Part 2: Veterinary (Avian) Pain Management & Signal Reception

By Jeannine Miesle MA, AAV

Part 1: History / Introduction

Part 2: Pain Perception and Signal Reception (Please scroll down)

Part 3: Pain Signal Transmission and Pain Pathways

Part 4: Types of Pain, Long-term effects, Referred Pain, and Pain Memory

Part 5: Pain, Stress, and the Body’s Physiological Response to Them

Part 6: Pain in the Avian Species

Part 7: Anesthesia and Analgesia, Chronic Pain

Part 8: Quality-of-Life Issues

Part 9: Pain Assessment in Birds / Quality of Life

Part 10: Hospice and Palliative Care for Pets, Strategy for Comprehensive Care, & Conclusion

Part II:

What happens when you’re cutting up vegetables and you suddenly feel a sharp pain? The cut you just gave yourself is very painful immediately, but it soon becomes a longer-lasting dull ache. Eventually both will go away, but how does the pain happen in the first place? What will make it less painful? What is pain, and how can it be managed?

Let’s look at what pain actually is. It’s not an easy concept to define or explain because it’s such a subjective sensation; what one person considers painful another barely feels.  It is defined as an “unpleasant sensory and emotional experience associated with tissue damage.” Your brain is telling you that a stimulus is causing damage, and you should do something about it.

Nociception, or pain perception, is the process by which a painful stimulus is relayed from the site of stimulation (injury) to the CNS (Center Nervous System). This process occurs in several steps:

First, Contact.  The body makes contact with a stimulus.  This stimulus can be

• Mechanical (pressure, punctures, and cuts)
• Chemical (burns)
• Thermal (heat, cold)
• Electrical (burns from lightning strikes, faulty wiring, shocks)

Second, Reception.

Third, Transmission.

The nerve sends the signal to the CNS. The relay of information usually involves several neurons (nerve cells) within the CNS.

Fourth, Pain Center Reception.

The brain receives the information from the nerves for further processing and action.

Nociception uses different neural pathways than normal perception, like light touch, pressure and temperature. When these do not cause pain, the first group of neurons to fire is normal somatic (sensory) receptors. When something causes pain, nociceptors go into action first.

Reference:

Freudenrich C. How Pain Works.

Signal Reception

Both normal sensory neurons and nociceptor neurons connect to peripheral sensory nerves. The stimulus travels along these nerves to the spinal cord. Normal nerve endings specialize in responding to ordinary levels of pressure, touch, and heat. These normal sensory nerve endings are myelinated; they are covered with a protein coat which insulates them and causes them to conduct normal stimuli quickly.

Nociceptors sense pain through nerve endings that are not myelinated; these are slower to conduct stimuli. Lightly myelinated nerve fibers conduct mechanical and thermal stimuli, while others contain C-fibers which conduct stimuli slowly and respond to many different types of stimuli.

The initial pain felt when the hand is cut is sudden and intense at the moment of injury. The signal for this pain is conducted rapidly by the myelinated nerve fibers. The less-intense pain produces a slower, prolonged, dull ache. This is conducted by the slower, non-myelinated C-fibers.  Anesthetists can block the neurons and separate the two types of pain. After that, analgesia can control the on-going pain.

Depending on the type of fiber, the neural impulse, or action potential, travels at speed ranging from two miles per hour in some unmyelinated fibers, to 200 or more miles per hour in myelinated fibers. Some actions must occur in a split second, such as withdrawing the hand from fire. In order for the nerve pathways to relay information that fast, there must be large, myelinated nerve fibers conducting them; on these, the impulses can travel as high as 0.6 miles per second. Some signals, such as those that originate in muscle position, travel at nearly 400 feet per second. This is how you know where each part of your body is as it moves. But some types of nociceptors travel more slowly. You will feel the pressure immediately if you hurt yourself because touch signals travel at 250 feet per second. But you won’t feel the pain for two or three more seconds because pain signals generally travel at only two feet per second.

References:

Freudenrich C. How Pain Works.

By Jeannine Miesle MA, AAV

Part 1: History / Introduction

Part 2: Pain Perception and Signal Reception

Part 3: Pain Signal Transmission and Pain Pathways (please scroll down)

Part 4: Types of Pain, Long-term effects, Referred Pain, and Pain Memory

Part 5: Pain, Stress, and the Body’s Physiological Response to Them

Part 6: Pain in the Avian Species

Part 7: Anesthesia and Analgesia, Chronic Pain

Part 8: Quality-of-Life Issues

Part 9: Pain Assessment in Birds / Quality of Life

Part 10: Hospice and Palliative Care for Pets, Strategy for Comprehensive Care, & Conclusion

Part 3: Pain Signal Transmission and Pain Pathways

Once pain signals are picked up by the nociceptors, they travel to the spinal cord’s dorsal root, located on the top of the vertebral area. There they connect (synapse) with other neurons which send the signal up the spinal column along the spinothalamic tract. This area is like a highway on which all sensory nerves travel to get to the brain. The messages are sent on afferent nerve fibers, meaning they travel to the spinal cord from the site of injury and then ascend to the brain. Efferent nerve fibers travel from the brain to the spinal cord and to the site of injury.

The messages first enter the brain stem (medulla) and synapse with neurons in the thalamus, the brain’s relay center. Some neurons there control physical behavior, such as pulling away from a painful stimulus. Nerves from the thalamus then relay the signal to the somatosensory center located in the cerebral cortex. From there, the neurons send signals to the motor cortex and down the spinal cord to the motor nerves. These tell you to move your hand away from the source of the pain. All this happens at one hundred meters (0.06 mile) per second; this seems instantaneous to the person injured.

The Brain’s Involvement

Scientists believe that the brain can influence pain perception. Researchers have observed that:

• Pain reduces in intensity over time.

• Patients who distract themselves consistently find that the pain doesn’t bother them as much.

• People who receive placebos for pain control often report that the pain ceases or diminishes.

This indicates that the pain-influencing neural pathways must exist in the efferent (descending) pathways. These efferent pathways originate in the somatosensory cortex, travel through the thalamus, then descend to the midbrain. There, they connect (synapse) with the ascending pathways in the medulla and spinal cord and actually inhibit the ascending nerve signals. The descending pathways prevent the painful nerve signals in the ascending pathways from continuing on to the brain! This produces pain relief (analgesia). In the process of this connection, natural, pain-relieving opiate neurotransmitters are stimulated. These are called endorphins, dynorphins and enkephalins. In a nutshell, the body has a way of diminishing the pain it experiences naturally, offering some relief. In more severe cases, it is insufficient, but in minor pain situations, this works very well.

So what happens in the body when it is in sudden, severe pain?  The heart rate and blood pressure increase, the body begins to sweat, and rapid breathing occurs. The more intense the pain, the more extensive are these reactions. They may be depressed somewhat by the brain centers in the cortex as the signals travel through descending pathways, but the ascending pain pathways, travelling through the spinal cord and medulla, can be set off by neuropathic pain—pain caused by damage to peripheral nerves, the spinal cord or the brain itself. This damage can limit the ability of the brain’s descending pathways to produce pain relief.

This may also cause psychogenic pain; pain which has no obvious physical cause.

Thoughts, emotions and nerve circuitry can affect both afferent and efferent pain pathways, resulting in physiological and psychological influences on pain perception. These are:

Age: Brain circuitry usually degenerates with age, so older people have lower pain thresholds and have more difficulty dealing with pain.

Gender: Women have a higher sensitivity to pain than men do. This could be due to sex-linked genetic traits and hormonal changes that alter pain perception. Psychosocial factors might influence the response to pain; men are expected not to show or report their pain, to be more stoic.

Fatigue: lack of sleep and stress both lead to a higher level of pain response.

Memory: Past experiences with pain can influence the neural responses; memory comes from the limbic system, which is related to the somosensory system.

Because animals have a somosensory and limbic system, they do feel emotions and pain. This is not a system such as the digestive system, but a collection of areas of the brain that control emotions. Many of these areas house the two systems collectively.

References:

Muir W III. The Ethics of Pain Management. In: Handbook of Veterinary Pain Management. Ed: James Gaynor, Wm Muir III. Mosby Inc, 2009.

Freudenrich C. How Pain Works.

Part 1: History / Introduction

Part 2: Pain Perception and Signal Reception

Part 3: Pain Signal Transmission and Pain Pathways

Part 4: Types of Pain, Long-term effects, Referred Pain, and Pain Memory

Part 5: Pain, Stress, and the Body’s Physiological Response to Them

Part 6: Pain in the Avian Species

Part 7: Anesthesia and Analgesia, Chronic Pain

Part 8: Quality-of-Life Issues

Part 9: Pain Assessment in Birds / Quality of Life  (Please scroll down)

Part 10: Hospice and Palliative Care for Pets, Strategy for Comprehensive Care, & Conclusion

Pain Assessment in Birds

Domain: Regularly … Sometimes … Rarely

Physical

• Is your bird’s energy level normal?
• Is your bird capable of completing normal, everyday tasks (playing, foraging, etc.)
• Is your bird eating normal amounts of food?
• Does your bird eat the normal variety of foods offered?
• Does your bird greet you with alertness and vocalization?
• Does your bird walk easily?
• Does your bird fly easily?
• Does your bird stumble due to poor vision?
• Does your bird fly into windows or furniture?
• Does your bird hear normally?
• Does your bird recognize his name and turn his head when you speak to him?
• Is your bird breathing normally, without tail-bobbing?
• Does your bird become out-of-breath after light exertion?
• Does your bird let you touch the painful area?
• Does your bird sleep comfortably on a perch? 
• Does your bird sleep on a platform or cage floor?
• Does your bird alternate its sleeping positions?
• Does your bird sit for long periods with its feathers fluffed and head under the wing?
• Does your bird react adversely to any medications?
• Is your bird presently on any medications?

Behavioral

• Is your bird behaving normally?
• Does your bird play with toys?
• Does your bird enjoy foraging opportunities? 
• Does your bird engage in normal self-grooming/preening behavior?
• Does your bird engage in social grooming of other birds?
• Does your bird preen normally after a bath?
• Does your bird appear chilled and remain still after a bath instead of preening normally?
• Is your bird easy to awaken?
• Is your bird ever unusually anxious or nervous?
• Does your bird cry out unexpectedly?
• Does your bird exhibit guarding behavior by changing body positions in order to protect a painful area?
• Does your bird withdraw to a corner or other solitary place and sit still?
• Does your bird engage in feather-destructive behavior?
• Does your bird engage in painful grooming behavior or self-mutilation at a specific site?
• Does your bird engage in painful grooming behavior or self-mutilation generally?
• Does your bird experience long periods of decreased activity?
• Is your bird increasingly aggressive toward other birds of the same species?
• Is your bird increasingly aggressive toward you?
• Is your bird tolerant of other pets in the house?
• Is your bird’s plumage in good condition?
• Are there any unusual lumps or growths on your bird?
• Are your bird’s eyes clear and bright?
• When you lift the eyelid, is it red?
• Are the nares clear and free of debris?
• Is there any discharge from the nares?
• Is your bird’s vent red, inflamed or swollen?
• Is there any tissue coming out of the vent?
• Does his preen gland appear normal?

Social

• Is your bird happy to see you when you get home?
• Does your bird interact normally with you?
• Does your bird interact normally with other people?
• Do you think your bird is happy?

What is your bird’s pain assessment?

The Bird Is In No Pain 0_____________________________________10  The Bird Is In Great Pain

Reference:

Paul-Murphy J. Pain Management for the Pet Bird. In: Handbook of Veterinary Pain Management, Ed. Gaynor J and Muir W III. Second Edition, Mosby Inc., 2009. p. 467

(Additional questions provided by J Miesle)

By Jeannine Miesle MA, AAV

Part 1: History / Introduction

Part 2: Pain Perception and Signal Reception

Part 3: Pain Signal Transmission and Pain Pathways

Part 4: Types of Pain, Long-term effects, Referred Pain, and Pain Memory  (Please scroll down)

Part 5: Pain, Stress, and the Body’s Physiological Response to Them

Part 6: Pain in the Avian Species

Part 7: Anesthesia and Analgesia, Chronic Pain

Part 8: Quality-of-Life Issues

Part 9: Pain Assessment in Birds / Quality of Life

Part 10: Hospice and Palliative Care for Pets, Strategy for Comprehensive Care, & Conclusion

Part 4: Types of Pain, Long-term Effects, Referred Pain, and Pain Memory

There are different types of pain, as classified by physicians and neuroscientists.

These are general categories under which fall many sub-categories:

Acute Pain: caused by an injury to the body. It warns of potential damage that requires action by the brain, and it can develop slowly or quickly. It can last for a few minutes to six months and goes away when the injury heals. Examples: accidents, falls, surgery, cuts.

Chronic pain: persists long after the trauma has healed, and in some cases, it occurs in the absence of any trauma or tissue damage. Chronic pain does not warn the body to respond, and it usually lasts longer than six months. Examples: Arthritis, fibromyalgia, headaches, back pain.

Cancer (malignant) pain: associated with malignant tumors. Tumors invade Healthy tissues and exert pressure on nerves or blood vessels, producing pain. Cancer pain can also be associated with invasive procedures or treatments. Some physicians classify cancer pain with chronic pain.

The taxonomy of pain is also categorized based on the source. The purpose of each category is to suggest possible causes for pain, its severity and most appropriate therapy.  

Some examples include:

• Disease: arthritis, pancreatitis, cancer

• Anatomy: bladder, pancreatic, back, orthopedic

• General location: superficial, visceral, deep

• Duration: transient, acute, chronic

• Intensity: mild, moderate, severe

• Response to manipulation: palpation, response to commands, algesiometers (an instrument for determining the skin’s response to a painful stimulus; this is done by applying steady pressure with the instrument’s probe until you get a response from the patient.)

The longer the pain persists, the more intense it becomes. There are actual changes in sensory processing in the spinal cord. Central sensitization refers to activity in the entire central nervous system (CNS). When pain lasts a very long time, either from injury or chronic disease, it creates “windup,” or constant neuroexcitability, which means that the noxious stimuli produce prolonged, long-term sensitivity in the dorsal horn of the spinal cord. This sensitization of the dorsal horn (where pain signals are modulated and then sent on to the brain), is thought to be responsible for increases in the hyperalgesia (over-sensitivity to pain), and allodynia (pain resulting from activity that doesn’t usually cause pain, usually touch.) This lowers the threshold of pain on a permanent basis. Continuous noxious stimuli lasting longer than several hours actually change the genetic code and are responsible for long-term structural changes (neuroplasticity) to the CNS.

Visceral (internal organ) pain is not easily or quickly identified due to the lower number of nociceptors in the viscera compared to peripheral nociceptors. This means that it is difficult to pinpoint the exact location of pain since each nociceptor covers a large area. Also, pain may not even be perceived in the beginning of an assault by a noxious stimulus; however, generalized inflammation and tissue damage activate “silent” nociceptors in the intestines and bladder and increase sensitivity to otherwise innocuous mechanical stimuli. In other words, constant pain will cause the individual to feel pain from stimuli which ordinarily are not painful. They lower the threshold of pain to the point that ordinary touch is painful.

Referred Pain

Referred pain is pain that is felt in uninjured tissue a distance away from the causative injury or lesion. The “dermatome” is the area innervated by a nerve ganglion. Everything in this dermatome (muscles, bones, joints, and tendons) will feel the pain from the injury. It develops slowly, usually triggered by a deep somatic and visceral even rather than a superficial injury, and it referred to regions derived from the same dermatome.

Pain Memory

Pain perception and memory correlate strongly with the peak intensity of pain, but interestingly, not with its duration. The more the site is traumatized, the more severe the pain. This suggests that injury produces neurochemical changes in the CNS that affect nociceptive behavior. This is true for humans and animals.

If painful stimuli establish a memory of pain, then therapies that prevent central sensitization and neuroplastic changes should be beneficial in restoring normal pain sensitivity. This is the reason medical doctors and veterinarians are providing preemptive analgesia—pain medication given before the traumatic event occurs (such as surgery). Doctors reason that preventing the pain from occurring will prevent or reduce the subsequent pain, and the need for medication for additional pain will lessen. Once the intensity of the pain is raised to a high level (hyperexcitability), larger doses of analgesia are required, and often the treatment is ineffective. Therefore, all pain should be treated as early as possible and preemptively when possible.

Reference:

Muir W. Physiology and pathophysiology of Pain. In: Handbook of Veterinary Pain Management. Ed: James Gaynor, Wm Muir III. Mosby Inc, 2009

By Jeannine Miesle MA, AAV

Part 1: History / Introduction

Part 2: Pain Perception and Signal Reception

Part 3: Pain Signal Transmission and Pain Pathways

Part 4: Types of Pain, Long-term effects, Referred Pain, and Pain Memory

Part 5: Pain, Stress, and the Body’s Physiological Response to Them

Part 6: Pain in the Avian Species

Part 7: Anesthesia and Analgesia, Chronic Pain

Part 8: Quality-of-Life Issues

Part 9: Pain Assessment in Birds / Quality of Life

Part 10: Hospice and Palliative Care for Pets, Strategy for Comprehensive Care, & Conclusion (Please scroll down)

Part 10: Hospice and Palliative Care for Pets

Many of the ideas in this final chapter will not pertain to birds, but some do. The reader will determine which is applicable to his situation.

Human beings grow old, and many require long-term care. A growing number of people are seeking the same type of care for their pets as is given to people in their end stage of life. The goal of palliative and hospice care in veterinary medicine is the same as it is in human medicine: to relieve suffering and enhance the quality of life for the pet and the family. Up until recently, euthanasia had been the only option in the treatment of advanced illness. Now, veterinarians realize they have another options in the treatment of the pet: palliative care and hospice. Due to the advances in veterinary medicine, pets are experiencing extended life and improved quality of life.

Hospice refers to a facility or program designed to provide a caring environment which provides for the physical and emotional needs of the terminally ill. Palliative care focuses on the relief of suffering in order to achieve the best quality of life for the patient, regardless of the disease outcome. The two services overlap as the patient approaches death.

Owners who are unprepared for the death of their pets tend to grieve longer and more intensely than those who are prepared due to the strength of the human-animal bond. Veterinarians who are aware of this will prepare their clients early in the disease process for the inevitable end of their pets’ lives. Failure to do so does their clients a disservice. However, it is important that care be taken not to discuss hospice and palliative care while the illness is still treatable. Only after diagnostic tests are performed, treatment is attempted and fails, and symptoms grow worse should the clinician discuss palliative care with the client. Accurate diagnostic and prognostic information will aid in the transition from curative treatment to supportive care, and then from palliative to hospice care. If the veterinarian is interested in provided such care for his patients, he will need to be a good listener, be patient, and be empathetic with the client. He will also need good time-management skills. Not every veterinarian is willing to provide such care; therefore, the client should ask about this possibility of it if this is what he wants for his pet in the end.

The following circumstances preclude the choice of administering palliative or hospice care:

1. A decision not to pursue curative treatments
2. Diagnosis of a terminal illness
3. Diagnosis of a chronic illness
4. Symptoms of a chronic illness that are interfering with the routine of the pet
5. Disease process in which curative treatment was possible but failed
6. Difficulties that require long-term intensive care
7. Illnesses that are progressive
8. Trauma or diseases that have health complications associated with them

Clients should be given the following information:

• Physical examination findings
• List of all complications
• Assessment of quality of life

Hospice and Palliative Care Protocols

The “Pet Hospice and Education Center” in Sunbury, Ohio has developed a Five-Step Strategy for Comprehensive Care.” It is important to have such a protocol to make sure all details of care are provided. Because every pet’s condition and family relationship is different, a protocol assists the veterinarian and the family when they share information and discuss the pet’s care.

Five-Step Strategy for Comprehensive Care

Step 1:

Evaluation of the pet owner’s needs, beliefs, and goals for the pet. For the program to be successful, the care given by the veterinarian must be consistent with the beliefs of the pet owner. The program needs to be individualized for each client and each pet; therefore, the foundation upon which the care is built rests upon the communication between client and practitioner. The client may not wish euthanasia, or may not want the pet to be hospitalized, so alternatives need to be provided. It is not unusual for pet owners to abandon their original palliative or hospice care plan and pursue additional treatment in the hope of a cure.

It is also not unusual for the client to change his mind about the course of treatment or the option of euthanasia. Should the owner choose to have the dying pet given extraordinary care, such as esophageal feeding tubes, he should be advised of the risks of such procedures. Most of the time, these efforts are futile and merely serve to prolong the pet’s discomfort. Does the owner wish to track the disease process with testing? Where will the pet spend its time, in the hospital or at home? Are there alternative therapies for this illness? Final event details should be discussed with the owner. Does the owner want the pet to die at home or at the office? What will be done with the body? There are several options for handling the remains, and the client should ask about this ahead of time.

Step 2: Education about the disease process

The veterinarian should be familiar with the disease process and share this information with the owner. The owner will need to be informed about life expectancy, symptoms of the disease, and common side effects. This will allow the owner to make better choices on his pet’s behalf. An accurate diagnosis is vital before initiating a hospice plan. He should also discuss the complications of any treatments provided. A discussion about the owner’s financial concerns is also in order. The owner should not be made to feel guilty if he cannot afford the long-term treatment or hospice care. The option of euthanasia should always be offered.

Step 3: Development of a personalized plan for the pet and pet owner.

This plan is based upon the previous discussion about the family’s beliefs and desires for the pet. The plan should take into account the management of the symptoms of the disease, the willingness of the pet to take medications, the ability of the owner to dispense the medications, and the pet’s reactions to the stress of hospital visits. As the pet’s condition deteriorates, there will be a transition into hospice care. For this to happen, the family must acknowledge that the pet is actually dying and showing no improvement or worsening, even with medical help.

The veterinarian my come across dilemmas regarding the treatment choices because of the side effects of some of the medications. Such interventions may have negative consequences. For example, a medication which will alleviate pain my also risk death because of respiratory depression, but the importance of controlling pain overrides the other concerns. Nutrition should be addressed. If the pet is not able to eat on its own, it might require feeding tubes. These options should be discussed with the pet owner. Another challenge the veterinarian faces is that of treatment of wounds. There is the pain of the wound itself and the pain associated with the caring for the wound. In these cases, pain medication should be given one to two hours before the wound treatment.

Many of the medications given during the hospice and palliative care experience produce unwanted side effects; in addition, many will react adversely with each other. The client needs to be aware of the possible side effects of these drugs.

Medication Side-effect List for Clients:

• A rapid decline in condition, especially after starting a new medication

• Restlessness, excitability, (salivation, licking of the lips for mammals), or trembling after administration of a medication

• Lack of appetite or vomiting after being given medication

• Change in bowel movement consistency, frequency, or color

• Development of skin irritation or itching

• Development of depression or disorientation of administration of a medication

Step 4: Application of Palliative or Hospice Care Techniques

The pet owner should be able to carry out any directives given for the care of the dying pet. A support team member for the owner should be available to contact when problems develop in carrying out the techniques.

• The pet owner should be taught how to carry out the palliative techniques to provide comfort to the animal.

• Techniques should be demonstrated by a professional then performed by the client under staff observation.

• Compounded medications should be provided

• A list of medication side effects should be given to the client.

Step 5: Emotional Support during the Care Process and After Death

End of life is defined as the period when death is imminent. Before and during this time, the pet owner needs to be able to interpret the pet’s quality of life. Veterinarians should have a system to evaluate the pet’s physical comfort as well as the emotional well-being of the pet owner in the decision process. The clinician needs to describe the dying process, whether by natural causes or by euthanasia, with the pet owner. (When euthanasia is chosen, it is a two-step process: First, a tranquilizer is given to put the pet to sleep, then the drug is given to stop the heart. The veterinarian should always use the stethoscope to make sure the heart has stopped completely before declaring the animal dead.)

If possible, an emotional support system for the owner should be implemented before the end of the pet’s life. It might mean calling on the services of medical advisors, clergy, psychologists, social workers, or volunteers who have training in human palliate and hospice care. This team approach ensures that every need of the client is met. There should also be a list of pet-loss support groups to which the pet owner can refer if need be. For many people, depression and grief can impact their lives for a long time.

Conclusion:

Any veterinarian should be able to use this philosophy of palliative and hospice care. The role of the veterinarian and staff in the palliative and hospice care of the dying patient is extremely important. The client is in a vulnerable state and relies heavily on the clinician’s information and advice when making decisions about his pet’s care. A solid, relationship-centered plan will relieve the suffering of the pet and enhance its quality of life. It will also provide the needed emotional support system for the owner at this difficult time. Long after the death of the pet, the owner will remember the many kindnesses of the veterinary professional and his staff.

Reference:

Shearer T. Hospice and Palliative Care. In: Handbook of Veterinary Pain Management, Ed. Gaynor J and Muir W III. Mosby, Inc. 2009.

By Jeannine Miesle MA, AAV

Part 1: History / Introduction

Part 2: Pain Perception and Signal Reception

Part 3: Pain Signal Transmission and Pain Pathways

Part 4: Types of Pain, Long-term effects, Referred Pain, and Pain Memory

Part 5: Pain, Stress, and the Body’s Physiological Response to Them

Part 6: Pain in the Avian Species

Part 7: Anesthesia and Analgesia, Chronic Pain (Please scroll down)

Part 8: Quality-of-Life Issues

Part 9: Pain Assessment in Birds / Quality of Life

Part 10: Hospice and Palliative Care for Pets, Strategy for Comprehensive Care, & Conclusion

Part 7: Anesthesia and Analgesia, Chronic Pain

Regional Anesthesia and Analgesia

Local anesthetics such as lidocaine and bupivacaine block the sodium channels in the nerve axon. These channels carry the nerve impulses in the nerve fibers to the spinal cord and brain. They interfere with the conduction of the action potentials, or nerve sensations, along the nerve. The events from the first recognition of pain, the transmission to the spinal cord, the modulation and transmission to the brain, ending with the movement away from the painful stimulus happen almost instantaneously. The neuron path travels at about 700 mph.

Veterinarians and their physician and dental counterparts use a technique for local anesthesia called a “splash block.” Dentists inject a tiny amount (called a bleb) of Novocain in first, and when it has numbed the area a little, they inject another and another until the entire area is numb. Veterinarians make several subcutaneous injections; the space in the skin is very thin, so they follow the incision line with little blebs of anesthesia until the entire line is blocked.

Because birds are more sensitive to the effects of the drugs, the practitioner must be very careful about dosage, and will often use a lower dose of anesthesia than he would for mammals. Also, systemic uptake of the drug is more rapid with birds, and metabolism may be prolonged, increasing the possibility of toxic reactions. Side effects may include fine tremors, ataxia, sleepiness, recumbency (lying down), seizures, stupor (unresponsiveness), cardiovascular effects, and death.

When general anesthesia is needed, the two most commonly used gases are isoflurane and sevoflurane. These two gases are very safe; they are not volatile as previous gases had been, and patients awaken without the confusion that had occurred with previous gases. The bird is given an opioid once he is anesthetized to diminish the painful stimuli occurring during and after the surgery. Post-operative opioids are administered every 2-3 hours intramuscularly to maintain the analgesic effect.

Drugs may be given orally or parenterally (in a way other than by mouth or into the digestive tract.) Injections may be given:

1. Intraosseously (into the bone)

2. Subcutaneously (into the skin)

3. Intramuscularly (into the muscle)

4. Intrasternally (into the sternum) or

5. ly (into the vein)

There are two different types of analgesic pain killers: opiods and Non-Steroidal Anti-Inflammatories (NSAIDS). Opiods reversibly bind to specific receptors in the central and peripheral nervous systems. Clinical effects depend on the preparation of the drug, the dose, the route of administration, and the species being given the drug. NSAIDS work to reduce the cyclooxygenase (COX) enzymes in the body. Cyclooxygenase is an enzyme produced by the body to respond to tissue injury. COX-2 inhibitors block prostaglandins which cause pain and inflammation. Since COX-1 enzymes also protect the stomach and promote blood clotting; it is advisable not to inhibit these enzymes.

COX-2 inhibitors also decrease the sensitivity of the nerve endings. NSAIDS are used mostly to relieve arthritis pain and visceral, muscular pain, and to decrease inflammation associated with surgery. When injury occurs, the COX enzymes initiate a cascade of reactions which release substances that cause inflammation and sensitization of the nerve endings. NSAIDS inhibit these COX-2 enzymes, thereby reducing inflammation at the site of the injury.

Chronic Pain

Chronic, painful conditions, such as joint disease and neoplasia, are progressive and degenerative. It’s often difficult to assess and treat these conditions in birds since the response to analgesia is based on the evaluation of behavior of each bird.

NSAIDS are the first course of therapy for chronic disorders. They have no sedative effects and last longer than opiods. Carprofen, meloxicam, and celecoxib are frequently administer as they have few side effects and may be administered orally in small birds. Dosages begin low and increase over time as necessary. Monitoring renal and hepatic function every few months and CBC’s are recommended. Stronger NSAIDS may be needed for degenerative joint disease and cancer; however, they come with the risk of renal toxicity and gastric ulceration when given in high dosages. If the pain is not controlled with NSAIDDS, opioid use may be indicated.

Many medications and modalities used in mammals, especially dogs and cats, have not been tested in birds. Cancer treatment, although now commonplace in mammals, is generally not used in birds because of the dangers of side effects and lack of sufficient evidence of their success. Birds are too fragile for such aggressive therapy.

Reference: Paul-Murphy J. Pain management for the Pet Bird. In: Handbook of Veterinary Pain Management. Ed. James Gaynor, William Muir III. Mosby, Inc 2009

By Jeannine Miesle MA, AAV

Part 1: History / Introduction

Part 2: Pain Perception and Signal Reception

Part 3: Pain Signal Transmission and Pain Pathways

Part 4: Types of Pain, Long-term effects, Referred Pain, and Pain Memory

Part 5: Pain, Stress, and the Body’s Physiological Response to Them  (Please scroll down)

Part 6: Pain in the Avian Species

Part 7: Anesthesia and Analgesia, Chronic Pain

Part 8: Quality-of-Life Issues

Part 9: Pain Assessment in Birds / Quality of Life

Part 10: Hospice and Palliative Care for Pets, Strategy for Comprehensive Care, & Conclusion

Part 5: Pain, Stress, and the Body’s Physiological Response to Them

An animal’s well-being should include

“The Five Freedoms”

Freedom from thirst, hunger, and malnutrition

• Access to fresh water and a healthful diet

Freedom from discomfort

• Suitable environment, shelter, and a resting place

Freedom from pain, injury, and disease

• Prevention of cruelty and illness by care and rapid treatment

Freedom to express normal behavior

• Provision of space, facilities, and company of the animal’s own kind

Freedom from fear and distress

• Assurance of conditions that avoid stress and mental suffering

Wm. W Muir III

Stress is a biological response that an animal exhibits when it perceives a threat. Its internal state of well—being (homeostasis) is jeopardized. In the past, most vets only concerned themselves with the body’s response to injury or surgical trauma, but today they realize that there are many factors which can put homeostasis at risk.

The Central Nervous System (CNS) can modify the response of the body to the various stressors, such as pain, surgery, restraint, and confinement. Birds can experience trauma from auditory and visual stimuli identical to somatosensory input from damaged tissue. Stress modifies the animal’s memory, thus serving as a protective role in diverting the body’s resources to cope with the stressor. If the body cannot respond effectively to stress, it cannot maintain homeostasis, and the result is dysfunction, disease, and suffering. This “sickness syndrome” hastens death.

It is uncertain whether animals perceive pain and suffering in the same way humans do because they live in the present and cannot understand death or future suffering. Its interaction with its environment and external events determines its well-being. This interaction incorporates feeling, perception and awareness, so if he perceives an event as threatening, the response will be the same whether it is threatening or not; therefore, it is ethical and humane to minimize stress because of the adverse reaction to it all animals face.

Pain serves a protective function by warning the animal of real or impending tissue damage. Acute and chronic pain produce stress, and when severe, increase neuroendocrine activity and profound behavior changes. Environmental factors can produce anxiety and feather that sensitize and amplify the stress response to painful stimulus. The severity and duration of pain determine the consequences of the animal’s pain in terms of stress and suffering.

Stress alters the release of the hormones in the body. Some of the hormones that are affected are cortisol, epinephrine, glucagon (insulin for mammals), the growth and thyroid hormones, and vasopressin, which aids the body in retaining the necessary amount of water.

The metabolism is also affected by stress. Unbalanced carbohydrates can lead to hyperglycemia, poor wound-healing, infections, and morbidity. Fat and protein metabolism are disturbed, causing the body to be unable to metabolize these properly.

The Immune System

Although most people think the immune system’s primary purpose is to identify and destroy foreign substances, it also functions as a sense organ that communicates injury-related information to the brain. It can be activated or depressed by stress; thus, pain, whether accidental or intentional (e.g. surgery), modulates (changes) the immune response. The key elements that determine how the immune system responds to pain are intensity and duration. Chronic pain suppresses the immune system’s responses, and mild-to-moderate pain from tissue trauma activates the immune system’s messengers.

The Acute-Phase Response of the immune system is triggered by severe stress from any cause. This response releases proteins from the liver, which acts in repairing tissue. Excessive production of these proteins can contribute to Systemic Inflammatory Response Syndrome (SIRS).

Morphological Changes

Morphological changes brought about by chronic stress or pain are typical of long-term aversive stimuli and include failure to thrive, feather loss, poor feather condition, weight loss, and acceleration of aging.

Reference:

Muir W III. Pain and Stress. In: Handbook of Veterinary Pain Management. Ed: James Gaynor, Wm Muir III. Mosby Inc, 2009

By Jeannine Miesle MA, AAV

Part 1: History / Introduction

Part 2: Pain Perception and Signal Reception

Part 3: Pain Signal Transmission and Pain Pathways (please scroll down)

Part 4: Types of Pain, Long-term effects, Referred Pain, and Pain Memory

Part 5: Pain, Stress, and the Body’s Physiological Response to Them

Part 6: Pain in the Avian Species

Part 7: Anesthesia and Analgesia, Chronic Pain

Part 8: Quality-of-Life Issues

Part 9: Pain Assessment in Birds / Quality of Life

Part 10: Hospice and Palliative Care for Pets, Strategy for Comprehensive Care, & Conclusion

Part 3: Pain Signal Transmission and Pain Pathways

Once pain signals are picked up by the nociceptors, they travel to the spinal cord’s dorsal root, located on the top of the vertebral area. There they connect (synapse) with other neurons which send the signal up the spinal column along the spinothalamic tract. This area is like a highway on which all sensory nerves travel to get to the brain. The messages are sent on afferent nerve fibers, meaning they travel to the spinal cord from the site of injury and then ascend to the brain. Efferent nerve fibers travel from the brain to the spinal cord and to the site of injury.

The messages first enter the brain stem (medulla) and synapse with neurons in the thalamus, the brain’s relay center. Some neurons there control physical behavior, such as pulling away from a painful stimulus. Nerves from the thalamus then relay the signal to the somatosensory center located in the cerebral cortex. From there, the neurons send signals to the motor cortex and down the spinal cord to the motor nerves. These tell you to move your hand away from the source of the pain. All this happens at one hundred meters (0.06 mile) per second; this seems instantaneous to the person injured.

The Brain’s Involvement

Scientists believe that the brain can influence pain perception. Researchers have observed that:

• Pain reduces in intensity over time.

• Patients who distract themselves consistently find that the pain doesn’t bother them as much.

• People who receive placebos for pain control often report that the pain ceases or diminishes.

This indicates that the pain-influencing neural pathways must exist in the efferent (descending) pathways. These efferent pathways originate in the somatosensory cortex, travel through the thalamus, then descend to the midbrain. There, they connect (synapse) with the ascending pathways in the medulla and spinal cord and actually inhibit the ascending nerve signals. The descending pathways prevent the painful nerve signals in the ascending pathways from continuing on to the brain! This produces pain relief (analgesia). In the process of this connection, natural, pain-relieving opiate neurotransmitters are stimulated. These are called endorphins, dynorphins and enkephalins. In a nutshell, the body has a way of diminishing the pain it experiences naturally, offering some relief. In more severe cases, it is insufficient, but in minor pain situations, this works very well.

So what happens in the body when it is in sudden, severe pain?  The heart rate and blood pressure increase, the body begins to sweat, and rapid breathing occurs. The more intense the pain, the more extensive are these reactions. They may be depressed somewhat by the brain centers in the cortex as the signals travel through descending pathways, but the ascending pain pathways, travelling through the spinal cord and medulla, can be set off by neuropathic pain—pain caused by damage to peripheral nerves, the spinal cord or the brain itself. This damage can limit the ability of the brain’s descending pathways to produce pain relief.

This may also cause psychogenic pain; pain which has no obvious physical cause.

Thoughts, emotions and nerve circuitry can affect both afferent and efferent pain pathways, resulting in physiological and psychological influences on pain perception. These are:

Age: Brain circuitry usually degenerates with age, so older people have lower pain thresholds and have more difficulty dealing with pain.

Gender: Women have a higher sensitivity to pain than men do. This could be due to sex-linked genetic traits and hormonal changes that alter pain perception. Psychosocial factors might influence the response to pain; men are expected not to show or report their pain, to be more stoic.

Fatigue: lack of sleep and stress both lead to a higher level of pain response.

Memory: Past experiences with pain can influence the neural responses; memory comes from the limbic system, which is related to the somosensory system.

Because animals have a somosensory and limbic system, they do feel emotions and pain. This is not a system such as the digestive system, but a collection of areas of the brain that control emotions. Many of these areas house the two systems collectively.

References:

Muir W III. The Ethics of Pain Management. In: Handbook of Veterinary Pain Management. Ed: James Gaynor, Wm Muir III. Mosby Inc, 2009.

Freudenrich C. How Pain Works.

Part 1: History / Introduction

Part 2: Pain Perception and Signal Reception

Part 3: Pain Signal Transmission and Pain Pathways

Part 4: Types of Pain, Long-term effects, Referred Pain, and Pain Memory

Part 5: Pain, Stress, and the Body’s Physiological Response to Them

Part 6: Pain in the Avian Species

Part 7: Anesthesia and Analgesia, Chronic Pain

Part 8: Quality-of-Life Issues

Part 9: Pain Assessment in Birds / Quality of Life  (Please scroll down)

Part 10: Hospice and Palliative Care for Pets, Strategy for Comprehensive Care, & Conclusion

Pain Assessment in Birds

Domain: Regularly … Sometimes … Rarely

Physical

• Is your bird’s energy level normal?
• Is your bird capable of completing normal, everyday tasks (playing, foraging, etc.)
• Is your bird eating normal amounts of food?
• Does your bird eat the normal variety of foods offered?
• Does your bird greet you with alertness and vocalization?
• Does your bird walk easily?
• Does your bird fly easily?
• Does your bird stumble due to poor vision?
• Does your bird fly into windows or furniture?
• Does your bird hear normally?
• Does your bird recognize his name and turn his head when you speak to him?
• Is your bird breathing normally, without tail-bobbing?
• Does your bird become out-of-breath after light exertion?
• Does your bird let you touch the painful area?
• Does your bird sleep comfortably on a perch? 
• Does your bird sleep on a platform or cage floor?
• Does your bird alternate its sleeping positions?
• Does your bird sit for long periods with its feathers fluffed and head under the wing?
• Does your bird react adversely to any medications?
• Is your bird presently on any medications?

Behavioral

• Is your bird behaving normally?
• Does your bird play with toys?
• Does your bird enjoy foraging opportunities? 
• Does your bird engage in normal self-grooming/preening behavior?
• Does your bird engage in social grooming of other birds?
• Does your bird preen normally after a bath?
• Does your bird appear chilled and remain still after a bath instead of preening normally?
• Is your bird easy to awaken?
• Is your bird ever unusually anxious or nervous?
• Does your bird cry out unexpectedly?
• Does your bird exhibit guarding behavior by changing body positions in order to protect a painful area?
• Does your bird withdraw to a corner or other solitary place and sit still?
• Does your bird engage in feather-destructive behavior?
• Does your bird engage in painful grooming behavior or self-mutilation at a specific site?
• Does your bird engage in painful grooming behavior or self-mutilation generally?
• Does your bird experience long periods of decreased activity?
• Is your bird increasingly aggressive toward other birds of the same species?
• Is your bird increasingly aggressive toward you?
• Is your bird tolerant of other pets in the house?
• Is your bird’s plumage in good condition?
• Are there any unusual lumps or growths on your bird?
• Are your bird’s eyes clear and bright?
• When you lift the eyelid, is it red?
• Are the nares clear and free of debris?
• Is there any discharge from the nares?
• Is your bird’s vent red, inflamed or swollen?
• Is there any tissue coming out of the vent?
• Does his preen gland appear normal?

Social

• Is your bird happy to see you when you get home?
• Does your bird interact normally with you?
• Does your bird interact normally with other people?
• Do you think your bird is happy?

What is your bird’s pain assessment?

The Bird Is In No Pain 0_____________________________________10  The Bird Is In Great Pain

Reference:

Paul-Murphy J. Pain Management for the Pet Bird. In: Handbook of Veterinary Pain Management, Ed. Gaynor J and Muir W III. Second Edition, Mosby Inc., 2009. p. 467

(Additional questions provided by J Miesle)

By Jeannine Miesle MA, AAV

Part 1: History / Introduction

Part 2: Pain Perception and Signal Reception

Part 3: Pain Signal Transmission and Pain Pathways

Part 4: Types of Pain, Long-term effects, Referred Pain, and Pain Memory  (Please scroll down)

Part 5: Pain, Stress, and the Body’s Physiological Response to Them

Part 6: Pain in the Avian Species

Part 7: Anesthesia and Analgesia, Chronic Pain

Part 8: Quality-of-Life Issues

Part 9: Pain Assessment in Birds / Quality of Life

Part 10: Hospice and Palliative Care for Pets, Strategy for Comprehensive Care, & Conclusion

Part 4: Types of Pain, Long-term Effects, Referred Pain, and Pain Memory

There are different types of pain, as classified by physicians and neuroscientists.

These are general categories under which fall many sub-categories:

Acute Pain: caused by an injury to the body. It warns of potential damage that requires action by the brain, and it can develop slowly or quickly. It can last for a few minutes to six months and goes away when the injury heals. Examples: accidents, falls, surgery, cuts.

Chronic pain: persists long after the trauma has healed, and in some cases, it occurs in the absence of any trauma or tissue damage. Chronic pain does not warn the body to respond, and it usually lasts longer than six months. Examples: Arthritis, fibromyalgia, headaches, back pain.

Cancer (malignant) pain: associated with malignant tumors. Tumors invade Healthy tissues and exert pressure on nerves or blood vessels, producing pain. Cancer pain can also be associated with invasive procedures or treatments. Some physicians classify cancer pain with chronic pain.

The taxonomy of pain is also categorized based on the source. The purpose of each category is to suggest possible causes for pain, its severity and most appropriate therapy.  

Some examples include:

• Disease: arthritis, pancreatitis, cancer

• Anatomy: bladder, pancreatic, back, orthopedic

• General location: superficial, visceral, deep

• Duration: transient, acute, chronic

• Intensity: mild, moderate, severe

• Response to manipulation: palpation, response to commands, algesiometers (an instrument for determining the skin’s response to a painful stimulus; this is done by applying steady pressure with the instrument’s probe until you get a response from the patient.)

The longer the pain persists, the more intense it becomes. There are actual changes in sensory processing in the spinal cord. Central sensitization refers to activity in the entire central nervous system (CNS). When pain lasts a very long time, either from injury or chronic disease, it creates “windup,” or constant neuroexcitability, which means that the noxious stimuli produce prolonged, long-term sensitivity in the dorsal horn of the spinal cord. This sensitization of the dorsal horn (where pain signals are modulated and then sent on to the brain), is thought to be responsible for increases in the hyperalgesia (over-sensitivity to pain), and allodynia (pain resulting from activity that doesn’t usually cause pain, usually touch.) This lowers the threshold of pain on a permanent basis. Continuous noxious stimuli lasting longer than several hours actually change the genetic code and are responsible for long-term structural changes (neuroplasticity) to the CNS.

Visceral (internal organ) pain is not easily or quickly identified due to the lower number of nociceptors in the viscera compared to peripheral nociceptors. This means that it is difficult to pinpoint the exact location of pain since each nociceptor covers a large area. Also, pain may not even be perceived in the beginning of an assault by a noxious stimulus; however, generalized inflammation and tissue damage activate “silent” nociceptors in the intestines and bladder and increase sensitivity to otherwise innocuous mechanical stimuli. In other words, constant pain will cause the individual to feel pain from stimuli which ordinarily are not painful. They lower the threshold of pain to the point that ordinary touch is painful.

Referred Pain

Referred pain is pain that is felt in uninjured tissue a distance away from the causative injury or lesion. The “dermatome” is the area innervated by a nerve ganglion. Everything in this dermatome (muscles, bones, joints, and tendons) will feel the pain from the injury. It develops slowly, usually triggered by a deep somatic and visceral even rather than a superficial injury, and it referred to regions derived from the same dermatome.

Pain Memory

Pain perception and memory correlate strongly with the peak intensity of pain, but interestingly, not with its duration. The more the site is traumatized, the more severe the pain. This suggests that injury produces neurochemical changes in the CNS that affect nociceptive behavior. This is true for humans and animals.

If painful stimuli establish a memory of pain, then therapies that prevent central sensitization and neuroplastic changes should be beneficial in restoring normal pain sensitivity. This is the reason medical doctors and veterinarians are providing preemptive analgesia—pain medication given before the traumatic event occurs (such as surgery). Doctors reason that preventing the pain from occurring will prevent or reduce the subsequent pain, and the need for medication for additional pain will lessen. Once the intensity of the pain is raised to a high level (hyperexcitability), larger doses of analgesia are required, and often the treatment is ineffective. Therefore, all pain should be treated as early as possible and preemptively when possible.

Reference:

Muir W. Physiology and pathophysiology of Pain. In: Handbook of Veterinary Pain Management. Ed: James Gaynor, Wm Muir III. Mosby Inc, 2009

By Jeannine Miesle MA, AAV

Part 1: History / Introduction

Part 2: Pain Perception and Signal Reception

Part 3: Pain Signal Transmission and Pain Pathways

Part 4: Types of Pain, Long-term effects, Referred Pain, and Pain Memory

Part 5: Pain, Stress, and the Body’s Physiological Response to Them

Part 6: Pain in the Avian Species

Part 7: Anesthesia and Analgesia, Chronic Pain

Part 8: Quality-of-Life Issues

Part 9: Pain Assessment in Birds / Quality of Life

Part 10: Hospice and Palliative Care for Pets, Strategy for Comprehensive Care, & Conclusion (Please scroll down)

Part 10: Hospice and Palliative Care for Pets

Many of the ideas in this final chapter will not pertain to birds, but some do. The reader will determine which is applicable to his situation.

Human beings grow old, and many require long-term care. A growing number of people are seeking the same type of care for their pets as is given to people in their end stage of life. The goal of palliative and hospice care in veterinary medicine is the same as it is in human medicine: to relieve suffering and enhance the quality of life for the pet and the family. Up until recently, euthanasia had been the only option in the treatment of advanced illness. Now, veterinarians realize they have another options in the treatment of the pet: palliative care and hospice. Due to the advances in veterinary medicine, pets are experiencing extended life and improved quality of life.

Hospice refers to a facility or program designed to provide a caring environment which provides for the physical and emotional needs of the terminally ill. Palliative care focuses on the relief of suffering in order to achieve the best quality of life for the patient, regardless of the disease outcome. The two services overlap as the patient approaches death.

Owners who are unprepared for the death of their pets tend to grieve longer and more intensely than those who are prepared due to the strength of the human-animal bond. Veterinarians who are aware of this will prepare their clients early in the disease process for the inevitable end of their pets’ lives. Failure to do so does their clients a disservice. However, it is important that care be taken not to discuss hospice and palliative care while the illness is still treatable. Only after diagnostic tests are performed, treatment is attempted and fails, and symptoms grow worse should the clinician discuss palliative care with the client. Accurate diagnostic and prognostic information will aid in the transition from curative treatment to supportive care, and then from palliative to hospice care. If the veterinarian is interested in provided such care for his patients, he will need to be a good listener, be patient, and be empathetic with the client. He will also need good time-management skills. Not every veterinarian is willing to provide such care; therefore, the client should ask about this possibility of it if this is what he wants for his pet in the end.

The following circumstances preclude the choice of administering palliative or hospice care:

1. A decision not to pursue curative treatments
2. Diagnosis of a terminal illness
3. Diagnosis of a chronic illness
4. Symptoms of a chronic illness that are interfering with the routine of the pet
5. Disease process in which curative treatment was possible but failed
6. Difficulties that require long-term intensive care
7. Illnesses that are progressive
8. Trauma or diseases that have health complications associated with them

Clients should be given the following information:

• Physical examination findings
• List of all complications
• Assessment of quality of life

Hospice and Palliative Care Protocols

The “Pet Hospice and Education Center” in Sunbury, Ohio has developed a Five-Step Strategy for Comprehensive Care.” It is important to have such a protocol to make sure all details of care are provided. Because every pet’s condition and family relationship is different, a protocol assists the veterinarian and the family when they share information and discuss the pet’s care.

Five-Step Strategy for Comprehensive Care

Step 1:

Evaluation of the pet owner’s needs, beliefs, and goals for the pet. For the program to be successful, the care given by the veterinarian must be consistent with the beliefs of the pet owner. The program needs to be individualized for each client and each pet; therefore, the foundation upon which the care is built rests upon the communication between client and practitioner. The client may not wish euthanasia, or may not want the pet to be hospitalized, so alternatives need to be provided. It is not unusual for pet owners to abandon their original palliative or hospice care plan and pursue additional treatment in the hope of a cure.

It is also not unusual for the client to change his mind about the course of treatment or the option of euthanasia. Should the owner choose to have the dying pet given extraordinary care, such as esophageal feeding tubes, he should be advised of the risks of such procedures. Most of the time, these efforts are futile and merely serve to prolong the pet’s discomfort. Does the owner wish to track the disease process with testing? Where will the pet spend its time, in the hospital or at home? Are there alternative therapies for this illness? Final event details should be discussed with the owner. Does the owner want the pet to die at home or at the office? What will be done with the body? There are several options for handling the remains, and the client should ask about this ahead of time.

Step 2: Education about the disease process

The veterinarian should be familiar with the disease process and share this information with the owner. The owner will need to be informed about life expectancy, symptoms of the disease, and common side effects. This will allow the owner to make better choices on his pet’s behalf. An accurate diagnosis is vital before initiating a hospice plan. He should also discuss the complications of any treatments provided. A discussion about the owner’s financial concerns is also in order. The owner should not be made to feel guilty if he cannot afford the long-term treatment or hospice care. The option of euthanasia should always be offered.

Step 3: Development of a personalized plan for the pet and pet owner.

This plan is based upon the previous discussion about the family’s beliefs and desires for the pet. The plan should take into account the management of the symptoms of the disease, the willingness of the pet to take medications, the ability of the owner to dispense the medications, and the pet’s reactions to the stress of hospital visits. As the pet’s condition deteriorates, there will be a transition into hospice care. For this to happen, the family must acknowledge that the pet is actually dying and showing no improvement or worsening, even with medical help.

The veterinarian my come across dilemmas regarding the treatment choices because of the side effects of some of the medications. Such interventions may have negative consequences. For example, a medication which will alleviate pain my also risk death because of respiratory depression, but the importance of controlling pain overrides the other concerns. Nutrition should be addressed. If the pet is not able to eat on its own, it might require feeding tubes. These options should be discussed with the pet owner. Another challenge the veterinarian faces is that of treatment of wounds. There is the pain of the wound itself and the pain associated with the caring for the wound. In these cases, pain medication should be given one to two hours before the wound treatment.

Many of the medications given during the hospice and palliative care experience produce unwanted side effects; in addition, many will react adversely with each other. The client needs to be aware of the possible side effects of these drugs.

Medication Side-effect List for Clients:

• A rapid decline in condition, especially after starting a new medication

• Restlessness, excitability, (salivation, licking of the lips for mammals), or trembling after administration of a medication

• Lack of appetite or vomiting after being given medication

• Change in bowel movement consistency, frequency, or color

• Development of skin irritation or itching

• Development of depression or disorientation of administration of a medication

Step 4: Application of Palliative or Hospice Care Techniques

The pet owner should be able to carry out any directives given for the care of the dying pet. A support team member for the owner should be available to contact when problems develop in carrying out the techniques.

• The pet owner should be taught how to carry out the palliative techniques to provide comfort to the animal.

• Techniques should be demonstrated by a professional then performed by the client under staff observation.

• Compounded medications should be provided

• A list of medication side effects should be given to the client.

Step 5: Emotional Support during the Care Process and After Death

End of life is defined as the period when death is imminent. Before and during this time, the pet owner needs to be able to interpret the pet’s quality of life. Veterinarians should have a system to evaluate the pet’s physical comfort as well as the emotional well-being of the pet owner in the decision process. The clinician needs to describe the dying process, whether by natural causes or by euthanasia, with the pet owner. (When euthanasia is chosen, it is a two-step process: First, a tranquilizer is given to put the pet to sleep, then the drug is given to stop the heart. The veterinarian should always use the stethoscope to make sure the heart has stopped completely before declaring the animal dead.)

If possible, an emotional support system for the owner should be implemented before the end of the pet’s life. It might mean calling on the services of medical advisors, clergy, psychologists, social workers, or volunteers who have training in human palliate and hospice care. This team approach ensures that every need of the client is met. There should also be a list of pet-loss support groups to which the pet owner can refer if need be. For many people, depression and grief can impact their lives for a long time.

Conclusion:

Any veterinarian should be able to use this philosophy of palliative and hospice care. The role of the veterinarian and staff in the palliative and hospice care of the dying patient is extremely important. The client is in a vulnerable state and relies heavily on the clinician’s information and advice when making decisions about his pet’s care. A solid, relationship-centered plan will relieve the suffering of the pet and enhance its quality of life. It will also provide the needed emotional support system for the owner at this difficult time. Long after the death of the pet, the owner will remember the many kindnesses of the veterinary professional and his staff.

Reference:

Shearer T. Hospice and Palliative Care. In: Handbook of Veterinary Pain Management, Ed. Gaynor J and Muir W III. Mosby, Inc. 2009.

By Jeannine Miesle MA, AAV

Part 1: History / Introduction

Part 2: Pain Perception and Signal Reception

Part 3: Pain Signal Transmission and Pain Pathways

Part 4: Types of Pain, Long-term effects, Referred Pain, and Pain Memory

Part 5: Pain, Stress, and the Body’s Physiological Response to Them

Part 6: Pain in the Avian Species

Part 7: Anesthesia and Analgesia, Chronic Pain (Please scroll down)

Part 8: Quality-of-Life Issues

Part 9: Pain Assessment in Birds / Quality of Life

Part 10: Hospice and Palliative Care for Pets, Strategy for Comprehensive Care, & Conclusion

Part 7: Anesthesia and Analgesia, Chronic Pain

Regional Anesthesia and Analgesia

Local anesthetics such as lidocaine and bupivacaine block the sodium channels in the nerve axon. These channels carry the nerve impulses in the nerve fibers to the spinal cord and brain. They interfere with the conduction of the action potentials, or nerve sensations, along the nerve. The events from the first recognition of pain, the transmission to the spinal cord, the modulation and transmission to the brain, ending with the movement away from the painful stimulus happen almost instantaneously. The neuron path travels at about 700 mph.

Veterinarians and their physician and dental counterparts use a technique for local anesthesia called a “splash block.” Dentists inject a tiny amount (called a bleb) of Novocain in first, and when it has numbed the area a little, they inject another and another until the entire area is numb. Veterinarians make several subcutaneous injections; the space in the skin is very thin, so they follow the incision line with little blebs of anesthesia until the entire line is blocked.

Because birds are more sensitive to the effects of the drugs, the practitioner must be very careful about dosage, and will often use a lower dose of anesthesia than he would for mammals. Also, systemic uptake of the drug is more rapid with birds, and metabolism may be prolonged, increasing the possibility of toxic reactions. Side effects may include fine tremors, ataxia, sleepiness, recumbency (lying down), seizures, stupor (unresponsiveness), cardiovascular effects, and death.

When general anesthesia is needed, the two most commonly used gases are isoflurane and sevoflurane. These two gases are very safe; they are not volatile as previous gases had been, and patients awaken without the confusion that had occurred with previous gases. The bird is given an opioid once he is anesthetized to diminish the painful stimuli occurring during and after the surgery. Post-operative opioids are administered every 2-3 hours intramuscularly to maintain the analgesic effect.

Drugs may be given orally or parenterally (in a way other than by mouth or into the digestive tract.) Injections may be given:

1. Intraosseously (into the bone)

2. Subcutaneously (into the skin)

3. Intramuscularly (into the muscle)

4. Intrasternally (into the sternum) or

5. ly (into the vein)

There are two different types of analgesic pain killers: opiods and Non-Steroidal Anti-Inflammatories (NSAIDS). Opiods reversibly bind to specific receptors in the central and peripheral nervous systems. Clinical effects depend on the preparation of the drug, the dose, the route of administration, and the species being given the drug. NSAIDS work to reduce the cyclooxygenase (COX) enzymes in the body. Cyclooxygenase is an enzyme produced by the body to respond to tissue injury. COX-2 inhibitors block prostaglandins which cause pain and inflammation. Since COX-1 enzymes also protect the stomach and promote blood clotting; it is advisable not to inhibit these enzymes.

COX-2 inhibitors also decrease the sensitivity of the nerve endings. NSAIDS are used mostly to relieve arthritis pain and visceral, muscular pain, and to decrease inflammation associated with surgery. When injury occurs, the COX enzymes initiate a cascade of reactions which release substances that cause inflammation and sensitization of the nerve endings. NSAIDS inhibit these COX-2 enzymes, thereby reducing inflammation at the site of the injury.

Chronic Pain

Chronic, painful conditions, such as joint disease and neoplasia, are progressive and degenerative. It’s often difficult to assess and treat these conditions in birds since the response to analgesia is based on the evaluation of behavior of each bird.

NSAIDS are the first course of therapy for chronic disorders. They have no sedative effects and last longer than opiods. Carprofen, meloxicam, and celecoxib are frequently administer as they have few side effects and may be administered orally in small birds. Dosages begin low and increase over time as necessary. Monitoring renal and hepatic function every few months and CBC’s are recommended. Stronger NSAIDS may be needed for degenerative joint disease and cancer; however, they come with the risk of renal toxicity and gastric ulceration when given in high dosages. If the pain is not controlled with NSAIDDS, opioid use may be indicated.

Many medications and modalities used in mammals, especially dogs and cats, have not been tested in birds. Cancer treatment, although now commonplace in mammals, is generally not used in birds because of the dangers of side effects and lack of sufficient evidence of their success. Birds are too fragile for such aggressive therapy.

Reference: Paul-Murphy J. Pain management for the Pet Bird. In: Handbook of Veterinary Pain Management. Ed. James Gaynor, William Muir III. Mosby, Inc 2009

By Jeannine Miesle MA, AAV

Part 1: History / Introduction

Part 2: Pain Perception and Signal Reception

Part 3: Pain Signal Transmission and Pain Pathways

Part 4: Types of Pain, Long-term effects, Referred Pain, and Pain Memory

Part 5: Pain, Stress, and the Body’s Physiological Response to Them  (Please scroll down)

Part 6: Pain in the Avian Species

Part 7: Anesthesia and Analgesia, Chronic Pain

Part 8: Quality-of-Life Issues

Part 9: Pain Assessment in Birds / Quality of Life

Part 10: Hospice and Palliative Care for Pets, Strategy for Comprehensive Care, & Conclusion

Part 5: Pain, Stress, and the Body’s Physiological Response to Them

An animal’s well-being should include

“The Five Freedoms”

Freedom from thirst, hunger, and malnutrition

• Access to fresh water and a healthful diet

Freedom from discomfort

• Suitable environment, shelter, and a resting place

Freedom from pain, injury, and disease

• Prevention of cruelty and illness by care and rapid treatment

Freedom to express normal behavior

• Provision of space, facilities, and company of the animal’s own kind

Freedom from fear and distress

• Assurance of conditions that avoid stress and mental suffering

Wm. W Muir III

Stress is a biological response that an animal exhibits when it perceives a threat. Its internal state of well—being (homeostasis) is jeopardized. In the past, most vets only concerned themselves with the body’s response to injury or surgical trauma, but today they realize that there are many factors which can put homeostasis at risk.

The Central Nervous System (CNS) can modify the response of the body to the various stressors, such as pain, surgery, restraint, and confinement. Birds can experience trauma from auditory and visual stimuli identical to somatosensory input from damaged tissue. Stress modifies the animal’s memory, thus serving as a protective role in diverting the body’s resources to cope with the stressor. If the body cannot respond effectively to stress, it cannot maintain homeostasis, and the result is dysfunction, disease, and suffering. This “sickness syndrome” hastens death.

It is uncertain whether animals perceive pain and suffering in the same way humans do because they live in the present and cannot understand death or future suffering. Its interaction with its environment and external events determines its well-being. This interaction incorporates feeling, perception and awareness, so if he perceives an event as threatening, the response will be the same whether it is threatening or not; therefore, it is ethical and humane to minimize stress because of the adverse reaction to it all animals face.

Pain serves a protective function by warning the animal of real or impending tissue damage. Acute and chronic pain produce stress, and when severe, increase neuroendocrine activity and profound behavior changes. Environmental factors can produce anxiety and feather that sensitize and amplify the stress response to painful stimulus. The severity and duration of pain determine the consequences of the animal’s pain in terms of stress and suffering.

Stress alters the release of the hormones in the body. Some of the hormones that are affected are cortisol, epinephrine, glucagon (insulin for mammals), the growth and thyroid hormones, and vasopressin, which aids the body in retaining the necessary amount of water.

The metabolism is also affected by stress. Unbalanced carbohydrates can lead to hyperglycemia, poor wound-healing, infections, and morbidity. Fat and protein metabolism are disturbed, causing the body to be unable to metabolize these properly.

The Immune System

Although most people think the immune system’s primary purpose is to identify and destroy foreign substances, it also functions as a sense organ that communicates injury-related information to the brain. It can be activated or depressed by stress; thus, pain, whether accidental or intentional (e.g. surgery), modulates (changes) the immune response. The key elements that determine how the immune system responds to pain are intensity and duration. Chronic pain suppresses the immune system’s responses, and mild-to-moderate pain from tissue trauma activates the immune system’s messengers.

The Acute-Phase Response of the immune system is triggered by severe stress from any cause. This response releases proteins from the liver, which acts in repairing tissue. Excessive production of these proteins can contribute to Systemic Inflammatory Response Syndrome (SIRS).

Morphological Changes

Morphological changes brought about by chronic stress or pain are typical of long-term aversive stimuli and include failure to thrive, feather loss, poor feather condition, weight loss, and acceleration of aging.

Reference:

Muir W III. Pain and Stress. In: Handbook of Veterinary Pain Management. Ed: James Gaynor, Wm Muir III. Mosby Inc, 2009

By Jeannine Miesle MA, AAV

Part 1: History / Introduction

Part 2: Pain Perception and Signal Reception

Part 3: Pain Signal Transmission and Pain Pathways

Part 4: Types of Pain, Long-term effects, Referred Pain, and Pain Memory

Part 5: Pain, Stress, and the Body’s Physiological Response to Them

Part 6: Pain in the Avian Species (Please scroll down)

Part 7: Anesthesia and Analgesia, Chronic Pain

Part 8: Quality-of-Life Issues

Part 9: Pain Assessment in Birds / Quality of Life

Part 10: Hospice and Palliative Care for Pets, Strategy for Comprehensive Care, & Conclusion

Part 6: Pain in the Avian Species

Recognizing Avian Pain

All animals are capable of perceiving and transmitting pain stimuli. Even though they are unable to express their pain verbally, they convey their discomfort emotionally through their body language. Birds know there is no survival advantage to displaying their pain outwardly; however, birds perceive and respond to noxious stimuli in the same way other animals and mammals do.

Because of their reluctance to demonstrate pain, birds are often undertreated for it. Most bird owners and many practitioners find it difficult to determine the presence and severity of the bird’s pain. Birds held in a hospital setting often experience an even higher level of pain and anxiety due to isolation in an unfamiliar place and separation from their families.

Scientific information concerning appropriate therapies and dosages for birds is lacking in much of the literature; as a result, many practitioners do not have the knowledge needed to adequately treat pain in their avian patients. When assessing avian pain, the clinician must consider the age, species, gender, and environment of his patient. He must also determine the source of this pain and whether there exists a concurrent illness which could be affecting the pain level.

When a bird experiences pain, some of the normal behaviors are usually changed or absent. These include:

• Decreased social interactions: Perching away from other birds, decreased grooming of self or other conspecifics (birds of its own species), decreased interactions with owner.

• Guarding behavior. Change in posture to protect a painful area, decreased activity

• Increased aggression toward conspecifics or owner

• Grooming behavior at painful site or generalized, feather-destructive behaviors, self-mutilation

(For complete Quality of Life and Pain Assessment questionnaires, please see Part 9 of this series.)

Some behaviors are obvious, but others may be more subtle. Interactions with the owner may occur less often than usual, and antisocial behaviors might begin to take place. Guarding behavior, during which the bird attempts to protect the painful area, is usually displayed. The bird may become aggressive, scream, or bite when handled. An increase or decrease in preening may take place, and this may lead to feather-picking and self-mutilation, particularly over the area of discomfort. It has been observed that distracting the bird from itself reduced the severity of pain.

Physiology of Avian Pain

The physiology of avian pain first involves the peripheral nerves (nociceptors) detecting the noxious stimulus, or painful event, whether it be mechanical, thermal, or chemical. The nerves must then transmit the impulses to the dorsal root of the spinal cord, where they are modulated (changed) and projected to the brain for central processing of the information. The brain then determines the perception of the noxious stimuli. (Pain perception in birds is considered to be the same as in mammals.)

Compared to mammals, birds are less sensitive to lower temperatures and have a higher threshold to high temperatures, possibly because their body temperatures are higher. Therefore, they have a wider range of thermal tolerance than mammals.

As stimulus intensity increases, the number of nerve responses increases. Peripheral nerve sensation increases when inflammation is added to a normally painful stimulus. Cell damage and leakage lead to central sensitization, and the increase in excitability of the spinal cord over a long period of time triggers hyper-sensitization of a wide range of neurons that don’t respond under normal circumstances, such as the C-Fibers. These only activate during periods of extreme pain.

This has led physicians and veterinarians to conclude that the earlier analgesics are given, the better the pain control will be. If analgesics are given before the painful even (e.g., surgery) is performed, rather than after the start of neuro-stimulation, the spinal excitability can be suppressed. The earlier pain is treated, the less total analgesia is needed, both during and after surgery. In studies using pigeons, birds receiving analgesia before surgery recovered faster than those receiving it only during and after surgery.

Treatment of Pain

Identifying the cause of pain and site of tissue damage in birds is challenging, but it is necessary in order to select the correct analgesic drugs and supportive care. Drug therapy is used to resolve the injury or disease and to decrease the peripheral pain signals leading to the brain. In some cases, the patient’s pain and other symptoms may need to be treated before the cause of the pain is known and a diagnosis is reached. In such cases, the choice of analgesic drugs will need to be conservative.

Both physicians and veterinarians have, in the past several decades, learned that the use of multimodal analgesia is more effective than the use of a single drug. Combining analgesics which work by different mechanisms can augment the pain relief. Many times, administering two or more analgesics produces a synergistic effect; the medications work together to diminish the pain. Combining drugs reduces not only the amount of the drugs used, but the side effects of each drug.

A patient undergoing surgery will receive:

• A local anesthetic (such as lidocaine) at the incision site,

• An opioid administered directly before and after surgery, and

• An NSAID (non-steroidal anti-inflammatory) given during surgery and for several days following the procedure.

Giving the painkiller before the surgery will lessen the need for stronger opioids during and after the surgery by dampening the nociceptive pain messages being sent to the brain. Often, the patient will receive adjunctive drugs, such as tranquilizers, to reduce anxiety, thus enhancing the effects of the analgesia. The avian patient also needs supportive care during and after the traumatic event; he needs to be kept warm, dry, and clean. A separate area just for birds should be part of the clinic, since the sounds and smells of other animals, particularly predators like dogs and cats, can disturb the bird and heighten its anxiety, thus lowering the effect of the analgesic drugs. Gentle, soothing human contact is essential.

Reference:

Paul-Murphy J. Pain management for the Pet Bird. In: Handbook of Veterinary Pain Management. Ed. James Gaynor, William Muir III. Mosby, Inc 2009