Analgesia for feline arthritis (Proceedings)


Analgesia for feline arthritis (Proceedings)

Aug 01, 2009

Awareness of the possibility of pain is the first step to its alleviation and prevention. In some cases, pain is pre-existing and part of the condition for which the patient is presented to us however, thought and careful handling go a long way to reduce the stress, distress and discomfort of the hospital visit. The scope of this presentation is to feline arthritic pain but an introduction on pain, per se, is still warranted.

Understanding pain

Pain evolved as a protective mechanism. Certain types of pain, such as physiologic pain, are beneficial for survival. Conditions resulting in damage to tissues or nerves, on the other hand, are pathological and include visceral and neuropathic forms of pain. The nociceptive response begins with the free nerve endings signaling potential or actual tissue injury. This results from a combination of mechanical (crush), chemical (mediators) or thermal input being translated (transduced) into electric impulses. These impulses are transmitted via the primary afferent (1st order) neuron to the spinal cord where they are modulated in the dorsal horn. The impulse is further transmitted via 2nd order neurons in the spinal tract to the thalamus where the message is received by a 3rd order neuron to be projected to the somatosensory cortex. It is at this point that the impulse is experienced as pain and an appropriate response might be generated.

The implications are important; rather than addressing the alleviation of pain at one level, we have multiple points to target. Using a combination of agents in a multimodal approach is often more effective than using a single modality to treat and prevent pain. Pre-emptive plays a key role in patient care. By blocking the transduction and transmission of input, it is easier to keep patients comfortable.

Recognition of pain

The signs of pain are generally more subtle in cats than in dogs. Some objective clinical signs indicative of pain include

  • Inability to rest/sleep
  • Inappropriate activity level
  • Sitting in the back of the kennel
  • Mental attitude/demeanour (stupor or anxiety)
  • Changes in attitude/personality
  • Poor hair coat
  • Lack of comfort when palpated
  • Facial expression, staring, fixed gaze, dilated pupils
  • Lack of appetite and thirst
  • (Self-mutilation)
  • Vocalizations
  • Posture
  • Tachycardia
  • Tachypnea

Body temperature and blood pressure can be variable. The truest assessment of the presence of pain is response to analgesics resulting in return to normal behaviors.

If a procedure is to be performed or a patient is ill, given the similarities in pain perception between humans and cats, assume that the cat's experience is similar to that of a human and err on the side of humaneness. Through the process of central sensitization, chronic conditions are especially debilitating and interfere with quality of life. Concerns that analgesic agents may be harmful depend on the type of drug and the underlying status of the patient. Factors to be taken into consideration include the integrity of renal and hepatic function, state of hydration and intestinal health. The other side of this is that the cascade of catabolic and detrimental effects that occur as a result of uncontrolled pain may be a greater risk for the patient than the drugs are. Each case needs to be evaluated individually so that the safest protocol is used to blunt or eliminate pain.