ABSTRACT
It is the obligation of all veterinarians to minimize pain and suffering in patients under their care. This obligation is even greater for those veterinary personnel who strive to care for the critically injured and sick animal. Critically ill patients frequently suffer from pain and distress associated with trauma or disease. The well-intentioned medical and surgical interventions designed to prolong or save lives often induce additional tissue trauma and pain. Due to their limited efficacy to treat severe pain, opioid agonist-antagonists (e.g., butorphanol) and partial agonists (e.g., buprenorphine) play a secondary role in pain management of the critically ill patient. Respiratory depression is the side effect that causes the most concern, particularly in the critically ill patient. Opioids alter respiratory center sensitivity to carbon dioxide, with the potential of causing hypoventilation and respiratory acidosis. In the animal breathing room air, clinically significant hypoventilation will lead to hypoxemia.
