Objective: To summarize the challenges to recognizing pain in critically ill patients, the rationale for treatment even in the absence of signs of pain, and the therapeutic options available in the intensive care environment.
Etiology: Pain is one of many stressors challenging the critically ill patient, and may in turn be multifactorial in nature. Common causes include local and systemic inflammation, injuries, diagnostic and therapeutic procedures, immobilization, and thrombosis.
Diagnosis: Critically ill animals with pain may not demonstrate overt behavioral or physiologic signs of distress. Therefore, pain must be assumed to be present for animals whose condition puts them at risk.
Therapy: Currently available analgesic and sedative drugs and methods of delivery are described. Several useful analgesics and sedatives may be co-administered as fluid additives to provide continuous therapy.
Prognosis: There is growing evidence that the neuroendocrine stress response to severe injury or illness may become sufficiently intense to contribute to morbidity and mortality. Many therapeutic analgesic and sedation options provide good control of pain and stress, and in some circumstances this may improve the outcome of critical illness.