We must all die. But that I can save him from daysof torture, that is what I feel as my great and evernew privilege. Pain is a more terrible lord ofmankind than even death itself. ALBERT SCHWEITZER

Pain has long been feared. The quotation from Albert Schweitzer is probably representative of the feelings of most patients and physicians alike. Management of pain in the critically ill patient demands extreme dedication to the provision of analgesia that is appropriate for the specific clinical situation. An intensivist's challenge is vast, and lies in understanding the mechanisms of nociception, understanding the influences of stress responses evoked during surgery or non-surgical critical illness, understanding pharmacokinetics and pharmacodynamics, understanding the influences of drugs on changes in volume of distribution or organ dysfunction, possessing a mastery of techniques which may be indicated under certain clinical circumstances and finally trying to ensure the appropriate level of analgesia many times under conditions when direct patient feedback is unattainable. As one might expect, the challenges are many and complex.

The causation of pain is generally multifactorial in the critical care unit. Depending on the setting, patients may possess immense surgical wounds or experience pain emanating from nonsurgical sources. Most patients will have catheters of some classification inserted, for example Foley catheters, pulmonary artery catheters, central venous catheters, or arterial catheters, and a vast array of drains. Tubes inserted may include endotracheal, nasogastric, Dobhoff, and thoracostomy tubes. In addition to surgical trauma, pain may originate as a result of nonsurgical etiologies and may include myocardial ischemia and/or infarction, pancreatitis, a sickle cell anemia crisis, subarachnoid hemorrhage, nephrolithiasis, or cholecystitis, all of which require medical attention and, if deemed serious, could mandate admission to the critical care unit.

This article will attempt to review briefly what is understood and what is not understood about pain and its management. Topics include pain assessment, knowledge of analgesia administration, the physiologic influences of pain (both surgical and non-surgical), and the impact of pain on patient outcome.