Prophylactic use of intravenous tramadol vs intravenous nalbuphine for control of postspinal shivering after knee arthroscopy: a randomized double-blind placebo controlled trial

Abstract

P ost-anesthetic shivering refers to spontaneous, involuntary, rhythmic, oscillating and tremor-like muscle hyperactivity that increases metabolic heat production up to 600% after general or regional anesthesia. Shivering is not only subjectively unpleasant but is physiologically stressful because it elevates blood pressure, heart rate, oxygen consumption, and plasma catecholamine concentrations. Moreover, shivering may aggravate pain and hinder wound closure by simply stretching surgical incisions. The mechanism for shivering after spinal anesthesia may be related to disruption of normal temperature regulation resulting from the re-distribution of body heat from the center of the body to the periphery. As a result, the afferent temperature signal in the anesthetized area is not transmitted to the thermoregulation center located in the hypothalamus.