Post-anesthetic shivering

Introduction: post-anesthetic shivering is caused by one of the greatest dissatisfactions during the immediate postoperative period. It is a common event, also potentially damaging because it increases the metabolic demand for oxygen. Objective: To make an update on post-anesthetic shivering and its prophylaxis. Methods: It constitutes an oscillatory muscle activity to increase heat production. Its etiology is unknown, although it is attributed to many causes. Its frequency varies between 6.3 and 66 %. 5 to 65 % are related to general anesthesia, and 30 % to regional anesthesia. Under general anesthesia, the central temperature decreases from 0.5 to 1.5 °C in the first hour after induction, as in regional anesthesia. This mechanism is caused by redistribution of heat from the center to the periphery. All anesthetics, opioids and sedatives decrease vasoconstriction and the autonomic control of thermal regulation, and facilitate hypothermia. It occurs most often in young patients, male, to whom halogenated anesthetic agents are administered with anesthetic prolonged surgical time. Many items indicate that in the homeothermic species a thermoregulator system is present, which coordinates the defense against the environmental temperature to maintain the internal temperature in a narrow threshold. The combination of anesthetic inducing agents and exposure to cold environment make patients present post-anesthetic shivering. Prophylaxis is attained by using meperidine, clonidine and tramadol. Ketamine is a phencyclidine, which produces electrophysiological dissociation between the limbic and cortical systems. It is bound to two molecular targets in the brain: dopaminergic terminals in the accumbens nucleus and the N-methyl aspartate receptor. When ketamine binds to these receptors, it inhibits the release of dopamine. Conclusions: Post-anesthetic shivering constitutes an adverse effect of anesthesia, which can be avoided. Ketamine, for its action mechanism, seem to play a role in prevention, because when such receptor is blocked, it is inferred to module, at some extent, thermal regulation at various levels.