Best practice & research. Clinical anaesthesiology
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Best Pract Res Clin Anaesthesiol · Dec 2008
ReviewThermoregulatory management for mild therapeutic hypothermia.
In recent years the use of mild therapeutic hypothermia as a means of neuroprotection has become an important concept for treatment after cerebral ischemic hypoxic injury. Mild therapeutic hypothermia has been shown to improve outcome after out-of-hospital cardiac arrest, and many studies suggest a beneficial effect of mild therapeutic hypothermia on patient outcome after traumatic brain injury, cerebrovascular damage and neonatal asphyxia. This review article explores the numerous possibilities and methods for the induction of mild therapeutic hypothermia, reviews thermoregulatory management during maintenance and discusses associated risks and complications.
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Core body temperature is one of the most tightly regulated parameters of human physiology. At any given time, body temperature differs from the expected value by no more than a few tenths of a degree. ⋯ Consequently, perioperative hypothermia leads to a number of complications including postoperative shivering (which unacceptably increases patients' metabolic rates), impaired coagulation, prolonged drug action, and negative postoperative nitrogen balance. In this review I will describe how anesthesia and surgery impair thermoregulation, the resulting changes in heat balance, and the physiological responses provoked by perioperative alterations in body temperature.
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This chapter describes the incidence, mechanisms and possible consequences of hypothermia during cardiac surgery, including protection against ischaemia, alteration of the coagulation cascade and the inflammatory response. Various temperature-specific topics related to cardiac surgery are discussed, including the use of hypothermia or normothermia during cardiopulmonary bypass, and the temperature reached during rewarming at the end of cardiopulmonary bypass and its deleterious consequences for the brain (postoperative neurocognitive dysfunction). ⋯ Modern cardiac techniques, such as off-pump surgery and minimal extracorporeal circulation, and their implications for temperature preservation are discussed. Finally, a protocol is proposed that combines mild intra-operative hypothermia with peripheral active warming in order to avoid the need for fast, intense rewarming, thus avoiding the potential incidence of brain damage.
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Perioperative hypothermia is a common and serious complication of anesthesia and surgery and is associated with many adverse perioperative outcomes. It prolongs the duration of action of inhaled and intravenous anesthetics as well as the duration of action of neuromuscular drugs. Mild core hypothermia increases thermal discomfort, and is associated with delayed post anaesthetic recovery. ⋯ Hypothermia adversely affects antibody- and cell-mediated immune defences, as well as the oxygen availability in the peripheral wound tissues. Furthermore mild hypothermia triples the incidence of postoperative adverse myocardial events. Thus, even mild hypothermia contributes significantly to patient care costs and needs to be avoided.