Dexmedetomidine, Ketamine and Dexmetedomidine-Ketamine Combination for Control of Shivering During Regional Anaethesia

Overview

Shivering is defined as an involuntary, repetitive activity of skeletal muscles. The incidence of shivering has been found to be quite high, approximately 40-50% in different studies. It can double or even triple oxygen consumption and carbon dioxide production. Shivering also increase intraocular and intracranial pressure, and may contribute to increased wound pain, delayed wound healing, and delayed discharge from post-anaesthetic care. Apart from being an uncomfortable experience, its deleterious effects deserve primary prevention and rapid control on occurence.

Shivering is a physiological response to core hypothermia in an attempt to raise the metabolic heat production. The main causes of intra and postoperative shivering are heat loss, increased sympathetic tone, pain, and systemic release of pyrogens. Spinal anaesthesia significantly impairs the thermoregulation system by inhibiting tonic vasoconstriction, which plays a significant role in temperature regulation. It also causes a redistribution of core heat from the trunk (below the block level) to the peripheral tissues. These factors predispose patients to hypothermia and shivering. The treatment of shivering includes both pharmacological and non-pharmacological methods. The non-pharmacological management is by external heating like the use of forced air warming, warming blankets, warmed fluids etc. According to the results of meta-analysis, the most frequently reported pharmacological interventions include clonidine, pethidine, tramadol, nefopam, and ketamine. Unfortunately, no gold standard treatment is known for shivering as the administration of all the available drugs is associated with various adverse effects. Dexmedetomidine, a congener of clonidine, is a highly selective adrenoceptor agonist. It has been used as a sedative agent and is known to reduce the shivering threshold. Few studies which have explored its anti-shivering potential have inferred that dexmedetomidine is an effective drug without any major adverse effect and provides good haemodynamic stability. Ketamine has been tried to prevent shivering during anaesthesia with good results. Ketamine a competitive NMDA receptor antagonist has a role in thermoregulation at various levels. NMDA receptor modulates non-adrenergic and serotoninergic neurons in locus coeruleus. It is used as anti-shivering agent. Shivering is a physiological response to core hypothermia in an attempt to raise the metabolic heat production. The main causes of intra and postoperative shivering are heat loss, increased sympathetic tone, pain, and systemic release of pyrogens. Spinal anaesthesia significantly impairs the thermoregulation system by inhibiting tonic vasoconstriction, which plays a significant role in temperature regulation. It also causes a redistribution of core heat from the trunk (below the block level) to the peripheral tissues. These factors predispose patients to hypothermia and shivering. The treatment of shivering includes both pharmacological and non-pharmacological methods. The non-pharmacological management is by external heating like the use of forced air warming, warming blankets, warmed fluids etc. According to the results of meta-analysis, the most frequently reported pharmacological interventions include clonidine, pethidine, tramadol, nefopam, and ketamine. Unfortunately, no gold standard treatment is known for shivering as the administration of all the available drugs is associated with various adverse effects. Dexmedetomidine, a congener of clonidine, is a highly selective adrenoceptor agonist. It has been used as a sedative agent and is known to reduce the shivering threshold. Few studies which have explored its anti-shivering potential have inferred that dexmedetomidine is an effective drug without any major adverse effect and provides good haemodynamic stability. Ketamine has been tried to prevent shivering during anaesthesia with good results. Ketamine a competitive NMDA receptor antagonist has a role in thermoregulation at various levels. NMDA receptor modulates non-adrenergic and serotoninergic neurons in locus coeruleus. It is used as anti-shivering agent.