Efficacy of Intrathecal Versus Intravenous Dexmedetomidine for Prevention of Post Spinal Anesthesia Shivering in Patients Undergoing TURP

Shivering is a frequent complication following SA. It is distressing and unpleasant experience for patients. The incidence of shivering has been reported to be about 36-85% after SA. It is more common in TURP that may be due to absorption of large amount of irrigating fluid at room temperature. Shivering may occur as a response to hypothermia. However, it may also occur in normothermic patients. SA impairs the thermoregulation system by inhibiting tonic vasoconstriction below the level of anesthesia through sympathetic and somatic neural blockade. With internal redistribution of heat from the core to the peripheral compartment, the loss of thermoregulatory vasoconstriction results in increased heat loss from body surfaces in excess of metabolic heat production. Excessive shivering can result in an increased oxygen demand up to 400% of normal and induce metabolic derangements such as hypoxemia, lactic acidosis and hypercarbia. Therefore, shivering may cause problems in patients with low cardiac and pulmonary reserves.

Considering these undesirable consequences of shivering, measures to prevent in the postoperative period are important. Various drugs have been investigated for the prevention or treatment of postoperative shivering, including meperidine, ketamine, tramadol, doxapram and dexmedetomidine.

Dexmedetomidine is an α 2-agonist that decreases vasoconstriction and shivering thresholds and when administered with meperidine additively reduces the shivering threshold in healthy volunteers. Intraoperative dexmedetomidine reduces postanesthetic shivering as does meperidine after surgery.

One bolus dose of dexmedetomidine 1 μg/kg with or without continuous infusion was used in the previous antishivering studies. Dexmedetomidine also has sedative and analgesic effects in the postoperative period. Patients who received an intraoperative injection of dexmedetomidine were more sedated after surgery than those who received placebo. This can be a disadvantage particularly for patients undergoing outpatient surgery.

Addition of intrathecal dexmedetomidine to heavy bupivacaine 0.5% was more advantageous than fentanyl with special regard to its analgesic properties in diabetic surgical patients. Few studies have been done to evaluate the efficacy of intrathecal dexmedetomidine in attenuation and prevention of shivering in TURP.