Intravenous Dexmeditomidine for Prevention of Spinal Anesthesia Induced Shivering.

Overview

Intraoperative and post operative shivering is a common problem encountered in operating rooms and recovery suites. Shivering under spinal anesthesia has an incidence of 40-60%. Shivering is not only uncomfortable for the patient; additionally it increases minute oxygen consumption, subjecting the patient to a higher risk of cardiovascular complications. A variety of drugs like pethidine, fentanyl, alfentanil, sufentanil, buprenorphine, doxapram, clonidine, and ketanserin, are reported to be effective in suppressing postoperative shivering, yet an ideal drug/ method to be explored. Dexmeditomidine, a sedative and analgesic, may control shivering without significant adverse effects, like nausea and vomitting and respiratory depression. The study design will be randomized controlled parallel trials with sample size of 80,They will be randomized into two equal groups. One group will receive 10 microgram Inj. Dexmeditomedine while the other will recieve inj. normal saline as placebo. The participants will be assessed for intra- and postoperative shivering.

Intraoperative inadvertent changes in the body temperature are quite common. Incidence of inadvertent hypothermia (up to 90%) is much higher than hyperthermia. The hypothermic patients shiver postoperatively after general anesthesia and both introperatively and post operatively during regional anesthesia. Shivering under spinal anesthesia has an incidence of 40-60%. Shivering is not only uncomfortable for the patient; additionally it increases minute oxygen consumption VO2 at the cost of increased presser hormones level, subjecting the patient to a higher risk of cardiovascular complications. Heat loss from skin and surgical site is mostly by radiation. Dropped body temperature in cesarean section under spinal anesthesia is due to a combination of anesthetic-induced impaired thermoregulation i.e. vasodilation and inhibition of vasoconstriction in the blocked dermatomes, which are due to autonomic and motor blockade caused by spinal anesthesia. General anesthesia also leads to hypothermia due to vasodilation and reduced metabolic rate, in the order of 20%-30%. Additional factors are exposure to cold environment, un-warmed cold irrigants/ intra vascular fluids and ventilation with dry anesthetic gases. In spinal anesthesia, due to blocked motor activity below umbilicus, shivering in response to hypothermia is abolished. It interferes with physiologic heat recovery, as human core body temperature should normally be maintained within the narrow range of 36.5-37.5 °C. A variety of drugs like pethidine, fentanyl, alfentanil, sufentanil, buprenorphine, doxapram, clonidine, and ketanserin, are reported to be effective in suppressing postoperative shivering, yet an ideal drug/ method to be explored. Dexmeditomidine which is an alpha-2 agonist, is a new drug used for analgesia and sedation either in perioperative settings or in intensive care units. It is 7-8 times selective alpha 2 agonist than clonidine and was expected to control shivering like clonidine. There are study demonstrating the favorable effect of Dexmeditomidine via infusion in the intraoperative period on shivering after abdominal hysterectomy. In previous studies, a prophylactic single dose of Dexmeditomidine for prevention or aborting shivering was generally found to be effective after general or regional anesthesia. Dexmedetomidine 0.5 mcg/kg I/v as loading dose was found 100% effective in managing post anesthesia shivering after general anesthesia in children. In another study, it was observed that Dexmedetomidine was equally effective compared to tramadol, and was associated with shorter time for complete shivering control and less incidence of nausea vomiting, but prospects of a single sub loading dose in parturients during spinal anesthesia requires exploration as physiologic volume loaded parturients at term are expected to lose more heat by redistribution due to vasodilation caused by spinal anesthesia. OBJECTIVE: To determine the role of single sub loading dose of Dexmeditomidine i.e. 10 mcg (0.1- 0.2 microgram/kg) administered intravenously for prevention of shivering in participants undergoing Cesarean section under spinal anesthesia in a randomized double-blind, placebo controlled parallel study.