Prophylactic vs. therapeutic magnesium sulfate for shivering during spinal anesthesia

IntroductionShivering is one of the most common complications of neuraxial blockade. Some patients find shivering sensation worse than surgical pain. Therefore, both prevention and treatment of established shivering should be regarded as clinically relevant intervention in the perioperative period. The aim of our study is to compare the efficacy of magnesium sulfate when used for prevention or treatment of shivering following spinal anesthesia.MethodsIn this prospective, double blind, placebo controlled study, 120 ASA I, II patients undergoing surgery under spinal anesthesia were randomized into 3 groups. Following intrathecal injection, Group P (prophylactic) was given MgSO4, 50 mg/kg I.V. bolus + 2 mg/kg/h infusion. Group T (therapeutic) was given MgSO4 50 mg/kg I.V. bolus as a therapy when shivering occurred. If shivering persisted, they received 25 mg/kg I.V. bolus. Group C (control) received saline at identical times. Meperidine was given as rescue if shivering persisted. Shivering grade 3/4 was regarded as significant. Core temperatures, incidence of shivering, and side effects were recorded.Main resultsTotal incidence of shivering, grade 3/4, was 15% in Group P, 45% in Group T, and 50% in Group C (p < 0.01). Magnesium sulfate significantly reduced the incidence and gain of shivering. The use of rescue meperidine was more in Group P (20%) and Group C (50%) compared to none in Group T (p < 0.05, p < 0.01, respectively). Significant reduction in core temperature occurred in the Mg groups compared to the control group p < 0.05. No correlation was found between patients who shivered and core temperature or ΔT. Hypotension was more frequent in Group P; nausea and vomiting were more in Mg groups than control group p < 0.05.ConclusionFollowing spinal anesthesia, prophylactic MgSO4 infusion lowered incidence of shivering. When shivering did occur, MgSO4 proved to be an effective treatment with minimal side effects.