Effectiveness of low-dose midazolam plus ketamine in the prevention of shivering during spinal anaesthesia for emergency lower limb surgery

Abstract

Objective: This study was conducted to compare the effectiveness of two  different dosages of intravenous midazolam in combination with ketamine in the prevention of shivering during spinal anaesthesia for emergency  lower limb surgery.
Design: This was a prospective, randomised, double-blind, placebo- controlled study.
Setting and subjects: We studied 90 patients with American Society of  Anesthesiologists classification I and II, aged between 18 and 60 years old, and randomly allocated to receive either a combination of low-dose  midazolam 0.02 mg/kg plus ketamine 0.25 mg/kg (Group A), or a combination of higher-dose midazolam 0.04 mg/kg plus ketamine 0.25 mg/kg (Group B), or normal saline as the control group (Group C), after an intrathecal injection of 0.5% hyperbaric bupivacaine 12.5-15 mg.
Outcome measures: The outcomes measured were the incidence and the  degree of shivering, the effectiveness and the side-effects of two different dosages of the drugs in preventing shivering.
Results: In this study, the incidence of shivering was 46% in Group C, which was significantly higher than that in Group A (16%) and Group B (10%) (p-value < 0.05). However, there was no difference between Group  A and B (p-value = 0.704). The number of patients with shivering grade ≥ 2 was significantly higher in Group C than it was in Groups A and B (p-value < 0.05), but not between Group A and Group B. It was also found that  there was no difference in the haemodynamic parameters in all three groups. However, patients in Groups A and B were more sedated (p-value  < 0.05), and had higher incidence of nystagmus than those in Group C (p-value < 0.001).
Conclusion: Low-dose midazolam 0.02 mg/kg plus ketamine 0.25 mg/kg was equally effective when compared with a higher dose of midazolam 0.04 mg/kg plus ketamine 0.25 mg/kg in preventing shivering during  spinal anaesthesia for emergency lower limb surgery. There were no significant changes in the haemodynamic parameters in all three groups. However, patients in the midazolam plus ketamine groups were more  sedated and had a higher incidence of nystagmus.

Keywords: midazolam, ketamine, spinal anaesthesia, emergency lower limb surgery, temperature