Background: Discomfort during procedures under spinal anesthesia (SA) can lead to poor posture and autonomic swings, which can be alleviated by sedation. We evaluated the sedative efficacy of intravenous (IV) low-dose ketamine compared to midazolam during SA. We hypothesized that low-dose ketamine may be as effective as midazolam.
Methods: Eighty patients, ASA I-II, aged 18-50 years, undergoing unilateral inguinal hernia repair, were randomly assigned to receive either an IV single bolus dose of ketamine at 0.5 mg/kg or midazolam at 0.03 mg/kg over 10 minutes. Sedation was evaluated up to 90 min after SA using the Modified Observer's Assessment of Alertness/ Sedation (MOAA/S) scale and A-line Autoregressive Index (AAI). Heart rate, mean blood pressure and oxygen saturation were continuously monitored. The time to the first analgesic request, any complications, and patient and surgeon satisfaction were documented.
Results: Patients in the ketamine group achieved a MOAA/S score of 4 (P=0.029) and recovered to an AAI score > 60o (P=0.029) faster than those in the midazolam group. Heart rate and oxygen saturation were similar between the groups. Hypotension occurred significantly more in the midazolam group (P= 0.003), while disruptive movements (P=0.001) and blurred vision (P=0.005) occurred only in the ketamine group. The patient and surgeon satisfaction were similar across groups.
Conclusions: The use of a single low dose of both ketamine and midazolam was effective in providing adequate sedation. However, clinically, ketamine caused a rapid onset of sedation and, instrumentally, led to a faster recovery compared to midazolam.