safety, benefits and effectiveness of different intravenous subanesthetic doses of ketamine when combined with small dose of midazolam before combined spinal epidural technique for orthopedic lower extremity surgery

ABSTRACT

In a double blind, randomized, and controlled study of 100 patients [aged 20-60 years], we compared the effect of intravenous [IV] coadministration of different small doses of ketamine [0.00, 0.15, 0.30, and 0.45 mg/kg] with midazolam 0.03 mg/kg in alleviating patient anxiety and pain during establishment of combined spinal epidural [CSE] technique. Patients received midazolam 0.03 mg/kg with placebo [Group C, n= 25] or ketamine 0.15 mg/kg IV [Group K1, n= 25], 0.30 mg/kg IV [Group K2, n= 25] or 0.45 mg/kg IV [Group K3, n= 25], 5 minutes before local analgesic infiltration at the site of SCE and 10 minutes before performing CSE. Scores for sedation, patient's behavior to CSE puncture, and ease of CSE establishment, the mean arterial blood pressure [MBP], heart rate [HR] and arterial oxygen saturation [SpO2] were recorded; the need for ephedrine, atropine and supplemental O2 inhalation was recorded. The incidence of adverse effects especially of unpleasant emergence reactions were recorded. Lastly, the quality of the CSE technique was assessed by the patient and a blind observer. Patients in Group K2 who received midazolam 0.03 mg/kg with ketamine 0.3 mg/kg IV showed ideal scores for sedation, behavior to CSE puncture, and ease of placement of CSE, and best hemodynamic compensation for the inhibitory cardiovascular effects of spinal anesthesia and also for maintenance of normal SpO2. In addition group K2 showed the best quality of anesthesia when assisted by the patient and the blind observer, without significant unpleasant emergence reactions. We conclude that addition of ketamine 0.3 mg/kg to midazolam 0.03 mg was safe, useful, and effective in alleviating patient's anxiety and pain during placement of CSE