The necessity and the efficacy of the second administration of midazolam for sedation during spinal anesthesia

We investigated the necessity of the second additional administration of intravenous midazolam for sedation during spinal anesthesia and the adequate dose if necessary. Fifty patients with ages between 35 to 70 years for spinal anesthesia were administered midazolam 0.05 mg.kg-1 intravenously during surgery. Thirty-four patients opened their eyes spontaneously and to these patients midazolam 1 mg was administered every three minutes until patients closed their eyes. All 34 patients closed their eyes with 1 mg of midazolam. Patients opened their eyes again at 47 +/- 16 minutes (mean +/- SD) after the first dose (0.05 mg.kg-1) and at 24 +/- 14 minutes after the second dose (1 mg). The decreases in blood pressure, heart rate and percutaneous arterial oxygen saturation after the administration of midazolam were less after the second administration than those after the first one. The percent of patients with amnesia was larger in the patients with only first administration than those with the second dose. These results suggest that the additional dose of midazolam is not necessary after intravenous midazolam 0.05 mg.kg-1 until patients open their eyes and the additional 1 mg is useful even after patients have opened their eyes.