A comparison of morphine-perphenazine and midazolam on preoperative sedation and arterial oxygen saturation

The effectiveness of midazolam and a mixture of morphineperphenazine premedicalion to produce sedation and their effects on preoperative oxygen saturation (SaO2) were examined. Eightyfive patients whose SaO2 measured with a pulse oximeter was > 90% and who were not receiving narcotic sedatives or oxygen were randomized to three groups. Each patient had his SaO2 recorded before premedication with placebo (saline), midazolam 0.08 mg · kg−1 or morphine 0.15 mg · kg−1 with perphenazine 2.5–5.0 mg im. From 30–90 min later, prior to anaesthesia SaC2 was repeated, and a sedation score was obtained by a blinded observer using a seven point scale. Median sedation scores were greater for midazolam (4) than for morphineperphenazine (2) and placebo (1) (P < 0.0001). As well, there was a decrease in the SaO2 in the morphineperphenazine group (1.7 ± 2.7%, P < 0.001) but not in the midazolam and placebo groups (0.1 ± 2.3%, – 0.8 ±2.1%). In conclusion midazolam produced greater sedation than morphineperphenazine and placebo without effect on SaO2 whereas morphineperphenazine showed a decrease in SaO2 preoperatively.