Effect of premedication with atropine sulphate on arterial blood-gases and pH

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

The effectiveness of midazolam and a mixture of morphine-perphenazine premedication to produce sedation and their effects on preoperative oxygen saturation (SaO2) were examined. Eighty-five patients whose SaO2 measured with a pulse oximeter was greater than 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 SaO2 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 morphine-perphenazine (2) and placebo (1) (P less than 0.0001). As well, there was a decrease in the SaO2 in the morphine-perphenazine group (1.7 +/- 2.7%, P less than 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 morphine-perphenazine and placebo without effect on SaO2 whereas morphine-perphenazine showed a decrease in SaO2 preoperatively.

Arterial hypoxaemia following premedication in patients with coronary artery disease

The effect of premedication with morphine and scopolamine, morphine alone, and scopolamine alone on arterial oxygen tension has been studied in patients with coronary artery disease undergoing bypass operations. Control arterial blood samples were obtained with the patients in the supine position breathing room air the day before operation. A second arterial blood sample was taken in the induction room with the patient breathing room air in the supine position. In the first group (scopolamine only) and second group (morphine only) cH+ (pH), PaCO2 and PaO2 did not change. In the third group (morphine and scopolamine), however, PaO2 decreased, while PaCO2 and cH+ increased (pH decreased). The changes in cH+ and PaCO2 were statistically significant, but of no clinical importance. The present study suggests that, when morphine and scopolamine premedication is used for patients with coronary artery disease, simultaneous administration of oxygen is important in helping to eliminate a possible cause of preoperative myocardial ischaemia.

Atropine and hyoscine

The drugs atropine and hyoscine are reviewed in the context of their use by anaesthetists. The results of recent studies are stressed and guidelines given for use of these drugs in modern anaesthetic practice.