[Effects of midazolam on the delivery and consumption of myocardial oxygen in the postoperative period of children undergoing heart surgery].

Introduction: The aim of this study was to evaluate the effect of midazolam on the variables which determine myocardial oxygen delivery and consumption relationship (endocardiac viability index) in children undergoing cardiac surgery under extracorporal circulation.

Methods: The study was carried out in 15 children to whom a doses of midazolam of 0.2 mg/kg was given in immediate postoperative period upon hemodynamic stabilization. The determinations were performed prior to administration of the drug, at 5, 15, and 30 minutes thereafter. The variables analyzed were mean systemic blood pressure, mean diastolic pressure in aorta, mean pressure in the left auriculum, diastolic-systolic time relation, arterial blood O2 content and index of endocardiac viability.

Results: The following variables were modified with respect to the basal contributing to an improvement in the endocardiac viability index. Mean aortic diastolic pressure decreased 10.05% at 5 min and 6.17% at 15 min (p < 0.05, p < 0.005); mean systemic arterial pressure decreased 10.64% at 5 min and 6.9% at 15 min (p < 0.05, p < 0.005); the mean pressure in the left auriculum decreased 6.28% at 5 and 8.32% at 15 min (p < 0.05); the diastolic-systolic time relation increased 24.04% at 5 min (p < 0.05, p < 0.005). The index of delivery and consumption of endocardiac oxygen increased 23.4% at 5 min (p < 0.05).

Conclusions: The intravenous administration of midazolam to children at doses of 0.2 mg/kg during the postoperative period of cardiac surgery produced an improvement in the delivery and consumption of oxygen to endocardium at 5 minutes of its administration.