[Hemodynamic interaction between midazolam and alfentanil in coronary patients]

We studied the hemodynamic interaction between midazolam and alfentanil during induction of anaesthesia in 27 patients with coronary heart disease. Using alfentanil alone (93 +/- 6 micrograms/kg) the induction was associated with stable systemic haemodynamics but also with a pressure increase in pulmonary circulation, due to chest wall rigidity and respiratory acidosis. The administration of subhypnotic doses of midazolam (50 and 100 micrograms/kg) prior to alfentanil prevented chest wall rigidity and pulmonary vasoconstriction completely, suppressed the pressor response to intubation and reduced the dose of alfentanil required for induction. However the midazolam-alfentanil combination led to hypotension, which was primarily due to a decrease of peripheral systemic resistance. Thus the haemodynamic interaction between midazolam and alfentanil resembles the known interactions between other benzodiazepines and opiates, characterized by decreased sympathetic tone and suppressed baroreceptor reflex.