Midazolam versus diazepam: different effects on systemic vascular resistance. A randomized study utilizing cardiopulmonary bypass constant flow.

In 43 patients electively scheduled for myocardial revascularization surgery, a hemodynamic comparison of 8-chloro-6-(2-fluorophenyl)-1-methyl-4H-imidazo[1,5-a][1,4] benzodiazepine (midazolam, Ro 21-3981, Dormicum) and 7-chloro-1,3-dihydro-1-methyl-5-phenyl-(2H)1,4-benzodiazepin-2-one (diazepam) was made during cardiopulmonary bypass. Midazolam and diazepam were compared in patients with ischemic heart disease to determine the effects of the drugs on systemic vascular resistance at constant flow (cardiac output) and temperature. Diazepam (0.3 mg/kg) produced significantly greater decreases in perfusion pressure, systemic vascular resistance, and venous reservoir volume than did midazolam (0.2 mg/kg). It was concluded that there are subtle differences in the pharmacologic actions of both midazolam and diazepam. When used with constant flow on cardiopulmonary bypass, diazepam causes more pronounced arterial and venous dilation. These data are at variance with the findings in intact man.