Haemodynamic effects of midazolam in the anaesthetized patient with coronary artery disease

The haemodynamic effects of midazolam 0.25 mg/kg administered intravenously were studied in eight anaesthetized patients suffering from coronary artery disease. Heart rate, systemic and pulmonary pressures, right atrial pressure, capillary pressure and cardiac output were measured 2, 5, 8 and 12 min after injection of midazolam and were compared with reference values collected before the commencement of the haemodynamic test. The cardiovascular condition of all the patients followed the same course after the injection of midazolam. The greatest variations were seen at the twelfth minute, with the exception of capillary pressure where the largest decrease was noted at the eighth minute. These variations, expressed as a percentage of the initial values, were: mean arterial pressure -17% (P less than 0.01); capillary pressure -23.5% (eight minute, P less than 0.01); heart rate - 9% (P less than 0.01); cardiac index -9% (P less than 0.01); systemic vascular resistance -12% (eighth minute, P less than 0.01). The stroke volume was well maintained (+0.1% NS). These haemodynamic variations were accompanied by a favourable evolution of the endocardial viability ratio (EVR), +12% (P less than 0.01). The slight tachycardia occasionally seen on induction of anaesthesia with midazolam was not seen in this group of patients. We conclude that these haemodynamic variations leading to an increase in EVR support the use of midazolam as a supplement to fentanyl anaesthesia for patients with coronary artery disease.