Lorazepam and high-dose fentanyl anaesthesia: effects on haemodynamics and oxygen transportation in patients undergoing coronary revascularization

The effects of intravenous lorazepam (0.05 mg/kg) on haemodynamics and oxygen transportation were studied in a group of 11 patients undergoing a coronary artery bypass grafting operation with high-dose fentanyl anaesthesia and compared to the changes in another group of 11 patients receiving the same anaesthesia, but saline instead of lorazepam. The measurements were made under stable haemodynamic conditions before the injection of lorazepam or saline, and repeated 5, 20 and 40 min after the injection. Lorazepam caused a slight decrease in the systemic and pulmonary arterial pressures and in the left ventricular stroke work index, as compared to the control group. The ECG or the rate-pressure product did not show changes indicative of myocardial oxygen supply/demand imbalance in either group. There was a similar decrease in the systemic oxygen transportation and an increase in the arterio-venous oxygen content difference in both groups, but the unchanged systemic oxygen consumption and arterial lactate level suggest a well-maintained tissue oxygenation. It is concluded that intravenous lorazepam does not cause important haemodynamic untoward effects as an adjunct to high-dose fentanyl anaesthesia in patients undergoing coronary artery bypass grafting.