Intravenous nitrogly-cerin administration during infrarenal aortic clamping

Twenty-five patients requiring infrarenal abdominal aortic clamping were studied during halothane, nitrous oxide anaesthesia. Aortic clamping caused reductions in cardiac index (CI), stroke volume index (SVI) and left ventricular stroke work index (LVSWI). Systemic vascular resistance (SVR) increased. In seven patients CI was less than 1.8 l·min^-1m^-2. Intravenous administration of nitroglycerin, 1μg·kg^-1min^-1, for 20 minutes, accompanied by volume loading to maintain pulmonary capillary wedge pressure, resulted in a significant improvement in haemodynamic parameters. CI increased 24 per cent as a result of a 14 per cent increase in SVI and an eight per cent increase in heart rate, LVSWI increased 13 per cent and SVR decreased 21 per cent. The plasma nitroglycerin concentration at the time of these measurements was 2.9 ± 1.0ng·ml^-1, Aortic unclamping resulted in a mean maximum decrease of 14 ± 2 torr mean arterial pressure. Epinephrine, norepinephrine and plasma renin activity gradually increased during the period of the anaesthetic.