Hormonal and hemodynamic changes induced by pentolinium and propranolol during surgical correction of scoliosis.

Abstract

Deliberate hypotension has had variable success in decreasing blood losses and facilitating extensive surgical procedures. In this study, hemodynamic variables, catecholamines, plasma renin activity, and angiotensin II levels were studied in 11 patients undergoing operative correction of idiopathic scoliosis. Deliberate hypotension with mean arterial blood pressures ranging from 55 to 42 torr was provided with the ganglionic blocking agent, pentolinium tartrate, supplemented by beta blockade with propranolol during morphine–nitrous oxide anesthesia. Stroke volume index, systemic vascular resistance, and left ventricular stroke work index decreased 16, 19, and 40 per cent, respectively, with blood pressure reduction. Following the return to normal blood pressure, stroke volume index increased to a value 28 per cent greater than control, while systemic vascular resistance remained decreased. At this time left ventricular stroke work index increased slightly, but the increase was not statistically significant compared with control. The epinephrine level had risen from 59 to 270 pg/ml an hour after hypotension, probably secondary to infiltration of the skin prior to the surgical procedure. It had decreased to control levels by the end of the procedure. Norepinephrine and dopamine concentrations and plasma renin activity were unchanged. The angiotensin II level was significantly decreased, from 60 to 40 pg/ml, during deliberate hypotension. Blood loss correlated with left ventricular stroke work index, while changes in systemic vascular resistance and heart rate correlated well with changes in angiotensin II and plasma renin activity, respectively. The ability of ganglionic blockade and propranolol to inhibit the increases in catecholamines and angiotensin II during morphine–nitrous oxide anesthesia, hypotension, and surgical intervention may be of considerable importance.