Catecholamine and renin-angiotensin response during hypotensive anesthesia induced by sodium nitroprusside or trimethaphan camsylate

Sodium nitroprusside and trimethaphan camsylate often are used to induce hypotension for a variety of surgical procedures. Both agents have a short duration of action that allows for minute-to-minute regulation of blood pressure with rapid restoration of normal pressure. Nitroprusside decreases vascular resistance by directly relaxing arteriolar and, to a lesser extent, venular smooth muscle. Trimethaphan primarily decreases vascular tone by blocking autonomic reflexes secondary to ganglionic blockade. Some direct vasodilatory activity is also present. In a previous report, we described hormonal and hemodynamic changes that occurred using pentoliniumtartrate-induced hypotension for the management of scoliosis surgery. In the present study, we compare the hormonal responses during nitroprusside- or trimethaphan-induced hypotension in a similar group of patients.