Comparative hemodynamic responses to chlorpromazine, nitroprusside, nitroglycerin, and trimethaphan immediately after open heart operations

The hemodynamic effects of intravenous chlorpromazine, nitroprusside, nitroglycerin, and trimethaphan camsylate were studied in 51 patients with high mean arterial pressures immediately after open heart operations. Chlorpromazine was given by bolus intravenous injection to 24 patients (average dose 10.3 mg); nitroprusside (17 patients), nitroglycerin (8 patients), and trimethaphan (12 patients) were administered by constant intravenous infusion at average doses of 77 μg/min, 59 μg/min, and 0.97 mg/min, respectively. Measured or derived variables included right atrial pressure, pulmonary artery pressure, left atrial pressure, systemic arterial pressure, heart rate (HR), cardiac index (CI), stroke index (SI), stroke work index (SWI), and systemic vascular resistance index (SVRI). All four vasodilators significantly reduced systemic and intracardiac pressures and SWI (P < 0.01). Associated changes in left ventricular pumping performance, however, differed importantly between groups. Chlorpromazine caused a significant rise (+ 19%) in HR with preservation of SI; thus, CI rose significantly (P < 0.01). Only nitroprusside, however, resulted in enhancement of SI (P < 0.05) at the lowered left atrial pressure; CI increased by 19% (P < 0.01), HR rose minimally (6.5%), and calculated SVRI diminished 33% (P < 0.01). Both nitroglycerin and trimethaphan caused decreases in SI and CI. These results indicate that in general, among the vasodilators studied, nitroprusside is associated with the most favorable hemodynamic responses in early postoperative cardiac surgical patients.