The effect of nitrous oxide on left ventricular pump performance and contractility in patients with coronary artery disease: effect of preoperative ejection fraction.

Abstract

To elucidate the effects of nitrous oxide (N2O) on left ventricular (LV) pump performance and contractility, 28 patients undergoing coronary artery bypass graft surgery were studied, of whom 15 had depressed global LV function at preoperative catheterization. Transesophageal echocardiography and simultaneous hemodynamic measurements were used to assess LV preload, afterload, and systolic performance during inhalation of 100% oxygen (O2) and 60% N2O:40% O2. Systolic function indices were expressed as a percent of the predicted value for observed end-systolic stress to provide estimates of LV contractility. In the entire study population, N2O reduced pump performance (cardiac index 2.4 +/- 0.8 to 2.2 +/- 0.6 L.min-1 x m-2; P < 0.02). Heart rate and mean arterial pressure were reduced (67 +/- 13 to 64 +/- 13, P < 0.01, and 87 +/- 9 to 80 +/- 15, P < 0.005) as were left and right ventricular stroke work index. Preload, as measured by end-diastolic stress, was unchanged but afterload, as measured by end-systolic stress, tended to decrease (88 +/- 31 to 78 +/- 28, P = 0.053). In the 13 patients with normal preoperative LV function, mean arterial pressure and LV stroke work index decreased significantly (91 +/- 8 to 84 +/- 14, P < 0.04, and 40 +/- 13 to 34 +/- 10, P < 0.04, respectively) and end-systolic stress tended to decrease (P = 0.054).(ABSTRACT TRUNCATED AT 250 WORDS)