Effect of 7.2% hypertonic saline/6% hetastarch on left ventricular contractility in anesthetized humans

Abstract

Background: Although a positive inotropic effect of hypertonic saline has been demonstrated in isolated cardiac tissue as well as in animal preparations, no information exists about a possible positive inotropic action of hypertonic saline in humans. The aim of this investigation was to determine whether a clinically relevant positive inotropic effect can be demonstrated in humans. Methods: Twenty-six patients without cardiovascular disease were randomized to receive 4 ml/kg of either 7.2% hypertonic saline/6% hetastarch or 6% hetastarch (control) at a rate of 1 ml · kg-1 · min-1 while under general endotracheal anesthesia. Transesophageal echocardiography was used to evaluate left ventricular function. Arterial pressure, heart rate, and left ventricular end-systolic and end-diastolic diameter, area, and wall thickness were measured immediately before and after administration of either solution. Fractional area change, end-systolic wall stress, and the area under the end-systolic pressure-length relationship curve (ESPLR(area)) were calculated. ESPLR(area) was used to assess left ventricular contractility. Results: Administration of hypertonic saline/hetastarch resulted in a significant decrease of mean arterial pressure and end-systolic wall stress from 77 ± 14 (mean ± SD) to 64 ± 17 mmHg (P < 0.01) and from 52 ± 14 to 32 ± 11 103 dyne/cm2 (P > 0.01), respectively. End-diastolic area and fractional area change increased from 16.5 ± 2.9 to 21.7 ± 3-3 cm2 (P < 0.01) and from 0.53 ± 0.07 to 0.70 ± 0.06 (P < 0.01), respectively, whereas there was only a minor change of ESPLP(area) from 38 ± 13 to 44 ± 13 mmHg · cm (P<0.05). Conclusions: The apparent improvement of left ventricular systolic function in response to hypertonic saline/hetastarch is caused mainly by the combined effect of increased left ventricular preload and reduced left ventricular afterload. A possible positive inotropic action of hypertonic saline/hetastarch is not likely to be clinically relevant.