Effects of hypertonic saline on regional function and blood flow in canine hearts during acute coronary occlusion

Small-volume resuscitation using hypertonic saline (7.5%) is effective for various types of shock. Recently, hypertonic saline has been proposed for fluid management in patients with impaired cardiovascular function. Whether hypertonic saline is safe in the compromised heart during coronary occlusion is not known. We examined the effects of hypertonic saline at 4 mL · kg^-1 on myocardial function and blood flow during acute coronary occlusion. In anesthetized dogs, the left ventricle (LV) was instrumented with pressure and ultrasonic dimension transducers. Myocardial contractility was assessed using percent of systolic shortenings measured in both normal or ischemic regions. Blood flow distribution was measured using radioactive microspheres. Percent of systolic shortening and blood flow in the normal myocardium, unaltered by coronary occlusion, increased significantly after hypertonic saline from 11.0 ± 1.1% to 13.7 ± 1.4% and from 120 ± 13 mL · min^-1 ·100 g^-1 to 169 ±13 mL · min^-1 · 100 g^-1, respectively. In the ischemic myocardium, occlusion of the left anterior descending coronary artery markedly decreased percent of systolic shortening from 13.0 ± 1.2% to 9.3 ± .9% and blood flow from 98 ± 13 mL · min^-1 · 100 g^-1 to 19 ±10 mL · min^-1 · 100 g^-1. At peak effect of hypertonic saline contractility and blood flow in the ischemic myocardium decreased to 7.4 ± .8% and 12 ± 5 mL · min^-1 · 100 g^-1, respectively. Five of the nine dogs developed premature ventricular beats during hypertonic saline infusion. However, no significant changes were observed when normal saline was given at equivalent volumes to hypertonic saline in six dogs. Hypertonic saline was associated with significant increases in heart rate (from 116 ± 3 beats · min^-1 to 129 ± 5 beats · min^-1)and cardiac output (from 2.54 ± .17 L · min^-1 to 3.32 ± .26 L · min^-1). Except for an improved perfusion in the skin, hepatic arterial, and coronary beds, blood flow to the muscle, spleen, jejunum, kidney, and brain was not significantly altered by hypertonic saline. Our data demonstrates variant effects of hypertonic saline on either normal or ischemic myocardium. Whereas contractile function and blood flow in the normal myocardium were improved after hypertonic saline infusion, further decreases in blood flow and contractile function in region distal to coronary occlusion could lead to worsening of ischemic injury. These data suggest that hypertonic saline may be deleterious in hearts with impaired contractile function caused by ischemia.