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 prop osed for fluid management in patients with impaired cardiovascular fun ction. Whether hypertonic saline is safe in the compromised heart duri ng coronary occlusion is not known. We examined the effects of hyperto nic saline at 4 mL.kg(-1) on myocardial function and blood flow during acute coronary occlusion. In anesthetized dogs, the left ventricle (L V) was instrumented with;pressure and ultrasonic dimension transducers . Myocardial contractility was assessed using percent of systolic shor tenings measured in both normal or ischemic regions. Blood flow distri bution was measured using radioactive microspheres. Percent of systoli c shortening and blood flow in the normal myocardium, unaltered by cor onary 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 isc hemic myocardium, occlusion of the left anterior descending coronary a rtery 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 hypertoni c saline contractility and blood flow in the ischemic myocardium decre ased to 7.4 +/- .8% and 12 +/- 5 mL . min(-1) . 100 g(-1), respectivel y. Five of the nine dogs developed premature ventricular beats during hypertonic saline infusion. However, no significant changes were obser ved when normal saline was given at equivalent volumes to hypertonic s aline in six dogs. Hypertonic saline was associated with significant i ncreases in heart rate (from 116 +/- 3 beats . min(-1) to 129 +/- 5 be ats . min(-1))and cardiac output (from 2.54 +/- .17 L . min(-1) to 3.3 2 +/- .26 L min(-1)). Except for an improved perfusion in the skin, he patic arterial, and coronary beds, blood flow to the muscle, spleen, j ejunum, 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 sa line infusion, further decreases in blood flow and contractile functio n in region distal to coronary occlusion could lead to worsening of is chemic injury. These data suggest that hypertonic saline may be delete rious in hearts with impaired contractile function caused by ischemia.