Insulin treatment before resuscitation following hemorrhagic shock improves cardiac contractility and protects the myocardium in the isolated rat heart

BACKGROUND: Insulin has been shown to exert positive inotropic effects in several in vivo ex vivo models and in human hearts. Resuscitation following hemorrhagic shock results in myocardial contractile dysfunction. However, the optimal timing for treatment with insulin for the cardioprotection effects is unclear. OBJECTIVES: The objective of this study was to test the hypothesis that treatment with insulin before resuscitation provides better cardioprotection than treatment with insulin after resuscitation. MATERIALS AND METHODS: Rats were assigned to 3 experimental groups (n = 6 per group): (1) Hemorrhagic shock and resuscitation, (2) hemorrhagic shock resuscitated then treated with insulin and (3) hemorrhagic shock treated with insulin before resuscitation. Rats were hemorrhaged for 60 min to rach mean arterial blood pressure of 40 mmHg. Rats were resuscitated in vivo by reinfusion of the shedded blood to restore normotension and monitored for 60 min. Rats were treated or not with insulin 200 μU/g body weight intramuscularly either before or after resuscitation. The maximum of the left ventricular developed pressure (+dP/dt) was measured for 60 min in the isolated perfused hearts using the Langendorff method. Blood samples were obtained for measurements of tumor necrosis factor-alpha (TNF-α). RESULTS: Treatment with insulin before resuscitation following hemorrhagic shock significantly elevated max dP/dt compared with insulin treatment after resuscitation and the untreated group. TNF-α levels were lower in the insulin treatment before resuscitation compared to the treatment after resuscitation and the untreated group. CONCLUSION: Insulin treatment before resuscitation following hemorrhagic shock provides better cardiac protection than treatment with insulin after resuscitation, as evidenced by the improved myocardial contractility, preservation of myocardial structure. The mechanism of cardiac protection involves decrease in the inflammatory response to shock by lowering the levels of TNF.