Insulin improves heart function and metabolism during non-ischemic cardiogenic shock in awake canines

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Abstract
Objectives: This study was undertaken to examine in-situ heart function and metabolism during insulin treatment of verapamil-induced cardiogenic shock in awake canines. Methods: Twenty mongrel canines were instrumented to monitor myocardial substrate uptakes (glucose, lactate, free fatty acids, oxygen [MVO2]), as well as left ventricular (LV) end-systolic elastance (Emax), LV efficiency (LV minute work/MVO2), and Tau. Shock was induced by graded intraportal verapamil infusion followed by randomized assignment to one of 4 treatment groups: saline control (3.0 ml/kg/min, n=5), epinephrine (5 μg/kg/min, n=5), glucagon (10 μg/kg/min, n=5) or insulin (1000 mU/min, n=5) with dextrose to clamp arterial [glucose] ±10% of basal concentrations. Results: Insulin treatment significantly increased Emax (34±3 vs. 17±3 mmHg/mm, saline control), and shortened Tau (9±3 ms) compared to saline control (42±5 ms), epinephrine (20±4 ms) and glucagon (35±8 ms). With insulin treatment, mechanical efficiency increased to 20 097±2070 vs. 12 424±1615 mmHg·mm/ml O2/100 g in controls. Simultaneously, insulin increased myocardial lactate uptake (35±2 vs. 17±4 μmol/min/100 g, saline control), but did not increase glucose uptake. Epinephrine and glucagon decreased mechanical efficiency compared to saline controls, coincident with increased myocardial fatty acid consumption, but without increasing lactate uptake. One dog died early with glucagon treatment before the first death in the saline-treated group. Conclusions: Insulin improves systolic and diastolic heart function during aerobic shock and accelerates in-vivo myocardial lactate oxidation.

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