Abstract 257: The Induction of Mild Hypothermia Improves Myocardial β-Adrenergic Responsiveness During Endotoxemia in Pigs
Background: Mild hypothermia (MH) exerts anti-inflammatory effects in experimental settings. We tested the effect of MH on myocardial ß-adrenergic responsiveness during experimental endotoxemia.
Methods: Anesthetized pigs (65±2 kg) were acutely instrumented (closed chest) with a series of catheters including a Swan-Ganz catheter, a left ventricular (LV) pressure-volume catheter, an intraaortic balloon catheter and an intravascular cooling device. Endotoxemia, a model of septic shock, was induced by lipopolysaccharid (LPS) infusion at 0.5 µg/kg/h for 1 hour and 1 µg/kg/h for further 3 hours. With the beginning of LPS infusion, pigs were assigned to either normothermia (NT, 38 °C, n=7) or MH (33 °C, n=6). Animals were followed for a total of 8 hours. After sacrifice, ventricular muscle strips were isolated, stretched to optimal length in Tyrode solution containing 2,5 mmol calcium, stimulated at 1 Hz and exposed to increasing concentrations of isoproterenol. All muscle strips were examined at 38 °C.
Results: In vivo, LV pressure-time (dP/dt) and pressure-volume analysis indicated a similar impairment of LV contractile parameters. In vitro, the increase of developed force in response to isoproterenol was higher in muscle strips isolated from hearts of the MH group than of the NT group. The logEC50% was not different between groups.
Conclusion: These data indicate that MH counteracts the loss of myocardial ß-adrenergic responsiveness typically associated with the development of sepsis. MH may be a therapeutic option for septic cardiomyopathy.
- © 2011 by American Heart Association, Inc.