Abstract P197: The Induction of Mild Hypothermia Preserves Myocardial Contractility After Ventricular Fibrillation/Resuscitation in Pigs
The induction of mild hypothermia (MH) in patients with depressed cardiac function is discussed controversially due to a concomitant reduction of cardiac output (CO). In 16 anaesthetized pigs (64±2 kg), ventricular fibrillation (VF, 5 min) was induced electrically. After resuscitation and return of spontaneous circulation (ROSC), pigs were assigned to normothermia (NT, 38°C, n =8) or MH (33°C, n =8, intravascular cooling device). Data are reported at 6h after ROSC vs control. Heart rate (HR, bpm) was unchanged in NT (86±6 vs 90±3) but lower in MH (59±4 vs 86±6, p<0.05). LV maximum pressure decreased in both groups. CO (l/min) decreased in MH (3.5±0.2 vs 5.5±0.4, p<0.05), but not in NT (4.8±0.4 vs 5.7±0.4, p=NS). However, mixed venous oxygen saturation (%) decreased in NT (56±2 vs 66±3, p<0.05), but not in MH (64±2 vs 65±2), due to lowered whole body oxgen consumption (WB-VO2, ml/min) in MH (184±11 vs 282±24, p<0.05), but not in NT (268±16 vs 264±14). LV dP/dtmax (mmHg/sec) was decreased in NT (1163±97 vs 1665±134, p<0.05) but preserved in MH (1602±102 vs 1603±96). From end-systolic pressure-volume relationships (aortic balloon catheter inflation), the end-systolic volume corresponding to an end-systolic pressure of 100 mmHg (LVV-Pes100, ml) was calculated. LVV-Pes100 increased in NT (69±9 vs 53±8, p<0.05) but not in MH (52±6 vs 56±4, p<0.05 vs NT). At control HR (right atrial pacing) in MH, LVV-Pes100 decreased further (40±5, p<0.05 vs ROSC 6h), but diastolic filling deteriorated. During MH, a lower CO is balanced by a lower WB-VO2. MH after cardiac arrest is a positive inotrope rather than an additional risk for the resuscitated heart.