Mild therapeutic hypothermia is superior to controlled normothermia for the maintenance of blood pressure and cerebral oxygenation, prevention of organ damage and suppression of oxidative stress after cardiac arrest in a porcine model.

BACKGROUND: Mild therapeutic hypothermia (HT) has been implemented in the management of post cardiac arrest (CA) syndrome after the publication of clinical trials comparing HT with common practice (ie, usually hyperthermia). Current evidence on the comparison between therapeutic HT and controlled normothermia (NT) in CA survivors, however, remains insufficient. METHODS: Eight female swine (sus scrofa domestica; body weight 45 kg) were randomly assigned to receive either mild therapeutic HT or controlled NT, with four animals per group. Veno-arterial extracorporeal membrane oxygenation (ECMO) was established and at minimal ECMO flow (0.5 L/min) ventricular fibrillation was induced by rapid ventricular pacing. After 20 min of CA, circulation was restored by increasing the ECMO flow to 4.5 L/min; 90 min of reperfusion followed. Target core temperatures (HT: 33°C; NT: 36.8°C) were maintained using the heat exchanger on the oxygenator. Invasive blood pressure was measured in the aortic arch, and cerebral oxygenation was assessed using near-infrared spectroscopy. After 60 min of reperfusion, up to three defibrillation attempts were performed. After 90 min of reperfusion, blood samples were drawn for the measurement of troponin I (TnI), myoglobin (MGB), creatine-phosphokinase (CPK), alanin-aminotransferase (ALT), neuron-specific enolase (NSE) and cystatin C (CysC) levels. Reactive oxygen metabolite (ROM) levels and biological antioxidant potential (BAP) were also measured. RESULTS: Significantly higher blood pressure and cerebral oxygenation values were observed in the HT group (P<0.05). Sinus rhythm was restored in all of the HT animals and in one from the NT group. The levels of TnI, MGB, CPK, ALT, and ROM were significantly lower in the HT group (P<0.05); levels of NSE, CysC, and BAP were comparable in both groups. CONCLUSIONS: Our results from animal model of cardiac arrest indicate that HT may be superior to NT for the maintenance of blood pressure, cerebral oxygenation, organ protection and oxidative stress suppression following CA.

Direct comparison of percutaneous circulatory support systems in specific hemodynamic conditions in a porcine model.

BACKGROUND: Several percutaneous circulatory support systems have been recently introduced into clinical practice for the treatment of cardiogenic shock or refractory nontolerated ventricular tachycardia, in support of high-risk catheter interventions and, occasionally, cardiopulmonary resuscitation. To date, however, a direct comparison of the available systems has not been performed. METHODS AND RESULTS: Adult female pigs (weight 50-60 kg) were used throughout the experiment. Under deep anesthesia and mechanical ventilation, 3 percutaneous circulatory support systems were compared: (1) right atrium-aorta, extracorporeal membrane oxygenation (n=4); (2) left atrium-aorta, TandemHeart system (n=4); (3) left ventricle-aorta, Impella 2.5 system (n=4), and (4) left ventricle-aorta with norepinephrine at 0.1 µg/kg per minute (n=4). Hemodynamic efficacy (mean arterial pressure) was measured at 3 specific conditions: ventricular pacing at 200 and 300 beats per minute, and ventricular fibrillation. Although no or only nonsignificant differences were found among the systems at ventricular pacing of 200 and 300 beats per minute, under ventricular fibrillation, the right atrium-aorta system was significantly the most efficacious, followed by the left atrium-aorta system and the left ventricle-aorta system (P<0.001). However, the left ventricle-aorta system with norepinephrine still maintained mean arterial pressure comparable with the left atrium-aorta system. CONCLUSIONS: Differences were seen in the hemodynamic efficacy of available percutaneous circulatory support systems, particularly under the most severe hemodynamic condition, ventricular fibrillation.