Effect of chest compressions in addition to extracorporeal life support on carotid flow in an experimental model of refractory cardiac arrest in pigs.

Background: Extracorporeal life support (ECLS) provides organ perfusion in refractory cardiac arrest but during the initiation of ECLS mean arterial pressure (MAP) and carotid flow may be suboptimal due to hypotension and/or insufficient flow. We hypothesized that cardiopulmonary resuscitation (CPR) in addition to ECLS may increase carotid flow and MAP compared to ECLS alone.

Methods: Observational pilot study comparing hemodynamic parameters before and after CPR cessation in pigs supported by ECLS for experimental refractory cardiac arrest. Pigs were anesthetized, ventricular fibrillation was induced for 3 min, automated CPR performed for 30 min, ECLS was initiated then CPR stopped.Variables averaged over 3 s were compared between the last 3 s of CPR + ECLS and 3, 6, 30 s, and 5 and 10 min of ECLS alone. Data are expressed as medians (25-75 interquartile range) and compared using paired samples Wilcoxon test.

Results: Nine pigs were included, ECLS was initiated at 2.7 (2.3-2.8) L/min. MAP during CPR + ECLS was 56(53.0-59.2) mmHg, 50(45-57)mmHg, 52(46-59)mmHg, 61(50-63)mmHg, 57 (54-66)mmHg, 54 (47-58)mmHg of ECLS alone, p = 0.50, 0.61, 0.70, 0.44, 0.73 respectively. Carotid flow was 113(78-119) ml/min during CPR + ECLS 99(79-110)ml/min, 100(81-110)ml/min, 96(60-122)ml/min, 118 (101-130)ml/min, 124 (110-141)ml/min, p = 0.41, 0.52, 0.73, 0.33, 0.20 respectively. When ECLS was initiated at lower flow, 1.5 L/min (one pig), MAP decreased from 59 to 45 mmHg, and carotid flow from 78.2 to 32.5 ml/min after 3 s of ECLS alone.

Conclusion: Stopping CPR after effective ECLS initiation does not decrease MAP or carotid flow. Future studies may evaluate augmenting low flow ECLS with CPR.