Extended series of cardiac compressions during CPR in a swine model of perinatal asphyxia☆

Abstract 

Background

The rationale for a compression to ventilation ratio of 3:1 in neonates with primary hypoxic, hypercapnic cardiac arrest is to emphasize the importance of ventilation; however, there are no published studies testing this approach against alternative methods. An extended series of cardiac compressions offers the theoretical advantage of improving coronary perfusion pressures and hence, we aimed to explore the impact of compression cycles of two different durations.

Materials and methods

Newborn swine (n=32, age 12–36h, weight 2.0–2.7kg) were progressively asphyxiated until asystole occurred. Animals were randomized to receive compressions:ventilations 3:1 (n=16) or 9:3 (n=16). Return of spontaneous circulation (ROSC) was defined as a heart rate ≥100beatsmin⁻¹.

Results

All animals except one in the 9:3 group achieved ROSC. One animal in the 3:1 group suffered bradycardia at baseline, and was excluded, leaving us with 15 animals in each group surviving to completion of protocol. Time to ROSC (median and interquartile range) was 150s (115–180) vs. 148s (116–195) for 3:1 and 9:3, respectively (P=0.74). There were no differences in diastolic blood pressure during compression cycles or in markers of hypoxia and inflammation. The temporal changes in mean arterial blood pressure, heart rate, arterial blood gas parameters, and systemic and regional oxygen saturation were comparable between groups.

Conclusion

Neonatal pigs with asphyxia-induced cardiac arrest did not respond to a compression:ventilation ratio of 9:3 better than to 3:1. Future research should address if alternative compression:ventilation ratios offer advantages over the current gold standard of 3:1.

Abbreviations: ILCOR, International Liaison Committee on Resuscitation, CPR, Cardiopulmonary resuscitation, C:V ratio, Compression:ventilation ratio, CPP, Coronary perfusion pressure, ROSC, Return of spontaneous circulation, MAP, Mean arterial blood pressure, DBP, Diastolic blood pressure, HR, Heart rate, CSF, Cerebrospinal fluid, NIRS, Near Infrared Spectroscopy, rScO₂, Regional cerebral oxygen saturation, cFTOE, Cerebral fractional tissue oxygen extraction, BALF, Bronchoalveolar lavage fluid

Keywords: Asphyxia, Asystole, Cardiopulmonary resuscitation (CPR), Chest compression, Coronary perfusion pressure, Neonatal resuscitation, Return of spontaneous circulation