P0717 - Continuous Chest Compressions with Asynchronous Ventilations Increase Cerebral Blood Flow and Oxygen Delivery in the Perinatal Asphyxiated Cardiac Arrest Lamb Model

Purpose:
In newborns with persistent bradycardia (heart rate <60/min) despite effective ventilation, interrupted chest compressions ([CC] 3:1 compression-to-ventilation – C:V ratio with a pause during ventilation; 90 CC/min and 30 breaths/min) are recommended. In neonates, heart rate is the primary determinant of cardiac output and achieving a higher rate of CC (e.g. continuous CC at 120 CC/min and asynchronous ventilations at 30/min) may increase blood flow to essential organs.

We hypothesize that continuous CC with asynchronous ventilations (CCCaV) leads to quicker ROSC and better hemodynamics compared to the current recommended interrupted 3:1 C:V resuscitation.

Methods:
22 near-term fetal lambs (~140/147d) were partially exteriorized, intubated and instrumented. Lambs were randomized to interrupted 3:1 C:V or CCCaV. Asphyxiation to cardiac arrest (asystole) was induced by cord occlusion. After five min of asystole, positive pressure ventilation (PPV) was provided by a T-piece resuscitator. CC was started after 30s with PPV with 100%O2. The first dose of epinephrine (EPI) was given at 6 min if return of spontaneous circulation (ROSC) was not achieved and repeated q3 min until ROSC (or max of 4 doses). Invasive arterial blood pressure and left carotid blood flow were continuously measured. Arterial blood gases were collected at defined time-points during the study period.

Results:
There were no differences in baseline characteristics between groups (Table 1). Rate of ROSC was similar in both groups at 91%, as was time to ROSC (5.5 ±2.3 vs. 5.7 ±1.5 min in the 3:1 C:V compared to the CCCaV group, respectively). Lambs that received CCCaV had significantly greater left carotid blood flow compared to 3:1 C:V (7.5 ±3.1 vs. 4.3 ±2.6 ml/kg/min, p <0.01; Fig). During CC, PaO2 and left carotid oxygen delivery were significantly greater with CCaV compared to 3:1 C:V (0.4 ±0.15 vs. 0.13 ±0.07 mL O2/kg/min, p <0.01; Table 2). There was no difference in systolic, diastolic and mean blood pressure between the groups.

Conclusions:
In a perinatal asphyxiated cardiac arrest lamb model, CCCaV showed greater carotid blood flow and oxygen delivery to the brain compared to the conventional 3:1 C:V resuscitation. No difference between groups was observed in the time to ROSC, the rate of ROSC or the number of EPI doses administered. Clinical studies assessing the survival and neurodevelopmental outcomes comparing CCCaV to 3:1 C:V during newborn resuscitation are warranted.