Continuous Chest Compressions During Sustained Inflations in a Perinatal Asphyxial Cardiac Arrest Lamb Model

Abstract

Objective Continuous chest compressions (CCCs) are more effective during resuscitation in adults. Sustained inflation (SI) rapidly establishes functional residual capacity in fluid-filled lungs at birth. We sought to compare the hemodynamics and success in achieving return of spontaneous circulation (ROSC) in an asphyxial cardiac arrest lamb model with transitioning fetal circulation and fluid-filled lungs between subjects receiving CCCs during SI and those receiving conventional 3:1 compression-to-ventilation resuscitation. Design Prospective, randomized, animal model study. Setting An experimental laboratory. Subjects Fourteen newborn term gestation lambs. Interventions Lambs were randomized into two groups: 3:1 compression-to-ventilation (control) and CCCs during SI (SI+CCCs). The umbilical cord was occluded to induce asphyxia and asystole. The control group was resuscitated per NRP guidelines. In the SI+CCCs group, SI at 35cm H2O was provided for 30 seconds with 1-second interruptions before another SI was provided. 120 chest compressions/min started after the initial SI. The first dose of IV epinephrine was given at 6 minutes if ROSC was not achieved, and then every 3 minutes until ROSC or for a total of four doses. Measurement and Results All lambs achieved ROSC in a comparable median time (interquartile range) of 390 (225–405) and 345 (204–465) seconds in the SI+CCCs and control groups, respectively. 4/7 (SI+CCCs) and 3/6 (control) lambs required epinephrine to achieve ROSC. Diastolic blood pressures were lower in the SI+CCCs (4 ± 2 mmHg) compared to the control group (7 ± 2 mmHg); P<0.05. PaCO2, PaO2, and lactate were similar between the groups during the study period. Conclusion In this perinatal cardiac arrest lamb model with transitioning fetal circulation and fluid-filled lungs, SI+CCC is as effective as 3:1 C:V resuscitation in achieving ROSC. Half the lambs achieved ROSC without epinephrine. CCCs during SI reduced diastolic pressures but did not alter gas exchange or carotid blood flow compared to 3:1 C:V resuscitation.

Chest Compression in Neonatal Cardiac Arrest: Cerebral Blood Flow Measurements in Experimental Models

“…Combining CC with SI (n = 7) did not improve recovery in lambs compared to 3:1 C:V CPR (n = 6) [41]. The main difference between the piglets and lambs were that the pigs were post-transitional, whereas the lambs were examined during cardiopulmonary transition.…”

“…In asphyxiated piglets and lambs, different CC approaches have been investigated as alternatives to the standard 3:1 C:V ratio including different C:V ratios 2:1 [33], 4:1 [33], 9:3 [34], and 15:2 [35], continuous CC with asynchronous ventilations (CCaV) [36,37] at different CC rates (90/min, 100/min and 120/min) [38], and continuous CC with sustained inflation (SI) [39][40][41] at different CC rates [42] and SI duration [43].…”

Comparison of Different Compression to Ventilation Ratios (2: 1, 3: 1, and 4: 1) during Cardiopulmonary Resuscitation in a Porcine Model of Neonatal Asphyxia

“…These studies suggest that during neonatal CPR, different C:V ratios do not improve outcomes and might not be the optimal CC approach in newborn infants. In comparison with the recommended 3: 1 C:V, combining CC with sustained inflation has been shown to be more effective in improving ROSC in piglets [15, 22-24], but not in lambs [25]. …”

Ventilation Strategies during Neonatal Cardiopulmonary Resuscitation

“…However, the study by Schmölzer et al used a CC rate of 120/min (in the CC + SI group), which is higher than the currently recommended CC rate of 90/min, which could have also added to the improved outcomes. A recent study using a perinatal cardiac arrest lamb model with transitioning fetal circulation and fluid filled lungs reported that CC + SI is as effective as 3:1 C:V ratio in achieving ROSC ( 27 ).…”