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

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Abstract

Objective:

Continuous chest compressions are more effective during resuscitation in adults. Sustained inflation 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 in an asphyxial cardiac arrest lamb model with transitioning fetal circulation and fluid-filled lungs between subjects receiving continuous chest compressions during sustained inflation 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 continuous chest compressions during sustained inflation. The umbilical cord was occluded to induce asphyxia and asystole. The control group was resuscitated per NRP guidelines. In the sustained inflation + continuous chest compressions group, sustained inflation at 35 cm H2O was provided for 30 seconds with 1-second interruptions before another sustained inflation was provided. One hundred twenty chest compressions/min started after the initial sustained inflation. The first dose of IV epinephrine was given at 6 minutes if return of spontaneous circulation was not achieved and then every 3 minutes until return of spontaneous circulation or for a total of four doses.

Measurement and Results:

All lambs achieved return of spontaneous circulation in a comparable median time (interquartile range) of 390 seconds (225–405 s) and 345 seconds (204–465 s) in the sustained inflation + continuous chest compressions and control groups, respectively. Four of seven (sustained inflation + continuous chest compressions) and three of six (control) lambs required epinephrine to achieve return of spontaneous circulation. Diastolic blood pressures were lower in the sustained inflation + continuous chest compressions (4 ± 2 mm Hg) compared to the control group (7 ± 2 mm Hg), 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, sustained inflation + continuous chest compressions is as effective as 3:1 compression-to-ventilation resuscitation in achieving return of spontaneous circulation. Half the lambs achieved return of spontaneous circulation without epinephrine. continuous chest compressions during sustained inflation reduced diastolic pressures but did not alter gas exchange or carotid blood flow compared to 3:1 compression-to-ventilation resuscitation.

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