Abstract P152: An Observational Study to Assess Changes in Arterial Blood Gas Values During Untreated Porcine Ventricular Fibrillation
Background: Cardiocerebral resuscitation (CCR) is reportedly superior to cardiopulmonary resuscitation (CPR) for out-of-hospital cardiac arrest (OHCA) even though active ventilation is not initially provided. Understandably, concerns have been raised regarding the withholding of positive pressure ventilation (PPV) during CCR because of the longstanding belief that respiratory gas exchange is a critical action during resuscitation. We sought to quantify the effect of untreated VF on the pH, pCO2, and pO2 values in a swine model of witnessed cardiac arrest to determine if these concerns might be warranted.
Methods: Both included studies were IACUC approved. Eighty-three animals (25–35kg) were instrumented under general anesthesia. Baseline characteristics were recorded. An arterial blood gas (ABG) was drawn from each animal via femoral catheter just prior to electrical induction of VF. After 8 minutes of untreated VF in one study [Study1 (n=30)] and 10 minutes of untreated VF in the other study [Study2 (n=53)], a second ABG was drawn. All samples were processed immediately using an iStat portable analyzer. Baseline characteristics of animals in the two studies were assessed using descriptive statistics. For the second ABG in each study, the mean pH, pCO2, and pO2 values, with 95% confidence intervals (95%CI), were determined. The paired ABG results for each animal were then compared and the average pH, pCO2, and pO2 proportions, with 95%CI, for each study were calculated.
Results: Baseline characteristics of animals in the two studies were similar. The table⇓ summarizes the absolute (ABS) and relative (REL) ABG values for the two studies, after 8 and 10 minutes of untreated VF, respectively.
Conclusions: These data would suggest that concerns over initially withholding PPV to focus on high quality chest compressions and expedited vasopressor delivery during initial resuscitation by EMS personnel after witnessed untreated VF are unfounded.