Introduction: It is recommended that bystanders witnessing the sudden collapse of an individual should provide cardiopulmonary resuscitation (CPR) whilst waiting for the emergency medical services. As the presence of pulse might not be assessed correctly, it is possible that a bystander might perform CPR on a beating heart. Although potentially important to the patient’s outcome, the hemodynamic changes caused by performing CPR on a beating heart have not been extensively investigated.
Hypothesis: Aim of this study is to investigate changes in mean arterial blood pressure (AOP) following CPR in animals with a beating heart.
Methods: Prospective laboratory investigation using an established porcine model with instrumentation for measurement of hemodynamic variables, vital organ blood flow and blood gases. Animals (n=5) were anesthetized and mechanically ventilated on a mixture of room air and titrated isoflurane (≈1.0% to 2.5%). CPR at 30:2 compressions over breaths was performed for 2 minutes followed by 1 minute hands off. This procedure was repeated 4 times for each animal. A 10 minutes hands off period followed the last CPR cycle.
Results: Mean AOP was measured at baseline, after each CPR cycle (CPR1, CPR2, CPR3 and CPR4) and 10 minutes after the last CPR cycle. Analysis of variance (ANOVA) was conducted for the different time points (Figure 1). Post hoc analysis (one-tailed t-test) comparing baseline mean AOP (75.20±3.03 mmHg ) and mean AOP after each CPR cycle shows a nominal p < 0.05 for CPR3, CPR4 and 10 min after CPR. Following the fourth CPR cycle mean AOP (92.25±11.41 mmHg, p = 0.0273) was elevated in all animals. Mean AOP persisted at a higher level than the baseline mean AOP even after the 10 minutes hands off period (mean AOP = 86.50±7.32, p = 0.0234).
Conclusions: In this animal model, performing CPR on a beating heart altered mean AOP, resulting in an increase in mean AOP that would persist even after 10 minutes of hands off period.