Effects of Left Ventricular Versus Traditional Chest Compressions in a Traumatic Pulseless Electrical Activity Model.

BACKGROUND: Prehospital cardiopulmonary resuscitation has commonly been considered ineffective in traumatic cardiopulmonary arrest because traditional chest compressions do not produce substantial cardiac output. However, recent evidence suggests that chest compressions located over the left ventricle (LV) produce greater hemodynamics when compared to traditional compressions. We hypothesized that chest compressions located directly over the LV would result in an increase in return of spontaneous circulation (ROSC) and hemodynamic variables, when compared to traditional chest compressions, in a swine model of traumatic pulseless electrical activity (PEA). METHODS: Transthoracic echocardiography was used to mark the location of the aortic root (traditional compressions) and the center of the LV on animals (n = 34) that were randomized to receive chest compressions in one of the two locations. Animals were hemorrhaged to mean arterial pressure <20 to simulate traumatic PEA. After 5 minutes of PEA, basic life support (BLS) with mechanical cardiopulmonary resuscitation was initiated and performed for 10 minutes followed by advanced life support for an additional 10 minutes. Hemodynamic variables were averaged over the final 2 minutes of BLS and advanced life support periods. RESULTS: Six of the LV group (35%) achieved ROSC compared to eight of the traditional group (47%) (P = .73). There was an increase in aortic systolic blood pressure (P < .01), right atrial systolic blood pressure (P < .01), and right atrial diastolic blood pressure (P = .02) at the end of BLS in the LV group compared to the traditional group. CONCLUSIONS: In our swine model of traumatic PEA, chest compressions performed directly over the LV improved blood pressures during BLS but not ROSC.

A Traumatic Pulseless Electrical Activity Model: Mortality Increases With Hypovolemia Time.

BACKGROUND: There currently are no well-defined animal models for traumatic pulseless electrical activity (PEA). Our objective was to develop a swine model of traumatic PEA that would be useful for laboratory research where mortality is an outcome of interest. In this pilot study, we hypothesized that animals that remained in PEA without intervention for a longer period would have increased mortality. MATERIALS AND METHODS: Sixteen Yorkshire swine were alternately allocated to either 5 or 10 min of traumatic PEA without intervention. After the nonintervention period, basic life support (BLS) with mechanical cardiopulmonary resuscitation was initiated and performed for 10 min followed by advanced life support (ALS) for an additional 10 min. Hemodynamic and laboratory values are reported for baseline, posthemorrhage, end of BLS, and end of ALS periods. RESULTS: Mortality in the 10-min PEA group (100%) was higher than the 5-min group (38%) (P = 0.03). Animals in the 5-min group had improved aortic diastolic blood pressure, coronary perfusion pressure, and end-tidal CO2 at the end of both the BLS (P = 0.02, 0.002, and 0.02, respectively) and ALS (P = 0.009, 0.005, and 0.008, respectively). The 10-min animals had increased hyperkalemia at the end of the BLS (P = 0.004) and ALS (P = 0.005) periods. All animals in the 10-min group developed ventricular fibrillation (VF) and 38% of the 5-min animals developed VF (P = 0.03). CONCLUSIONS: In our pilot study of traumatic PEA in a swine model, a shorter period of nonintervention resulted in increased survival, improved hemodynamics during resuscitation, decreased hyperkalemia, and less incidence of conversion to VF arrest.