Effect of repeated episodes of ventricular fibrillation and defibrillation on arterial acid-base and electrolytes changes in a swine model / 中华急诊医学杂志

ABSTRACT

Objective:To investigate changes in arterial acid-base and electrolytes after repeated episodes of ventricular fibrillation (VF) and defibrillation in a swine model.Methods:Sixteen Peking white swine, weighting (32±2.5) kg, were placed with temporary pacemaker electrodes via the left femoral vein into the right ventricle after anesthesia. Then VF was electrically induced by using a programmed electrical stimulation instrument. An arterial cannula was inserted into the left femoral artery to measure mean arterial blood pressure and cardiac output using a PiCCO monitor, with blood samples collected. The pigs were randomly divided into two group: the manual defibrillation group (MD, n=8) and the automated external defibrillation group (AED, n=8). The first defibrillation was attempted with the manufacturer’s dose (150 J) for 15 s after the successful induction of VF in the MD group. If spontaneous circulation was not recovered, 2-min chest compression and subsequent defibrillation (200 J) were attempted. For the AED group, the defibrillation was delivered following voice prompts of the AED. After the return of spontaneous circulation, the pig was allowed to stabilize for 30 min, followed by the induction of the next episode of VF. The above process was repeated five times. Arterial blood gas, cardiac biomarkers, and hemodynamic variables were measured at 30 min after the return of spontaneous circulation. Results:All pigs were successfully induced VF five times and defibrillated successfully. There were no significant changes in heart rate and mean arterial blood pressure between the two groups after repeated episodes of VF and defibrillation. Compared with baseline measurements, cardiac output tended to decrease after repeated episodes of VF and defibrillation but was not statistically significant (all P>0.05). There were no significant differences in arterial pH, HCO 3-, sodium, and lactic acid in the two groups between each measurement time point and baseline values after repeated VF (all P>0.05), but potassium levels in the two groups decreased with time, and the difference was statistically significant compared with the baseline measurement (all P<0.05). There were no significant differences in myoglobin, creatine kinase isoenzyme-MB, and cardiac troponin I for the two groups compared with baseline values after repeated episodes of VF and defibrillation or various episodes of VF between the two groups (all P > 0.05). Conclusions:Repeated episodes of VF and defibrillation have no significant effect on pH balance, but significantly decrease blood potassium. Clinical approaches (MD vs. AED) do not affect defibrillation effect, with no significant differences in hemodynamic variables and myocardial injuries.