Survey of effects of anesthesia protocols on hemodynamic variables in porcine cardiopulmonary resuscitation laboratory models before induction of cardiac arrest

Objective: An advantage of animal models in cardiopulmonary resuscitation (CPR) research is the possibility to control confounding variables that may be impossible to standardize in clinical trials. A neglected effect of the anesthesia protocol in porcine CPR studies may be its impact on hemodynamic variables before induction of cardiac arrest. Accordingly, the purpose of the study reported here was to evaluate published CPR reports with regard to their anesthesia protocol. Methods: Of 100 articles that reported on laboratory models simulating cardiac arrest between 1987 and 1997 in peer-reviewed journals, 25 met inclusion criteria and were analyzed for values of coronary perfusion pressure, mean arterial pressure, heart rate, temperature, and cardiac index before induction of cardiac arrest. Subsequently, mean values for all animals in a given report were calculated and corrected for group size; statistical analysis was not performed since this was a survey only. Results: Different anesthesia protocols resulted in a widely distributed pattern of hemodynamic variables prior to induction of cardiac arrest. Ranges compared with reference values were: heart rate, 100 to 122 beats/min versus 105 ± 11 beats/min; mean arterial pressure, 68 to 130 mm Hg versus 102 ± 9 mm Hg; coronary perfusion pressure, 55 to 114 mm Hg (no reference value); cardiac index, 69 to 152 ml/kg/min versus 147 ± 22 ml/kg/min; body temperature, 37 to 38.5°C versus 38.5 ± 0.7°C. Conclusion: The anesthesia protocol may have an impact on hemodynamic variables before induction of cardiac arrest in CPR studies.