No assisted ventilation cardiopulmonary resuscitation and 24-hour neurological outcomes in a porcine model of cardiac arrest

OBJECTIVES: To evaluate the effect of no assisted ventilation cardiopulmonary resuscitation on neurologically intact survival compared with ten positive pressure ventilations/minute cardiopulmonary resuscitation in a pig model of cardiac arrest. DESIGN: Prospective randomized animal study. SETTING: Animal laboratory. SUBJECTS: Sixteen female intubated pigs (25.2 ± 2.1 kg) anesthetized with propofol. INTERVENTIONS: fter 8 mins of untreated ventricular fibrillation, the intubated animals were randomized to 8 mins of continuous chest compressions (100/min) and either no assisted ventilation (n = 9) or 10 positive pressure ventilations/min (Smart Resuscitator Bag with 100% O2 flow at 10 L/min) (n = 7). The primary end point, neurologically intact 24-hr survival, was evaluated using a pig cerebral performance category score by a veterinarian blinded to the cardiopulmonary resuscitation method. MEASUREMENTS, AND MAIN RESULTS: During cardiopulmonary resuscitation, aortic and coronary perfusion pressure were similar between groups but cerebral perfusion pressure was significantly higher in the positive pressure ventilation group (33 ± 15 vs. 14 ± 14, p =.04). After 7.5 mins of cardiopulmonary resuscitation, arterial pO2 (mm Hg) and mixed venous O2 saturation (%) were significantly higher in the positive pressure ventilation compared with the no assisted ventilation group (117 ± 29 and 41 ± 21 vs. 40 ± 24 and 10.8 ± 7; p =.01 for both). Paco2 was significantly lower in the positive pressure ventilation group (48 ± 10 vs. 77 ± 26, p =.01). After 24 hrs, four of nine no assisted ventilation pigs were alive with a mean cerebral performance category score of 3 ± 0 vs. five of seven alive and neurologically intact positive pressure ventilation pigs with a cerebral performance category score of 1 ± 0.3 (p <.001 for cerebral performance category score). CONCLUSIONS: No assisted ventilation cardiopulmonary resuscitation results in profound hypoxemia, respiratory acidosis, and significantly worse 24-hr neurologic outcomes compared with positive pressure ventilation cardiopulmonary resuscitation in pigs.