• Joshua C Reynolds, David D Salcido, and James J Menegazzi.
• Department of Emergency Medicine, University of Maryland, Baltimore, Maryland 21201, USA. jreynoldsmd@gmail.com
• Prehosp Emerg Care. 2010 Jan 1;14(1):78-84.

IntroductionThe amount of myocardial perfusion required for successful defibrillation after prolonged cardiac arrest is not known. Coronary perfusion pressure (CPP) is a surrogate for myocardial perfusion. One limited clinical study reported that a threshold of 15 mmHg was necessary for return of spontaneous circulation (ROSC), and that CPP was predictive of ROSC. A distinction between threshold and dose of CPP has not been reported.ObjectiveTo test the hypothesis that swine achieving ROSC will have higher preshock mean CPP and higher preshock area under the CPP curve (AUC) than swine not attaining ROSC.MethodsData from four similar swine cardiac arrest studies were retrospectively pooled. Animals had undergone 8-11 minutes of untreated ventricular fibrillation, 2 minutes of mechanical cardiopulmonary resuscitation (CPR), administration of drugs, and 3 more minutes of CPR prior to the first shock. Mean CPP +/- standard error of the mean (SEM) was derived from the last 20 compressions of each 30-second epoch of CPR and compared between ROSC/no-ROSC groups by repeated-measures analysis of variance (RM-ANOVA). AUC for all compressions delivered over the 5 minutes was calculated by direct summation and compared by Kruskal-Wallis test. Prediction of ROSC was assessed by logistic regression.ResultsThroughout the first 5 minutes of CPR (n = 80), mean CPP +/- SEM was consistently higher in animals with ROSC (n = 63) (maximum CPP 41.2 +/- 0.6 mmHg) than animals with no ROSC (maximum CPP 20.1 +/- 0.3 mmHg) (p = 0.0001). Animals with ROSC received more total reperfusion (43.9 +/- 17.6 mmHg x 10(2)) than animals without ROSC (21.4 +/- 13.7 mmHg x 10(2)) (p < 0.001). Two regression models identified CPP (odds ratio [OR] 1.11; 95% confidence interval [CI] 1.05, 1.18) and AUC (OR 1.10; 95% CI 1.05, 1.16) as predictors of ROSC. Experimental study also predicted ROSC in each model (OR 1.70; 95% CI 1.15, 2.50; and OR 1.59; 95% CI 1.12, 2.25, respectively).ConclusionHigher CPP threshold and dose are associated with and predictive of ROSC.

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