Ethyl pyruvate enhances intra-resuscitation hemodynamics in prolonged ventricular fibrillation arrest

Ethyl pyruvate, a versatile protector in inflammation and autoimmunity

Ethyl pyruvate (EP) has potent influence on redox processes, cellular metabolism, and inflammation. It has been intensively studied in numerous animal models of systemic and organ-specific disorders whose pathogenesis involves a strong immune component. Here, basic chemical and biological properties of EP are discussed, with an emphasis on its redox and metabolic activity. Further, its influence on myeloid and T cells is considered, as well as on intracellular signaling beyond its effect on immune cells. Also, the effects of EP on animal models of chronic inflammatory and autoimmune disorders are presented. Finally, a possibility to apply EP as a treatment for such diseases in humans is discussed. Scientific papers cited in this review were identified using the PubMed search engine that relies on the MEDLINE database. The reference list covers the most important findings in the field in the past twenty years.

Chest compressions do not disrupt the seal created by the laryngeal mask airway during positive pressure ventilation: a preliminary porcine study

OBJECTIVE

Pulmonary aspiration of gastric contents occurs 20 to 30% of the time during cardiopulmonary resuscitation (CPR) of cardiac arrest due to loss of protective airway reflexes, pressure changes generated during CPR, and positive pressure ventilation (PPV). Although the American Heart Association has recommended the laryngeal mask airway (LMA) as an acceptable alternative airway for use by emergency medical service personnel, concerns over the capacity of the device to protect from pulmonary aspiration remain. We sought to determine the occurrence of aspiration after LMA placement, CPR, and PPV.

METHODS

We inserted a size 4 LMA, modified so that a vacuum catheter could be advanced past the LMA diaphragm, into the hypopharynx of 16 consecutive postexperimental mixed-breed domestic swine. Fifteen millilitres of heparinized blood was instilled into the oropharynx. Chest compressions were performed for 60 seconds with asynchronous ventilation via a mechanical ventilator. We then suctioned through the LMA for 1 minute. The catheter was removed and inspected for signs of blood. The LMA cuff was deflated, removed, and inspected for signs of blood.

RESULTS

None of 16 animals (95% CI 0-17%) had a positive test for the presence of blood in both the vacuum catheter and the intima of the LMA diaphragm.

CONCLUSIONS

In this swine model of regurgitation after LMA placement, there were no cases with evidence of blood beyond the seal created by the LMA cuff. Future studies are needed to determine the frequency of pulmonary aspiration after LMA placement during CPR and PPV in the clinical setting.

Female sex is not associated with improved rates of ROSC or short term survival following prolonged porcine ventricular fibrillation

OBJECTIVES

There may be a survival benefit in female patients experiencing cardiac arrest, which could affect the interpretation of in vivo animal studies. We hypothesized that sex predicts return of spontaneous circulation (ROSC) and short-term survival (SURV) in porcine studies of prolonged ventricular fibrillation (VF).

METHODS

Retrospective analysis of eight comparable experiments performed in our lab using mixed-breed domestic swine of either sex. All experiments included prolonged untreated VF, CPR, defibrillation, and drugs. We defined ROSC as systolic blood pressure ≥80 mm Hg for ≥1 min. Short-term survival was defined 20 or 60 min, depending on protocol. Categorical variables were compared with chi-square test and Fisher's exact test. Continuous variables were compared with two-sample t-test and one-way ANOVA. Multiple logistic regression determined predictors of ROSC and SURV, utilizing cluster analysis by experimental protocol. Candidate variables were sex, weight, anesthesia duration, VF duration, and CPR ratio.

RESULTS

Of 263 swine analyzed (53.2% male), 58.6% of males and 68.3% of females had ROSC (p=0.10), whereas 50.0% of males and 61.0% of females experienced SURV (p=0.07).

RESULTS

Of 263 swine analyzed (53.2% male), 58.6% of males and 68.3% of females had ROSC (p=0.10), whereas 50.0% of males and 61.0% of females experienced SURV (p=0.07). Neither sex nor any identified candidate variable predicted ROSC or SURV. Both models had acceptable fit with Hosmer-Lemeshow values of 0.35 and 0.31, respectively.

CONCLUSIONS

Sex predicts neither ROSC nor SURV in a swine model of prolonged VF.

Conceptual models of coronary perfusion pressure and their relationship to defibrillation success in a porcine model of prolonged out-of-hospital cardiac arrest

INTRODUCTION

The amount of myocardial perfusion required for successful defibrillation after cardiac arrest is unknown. Coronary perfusion pressure (CPP) is a surrogate for myocardial perfusion. One limited clinical study identifies a threshold of 15 mmHg required for return of spontaneous circulation (ROSC). Our exploration of threshold and dose models of CPP during the initial bout of CPR indicates higher levels than previously demonstrated are required. CPP required for shock success throughout on-going resuscitation is unknown and other conceptual models of CPP have not been explored.

HYPOTHESIS

An array of conceptual models of CPP is associated with and predicts defibrillation success throughout resuscitation.

METHODS

Data from 6 porcine cardiac arrest studies were pooled. Mean and area under the curve (AUC) CPP were derived for 30-s epochs. Five conceptual models of CPP were analyzed: threshold, delta, cumulative delta, dose, and cumulative dose. Comparative statistics were performed with one-way ANOVA and two-tailed t-test. Regression models assessed CPP trends and prediction of ROSC.

RESULTS

For 316 defibrillation attempts in 124 animals, those resulting in ROSC (n=75) had significantly higher threshold, delta, cumulative delta, dose, and cumulative dose CPP than those without. All conceptual models except delta CPP had significantly different values across successive defibrillation attempts and all five models were significant predictors of ROSC, along with experimental design.

CONCLUSIONS

Threshold, delta, cumulative delta, dose, and cumulative dose CPP predict individual defibrillation success throughout resuscitation.

Coronary perfusion pressure and return of spontaneous circulation after prolonged cardiac arrest

INTRODUCTION

The 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.

OBJECTIVE

To 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.

METHODS

Data 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.

RESULTS

Throughout 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).

CONCLUSION

Higher CPP threshold and dose are associated with and predictive of ROSC.