Abstract 434: A Randomized Blinded Trial of Three Chest Compression Strategies in a Porcine Model of Pediatric Cardiac Arrest

Abstract

Background: Current guidelines recommend that chest compressions for children be done at either 1.5 inches depth and 100 per minute, or one-third the chest A-P diameter depth and 100 per minute. Neither of these recommendations is based on scientific evidence. Objective: As part of an ongoing efficacy trial, we sought to compare the safety of three different chest compression strategies in a porcine model of pediatric cardiac arrest. Methods: Following anesthesia, instrumentation, and induction of asphyxial cardiac arrest, we randomly assigned 48 domestic swine to one of three groups (n=16 per group). The mean mass of 25.7 kg approximates the 50 th percentile for a 7 year old. Group 1 had fixed chest compression depth of 1.5 inches/rate 100; group 2 had fixed proportional depth of one-third the A-P diameter/rate 100; group 3 used an adaptive algorithm that incrementally increased chest compression rate and/or depth from baseline 1.5in (max: 2.13in) and 100/min (max; 130/min) every 25s while coronary perfusion pressure was below 25mmHg. Necropsies were independently performed by a veterinarian and veterinary technologist who were blinded to group assignment. The primary safety outcome was unrecoverable injury (i.e. toxicity), which we defined as either a total lung injury score ≥16 (score can range from 0 to 20) plus presence of hemothorax, or disruption of either the aorta or vena cava. Data were analyzed with the Bayesian Beta Binomial to determine if within-group toxicity exceeded an unacceptable level (30%) with a pre-selected posterior predictive threshold of 0.75(ptox). Lung injury scores between groups were compared with Kruskal-Wallis tests. Results: Median total lung injury scores were: 12 for group 1; 18 for group 2; 14 for group 3. Group 2 was significantly different from both groups 1 and 3 (p<0.001). Groups 1 and 3 did not differ (p=0.24). Toxicity occurred in zero animals in group 1 (ptox=0.0001); 7 animals in group 2 (ptox=0.8180); and 1 animal in group 3 (ptox=0.0076). The posterior probability threshold was exceeded in group 2 which warranted termination of the treatment arm for safety. Conclusions: Chest compressions performed at a depth of one-third the A-P diameter are unsafe. The safety of this approach in children should be carefully evaluated.