Strengths and limitations
myocardial damage
SEPARATION, COLD
This is one of few adequately powered RCTs focused on paediatric myocardial protection. Strengths are: inclusivity of the eligibility criteria; concealed allocation to minimize selection bias; objective outcomes and blinding to minimize detection bias, and minimal attrition. Stratification by RACHS score ensured the more complex cases were balanced across groups. A single laboratory was used for sample analysis, thereby avoiding inter-laboratory variability.With respect to limitations, participants were recruited from a single hospital which limits the generalizability of the findings. The 2 crystalloid formulas were not identical, but they represent the most common preparations used in myocardial protection in children for cold and warm myocardial protection. They are the solutions used outside the trial setting at the study centre. There were protocol deviations, mostly related to staff being unblinded after accessing anaesthetic and perfusion records; these would be expected to have minimal impact given the objective nature of most outcomes. The 4 crossovers could have reduced the differences in outcome between groups, but there was good separation in cardioplegia temperatures reflecting adherence to the protocol. Furthermore, the crossovers (4.1%) did not reduce the statistical power; the sample size without allowance for missing data was 80 participants, allowing for 5% crossover increases the sample size to 90 participants. Overall, 95 participants contributed primary outcome data. There are limitations to the data, specifically preoperative echocardiograms rarely assessed ventricular function, thereby limiting our ability to adjust analyses for presurgery cardiac function. Fitness for discharge from PICU was not recorded reliably so actual transfer times were used, but any delays are unlikely to be differential between groups. The study has a wide range of ages and pathologies; a higher percentage of participants with RACHS score ≥3 would have further increased the applicability of the findings. cTnT is not measured routinely in clinical practice. While it provides reassurance in terms of myocardial damage, it is not a direct measurement of function. We envisaged supplementing this with a detailed echocardiographic assessment of systolic and diastolic function [