Intermittent cold blood cardioplegia is commonly used in children whereas intermittent warm blood cardioplegia is widely used in adults. We aimed to compare clinical and biochemical outcomes with these two methods.

A single centre, randomized controlled trial was conducted to compare the effectiveness of warm (≥34°C) versus cold (4–6°C) antegrade cardioplegia in children. The primary outcome was cardiac troponin T over the first 48 postoperative hours. Intensive care teams were blinded to group allocation. Outcomes were compared by intention-to-treat using linear mixed-effects, logistic, or Cox regression.

97 participants with median age of 1.2 years were randomized (49 to warm, 48 to cold cardioplegia); 59 participants (61%) had a risk-adjusted congenital heart surgery score of 3 or above. There were no deaths and 92 participants were followed to 3-months. Troponin release was similar in both groups (geometric mean ratio 1.07; 95% confidence interval [CI], 0.79–1.44; P = 0.66), as were other cardiac function measures (echocardiography, arterial and venous blood gases, vasoactive-inotrope score, arrhythmias). Intensive care stay was on average 14.6 hours longer in the warm group (hazard ratio 0.52; 95% CI, 0.34–0.79; P = 0.003), with a trend towards longer overall hospital stays (hazard ratio 0.66; 95% CI, 0.43–1.02; P = 0.060) compared with the cold group. This could be related to more unplanned reoperations on bypass in the warm group compared to cold group (3 vs 1).

Warm blood cardioplegia is a safe and reproducible technique but does not provide superior myocardial protection in paediatric heart surgery.