Randomization
HEART
Randomization was stratified by surgical complexity [Risk Adjustment for Congenital Heart Surgery (RACHS) score <3 vs ≥3]. Random allocations were computer-generated using blocks with varying sizes, prepared by a statistician independent of the study team. Allocations were concealed until a patient was recruited and registered onto a secure purpose-designed electronic database. Randomization took place as close to the start of surgery as possible; if a participant’s surgery was unexpectedly rescheduled, they retained their randomized allocation.