Objectives To compare myocardial protection afforded by three single-dose cardioplegic solutions — Custodiol (HTK), del Nido (DN) and modified del Nido (MDN) — in adult elective cardiac surgery.

Design Double-blind randomised controlled trial.

Setting Tertiary hospital in southern Brazil.

Participants 99 adults undergoing elective valve or coronary artery bypass surgery with cardiopulmonary bypass.

Interventions Administration of HTK, DN or MDN solution during surgery.

Main outcome measures High-sensitivity cardiac troponin T (hs-cTnT) at 0, 2, 12 and 24 hours postoperatively. Additionally, indirect measures of myocardial protection were compared, both laboratory and clinical, during intraoperative and postoperative periods.

Results All solutions provided effective myocardial protection, with similar clinical and laboratory outcomes. DN was associated with significantly lower hs-cTnT at 2 hours (p=0.023) and fewer intraoperative transfusions (p=0.008). HTK patients had lower postoperative sodium and potassium levels (p=0.049 and p=0.002, respectively). Survival and major postoperative outcomes, including vasoactive or mechanical support, were similar across groups.

Conclusions The three cardioplegic strategies showed comparable biochemical profiles of myocardial injury. DN was associated with lower early troponin release and reduced transfusion requirements, while HTK produced transient electrolyte shifts.