Does cardioplegia leave room for postconditioning in paediatric cardiac surgery?

Postconditioning by brief episodes of ischaemia performed just at the time of reperfusion have been shown to reduce the size of infarcts in animal models, and in the clinical setting of percutaneous cardiac intervention. The clinical applicability of postconditioning in cardiac surgery remains to be determined. We investigated the effect of postconditioning on myocardial protection in children undergoing cardiac surgery.

We randomly assigned 40 patients scheduled for surgical correction of congenitally malformed hearts under cold blood cardioplegic arrest to postconditioning or control treatment. Postconditioning was performed by two cycles of 30 seconds ischaemia and 30 seconds reperfusion using aortic reclamping, and declamping started 30 seconds after cardioplegic arrest. We assayed creatine kinase-MB, troponin I, transcardiac release of lactate and neutrophil counts.

The types of procedure, age, bypass and aortic cross-clamping times were similar in both groups. The postoperative peaks of creatine kinase-MB and troponin I were lower after aortic de-clamping in the postconditioned patients compared with their controls (128 +/- 48 units per liter as opposed to 199 +/- 79 units per liter, p = 0.016, and 0.34 +/- 0.21 nanograms per milliliter as opposed to 0.61 +/- 0.53 nanograms per milliliter, p = 0.05), with reduced inotropic scores in those submitted to postconditioning compared with their controls (4.8 +/- 3.1 versus 2.3 +/- 1.5, p = 0.036). Transcardiac release of lactate was reduced in the postconditioned patients compared with their controls (0.10 +/- 0.27 as opposed to 0.37 +/- 0.43 millimols per liter, p = 0.048). No differences between groups were found for transcardiac neutrophil count during reperfusion (10.8 +/- 6.3% for postconditioning versus 14.0 +/- 8.7% for controls, p = 0.48).

Our study demonstrates that postconditioning may protect the myocardium of children undergoing cold blood cardioplegic arrest. These data support the need for a larger clinical trial of postconditiong in children undergoing cardiac surgery.