Does normoxemic cardiopulmonary bypass prevent myocardial reoxygenation injury in cyanotic children?

Abstract

Objective: To evaluate whether the deleterious effect of cardiopulmonary bypass (CPB) can be prevented by controlling PaO2 in cyanotic children. Design: Prospective randomized clinical study. Setting: Single university hospital. Participants: Pediatric patients undergoing cardiac surgery for repair of congenital heart disease (n = 24). Interventions: Patients were randomly allocated into 3 groups. Patients in the acyanotic group (group I n = 10) had CPB initiated at a fraction of inspired oxygen (F1O2) of 1.0 (PO2 300 to 350 mmHg). Cyanotic patients were subdivided as follows: Group 11 (n = 7) had CPB initiated at an F1O2 of 1.0 and group III (n = 7) had CPB initiated at an F1O2 of 0.21 (PO2 90 to 110 mmHg). A biopsy specimen of right atrial tissue was removed during venous cannulation and another sample was removed after CPB before aortic cross-clamping. The tissue was incubated in 4 mmol/L of t-butylhydroperoxide and the malondialdehyde (MDA) level was measured to determine the antioxidant reserve capacity. Blood samples for cytokine levels tumor necrosis factor (TNF)-alpha and interleukin (IL)-6 response to CPB were collected after induction of anesthesia and at the end of CPB before prolamine administration. Measurements and Main Results: After initiation of CPB MDA level rose markedly in the cyanotic groups compared with the acyanotic group (210 +/- 118% v 52 +/- 34% p < 0.05) which indicated the depletion of antioxidants. After initiation of CPB TNF-&alpha

and IL-6 levels of the cyanotic groups were higher than for the acyanotic group (168 +/- 77 v 85 +/- 57 p < 0.001

249 +/- 131 v 52 +/- 40

p < 0.001). When a comparison between the cyanotic groups was performed group II (initiating CPB at an F1O2 of 1.0) had significantly increased MDA production compared with group III (initiating CPB at an F1O2 of 0.21) (302 +/- 134% v 133 +/- 74% p < 0.05). Group If had higher TNF-alpha and IL-6 levels than group III (204 +/- 81 v 131 +/- 52 p < 0.001

308 +/- 147 v 191 +/- 81 p < 0.01). Conclusion: Conventional clinical methods of initiating CPB at a hyperoxemic PO2 may increase the possibility of myocardial reoxygenation injury in cyanotic children. This deleterious effect of reoxygenation can be modified by initiating CPB at a lower level of oxygen concentration. Subsequent long-term studies are needed to determine the best method of decreasing the oxygen concentration of the CPB circuit. Copyright 2002 Elsevier Science (USA). All rights reserved.