Effects of ultrafiltration and peritoneal dialysis on proinflammatory cytokines during cardiopulmonary bypass surgery in newborns and infants.

OBJECTIVES

To assess the impact of balanced ultrafiltration and peritoneal dialysis (PD) on plasma and urinary cytokines and renal dysfunction after cardiopulmonary bypass (CPB) surgery in newborns and infants.

METHODS

Twenty-three newborns and infants weighing less than 7 kg and scheduled for operation on congenital malformation were enrolled in this descriptive open clinical study. All patients received conventional ultrafiltration in the CPB rewarming period. Eleven newborns underwent Tenckhoff-catheter implantation in the operation theatre as a routine institutional procedure and received PD after admission to the ICU (the PD [+] group). No PD was used in another 12 patients (the PD [-] group). Interleukins (IL) 6 and 8 were measured four times pre- and post-operatively. Kidney function was assessed by creatinine clearances and urine protein and enzyme analyses.

RESULTS

All patients had an uneventful clinical course. Age (10+/-2 days, PD [+] vs. 96+/-19 days, PD [-]), CPB duration (215+/-23 vs. 143+/-20 min), and degree of hypothermia (26+/-1.3 vs. 31+/-0.1 degrees C) differed significantly between the groups. Age, CPB duration and ultrafiltration influenced post-operative IL-levels in an analysis of variance. While there were few differences immediately after the end of ultrafiltration, post-operative levels of IL-6 and IL-8 were higher and more sustained in the newborns (PD [+]) than in the older infants (PD [-]). The median amount of IL-6 and IL-8 removed by ultrafiltration came to 28 and 59% compared to the amount of IL-6 and IL-8 remaining in the blood at the end of CPB. IL-clearance by ultrafiltration was more than 1000-fold and by PD more than 100-fold as effective as IL-clearance by the kidney. While the kidneys showed an unselective mixed glomerular and tubular pattern of injury, during CPB higher serum IL-concentrations correlated with lower urinary IL-clearances in both study groups.

CONCLUSIONS

Ultrafiltration and PD are highly effective in removing proinflammatory cytokines. Impaired kidney function was associated with proinflammatory IL-serum concentrations. Thus, we raise the hypothesis that glomerular-filtered proinflammatory ILs damage the proximal tubular cells of the kidney in newborns and infants, thus contributing to post-operative renal dysfunction. Conversely, we conclude that removing proinflammatory ILs by ultrafiltration and PD acts renoprotectively. A future prospective randomised study could demonstrate whether this can indeed improve clinical outcome.