Acute-phase responses to cardiopulmonary bypass in children weighing less than 10 kilograms

Background. Cardiopulmonary bypass induces a systemic inflammatory response. This study investigated, in a pediatric population, cytokine-induced responses and their potential modification by intraoperative steroid administration. Methods. Markers of the acute-phase response were measured perioperatively in 24 children weighing less than 10 kg undergoing cardiac operations. Those having operations with cardiopulmonary bypass were randomized to receive either no steroid (group I, n = 8) or 10 mg/kg methylprednisolone in the pump prime (group II, n = 10); patients undergoing nonbypass procedures were controls (group III, n = 6). Results. In all groups, plasma interleukin-6 level was elevated (p < 0.01) above baseline throughout the postoperative period, peaking earlier in group I. Levels of C-reactive protein peaked at 48 hours, and postoperative core temperature was raised in all groups. Levels of interleukin-6 from 2 to 6 hours and C-reactive protein at 24 hours postoperatively were greater (p < 0.05) in group I than in group II. Maximum interleukin-6 level, C-reactive protein level, and temperature were all significantly greater in group I than in group III. Maximum interleukin-6 level correlated with maximum C-reactive protein level in group I only (rs = 0.76; p < 0.05) and showed no association with temperature. Duration of bypass did not correlate with levels of interleukin-6. Conclusions. This study demonstrated a marked acute-phase response to operation; the greater response to procedures with cardiopulmonary bypass was abrogated by intraoperative steroid administration. The importance of interleukin-6 as an inducer of acute phase proteins after bypass is supported by its association with C-reactive protein levels, but other factors must be important in the induction of pyrexia.