Impact of peroperative administration of steroid over inflammatory response and pulmonary dysfunction following cardiac surgery

Introduction

Cardiac surgery with cardiopulmonary bypass (CPB) is a recognized trigger of systemic inflammatory response, usually related to postoperative acute lung injury (ALI). As an attempt to dampen inflammatory response, steroids have been perioperatively administered to patients. Macrophage migration inhibitory factor (MIF), a regulator of the endotoxin receptor, is implicated in the pathogenesis of ALI. We have previously detected peak circulating levels of MIF, 6 hours post CPB. Experimental data have shown that steroids may induce MIF secretion by mononuclear cells. This study aims to correlate levels of MIF assayed 6 hours post CPB to the intensity of postoperative pulmonary dysfunction, analysing the impact of perioperative steroid administration.

Methods

We included patients submitted to cardiac surgery with CPB, electively started in the morning, performed by the same team under a standard technique except for the addition of methylprednisolone (15 mg/kg) to the CPB priming solution for patients from group MP (n = 37), but not for the remaining patients – group NS (n = 37). MIF circulating levels were assayed at the anesthesia induction, 3, 6, and 24 hours after CPB. A standard weaning protocol with fast track strategy was adopted, and indicators of organ dysfunction and therapeutic intervention were registered during the first 72 hours postoperative.

Results

Levels of MIF assayed 6 hours post CPB correlated directly to the postoperative duration of mechanical ventilation (P = 0.014, rho = 0.282) and inversely to PaO₂/FiO₂ ratio (P = 0.0021, rho = -0.265). No difference in MIF levels was noted between the groups. The duration of mechanical ventilation was higher (P = 0.005) in the group MP (7.92 ± 6.0 hours), compared with the group NS (4.92 ± 3.6 hours).

Conclusion

Circulating levels of MIF assayed 6 hours post CPB are correlated to postoperative pulmonary performance. Immunosuppressive doses of methylprednisolone did not affect circulating levels of MIF and may be related to prolonged mechanical ventilation.