Methylene blue compared to norepinephrine in the management of vasoplegic syndrome in pediatric patients after cardiopulmonary bypass: a randomized controlled study

Background and aim
Vasoplegic syndrome (VS) is a frequent complication following cardiopulmonary bypass (CPB) requiring escalating dose of vasopressor support. The guanylate cyclase inhibitor methylene blue (MB) could be an attractive alternative treatment in such cases. This study examines the efficacy and safety of using MB compared to the commonly used norepinephrine in VS in pediatric population following CPB.
Methods
Forty patients of pediatric age group who developed VS following CPB for elective corrective cardiac surgeries received 0.5 μg/kg/min norepinephrine intravenous infusion for 5 min without improvement (Time 1). Patients were randomly assigned to two equal groups. Group MB received 1.5 mg/kg methylene blue by intravenous infusion over 20 min. Group N did not receive MB. Norepinephrine infusion was continued in both groups and titrated according to the response of patients with a maximum dose of 2 μg/kg/min (Time 2). Heart rate, mean arterial pressure (MAP), central venous pressure (CVP), cardiac output (CO), cardiac index (CI), mean pulmonary artery pressure (MPAP), systemic vascular resistance (SVR) and systemic vascular resistance index (SVRI) were calculated in both groups. Side effects related to the study drug were recorded.
Results
Time 2 values of norepinephrine dose were significantly lower in MB group compared to N group. Time 2 values of MAP were significantly higher in MB group compared to N group with a significant decrease in HR in MB group compared to N group. No change in the rhythm was detected in the two groups. Time 2 values of CVP were higher in MB group compared to N group. Time 2 values of CO and CI were significantly lower in MB group compared to N group and SVR and SVRI were significantly higher in MB group compared to N group. Time 2 values of MPAP were comparable in both groups and showed no significant change. No side effects from using MB were recorded as pulmonary edema and respiratory distress.
Conclusion
In this study, MB showed superior efficacy and safety in managing VS in pediatrics following CPB compared to the conventionally used norepinephrine.