Hydroxocobalamin Dosing Strategies for Vasoplegic Syndrome Post-cardiac Surgery: A Retrospective Cohort Study.

introductionVasoplegic syndrome is a common complication following cardiac surgery, characterized by profound hypotension and high vasopressor requirements. Hydroxocobalamin, traditionally used for cyanide toxicity, has shown promise in treating refractory vasoplegic syndrome by scavenging nitric oxide. This study compares the efficacy of bolus versus extended infusion dosing strategies of hydroxocobalamin in reducing catecholamine requirements post-cardiac surgery.

methodsWe conducted a retrospective, single-center cohort study of adult patients (>18 years) admitted to the intensive care unit (ICU) after cardiac surgery between February 2020 and October 2022 who received hydroxocobalamin for vasoplegic syndrome (mean arterial pressure <65 mmHg, requiring vasopressors). Patients were grouped by hydroxocobalamin dosing: bolus (over 15 minutes) or extended infusion (over six hours). Exclusion criteria included prior methylene blue use, postoperative extracorporeal membrane oxygenation (ECMO), or intraoperative hydroxocobalamin administration. The primary outcome was the percent change in norepinephrine equivalents (NEE) over 12 hours post-administration. Secondary outcomes included NEE area under the curve (AUC), ICU and hospital length of stay, hospital survival, and additional scavenging therapy or ECMO use. Statistical analyses used Fisher's exact test for categorical data and the Wilcoxon rank-sum test for continuous data (PC SAS v9.4, significance at p < 0.05).

resultsOf 55 patients receiving hydroxocobalamin, 13 met the inclusion criteria (eight in the bolus group and five in the extended infusion group). Baseline characteristics were similar, with 85% male patients, a median age of 61 years, and a median cardiopulmonary bypass (CPB) duration of 184 minutes (p=0.71). The percent change in NEE at 12 hours was not significantly different between groups (p=0.6084). However, the NEE AUC was significantly higher in the bolus group (median: 11.59 (interquartile range (IQR): 11.21-12.30) vs. 8.463 (IQR: 5.160-8.728), p=0.0068). Additional scavenging therapy was more frequent in the bolus group (62.5% vs. 20%, p=0.46). No differences were observed in ICU stay (23 vs. 8 days, p=0.71), hospital stay (31.5 vs. 29 days, p=0.66), or mortality (62.5% vs. 60%, p=1.0).

conclusionsBolus and extended infusion hydroxocobalamin dosing showed no significant difference in NEE reduction at 12 hours, though the bolus group had a higher NEE AUC, suggesting a less sustained effect. Further research is needed to optimize dosing strategies for vasoplegic syndrome post-cardiac surgery.