Effect of Hydroxocobalamin Compared to Methylene Blue for Management of Vasoplegia

Abstract

<h3>Purpose</h3> Vasoplegic syndrome is a common complication following cardiac surgery, characterized by profound systemic hypotension from poor systemic vascular resistance (SVR) requiring high doses of vasopressors. Hydroxocobalamin and methylene blue are two medications used to decrease vasoplegia and vasopressors requirements, thereby decreasing morbidity and mortality. The purpose of this study is to evaluate whether hydroxocobalamin or methylene blue is more effective in relieving vasoplegia as defined by reducing vasopressor requirements. <h3>Methods</h3> This was a retrospective chart review performed at an academic medical center between March 2020 through August 2021. Patients ages 18-89 who received a dose of hydroxocobalamin or methylene blue while in a cardiac intensive care unit for vasoplegia were included for analysis. The primary outcome was the time to reduction of 50% of original vasopressor requirements, defined in norepinephrine equivalents. Secondary outcomes include change in mean arterial pressure (MAP), cardiac index, SVR, ICU length of stay (LOS), mortality, and the need for renal replacement therapy. The primary outcome will be expressed as means with standard deviations as well as a time to event analysis with a Kaplan-Meier Curve and log rank test. <h3>Results</h3> Patients were treated with a one-time 5mg dose of hydroxocobalamin (n=8) or dose(s) of methylene blue (n=15). The time to reduction of 50% of vasopressor requirements was 5.75 hours with hydroxocobalamin and 13.08 hours with methylene blue (p=0.0248). Change in MAP at 4 hours post dose was 7.75 mmHg with hydroxocobalamin and -0.93 mmHg in methylene blue (p=0.150). There was no difference in change in cardiac index (p=0.11), ICU LOS (p=0.11), or mortality (p=1). Change in SVR increased by 428.4 dynes/sec/cm5 with hydroxocobalamin and 95.6 dynes/sec/cm5 with methylene blue (p=0.0238). Need for renal replacement therapy was 62.5% with hydroxocobalamin and 13% with methylene blue (p=0.0257). <h3>Conclusion</h3> Use of hydroxocobalamin for vasoplegia is associated with a significantly faster time to a 50% reduction of vasopressor requirements and an increase in SVR post administration compared to methylene blue. Hydroxocobalamin was also significantly associated with an increase in need for renal replacement therapy. The clinical significance of these effects must be determined in larger, randomized controlled trials.