• Pranav R Shah, Penny S Reynolds, Nirvik Pal, Daniel Tang, Harry McCarthy, and Bruce D Spiess.
• Department of Anesthesiology, Virginia Commonwealth University-Medical College of Virginia, Richmond, VA, USA.
• Can J Anaesth. 2018 May 1; 65 (5): 560-568.

PurposeVasoplegia is a clinical syndrome marked by severe arteriolar vasodilatation, hypotension, and low systemic vascular resistance refractory to multiple vasopressor treatment. We report our experience with hydroxocobalamin (B12) infusion as a potential rescue adjunct for refractory vasoplegia during cardiopulmonary bypass (CPB).MethodsWe performed a retrospective chart review of 33 patients undergoing cardiac surgery between 1 January 2013 and 31 December 2015, who were given intravenous B12 for refractory hypotension during, or immediately following, CPB. We assessed mean arterial pressure (MAP) responses using semi-parametric group-based models (trajectory analysis). Vasopressor use was evaluated by norepinephrine-equivalent rates calculated five minutes prior, and up to 60 min following, B12 administration.ResultsPatients were mostly male (82%), had a mean (SD) age of 53 (13) yr, and median (IQR) EuroSCORE mortality index of 9 [4-40]. Four patterns of MAP responses to B12 were identified. In Group 1 ("poor responders") nine of 33 patients (27%) had the highest median [IQR] mortality risk (EuroSCORE 40 [4-52]), lowest mean pre-B12 MAP (50 mmHg), and minimal hemodynamic response in spite of continued vasopressor support. In contrast, Group 2 "responders" (8/33, 24%) showed a brisk MAP response (> 15 mmHg) to B12, sustained for > 60 min post-infusion, with 50% vasopressor reduction. Groups 3 and 4 had the lowest median mortality risk (EuroSCORE 8) and highest pre-B12 MAP (72 mmHg). Although Group 3 patients ("sustainers"; 9/33, 27%) showed a sustained MAP improvement, those in Group 4 ("rebounders"; 7/33, 21%) were characterized by hypertensive overshoot followed by a decrease in MAP.ConclusionThese data indicate considerable heterogeneity in patient response to B12, potentially dependent on both patient preoperative condition and non-standardized time of administration. B12 may provide a useful alternative therapy for refractory hypotension and vasoplegia, but controlled clinical trials to assess efficacy are needed.

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