• Carole Maurin, Philippe Portran, Remi Schweizer, Bernard Allaouchiche, Stéphane Junot, Matthias Jacquet-Lagrèze, and Jean-Luc Fellahi.
• From the Service d'Anesthésie Réanimation, Hôpital Cardiovasculaire et Pneumologique Louis Pradel (CM, PP, RS, MJ-L, J-LF), Service d'Anesthésie-Réanimation, Centre Hospitalier Lyon Sud, Hospices Civils de Lyon (BA), APCSe, Université de Lyon, VetAgro Sup - Campus Vétérinaire de Lyon (SJ) and Laboratoire CarMeN, Inserm U1060, Université Claude Bernard Lyon 1, Campus Lyon Santé Est, Lyon, France (MJ-L, J-LF).
• Eur J Anaesthesiol. 2022 Apr 1; 39 (4): 333341333-341.

BackgroundMethylene blue is used as rescue therapy to treat catecholamine-refractory vasoplegic syndrome after cardiac surgery. However, its microcirculatory effects remain poorly documented.ObjectiveWe aimed to study microcirculatory abnormalities in refractory vasoplegic syndrome following cardiac surgery with cardiopulmonary bypass and assess the effects of methylene blue.DesignA prospective open-label cohort study.Setting20-Bed ICU of a tertiary care hospital.Patients25 Adult patients receiving 1.5 mg kg-1 of methylene blue intravenously for refractory vasoplegic syndrome (defined as norepinephrine requirement more than 0.5 μg kg-1 min-1) to maintain mean arterial pressure (MAP) more than 65 mmHg and cardiac index (CI) more than 2.0 l min-1 m-2.Main Outcome MeasuresComplete haemodynamic set of measurements at baseline and 1 h after the administration of methylene blue. Sublingual microcirculation was investigated by sidestream dark field imaging to obtain microvascular flow index (MFI), total vessel density, perfused vessel density and heterogeneity index. Microvascular reactivity was assessed by peripheral near-infrared (IR) spectroscopy combined with a vascular occlusion test. We also performed a standardised measurement of capillary refill time.ResultsDespite normalised CI (2.6 [2.0 to 3.8] l min-1 m-2) and MAP (66 [55 to 76] mmHg), patients with refractory vasoplegic syndrome showed severe microcirculatory alterations (MFI < 2.6). After methylene blue infusion, MFI significantly increased from 2.0 [0.1 to 2.5] to 2.2 [0.2 to 2.8] (P = 0.008), as did total vessel density from 13.5 [8.3 to 18.5] to 14.9 [10.1 to 14.7] mm mm-2 (P = 0.02) and perfused vessel density density from 7.4 [0.1 to 11.5] to 9.1 [0 to 20.1] mm mm-2 (P = 0.02), but with wide individual variation. Microvascular reactivity assessed by tissue oxygen resaturation speed also increased from 0.5 [0.1 to 1.8] to 0.7 [0.1 to 2.7]% s-1 (P = 0.002). Capillary refill time remained unchanged throughout the study.ConclusionIn refractory vasoplegic syndrome following cardiac surgery, we found microcirculatory alterations despite normalised CI and MAP. The administration of methylene blue could improve microvascular perfusion and reactivity, and partially restore the loss of haemodynamic coherence.Trial RegistrationClinicalTrials.gov identifier: NCT04250389.Copyright © 2021 European Society of Anaesthesiology and Intensive Care. Unauthorized reproduction of this article is prohibited.

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