Vasoplegic shock in cardiac surgery, the role of methylene blue from a clinical pharmacology view. A review article

Narrative review of methylene blue in vasoplegic shock after cardiac surgery in adult intensive care patients. A literature search was made in PubMed, Embase, Ovid, and the grey literature databases. Vasoplegic shock is a postoperative complication of cardiac surgery. It is characterised by arterial hypotension, low systemic vascular resistance, low ventricular filling pressures, a normal or elevated cardiac index, and vasopressor medication requirement. The conventional treatment is based on the administration of fluids and vasopressor therapy with catecholamines and vasopressin. When this management is not effective, methylene blue, tricyclic phenothiazine, is used as a therapeutic alternative. This acts by inhibiting nitric oxide synthase, guanylate cyclase, and relaxation induced by acetylcholine, thus improving the tone vascular and refractory hypotension associated with endothelial dysfunction. It is concluded that the evidence supports the use of methylene blue in vasoplegic shock in the postoperative period of cardiac surgery as rescue therapy when the management with catecholamines and vasopressin is not effective. The use of methylene blue allows the weaning of conventional vasopressors, a reduction in the duration of vasoplegia in cardiac surgery compared to conventional treatment, and a reduction in mortality. Risk management measures in clinical pharmacology are recommended, including monitoring and prevention of adverse events such as haemolytic anaemia, transaminase elevation, and serotonin syndrome, as well as drug interactions with drugs with a narrow therapeutic margin due to the potential of methylene blue to inhibit cytochrome P450.