Methylene blue and hydroxocobalamin in a severely vasoplegic lung transplant recipient

ABSTRACT

INTRODUCTION: Vasoplegia is defined as a refractory shock state with profound hypotension in the setting of reduced systemic vascular resistance and high cardiac output. Lung transplantation is an arduous surgery often requiring cardiopulmonary bypass, which ultimately predisposes to vasoplegia. We detail the treatment of a patient with end-stage lung disease secondary to COVID-19 pneumonia undergoing lung transplant who developed vasoplegia. DESCRIPTION The patient is a 36-year-old female who was admitted with profound hypoxemic respiratory failure secondary to COVID-19 pneumonia. Despite initial therapy, she remained ventilator-dependent with need for extracorporeal membrane oxygenation (ECMO) support. Given her single organ failure status - lungs being solely affected - she was promptly considered for lung transplant evaluation upon resolution of her active SARS-CoV-2 infection. She was ultimately deemed appropriate for listing and underwent subsequent transplant. The surgery required the use of cardiopulmonary bypass, given the extensive adhesions of the native COVID-19-infected lungs. The lungs were, unfortunately, quite necrotic, with multiple purulent pockets. She was profoundly hypotensive throughout the surgery and required massive fluid resuscitation, as well as multiple vasopressors. In the setting of this vasoplegia, she received multiple doses of methylene blue at 2 mg/kg, with only marginal improvement in blood pressure. Decision was made to add high-dose (5 g) hydroxocobalamin in an attempt to synergistically stabilize blood pressure. Intraoperatively, her blood pressure stabilized within hours;she remained on ECMO support and was transferred to the ICU postoperatively. Eventually, she was slowly weaned from her vasopressors, with stable blood pressure. DISCUSSION: Methylene blue mechanistically inhibits inducible nitric oxide synthase and guanylyl cyclase, while hydroxycobalamin acts as a nitric oxide scavenger. Both agents have been used independently to treat vasoplegia during cardiopulmonary bypass. Together, they may be used as a salvage therapy to improve blood pressure in refractory cases of shock seemingly exacerbated by the cytokine milieu promoted by recent SARS-CoV-2 infection.