Vasoplegic syndrome (VS) is a common and potentially life-threatening complication of cardiac surgery with cardiopulmonary bypass (CPB). It presents a significant haemodynamic challenge that is often difficult to manage and can appear either intraoperatively, upon CPB initiation, or in the early postoperative period. Until recently, VS had been described under various terms, including low vascular resistance syndrome, catecholamine-resistant vasoplegia and post-cardiotomy VS. Moreover, it is also considered part of a broader spectrum of inflammatory responses, such as post-perfusion syndrome, vasoplegic shock or postoperative vasoplegia [1]. This inconsistent terminology and the overlap between definitions have made it challenging to accurately determine its true incidence, establish a standardized diagnostic and therapeutic framework and understand its association with adverse outcomes. Furthermore, the lack of a universally accepted definition hinders the identification of key patient and procedural risk factors that could help reduce VS-associated morbidity and mortality.

In this context, Zhu et al. [2] present a Best Evidence Topic review summarizing data on the use of methylene blue in patients with post-cardiac surgery VS. The review offers a valuable opportunity to assess its role in VS management and evaluate whether its clinical use is supported by robust evidence.