Methaemoglobinemia: a diagnosis of surprise with recent literature review and management

Abstract Background Methaemoglobinemia (MetHb) is a rare entity in clinical practice which often goes undiagnosed and keeps both the anaesthesiologist attending surgeon under tension during surgery on seeing dark or chocolate-coloured blood surgical field. A low oxygen saturation (SpO2) will further panic us to search for cause but may end futile. To add further, SpO2 not rise significantly with adequate oxygenation reach 100 fraction of inspired (FiO2) 1 searching cause. An arterial gas (ABG) finally clinches our diagnosis. It missed pre-anaesthetic evaluation due its rarity patient being asymptomatic most time. Case presentation We present case 61-year-old man, reformed smoker hypertensive regular medication was evaluated laparoscopic partial nephrectomy right renal cell carcinoma. MetHb diagnosed preoperatively midst COVID pandemic when we had all patients’ room air recorded thus helped smooth hassle-free management vitamin C 5 days an uneventful perioperative period. Conclusions uncommon potentially reversible hypoxia. simple bedside give hint diagnosis along high haematocrit urges order ABG no other attributable. preoperative can lead effective reduces methaemoglobin levels have favourable outcome. According literature, any level less than 20% does much significance patients need be deferred.