Methemoglobinemia: An unusual cause of postoperative cyanosis

Abstract

Methemoglobinemia, although rare, must be considered in surgical patients presenting with acute respiratory distress and cyanosis. We report two cases of methemoglobinemia in patients undergoing aortic reconstruction. The first patient developed methemoglobinemia while on a nitroglycerin infusion, and the second after receiving benzocaine spray before intubation. Both patients were treated with methylene blue and ascorbic acid, with resolution of their hypoxia and cyanosis. The pathophysiology, etiology, diagnosis, and treatment of methemoglobinemia are reviewed.

Prilocaine induced methaemoglobinaemia in a medically compromised patient. Was this an inevitable consequence of the dose administered?

“…In this state the oxygen-binding properties of haemoglobin are inhibited. The body is subjected to continual production of 1 *Staff Grade Oral and Maxillofacial Surgery, 2 Senior Lecturer/Consultant Oral Surgeon, 3 Consultant in Anaesthesia, Royal Victoria Hospital Belfast, 274 Grosvenor Road, Belfast BT12 6BA *Correspondence to: Dr Victoria Adams Email: vickyandy12@yahoo.co.uk MetHb due to various oxidant stresses. However, the levels of MetHb are nor mally kept below 1%, mainly due to the action of two enzyme systems:…”

“…1,2 MetHb may present with a variety of symptoms depending on the concentration of methaemoglobin (Table 4). 2,3 The non-specific nature of the symp toms may make diagnosis diffi cult.…”

The novel nitric oxide donor PDNO attenuates ovine ischemia-reperfusion induced renal failure

“…Methemoglobinemia is a known side effect of both intravenous and inhalational NO treatments, most often after high doses have been administered [47, 48]. Our results indicate that PDNO can be infused intravenously at a rate sufficient for beneficial systemic effects without causing methemoglobinemia.…”

Diagnostic dilemma: Low oxygen saturation during cardiac surgery

“…[1] Co-oximetry, which measures light absorbance at four different wavelengths, using spectrophotometry, is one of the most accurate ways of measuring MHb levels. Since cooximeters are not routinely used and MHb levels are not routinely performed on ABG analyzers, in case of clinical suspicion, advanced ABG analysis machines should be used for timely detection of methemoglobinemia in the presence of associated cardiac disease[4] as we did in our case.…”

“…However, sometimes, in patients who are undergoing cardiac surgery, the cause of low oxygen saturation on pulse oximetry may not be easily explainable or attributed to the cardiopulmonary cause, and the anesthesiologist should be vigilant about some rare differential diagnosis even in the presence of cardiac disease. [1] We report a case of severe mitral stenosis with diagnostic dilemma of low oxygen saturation on pulse oximetry.…”