Anaesthetic Management Of A Patient With Methemoglobinemia: Case Report And Review Of Literature

Abstract

Methemoglobinemia is a rare but serious haemoglobin disorder when red blood cells contain methaemoglobin at levels higher than 1%. Basically, it results from the oxidation of the ferrous iron in haemoglobin to the ferric iron. Methaemoglobin is incapable of carrying O2, and high levels can impair O2 delivery to the tissues. Methemoglobinemia can be congenital or acquired. Acquired methemoglobinemia is more common than the congenital variety. Several factors must be considered when anesthetizing patients with methemoglobinemia, which include the potential for decreased oxygen delivery, which may be exacerbated by intraoperative blood loss and anaemia, interference with normal intraoperative monitoring devices, and the potential for medications to cause or exacerbate methemoglobinemia. Here we describe a patient with congenital methemoglobinemia, which was diagnosed during preop evaluation for renal transplant on the basis of a discrepancy between the O2 saturation noted by pulse oximetry and that obtained from arterial blood gas analysis and found to have NADH cytochrome b5 reductase deficiency. He is now posted for parathyroidectomy and total thyroidectomy. Anaesthetic care of patients with methemoglobinemia is discussed with a brief review on the topic.