Adie syndrome associated with general anesthesia.

CAN J ANESTH 55: 2 www.cja-jca.org February, 2008 A 60-yr-old lady with HbM Saskatoon and congenital methemoglobinemia was scheduled for mastectomy. Clinical examination confirmed cyanosis but she had no symptoms due to methemoglobinemia and no history suggestive of cardiac or respiratory problems. Her electrocardiogram was normal and arterial blood gas (ABG) values on room air were: pH = 7.52, pO2 = 104 mmHg, pCO2 = 28 mmHg, BE = 0.9, lactate – within normal limits. We could not obtain details regarding oxyhemoglobin (oxyHb), reduced hemoglobin and MetHb from our co-oximeter. As the patient had good exercise tolerance and the normal lactate indicated adequate tissue perfusion4 we planned to proceed with surgery. We monitored the patient by measuring serial ABGs through an indwelling arterial line in addition to routine monitors. Anesthesia was induced with fentanyl and propofol. A spontaneously breathing technique with a 1:1 mixture of oxygen/air and isoflurane was used. Intraoperatively, a representative ABG was as follows: pH = 7.47, pO2 = 375 mmHg, pCO2 = 32 mmHg, BE = 0.2; lactate = 1.1 mmol·L–1. The perioperative course was uneventful and the patient was discharged home two days later. Severe MetHb is treated with methylene blue which rapidly reduces methemoglobinemia nonenzymatically.3 The recommended dosage of methylene blue is 1–2 mg·kg–1 iv over a five-minute period. Doses > 15 mg·kg–1 can paradoxically cause methemoglobinemia.1 It is known that methylene blue is ineffective in the presence of nicotinamide-adenine dinucleotide phosphate dehydrogenase and glucose-6 phosphate dehydrogenase deficiencies.1,3 Methylene blue is not effective in the presence of HbM because HbM leads to the formation of an iron-phenolate complex that resists reduction. Co-oximeters are also misleading in the presence of HbM.1 The HbM spectrum lacks the characteristic MetHb peak at 630 nm and has a peak near 600 nm. In the presence of HbM, co-oximeters may report normal fractions of MetHb, increased carboxyhemoglobin (COHb) or increased sulfhemoglobin.1 Our ABG machine (Roche Omni S, Cambridge, UK) failed to record all types of hemoglobin (oxyHb, reduced Hb, MetHb and COHb). We raised this issue with our biochemistry department whose staff concluded that the HbM Saskatoon interfered with the algorithm of the co-oximeter and hence failed to record any form of hemoglobin. The issues raised by this case include failure of methylene blue to treat methemoglobinemia in the presence of HbM and interference of HbM Saskatoon with the algorithm of the co-oximeter. In severe cases of methemoglobinemia with HbM, exchange transfusion or even hyperbaric oxygen5 may have to be considered. The role of ascorbic acid in managing such cases remains uncertain.