Acute Methoglobinemia After Endoscopy
Acute methemoglobinemia may be caused by topical anesthetics and other oxidizing medications commonly prescribed by Family Physicians. Without knowledge of this potentially lethal condition, delay in diagnosis and treatment is likely. Methemoglobinemia should be considered in any patient presenting with cyanosis, particularly after the use of oxidizing medications.
We describe a case of methemoglobinemia in a patient who presented with cyanosis after endoscopy. This case followed otherwise uncomplicated upper gastrointestinal (GI) endoscopy. The diagnosis was delayed several hours because the physicians treating the patient did not consider the possibility of acute methemoglobinemia.
The patient was a 26-year-old white woman who was sent to the emergency department for evaluation of cyanosis immediately after esophagogastroduodenoscopy. Before the onset of cyanosis, the procedure had been uncomplicated. Benzocaine spray had been applied, and the patient was routinely sedated with meperidine and midazolam. While in recovery, the nurses noted that the patient became cyanotic and mildly short of breath.
The patient was transferred to the emergency department, where she was markedly cyanotic. She was initially given naloxone and flumazenil without improvement in her cyanosis. Her blood pressure was 72/48 mm Hg, and she was tachypneic. Cardiac and pulmonary exams were otherwise unremarkable. Hemoglobin and hematocrit were 12.6 g/dL and 0.384, respectively. The results of a basic chemistry panel were normal. Arterial blood gas on room air showed pH of 7.349, pCO2 was 40.8 mm Hg, pO2 was 97.5 mm Hg, and HCO3 was 21.8 mEq/L. Oxygen saturation (SaO2) by pulse oximetry was 83%. The patient was placed on 100% oxygen, but there was no improvement in the SaO2. A chest radiograph was unremarkable and results of a ventilation-perfusion scan were normal. At that time, a pulmonologist was consulted. He recommended checking a methemoglobin level, which was subsequently found to be elevated at 23.6%.
Because the patient was tachypneic and hypotensive, she was admitted to the intensive care unit and given 90 mg of intravenous methylene blue (2 mg/kg) over 5 minutes. Repeat methemoglobin level 3 hours later was near zero. The patient was discharged the following day in stable condition without any further complications.
Acute methemoglobinemia may be caused by topical anesthetics and other oxidizing medications commonly prescribed by Family Physicians. Without knowledge of this potentially lethal condition, delay in diagnosis and treatment is likely. Methemoglobinemia should be considered in any patient presenting with cyanosis, particularly after the use of oxidizing medications.
We describe a case of methemoglobinemia in a patient who presented with cyanosis after endoscopy. This case followed otherwise uncomplicated upper gastrointestinal (GI) endoscopy. The diagnosis was delayed several hours because the physicians treating the patient did not consider the possibility of acute methemoglobinemia.
The patient was a 26-year-old white woman who was sent to the emergency department for evaluation of cyanosis immediately after esophagogastroduodenoscopy. Before the onset of cyanosis, the procedure had been uncomplicated. Benzocaine spray had been applied, and the patient was routinely sedated with meperidine and midazolam. While in recovery, the nurses noted that the patient became cyanotic and mildly short of breath.
The patient was transferred to the emergency department, where she was markedly cyanotic. She was initially given naloxone and flumazenil without improvement in her cyanosis. Her blood pressure was 72/48 mm Hg, and she was tachypneic. Cardiac and pulmonary exams were otherwise unremarkable. Hemoglobin and hematocrit were 12.6 g/dL and 0.384, respectively. The results of a basic chemistry panel were normal. Arterial blood gas on room air showed pH of 7.349, pCO2 was 40.8 mm Hg, pO2 was 97.5 mm Hg, and HCO3 was 21.8 mEq/L. Oxygen saturation (SaO2) by pulse oximetry was 83%. The patient was placed on 100% oxygen, but there was no improvement in the SaO2. A chest radiograph was unremarkable and results of a ventilation-perfusion scan were normal. At that time, a pulmonologist was consulted. He recommended checking a methemoglobin level, which was subsequently found to be elevated at 23.6%.
Because the patient was tachypneic and hypotensive, she was admitted to the intensive care unit and given 90 mg of intravenous methylene blue (2 mg/kg) over 5 minutes. Repeat methemoglobin level 3 hours later was near zero. The patient was discharged the following day in stable condition without any further complications.