METHEMOGLOBINEMIA IN A PATIENT UNDERGOING GASTROINTESTINAL ENDOSCOPY Anjali Bhutani, Manoop S. Bhutani, and Rajesh Patel

To report a case of methemoglobinemia induced by benzocaine in a patient undergoing gastrointestinal endoscopy.

OBJECTIVE:

CASE SUMMARY: Before undergoing an upper gastrointestinal endoscopy, a 15-year-old girl received 20% benzocaine as a spray, to locally anesthetize the pharyngeal mucosa. Thirty minutes after the endoscopy, the patient suddenly became cyanotic, short of breath, and comatose. She was intubated and transferred to the intensive care unit. Her blood methemoglobin concentration was 54 percent. The patient was treated with intravenous methylene blue. Four hours later she was extubated. She was alert, awake, and asymptomatic. DISCUSSION: This is the fourth reported case of methemoglobinemia induced by benzocaine spray in patients undergoing gastrointestinal endoscopy. Pathways for the formation of methemoglobin in the body are reviewed. Intravenous methylene blue is the drug of choice for this condition, and produces rapid and dramatic reversal of methemoglobinemia.

It is common to use benzocaine spray prior to upper gastrointestinal endoscopy. Benzocaine rarely induces methemoglobinemia in these patients. Prompt diagnosis and treatment with intravenous methylene blue is warranted in such cases.

CONCLUSIONS:

Ann Pharmacother 1992;26:1239-40. PATIENTS UNDERGOING an upper endoscopic examination are frequently subjected to oropharyngeal local anesthesia with 20% benzocaine spray. Benzocaine in various forms is used as a local anesthetic. Rare cases of induction of methemoglobinemia by benzocaine have been reported. loS A literature search using the MEDLINE service revealed three reported cases of methemoglobinemia induced by the use of benzocaine spray prior to an upper gastrointestinal endoscopic procedure.>" We present another case of severe methemoglobinemia induced by 20% benzocaine spray. CASE REPORT A 15-year-old girl was referred by a pediatrician for dyspeptic symptoms. She did not consume alcohol, was a nonsmoker, and had no history of nonsteroidal drug use. Physical examination was unremarkable. An upper gastrointestinal series was normal. ANJALI BHUTANI, M.D.. is a Clinical Instructor of Medicine; MANOOP S. BHUTANI, M.D., is a Clinical Instructor of Medicine; and RAJESH PATEL, M.D., is a Clinical Assistant Professor of Medicine, School of Medicine, Wright State University, Dayton, OH. Reprints: Manoop S. Bhutani, M.D., Department of Medicine, School of Medicine, Wright State University, P.O. Box 927, Dayton, OH 45401.

The patient was started on ranitidine 150 mg po bid on an empirical basis. After eight weeks of ranitidine therapy the patient still remained symptomatic. She was then scheduled to have an esophagogastroduodenoscopy (EGD) as an outpatient. Before the procedure the patient's oropharyngeal mucosa was sprayed three to four times with 20% benzocaine spray and she was also given midazolam 6 mg iv. The procedure was tolerated well by the patient and was uneventful. The EGD revealed esophagitis, a hiatal hernia, and mild gastritis. The patient was transferred to the recovery room in stable condition. About 30 minutes after the procedure, the patient became severely short of breath, deeply cyanotic, and very lethargic. In the next few minutes she became comatose and had a respiratory arrest. The patient was immediately intubated and transferred to the medical intensive care unit where she was put on a ventilator. Arterial blood gases on 100% fractional inspired oxygen concentration on the ventilator were pH 7.5, pe02 26.4 mm, p02 617 mm, oxygen saturation 49 percent, and HCO J 21.6. An immediate blood methemoglobin concentration was 54 percent (normal

Methemoglobinemia in a patient undergoing gastrointestinal endoscopy.

To report a case of methemoglobinemia induced by benzocaine in a patient undergoing gastrointestinal endoscopy...
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