Topical benzocaine (Hurricaine) induced methemoglobinemia during endoscopic procedures in gastric bypass patients.

Abstract

BACKGROUND:

Methemoglobinemia results from oxidation of ferrous to ferric iron in hemoglobin. In addition to a functional anemia, methhemoglobinemia causes the O2-binding affinity of the remaining O2 sites in the hemoglobin tetramer to increase; essentially shifting the oxyhemoglobin dissociation curve to the left and decreasing O2 delivery. Patients develop profound cyanosis unresponsive to O2 when methemoglobin (MHb) levels exceed 10%. It can be lethal if levels exceed 70%. Benzocaine 20% (Hurricaine) spray, commonly used in endoscopy (EGD) can cause methemoglobinemia. We report our experience.

METHODS:

Two patients out of >1,000 EGDs in 4 yrs developed methemoglobinemia.

RESULTS:

Patient 1: 34 F, BMI 46, open distal gastric bypass. Patient 2: 26 F, BMI 49, laparoscopic proximal gastric bypass. Both had nausea and vomiting from stomal stenosis requiring EGD for which benzocaine 20% spray was used. Severe cyanosis (despite pulse oximetry readings of 86% and 89%), dyspnea and tachycardia, were seen within 13 and 7 minutes. They were unresponsive to O2, despite being awake and conversant after complete reversal of sedatives. MHb levels were 35.6% and 18.8% (normal <1%). Patients dramatically improved after 1% methylene blue at 1-2 mg/kg IV over 5 minutes. MHb levels dropped to 2.3% and 0.8 % within 150 and 110 minutes. Neither patient had any evidence of pulmonary embolism or DVT or G6PD deficiency.

CONCLUSION:

Topical benzocaine 20% (Hurricaine) spray used in EGDs gets absorbed and can cause methemoglobinemia. Sprays should be limited to 1 second. Prompt treatment with 1% methylene blue IV can be life-saving.

• Authors: Myur S Srikanth, Richard Kahlstrom, Ki H Oh, S Ross Fox, Earl R Fox, Katherine M Fox
• Journal: Obesity surgery (Obes Surg) Vol. 15 Issue 4 Pg. 584-90 (Apr 2005) ISSN: 0960-8923 [Print] United States
• PMID: 15946444 (Publication Type: Case Reports, Journal Article)

Chemical References

• Anesthetics, Local
• Oxygen
• Methylene Blue
• Benzocaine

Topics

• Administration, Topical
• Adult
• Anesthetics, Local (adverse effects, therapeutic use)
• Benzocaine (adverse effects, therapeutic use)
• Body Mass Index
• Combined Modality Therapy
• Female
• Follow-Up Studies
• Gastric Bypass (adverse effects, methods)
• Humans
• Infusions, Intravenous
• Laparoscopy (adverse effects, methods)
• Methemoglobinemia (chemically induced, physiopathology, therapy)
• Methylene Blue (therapeutic use)
• Obesity, Morbid (diagnosis, surgery)
• Oxygen (therapeutic use)
• Risk Assessment
• Severity of Illness Index
• Treatment Outcome