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


CONCLUSIONS
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.
Srikanth
Myur S
MS
Tacoma Surgical Weight Loss Clinic, Tacoma, WA 98418, USA. myursrikanth@yahoo.com
Kahlstrom
Richard
R
Oh
Ki H
KH
Fox
S Ross
SR
Fox
Earl R
ER
Fox
Katherine M
KM
D000287:Administration, Topical; D000328:Adult; D000779:Anesthetics, Local / Q000009:adverse effects / Q000627:therapeutic use; D001566:Benzocaine / Q000009:adverse effects* / Q000627:therapeutic use; D015992:Body Mass Index; D003131:Combined Modality Therapy; D005260:Female; D005500:Follow-Up Studies; D015390:Gastric Bypass / Q000009:adverse effects* / Q000379:methods; D006801:Humans; D007262:Infusions, Intravenous; D010535:Laparoscopy / Q000009:adverse effects / Q000379:methods; D008708:Methemoglobinemia / Q000139:chemically induced* / Q000503:physiopathology / Q000628:therapy*; D008751:Methylene Blue / Q000627:therapeutic use; D009767:Obesity, Morbid / Q000175:diagnosis / Q000601:surgery*; D010100:Oxygen / Q000627:therapeutic use; D018570:Risk Assessment; D012720:Severity of Illness Index; D016896:Treatment Outcome
D000779:Anesthetics, Local; D010100:Oxygen; D008751:Methylene Blue; D001566:Benzocaine