Document Type

Conference Proceeding

Publication Date

5-1-2026

Abstract

Introduction The overall prevalence of methemoglobinemia is around 0.035%. Methemoglobinemia is a rare but potentially life-threatening complication of local anesthetic use. While all patients are at risk, those with cardiac or pulmonary compromise are more susceptible to developing clinical manifestations. We report a case of acquired methemoglobinemia following topical lidocaine patch application for post-operative pain management in an elderly patient. Case Presentation 84-year-old male with a past medical history of aortic stenosis status post Transcatheter aortic valve replacement, Coronary artery disease, gastrointestinal bleed due to colon polyps, obstructive sleep apnea, chronic kidney disease, trigeminal neuralgia, obesity, essential hypertension, chronic atrial fibrillation, adjustment disorder, chronic diastolic heart failure presented with a chief complaint of worsening diffuse abdominal pain and distension associated with nausea. He also endorsed fatigue and right-sided chest pain. Physical examination was unremarkable except for right upper quadrant abdominal tenderness. Labs were significant for elevated aspartate aminotransferase 206, alanine aminotransferase 199, alkaline phosphatase 477 suggestive of cholestatic injury with biliary tree obstruction. Ultrasound abdomen showed distended gallbladder with sludge and positive Murphy’s sign without evidence of common bile duct dilation. Computed Tomography of abdomen showed colonic diverticulosis and well distended gall bladder. General surgery was consulted and hepatobiliary iminoacetic acid scan was ordered which showed severely delayed or absent radiotracer excretion into biliary system. On day 4, he underwent uncomplicated laparoscopic cholecystectomy. Postoperative pain was treated with muti-modal pain management with IV hydromorphone as needed, oxycodone, Tylenol and 4% Lidocaine patch. He was discharged to inpatient rehab. On day 15, rapid was called in rehab for an episode of desaturation. He was put on Vapotherm but patient remained hypoxic and was eventually intubated and transferred to ICU. ABG obtained at that time revealed a normal partial pressure of oxygen with an elevated methemoglobin level (35.6) confirming the diagnosis of methemoglobinemia. Lidocaine patch was promptly discontinued and the patient was treated with methylene blue, resulting in rapid clinical and laboratory improvement. Glucose-6 phosphatase enzyme levels were within normal limits. Discussion Methemoglobinemia occurs when oxidant stress converts hemoglobin iron from ferrous (Fe2+) to Ferric (Fe3+) state, impairing oxygen-carrying capacity. Lidocaine-induced methemoglobinemia results from metabolic activation via carboxylesterase, CYP2E1 and CYP3A4 pathways. Elderly patients may be at increased risk due to age-related physiological changes and potential cardiac or pulmonary comorbidities. Clinicians should maintain high suspicion for this complication when patients develop unexplained cyanosis following local anesthetic use. Conclusion This case highlights the importance of recognizing methemoglobinemia as a potential complication of topical lidocaine use, even with transdermal patches. Early recognition and prompt treatment with methylene blue are essential for favorable outcomes. Careful consideration of risk factors and monitoring is warranted when using lidocaine-containing products in elderly postoperative patients.

Comments

American College of Physicians Michigan Chapter and Society of Hospital Medicine Michigan Chapter 2026 Resident and Medical Student Day, May 1, 2026, Troy, MI

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