Benzocaine-induced methemoglobinemia: report of a severe reaction and review of the literature.

OBJECTIVE: To report a case of benzocaine-induced inethemoglobinemia and present a review of the related literature. CASE REPORT: An 83-year-old man received benzocaine topical anesthesia 600 mg prior to intubation for resection of a thyroid adenoma. The patient became severely cyanotic after induction of anesthesia. After a negative workup for common causes of cyanosis. blood co-oximetry analysis revealed a methemoglobin concentration of 54.1 percent. Intravenous methylene blue reversed the methemoglobinemia, although delayed recurrence 20 h later necessitated readministration of intravenous methylene blue. The patient developed cardiovascular instability and severe neurologic depression requiring prolonged ventilatory support. DISCUSSION: Methemoglobinemia can result from exposure to a number of drugs including benzocaine. Cyanosis, neurological and cardiac dysfunction may result when methemoglobin concentrations exceed 30 percent. Clinical diagnosis is made on the presentation of cyanosis unresponsive to oxygen administration and a distinctive arterial blood brown color; laboratory confirmation is by cooximetry. Treatment of symptomatic methemoglobinemia is by intravenous methylene blue (1-2 mg/kg) administration. Fifty-four cases of benzocaine-induced methemoglobinemia have been reported in the literature. Intubation, endoscopy/bronchoscopy, and ingestion were the most common procedures in which benzocaine administration produced methemoglobinemia. Infants and the elderly were more likely to develop toxic methemoglobinemia after benzocaine exposure. Other risk factors included genetic reductase deficiencies, exposure to high doses of anesthetic, and presence of denuded skin and mucous membranes. CONCLUSIONS: Because of the potential for severe complications, methemoglobinemia should be corrected promptly in compromised patients and those with toxic benzocaine concentrations. The possibility of masking symptoms during general anesthesia carries special risk of use of this agent in the preanesthesia setting.

The dilemma of the multicystic dysplastic kidney.

Multicystic dysplastic kidney is the most frequent cause of an abdominal mass in the neonate, but controversy continues as to the optimal management of these lesions, since little is known about their natural history. Experience with two complicated cases and a review of reports of retained multicystic dysplastic kidneys suggest that such lesions pose a significant risk to their hosts. Malignancy, reversible hypertension, pain, and mass effect have been associated with retained lesions. Infection is another potential hazard that is frequently cited but poorly documented in the literature. In light of the currently low morbidity and mortality associated with operation and anesthesia in the neonatal period, resection appears to be the treatment of choice for the neonate with a multicystic dysplastic kidney.