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A patient with the acquired immunodeficiency syndrome (AIDS) developed severe cyanosis after bronchoscopy (oxygen saturation 34%) from methaemoglobinaemia. This was thought to be due to enhanced absorption of local anaesthetic from the nasopharynx or trachea as a result of candidiasis. The patient responded dramatically to intravenous methylene blue.Severe cyanosis during or after bronchoscopy usually results from hypoxaemia from pneumothorax, pulmonary haemorrhage, or bronchoconstriction. We report a patient with the acquired immunodeficiency syndrome who developed cyanosis as a result of methaemoglobinaemia immediately after bronchoscopy. This was probably due to systemic absorption of the topical anaesthetic used to anaesthetise the nasopharynx (benzocaisk') or the trachea (lignocaine). Case reportA 30 year old man with the acquired immunodeficiency syndrome (AIDS) and chronic oropharyngeal candidiasis underwent bronchoscopy to evaluate new nodular densities on the chest radiograph. He denied recent use of amyl nitrite or other drugs. The nose and nasopharynx were anaesthetised with several sprays of Cetacaine topical anaesthetic (benzocaine 14% and tetracaine 2%). About 10 ml of a 2% solution of lignocaine (lidocaine USP) was given through the bronchoscope to anaesthetise the larynx and major airways. Multiple transbronchial biopsy specimens were obtained and bronchoalveolar lavage was performed without difficulty.Immediately after bronchoscopy the patient became profoundly cyanosed. A chest radiograph showed no new infiltrate or pneumothorax. An arterial blood sample, obtained while the patient breathed ambient air, was chocolate brown in colour. The pH was 7-36, the arterial oxygen tension (Pao2) 11-2 kPa and the arterial carbon dioxide tension (Paco2) 5 9 kPa. Oximetry disclosed an arterial oxygen saturation of 34%. Spectrophotometric analysis of the blood sample indicated that 72% of the circulating haemoglobin was methaemoglobin.Initially the patient appeared quite ill, but he responded

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