Chest
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Described are two patients whose initial symptom was acute respiratory failure requiring mechanical ventilation. Initially, the cause of the respiratory failure in each patient was obscure, but diaphragmatic paralysis was subsequently demonstrated fluoroscopically in each case. Further neurologic evaluation then supported the diagnosis of amyotrophic lateral sclerosis. Postmortem examination corroborated this diagnosis.
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In two seriously ill patients, cyanosis developed shortly after a topical anesthetic spray (Cetacaine) was used. In both cases the presence of methemoglobinemia was suggested by a discrepancy between the arterial oxygen tension and the oxygen saturation of hemoglobin, as measured spectrophotometrically. The characteristic responses of the spectrophotometric oximeter to blood containing different concentrations of methemoglobin are described. Physicians administering this topical anesthetic spray (Cetacaine) should be aware of the possible development of methemoglobinemia.