Benzocaine-induced methaemoglobinaemia: a case study

Benzocaine is a widely used topical anaesthetic and has been reported to cause toxic methaemoglobinaemia in otherwise healthy individuals with no predisposing risk factors. This article reports on a rare case of benzocaine-induced methaemoglobinaemia following adenotonsillectomy in a 5-year-old girl. Topical benzocaine was applied orally for the relief of postoperative wound pain on the eighth postoperative day. Two hours after application, generalized cyanosis, mild dyspnoea and some degree of agitation developed. The methaemoglobin level was 38.5%. Treatment with methylene blue was initiated immediately. Symptoms completely disappeared 4 hours after initiation of methylene blue therapy. The further course was uneventful. Therefore, all health professionals should be aware that topical anaesthetics after surgery can induce methaemoglobinaemia in children, even after a prolonged interval, and especially when applied on wound surfaces.