Methemoglobinemia is a relatively rare, but potentially life-threating medical condition, which may be induced by application of topical anaesthetic agents commonly used during endoscopic procedure. The aim of our study was to assess the influence of
lidocaine used prior to transesophageal echocardiography (TEE) on the blood level of
methemoglobin in vivo. Additionally we attempted to establish the occurrence rate of clinically evident
lidocaine-induced
methemoglobinemia on the basis of data collected in our institution. We retrospectively analyzed patient records from 3,354 TEEs performed in our echocardiographic laboratory over the course of 13 years in search for clinically evident
methemoglobinemia cases. Additionally, 18 consecutive patients referred for TEE were included in the prospective part of our analysis. Blood samples were tested before and 60 min after pre-TEE
lidocaine anesthesia application. Information concerning concomitant conditions and
pharmacotherapy were also obtained. In 3,354 patients who underwent TEE in our institution no cases of clinically evident
methemoglobinemia occurred. In the prospective part of the study, none of 18 patients [16 (89 %) men, mean age 63 ± 13] was diagnosed with either clinical symptoms of
methemoglobinemia or exceeded normal blood concentration of
methemoglobin. Initial mean
methemoglobin level was 0.5 ± 0.1 % with mild, statistically (but not clinically) significant rise to 0.6 ± 0.1 % after 60 min (p = 0.02). Among the analyzed factors only the relation between the
proton pump inhibitors intake and
methemoglobin blood level rise was identified as statistically relevant (p = 0.03). In adults, pre-TEE
lidocaine anesthesia with recommended dosage results in significant increase in
methemoglobin blood level, which however does not exceed normal values and does not result in clinically evident
methemoglobinemia.