Poster Number: tba MetroHealth Medical Center Research Days – Poster Presentation Poster Title: Can Pulse Co-Oximetry Detect Methemoglobinemia In Patients Receiving Cetacaine Spray For Transesophogeal Echocardiography? Authors: Lee Sasala, Karl Wagner MD, Alfred Pinchak MD, Charles E. Smith MD Presenter’s Name: Karl Wagner MD Location of Laboratory: Department of Anesthesia and Department of Cardiology, MetroHealth Medical Center ALL: Please indicate into which category your research belongs: _____ Molecular & Cellular Biology _____ Ion Channels _____ Cardiac Physiology ___x__ Clinical Research _____ Functional Electrical Stimulation _____ Health Care Research Abstract or short description of the poster presentation: (single spaced, 25 lines maximum) Introduction: Methemoglobinemia (MetHb) is an uncommon but serious side effect of the topical local anesthetic benzocaine, the major active ingredient in cetacaine spray. MetHb occurs when the heme groups of hemoglobin are oxidized, making them unable to bind oxygen and ultimately incapable of delivering it to the tissues. MetHb may occur due to overzealous administration of cetacaine during topicalization with resultant morbidity. Signs and symptoms of MetHb are nonspecific and include mental status changes , headache, fatigue, dizziness, and syncope. Although, it is normal to have small amounts (<3%) of methemoglobin, concentrations, >15% can lead to hypoxia. In addition, MetHb can make traditional pulse oximetry readings unreliable. Dangerous MetHb previously could only be diagnosed with laboratory analysis of blood (blood co-oximetry) which is invasive, non-continuous, and subject to delays in reporting. The purpose of this descriptive study was to determine if the pulse co-oximeter can be used to continuously monitor MetHb in patients who received cetacaine spray during TEE. Methods: The protocol was approved by the IRB and written informed consent was obtained. Patients were included in this study if they were over 18 years old and having elective TEE. Topicalization of the oropharynx was achieved with 15 ml of 2% viscous lidocaine and cetacaine spray. IV sedation was with titrated midazolam and fentanyl. Drug dosing and duration of cetacaine topicalization were at the discretion of the cardiology physicians and not affected by the study. Data collected were patient demographics, vital signs, methemoglobin level, and drug doses. TEE procedure duration started at administration of local anesthetic and ended with the removal of the TEE probe. Data was analyzed using min, max, mean, standard deviation, Student’s t-test and correlation analysis. Results: A total of 41 patients were studied. The duration of spray and benzocaine dose varied widely among Cardiology staff. There was no significant difference in benzocaine dose when comparing the 2 methods to calculate dose (duration of spray vs weight, P=0.6, NS). No patient developed hypoxia, and only one patient had a high level of MetHb during the study period. This patient developed a maximum methemoglobin level of 21.8%, had a total spray time of 21 s, and was morbidly obese (weight 178 kg, BMI 63) Discussion: MetHb results in a functional anemia since hemoglobin is incapable of transporting oxygen. MetHb is often caused by benzocaine, but may also be due to other agents such as prilocaine (EMLA cream), lidocaine, nitroglycerin, nitroprusside, nitric oxide, and dapsone. MetHb levels of 20-30% are associated with mental status changes and dizziness, whereas higher levels can result in arrhythmias, seizure, and coma. MetHb > 70% may be fatal. Diagnosis of MetHb in the sedated or anesthetized patient is often delayed, which in turn may delay treatment with methylene blue. The pulse co-oximeter uses seven wavelengths of infrared light to measure the absorption of different hemoglobin species continuously, instantaneously, and noninvasively. The use of more than the traditional two wavelengths of light allows determination of oxygenated and deoxygenated hemoglobin, as well as dysfunctional hemoglobins such as MetHb. This additional information is useful for diagnosing MetHb, and does so in a timely manner without invasive testing. References: 1.Barker SJ, Curry J, Redford D, Morgan S. Measurement of Carboxyhemoglobin and Methemoglobin by Pulse
Oximetry: A Human Volunteer Study. Anesthesiology (2006) 105(5): 892-897.
2.Jaffery Z, Ananthasubramaniam G. A rare side effect of transesophageal echocardiography: methemoglobinemia from topical benzocaine anesthesia. Eur J Echocardiogr (2008) 9(2):289-290.
The needle-nosed turboprop, one of those bend-over-and-walk-down-the-aisle commuter jobs, was the only non-stop from Oakland to Fresno. Doctor Daniel Fazen used the time on board, all of it, to read through Kerry’s case summary. Left alone by the overwhelmed Olympia-Fresno nurses, she had bled nearly to death following a tonsillectomy. The icy prose of the medical narratives did nothing to dimin
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