Microsoft word - abstract metrohealth fair.doc

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.

Source: http://www.anesthesiawiki.net/metrohealthanesthesia/MHAnes/research/abstracts/sasala09MH.pdf