To the Editor:-Ravindran presented a method for monitoring the surface electrocardiogram (ECG) in patients with extensive burns, in whom it is difficult to obtain a surface ECG signal because of the lack of natural skin and the application of protective ointments that prevent the adherence of ECG pads. His technique does, however, have some limitations in the clinical setting he describes:(1) inability to place electrodes optimally because of involvement in the surgical field, (2) potential loss of electrodes during the surgical procedure, and (3) lack of accessibility, which might limit the ability of the anesthesia care team to replace electrodes. We suggest another monitoring option, the transesophageal pulse oximeter (ESOX[registered sign]) probe (ARISTO Medical, Waukesha, WI), which provides accessibility, is not affected by the surgical procedure, and provides pulse oximetry readings (an ASA-mandated standard for intraoperative monitoring), in addition to temperature and auscultation.
In a recent case report, we presented a patient in whom ESOX[registered sign] was used successfully when peripheral oximetry was unobtainable because of peripheral vascular disease. Atlee and Prielipp have suggested that core organ perfusion is maintained during periods of poor peripheral perfusion, and that ESOX[registered sign] is, therefore, a potentially useful monitor in these patients. It is likely that ESOX[registered sign] would be useful in burn patients such as the one described by Ravindran because core organ perfusion likely would be maintained.
Dorn et al. demonstrated the application of ESOX[registered sign] in a critical care setting. They concluded that ESOX[registered sign] seems to be more reliable than surface pulse oximetry in intensive care unit (ICU) patients, especially in situations of hemodynamic instability. Their findings support the potential usefulness of ESOX[registered sign] in Ravidran's patient.
Atlee et al. [3,6]introduced ESOX[registered sign] and demonstrated a favorable comparison with lingual or rectal oximetry in dogs subjected to desaturation. Prielipp et al. compared ESOX[registered sign] with peripheral surface oximetry in patients undergoing CABG. They found that the ESOX[registered sign] signal was sometimes well preserved when peripheral sensors failed. Dhamee et al. compared ESOX[registered sign] SpO2measurements with simultaneous SaO2measurements (co-oximetry) during clinical desaturation of a patient with alveolar proteinosis undergoing pulmonary lavage; they found comparable, favorable trending during transient desaturations to SaO2values as low as 70%.
In conclusion, we suggest ESOX[registered sign] as a potentially useful monitor in intubated critically ill patients such as the one reported by Ravindran. 
Stanley E. Borum, M.D.
Department of Anesthesiology; Scott & White Clinic and Memorial Hospital; Texas A & M University Health Science Center; Temple, Texas
(Accepted for publication January 20, 1998.)