To the Editor:—
Esophageal Doppler monitoring is a noninvasive method to determine stroke volume and cardiac output. 1,2So far, it has been used in awake patients or intubated patients. Either the laryngeal mask airway (LMA) cuff made the introduction of the Doppler probe impossible or the fear that the insertion and possible intraoperative movement of the Doppler probe might displace the LMA or increase the risk for aspiration prevented its use. Recently, the LMA-ProSeal ™ (Laryngeal Mask Company, Nicosia, Cyprus) has been made commercially available. 3A comparison with a standard mask did not show any differences in insertion, trauma, or quality of airway. 4The LMA-ProSeal ™ incorporates a port (inner tube diameter: 7 mm for LMA size 5, 6.5 mm for LMA size 4; LMA size 3 is not available with a port) originally designed for insertion of a gastric tube to reduce gastric inflation and reduce gastric regurgitation during longer procedures.
We have inserted the esophageal Doppler probe (Deltex Company, Irving, TX; diameter: 6 mm) through the drainage port of the LMA-ProSeal ™ successfully in 30 patients undergoing general surgery. It is important that the whole of the Doppler probe is well-lubricated to facilitate insertion and movement of the probe during the procedure. After induction of anesthesia and insertion of the LMA-ProSeal ™, the Doppler probe was inserted in all patients in the supine position. The insertion was easily performed through the port of the LMA-ProSeal ™ without displacement of the laryngeal mask. In masks of size 4, a resistance could be felt during insertion of the Doppler probe when passing the curve of the port within the LMA cuff but could easily be overcome and did not obstruct the movement of the Doppler probe. Regardless of the patient position (supine or lateral position), measurements of stroke volume and cardiac output were monitored throughout the procedure in all patients without additional repositioning of the probe. At the end of surgery, the Doppler probe was easily extracted, and the laryngeal mask was removed after the patient was fully awake. We conclude that the drainage port of the new LMA-ProSeal ™ cannot only be used to insert a gastric tube but also to insert the Doppler probe. The LMA-ProSeal ™ allows anesthesiologists to use esophageal Doppler monitoring—something that has previously been impossible.