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Department of Anesthesiology and Clinical Research Institute, Seoul National University Hospital, Seoul National University College of Medicine Seoul, Korea
To the Editor:
I read with interest the article by Ng et al. (1) regarding induction of anesthesia and insertion of a laryngeal mask airway (LMA) in the prone position. Some earlier reports on the placement of LMA in the prone position should be cited as references (2,3) . In the figure, the anesthesiologist does not wear gloves, which may harm the relevant physician. The standard precautions for health-care workers should be taken during all encounters with patients. Additionally, the LMA cuff does not appear to be adequately collapsed. This practice may produce soft tissue trauma to the airway, induce laryngospasm and/or push down the epiglottis (4). In addition, the LMA does not appear to be secured, which may lead it to dislodge due to gravity and cause it to be squeezed up out of the pharynx when nitrous oxide diffuses into the cuff. Lastly, if properly oxygenated, ventilation via a face mask is not necessary during anesthesia induction with propofol without the use of muscle relaxants (2,3,5,6) . Both apnea and airway obstruction, the main disadvantages of propofol, can be overcome with the insertion of an LMA (5,6) . Thus, I do not think that ventilation via a mask should be performed before LMA insertion especially in the awkward prone position because LMA itself can provide a better airway, with respect to ventilation and oxygenation, than a conventional mask and oropharyngeal airway (7,8) .
During LMA insertion in the prone position, keeping the neck flexed and the head extended does not seem to be needed because the tongue falls anteriorly by gravity (1,3) , and the head may be slightly turned to the side (1) or extended (2,3) . Besides, LMA can be inserted in the same way as recommended in the supine position except that we may grasp it with the aperture facing the intubator. While inflating the cuff, we should hold the LMA passively to prevent it from being withdrawn by the weight of LMA and anesthetic hosing and to yield to a small outward movement during cuff inflation. A spare trolley should be available to move the patient to a supine position in case of airway emergency (1,3) . However, patients may be allowed to recover in the prone position until the return of reflexes allows removal of the LMA (2).
References
University Department of Anaesthesia, Critical Care & Pain Management, University Hospitals of Leicester, Leicester, England
In Response:
Thank you for the opportunity to reply to Dr. Bahk’s letter.
The previous references (1,2) noted by Dr. Bahk on insertion of the LMA in the prone position are in the correspondence section of Anaesthesia and do not provide any information on technique; consequently we did not think that they were worthy of citation.
The technique described in our paper (3) did not require insertion of fingers into the patient’s mouth; contact with body fluids is therefore unlikely and so wearing gloves may be considered optional.
It is well known that any instrumentation of the airway in general anesthetic practice may cause soft tissue trauma and induce laryngospasm. One of the purposes of submitting our paper for publication was to show that problems with the airway were minor and easily corrected.
Dr. Bahk seems to be concerned that the LMA was not secured in position. However, it was not absolutely necessary to tie the LMA in position because, in the prone position, the proximal end of the LMA and the connector were supported by the operating table.
We draw Dr. Bahk’s attention to the fact that all our patients were properly oxygenated. We did not have difficulty ventilating the lungs manually in the prone position and this is an important item of information for any anesthesiologist who might contemplate inducing anesthesia with the patient in the prone position. We would remind Dr. Bahk that the tongue falls forwards with gravity in the prone position, thereby opening up the posterior oropharyngeal space for the LMA. Thus, maintenance of the airway and insertion of the LMA were straightforward.
We disagree with Dr. Bahk’s comment concerning the position of the head and neck. Whether or not the tongue falls forward with gravity, the head and neck should always be in an optimal position for insertion of an airway device; this is a hallmark of good anesthetic practice.
References
This article has been cited by other articles:
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  S. M. Neustein Mirror-Guided Tracheal Intubation Anesth. Analg., May 1, 2007; 104(5): 1293 - 1294. [Full Text] [PDF]
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