To the Editor:-Previously described methods of replacing the laryngeal mask airway (LMA) with an endotracheal tube have relied on antegrade passage of a Cook airway exchange catheter [1,2]or flexible guidewire, either blindly or with fiberoptic bronchoscope assistance. [3-5]The potential exists for the unsecured distal portion of these devices to become dislodged when passed antegrade into the trachea, either during removal of the LMA or attempted passage of the endotracheal tube. Blind intubation through the LMA also may be complicated by esophageal intubation. Recently, we managed a difficult airway using a combined laryngeal mask airway and retrograde wire technique to facilitate tracheal intubation.
A 33-yr-old, 100-kg man with an uncomplicated medical history presented for exploratory laparotomy. On preoperative anesthetic evaluation of the airway only, one half of the uvula was visible, but the examination was otherwise normal. In the operating room after placement of the standard monitors, anesthesia was induced with fentanyl, thiopental, and succinylcholine. Laryngoscopy failed to permit visualization of the laryngeal structures despite using a variety of types and sizes of laryngoscope blades. A #5 LMA (Gensia) was easily inserted, and adequate ventilation was begun. A 6.0-mm endotracheal tube (ETT) was passed, in its entirety, through the LMA. Fiberoptic bronchoscopy (Olympus LF-1) revealed intralaryngeal placement of the tube cuff. Although the LMA adaptor was removed, the patient's head and neck repositioned, and the volume of air adjusted in the LMA, intralaryngeal ETT cuff inflation remained. Withdrawal of the LMA over a blindly placed tube exchange catheter (Cook) intended to facilitate tracheal intubation resulted in dislodgement of the exchange catheter, necessitating replacement of the LMA. After sterile preparation, the cricothyroid membrane was entered with an 18-gauge introducer needle and a sterile J tip 0.38-inch (0.97-mm) diameter, 110-cm guidewire (Cook Critical Care retrograde guidewire kit, Cook) passed cephalad. Resistance was encountered at the level of the LMA aperture bars, but the wire easily passed with slight manipulation. A 11.0 French Teflon guide catheter (TFE) was threaded ante-grade over the wire into the LMA until skin tenting was noted at the cricothyroid membrane and the LMA removed. An 8.0-mm ETT was passed over the TFE catheter until skin tenting was observed again. A fiberoptic elbow adapter (Portex) was attached to the ETT and connected to a capnograph, to verify placement. The TFE catheter and guidewire were removed, and ventilation was achieved through the endotracheal tube.
The possibility of intralaryngeal or supraglottic ETT cuff positioning after insertion of a standard ETT through the LMA was described previously. [6,7]Suggested solutions to this problem have included the use of the extra-long Mallinckrodt microlaryngeal tube (St. Louis, MO) or Mallinckrodt reinforced tracheal tube, deflation of the LMA cuff and advancement of the ETT and LMA together, insertion of a smaller diameter ETT into the cut end of the primary tube, cutting of the LMA shaft and advancement of the ETT, and use of the shortened version of the LMA, the ST-LMA (Intravent International SA, Henley-on-Thames, England). 
In the case described here, insertion of an extra-long ETT most likely would have prevented this situation from occurring, but, one was not readily available and we were forced to use retrograde intubation to attain satisfactory tracheal intubation. Retrograde intubation is invasive and not without limitations or complications, although one advantage may be that guidewire fixation at the cricothyroid membrane may decrease the likelihood of dislodgement of a tracheal tube passed through a laryngeal mask airway. This technique also might be modified to include the use of a fiberoptic bronchoscope passed antegrade over the guidewire. The combined technique of retrograde intubation via the laryngeal mask airway should be considered another alternative to achieve tracheal intubation through the laryngeal mask airway when conventional methods are unsuccessful.
Susan C. Harvey, M.D., Assistant Professor; Richard L. Fishman, M.D., Assistant Professor; Scott M. Edwards, M.D., Resident, Department of Anesthesia and Perioperative Medicine, Medical University of South Carolina, 171 Ashley Avenue, Charleston, South Carolina 29425-2207.
(Accepted for publication September 23, 1996.)