Introduction

In patients with head and neck cancers, panendoscopy is almost always performed to obtain biopsies and judge the extent of malignant disease in order to determine what mode of treatment is best. It entails a suspension laryngoscopy which allows access to the oropharynx, trachea, and sometime esophagus.

Preparations

In order to allow the surgeon maximum visibility, we use a smaller than normal endotracheal tube. This Micro Laryngoscopy Tube (or MLT tube) comes in sizes 5.0, and 6.0 (inner diameter) and is available in the anesthesia work room. They differ from ordinary endotracheal tubes of the same size in two important respects. First, they are longer so that a size five or six MLT tube when placed to a depth of 18-20 cm at the teeth will still have a significant length of tube outside the mouth to allow connection to the circuit a safe distance away from the mouth. Second, the endotracheal tube cuff is larger than that found on an ordinary 5.0 or 6.0 tube so that a good seal may be obtained in an adult trachea.

In order to provide an immobile field, profound neuromuscular block must be maintained through the end of the case. I have found that the case duration is variable, but that the surgeon will usually have a good idea of how long a particular case will take. For cases of less than one hour duration, I prefer using succinyl choline to intubate and to use a succinylcholine infusion to maintain paralysis. The advantage of such an approach include ready titratability of profound motor block and rapid reversal of NMB by discontinuing the infusion at the conclusion of the case. For longer cases, an intermediate-acting non-depolarizing agent will suffice. I discourage the use of pancuronium for any ENT case where the patient will be extubated at the end.

The bed will be turned 90 ° after intubation toward center well, so it will be most convenient to place the IV in the left hand. Blood loss is minimal, so a 20 g will suffice.

Pre-operative Assessment

Trust no one when it comes to assessing the airway. Trust the surgeons a little bit, but no more. I cannot overemphasize how important it is to communicate with your surgical colleagues about each case, if only during the preceding case, regarding the patients' airway pathology and your plan for managing it. If you include them in your planning, they will be available to help you during induction and you will have a better day for it. Really. As always, have blankets in the room to optimize the patients sniff position prior to induction.

Pre-operative Medications

The goal is to have an awake patient by the end of the case who is able to maintain their own airway and protect it. Use midazolam sparingly. Just as for a fiberoptic intubation, administer glycopyrrolate to dry secretions and make the surgeons job easier by reducing the need for constant suctioning.

Induction

Once an IV induction is planned, I prefer propofol over pentothal. Most panendoscopy patient will be discharged home the same day, and I feel the wakeup is cleaner after propofol. In an effort to blunt the response to suspension laryngoscopy by the surgeons, I will spray the cords and trachea with 4% lidocaine via the LTA when I intubate the patient.

Maintenance

A balanced technique works well. I like to give a narcotic at the beginning. Maintenance can be with inhaled agent or a propofol drip, when appropriate or indicated. Keep the CO2 is the high thirties to allow the rapid return to the patients apneic threshold at the conclusion of the case. Use of nitrous oxide is okay, but don't exceed 50% to give yourself a margin of safety in case of accidental extubation. As you will likely be titrating the level of inhaled agent, keep you flows on the high side (greater than 4 liters total flow) throughout the case. If there will be an apneic portion in the case (for bronchoscopy), be sure to switch the patient to 100% oxygen and confirm that the FiO2 exceeds 80% before you begin apnea. This takes about 18 breaths at normal flows.

Emergence

You will get about a five minute notice from the surgeons before the end of the case. If you're using succinylcholine, simply discontinue to infusion and document the return to full twitch height. If you're using a non-depolarizer, administer reversal agent sufficiently far in advance of planned extubation to allow a normal double burst response (no detectable fade between the first and second stimulus.)

One final point. If the patient had a mass lesion in their oropharynx, or required a awake fiberoptic intubation, consider extubating the patient over a Cook airway exchange catheter.

References

Hendolin, H., M. Kansanen, et al. (1994). "Propofol-nitrous oxide versus thiopentone-isoflurane-nitrous oxide anaesthesia for uvulopalatopharyngoplasty in patients with sleep apnea." Acta Anaesthesiologica Scandinavica 38(7): 694-8.

A randomized prospective study was performed to compare the recovery in 41 patients undergoing uvulopalatopharyngoplasty (UPPP) with either propofol-nitrous oxide-fentanyl or thiopentone-isoflurane-nitrous oxide-fentanyl anaesthesia. The patients were referred to UPPP after examination including polysomnography and otorhinolaryngological examination. The propofol group received propofol 2 mg.kg-1 for induction followed by an infusion of 10 mg.kg-1.h-1 after intubation. The thiopentone-isoflurane group received 5 mg.kg-1 of thiopentone for induction followed by isoflurane (0.5-2%) after intubation. Other medication was similar in both groups. In the propofol group the patients had a significantly better oxygen saturation during the first postoperative hour (P < 0.05), and a higher rate of breathing (P < 0.05), indicating a more rapid recovery of the physiologic control of breathing. Pain as measured by visual analogue score was lower (P < 0.05) during the second postoperative hour compared with the isoflurane group. Apneic episodes occurred with similar frequency in both groups, and they were related to the severity of obstructive sleep apnea (OSA). We conclude that propofol is preferable to thiopentone-isoflurane in UPPP operations, because physiologic respiratory control recovers faster and postoperative pain is less intense.