29
Anaesthesia for ENT, Maxillofacial and Dental Surgery
ENT SURGERY
Special problems are caused when the airway is shared by both anaesthetist and surgeon (Table 29.1). If bleeding is anticipated, the airway must be protected and the oropharynx may be packed to avoid contamination of the larynx with blood, pus and other debris. If a pack is used, it should either be labelled or the tail left obviously emerging from the mouth as a reminder that it must be removed at the end of the operation. The anaesthetic circuit connections are usually hidden under the drapes and may well be ‘knocked’ by the surgeon during the procedure. Anaesthetic disconnections are, therefore, a constant threat. It is important to realize that disconnections on the machine side of the capnograph sampling tube, in a patient who is breathing spontaneously, does not lead to a loss of the capnograph trace and so careful observation of the reservoir bag is mandatory.
TABLE 29.1
Potential Problems Associated with the Shared Airway
Disconnection of tracheal tube
Dislodgement of tracheal tube
Access for surgeon or anaesthetist
Airway soiling
Tube damage, e.g. laser
Lack of visual confirmation of ventilation
Eye care
Tonsillectomy
Surgical access to the pharynx requires the insertion of a Boyle Davis gag. To facilitate this, a secure airway is usually maintained with a ‘south-facing’ moulded tracheal tube (Fig. 29.1). Alternatively, a reinforced laryngeal mask airway (LMA) can be used successfully provided that the surgeon carefully avoids displacement of the LMA during the insertion and removal of the gag.
FIGURE 29.1 Various tubes used in ENT and oromaxillofacial surgery. Clockwise from top left: armoured tracheal tube, south-facing moulded tracheal tube, north-facing moulded tracheal tube, microlaryngoscopy tube, armoured LMA, laryngectomy tube, laser tube.
Rigid Endoscopy and Microlaryngoscopy
Occasionally, the surgeon requires access to the larynx without the presence of a tracheal tube. In this situation, oxygenation can be provided by jet insufflation of the lungs via a subglottic catheter or an attachment to the endoscope (Fig. 29.2). The catheter can be inserted into the trachea either down the endoscope or through the cricothyroid membrane. Anaesthesia is maintained using an intravenous agent, usually propofol.
Nasal and Sinus Surgery
Most nasal procedures in the UK are performed under general anaesthesia and range from simple diathermy of the inferior turbinates to prolonged cosmetic external rhinoplasty. The application of a mixture of topical local anaesthetic agents and other adjuncts (e.g. Moffat’s solution, which is a mixture of cocaine, adrenaline and bicarbonate) provides vasoconstriction before surgery. The airway must be secured to allow the delivery of oxygen and a volatile anaesthetic agent and also to protect the trachea from soiling by blood from the operative site. This can be achieved satisfactorily by the use of a reinforced LMA if there are no specific indications for tracheal intubation such as obesity or the expectation of a prolonged operation. Special attention must be paid to avoid disconnection or occlusion of the breathing system by the surgeon, or soiling of the trachea. Balanced anaesthesia is achieved using increments of a short-acting opioid or a longer-acting drug for prolonged or painful procedures. Careful pharyngeal suction is performed at the end of surgery to ensure the removal of blood and other debris which may have accumulated. The use of a pharyngeal pack is generally unnecessary but, if used, it is vital to ensure that it has been removed before emergence. Serious complications, including death, have been reported after failure to remove a throat pack. The usual principles applying to day-case anaesthesia are adhered to including preoperative assessment and postoperative care (see Ch 26).