Anaesthesia

21. Anaesthesia for Laryngectomy

21. Anaesthesia for Laryngectomy Certain lesion s occuring i n the larynx or it s vicinity are amenable to surgica l treat ment . Th e operativ e procedur e ar e frequentl y laryngectom y wit h o r withou t th e block resectio n o f gland s o f neck , o r (a s i n carcinoma o f the epiglottis, pharynx or upper esophagus) a pharyngo-laryngo-oesophagectomy (P.L.O.) . If the lesion have caused respiratory difficulties befor e the operation, a preliminary tracheostomy will most likely, have already been performed. Anaesthesi a and ventilation can then be given through this. However, som e surgeons still prefer performing tha t part of the operation, whic h requires a thorough exposur e an d exploratio n o f the neck, withou t havin g the tra cheostomy tub e (and th e connecting tubin g from th e anaesthetic machine) obstruc t their vie w and interfer e wit h the exposur e an d resection . A n attemp t is , therefore , always made , eve n i n thos e patient s wh o alread y hav e a tracheostomy , t o pas s a suitable oro- or naso-tracheal tube (cuffed) befor e the surgery. However, when this is impossible, the surgeon will have to operate with the tracheostomy an d connection s in situ. If a n endotrachea l tub e ha s bee n inserted , th e patien t remain s supin e wit h a sandbag unde r th e shoulder s an d th e hea d restin g o n a headring . Genera l anaes thesia , with a non-depolarizing muscl e relaxant, oxyge n and nitrou s oxide (using a ventilator fo r IPPV) , i s give n an d supplemente d wit h suitabl e dose s o f a narcoti c analgesic (such as fentanyl) intravenously . The exploration and resection in the neck can then proceed without hindrance . Before the surgeon divides the trachea (and performs a permanent tracheostomy) , he give s th e anaesthetis t on e o r tw o minute s warning . Durin g thi s tim e nitrou s oxide is switched off, pur e oxygen is used for IPP V and ketamine 0.5 mg/kg is given intravenously. Thi s ensures a well-oxygenated patient , wit h sufficien t analgesi a an d narcosis for the ensuing period. The cuff of the endotracheal tube is deflated an d th e tube removed. Th e surgeon the n construct s a new tracheostomy, fixes the edges by suturing t o th e surroundin g ski n an d insert s a steril e Ratclif T type cuffed tracheos tomy tube with a sterile mount. Durin g thi s part o f the procedure (which in highly skilled hand s take s onl y 2- 3 minutes) , th e patien t i s apnei c an d no t ventilated . Because of the pre-oxygenation, no hypoxaemia nor any unto wards signs can usually be detected. Whe n th e tracheostomy tub e and the mount hav e been inserted wit h a special steril e towel placed unde r th e mount, th e anaesthetist re-connect s th e ventilator (which usually stands on the left side near the patient's head) to the mount. Th e sterile towel is now wrapped aroun d th e mount an d th e tubing from th e ventilator . Anaesthesia for Laryngectomy 335 Anaesthesia and IPPV then continue in the usual manner . Ketamine i s preferred fo r thre e reasons: It has fairly goo d analgesi c and narcoti c properties; it does not caus e a drop in B.P.; and there is some bronchodilator effect . From this stage onward, a pharyngo-laryngo-oesophagectomy wil l still require about 1.5-2 hour s of surgery but no unto wards effects o f ketamine have been encountere d on the termination of anaesthesia. If, a s an alternative, halothane i s used in place of ketamine, some of the alveola r space would b e occupied b y halothane vapour instead of oxygen. This would not be of great significance. However, because many patients' pre-operative condition is not too good and there may be some hypoproteinemia and/or hypovolaemia, their reaction t o halothane an d IPP V ma y b e exaggerated an d undesirabl e hypotensio n ma y...