Anaesthesia

18. Anaesthesia for Ear, Nose, Throat and Eye Operations

18. Anaesthesia forEar, Nose, Throat and Eye Operations Operations aroun d th e ear s d o no t pos e an y particula r problems , provide d th e patient's airway is carefully maintaine d and respiration is not depressed during adequate anaesthesia, so that coughing and straining are avoided. However, operations for nose and throat surgery present an additional problem (similar to dental surgery) that both the surgeon and the anaesthetist have to compete for the confined space of the patient' s mouth , throa t and , sometimes , eve n th e airway . Operation s o f thi s nature have a tendency to haemorrhage and also nausea and vomiting. Thus an early return of the protective cough reflex is particularly important. Mastoidectomy and Myringotomy Mastoidectomy patients may be toxic, feverish ancfhave respiratory tract infection. Children have specially to be guarded against hyperpyrexia. Atropine pre-operatively and diethy l ether ar e bette r avoide d i n thes e cases. If th e operation i s performe d under general anaesthesia using spontaneous respiration, it is advisable to spray the larynx with a topical analgesic prior to endotracheal intubation, so that movement of the head will then not be so liable to cause coughing or straining. Light general anaesthesia with muscle relaxants and IPPV is recommended. Myringotomy and insertion of grommets in children may be carried out without an endotracheal tube, using nitrous oxide, oxygen and an adjuvant (such as halothane) by face mask. Middle Ear Surgery This is often intricate . The patient must be completely immobile and meticulous attention must be paid to having an unobstructed airway, no straining, and adequate oxygenation and elimination of carbon dioxide. If moderate hypotension is required, this can be achieved by the use of halothane. More profound degrees of hypotension will need appropriate measures (see under induced hypotension). Some surgeons like to use pledgets of cotton wool soaked in adrenaline. In such cases halothane, trichloroethylene an d cyclopropan e shoul d no t b e used (du e t o sensitizatio n o f th e heart—cardiac dysrhythmias) . Nitrou s oxid e shoul d b e turne d of f som e minute s before the middle ear is closed so as to prevent it from accumulating under the flap. Anaesthesia for Ear, Nose, Throat and Eye Operations 307 Ultrasonic irradiatio n o f th e labyrint h ha s becom e popula r i n th e treatmen t o f those patients with Meniere' s disease who have not responde d t o treatmen t b y con servative means . I t i s essentia l i n thes e operation s tha t an y ocula r deviatio n an d nystagmus can be observed during the ultrasonic radiation. I t is also very importan t to ensur e th e integrit y o f th e facia l nerv e b y constan t observatio n o f th e facia l muscles. Nausea and vertigo during the procedure may not only be distressing to the patient, bu t ma y als o seriousl y interfer e wit h th e operation . Th e irradiatio n itsel f must b e performe d wit h th e patien t bein g conscious . I t is , therefore , necessar y t o explain beforehan d th e procedure and aquain t th e patient wit h what t o expect. Pre operative medication usually consists of atropine 0.6 mg and prochlorperazine (stem etil ) 12. 5 mg. The latter drug is given for it s properties against nause a and vertigo. Nasal Operations Nasal operation s (suc h a s Cauldwell-Luc , adenoidectomy , dacryocystorhinos tomy o r -plasty , an d fo r th e correctio n o f deviate d nasa l septum ) ma y b e accom panied b y considerabl e bleedin g an d thu s requir e a techniqu e ensurin g maximu m protection o f the airway. As adenoidectomies are often don e at the time of tonsillectomy , similar anaesthetic techniques are suitable. For other nasal operations a cuffe d endotracheal tub e (preferabl y o f th e non-kinkin g kind ) i s used. I n man y instances , the nasopharynx is also packed with gauze roll (soaked in glycerine or saline). Liquid paraffin shoul d b e avoided fo r soaking . Some surgeons, in addition, lik e to infiltrat e the operatio n are a wit h solution...