Anaesthesia used in microlaryngoscopy is
C i.e. Pollarad tube with infiltration block When fire breaks out during laser vocal cord surgery, oxygen should be turned off, ventilation stopped, tracheal tube removed and submerged in water and the patient should be ventilated with facemasK. Airway damage is assessed with bronchoscopy and bronchial lavage, steroids, can be used for treatment. Anesthesia for Endoscopic Surgeries of Airway Endoscopy includes laryngoscopy, microlaryngoscopy (i.e. aided by an operating microscope), bronchoscopy & oesophagoscopy. These procedures may be accompanied by laser surgery. Microlaryngoscopic surgeries include biopsy / surgery of laryngeal malignancy, vocal cord polyps etc. It is associated with some specific problems as - common field for anesthetist & surgeon, already reduced glottic opening d/t growth, laryngospasm (mediated by superior laryngeal nerve) d/t laryngeal stimulation, very high chances of aspiration and myocardial ischemia (- 4% due to sympethetic stimulation). Preoperative Considerations - Sedative premedication is contraindicated in any patient with any significant degree of upper airway obstructionQ, d/t fear of aspiration. Glycopyrrolate, 1 hour before surgery minimize secretions, thereby facilitate ventilation. Pethidine & promethazine are only given if there is no airway obstruction. Laser Precautions General laser precautions include wearing protective spectacles to prevent retinal damage and evacuation of toxic fumes (laser plume) from tissue vaporization which may have potential to transmit microbacterial diseases. Greatest fear during laser airway surgery is a tracheal tube fire. This can be avoided by using a technique of ventilation that does not involve a flammable tube or catheter (eg intermittent apnea or jet ventilation through the laryngoscope side po). The potential fuel source should have laser resistant propeies (laser tubes or wrapping a tracheal tube with metallic tape) or be removed (supraglottic jet ventilation technique). The only non inflammable, laser proof tube is the all metal. Noon tube, which has no cuff. Most laser tubes have laser resistant propeies around the shaft, but the cuff is not protected and can ignite. So there are double cuffs to seal the airway- if upper cuff is struck by laser and saline escapes, the lower cuff will continue to seal the airway. No cuffed tracheal tube, or any currently available tube protection is completely laser proof. Therefore, whenever laser airway surgery is being performed with a tracheal tube in place, the following precaution should be observed. - Inspired 02 conc. should be as low as possible may be upto 21% - N20 suppo combustion & should be replaced with air (N2) or heliumQ - Tracheal tube cuffs should be filled with saline dyed with methylene blue to dessipate heat & signal cuff rupture - A cuffed tube will minimize 02 conc. in the parynx. The addition of 2% lidocaine jelly (1:2 mixture with saline) can seal small laser induced cuff leaks, potentially preventing combustion - Laser intensity & duration should be limited as much as possible. - Saline soaked pledgets (completely saturated) should be placed in the airway to limit risk of ignition. - A source of water (60 ml) should be immediately available in case of fire. Muscle Relaxation Profound muscle relaxation is the aim to provide masseter muscle relaxation for introduction of suspension laryngoscope & an immobile surgical field. - Anesthesia is induced with IV induction agent followed by a non depolarizing muscle relaxant; the vocal cords are sprayed with 3 ml lidocaine 4% to assist smooth anesthesia & to minimize the possibility of postextubation laryngospasmQ - Alternatively the cords may be painted with 3% cocaine at the end of procedure, which has the added advantage of reducing bleeding from operative site. Oxygentation & Ventilation - Microlaryngoscopy tubes are long, have a small internal and external diameter, and are designed specifically for endoscopic procedures (but not suitable for laser surgery). Typically 4 to 5 mm internal diameter tubes with high volume, low pressure cuffs are used in nasal or oral versions. The most popular anesthetic technique use a Coplan's microlaryngoscopy tube (5mm ID, 31cm long, 10m1 cuff volume and constructed from soft plastic). It is designed for micro laryngeal surgery or for patient whose airway has been narrowed to such an extent that a normal sized tracheal tube cannot be inseed. The small tube diameter provides better visibility and access to surgical field but may lit incomplete exhalation and occlusion. - Most commonly the patients are intubated with small diameter (4 - 6 mm) tracheal tubesQ; - Standandard tracheal tubes of this size, however, are designed for pediatric patients. They tend to be too sho for adult trachea (in length)Q with a low volume cuff that will exe high pressure against it - A 4 - 6 mm microlaryngea tracheal (MLT) tubes (Mallinckrodt critical Care) is the same length as the adult tube, has dispropoionately large high volume low pressure cuff, and is stiffer and less prone to compression than a regular tracheal tube. - The advantages of intubation include - protection against aspiration, and the ability to administer inhalational anesthetics and enable monitoring of ventilation by capnography and spirometry, by measuring end tidal CO2Q - In some cases (eg those involving posterior commissure), intubation may interfere with surgeon's visualization and then alternatives are: 1.Insufflation of high flows of oxygen through small catheter placed in the trachea 2. Intermittent apnea technique. Jet ventilation through laryngoscope High frequency positive pressure ventilation (HFPPV)
Pollarad tube of 10 mm diameter with heavy sedation
Pollarad tube of 15 mm diameter with topical xylocaine
Pollarad tube with infiltration block
Heavy sedation on and Endotracheal intubation