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Asian Intensive Care: problems & solutions
International Intensive Care conference, Hong Kong, November 28th-30th 2007
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ENT anaesthesia

Jason Brooks MBBS, FRCA

Issues

Nasal procedures

Adenoids & tonsils

Bleeding tonsil

Sleep apnoea

Endoscopic & laser surgery of larynx

Laryngectomy

Bronchoscopy

Oesophagoscopy

Upper airway obstruction

Oto-neurosurgery

Myringoplasty

Mastoid surgery

Endolymphatic shunts

Acoustic neuroma

Issues

  • shared airway with potential for soiling of the airway
  • increased incidence of arrhythmias due to glossopharyngeal reflexes
  • remote from patient
  • often extremes of age encountered

Nasal Procedures

Problems

  • polyps - predispose to atopy
  • sleep apnoea ( cf tonsillectomy)
  • # nose - recent head injury / swallowed blood
  • avoidance of bleeding
  • post op airway management - nasal packs & airway bleeding

Reduce Bleeding

  • Cocaine: 2-3 mg/Kg - Moffett's solution (cocaine 10% 1ml + adrenaline 1ml 1:1000 + Na Bic. 2ml 8.4%. Adrenaline: max 100m g/10 min - risk arrhythmia's - especially halothane, hypercapnia and hypertension
  • Ephedrine drops

Technique

  • pre O2 - nasal patency compromised
  • LMA vs ET tube
  • LMA used routinely in many centres, effective barrier against blood and secretions entering the airway. Care should be taken to pack only the postnasal space and oropharynx. Leave until full return of reflexes.
  • vasoconstrictor technique
  • pharyngeal pack
  • 10o head up - ¯ venous ooze
  • protective eye pads
  • laryngoscopy at the end of the procedure to recovery any blood clot, packs and any foreign material which may have been deposited in the oropharynx

Post op

  • NSAIDS
  • Nasal packs

Adenoidectomy & Tonsillectomy

Issues

  • sleep apnoea
  • shared airway
  • airway security in recovery
  • post op bleeding - D and management
  • analgesia
  • LMA

Anaesthesia

Pre-operative

  • NB sleep apnoea
  • +/- EMLA cream
  • FBC, G&S

Operation

  • inhalational or iv induction
  • ET tube vs LMA
  • if intubation +/- muscle relaxation ( common to intubate children without muscle relaxation)
  • head extended, protect eyes & Boyle Davies gag
  • bradycardia can be provoked with a swab in post nasal space
  • measure blood loss in small children
  • aim for rapid return of airway reflexes
  • analgesia - NSAIDS + morphine or im codeine phosphate (1mg/kg)
  • a reinforced LMA is used routinely in some centres. Proposed advantage is a smoother recovery with less obstruction and the avoidance of tracheal intubation. When correctly positioned the cuff should not be visible once the gag is opened to its full extent. Main disadvantage is if the airway is lost, it can be difficult to rectify the situation.

Bleeding tonsil

  • difficult diagnosis - ­ HR, agitated
  • hypovolaemia - difficult to assess if a significant amount of blood swallowed.
  • residual effects of a recent anaesthetic - not only residual narcosis but also minor degree of subglotic oedma
  • full stomach

Management

Pre-op

  • resuscitate. NB hypovolaemia may be profound
  • cross match
  • usual equipment; in addition 2 wide bore suckers must be available. Check anaesthetic chart to discover size of ETT used. Have that size and the 2 sizes smaller ready
  • senior anaesthetist & surgeon available

Induction

  • 2 options
    • inhalational induction in lateral position with tracheal intubation under deep anaesthesia (classical teaching). Problems include hypotension, especially if there is any degree of hypovolaemia and laryngospasm if intubation is attempted too soon, or
    • conventional rapid sequence induction. Dose of induction agent should take into account any residual narcosis, and a failed intubation plan should be prepared in advance.
  • once child has been intubated pass large bore stomach tube to empty stomach
  • extubation should be performed in the lateral position with the child fully awake
  • risk of further re-bleeds

Sleep apnoea

  • symptoms - nocturnal snoring, noising breathing, restless sleep & frequent waking, poor weight gain and often hyperactive
  • problems - due to narrowing of the airway from the nasopharynx to the supraglottis, leads to hypoxia & hypercapnia at night. Long standing sleep apnoea leads to chronic hypoventilation, hypoxia, pulmonary hypertension with RV hypertrophy and ultimately RV failure.
  • investigations:
    • FBC - polycythemia
    • ECG - RVH
    • may need further sleep or cardiac studies

Anaesthetic Management

- centred on airway management and the risk of cardiovascular collapse.

  • pre-operative - no sedatives
  • intra-operative - risk life threatening airway obstruction and cardiac decompensation
  • during induction. No definitive technique of choice ( ET tube + cardiostable)
  • post-op avoid opioid analgesia, intensive monitoring if severe OSA

Endoscopic / Laser surgery of the larynx

Issues:

  • wide age range
  • ASA 1-4
  • difficult intubation / airway
  • anaesthesia airway vs surgical access
  • laryngospasm / coughing
  • elderly + co-existing diseases

Airway options include:

  • intubation - microlaryngoscopy tube 5-5.5, can be difficult access for surgeon
  • tracheal catheter - spontaneous ventilation - 4l/min, danger soiling & inadequate anaesthesia/oxygenation
  • jet ventilation (a) via ventilating laryngoscope, reliant on surgeon. (b) crico-thyroid puncture, high pressure gas / O2 sanders injector, risk barotrauma, need TIVA

LASER

Light Amplification of the Simulated Emission of Radiation

  • monochromic (single wavelength)
  • coherent (all waves in same plane)
  • parallel
  • effect on tissue depends on its wavelength and power density
  • power density = energy / unit area, W/cm2
  • CO2 used in ENT surgery - wavelength = 1060nm
  • Light energy absorbed by all cell tissues, penetrates 200m m, therefore minimal heating surrounding tissues.
  • Risks - explosion, airway fire or ignition of ET tube. Operating personnel - i.e. retinal damage

Precautions

  • ET tubes - stainless steel or PVC coated with teflon or aluminium +/- cuffs filled with saline or foam
  • Airway - FiO2 < 40%, use laser in short bursts & wet swabs ¯ thermal damage
  • Theatre safety - protective glasses, personnel education, warning notices
  • Airway fire management - stop ventilation, disconnect O2, douse water, reintubate & steroids

Complications of Laser surgery

  • short - aspiration, laryngospasm, oedema & stridor
  • medium - bleeding, oedema & stridor
  • long - tissue scaring & hoarseness

Laryngectomy

  • usually performed for recurrence of tumour and patients will therefore have had radiotherapy to the neck before, therefore many have difficult airway or intubation.
  • patients frequently malnourished
  • may last 2-15 hrs with most cases taking about 4 hrs
  • additional monitoring needed - invasive Bp, CVP (long line) and temp
  • heat loss important in prolonged procedures - therefore fluid / body warmers
  • ? hypotensive anaesthesia. If this is used BP should be allowed to rise before wound is closed to ensure that haemostasis is adequate
  • risk of major bleeding, air embolus, pneumothorax
  • carotid sinus stimulation may cause bradycardia, or even asystole, and hypotension
  • involves formation of tracheostomy during procedure if patient does not already have one. Change from ETT to tracheostomy tube intraoperatively.
  • Opioid analgesia required for smooth recovery
  • HDU/ITU for 1 day post-op may be necessary in poor-risk patients

Bronchoscopy

Children:

  • commonest approach in babies and young children is to use volatile agents and spontaneous ventilation. 5.0 ETT fits onto the end of the Storz paediatric bronchoscope and thus allows continued supply of volatile anaesthetics during procedure. NB if bronchoscopy is for removal of foreign body try to avoid positive pressure ventilation as this may result in more distal impaction of foreign body and may lead to an exacerbation of any air trapping distal to foreign body

Adults:

  • Several airway techniques available:
    • relaxant and inflation of lungs intermittently with an entrainment system eg Sanders injector
    • apnoiec technique: ventilate lungs prior to insertion of bronchoscope with oxygen-rich mixture then position suction catheter in trachea and insufflate oxygen
    • high-frequency ventilation via side arm of Storz bronchoscope or via cricothyroid cannula. In latter case it is essential to ensure that there is no sub-glottic extension of tumour as there is a considerable risk of barotrauma if the upper airway is obstructed. Cricothyroid ventilation associated with risk of subcutaneous emphysema, pneumomediastinum and pneumothorax
  • Close co-operation between the surgeon and the anaesthetist required

Oesophagoscopy

  • factors - elderly, malnutrition, dehydration, malignancy, anaemia, ­ risk regugitation & aspiration and low grade chest infection
  • IV induction with suxamethonium for intubation and repeated doses to allow ventilation
  • good relaxation particularly important when scope is being passed through the cricopharyngeal sphincter; this may be impeded by the presence of prominent osteophytes on the spine and stiffness of the neck. Over-inflated cuff of ETT may exacerbate difficulties and temporary deflation may be necessary
  • anatomical proximity of major blood vessels means that smooth anaesthesia and good relaxation of great importance during oesophagoscopy
  • problems - damage to teeth, compression of ET tube, arrhythmias, aspiration, CVS collapse & oesophageal perforation

Upper airway obstruction

Aetiology

Diagnosis

Made mainly on clinical grounds:

  • stridor - inspiratory suggests extrathoracic obstruction & expiratory suggests intrathoracic.
  • tracheal tug
  • paradoxical respiration
  • -/+ difficulty swallowing resulting in drooling
  • sitting forwards
  • apnoea (if complete)
  • children - recession intercostal, supraclavicular and sub-diaphragmatic areas, tachypnoea (60/min infant and >40/min in older child), flaring alae nasi & grunting, impaired ability to feed, restlessness / cyanosis

Management

  • based on securing the airway
  • request presence of ENT surgeons
  • traumatic and infective cases are more likely to progress to complete obstruction over a short period of time. Patient should be taken to theatre urgently, accompanied by a cricothyrotomy kit and someone who knows how to use it without undue delay for investigations
  • options, in order of increasing risk are:
    • awake tracheostomy
    • awake cricothyrotomy
    • awake intubation. Less attractive proposition than in other situations of anticipated difficult intubation because of the risk of precipitating complete obstruction. Conventional laryngoscopy may give a better idea of the anatomy than fibreoptic laryngoscopy. Direct conventional laryngoscopy may be the technique of choice for a foreign body
    • GA with gas induction. If, despite careful manipulation and deepening of anaesthesia, the cords cannot be seen on direct laryngoscopy, or the patient begins to lose his airway while anaesthesia is being induced he should be woken and a tracheostomy performed under local anaesthesia. Although this unpleasant for the patient it is safer than proceeding and the patient is likely to require a tracheostomy post-operatively anyway
    • GA with induction with small dose of IV agent, preferably etomidate or ketamine. Where soft-tissue swellings of infective or neoplastic origin are likely to encroach on and distort the normal anatomy of the upper airway, methods of dealing with "difficult intubation" such as blind nasal intubation following IV induction become fraught with danger as accidental opening of an abscess or haemorrhage may flood the lungs with fluid. In this situation the patient should be intubated awake or a cautious gas induction should be used
      2 important principles if GA is to be attempted:
      • maintain spontaneous ventilation (mask IPPV may precipitate complete obstruction)
      • don't use neuromuscular blockers until airway secured
      • start well down list of options in uncooperative patient. Think twice about an inhalational induction if not skilled at this. Be fully prepared for emergency transtracheal ventilation and have a range of difficult intubation equipment. ENT surgeon should be fully prepared for cricothyrotomy or tracheostomy

Epiglottitis in children

  • Features - commonest 3-6 yrs, marked fever & toxicity. Stridor, drooling and characteristic sitting posture.
  • Maintain sitting position & avoid disturbing the child, induce anaesthesia with inahalational induction / O2 and intubate under direct vision with ENT surgeon standing by to perform cricothyrotomy/tracheostomy. Establish i.v access prior to intubation. Smaller ET tube will be needed & bubbles of saliva may be a valuable clue to the location of the larynx.
  • Blood cultures & antibiotics ( third generation cephalosporin)
  • ITU 24-48 hrs

Epiglottitis in adults

  • Some recommend same approach as in children. However, may be more problematic and awake cricothyrotomy followed by induction of GA may be a better alternative.

Trauma

  • patient with traumatic stridor often has associated head, face and neck trauma. May not co-operate for awake techniques and inhalational induction may produce unwanted movement of head and neck and will exacerbate raised ICP. You may be forced to induce anaesthesia with etomidate or thiopentone and perform either direct laryngoscopy (with head stabilised) or cricothyrotomy and retrograde intubation. Avoid nasal route if there is risk of basal skull fracture. Assume full stomach.
  • adjunctive treatment:
    • helium. Lower density than nitrogen (and oxygen) means that 80% He/20% O2 will flow through an orifice approx. 3 times faster than air. Unclear how useful this really is.
    • nebulised adrenaline may be useful when oedema is the problem

Oto-neurosurgery

Issues:

  • avoidance of bleeding / hypotensive anaesthesia
  • N2O with middle ear grafts
  • Post op N&V
  • Preventing coughing on extubation

Reduction of bleeding

  • To facilitate delicate, intricate surgery safely.
  • Aim is to reduce bleeding at surgical site with maintenance of adequate tissue perfusion,
  • Simple manoeuvres first:
    • avoid atropine
    • deep, smooth anaesthesia - ( isoflurane + opiate)
    • normocapnoea
    • 100 head up tilt + good venous drainage
    • prevent hypotension
  • Pharmacological adjuvants : commonly B-blockers and vasodilators.

Myringoplasty

  • undertaken to repair perforation of tympanic membrane which has not healed spontaneously
  • hypotensive techniques can be helpful as bleeding may be a problem
  • thought that nitrous oxide may be detrimental to the positioning of grafts but air space is reduced so much by packing in the middle ear to support the grafts that it is unlikely to be a problem clinically. With underlay grafts (as opposed to overlay) nitrous oxide likely to be beneficial in keeping graft in place if it has any significant effect at all

Mastoid surgery

  • poses same type of problems to anaesthetist as myringoplasty but is likely to be more prolonged

Endolymphatic shunt operations

  • involves decompression of endolymphatic sac by insertion of a shunt which allows the endolymph to trickle into the CSF
  • anaesthesia is as for an extensive mastoid operation but because of the need to identify structures by drilling into the bony framework haemostasis is even more important
  • muscle is frequently taken from the thigh to pack the mastoid cavity created by surgery

Acoustic neuroma

  • small tumours can be reached by a trans-labyrinthine approach which requires anaesthesia as for a mastoid exploration
  • large tumours require a middle fossa approach and a neurosurgical type of anaesthetic

Further reading

Goldstone JC. Handbook of Clinical Anaesthesia. 1996

Jones GW. Anaesthesia for Laser Surgery in Airway. RCA Newsletter No.49. Nov 1999

Nair I. Review of uses of laryngeal mask in ENT anaesthesia. Anaesthesia, 1995, 50, pp898-900

Warwick J.P Obstructive sleep apnoea syndrome in children. Anaesthesia, 1998, 53, pp 571-579


© Justin Brooks November 1999

 

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