You are asked to review a 46-year-old female on the surgical ward who has stridor 4 hours after a total thyroidectomy.
a) List six possible causes for this. (30% marks)
b) You determine intubation is necessary. Outline your approach to securing her airway and justify it.
- airway obstruction secondary to haematoma,
- stridor secondary to hypocalcaemia ( less likely so early)
- airway obstruction due to recurrent laryngeal nerve injury – unilateral versus bilateral,
- post extubation stridor – vocal cord edema
- airway collapse secondary to tracheomalecia if long term goitre
- Anaphlaxis/any other cause examiner is happy with,
Immediate oxygenation measures:
Administer High flow Oxygen / Hudson mask with rebreath bag at 15L. Sitting up position better tolerated than lying flat
Can try Heliox – though to be effective will need 79% Helium, 21% Oxygen mix which may be inadequate if patient has poor gas exchange / pulmonary oedema
Declare Airway emergency – get help: Surgeon, Anaesthetist, Nursing staff
Decide on location for intubation: In ward, theatre or ICU – depending on distance to be moved and patient stability
Decide on and communicate plan of airway intervention including plan for failure: Plans A,B,C highlighting each approach
Ensure Team members are aware of roles & sequence of events and emergency responses
Check Equipment for familiarity and correct function
Be clear about pros and cons of approaches for airway management (Must justify one)
- IV bolus induction – Facilitates rapid airway access but loss of control of airway possible with need for rescue using front of neck access.
- Slow IV propofol infusion induction – maintains respiratory efforts, but familiarity with propofol kinetics and pumps needed.
- Slow Gas induction – maintains respiratory efforts, but an operating theatre and familiarity with anaesthetic machine needed.
- Awake intubation – maintains respiratory efforts, uses local anaesthesia, opiate, sedation avoiding paralysis – not possible in extremis, may hinder adequate view
- Awake Fibreoptic intubation – not appropriate in stridor where scope often obstructs airway inlet in stridorous awake patient.
Outline plan for failure: then front of neck access:
- Scalpel bougie technique (landmarks palpable)
- Midline incision, finger dissect, tracheal access (landmarks impalpable)
Possible causes of stridor in a patient returning from thyroidectomy are more than likely going to be related to the thyroidectomy, or less likely to the drugs which have been given around the time of the thyroidectomy. In any case, it is still probably worthwhile reasoning through this as if it were an exercise in generating differentials:
- Haematoma or pseudoaneurysm (most likely)
- Infection (unlikely)
- Tracheomalacia: an idiopathic cause related to the goitre (Chi et al, 2011)
- Drug-related causes:
- Incomplete reversal of muscle relaxant (i.e. was reversed with neostigmine, which subsequently wore off, leaving behind the for-some-reason-prolonged effects of some long-acting curare toxin)
- Immunological causes:
- Anaphylaxis to a dose of prophylactic antibiotics
- Delayed allergic reaction to drugs given in theatre
- Perforation of the trachea, with subcutaneous emphysema and pneumomediastinum
- Tracheal haematoma due to retraction trauma
- Vocal cord paralysis due to recurrent laryngeal nerve damage
- Vocal cord oedema
- Endocrine and electrolyte abnormalities:
- Extreme hypocalcemia with tetany (known to produce laryngospasm- Scanlon et al, 1985)
To throw a coat of peer-review varnish over this unprofessional gibberish, one could point to an excellent article by Ayandipo et al (2016), which discusses a case series of airway complications from a high-volume ENT service in Nigeria. The most common reason for the reintubation was tracheomalacia, which was observed in something like 5% of the total cases.
Approach to securing the airway is an exercise in demonstrating a level of caution and anxiety to the examiners, so as to give the appearance of a safe practitioner. Specific noises which one needs to make to generate this impression are:
- Unless completely impractical (i.e. patient is blue), insist on doing the reintubation in theatre
- Ideally, invite the surgeon who operated on the patient to join you there, as there is a nonzero chance that they will need to reopen the neck
- Access the services of an airway specialist, ideally an anaesthetist who routinely does ENT and head-and-neck lists
So, the ideal approach here would be:
- In theatre
- Surgeon on standby
- Awake fibreoptic intubation by anaesthetics
However, the college asked for "your approach to securing her airway", not "your approach to avoiding having to handle her airway". Frequently, this scenario plays out after-hours. Consider that a complex total thyroidectomy may take all day, finish at 8pm, and then stridor comes at midnight. One might be working with a skeleton staff and with no theatre available, plus the surgeon is now on his private island and is not inclined to return to the hospital. In short, you're it.
- Assess for difficulty of intubation, to determine which specific features were problematic.
- Assess for difficulty of bag-mask ventilation.
- Look at the most recently available ABG or venous biochemistry: specifically, the PaCO2 helps determine the dose of anaesthetic induction agent, and the serum K+ level helps select the muscle relaxant.
- Decide beforehand what the algorithm is going to be, depending on what is available locally.
- Have a plan for intubation
- Have a plan for oxygenation
- Have a backup plan (or two) for each
- Have a clear idea of what the locally available cricothyroidotomy kit looks like and roughly how long it takes to set up (given that pretty much all of the algorithms lead to cutting the throat).
Preparation of the staff
- Choose a competent assistant to assist with the airway: somebody who knows what BURP is and how to correctly do cricoid pressure
- Choose a competent assistant to give drugs
- Assign a staff member to act as “access”, i.e. somebody to run around and get equipment
- Inform standby staff to be ready (eg. somebody whom you've nominated as the front-of-neck person)
- Discuss the plan with the team to ensure everyone is aware of what is going to happen (eg. “OK people, Plan A is videolaryngoscopy with bougie, Plan B is FONA”).
Preparation of the equipment
- Plan A equipment should be ready for use
- Plan B equipment should be available within 60 seconds (which means, in the room, within arm’s reach, and wherever possible unwrapped and lubricated).
- Drugs should be drawn up, including a couple of adrenaline ampoules in case CPR becomes a part of the rapid sequence induction.
- An end-tidal CO2 monitor should be within reach
- The equipment should be checked, and its operability ensured (i.e. those CMAC batteries better be charged).
Preparation of the patient
- Explain to the patient what the plan is (if they are conscious and capable of processing this information, it would be helpful to have them on your side).
- Commence high flow oxygen
- Preoxygenate for a minimum of 3 minutes. The utility of this is debated.
- During this time, either position the patient for intubation, or (if they cannot tolerate that position) prepare equipment and assistants to put them into that position as soon as the induction is commenced.
Scanlon, Edward F., Stephen F. Sener, and E. Dennis Murphy. "Early onset of tetany following thyroidectomy: report of two cases." Journal of surgical oncology 29.4 (1985): 222-223.
Jeong, Jee Yeon, et al. "Respiratory difficulty at a postanesthesia care unit after total thyroidectomy: a case report." Korean J Anesthesiol 45.4 (2003): 540.
Ayandipo, O. O., T. A. Adigun, and O. O. Afuwape. "Airway Complications and Outcome after Thyroidectomy in Ibadan: A 15 year review." Arch Med 8 (2016): 4.
Law, J. Adam, et al. "The difficult airway with recommendations for management–part 2–the anticipated difficult airway." Canadian Journal of Anesthesia/Journal canadien d'anesthésie 60.11 (2013): 1119-1138.