Term 4 Week 2 (w/c 10/09/2012)
Good morning. Welcome to week 2 of this term’s Gasclass.
You are involved in the care of a 28 year old female who has presented at 38 weeks for elective caesarean section for breech presentation. She is mildly asthmatic and takes a Salbutamol inhaler PRN, otherwise she is well. The surgery is completed uneventfully under spinal anaesthesia.
In the post anaesthetic care unit (recovery room) she becomes agitated. She is running a sinus tachycardia at around 130 bpm and is hypertensive 170/105.
We have had some well thought out suggestions to the above so far. In addition you manage to glean out the following
– She is comfortable & denies being in pain
– There are no signs of hypovolaemia / haemorrhage. (Haemocue is normal)
– Her temperature is 37.6 and she is increasingly intolerant of heat.
What are the possible causes and what other features can you look for to help your diagnosis?
We had some well thought out suggestions yesterday and it is good that people appreciate this kind of scenario is often a diagnostic challenge.
Direct questioning provides you with some further insight. She admits to frequent episodes of heat intolerance and that at times she often feels jittery and has occasional palpitations. You suspect thryoid storm and administer a beta blocker for symptom control. She is also actively cooled toward normothermia & admitted to the HDU. Lab investigation confirm the diagnosis with elevated T3/T4 and low TSH.
Now, assume the patient had an uneventful post operative course but returned again at some point in the future for surgery related to her condition.
What are the perioperative concerns for a patient with thyroid disease?
What is the concern about anaesthetising her. In general terms, what is your plan? We will have a vote tomorrow if there are differing ideas.
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Although we used a bit of artistic license in the way that this case was presented we have tried to cover several of the difficulties that the anaesthetist may face when involved with thyroid surgery.
We firstly encountered thyroid storm. This is a life-threatening syndrome seen in hyperthyroid patients typically 6–24 hours post-operatively, although it may occur intra-operatively. It ischaracterized by hyperpyrexia, tachycardia, hypotension and altered consciousness. It may initially mimic malignant hyperthermia, but is not associated with a severe metabolic acidosis. Other factors such as labour or severe infection may also precipitate the syndrome. Treatment consists of anti-thyroid drugs, Beta blockers, active cooling and IV fluids. Critical care admission may be warranted.
The bulk of the discussion toward the end of the week focused on management of a retrosternal goitre. Problems with a goitre include:
Airway compression: May be worse in supine position, eased on side or prone
Tracheomalacia (especially post-operatively)
SVC: Retrosternal extension Oedematous face and airway Engorgement of nasopharyngeal veins (epistaxis withﬁbre-optic intubation) Poor venous return therefore place i.v. line in lowerextremity (IVC territory)
Recurrent laryngeal nerve: may have involvement pre-operatively. This causes cordadduction leading to a hoarse voice. Bilateral nerve involvement causes stridor.
Symptoms of Dysphagia, positional dyspnoea or stridor should prompt additional investigation including the use of flexible nasoendoscopy to assess cord function aswell as CT scan to confirm the degree of tracheal compression and the point at which it is narrowest.
Some authors state that patients with a mediastinal mass can be classified into three groups according to the clinical symptoms and diagnostic results. The patients are ‘safe’ if they are asymptomatic whereas clear symptoms and positive imaging are assigned in the ‘unsafe’ group. The ‘uncertain’ group is in between the former two categories and comprises of patients with moderate clinical symptoms or asymptomatic but with CT evidence of tracheobronchial tree obstruction (i.e. diameter less than 50% of normal) . It is suggested that adequate staff are on hand prior to induction of anesthesia including the presence of a second anaesthetist and a perfusionist for those patients who are identified as ‘unsafe’ and ‘uncertain’.
It is important to be aware fo the need for close interdisciplinary cooperation in managing this patient, including input from the endocrinologist in optimization of thyroid status. Comprehensive contingency plans on airway management had been developed with the involvement of anaesthetists, a general surgeon, an ENT surgeon and cardiothoracic surgeons. The availability of rigid bronchoscopy with jet ventilation would offer rescue in the event of loss of airway control http://www.ncbi.nlm.nih.gov/pubmed/17670386. Temporary airway stenting via rigid bronchoscopy has also been described in the literature for patients presenting with mediastinal masses. In addition, cardiopulmonary bypass (CPB) would be life-saving during acute cardiorespiratory decompensation and femoral cannulation can be achieved under local anesthesia preoperatively for the ‘unsafe’ patients. Though several authors advocate a primed CPB machine and femoral cannulae in-situ prior to inducing the ‘unsafe’ patients, there are no standard guidelines for management of extracorporeal circulation in the ‘uncertain’ category. It is possible that some anaesthetists would choose to have a perfusionist and primer CPB in the vacinity if the operating theatres.