Question 16

College answer

Syllabus topic/section:

2.1.9 Endocrine Intensive care / Acute Thyroid crises: L1
2.1.9 Endocrine Intensive care / Other thyroid disorders: L2

Discussion:  

This was a simple didactic question. In general, the management section was dealt with well. Many candidates could have been more successful in demonstrating the standard required if detailed and structured answers for the questions on clinical presentation and investigations were given.
For example, a structured answer for part A detailing neurological, respiratory, GIT and cardiovascular signs and symptoms, was required. For Part B, the laboratory investigations required detailing the findings on thyroid function tests with the corresponding laboratory profile (normocytic anaemia, elevated CK, hyponatraemia's, hypoglycaemia, hypercapnia and respiratory acidosis).
The better answers in part C included management of precipitating factors and rationale for use of T3 versus T4.
The rubric is included to aid the candidate's future study.

Domain	Below standard	At standard	Above standard
a) Clinical presentation (3 marks)	Absent or incorrect information 0-1.0 marks	List of symptoms or signs without systemic approach or structure Must include symptoms of at least 3 of the following Systems: cardiovascular, neurological, respiratory or temperature changes. 1.5-2.0 marks	Plus, addition of Systematic approach to clinical manifestations Must include cardiovascular, neurological, respiratory and temperature for full marks. 2.5-3.0 mark
b) Laboratory results (2 marks)	Absent or incorrect information 0-0.5 marks	TSH and T3/T4 Results 1.0 mark	TSH and T3/T4 Results + Other laboratory profile 1.5-2.0 marks
c) Key Principles of Management (5 marks)	Basic Principles of treatment. Lack of details and poor structure Must Include: -Supportive treatment + -Medication therapy without reasoning or incomplete 0-2.0 marks	Basic principles of treatment Must Include: -Supportive treatment + -Medication therapy and reasoning + -Treatment of precipitant 2.5-3.5 marks	In depth principles of treatment Must Include: -Supportive treatment + -Medication therapy and reasoning + -Treatment of precipitant 4.0-5.0 marks

Discussion

"Outline the clinical presentation" has not been asked for this condition before. That the vocabulary term "list" was not used suggests that some additional structure was expected:

a)

Airway features

• Macroglossia
•  Oedema (myxoedema) of the nasopharynx and larynx
• Goitre displacing the airway

Respiratory features

• A "puffy" face, propensity to sleep apnoea
• Reduced hypoxic respiratory drive
• Decreased ventilatory response to hypercapnia

Cardiovascular features

• Bradycardia
• Pericardial effusion
• Cardiogenic shock
• Prolonged PR interval
• Decreased QRS voltages, especially in the limb leads
• Prolonged QT
• Deep T-wave inversions

Neurological features

• Decreased level of consciousness
• Seizures (in up to 25%)
• Psychosis or depression ("myxoedema madness")

Renal consequences

• Bladder atony and urinary retention

Gastrointestinal features

• Anorexia, nausea, abdominal pain
• Constipation,  ileus, all the way to megacolon

Immunological features

• Hypothermia, which masks fever

Other associated examination findings:

• Hypothermia
• Periorbital oedema
• Coarse, sparse hair
• Non-pitting oedema

b) Laboratory investigations and expected results:

• EUC: hyponatremia
• Serum osmolality: hyposmolarity
• BSL: Hypoglycaemia
• CSF biochemistry: normal, except for elevated protein levels
• Serum lipids: high serum cholesterol
• CK: Raised CK (increased muscle permeability)
• ABG: hypoxia and hypercapnia

• FBC: normocytic normochromic anaemia from decreased erythropoiesis 

• TFTs: hypothyroidism, duh. Surely that would not have scored any marks?

c) "Key principles" of management:

• Replace thyroid hormone - preferably IV T3
  • loading dose is 300-400μcg
  • Continue until body temperature and haemodynamics renormalise
  • IV T3 is preferred mostly because of the atonic bowel, where absorption is likely to be erratic. IV T4 has been used as well, but apparently it is less effective because it has lower intrinsic activity. Plus if there is some concurrent illness (an there always is) the T4  is not converted to T3 because of reduced 5′-deiodinase activity. 
• Replace corticosteroids - there is usually a concomitant adrenal insufficiency. One would use a "stress dose".
• Fluid restriction to correct the sodium: this is usually a hypervolemic hyponatremia
• Good solid supportive management:  this appears as an essential element in the rubric and also seemed necessary in the CICM answer to Question 13 from the second paper of 2018, even though it is in no way specific to the management of myxoedema coma. Judging by the allocation of the marks in the rubric, mentioning that the comatose person needs to be intubated would have upgraded your answer 
  • Establish an airway if this is needed
  • Maintain normoxia and normocapnea with the ventilator
  • Maintain normotension to support organ system perfusion, with a catecholamine infusion
  • Correct the Na⁺ deficit - consider using water restriction alone.
  • Correct hypoglycaemia
  • Correct hypothermia with warming blanket
• Underlying cause:  often something like sepsis is in the background.