What is the most urgent management for a patient with myxoedema coma (hypothyroidism coma) presenting with confusion, hypoxia, hypercapnia, and hypotension?

Management of Myxoedema Coma

The most urgent management for a patient with myxoedema coma is securing the airway with endotracheal intubation followed by oxygen therapy, then immediate administration of intravenous thyroid hormone replacement (levothyroxine and T3) with concurrent glucocorticoid therapy. 1, 2

Initial Airway Management

• Immediate endotracheal intubation is critical as patients with myxoedema coma often have respiratory depression with hypoxia and hypercapnia 3
• Be prepared for a potentially difficult airway as patients may have posterior pharyngeal edema despite minimal external signs of facial edema 3
• Position the patient with head-up tilt (25-30°) when possible to improve upper airway patency and access 4
• Use waveform capnography to confirm correct endotracheal tube placement 4
• Provide oxygen therapy targeting SpO2 94-98% after securing the airway 4

Thyroid Hormone Replacement

• Administer intravenous liothyronine (T3) immediately as it has a faster onset of action 1
  • Initial dose: 25-50 mcg IV (reduce to 10-20 mcg in patients with known cardiovascular disease) 1
  • Subsequent doses should be administered at least 4 hours apart but not more than 12 hours apart 1
  • A minimum daily dose of 65 mcg/day in the initial days of treatment is associated with lower mortality 1
• Concurrent administration of levothyroxine (T4) is recommended to provide sustained hormone replacement 5

Glucocorticoid Therapy

• Administer glucocorticoids immediately before or concurrently with thyroid hormone replacement 1
• Recommended regimen: dexamethasone 2-4 mg twice daily or hydrocortisone 50-100 mg three times daily 1
• Dexamethasone is preferred as it does not interfere with T4 to T3 conversion and won't affect thyroid function tests 1
• Continue glucocorticoids until adrenal insufficiency is ruled out 1

Hemodynamic Support

• Treat hypotension with intravenous fluid resuscitation (1-2 L of normal saline or lactated Ringer's) 1
• If hypotension persists despite adequate fluid resuscitation, consider vasopressors 1
• Use caution with vasopressors as arrhythmias and circulatory collapse can occur when administered concurrently with thyroid hormones 1

Ventilation Management

• Avoid excessive ventilation; start at 10-12 breaths/min and titrate to target PETCO2 of 35-40 mm Hg 4
• Apply PEEP to reduce atelectasis and improve oxygenation 4
• Monitor arterial blood gases to assess ventilation status and acid-base balance 4

Additional Critical Care Measures

• Maintain normothermia with passive warming (blankets); avoid active external rewarming as it can worsen peripheral vasodilation and shock 1
• Correct hyponatremia if present, but note that it often resolves with thyroid hormone replacement 1
• Screen for and treat precipitating factors such as infection, which is often present in myxoedema coma 1
• Monitor glucose levels closely as hypoglycemia may occur and require correction 2

Ongoing Monitoring

• Continuous monitoring of vital signs, oxygen saturation, and cardiac rhythm 4
• Regular assessment of neurological status 2
• Monitor thyroid function tests (T3, T4, TSH) to assess response to therapy 1
• Transition to oral thyroid replacement only when the patient's clinical condition has stabilized 1

Common Pitfalls to Avoid

• Delaying thyroid hormone replacement while awaiting laboratory confirmation - treatment should be initiated immediately upon clinical suspicion 5
• Failing to administer glucocorticoids concurrently with thyroid hormone replacement, which can precipitate adrenal crisis 1
• Using active external rewarming, which can worsen hypotension through peripheral vasodilation 1
• Underestimating the potential for difficult airway management in these patients despite minimal external signs of edema 3

Remember that myxoedema coma carries a high mortality rate, and prompt recognition with immediate implementation of this treatment algorithm is essential for patient survival 2.