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Ovid: Oxford Handbook of Acute Medicine

Editors: Ramrakha, Punit S.; Moore, Kevin P. Title: Oxford Handbook of Acute Medicine, 2nd Edition Copyright ©1997,2004 Oxford University Press (Copyright 1997, 2004 by Punit S Ramrakha and Kevin P Moore) > Table of Contents > Chapter 9 – Endocrine emergencies > Myxoedema coma Myxoedema coma A common precipitant of coma is the use of sedatives, and subsequent hypothermia, in elderly female patients with undiagnosed hypothyroidism. Presentation

  • Altered mental status: disorientation, lethargy, frank psychosis
  • Coma (symmetrical, slow-relaxing reflexes; ~25% have seizures)
  • Hypothermia
  • Bradycardia, hypotension (rare)
  • Hypoventilation
  • Hypoglycaemia.


• U&Es Hyponatraemia is common (50%)
• Glucose Hypoglycaemia may occur
• FBC Normocytic or macrocytic (± coexistent pernicious anaemia) anaemia
• Raised CPK Often with a clinical myopathy
• Thyroid function T4 and TSH
• Cortisol To exclude co-existent Addison’s disease, i.e. Schmidt’s syndrome
• ABG Hypoventilation with ↑PaCO2, ↓PaO2 and acidosis
• Septic screen Blood and urine cultures
• ECG Small complexes with prolonged QT interval
• CXR Pericardial effusion may occur.

Poor prognostic indicators

  • Hypotension. Patients with hypothyroidism are usually hypertensive. ↓BP indicates possible adrenal failure or cardiac disease. Response to inotropes is poor as patients are usually maximally vasoconstricted.
  • Hypoventilation. This is the commonest cause of death in patients with myxoedema coma. The hypoxia responds poorly to oxygen therapy which tends to exacerbate hypercapnoea.


  • Transfer the patient to an intensive care unit. Mortality is up to 30%.
  • Mechanical ventilation should be instituted for respiratory failure.
  • CVP line. Patients are usually hypertensive and hypovolaemic as chronic myxoedema is compensated for by rising catecholamines.
  • Broad-spectrum antimicrobials (e.g. cefotaxime). Bacterial infection is a common precipitant of myxoedema coma.
  • Hypothermia should be treated as on P844: a space blanket is usually sufficient. Rapid external warming can cause inappropriate vasodilatation and cardiovascular collapse.
  • Hydrocortisone (100mg iv tds) until Addison’s is excluded.
  • Institute replacement therapy before confirming the diagnosis.
  • P.589

  • Ideally give 5–20µg iv (slow bolus) tri-iodothyronine (T3) twice daily for 3 days. After a few days treatment, commence oral thyroxine at 25–50µg/day or oral triodothyronine at 20µg bd. Some clinicians start thyroxine at a much higher dose, but this does carry a risk or precipitating cardiac ischaemia. T3 is preferable due to its short half-life and its effect disappears 24–48 hours after it isstopped.
  • If T3 is unavailable use thyroxine, 25–50µg po or via NG-tube daily.
  • Myxoedema coma has a high mortality if inadequately treated.

Precipitants of myxoedema coma

  • Drugs, including sedatives and tranquillizers
  • Infection
  • Cerebrovascular accident
  • Trauma

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