Myxedema Coma| definition, causes, symptoms, diagnosis and treatment

Definition: The term myxedema coma is a misnomer, as myxedema and coma are neither diagnostic criteria nor common presenting findings. A more proper description would be critical hypothyroidism.

Precipitating factors

  • Infections, especially pneumonia, are perhaps the most common precipitating factor.
  • Cardiac events (myocardial infarction, congestive heart failure).
  • Cerebral infarction.
  • Trauma, hemorrhage.
    myxedema-coma
  • Hypothermia, hypoglycemia.
  • Respiratory depression secondary to anesthetics or sedatives.

Clinical findings/ picture

  • Hypothermia
  • Hypotension
  • Bradycardia
  • Mental status depression ( common clinical feature and may progress to stupor or frank coma
  • Hypoglycemia
  • Generalized skin and soft tissue swelling and the presence of cool, dry skin.
  • Periorbital edema , ptosis, macroglossia

Confirmation:

  • The diagnosis is suspected clinically and confirmed with TFT (elevated TSH levels and low levels of free T4 and T3)
  • The degree of TFT abnormalities does not distinguish hypothyroidism from myxedema coma. Rather, the distinction is based on clinical findings. 
  • It is important for the clinician to be able to differentiate hypothyroidism from euthyroid sick syndrome, in which patients have a reduction in both TSH and thyroid hormone levels.

Treatment of Myxedema Coma

  • Thyroid hormone replacement should be given intravenously to ensure rapid restoration of bioactive thyroxine levels and resolution of symptoms
  • High-dose intravenous thyroxine is given as a bolus of 300-500 mcg, followed by 50-100 mcg daily depending on the patient's age, weight, and risk of complications. This method provides a more rapid recovery of symptoms but carries the potential for unwanted cardiac events resulting from the rapid replacement of thyroxine.
  • In the low-dose method, thyroxine 25 mcg is given daily for 1 week followed by a gradually increased dose until the patient is able to resume normal thyroxine orally
  • Regardless of the replacement method used, all patients should be continuously monitored for hypertension and cardiac ischemia.
  • Supportive care should be provided while thyroid hormone levels are replaced. Ventilatory support, passive external rewarming, and correction of underlying electrolyte abnormalities are commonly required. 

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