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.
- 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.