Critical Hypothyroidism: "Myxedema Coma" Flashcards
What is myxedema coma?
A severe form of decompensated hypothyroidism characterized by progressive cardiovascular, respiratory, and CNS dysfunction, with high mortality if untreated.
Why is myxedema coma often misnamed?
Patients rarely present with true coma despite the severity of the condition.
What are the cardinal symptoms of myxedema coma?
Hypothermia, altered mental status, bradycardia, hypotension, and hypoventilation.
What are key respiratory complications in myxedema coma?
Respiratory muscle weakness, reduced hypoxic ventilatory drive, CO2 narcosis, and pleural effusions impairing ventilation.
What are common myxedematous changes seen in this condition?
Periorbital edema, macroglossia, and dry skin.
What laboratory findings are typical in myxedema coma?
Low T3 and T4, elevated TSH (unless hypothalamic-pituitary dysfunction), anemia, hyponatremia, hypoglycemia, elevated liver enzymes, hypercholesterolemia.
What are common ECG findings in myxedema coma?
Sinus bradycardia, low voltage, and electrical alternans.
How does myxedema coma affect cardiac output?
Reduces cardiac output and stroke volume due to diminished cardiac contractility.
What are imaging findings associated with myxedema coma?
Chest X-ray and echocardiography may show cardiomegaly, pleural effusions, and septal hypertrophy.
What is the role of lumbar puncture in myxedema coma?
To exclude meningitis, which may show elevated CSF protein.
What is the initial IV T4 dose for thyroid hormone replacement in myxedema coma?
200-500 μg loading dose, followed by 50-100 μg daily.
Why is IV T3 used with caution in myxedema coma?
Due to the risk of cardiovascular effects; start with 10-20 μg followed by maintenance dosing.
What is the stress dose of hydrocortisone recommended for myxedema coma?
100 mg/m² IV initially, followed by 25 mg/m² every 6 hours.
Why are corticosteroids given in myxedema coma?
To address possible adrenal insufficiency, which often accompanies severe hypothyroidism.
What supportive care measures are crucial for managing hypothermia in myxedema coma?
Use gradual warming measures to avoid rapid rewarming, which can precipitate cardiovascular collapse.
How should severe hyponatremia in myxedema coma be treated?
With hypertonic saline.
What is the importance of measuring FT4 levels during IV T4 treatment?
To ensure thyroid hormone levels remain within the normal range.
How often should FT4 levels be checked initially when using IV T4?
Twice daily initially, then once or twice per week once stabilized and converted to oral therapy.
What are common complications of untreated myxedema coma?
Respiratory failure, cardiovascular collapse, and multi-organ dysfunction.
When should ACTH stimulation testing be performed in myxedema coma?
After initial stabilization to assess for persistent adrenal insufficiency.
Why are broad-spectrum antibiotics recommended initially in myxedema coma?
To empirically treat potential infections until ruled out.
What are potential cardiovascular complications in myxedema coma?
Severe hypotension, bradycardia, and reduced stroke volume.
What are the key signs of respiratory acidosis in myxedema coma?
Hypoxia, hypercapnia, and altered mental status.
What is the role of vasopressors in myxedema coma management?
To address severe hypotension unresponsive to fluid resuscitation.
What is the mortality risk of untreated myxedema coma?
High, necessitating prompt recognition and intervention.
