Critical Hypothyroidism: "Myxedema Coma"

Question 1

What is myxedema coma?

Answer 1

A severe form of decompensated hypothyroidism characterized by progressive cardiovascular, respiratory, and CNS dysfunction, with high mortality if untreated.

Question 2

Why is myxedema coma often misnamed?

Answer 2

Patients rarely present with true coma despite the severity of the condition.

Question 3

What are the cardinal symptoms of myxedema coma?

Answer 3

Hypothermia, altered mental status, bradycardia, hypotension, and hypoventilation.

Question 4

What are key respiratory complications in myxedema coma?

Answer 4

Respiratory muscle weakness, reduced hypoxic ventilatory drive, CO2 narcosis, and pleural effusions impairing ventilation.

Question 5

What are common myxedematous changes seen in this condition?

Answer 5

Periorbital edema, macroglossia, and dry skin.

Question 6

What laboratory findings are typical in myxedema coma?

Answer 6

Low T3 and T4, elevated TSH (unless hypothalamic-pituitary dysfunction), anemia, hyponatremia, hypoglycemia, elevated liver enzymes, hypercholesterolemia.

Question 7

What are common ECG findings in myxedema coma?

Answer 7

Sinus bradycardia, low voltage, and electrical alternans.

Question 8

How does myxedema coma affect cardiac output?

Answer 8

Reduces cardiac output and stroke volume due to diminished cardiac contractility.

Question 9

What are imaging findings associated with myxedema coma?

Answer 9

Chest X-ray and echocardiography may show cardiomegaly, pleural effusions, and septal hypertrophy.

Question 10

What is the role of lumbar puncture in myxedema coma?

Answer 10

To exclude meningitis, which may show elevated CSF protein.

Question 11

What is the initial IV T4 dose for thyroid hormone replacement in myxedema coma?

Answer 11

200-500 μg loading dose, followed by 50-100 μg daily.

Question 12

Why is IV T3 used with caution in myxedema coma?

Answer 12

Due to the risk of cardiovascular effects; start with 10-20 μg followed by maintenance dosing.

Question 13

What is the stress dose of hydrocortisone recommended for myxedema coma?

Answer 13

100 mg/m² IV initially, followed by 25 mg/m² every 6 hours.

Question 14

Why are corticosteroids given in myxedema coma?

Answer 14

To address possible adrenal insufficiency, which often accompanies severe hypothyroidism.

Question 15

What supportive care measures are crucial for managing hypothermia in myxedema coma?

Answer 15

Use gradual warming measures to avoid rapid rewarming, which can precipitate cardiovascular collapse.

Question 16

How should severe hyponatremia in myxedema coma be treated?

Answer 16

With hypertonic saline.

Question 17

What is the importance of measuring FT4 levels during IV T4 treatment?

Answer 17

To ensure thyroid hormone levels remain within the normal range.

Question 18

How often should FT4 levels be checked initially when using IV T4?

Answer 18

Twice daily initially, then once or twice per week once stabilized and converted to oral therapy.

Question 19

What are common complications of untreated myxedema coma?

Answer 19

Respiratory failure, cardiovascular collapse, and multi-organ dysfunction.

Question 20

When should ACTH stimulation testing be performed in myxedema coma?

Answer 20

After initial stabilization to assess for persistent adrenal insufficiency.

Question 21

Why are broad-spectrum antibiotics recommended initially in myxedema coma?

Answer 21

To empirically treat potential infections until ruled out.

Question 22

What are potential cardiovascular complications in myxedema coma?

Answer 22

Severe hypotension, bradycardia, and reduced stroke volume.

Question 23

What are the key signs of respiratory acidosis in myxedema coma?

Answer 23

Hypoxia, hypercapnia, and altered mental status.

Question 24

What is the role of vasopressors in myxedema coma management?

Answer 24

To address severe hypotension unresponsive to fluid resuscitation.

Question 25

What is the mortality risk of untreated myxedema coma?

Answer 25

High, necessitating prompt recognition and intervention.