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Difficulty: MediumEndocrinology and Metabolism

A 72-year-old woman is brought to the emergency department by ambulance after being found unresponsive in her home. According to her family, she has a history of hypothyroidism but stopped taking her medications a year ago. On arrival, she is unarousable. Vital signs show a temperature of 34.2∘C34.2^\circ\text{C} (93.6∘F93.6^\circ\text{F}), a heart rate of 46/min46/\text{min}, a blood pressure of 85/50 mm Hg85/50\text{ mm Hg}, and a respiratory rate of 6/min6/\text{min} with shallow breathing. Her oxygen saturation is 82%82\% on room air. Physical examination reveals periorbital puffiness, generalized non-pitting edema, and cold, dry skin. Arrange the following steps in the most appropriate chronological sequence for the acute evaluation and management of this patient.

  1. 1Perform endotracheal intubation and initiate mechanical ventilation.
  2. 2Obtain blood samples to measure baseline serum cortisol, TSH, and free T4 levels.
  3. 3Administer intravenous hydrocortisone.
  4. 4Administer intravenous levothyroxine.

Answer

The correct sequence is: (1) Perform endotracheal intubation and initiate mechanical ventilation, (2) Obtain blood samples to measure baseline serum cortisol, TSH, and free T4 levels, (3) Administer intravenous hydrocortisone, and finally (4) Administer intravenous levothyroxine.
In the presentation of myxedema coma (hypothermia, bradycardia, hypotension, respiratory depression, and altered mental status in the context of untreated hypothyroidism), the absolute first step is the stabilization of Airway, Breathing, and Circulation (ABCs). Endotracheal intubation is necessary for this comatose, hypoxic patient. Next, because the patient requires emergency glucocorticoids, it is vital to draw baseline serum cortisol and thyroid function tests before medications confound the results. Intravenous hydrocortisone must then be administered to empirically cover for potential coexisting adrenal insufficiency (such as autoimmune polyglandular syndrome). Only after glucocorticoids have been given is it safe to administer intravenous levothyroxine, which treats the underlying thyroid hormone deficit without risking an adrenal crisis.

Step-by-Step Solution

1
Assess the patient's respiratory status and airway.
Endotracheal intubation is performed.
The patient is comatose with a respiratory rate of 6/min and severe hypoxia (oxygen saturation 82%). Immediate airway protection and ventilatory support are required as the first step in resuscitation.
2
Obtain baseline diagnostic laboratory studies.
Blood is drawn for TSH, free T4, and serum cortisol.
Diagnostic samples must be collected prior to medical therapy, as administering exogenous hydrocortisone will confound subsequent baseline cortisol measurements needed to diagnose coexisting adrenal insufficiency.
3
Provide empiric glucocorticoid coverage.
Intravenous hydrocortisone is administered.
Patients with severe primary hypothyroidism may have concomitant primary or secondary adrenal insufficiency (e.g., Schmidt syndrome). Cortisol replacement must empirically precede thyroid hormone.
4
Administer definitive thyroid hormone replacement.
Intravenous levothyroxine is given.
Once the airway is secure and adrenal crisis is averted with hydrocortisone, the underlying myxedema coma is definitively treated with thyroid hormone replacement.

Key Concept

Acute management sequence for Myxedema Coma
Estimated Time:1m 30s
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Topics

Endocrinology and Metabolism

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