A 67-year-old woman presents from a nursing home with altered mental status. She was last known to be normal the night before. The patient has dementia at baseline and is minimally interactive. This morning, she was found to be obtunded. No further history was provided from the nursing home, and the patient is unable to provide any history. Her temperature is 95.0°F (35.0°C), blood pressure is 84/54 mmHg, pulse is 50/min, respirations are 9/min, and oxygen saturation is 98% on room air. Physical exam reveals an obtunded woman who only withdraws her extremities to pain. Her skin is cool and pale, and her hair is thin. There are no signs of trauma noted on exam. Laboratory values are notable for a whole blood sodium of 120 mEq/L. The patient is given several intravenous boluses of fluids and her blood pressure improves to 100/60 mmHg. Which of the following is most likely to confirm the underlying cause of this patient's symptoms?
Perform an echocardiogram
Administer glucagon
Check serum TSH and free T4 levels
Perform a CT scan of the head
Check serum TSH and free T4 levels
This patient is presenting with obtundation, bradycardia, hypotension, hypothermia, thinning of her hair, and hyponatremia, which are concerning for myxedema coma. A serum TSH and free T4 would be most informative in confirming this diagnosis.

Myxedema coma (decompensated hypothyroidism) is the most life-threatening manifestation of hypothyroidism. Key clinical features include hypothermia (often the temperature is <95.9°F (35.5°C)), bradycardia, hypotension, bradypnea (causing a respiratory acidosis), hypoxia, and obtundation. Immediate management is centered on warming the patient, warmed IV fluids, and protecting the patient's airway, if needed. If there is high clinical suspicion for myxedema coma, then IV levothyroxine can be given empirically. Otherwise, the TSH and free T4 should be checked, which will reveal an elevated TSH and a low free T4. Patients are often critically ill and require active rewarming and close monitoring in an ICU setting.

Wall reviews myxedema coma. Wall notes that myxedema coma is a life-threatening manifestation of hypothyroidism. She recommends that generally IV T4 (levothyroxine) is preferred over IV T3 in initial management.

Incorrect Answers:
Answer A: Administering glucagon would be appropriate in a beta-blocker overdose, which presents with bradycardia, hypotension, and altered mental status. There is no indication that this patient intentionally overdosed, and her hyponatremia and thinning hair supports a diagnosis of hypothyroidism. Other treatments that can be given in a beta-blocker overdose including epinephrine, calcium, insulin, dextrose, and lipid emulsion therapy.

Answer C: Obtaining blood cultures and a serum lactate is the appropriate management of sepsis/septic shock. Generally, patients with septic shock present with hypotension (refractory to fluid resuscitation), tachycardia, and fever or hypothermia. Though myocardial depression may happen in critically ill patients who are about to undergo cardiac arrest, hypothyroidism better explains this patient's constellation of symptoms. It would be appropriate to obtain cultures and a serum lactate in this patient while the differential is being narrowed.

Answer D: Performing a CT scan of the head would be indicated at some point in the workup of patients with altered mental status if there was a suspected central nervous system etiology such as a subdural hematoma. However, hemodynamically unstable patients should never be sent to the CT scanner prior to stabilization and resuscitation. A subdural hematoma is more common in older patients and patients with alcohol use disorder who experience head trauma as the atrophy of their brain makes the bridging veins more vulnerable.

Answer E: Performing an echocardiogram may show reduced cardiac function; however, it is unlikely to reveal the underlying cause of this patient's hypotension and bradycardia other than showing poor cardiac function.

Bullet Summary:
Myxedema coma presents as a critically ill, obtunded patient who is hypothermic, bradycardic, and hypotensive, and the diagnosis can be supported with a high TSH and a low free T4.