Myxedema coma

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Background

  • Hypothyroidism + mental status changes/coma + hypothermia + precipitating stressor[1]
  • Majority of the patients > 60yo[2]
  • Occurs in 0.1% of patients with hypothyroidism
    • Usually occurs after precipitating incident in patient with untreated hypothyroidism [3]
  • Mortality may be as high as 60%[4]
  • Untreated mortality approaches 100% [5]
  • ~50% of cases become evident after admission
  • Severe hypothyroidism may be first time presentation of hypothyroid[6]

Precipitants

Clinical Features

Hypothermia

  • Temperature <35.5°C (95.9°F).

Cardiovascular

Pulmonary

  • Hypoventilation
    • Early respiratory support with intubation is necessary to prevent respiratory collapse
  • Hypercapnia
    • There is often diaphragmatic dysfunction that causes worsening hypoventilation. The dysfunction is reversed after thyroid hormone administration[9]
  • Hypoxia
  • Pleural Effusion
  • Upper airway obstruction from glottic edema, vocal cord edema, and macroglossia can complicate intubation.

Neurologic

  • Altered mental status/Coma due to CO2 narcosis
  • Coma is very rare
  • Pseudomyotonic "hung up" deep tendon reflexes
    • Particularly Achilles reflex
    • Relaxation phase of DTR twice as long as contraction phase
  • Neuropsychiatric symptoms [10]
    • Depression
    • Psychosis

Differential Diagnosis

Evaluation

Work-Up

  • Chemistry
    • Hyponatremia
    • Hpoglycemia
  • CBC
    • Mild anemia
  • TSH, FT4, FT3
  • Blood cultures
  • LFTs
    • Elevated
  • Cortisol level
  • VBG/ABG
    • Hypercapnia
    • Hypoxia
  • Lipid levels
    • Hypercholesterolemia
  • CXR
  • ECG
    • Sinus bradycardia
    • Non-specific ST-T wave changes
    • Prolonged QTc
    • Ventricular dysrhythmias
  • Bedside cardiac US for pericardial effusion

Lab Abnormalities

Management

Respiratory Support

  • Early mechanical ventilation will prevent respiratory collapse and severe respiratory acidosis.

Fluid Resuscitation

  • Often intravascularly depleted
    • May have underlying illness causing dehydration
  • In patients who are hyponatremic, be cautious with rapid correction of hyponatremia
    • Consider fluid restriction
    • Consider hypertonic saline if Na < 120
  • Use D5NS if hypoglycemic

Hypotension

  • Vasopressors will be ineffective without concomitant thyroid hormone replacement

Hormone Replacement

  • Hydrocortisone 100mg q8hr IV since there is also adrenal insufficiency present
    • Alternative: Dexamethasone 2-4mg q12hrs (will not affect cortisol level or ACTH stimulation test)
  • Levothyroxine (T4) (generally agreed upon first line therapy)
    • Dose: 100 to 500 mcg (4mcg/kg IV) followed by 75 to 100 mcg administered IV daily until the patient takes oral replacement.[11]
    • Does require extrathyroidal conversion which can be reduced in myxedema but will have a slow steady onset of action
    • Potentially safer in patients with CAD
    • American Thyroid Association recommends treatment with both T4 and T3[12]
  • T3 20mcg IV followed by 2.5-10mcg q8hr
    • Start with 10mcg if elderly or has CAD
    • Does not require extrathyroidal conversion
    • More rapid onset but may be harmful in patients with CAD

Adrenal Insufficiency

  • Hydrocortisone 100 mg IV for possible concomitant adrenal insufficiency

Hypothermia

  • Treat with passive rewarming
  • Hypothermia will also reverse with thyroid hormone administration
  • Avoid mechanical stimulation
  • Do not actively rewarm:
    • Usually are volume depleted
    • Rapid peripheral vasodilation may induce worsening hypotension

Disposition

  • Admit to ICU

See Also

References

  1. Wall CR. Myxedema coma: diagnosis and treatment. Am Fam Physician. Dec 1 2000;62(11):2485-90.
  2. Davis PJ, Davis FB. Hypothyroidism in the elderly. Compr Ther. 1984;10:17–23.
  3. Thiessen, M. (2018). Thyroid and Adrenal Disorders. Rosen's Emergency Medicine (9th ed.). Philadelphia, PA: Elsevier/Saunders.
  4. Arlot S et al. Myxoedema coma: response of thyroid hormones with oral and intravenous high-dose L-thyroxine treatment. Intensive Care Med. 1991;17:16–8.
  5. Thiessen, M. (2018). Thyroid and Adrenal Disorders. Rosen's Emergency Medicine (9th ed.). Philadelphia, PA: Elsevier/Saunders.
  6. Nicoloff JT et al. A form of decompensated hypothyroidism. Endocrinol Metab Clin North Am. 1993;22:279–90.
  7. Mazonson PD et al. Myxedema coma during long-term amiodarone therapy. Am J Med. 1984;77:751–4.
  8. Thiessen, M. (2018). Thyroid and Adrenal Disorders. Rosen's Emergency Medicine (9th ed.). Philadelphia, PA: Elsevier/Saunders.
  9. Martinez FJ et al. Hypothyroidism. A reversible cause of diaphragmatic dysfunction. Chest. 1989;96:1059–63.
  10. Thiessen, M. (2018). Thyroid and Adrenal Disorders. Rosen's Emergency Medicine (9th ed.). Philadelphia, PA: Elsevier/Saunders.
  11. Smallridge RC. Metabolic and anatomic thyroid emergencies: a review. Crit Care Med. 1992;20:276–91
  12. Jonklaas J, Bianco AC, Bauer AJ, Burman KD, Cappola AR, Celi FS, et al. Guidelines for the treatment of hypothyroidism: prepared by the american thyroid association task force on thyroid hormone replacement. Thyroid. 2014 Dec. 24 (12):1670-751.

Authors:

Ross Donaldson