Myxedema coma

Background

• Hypothyroidism + mental status changes/coma + hypothermia + precipitating stressor
• Majority of the patients will be > 60yo
• Occurs in 0.1% of patients with hypothyroidism
• Mortality may be as high as 60%
• Coma does not need to be present but there will be a decline in the patient's mental status. Sever hypothyroidism may present with severe decompensated hypothyroidism as the first presentation of undiagnosed hypothyroidism
• The classic myxedematous face, which is characterized by generalized puffiness, macroglossia, ptosis, periorbital edema may not be present, but other signs such as a palpaple goiter and thyroid medication use will help in suspecting the diagnosis.

Precipitants

• Bradycardia and hypothermia
• Burns
• CHF
• CVA
• Cold exposure
• GI bleed
• Metabolic abnormalities (hypoxia, hypercapnia, hyponatremia, hypoglycemia)
• Medications: B-blockers, sedatives, narcotics, phenothiazine, amiodarone
• Medication non-compliance (thyroid meds)
• MI
• Sepsis
• Trauma

Clinical Features

Hypothermia

• Temperature <35.5°C (95.9°F).

Cardiovascular

• Bradycardia
• Hypotension

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 thryroid hormone administration
• Pleural Effusion
• Upper airway obstruction from glottic edema, vocal cord edema, and macroglossia can complicate intubation.

Neurologic

• AMS/Coma

Differential Diagnosis

• Adrenal crisis
• CHF
• CVA
• Depression
• Drug overdose
• Hypoglycemia
• Hypothermia
• Meningitis
• Sepsis

Diagnosis

Work-Up

• Chemistry
• CBC
• TSH, FT4, FT3
• Cultures
• LFT
• Cortisol level
• VBG
• CXR
• EKG

Lab Abnormalities

• Abnormal Thyroid Hormone Levels
  • In primary hypothyroidism then TSH will be elevated and T4 and T3 will be low
  • If the patient has secondary hypothroidism (Pituitary dysfunction) the TSH can be low or normal and T4 and T3 will be low
• Anemia
• Elevated CPK
• Elevated creatinine
• Elevated transaminases
• Hypercapnia
• Hyperlipidemia
• Hypoglycemia
• Hyponatremia
• Hypoxia
• Leukopenia
• Respiratory acidosis

Management

Respiratory Support

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

Fluid Resuscitation

• Patients are often intravsascularly depleted and have an underlying infection mandating agressive fluid resususcitation
• In patients who are hyponatremia, be cautious with rapid correction of hyponatremia and choose an appropriate fluid
• Hypoglycemic patients will require intravenous dextrose added into the fluids

Hypotension

• Vasopressors will be ineffective without concomitant thyroid hormone replacement

Hormone Replacment

• Hydrocortisone 100mg q8hr IV since there is also adrenal insufficiency present
• 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.
  • Does require extrathyroidal conversion which can be reduced in myxedema but will have a slow steady onset of action and potentially safer in patients with coronary artery disease (CAD).
• T3
• Dose: 20mcg IV followed by 10mcg q8hr (Start with 10mcg if elderly or has CAD)
• Does not require extrathyroidal conversion and has more rapid onset but may be harmful in patients with severe coronary artery disease.

Hypothermia

• Treat with passive rewarming
• Hypothermia will also reverse with thryoid hormone administration

Disposition

• Admit to ICU

See Also

• Hypothyroidism
• Thyroid (Main)