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

1. Sepsis
2. Bradycardia and hypothermia
3. Cold exposure
4. Trauma
5. MI
6. CHF
7. CVA
8. GI bleed
9. Metabolic conditions (hypoxia, hypercapnia, hyponatremia, hypoglycemia)
10. Burns
11. Meds: B-blockers, sedatives, narcotics, phenothiazine, amiodarone
12. Medication non-compliance (thyroid meds)

Diagnosis

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

Work-Up

1. Chemistry
2. CBC
3. TSH, FT4, FT3
4. Cultures
5. LFT
6. Cortisol level
7. VBG
8. CXR
9. 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

Differential Diagnosis

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

Treatment

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

1. Admit to ICU
2. Endocrine consult

See Also

• Hypothyroidism
• Thyroid (General)