Thyroid

Myxedema Coma

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Myxedema Coma, Hypothyroid Coma

  • See Also
  • Epidemiology
  1. Incidence: Rare (0.22 per Million persons in U.S.)
  • Pathophysiology
  • Risk Factors
  • Predisposing Events
  1. Cold exposure
  2. Trauma or Burn Injury
  3. Hypoglycemia
  4. Infection (e.g. Pneumonia, Urinary Tract Infection, Sepsis, Influenza)
  5. Levothyroxine withdrawal
  6. Carbon Dioxide retention (e.g. COPD)
  7. Cerebrovascular Accident
  8. Medications
    1. Amiodarone
    2. Anesthesia
    3. Barbiturates
    4. Beta Blockers
    5. Diuretics
    6. Lithium
    7. Opioids
    8. Phenothiazines
    9. Phenytoin
    10. Rifampin
    11. Sedative-Hypnotics (Benzodiazepines)
  • Symptoms
  1. Confusion
  2. Generalized weakness
  3. Apathy
  4. Major Depression
  5. Dyspnea
  6. Weight gain
  7. Abdominal Pain
  8. Constipation
  9. Hoarse Voice (related to laryngeal edema)
  • Signs
  1. See Hypothyroidism
  2. Constitutional
    1. Hypothermia
  3. Head and Neck
    1. Macroglossia (related to mucin and albumin deposits)
    2. Facial edema (possible airway edema)
      1. May appear similar to Angioedema
      2. Generalized facial edema and periorbital edema
    3. Observe for ThyroidGoiter or anterior neck surgical scar
  4. Respiratory
    1. Hypoventilation
    2. Respiratory depression with hypercarbia
    3. Pleural Effusion
    4. Pulmonary edema
  5. Cardiovascular
    1. Percardial effusion
    2. Congestive Heart Failure
    3. Hemodynamic instability
      1. Diastolic pressure increased
      2. Hypotension (late finding)
      3. Bradycardia
    4. Pretibial edema and lower extremity nonpitting edema
  6. Neurologic
    1. Altered Level of Consciousness (Stupor and confusion to coma)
    2. Proximal Muscle Weakness
    3. Prolonged Deep Tendon Reflexes
  7. Gastrointestinal
    1. Myxedema Megacolon (late finding)
    2. Ascites
  • Labs
  1. See Hypothyroidism
  2. Bedside Glucose
    1. Hypoglycemia
  3. Thyroid Function Tests
    1. Normal Thyroid Function Tests may not exclude Myxedema Coma depending on timing of onset
    2. Thyroid Stimulating Hormone (TSH) increased (unless central Hypothyroidism)
    3. Free T4 (Thyroxine) decreased
  4. Serum Cortisol
  5. Complete Blood Count
  6. Comprehensive Metabolic Panel
    1. Hyponatremia
    2. Hypoglycemia
    3. Acute Kidney Injury with increased Serum Creatinine
    4. Liver transaminases increased
  7. Venous Blood Gas
    1. Hypoxia
    2. Hypercapnea
  8. Creatinine Phosphokinase (CPK) increased
  9. Pregnancy Test in women of childbearing age (bHCG)
  10. Consider Lactic Acid and Blood Cultures and infection evaluation (e.g. Urinalysis, Chest XRay)
  • Diagnostics
  • Imaging
  1. Chest XRay
    1. Consider if pursuing suspected infection source
  • Precautions
  1. Consider infection even in the absence of fever
    1. Even in Sepsis, severe Hypothyroidism may prevent fever response
  • Management
  1. ABC Management
    1. Medical emergency with high mortality
    2. Address hypoventilation and airway management
    3. Ventilatory and hemodynamic support
    4. Exercise caution with Rapid Sequence Intubation
      1. Myxedema Coma patients will have little oxygen reserve and may desaturate quickly on intubation attempt
  2. Intravenous Thyroxine (T4)
    1. Administer empirically if suspected (e.g. Hypothyroidism history)
      1. Normal TSH does not exclude Myxedema Coma (e.g. Amiodarone-induced Hypothyroidism)
    2. Standard Protocol (Thyroxine alone)
      1. Thyroxine (T4): 4 mcg/kg up to 200 to 500 mcg IV
    3. Alternative Protocol: Combined T4 and T3
      1. Precautions
        1. T4 alone may not significantly modify Blood Pressure or Heart Rate
        2. Endogenous conversion of T4 to T3 is typically delayed in Myxedema Coma
        3. T3 is however associated with increased risk of precipitating arrhythmia or coronary syndrome
      2. Dosing
        1. Thyroxine (T4) 400 mcg IV over 5-10 minutes AND
        2. T3 10 mcg IV over 5-10 minutes
    4. Monitoring
      1. Observe for Acute Coronary Syndrome and atrial arrhythmias (e.g. Atrial Fibrillation)
      2. Expect stabilization of Hypotension and Heart Rate after Thyroxine administration
        1. Hypothermia and mental status are often slower to respond to Thyroxine
  3. Intravenous Fluids
    1. Administer isotonic crystalloid (NS or LR) as indicated for hypovolemia
    2. Myxedema Coma patients may appear fluid up with third spacing, but they are typically intravascularly dry
      1. Consider monitoring with Inferior Vena Cava Ultrasound for Volume Status
    3. Anticipate reflex vasodilation and Hypotension with rewarming
  4. Rewarming
    1. May treat Hypothermia with Passive Rewarming
    2. However, monitor hemodynamic status carefully, maintain hydration and expect Hypotension
  5. Vasopressors
    1. Hypotension may be refractory to Vasopressors and fluids until Thyroxine has been administered
  6. Endocrinology Consultation
  7. ICU admission
  8. Anticipate electrolyte abnormalities (e.g. Hyponatremia)
  9. Consider empiric antibiotics if infection is considered trigger (even if no fever, esp. if hypothermic)
  10. Consider Stress Dose Corticosteroids (for concurrent suspected Adrenal Insufficiency)
    1. Hydrocortisone 100 mg IV every 8 hours
  • Prognosis
  1. Associated with high risk (30-60% of cases) of cardiovascular collapse or death
  • Complications
  • References