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Most patients have neither non-pitting oedema known as myxoedema nor coma. The cardinal sign is a deterioration of the patient's mental status from baseline and it is a differential of delirium. Physicians should be alert for myxoedema coma, particularly in elderly women with mental status changes who present during the winter months

About

• Rare but serious complication with high mortality
• First reported in London 1879 by Ord and is very rare indeed

Risk Groups

• Affected people are typically older > 65
• Previously undiagnosed hypothyroidism
• Some may be poorly compliant with medication.
• Commoner in older women x 4

Precipitant

• Heart failure, sepsis, or stroke
• Hypoxia, Hypercarbia
• Sedation, narcotics, amiodarone, lithium

Clinical

• Goitre may be present or a scar to suggest thyroidectomy
• Cool doughy skin, bradycardia, alopecia
• Delirium which is usually hypoactive
• Paralytic ileus, constipation, myxoedema megacolon
• Hypotension - sepsis, cardiac causes
• Elevated diastolic BP early
• Signs of Hypothyroidism (See topic)
• Face swelling, Macroglossia, Ptosis
• Periorbital oedema, coarse, sparse hair
• Hypothermia (as low as 23 C), coma, and seizures.

Investigations

• FBC: anaemia, macrocytosis, raised WCC
• U&E: AKI, Low Na may be seen
• LFTS: often elevated
• CRP: high may suggest sepsis
• TFTS: High TSH and low T4 (low TSH suggest pituitary/hypothalamic disease)
• Blood glucose: low
• CXR:May show infection, effusion, globular heart with pericardia fluid
• ECG: bradycardia, low voltage if effusion, Check QT
• Echocardiogram if pericardial effusion. Tamponade can occur
• CK is usually elevated, Troponin, Lactate
• Blood cultures
• Lumbar puncture: elevated protein and a high opening pressure.
• CT head may be needed to exclude other causes of coma and to exclude precipitants e.g. Stroke or SDH/ICH

The issue of whether myxoedema coma should be treated with LT4 alone or a combination of LT4 plus LT3 is controversial and doses vary between experts. Sometimes they are combined. The available case series suggest higher mortality with initial T4 doses larger than 500 mcg and with T3 doses larger than 75 mcg daily.

Management (Get expert help from Endocrinology)

• Acute Managment ABCDE, IV fluids, Oxygen
  • Close monitoring in HDU/ITU, telemetry, Look for precipitant
  • Hydrocortisone 100 mg IV 6-hourly
  • Treat any hypoglycaemia.
  • IV Antibiotics if sepsis e.g. IV Co amoxiclav 1.2 g IV TDS
• Replacing T3/T4: Doses recommended vary
  • Expert opinions differ about the dose and the preparation (T4 or T3).
  • High doses may precipitate myocardial ischaemia
  • Low dose may be insufficient to reverse a downhill course.
  • Treatment IV if there is a concern that GI absorption may be impaired.
  • Give LT3 (liothyronine) 10–20mcg/12h IV slowly
  • Give LT4 25-50 mcg OD PO/NG/IV but there will be slower conversion to T3.
  • After few days start regular LT4 50 mcg PO which can be slowly increased
• General principles
  • Oxygen for hypoxia
  • Hypoventilation:don't delay intubation and mechanical ventilation too long
  • Hypothermia: blankets, no active rewarming
  • Hyponatremia: mild fluid restriction
  • Hypotension: cautious volume expansion with crystalloid or whole blood
  • Hypoglycaemia: glucose administration
  • Precipitating event: identification and elimination by specific treatment, liberal use of antibiotics
• Prognosis
  • Myxedema is a serious disorder with high mortality.
  • Death from GI bleeding, sepsis, or respiratory failure
  • Poor prognostic factors include advanced age, persistent hypothermia, and altered mental status.

References

• Myxedema and Coma (Severe Hypothyroidism)
• Myxedema Coma: Diagnosis and Treatment