Hypothyroidism

This covers general considerations of hypothyroidism, myxoedema coma is covered at Myxoedema Coma and sick euthyroid state is covered under Sick Euthyroid State.

Epidemiology and Risk Factors

Pathophysiology

Aetiology

Include:

  • Iodine insufficiency
  • Autoimmune thyroiditis
    • Hashimoto’s Thyroiditis
      Antibodies against peroxidase and thyroglobulin.
  • Treatment of hyperthyroidism
  • Drugs
    • Amiodarone
    • Lithium
  • Pituitary failure

Clinical Features

  • A
    • Goitre
      • Hoarse voice
  • C 8 ↓ HR
    • Postural hypotension
      • Pre-syncope
    • Non-pitting oedema
  • D
    • Depression
    • Obtundation
    • Periorbital oedema
    • Hyporeflexia
  • E
    • Cold intolerance
  • G
    • Constipation
  • I
    • Proximal muscle weakness
    • Dry skin
    • Hair loss
    • Loss of the lateral 1/3rd of the eyebrows
  • O
    • Amenorrhoea

Diagnostic Approach and DDx

Investigations

Bloods:

  • FBE
    • Normochromic, normocytic anaemia
  • UEC
    • ↓ Na+
  • TFTs
    • ↓ T4/T3
    • ↑ TSH
  • Triglycerides
    • Hyperlipidaemia

Management

  • Thyroxine replacement
  • Supportive management

Anaesthetic Considerations

  • A
    • Tracheal compression
      Goitres may impinge on trachea and impede airway management.
  • B
    • Reduced response to ↑ CO2 and ↓ O2
  • C
    • Bradydysrhythmia
    • Diastolic HTN
    • Diastolic dysfunction
    • Abnormal baroreceptor function
    • Contracted plasma volume
  • D
    • Depression
    • Hypoglycaemia
    • Sensitive to anaesthetic agents
  • E
    • Myxoedema coma
      Hypothyroid crisis.
    • Hypothermia
  • E2
    • Addisons disease
      Occurs in 5-10% of patients with severe hypothyroidism.
  • F
    • Hyponatraemia
  • H
    • Anaemia

Marginal and Ineffective Therapies

Complications

Prognosis

Key Studies

References

  1. Bersten, A. D., & Handy, J. M. (2018). Oh’s Intensive Care Manual. Elsevier Gezondheidszorg.