Syndrome of inappropriate antidiuretic hormone secretion

Syndrome of inappropriate antidiuretic hormone secretion

Anesthetic relevance
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Signs and symptoms
Diagnosis
Treatment
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Syndrome of inappropriate antidiuretic hormone secretion (SIADH) is a condition in which excess anti-diuretic hormone (ADH) - also known as vasopressin - is produced. Downstream effects include 1. retention of excess water which can lead to cerebral edema/seizures/coma/death, 2. hyponatremia which can lead to arrhythmias and - if sodium corrected is attempted - potentially iatrogenic Osmotic demyelination syndrome (OSD)/Central pontine myelinolysis (CPM).

Anesthetic implications

Preoperative optimization

• Evaluate overall sodium trend
  • Most anesthesiologists would consider delaying case if sodium x<130
  • Ideally sodium should be corrected to normal limits or at least stabilized or trending towards correction prior to surgery
    • Uncorrected sodium levels merits discussion with internal medicine and surgery.

Pathophysiology

General Mechanism of Action of ADH

• ADH is a hormone produced by the hypothalamus, then stored and released via the posterior pituitary gland
• ADH is responsible for mechanisms pertaining to water retention via upregulation of aquaporin channels in renal nephrons to increase water re-absorption. ADH's main effect leads to increased fluid volume while decreasing serum sodium concentration and decreasing urinary output volume.

Consequences

Causes

• Cancer
  • Brain tumors
  • Small Cell Lung Cancer
  • Lymphoma
• Central Nervous System
  • Brain Surgery - especially pituitary gland surgery
  • Brain tumors
  • Meningitis
  • Encephalitis
  • Brain trauma

Signs and symptoms