Syndrome of inappropriate antidiuretic hormone secretion

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Syndrome of inappropriate antidiuretic hormone secretion
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Anesthetic management

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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.

Intraoperative management

  • Serial ABG to monitor serum sodium
    • concern for overly rapid correction - potentially leading to OSD or CPM.
      • Maintain sodium correction to 0.5mmol/L/hr with goal of 4-8mmol/L in 24 hours[1]
  • Avoid hypotonic fluids
    • half normal saline
    • dextrose in water
    • LR - can consider but requires very close monitoring of sodium levels
  • Preferred fluids
    • Hypertonic saline

Postoperative management

Related surgical procedures

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
    • Hypopituitarism
    • Stroke
  • Guillain-Barre
  • Heart Failure
  • Lung Pathology
    • Pneumonia
  • Medications
    • SSRIs
    • Anti-neoplastic drugs
    • Anti-psychotics
  • Acute stressors
    • pain
    • Nausea
  • Hypothoridism
  • HIV infection

Signs and symptoms

Siadh vs di vs cerebral salt wasting.png

Symptoms

  • Cerebral
    • Altered mental status
    • Seizures
    • Loss of balance/coordination
    • Coma
  • GI
    • Nausea
    • Emesis
  • Musculoskeletal
    • Muscle cramps
    • Muscle weakness

Diagnosis

  • Hyponatremia (serum) x< 135 mEq/L
  • High urine osmolality: 100+ mOsm/kg
  • High Urine sodium levels 40+ mEq/L
  • Euvolemic or fluid overload state

Treatment

  • Overall treatment is to remove excess water from the body
  • Diuretics
  • H20 restriction
  • Demeclocycline (off-label)
    • a tetracycline antibiotic that is used off-label to treat SIADH by decreasing renal response to ADH
  • Treat inciting etiology

Epidemiology

Risk factors for SIADH

  • Increasing age
  • Hospitalization
  • Lung cancer
  • Cerebral pathology/manipulation

References

[2]

  1. "The Resuscitationist's Approach to Severe Hyponatremia". www.acep.org. Retrieved 2025-06-29.
  2. Leung, Alexander A.; McAlister, Finlay A.; Rogers, Selwyn O., Jr; Pazo, Valeria; Wright, Adam; Bates, David W. (2012-10-22). "Preoperative Hyponatremia and Perioperative Complications". Archives of Internal Medicine. 172 (19): 1474–1481. doi:10.1001/archinternmed.2012.3992. ISSN 0003-9926.