Download Syndrome of Inappropriate Antidiuretic Hormone Secretion (SIADH)

Syndrome of Inappropriate Antidiuretic Hormone Secretion (SIADH)
Pathophysiology
Abnormal production &
secretion of antidiuretic hormone
(ADH) vasopressin

Vasopressin normally
released from posterior
pituitary → acts on
collecting ducts → causes
kidneys to reabsorb water
Water retention results in
hyponatremia & water
intoxication
Incidence & At Risk
Populations
Occurs in 3-5% of adults with
cancer
Causes:
Ectopic tumor secretion of ADH
or ADH-like substances

Small cell lung cancer
(accounts for 80% SIADH
in cancer)

Head & neck cancer

Pancreatic, prostate,
duodenal, or colon
carcinoma

Hodgkin’s & nonHodgkin’s lymphoma

Thymoma

Primary brain tumors
Chemotherapy

Cisplatin

Cyclophosphamide

Ifosphamide

Melphalan (high dose)

Vinca alkaloids
Other Medications

Narcotics

Tranquilizers

Barbiturates

General anesthetics
Non-Malignant Causes

CNS Disorders

Pulmonary Disorders
Signs & Symptoms
Severity of symptoms depends
on how quickly the syndrome
develops and the degree of
hyponatremia
Mild hyponatremia:
Sodium 125 – 134 mEq/L

May be asymptomatic

May present with thirst,
anorexia, nausea, fatigue,
weakness, muscle cramps,
headache
Moderate hyponatremia:
Sodium 115 – 124 mEq/L

Weight gain, oliguria,
progressive neurologic
symptoms
Severe hyponatremia:
Sodium < 115 mEq/L

Signs/symptoms related to
cerebral edema

Papilledema, delirium,
hypoactive reflexes, ataxia,
gait disturbances, seizures,
coma, death
Other common symptoms:

Weight gain without edema

Thirst

↓ Urine Output
Medical Management
Treat underlying cause
Fluid restriction
Mild hyponatremia: 800-1,000
ml/day
Moderate to severe
hyponatremia: 500 ml/day
IV fluid administration
Mild to moderate hyponatremia:
isotonic (0.9%) saline
Severe hyponatremia:
hypertonic (3%) saline may be
infused at rate of 1-2 mEq/L per
hour

Discontinue when serum
sodium level >120 mEq/L

Avoid rapid correction of
hyponatremia → too rapid
correction may lead to
demyelination of nerve
tissue 20 rapid loss of brain
electrolytes & organic
osmolytes
Pharmacologic interventions:
Administer medications that
block the action of ADH in the
collecting tubules

Demeclocycline: 600 –
1200 mg po daily

Urea 30-60 mg po daily

Lithium carbonate
Nursing Management
Assess hydration status

Skin turgor

Mucus membranes

Intake & output

Daily weights
Assess neurologic status

Changes in LOC

Headache

Lethargy

Irritability

Disorientation, mental
confusion

Seizures
Maintain safety needs

Seizure precautions for
serum sodium < 125 mEg/L

Keep area free of clutter
Patient & Family Education

Report signs & symptoms
of hyponatremia including
thirst, weight gain without
edema, ↓ urine output,
nausea, anorexia, weakness,
headache, confusion,
irritability

Rationale for fluid
restrictions & plan for fluid
intake

Comfort measures to ↓ dry
mouth (oral care, sugarless
candy)
From: Clancey, J.K. (2006). “Syndrome of Inappropriate Antidiuretic Hormone Secretion”, in Understanding and Managing Oncologic Emergencies: A Resource for
Nurses, Kaplan, M. (Ed.). Pittsburgh: Oncology Nursing Society, pp. 197-216.