Syndrome of Inappropriate Diuretic Hormone (SIADH)

Question 1

What is SIADH?

Answer 1

• Also known as Schwartz-Barter syndrome; is a problem in which antidiuretic hormone (ADH, vasopressin) is secreted even when plasma osmolarity is low or normal, resulting in water retention and fluid overload
• ADH continues to be released when not needed, leading to water retention and disturbances of fluid and electrolytes balance.
• Water retention results in DILUTIONAL HYPONATREMIA and FLUID OVERLOAD
• The increase in blood volume increases the kidney filtration and inhibits the release of renin and aldosterone, which increases urine sodium loss and greater hyponatremia

Question 2

Causes of SIADH

Answer 2

1. CNS disturbances (Stroke, Hemorrhage, Infection, Trauma, Surgery)
2. Tumors (especially small cell lung cancer)
3. Meds (mood stabilizers, anti-psychotics, anti-epileptics)

Question 3

Signs and Symptoms of SIADH

Answer 3

1. Early symptoms are related to the water-retention causing dilution of serum sodium levels (hyponatremia)
2. GI disturbances
    Loss of appetite
    Nausea
    Vomiting
3. Weigh the patient and document any recent weight gain
    Use this information to monitor response to therapy
    In SIADH, free water (not salt) is retained, and dependent edema is not usually present, even though water is retained.
4. Nervous System Function (serum sodium levels below 115 mEq/L)
    Lethargy and Headache (these can lead to decreased responsiveness, seizures and coma)
   
   • Assess deep tendon reflexes
      Hostility
      Disorientation
      Change in LOC
5. Vital Signs
    Full and bounding pulse (cause by increased fluid volume)
    Hypothermia (cause by central nervous system disturbances)
6. Fluid Volume Excess
    Tachycardia
    Hypertension
    Crackles
    JVD

Question 4

History Assessment

Answer 4

1. Ask about medical history, which may reveal conditions that can cause SIADH

Question 5

Diagnosis

Answer 5

1. Symptoms and Labs
   o Plasma levels compared to urine osmolarity levels

Question 6

Laboratory

Answer 6

1. Specific Gravity: urine will be super concentrated; will be ELEVATED (over 1.030)
2. Urine Osmolality/Osmolarity: INCREASED due to it being so concentrated
3. Serum Osmolality/Osmolarity: VERY DILUTE; DECREASED (under 270)
4. Sodium: HYPONATREMIA due to being diluted with extra fluid volume (water)
5. BUN: Normal
6. Creatine: Normal
7. ADH: Excess release of ADH (INCREASED)

Question 7

Intervention: Fluid Restriction

Answer 7

1. Essential because fluid intake further dilutes plasma sodium levels
2. Fluid intake may be as low as 500-1,000 mL/24hr
3. Use saline instead of water to dilute tube feeding, irrigate GI tubes, and give drugs by GI tube
4. Measure intake, output and daily weights to assess the degree of fluid restriction needed
5. Prevent mouth dryness with frequent oral rinsing (warn patients not to swallow the rinses)

Question 8

Intervention: Drug Therapy

Answer 8

1. VASOPRESSIN RECEPTOR ANTAGONIST (Vaptans; TOLVAPTAN or CONIVAPTAN)
    Tolvaptan and Conivaptan are used to treat SIADH when hyponatremia is present in hospitalized patient
    The drugs promote water excretion WITHOUT causing sodium loss
    Tolvaptan: given oral drug
   
   • Has a black box warning that rapid increases in serum sodium levels (greater than 12 mEq/L increase in 24 hours) has been associated with central nervous system demyelination that can lead to serious complications and death
   • When used at a higher dosage or for longer than 30 days, there is significant risk for LIVER FAILURE and DEATH
      Conivaptan: given IV
2. Diuretics
    Used on a limited basis to manage SIADH when sodium levels are near normal and heart failure is present
    With diuretics, sodium loss can be potentiated, further contributing to the problems caused by SIADH
    For MILDER SIADH, DEMECLOCYCLINE, an oral antibiotic may help reach fluid and electrolyte balance, although the drug is not approved for this problem
3. IV Fluids
    HYPERTONIC saline (3%) is used for SIADH when serum sodium level is very low
    Give IV saline cautiously because it may add to existing fluid overload and promote heart failure
    If the patient needs routine IV fluids, a saline solution is prescribed to prevent further sodium dilution

Question 9

Monitoring Patient for Drug Therapy

Answer 9

1. Response to therapy to prevent the fluid overload from becoming worse, leading to pulmonary edema and heart failure
   > Any patient, regardless of age, is at risk for these complications
   > The older adult or one who also has cardiac, kidney, pulmonary, or liver disease is at GREATER risk
2. Increased fluid overload
   • Bounding pulse, increase neck vein distention, lung crackles, dyspnea, increasing peripheral edema, reduced urine output); monitor every 2 hours
   • Pulmonary edema can occur very quickly and can lead to DEATH
   • Notify provider of any change that indicates the fluid overload is not responding to therapy or is worse

Question 10

Intervention: Providing a Safe Environment

Answer 10

1. Is needed when sodium levels fall below 120 mEq/L
2. The risk for neurologic changes and SEIZURES increases as a result of osmotic fluid shifts into brain tissue
   
   • Observe and document any changes in the patient’s neurologic status
   • Assess for subtle changes, such as muscle twitching, increasing irritability or restlessness, before these proceed to seizure and coma
   • Check orientation to time, place and person every 2 hours because disorientation or confusion may be present as an early indication
     * Reduce environmental noise and lighting to prevent overstimulation
3. The frequency of neurologic checks depends on the patient’s status
   
   • For a patient with SIADH who is alert, awake and oriented, check every 2-4 hours
   • For a patient who has had a change in LOC, perform neurologic checks at least every hour or as prescribed
   • Inspect the environment every shift, making sure that basic safety measure (side rails are secured in place)