SIADH+and+DI

Diabetes Insipidus and Syndrome of Inappropriate Antidiuretic Hormone (SIADH)

Normal Physiology of ADH

• Detection of Serum Osmolality:
  • Decreased serum osmolality is detected by osmoreceptors located in the hypothalamus.
  • This triggers a reduction in the production of Antidiuretic Hormone (ADH) through negative feedback.
• Physiological Processes:
  • Decreased Serum Osmolality:
  • Reflected in increased serum volume.
  • Results in Increased Urine Osmolality and decreased urine volume.
  • Osmoreceptor Function:
  • Osmoreceptor cells in the hypothalamus detect increased serum osmolality, stimulating ADH release from the posterior pituitary gland.
  • ADH Action on Kidneys:
  • ADH binds to receptors on the distal convoluted tubules in the kidneys, promoting the movement of Aquaporin-2 channels to the apical membrane of tubules.
  • These channels facilitate reabsorption of water from the collecting ducts back into the bloodstream.

Antidiuretic Hormone (ADH)

• Also Known As: Vasopressin
• Functions of ADH:
  • Decrease urine production.
  • Decrease sweating.
  • Increase blood pressure.
• Regulatory Mechanisms:
  • Dehydration Response:
  • Release of ADH occurs when blood osmotic pressure is high, stimulating hypothalamic osmoreceptors.
  • Overhydration Response:
  • Inhibition of ADH occurs when blood osmotic pressure is low, also affecting hypothalamic osmoreceptors.
• Pathways Involved:
  • Osmoreceptors activate hypothalamic neurosecretory cells that synthesize and release ADH.
  • Nerve impulses release ADH from axon terminals in the posterior pituitary gland into the bloodstream.
  • Resulting Effects:
  • Kidneys retain more water, thus decreasing urine output.
  • Sudoriferous (sweat) glands decrease water loss by perspiration.
  • Constriction of arterioles increases blood pressure.

Hyperosmolarity Effects

• Increased blood volume leads to increased systemic vascular resistance and arterial pressure through the action of Angiotensin II and sympathetic stimulation, mediated by the hypothalamus and posterior pituitary gland.

Overview of SIADH

• Definition: SIADH is characterized by excessive release of ADH from the posterior pituitary gland.
• Consequences of Excess ADH:
  • Enhanced renal reabsorption of water.
  • Suppression of the renin-angiotensin mechanism, resulting in renal excretion of sodium.
  • Leads to water intoxication, cellular edema, and dilutional hyponatremia, causing a decrease in serum osmolality.

Overview of Diabetes Insipidus (DI)

• Definition: DI results from a deficiency of ADH secreted by the posterior pituitary gland.
• Consequences of Decreased ADH:
  • Reduced ability of distal renal tubules to collect and concentrate urine.
  • Results in excessive diluted urination, excessive thirst, electrolyte imbalance, and increased fluid intake.

Assessment: Risk Factors

SIADH Risk Factors

• Conditions stimulating hypothalamus to hypersecrete ADH include:
  • Malignant tumors (e.g., lung cancer)
  • Increased intrathoracic pressure from positive pressure ventilation.
  • Head injury, meningitis, stroke.
  • Tuberculosis.
  • Various medications (chemotherapy agents, tricyclic antidepressants, SSRIs, opioids, fluoroquinolone antibiotics).

DI Risk Factors

• Head injury, tumors, lesions, surgery/radiation near the pituitary gland, or infections (meningitis, encephalitis).
• Medications such as lithium carbonate or demeclocycline.
• Increased risk in older adults due to:
  • Lower body water content,
  • Decreased thirst response,
  • Reduced kidney's ability to concentrate urine,
  • Increased diuretic usage,
  • Swallowing difficulties or inadequate food intake.

Clinical Manifestations

SIADH Manifestations

• Polyuria: Excessive urination (4 to 30 L/day of dilute urine) due to renal tubule failure.
• Polydipsia: Excessive thirst (2 to 20 L/day).
• Nocturia and Fatigue.
• Dehydration Symptoms: Extreme thirst, weight loss, muscle weakness, headache, constipation, dizziness.

DI Manifestations

• Early signs include:
  • Headache, weakness, anorexia, muscle cramps.
• As serum sodium decreases, symptoms include:
  • Personality changes, hostility, sluggish deep tendon reflexes, nausea, vomiting, diarrhea, oliguria.
• Urine appears dark yellow and concentrated.

Physical Assessment Findings

SIADH Findings

• Observations include:
  • Sunken eyes
  • Tachycardia
  • Hypotension
  • Loss or absence of skin turgor
  • Dry mucous membranes
  • Weak, poor peripheral pulses
  • Decreased cognition.

DI Findings

• Indicators include confusion, lethargy, Cheyne-Stokes respirations.
• Severe cases can lead to seizures, coma, and death.
• Signs of fluid volume excess include:
  • Tachycardia, bounding pulses, possible hypertension, crackles in lungs, distended neck veins, taut skin, weight gain without edema.
  • Intakes surpass outputs.

Laboratory Testing

SIADH Laboratory Findings

• Electrolyte Imbalances:
  • Diluational hyponatremia (decreased sodium).
• Urine Chemistry: Concentrated results with:
  • Increased urine sodium
  • Increased urine osmolality (as urine volume decreases).
• Blood Chemistry: Dilute results with:
  • Decreased serum sodium (
  • Decreased serum osmolality (<270 mEq/L).

DI Laboratory Findings

• Electrolyte Imbalances: Increased sodium.
• Urine Chemistry: Dilute results with:
  • Decreased urine specific gravity (<1.005)
  • Decreased urine osmolality (<200 mOsm/L)
  • Decreased urine pH, sodium, and potassium (as urine volume increases, urine osmolality decreases).
• Serum Chemistry: Concentrated results with:
  • Increased serum osmolality (>300 mOsm/L)
  • Increased serum sodium and potassium (as serum volume decreases, osmolality increases).

Diagnostic Testing & Procedures

• Water Deprivation Test (ADH stimulation test):
  • Induces dehydration through fluid withholding.
  • Administer a subcutaneous injection of vasopressin; evaluates urine output, specific gravity, and osmolality changes.
  • Positive DI test if kidneys cannot concentrate urine despite elevated plasma osmolality.
• Nursing Actions:
  • Obtain baseline patient data including weight, vital signs, serum electrolytes, osmolality, urine specific gravity.
  • Monitor vital signs, urine specific gravity, and body weight hourly during the test.
  • Discontinue if there is a loss of >2 kg and rehydrate the client.

SIADH Nursing Care

• Fluid Restriction:
  • Limit oral fluid intake to 500-1,000 mL/day.
  • Provide comfort for thirst, e.g., mouth care, ice chips.
  • Use 0.9% sodium chloride for flushing enteral tubes.
• Monitor:
  • Intake and output, vital signs (watch for increased blood pressure, tachycardia).
  • Lung sounds for pulmonary edema; report decreased urine output, altered mental status, weight daily.
• Safety: Reduce stimuli for clients with altered consciousness and maintain seizure precautions.
• Monitor for Heart Failure: Can occur from fluid overload; consider loop diuretics.

SIADH Medications

Demeclocycline (Tetracycline Derivative)

• Indication: Corrects fluid imbalances by promoting urine flow.
• Contraindications: Impaired kidney function.
• Nursing Considerations:
  • Monitor serum sodium/osmolality and urine output.
• Client Education:
  • Avoid concurrent use with calcium and iron supplements, antacids or milk.
  • Watch for yeast infection signs and sun exposure risks.

Vasopressin Antagonists (Tolvaptan, Conivaptan)

• Function: Promote water excretion without sodium loss.
• Nursing Considerations:
  • Administer in acute settings; monitor blood glucose and serum sodium.
• Client Education:
  • Frequent oral care is essential; monitor hydration status.

Loop Diuretics (Furosemide)

• Indication: Increase water excretion.
• Nursing Considerations:
  • Use cautiously due to potential sodium excretion and worsening hyponatremia.
• Client Education:
  • Warn about postural hypotension; report hyponatremia symptoms.

Hypertonic Sodium Chloride IV Fluid

• Purpose: Elevate sodium levels to alleviate neurologic compromise.
• Dosing: In severe cases, administer 200-300 mL of 3%-5% sodium chloride.
• Nursing Actions:
  • Monitor for overload and heart failure (e.g., distended neck veins, lung crackles).
• Client Education:
  • Explain procedures and monitor for breathing difficulties.

SIADH Complications

• Potential issues include water intoxication, cerebral or pulmonary edema, severe hyponatremia, coma, and death.
• Nursing Actions:
  • Early recognition of water intoxication symptoms (lung crackles, neck vein distention, altered neurological state).
• Regular monitoring of neurologic status and maintain seizure precautions.
  • Administer medications as needed; monitor vital signs and serum sodium levels.
• Client Education:
  • Provide information on fluid restrictions; support the client in understanding their condition.

Diabetes Insipidus (DI) Nursing Care

• Monitoring:
  • Vital signs, urine output, central venous pressure, and I&O are essential.
  • Daily weigh clients; promote dietary adherence.
• IV Therapy: Hydration matching I&O is crucial, electrolyte replacement as prescribed.
• Safety Measures: Ensure client safety and assist with ambulation as needed.
• Dietary Considerations: Add bulk foods; treat constipation if it occurs.
• Skin Care: Regular assessments and care to prevent skin breakdown.

Diabetes Insipidus Medications

ADH Replacement Agents

• Examples: Desmopressin or aqueous vasopressin, administered intranasally or parenterally.
• Effects: Increased kidney water absorption and decreased urine output.
• Monitoring: Vital signs, urine output, central venous pressure, and laboratory results (potassium, sodium, BUN, creatinine).
• Cautions: Use carefully in clients with coronary artery disease