Disorders of the Posterior Pituitary

Disorders of Posterior Pituitary

- Syndrome of Inappropriate ADH (SIADH)
- Diabetes Insipidus

Syndrome of Inappropriate ADH

Overproduction of ADH

Affect of Overproduction of ADH

• Reabsorption of water in renal distal tubule/collecting duct
• Dilutional hyponatremia, decreased osmolality, hypochloremia, decreased, concentrated urine output

Diagnosis of SIADH

• Serum sodium < 134 mEq/L
• Serum osmolality < 280 mOsm/kg
• Urine specific gravity > 1.025
• Serum osmolality < urine osmolality

Clinical Manifestations of SIADH

• Increased weight; decreased urine output
• Thirst, Dyspnea On Exertion, fatigue
• Progressive Hyponatremia

Stages of Hyponatremia in SIADH

- muscle cramps, headache, irritability
- Sodium < 120 mEq/L vomiting, abdominal cramps, muscle twitching
- Cerebral edema, seizures, coma

Treating SIADH

• Treat underlying cause
• Depends on Sodium Level
• Vasopressin receptor antagonists

SIADH Treatment with Sodium > 125 mEq/L

• Fluid restriction of 800 to 1000 mL/day
• Loop diuretic
• Demeclocycline blocks effect of ADH on renal tubules
• Seizure & fall precautions
• HOB flat or < 10 degrees to decrease load on heart

SIADH Treatment with Sodium < 120 mEq/L

• 3% sodium chloride
• Do not increase sodium > 8-12 mEq in 24 hours
• Fluid restriction 500 mL/day

Vasopressin receptor antagonists

• Block activity of ADH
• Conivaptan IV
• Tolvaptan PO
• Do not give with liver disease

Nursing Interventions for SIADH

• Fluid restriction
• Oral care
• Ice chips/chewing gum
• Daily weight
• Sodium & potassium supplements
• Seizure and fall precautions
• HOB flat or < 10 degrees
• Turning, positioning, ROM

Diabetes Insipidus

• Underproduction / hyposecretion of ADH or decreased renal response to ADH

Urine output with DI

• Increased urine output (2 to 20 L/day)
• Very low urine specific gravity (< 1.005)
• Urine osmolality low (< 100)
• Can lead to Dehydration, hypotension, tachycardia, & hypovolemic shock

Plasma Osmolality with DI

• Increased plasma osmolality (>295)
• Hypernatremia (> 145 mg/dL)
• Uncorrected: brain shrinkage & intracranial bleeding
• CNS irritability, mental dullness, coma
• Polydipsia

Treatment: Diabetes Insipidus

• Fluid replacement (Oral or IV)
• When Acute: Hypotonic saline or dextrose titrated to replace urine output
• Hormone therapy with ADH analogs
• Monitor pulse, BP, LOC, I & O, SG

ADH Analogs for DI

• DDAVP (PO, nasal, subcutaneous, IV)
• Aqueous vasopressin