| DI (Fluid Deficit) | SIADH (Fluid Excess) |
|---|
| Pathophysiology: | - Deficiency of ADH → inability to conserve H2O
- Large volumes of hypotonic fluid excreted
| - Excessive ADH secreted → water retention, hyponatremia, and hypo-osmolality
|
| Risk factors: | - Head injury
- Brain infection
- Posterior pituitary tumors
- Drugs that inhibit vasopressin (e.g., glucocorticoids, phenytoin, lithium)
| - Vasopressin overuse (Rx of DI) or stimulation (chemotherapy)
- Small cell carcinoma
- Adrenal insufficiency
- Myxedema
- Anterior pituitary insufficiency
|
| Assessment: | - Polyuria (up to 18 L/day)
- Urine specific gravity ↓
- Signs of fluid volume deficit: dry, cool skin; polydipsia; ↓ weight Laboratory: serum Na+ ↑ initially, then ↓ ; serum osmolality ↑ initially, then ↓
| - Signs of ↓ Na+—fatigue, headache, ↓ DTR, nausea, anorexia, ↓ mental status
- Signs of fluid volume excess: weight gain without edema; tachycardia; tachypnea; crackles
|
| Nursing care plan/implementation: | - Fluids: IV; I/O
 Medications: ADH replacement; Pitressin- Education: prepare for hypophysectomy
| - Fluids: hypertonic IV (↑ Na+); I/O
- Medications: diuretics; demeclocycline (tetracycline)
- Daily weight
|