In the NCLEX-RN, it’s important to understand the pathophysiology, symptoms, diagnostic findings, and treatment for disorders related to antidiuretic hormone (ADH), which is also known as vasopressin. ADH plays a crucial role in water balance, and its imbalance can lead to conditions like Diabetes Insipidus (DI) and Syndrome of Inappropriate Antidiuretic Hormone (SIADH).
ADH Imbalance: Diabetes Insipidus (DI) vs. SIADH
Condition | Diabetes Insipidus (DI) | Syndrome of Inappropriate Antidiuretic Hormone (SIADH) |
ADH Levels | ↓ ADH (deficiency) | ↑ ADH (excess) |
Primary Cause | Head injury, pituitary tumor, post-transsphenoidal hypophysectomy | Head injury, pituitary tumor, post-transsphenoidal hypophysectomy, lung cancer |
Urinary Output | ↑ Urinary output (polyuria) | ↓ Urinary output (oliguria) |
Fluid Status | Dehydration, excessive thirst (polydipsia), ↓ weight, hypotension | Water intoxication, ↑ weight, ↑ BP, headache, ↑ pulse, moist/cool skin |
Physical Findings | Dry, warm skin, weak, ↓ BP | Edema, moist skin, headache, confusion, seizures risk |
Lab Findings (Serum) | ↑ Na, ↑ osmolarity | ↓ Na, ↓ osmolarity |
Lab Findings (Urine) | ↓ Osmolarity (<1.010), ↓ specific gravity, clear urine | ↑ Osmolarity, ↑ specific gravity (>1.030), dark urine |
Treatment | Vasopressin, Desmopressin | Demeclocycline |
Additional Notes | Causes dehydration, polydipsia, and hypotension | Causes water retention, hyponatremia, and cerebral edema |
Key Pathophysiological Differences:
- Diabetes Insipidus (DI) is characterized by a deficiency of ADH, leading to excessive urine output (polyuria) and a risk of dehydration. This condition is often caused by head injuries, pituitary tumors, or post-surgical issues (Bickley & Szilagyi, 2020).
- Syndrome of Inappropriate Antidiuretic Hormone (SIADH) occurs when excess ADH is released, causing water retention and a dilution of sodium levels, leading to hyponatremia and water intoxication (Bickley & Szilagyi, 2020). Causes include lung cancer, head injuries, and post-surgical states.
Electrolyte Imbalances and Sodium Disorders
Sodium Imbalances:
Condition | Hypo-Sodium (Na < 135) | Hyper-Sodium (Na > 145) |
Causes | Dehydration, SIADH, renal failure, overuse of hypotonic solutions, TURP syndrome, vomiting | Excess sodium retention, dehydration, renal failure, excessive Na intake (sea water, hypertonic solutions) |
Clinical Manifestations | Fatigue, irritability, confusion, seizures risk | Thirst, agitation, increased temperature, confusion |
Treatment | Treat underlying cause, fluid replacement, careful monitoring | Fluid replacement, manage underlying conditions (e.g., corticosteroid use, kidney disease) |
Electrolyte Implications | Hyponatremia can cause cerebral edema, altered mental status, seizures (Bickley & Szilagyi, 2020) | Hypernatremia can lead to dehydration, altered mental status, and kidney failure (AACN, 2020) |
Electrolyte Ranges (Normal and Critical)
Electrolyte | Normal Range | Critical Range |
Sodium (Na) | 135-145 mEq/L | <120 or >160 mEq/L |
Potassium (K) | 3.5-5.1 mEq/L | <2.5 or >6.5 mEq/L |
Chloride (Cl) | 98-107 mEq/L | <80 or >120 mEq/L |
Magnesium (Mg) | 1.6-2.6 mEq/L | <1.0 or >3.0 mEq/L |
Calcium (Ca) | 9-11 mg/dL | <7 or >14 mg/dL |
Phosphorus (P) | 2.6-4.6 mg/dL | <1.0 or >7.0 mg/dL |
Sodium Imbalance Etiologies
- Hyponatremia (<135 mEq/L) can result from:
- Dilutional causes: SIADH, overuse of hypotonic solutions (Bickley & Szilagyi, 2020).
- Dehydration causes: Diarrhea, vomiting, excessive sweating, and inappropriate use of diuretics (AACN, 2020).
- Hypernatremia (>145 mEq/L) can occur from:
- Increased sodium retention: Renal failure, Cushing syndrome, or excessive use of corticosteroids.
- Decreased water intake: Particularly in elderly patients or those on NPO status (AACN, 2020).
- Increased water loss: From conditions like Diabetes Insipidus (Bickley & Szilagyi, 2020).
References
- American Association of Critical-Care Nurses (AACN). (2020). Electrolyte disturbances: Pathophysiology and management. Retrieved from https://www.aacn.org
- Bickley, L. S., & Szilagyi, P. G. (2020). Bates’ guide to physical examination and history taking (12th ed.). Wolters Kluwer.