Lecture Notes: Diabetes Insipidus (DI) and Syndrome of Inappropriate Antidiuretic Hormone (SIADH)

Diabetes Insipidus (DI)

Definition: DI is a condition where the hypothalamus produces insufficient antidiuretic hormone (ADH).
Mechanism: Due to low levels of ADH, the kidneys are unable to conserve water, leading to excessive water loss.
Mnemonic: "DI for dry inside" - Loss of fluids resembles the dryness shown by SpongeBob in a particular episode.

Damage to hypothalamus or pituitary gland: Often due to surgery, radiation, or brain disorders.
Increased intracranial pressure: Suppresses pituitary gland function.
Other conditions: Includes lung disease, cancer, tuberculosis, pneumonia, and chronic infections.

Polyuria: Increased urine output.
Diluted urine: Low urine specific gravity (<1.005).
Dehydration symptoms: Dry skin, dry mucous membranes, decreased blood pressure, and excessive thirst.
Laboratory Findings: Hyperosmolality and hypernatremia due to fluid loss.

Goal: Increase fluid retention and improve homeostasis.
Medications: Administer synthetic ADH (e.g., desmopressin, vasopressin) which contract renal ducts to reduce urine output.
Hydration: Encourage water intake or administer fluids intravenously if necessary (caution with dextrose and normal saline).
Nursing Considerations: Similar to those for SIADH.

Both conditions affect sodium to water ratio in the body.
SIADH: Patient is "soaked inside"; leads to dilution of blood, including sodium.
DI: Patient is "dry inside"; causes increased sodium relative to water content.
Brain Sensitivity: Both conditions require monitoring for neurological changes due to sodium level fluctuations.
- Early Signs: Headache, confusion, lethargy, hyponatremia.
- Late Signs: Muscle twitching, seizures, unresponsiveness, coma, or death if untreated.