Lecture Notes: Diabetes Insipidus and SIADH

Introduction

• Focus on two disorders: Diabetes Insipidus (DI) and Syndrome of Inappropriate Antidiuretic Hormone (SIADH).
• Both disorders relate to the function of Antidiuretic Hormone (ADH).
• ADH is released by the posterior pituitary gland in response to low blood volume, low blood pressure, or hypernatremia.

Diabetes Insipidus (DI)

Types

1. Neurogenic Diabetes Insipidus

   • Cause: Insufficient ADH release due to hypothalamus/pituitary injury or tumor.
   • Effect: Kidneys do not reabsorb water.

2. Nephrogenic Diabetes Insipidus

   • Cause: Kidneys do not respond to ADH despite normal release.
   • Effect: May result from kidney infection or nephrotoxic medications.

Signs and Symptoms

• Large amounts of dilute urine.
• Polydipsia (excessive thirst).
• Dehydration, hypotension, anorexia.

Lab Findings

• Urine: Low specific gravity (< 1.005), low osmolality (< 200), decreased sodium levels.
• Blood: High osmolality (> 300), high sodium levels (hypernatremia).

Diagnosis

• Water deprivation test (kidney concentration ability).
• Vasopressin test (distinguishes between neurogenic and nephrogenic DI).

Treatment

• Medications: Vasopressin or Desmopressin.

Nursing Care

• Monitor intake and output (I&O), urine specific gravity, daily weight.

Syndrome of Inappropriate ADH (SIADH)

Causes

• Excess ADH release due to brain tumor, head injury, meningitis, or certain medications.

Signs and Symptoms

• Small amounts of concentrated urine.
• Fluid volume excess: Tachycardia, hypertension, crackles, jugular vein distention, weight gain.
• Neurological symptoms: Headache, weakness, muscle cramping, confusion (due to hyponatremia).

Lab Findings

• Urine: High specific gravity (> 1.03), increased osmolality.
• Blood: Low osmolality (< 270), hyponatremia.

Treatment

• Diuretics, vasopressin antagonists, hypertonic saline to correct sodium levels.

Nursing Care

• Monitor I&O, daily weights, restrict fluids, replace sodium as ordered.
• Monitor for fluid volume excess and potential pulmonary edema.
• Monitor neurological status, implement seizure precautions.

Conclusion

• Understanding of DI and SIADH is crucial for nursing care.
• Key focus on ADH functionality and its effects on the body.

Remember to keep monitoring vital signs, lab results, and adjust treatments accordingly. These notes provide a foundational understanding to guide patient care and management.