Lab

Fluid Deprivation Test

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Fluid Deprivation Test

  • Indication
  1. Evaluation of Diabetes Insipidus
  • Precautions
  • Requires close monitoring
  1. Monitor Urine Output
  2. Monitor Vital Signs
  3. Monitor weight
    1. Do not allow weight loss to exceed 3-5%
  • Technique
  1. Fluid restrict patient
    1. Mild Polyuria (<10 L/day)
      1. Start fluid restriction 12 hours before test
    2. Severe Polyuria (>10 L/day)
      1. Start fluid restriction 2 hours before test
  2. Follow Serum Osmolality to steady state
    1. Serum Osmolality should approach 295 mOsm/kg water
    2. Measure Serum Osmolality hourly until endpoint:
      1. Two values are within 30 mOsm/kg of each other
      2. Weight loss exceeds 3-5%
  3. Administer endogenous ADH
    1. Vasopressin 5 units SQ
    2. Intranasal ddAVP 10 ug
  4. Measure Serum Osmolality 1 hour after ADH administered
  • Interpretation
  1. Water deprivation effect on urine concentrating ability
    1. No response in Nephrogenic DI
    2. No response in Central DI
  2. Exogenous ADH effect on urine concentrating ability
    1. Corrects Central DI
    2. Does not correct Nephrogenic DI