What is the protocol for performing a Desmopressin (DDAVP) Challenge Test?

Desmopressin Challenge Test Protocol

The Desmopressin Challenge Test is performed by administering desmopressin acetate 0.3 mcg/kg body weight intravenously, diluted in sterile physiological saline and infused slowly over 15-30 minutes, with monitoring of factor VIII activity and other hemostatic parameters before and after administration. 1

Patient Preparation

• Ensure patient is in normal hydration status before beginning the test 2
• Obtain baseline measurements including complete blood count, serum electrolytes (particularly sodium), and baseline coagulation studies (factor VIII activity, VWF:Ag, VWF:RCo) 3, 2
• Review patient's medication history for anticoagulants or medications that might interfere with test results 3
• Fluid restriction should be observed to prevent hyponatremia 1, 4

Test Administration

• For adults and children >10 kg: Dilute desmopressin in 50 mL of sterile physiological saline 1
• For children ≤10 kg: Dilute desmopressin in 10 mL of sterile physiological saline 1
• Administer desmopressin acetate at a dose of 0.3 mcg/kg body weight via intravenous infusion over 15-30 minutes 1
• Monitor blood pressure and pulse during infusion 1

Sample Collection and Monitoring

• Draw blood samples at specific intervals:

  • Baseline (before desmopressin administration) 3
  • 30 minutes after starting infusion 1
  • 1 hour after starting infusion 1
  • 2 hours after starting infusion (peak response typically occurs between 90 minutes to 2 hours) 1
  • 4 hours after starting infusion 1

• Measure the following parameters at each time point:

  • Factor VIII activity 3, 1
  • VWF:Ag (von Willebrand factor antigen) 3
  • VWF:RCo (ristocetin cofactor activity) 3, 1
  • Platelet function (if indicated) 3

Result Interpretation

• A positive response is typically defined as:

  • ≥2-fold increase in factor VIII activity from baseline 1
  • Increase in VWF:Ag and VWF:RCo levels 1
  • Maximum plasma levels typically reach 300-400% of initial concentrations after infusion of 0.4 mcg/kg 1

• Response patterns help classify von Willebrand disease subtypes:

  • Type 1: Proportional increase in both VWF:Ag and VWF:RCo 3
  • Type 2: Disproportionate increase (VWF:RCo increases less than VWF:Ag) 3
  • Type 3: Minimal or no response 3

Safety Considerations

• Monitor for potential side effects, particularly hyponatremia 2, 4

• Caution patients against excessive fluid intake during and after the test to prevent water intoxication 2, 4

• Exercise particular caution in patients with:

  • Renal impairment 2, 1
  • History of seizures 2
  • Cystic fibrosis 2
  • Elderly patients (due to higher risk of impaired renal function) 1

• If repeat administration is needed, consider that tachyphylaxis may occur with administrations given more frequently than every 48 hours 1

Common Pitfalls and Caveats

• Avoid excessive fluid intake during testing as this can lead to hyponatremia 2, 4
• In cases of DDAVP-associated hyponatremia, continuing DDAVP while correcting sodium levels may be safer than abrupt discontinuation, which can lead to rapid correction of serum sodium and potential neurological injury 4
• The necessity for repeat administration should be determined by laboratory response and clinical condition 1
• Recognize that the bioavailability of IV administration is approximately ten times that of intranasal administration 1
• Children may require size-adapted dosing regimens as body weight significantly affects clearance and volume of distribution 5