Why is D5W (Dextrose 5% in Water) infused between TPN (Total Parenteral Nutrition) infusions?

D5W Infusion Between TPN Administrations: Purpose and Protocol

D5W (Dextrose 5% in Water) is infused between TPN administrations to prevent hypoglycemia that can occur when TPN is abruptly discontinued, especially in children under 2 years of age who have limited glycogen stores and immature gluconeogenesis.

Rationale for D5W Infusion

Preventing Hypoglycemia

• When TPN is cycled or temporarily discontinued, the abrupt cessation of glucose delivery can lead to hypoglycemia, particularly in:
  • Young children under 2 years 1
  • Patients with poor glycogen stores
  • Patients who have become metabolically dependent on continuous glucose infusion

Metabolic Considerations

• TPN typically contains high concentrations of dextrose (often 15-25%) 2
• The maximum recommended dextrose infusion rate is 5-7 mg/kg/min 1
• Abrupt discontinuation can trigger a rapid drop in blood glucose levels
• D5W provides a gradual tapering of glucose delivery, allowing the body to adjust metabolically

Protocol for D5W Administration

Tapering Process

• When discontinuing TPN, a gradual tapering approach is recommended:
  • Begin with a 1-2 hour taper-down period of the TPN infusion 1
  • Follow with D5W infusion at a rate calculated to maintain glucose delivery at 2-3 mg/kg/min
  • This prevents the metabolic shock of sudden glucose withdrawal

Restarting TPN

• When reinitiating TPN, a similar tapering approach should be used:
  • Begin with D5W infusion
  • Gradually increase TPN infusion rate over 1-2 hours 1
  • This prevents hyperglycemia and respiratory distress that can occur with sudden high glucose loads

Special Considerations

Pediatric Patients

• Children are at higher risk of hypoglycemia with abrupt TPN discontinuation 1
• The risk is particularly high in children under 2 years due to:
  • Limited glycogen stores
  • Immature gluconeogenesis
  • Higher glucose demands relative to body weight

Adult Patients

• Most stable adults can tolerate abrupt discontinuation of TPN without D5W bridging
• However, D5W is still commonly used as a precautionary measure, especially in:
  • Patients with diabetes or metabolic disorders
  • Malnourished patients
  • Patients who have been on long-term TPN

Monitoring Recommendations

• Blood glucose should be monitored:
  • Before discontinuing TPN
  • 30-60 minutes after switching to D5W
  • Before restarting TPN
• Target blood glucose should be maintained between 100-180 mg/dL

Common Pitfalls to Avoid

• Abrupt discontinuation: Never abruptly stop TPN without a tapering protocol, especially in children
• Inadequate monitoring: Failure to check blood glucose during transition periods
• Incorrect D5W rate: Using a rate that's too low may not prevent hypoglycemia; too high may cause hyperglycemia
• Forgetting the taper-up: When restarting TPN, a gradual increase in infusion rate is as important as the taper-down when stopping

By following these guidelines, the risk of hypoglycemia during transitions between TPN administrations can be minimized while maintaining patient safety and metabolic stability.