Why is sudden discontinuation of TPN detrimental?

Trauma patients with wound healing could require 27 Kcal/kg/day of TPN (1). All TPN formulas contain dextrose, amino acids, lipids and vitamins. High dextrose content in TPN causes increase in endogenous insulin production (2). Long term TPN use can also cause islet hypertrophy and hyperplasia with increased insulin secretion (3,4,5).

Sudden cessation of TPN can lead to hypoglycemia because of increased endogenous insulin not adjusting to sudden glucose reduction (7). A study where serial serum glucose concentration were measured showed 50% of patients with abrupt TPN discontinuation developed hypoglycemia (<40mg/dl) compared to 20 % where TPN was reduced by 1/2 for an hour before discontinuation (8). The following two examples of TPN discontinuation can be used. A recommended procedure  in patients receiving enteral feeding or Tube Feedings (TF) is once patient is receiving TF at 50% of goal rate with good tolerance, the TPN may be reduced to 1/2 of goal for 4 hrs. The patient then can be weaned from TPN as TF rate advances to goal. Another recommended strategy is to reduce TPN infusion rate by 50% over the first hour and an additional 50% over the second hour before stopping TPN (6).

Patients on TPN cessation require bedside glucose monitoring. If hypoglycemia occurs during weaning, then the hypoglycemia is corrected by adding dextrose to IV (1).
           

References
         

1. Criticalcarenutrition.com       

2. C.H Rees, The Hitchhiker's Guide to Parenteral Nutrition Management for Adult Patients, Practical Gastroenterology, 2006;60:46-68
3. Gordon SS, Mayhew S, Johnson D. Parenteral nutrition implementation and management. In Merritt R, ed. The A.S.P.E.N. Nutrition Support Practice Manual. 2nd ed. Silver Spring, Md: American Society for Parenteral and Enteral Nutrition; 2005:108-117.
4. Nirula R, Yamada K, Waxman K. The effect of abrupt cessation of total parenteral nutrition on serum glucose: a randomized trial. Am Surg. 2000;66:866-869.
5. Eisenberg PG, Gianino S, Clutter WE, Fleshman JW. Abrupt discontinuation of cycled parenteral nutrition is safe. Dis Colon Rectum. 1995;38:933-939.
6. Robert D. Odze, M.D., John R. Goldblum, M.D. Surgical Pathology of the GI Tract, Liver, Biliary Tract, and Pancreas. 2nd edition, 2009:815-816
7. Wagman LD, Miller KB, Thomas RB, Newsome HH, Weir GC. The effect of acute discontinuation of total parenteral nutrition. Ann Surg. 1986;204:524-529.
8. Bendorf K, Friesen CA, Roberts CC. Glucose response to discontinuation of parenteral nutrition in patients less than 3 years of age. J Parenter Enteral Nutr., 1996;2:120

 

from Michael Abraha, MS4
revised 15 April 2013