From the Guidelines
Cycling total parenteral nutrition (TPN) carries a risk of metabolic disturbances, including hyperglycemia and hypoglycemia, particularly in young children and infants, and should be implemented gradually with careful monitoring, as recommended by the ESPGHAN/ESPEM/ESPR/CSPEN guidelines 1. The main risks associated with cycling TPN include:
- Metabolic disturbances, such as hyperglycemia and hypoglycemia, during transitions 1
- Electrolyte imbalances, particularly calcium loss during infusion of cyclical PN 1
- Potential liver dysfunction, including intestinal failure-associated liver disease (IFALD), although cyclical PN may have a protective effect 1 When TPN is cycled, patients may experience rapid glucose fluctuations as the infusion starts and stops, which can be particularly problematic for young children and infants due to their immature gluconeogenesis and limited glycogen stores 1. To minimize these risks, TPN cycling should be implemented gradually, with:
- Frequent assessment of volume/rate tolerance and blood glucose 1
- Tapering of the infusion rate up at the beginning and down at the end of each cycle 1
- Regular laboratory monitoring during the transition to cycled TPN and periodically thereafter 1 The optimal time to initiate cyclical PN is unknown, but it is recommended to start once patients are in a stable clinical condition and can maintain normoglycaemia during a period without PN infusion 1.
From the Research
Risks of Cycling Total Parenteral Nutrition (TPN)
- The risk of cycling TPN includes hypoglycemia or hyperglycemia, new-onset or worsening dyspnea, tachycardia, tachypnea, lower extremity or sacral edema, pulmonary edema, or abdominal ascites 2
- Hyperglycemia is a prevalent TPN-related adverse event, occurring in 24.2% and 30.0% of patients in the fast-track and standard groups, respectively 2
- Fast-track cycling is as safe as standard cycling in patients without diabetes mellitus or major organ dysfunction requiring long-term TPN 2
- Refeeding syndrome is a risk in adults receiving TPN, with high-risk patients more likely to have electrolyte abnormalities after receiving TPN regardless of preventative measures 3
- Parenteral nutrition-associated liver disease is a significant complication of TPN, with novel mechanisms including alterations in the Farnesoid X receptor and fibroblast growth factor 19 signaling pathway 4
- Cyclic TPN infusion may stabilize liver function tests in some patients with mild hyperbilirubinemia, but abrupt infusion initiation may cause hyperglycemia and abrupt discontinuation may cause hypoglycemia, predominantly in children younger than 2-3 years old 5
Metabolic Effects of Cyclic TPN Infusion
- Cyclic and continuous TPN infusions result in similar nitrogen balance and circulating counterregulatory hormone concentrations 5
- Carbohydrate oxidation decreases, fat oxidation increases, and the respiratory quotient decreases following TPN infusion 5
- Cyclic TPN infusion is not associated with increased daily calcium, phosphorus, magnesium, or vitamin D losses 5
Calculating TPN Cycles
- A mathematical formula can be used to calculate cyclic TPN flow rates as a function of total volume and cycle time: F = V/(4T-10), where F is the basal flow rate, T is the desired cycle time, and V is the total volume of TPN to be delivered in 24 hours 6