title: A practical guideline for calculating parenteral nutrition cycles.
abstract: BACKGROUND
  Both physiologic and psychological reasons for cycling total parenteral nutrition (TPN) have been well established. Despite widespread acceptance of this practice, the only previously published method for calculating TPN cycle rates is inherently flawed.
  
  
  METHODS
  A mathematical formula was derived to facilitate reliable calculation of cyclic TPN flow rates as a function of total volume and cycle time. A publicly accessible website was subsequently developed to expedite rapid determination of TPN cycles.
  
  
  RESULTS
  A fail-safe method of calculating TPN cycle flow rates can be expressed as F = V/(4T-10), where F is equal to the basal flow rate (mL/h), T is equal to the desired cycle time (hours), and V is equal to the total volume of TPN (mL) to be delivered in 24 hours. The basal flow rate and twice the basal flow rate are used for the first and last 2 hours of the TPN cycle, and the remainder of the cycle runs at 4 times the basal flow rate. TPN cycles may be easily calculated online using this formula at http://peds.stanford.edu/tpn.html.
  
  
  CONCLUSIONS
  We have developed a fail-safe method of calculating TPN cycle flow rates that will consistently deliver the desired volume and have made an online implementation of this formula publicly available.
authors.affiliation: Department of Pediatrics, Stanford University, California, USA.
authors.forename: Chris
authors.initials: C
authors.lastname: Longhurst
authors.forename: Louie
authors.initials: L
authors.lastname: Naumovski
authors.forename: Manuel
authors.initials: M
authors.lastname: Garcia-Careaga
authors.forename: John
authors.initials: J
authors.lastname: Kerner