Danielle asked what do we need to know about insulin requirements for peritoneal dialysis (PD). Thanks for the question Danielle, lets dig in.
Why would insulin requirements be different in PD?
Most peritoneal dialysis solutions use dextrose to help remove fluid. In the PD clinic I worked at, our most common solutions were 1.5% and 2.5% dextrose. We also used a 4.25%, which was considered a “rescue” for extra fluid removal.
Because the solutions contain dextrose, some dextrose will be absorbed while the solutions are “dwelling” (hanging out in the peritoneal cavity). This absorption can cause an increase in blood glucose (BG) levels and increase insulin requirements.
How much glucose is absorbed?
Here is a common method for estimating glucose and energy exposure from PD.
Volume of the solution (L) * Dextrose (g/L) * 40-60% absorption rate.
Use the 60% absorption rate for longer dwells (e.g. Continuous Ambulatory PD). Use the 40% absorption rate for shorter dwells (e.g. cycler).
Here is an example using one of that most common CAPD prescriptions used in my PD clinic: 4 exchanges, using 2L volumes and the solutions are 1.5/2.5/1.5/2.5.
Step 1: Figure out how much dextrose is in the solutions
(4L * 15g/L) + (4L * 25g/L) = 60 + 100 = 160g dextrose
Step 2: Figure out dextrose exposure
160g glucose * 0.6 absorption rate = 96g dextrose exposure
OPTIONAL Step 3: Estimate the energy added from the PD solutions
To calculate the energy – multiply the dextrose exposure by 3.4kcal/g
96g * 3.4kcal/g = 326.4kcal
How good are these formulas at predicting glucose exposure from PD?
In this study, researchers measured actual glucose exposure for adults on CCPD. The measured glucose exposure was lower than the estimated exposure.
Why are formulas making errors? Probably because they fail to consider factors that impact glucose absorption. As the authors of this article highlight, several factors impact glucose absorption.
| Factors that impact glucose absorption rates | Factor that didn’t impact glucose absorption rates |
|---|---|
| Dwell Time | Glucose concentration (e.g. 1.5% and 2.5% had the same absorption rate) |
| Membrane Characteristics |
50% of the glucose was absorbed within the first 90 minutes of the dwell. 75% is absorbed within 6 hours.
How does this impact the estimated changes to insulin requirements?
It is no longer common to add insulin to the PD solution bags. Because it increased the insulin required. By, potentially as much as 30%, according to this systematic review article.
In this study of 61 adults living with diabetes starting peritoneal dialysis, they reported an addition of 7.5u per day for every 2L exchange using a 2.5% solution.
However, as the authors of this 2023 review of diabetes management for adults on PD points out, there have been very few studies that have actually examined the impact the BGs and insulin administration in this population. Therefore these authors recommend individualized assessment and care as opposed to a specific insulin-adjustment recommendation.
Take Aways
- Our simple formula for calculating absorption of glucose is an estimate. Not an actual amount. The actual amount of dextrose absorbed will differ depending on the patient.
- Insulin needs will likely go up, but we don’t know by how much. One article reported an additional 7.5u per each 2.5%-2L exchange per day – though more studies are recommended before a specific adjustment can be made.
