Monitoring the PD Patient

Frequency of monitoring

The KDOQI Guidelines recommend that the patient’s baseline peritoneal membrane transport characteristics should be established after initiating a daily PD therapy using the tests such as the peritoneal equilibration test or peritoneal function test (for more information on common tests please visit the Understanding the Testing Methods article) (1). Data suggests waiting until 4 to 8 weeks after starting dialysis to obtain this baseline measurement (2–4). This may be because initial instillation of dialysate into the peritoneal cavity and the initiation of PD therapy is associated with mild changes in local cytokine production, peritoneal vascularity and blood flow. These changes in peritoneal anatomy and perfusion could potentially affect peritoneal membrane transport. Historical data have suggested that there is a small increase in the D to P ratio for small solutes during the first month on PD therapy. In addition, measurements should be obtained when the patient is clinically stable and at least 1 month after resolution of an episode of peritonitis, as peritonitis is associated with peritoneal inflammation and subsequent changes in peritoneal transport. With respect to follow-up studies, peritoneal membrane transport testing should be repeated when clinically indicated. Although peritoneal transport is generally stable over time, some studies that evaluated peritoneal transport characteristics over time indicated that peritoneal transport can change in some patients. One of the most frequently noted clinical abnormality is impaired ultrafiltration, the prevalence of which appears to depend on dialysis vintage (5). Thus, it may be necessary to consider re-evaluating the peritoneal equilibration test results on a yearly basis.

Evaluating clearances

With regards to the total solute clearances, the KDOQI Guidelines (1)recommend that renal and peritoneal Kt/V should be measured within the first month after initiating dialysis therapy and at least once every 4 months thereafter. This has been deemed appropriate since the peritoneal Kt/Vurea does not change much over time unless the prescription changes or a change in residual renal function (RRF) is observed. For patients with greater than 100 mL per day of residual kidney volume, 24-hour urine collection for solute clearance and urine volume should be obtained at a minimum of every 2 months or when a decrease in RRF is suspected (such as, decreasing urine output or recent exposure to a nephrotoxin). There is substantial variability in the rate of RRF loss in PD patients(2)Therefore, to prevent patients from falling below the minimum total Kt/Vurea target of 1.7, obtaining a 24-hour urine measurement at this frequency seems appropriate. In addition, it is important to measure clearance when there is a problem, such as can occur with peritonitis episodes. Creatinine clearance can be obtained using 24-hour collection or peritoneal function test.  However, determination of peritoneal creatinine clearance is of little added value for predicting risk for death, but may be used to monitor estimates of muscle mass over time.  During the monthly evaluation of the PD patient, nutritional status should also be estimated(1){C}. Serum albumin levels should be monitored and when obtaining 24-hour total solute clearances, an estimation of dietary protein intake should be undertaken.

References:

  1. K/DOQI Clinical practice guidelines for peritoneal adequacy, update 2006. Am J Kidney Dis. 2006;48 Suppl 1:S91-S97. Available from: https://www.ncbi.nlm.nih.gov/pubmed/16813997.
  2.  Lutes R, Perlmutter J, Holley JL, Bernardini J, Piraino B. Loss of residual renal function in patients on peritoneal dialysis. Adv Perit Dial. 1993;9:165-168. Available from: https://www.ncbi.nlm.nih.gov/pubmed/8105915.
  3. Canada-USA (CANUSA) Peritoneal Dialysis Study Group. Adequacy of dialysis and nutrition in continuous peritoneal dialysis: association with clinical outcomes. J Am Soc Nephrol. 1996;7(2):198-207. Available from: https://www.ncbi.nlm.nih.gov/pubmed/8785388.
  4. Lo W-K, Lui S-L, Chan T-M, Li F-K, Lam M-F, Tse K-C, Tang SC-W, Choy CB-Y, Lai K-N. Minimal and optimal peritoneal Kt/V targets: results of an anuric peritoneal dialysis patient’s survival analysis. Kidney Int. 2005;67(5):2032-2038. Available from: https://www.ncbi.nlm.nih.gov/pubmed/15840054.
  5. Blake PG, Daugirdas JT. Adequacy of Peritoneal Dialysis and Chronic Peritoneal Dialysis Prescription. In: Daugirdas JT, Blake PG, Ing TS, eds. Handbook of Dialysis. 5th ed. Philadelphia, PA: Walters Kluwer Health; 2015:464-482.

P/N 102488-01 Rev. A 07/2015