CAPD adequacy and dialysis morbidity: detrimental effect of a high peritoneal equilibration rate

Conventional urea kinetic modeling and peritoneal equilibration test (PET) were performed on 73 patients undergoing CAPD in order to determine factors influencing morbidity. Dialysis adequacy (KT/V, creatinine clearance, efficacy number) and nutrition (PCR, nPCR, creatinine generation rate, body mass index, albumin, transferrin) were compared to hospital admission days, blood pressure medication, and semiquantitative symptom indices. Renal clearance and dialysis intensity were the primary determinants of dialysis adequacy: patients without renal function required a dialysis intensity of > 0.15 L/kg/day for adequate dialysis, while patients with a renal clearance > 2 mL/min only required 0.1 L/kg/day. Ultrafiltration and PET played a minor role. High peritoneal equilibration rates (PER) were associated with increasing height, chronic glomerulonephritis, and recent peritonitis; low PER with polycystic renal disease and long CAPD duration (for patients without recent peritonitis). There were significant positive correlations between dialysis adequacy indices and nutritional indices: nPCR (p < 0.001); creatinine generation rate (p < 0.001), albumin (p < 0.01), and negative correlations to symptom indices: fatigue (p < 0.01), nausea (p < 0.05), pain (p < 0.05), and symptom index (p < 0.01). Nutritional indices correlated negatively to morbidity indices: 1-year admission rate (p < 0.01), pain (p < 0.01), itching (p < 0.05), edema (p < 0.05). A high PER was a powerful and independent predictor of clinical morbidity:fatigue (p < 0.01), nausea (p < 0.01), pain (p < 0.01), edema (p < 0.05), symptom index (p < 0.001), blood pressure medication (p < 0.01), and 1-year admission rate (p < 0.01).

Adequate dialysis is difficult to obtain in CAPD patients with no renal function, and malnutrition is therefore common. Morbidity improves with increasing nutrition and dialysis intensity, there being no apparent plateau. Creatinine clearance and serum albumin are the most useful indices. A high PER paradoxically predicts a poor clinical outcome, due to increased loss of protein in the dialysate, poor ultrafiltration, and appetite suppression secondary to increased glucose absorption. Patients with a high PER should preferably be treated with nightly peritoneal dialysis or hemodialysis.