Karl D. Nolph

The objective of this study was to evaluate the association of peritoneal membrane transport with technique and patient survival. In the Canada-USA prospective cohort study of adequacy of continuous ambulatory peritoneal dialysis (CAPD), a peritoneal equilibrium test (PET) was performed approximately 1 mo after initiation of dialysis; patients were defined as high (H), high average (HA), low average (LA), and low (L) transporters. The Cox proportional hazards method evaluated the association of technique and patient survival with independent variables (demographic and clinical variables, nutrition, adequacy, and transport status). Among 606 patients evaluated by PET, there were 41 L, 192 LA, 280 HA, and 93 H. The 2-yr technique survival probabilities were 94, 76, 72, and 68% for L, LA, HA, and H, respectively (P = 0.04). The 2-yr patient survival probabilities were 91, 80, 72, and 71% for L, LA, HA, and H, respectively (P = 0.11). The 2-yr probabilities of both patient and technique survival were 86, 61, 52, and 48% for L, LA, HA, and H, respectively (P = 0.006). The relative risk of either technique failure or death, compared to L, was 2.54 for LA, 3.39 for HA, and 4.00 for H. The mean drain volumes (liters) in the PET were 2.53, 2.45, 2.33, and 2.16 for L, LA, HA, and H, respectively (P < 0.001). After 1 mo CAPD treatment, the mean 24-h drain volumes (liters) were 9.38, 8.93, 8.59, and 8.22 for L, LA, HA, and H, respectively (P < 0.001); the mean 24-h peritoneal albumin losses (g) were 3.1, 3.9, 4.3, and 5.6 for L, LA, HA, and H, respectively (P < 0.001). The mean serum albumin values (g/L) were 37.8, 36.2, 33.8, and 32.8 for L, LA, HA, and H, respectively (P < 0.001). Among CAPD patients, higher peritoneal transport is associated with increased risk of either technique failure or death. The decreased drain volume, increased albumin loss, and decreased serum albumin concentration suggest volume overload and malnutrition as mechanisms. Use of nocturnal cycling peritoneal dialysis should be considered in H and HA transporters.

We initiated a therapeutic program of continuous ambulatory peritoneal dialysis for patients with chronic renal failure. Our program resulted in many episodes of peritonitis arising from contamination due to the technical aspects of the procedure. Microbiologic evaluation showed that 73% of 97 episodes were culture positive, with gram-positive organisms causing most of the cases, especially early in dialysis. Gram-negative rods tended to occur later. Gram stains of dialysate effluent resulted in a disappointingly low yield of only 9% positivity. Cell counts were a dependable indicator of the presence of peritoneal inflammation and also of therapeutic success. Most patients responded well to intraperitoneal cephalothin, 125 mg/L for 10 to 14 d. The occurrence of peritonitis resulted in 0.93 years of hospitalization during the total of 15.45 patient-years on dialysis, which essentially negated the financial advantages of this method of treatment of chronic renal failure. For this to be a successful mode of therapy, advances in the prevention of peritonitis must be made.

A retrospective investigation was undertaken in which the rate of decline of residual renal function (RRF), estimated from creatinine clearance, was compared in 55 continuous ambulatory peritoneal dialysis (CAPD) and 57 hemodialysis (HD) patients for whom a minimum of four (mean of 7.6) well-spaced historic measurements of residual clearance were available. Because of the intrinsic variability that attends such data, specialized nonlinear, growth curve statistical methods were employed. Residual function was found to decline exponentially after the onset of therapy in both cohorts. The rate of decline in the HD group was twice that of the CAPD group (5.8% +/- 0.4% per month for HD vs 2.9% +/- 0.3% per month for CAPD; difference significant at p less than 0.0001). This difference remained highly significant (p less than 0.01) when corrected for other potential risk factors such as age, gender, hypertensive status, and use of angiotensin converting enzyme inhibitors in patients with diabetic or other forms of glomerular nephropathy. Differences between cohorts were not significant for patients with other diagnoses (p greater than 0.1) although the size of some of these subsets was very small. The physiologic mechanism for the more rapid fall-off of RRF on HD remains speculative, but could be related to renal ischemia secondary to intratreatment hypovolemia and/or to nephrotoxic effects of the inflammatory mediators of extracorporeal circulation.

The KT/V urea index (K, clearance; T, treatment time; V, volume of urea distribution) has become an established index of hemodialysis (HD) adequacy, values of KT/V less than 0.8 being associated with overt uremic toxicity. For the typical continuous ambulatory peritoneal dialysis (CAPD) regimen of 4 X 2 L exchanges/day, the equivalent KT/V approximately 0.6. Paradoxically, overt uremic toxicity is not commonly observed in CAPD patients with this typical therapy prescription. Application of the urea kinetic model demonstrates that HD and CAPD have the same time-averaged urea concentration at the same KT/V. However, as HD is an intermittent therapy, the urea concentration in HD exceeds the time-averaged concentration for about half the hours in the week. If uremic toxicity is related to the peak rather than the time-averaged urea concentration, a higher KT/V would be required in HD to achieve a peak concentration at or below the steady-state CAPD concentration. This peak concentration hypothesis predicts, based on the results of the National Cooperative Dialysis Study, that underdialysis with CAPD would occur at KT/V less than 0.4 for a protein intake of 1.1 gm/kg/day.