Use of bethanechol chloride to increase available ultrafiltration in CAPD.

Reabsorption of peritoneal dialysis fluid during the prolonged dwell time of continuous ambulatory peritoneal dialysis (CAPD) reduces the efficiency of ultrafiltration and sacrifices effective dialysis adequacy. Studies by Nolph indicate a predominant role of lymphatics in this fluid loss. Khanna has reported that lymphatic flow may be influenced by acetylcholine. This study was designed to determine if bethanechol chloride (BC) would increase the availability of drained volume during CAPD. Nine patients were studied, including 7 patients who exhibited inadequate ultrafiltration. During a 5-day control period, total dialysate drained volume was collected and a standard peritoneal equilibration test (PET) performed. This was followed by a corresponding 5-day test period in which BC (mean dose 0.27 +/- 0.13 mg/kg/day) was administered orally. Drained volume during the control standard 4-hr PET was 1996.68 +/- 279.87 mL. The result for the test period was 2363.33 +/- 321.13 mL (p < 0.05), indicating an 18.4% increase using BC. The PET indicated no change in transport of urea, creatinine, and glucose. In conclusion, the total drained volume can be effectively increased with a subsequent increase in metabolite clearance using BC. Patients exhibiting inadequate ultrafiltration were able to be maintained on CAPD using this cholinergic drug.

Reduction in peritonitis incidence in continuous ambulatory peritoneal dialysis with a new catheter and implantation technique.

Recurrent episodes of peritonitis with the same organism cultured at the catheter exit site suggest that early tunnel colonization is associated with a transfer of these organisms through the catheter tunnel directly from the skin into the peritoneal cavity. In this instance the catheter has failed in its fundamental design to establish and maintain a bacteriological barrier. A three-part study was conducted using the Moncrief-Popovich catheter and implantation technique. The first part of the study included 59 patients who used standard spike exchange systems with this new catheter and implantation technique. A reduction in the incidence of peritonitis occurred in the continuous ambulatory peritoneal dialysis (CAPD) program at the Austin Diagnostic Clinic. The previous peritonitis incidence was 1 every 9 patient-months. This study had 1 every 29 patient-months with 530 patient-months of experience. The second part of the study had 79 patients. All except 11 used disconnect exchange systems. There was a total of 482 patient-months of experience with 1 episode every 27 patient-months. Those using the disconnect systems (86%) had 1 episode every 32 patient-months. The third part of the study included microscopic studies of 12 excised catheters. Three were known to be contaminated. The examiners identified those catheters that were free or nearly free of biofilm on the catheter segment between the two cuffs. It is concluded that biofilm analysis and reduction in peritonitis incidence supports the theory that the new catheter and implantation technique form an improved bacteriological barrier in the access for peritoneal dialysis.

The Moncrief-Popovich catheter. A new peritoneal access technique for patients on peritoneal dialysis.

Existing catheter implantation techniques violate a fundamental premise of wound healing. The immediate presence of the catheter in the post operative surgical wound forms a passage for permanent colonization of the catheter tunnel and cuff(s). This is manifested by the almost universal presence of the biologic products of bacterial growth (biofilm) on the external and internal surfaces of these catheters. The Moncrief-Popovich catheter and implantation technique are designed to address this problem. The Moncrief-Popovich catheter is implanted in the standard fashion, except that the external segment of the catheter is buried subcutaneously at the time of implantation. After allowing 3-5 weeks for tissue in-growth in a sterile environment, a small incision is made in the skin through which the external segment of the catheter is exteriorized and attached to an adapter. A 2 year trial was conducted in 59 patients, comprising 530 patient-months of experience; the incidence of peritonitis was one episode for every 29.4 patient months. All but three of the patients used the standard spike exchange technique. In a recently initiated study using disconnect procedures in 63 of the 74 patients studied, the peritonitis rate was one episode for every 28.7 patient-months; patient-months have totalled 201.2 to date. There was a rate of one exit site infection every 12.57 patients-months. It was concluded that the Moncrief-Popovich catheter and implantation technique result in a substantial decrease in the incidence of peritonitis for patients using the standard spike exchange system.

A distributed model of fluid and mass transfer in peritoneal dialysis.

A mathematical model has been developed to study peritoneal fluid and solute transfer. The model uses the concept of a distributed capillary system within the peritoneal tissue. The model accounts explicitly for transport across the capillary membrane, through interstitial tissue, and across the mesothelium. The capillary and mesothelial membranes are modeled using pore theory and a dual pathway (through pores and across cells) for fluid transfer. The nonperitoneal tissues are modeled as a single body pool. Lymphatic uptake from the peritoneal cavity is included. Model parameters were found from the literature and by simultaneously fitting experimental data for dialysate volume and dialysate concentrations of blood urea nitrogen, glucose, creatinine, and inulin. The model was also shown to predict concentration gradients within several tissues surrounding the peritoneal cavity. Variation of the model parameters revealed the importance of the mesothelial cell layer in peritoneal ultrafiltration. The results of model simulations indicate an initial transfer of fluid from the tissue space to the peritoneal cavity followed by transcapillary fluid transfer.

An hypothesis to explain the ultrafiltration characteristics of peritoneal dialysis.

We present an hypothesis that could account for many characteristics of ultrafiltration and solute movement during peritoneal dialysis. The hypothesis describes transcapillary ultrafiltration and can account for (1) the osmotic effectiveness of rapidly absorbed glucose, (2) small solute sieving in a system permitting protein loss, (3) functional estimates of effective pore sizes as low as 11 A for urea and as high as 62 A for proteins from hydrodynamic analyses, (4) isolated loss of ultrafiltration without loss of clearance, (5) decreased ultrafiltration with decreased clearances, and (6) increased ultrafiltration with decreased clearances. Mechanisms for fluid movement from the peritoneal interstitium into the peritoneal cavity may involve both hydrostatic and osmotic pressure. Interstitial water pathway dimensions, interstitial gel surface charges, mesothelial cell surface charges, and transmesothelial-cell water movement might also account for sieving effects during peritoneal ultrafiltration.

A comparison of peritoneal transport in patients with psoriasis and uremia.

Peritoneal solute equilibration studies during prolonged intraperitoneal dwell were performed in patients with psoriasis and normal renal function, and compared to patients with renal failure undergoing peritoneal dialysis. Calcium, phosphorous, uric acid and protein equilibration were faster in uremics. No differences were observed for sodium and chloride. Mass transfer area coefficients (a measure of the mass transfer at infinite dialysate flow rates) were calculated for glucose, protein and uric acid and found to be complimentary to the results obtained by studies of solute equilibration. Possible reasons for the differences obtained are discussed.

A comparison of the relative efficacy of CAPD and hemodialysis in the control of solute concentration.

Metabolite concentrations found in patients on both continuous ambulatory peritoneal dialysis (CAPD) and hemodialysis are predicted by means of a theoretical transport model. Effects of variation in parameters such as generation rate, mass transfer, coefficients and residual renal clearance are studied. The information obtained indicates that CAPD is as effective as hemodialysis in reducing the concentrations of low molecular weight metabolites occurring in the "average" ESRD patient. CAPD becomes increasingly more effective than hemodialysis as molecular weight increases.

Equilibration of peritoneal dialysis solutions during long-dwell exchanges.

There is an increasing interest in CAPD for the treatment of chronic uremia. This technique uses long-dwell peritoneal exchanges lasting 4 hr or more. We have determined equilibration curves for multiple solutes during long exchanges with commercially available 1.5% and 4.25% dextrose dialysis solutions. For small solutes, rates of change of D/P ratios fall off dramatically after 3 hr of dwell time. For larger solutes, D/P ratios change more linearly. Some concentration gradients for net removal by diffusion persist well beyond 4 hr for all but the most highly diffusible solutes. Previously reported net sieving of sodium and chloride during hypertonic exchanges is still evident after many hours.

Continuous ambulatory peritoneal dialysis.

The technique of continuous ambulatory peritoneal dialysis was evaluated in nine patients during 136 patient weeks. The major objectives were to see if continuous ambulatory peritoneal dialysis would provide [1] acceptable control of serum chemistries by usual criteria, [2] adequate removal of sodium and water, [3] tolerable protein losses, and [4] a low prevalence of peritonitis with episodes responsive to therapy with continuing continuous ambulatory peritoneal dialysis. Preliminary findings suggest continuous ambulatory peritoneal dialysis represents an effective ambulatory, portable, internal dialysis technique. Larger-solute clearances per week may approach values six times greater than with most hemodialysis techniques. Small-solute clearances approach dialysate flow rate (8.3 ml/min) and are comparable to other dialysis techniques on a weekly basis. Edema is readily controlled and protein losses should be tolerable with adequate protein intake. Peritonitus occurs on the average every 10 weeks but responds to therapy promptly with continuing continuous ambulatory peritoneal dialysis. If the prevalence of peritonitis can be reduced, continuous ambulatory peritoneal dialysis appears to represent a very attractive dialysis technique.