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P C Farrell

Publications and source records attributed to P C Farrell.

66 records · Page 4Linked to original sources
PubMedDate not supplied

Theoretical considerations on molecular transport in dialysis and sorbent therapy for uremia.

The technology of uremic blood purification has grown rapidly over the past decade and has provided the clinician with a wide range of therapeutic options. These options involve mass transfer processes which may be primarily due to diffusion or convection, or a combination of both mechanisms. However, regardless of the mechanism of molecular transport, evaluation of the clinical utility of these therapies requires studies which provide sufficient data to solve the appropriate rate equations and to close mass balances. Data from the recent hemodialysis, peritoneal dialysis and sorbent literature are analyzed to show the magnitude of variability in both patient and therapy-related mass balance paramters for urea nitrogen (U) and middle molecules (MM) and to provide unambiguous comparisons for some of these therapies. A theoretical model is developed to describe sorbent-mediated gut elimination of solute as a first-order clearance limited by sorbent saturation. The model is used to analyze data in the literature on AL (OH)3 facilitated gut clearance of phosphate and indicates a gut P clearance of approximately 20 ml/min with maximum removal of approximately 800 mg P/24 hrs. Similar analysis of oxystarch indicated a gut U clearance of 2.5 ml/min and maximum removal of 1.5 gm/24 hrs.

Absorption↗
PubMedDate not supplied

Plasma water filtration and lymphatic uptake during peritoneal dialysis.

To clarify further the extent, pathways, and significance of convective transport during peritoneal dialysis, acute transport studies were conducted in which five continuous ambulatory peritoneal dialysis (CAPD) patients underwent 6 hr dialyses (2 L infusate with 2.25% dextrose) on 2 successive days, with multiple sampling of both blood and peritoneal dialysate. Concentrations of permeants (urea, creatinine, uric acid, beta 2 microglobulin, and apolipoprotein A) and a radiolabeled marker (125I-polyvinyl pyrollidone [PVP]) were determined at 20-30 min intervals in dialysate and every 90 min in plasma. Intraperitoneal volumes and lymphatic flows were calculated from rates of dilution and disappearance of 125I-PVP. Intratreatment lymphatic flow rate averaged 76 +/- 15 ml/hr. Although lower than observed in small animal models and reported by some clinical groups, this level of lymphatic drainage was still sufficient to decrease net patient weight loss by approximately 50% and to resorb approximately 15% of metabolites in the peritoneal cavity, independent of molecular weight. Transcapillary ultrafiltration ranged from 7.4 +/- 1.5 ml/min at 10 min into the exchange to 1.3 +/- 1.5 ml/min at 345 min. Reverse ultrafiltration, from the peritoneal cavity back through capillary vasculature to the patient, was not observed in any patient in this study.

Ascitic Fluid↗
PubMedDate not supplied

The influence of dialysis treatment modality on the decline of remaining renal function.

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.

Female↗