Transcapillary Ultrafiltration Research Articles

Effects of tracer, volume, osmolarity and infection on fluid kinetics during CAPD.

A review is given on various aspects of using the disappearance rate of intraperitoneally administered macromolecules for the determination of fluid kinetics in CAPD patients. The rationale and mathematics for the calculation of transcapillary ultrafiltration and of indirect measurement of lymphatic absorption are described. A comparison is made between autologous haemoglobin, human albumin and dextran 70. Dextran 70 appeared most useful; one brand of human albumin increased solute transport. Lymphatic absorption was higher after the installation of a 3-litre dialysate volume than after a 2-litre one, and also higher during peritonitis than after recovery from infection. A gradual increase in intraperitoneal volume, as obtained with glucose 3.86% dialysate, had no apparent effect on the disappearance rate of dextran 70. It is concluded that intraperitoneally administered dextran 70 is a clinically useful marker for the description of fluid kinetics in CAPD patients under various conditions.

Transcapillary Ultrafiltration and Lymphatic Absorption During Childhood Continuous Ambulatory Peritoneal Dialysis

Peritoneal fluid handling depends on a balance between transcapillary ultrafiltration and lymphatic absorption. Lymphatic absorption is reported to be greater in children than in adult continuous ambulatory peritoneal dialysis (CAPD) patients. The present study provides data on peritoneal fluid kinetics in a group of 17 young children (0.4-13 years of age). Net transcapillary ultrafiltration and lymphatic absorption were not dependent on age or duration of treatment. No differences were established from normal values for adult patients reported in the literature.

Pharmacologic Modification of Transperitoneal Movement of Water

Investigations concerning the influence of pharmacologic agents on transperitoneal water movement are predominantly undertaken in the hope that their results can help in a restoration of net ultrafiltration (UF) volume toward normal in cases with declining UF during long-term dialysis treatment. Net UF volume represents the difference between net transcapillary UF and lymphatic absorption. The choice of a pharmacological agent for enhancing UF depends on the mechanisms responsible for net UF loss, which include: (a) early dissipation of the transperitoneal osmotic gradient; (b) decrease in the peritoneal surface area; (c) lymphomonokine overproduction; (d) enhanced lymphatic absorption; (e) high residual volumes left in the peritoneal cavity; or (f) a combination of these factors. Leakage of dialysate to the abdominal wall sometimes occurring in peritoneally dialysed patients (1), according to a definition of net UF volume, cannot be regarded as a true UF loss.

Oral Neostigmine and Lymphatic Absorption in a Myasthenia Gravis Patient on Continuous Ambulatory Peritoneal Dialysis (CAPD)

The effects of oral neostigmine on peritoneal lymph absorption and transcapillary and net ultrafiltration were studied in a myasthenia gravis patient on continuous ambulatory peritoneal dialysis (CAPD). Oral neostigmine decreased lymphatic absorption, but only up to a threshold dose. The effect on net ultrafiltration however was nullified to some extent by a concurrent decrease in cumulative transcapillary ultrafiltration.

Influence of Phosphatidylcholine on Lymphatic Absorption during Peritoneal Dialysis in the Rat

The mechanism whereby i.p. administration of phosphatidylcholine increases net ultrafiltration and solute clearances after long-dwell exchanges is not established. We performed 4-h exchanges in rats using 4.25% dextrose dialysis solution with and without the addition of 50 mgl L phosphatidylcholine. Net ultrafiltration was enhanced in the treated rats (p < 0.005) by a reduction in cumulative lymphatic absorption (p < 0.01) and without a concurrent increase in total net transcapillary ultrafiltration during the dwell time. Likewise, urea and phosphate clearances with i.p. phosphatidylcholine were enhanced mainly by the increase in the drain volume since serum to dialysate solute concentration ratios did not differ significantly between the treated and control rats. Thus, phosphatidylcholine increases net ultrafiltration and solute clearances in the rat by decreasing lymphatic absorption and without increasing transperitoneal transport of water and solutes into the peritoneal cavity. The uptake of the india ink by the lymphatics of rats who received dialysis exchanges without phosphatidylcholine and the lack of uptake in rats treated with phosphatidylcholine are supported by this observation. Reduction in lymphatic absorption with the addition of phosphatidylcholine to the infused dialysis solution offers an alternative means of enhancing the efficiency of long-dwell peritoneal dialysis.

Kinetics of peritoneal dialysis in children: Role of lymphatics

Intraperitoneal fluid is absorbed continuously by convective flow into the peritoneal cavity lymphatics. We evaluated the role of lymphatic absorption in the kinetics of peritoneal dialysis during standardized four hour exchanges in six children using 40 ml/kg of 2.5% dextrose dialysis solution. Cumulative lymphatic absorption averaged 10.4 +/- 1.6 ml/kg and reduced the total net transcapillary ultrafiltration during the dwell time by 73 +/- 10%. Due to the considerable lymphatic absorption rate, maximum intraperitoneal volume was observed before osmolar equilibrium. Extrapolated to four study exchanges per day, lymphatic absorption decreased the potential daily drain volumes in the children by 27 +/- 5% and daily peritoneal urea and creatinine clearances by 24 +/- 4% and 22 +/- 5%, respectively. Compared with four hour exchanges using two liters of 2.5% dextrose dialysis solution in 10 adult CAPD patients with average peritoneal transport, the children had more rapid equilibration of urea, greater absorption of dialysate glucose, higher lymphatic absorption and lower net ultrafiltration (P less than 0.01 to P less than 0.05). Lymphatic absorption therefore causes a relatively greater reduction in net ultrafiltration and solute clearances in children than in adults.

Pharmacological reduction of lymphatic absorption from the peritoneal cavity increases net ultrafiltration and solute clearances in peritoneal dialysis.

Lymphatic drainage from the peritoneal cavity occurs mainly via the subdiaphragmatic stomata and significantly reduces net ultrafiltration and solute clearances during long-dwell peritoneal dialysis. Intraperitoneal cholinergic drugs constrict these stomata and may reduce peritoneal cavity lymphatic absorption. We evaluated ultrafiltration kinetics, solute transport, and lymphatic drainage during single hypertonic exchanges in rats using 2.5% dextrose dialysis solution with and without added neostigmine. Net ultrafiltration was enhanced in the neostigmine group (p less than 0.01) by a reduction in cumulative lymphatic absorption (p less than 0.01) and without an increase in total transcapillary ultrafiltration during the dwell time. Likewise solute clearances were significantly augmented with neostigmine primarily due to the increase in dialysate drain volume (p less than 0.01) since dialysate/serum solute ratios were unchanged. Pharmacological manipulation of peritoneal lymphatic absorption provides an alternative means of increasing the efficiency of long-dwell peritoneal dialysis without altering peritoneal transport of solutes and water.

Contribution of lymphatic absorption to loss of ultrafiltration and solute clearances in continuous ambulatory peritoneal dialysis.

The contribution of peritoneal cavity lymphatic absorption to ultrafiltration kinetics and solute clearances in continuous ambulatory peritoneal dialysis was evaluated in patients with normal (group 1) and high (group 2) peritoneal permeability X area during 4-h exchanges using 2 liters 2.5% dextrose dialysis solution with 30 g added albumin. Cumulative lymphatic drainage in all continuous ambulatory peritoneal dialysis (CAPD) patients averaged 358 +/- 47 ml per 4-h exchange and reduced cumulative net transcapillary ultrafiltration at the end of the exchange by 58 +/- 7.2%. The peak ultrafiltration volume was observed before osmotic equilibrium between serum and dialysate was reached and occurred when the net transcapillary ultrafiltration rate had decreased to equal the lymphatic absorption rate. Thereafter the lymphatic absorption rate exceeded the net transcapillary ultrafiltration rate, and intraperitoneal volume decreased. Extrapolated to 4 X 2 liters, 2.5% dextrose, 6-h exchanges per d, lymphatic drainage reduced potential daily net ultrafiltration by 83.2 +/- 10.2%, daily urea clearance by 16.9 +/- 1.9%, and daily creatinine clearance by 16.5 +/- 1.9%. Although lymphatic absorption did not differ between the two groups, lymphatic drainage caused a proportionately greater reduction in net ultrafiltration in group 2 (P less than 0.025), because these patients had more rapid dialysate glucose absorption (P less than 0.05) and less cumulative transcapillary ultrafiltration (P less than 0.01). These findings indicate that cumulative lymphatic drainage significantly reduces net ultrafiltration and solute clearances in CAPD and that ultrafiltration failure in CAPD occurs when daily lymphatic absorption equals or exceeds daily transcapillary ultrafiltration. Reduction of lymphatic absorption may provide a means for future improvement in the efficiency of CAPD.

The kinetics of ultrafiltration during peritoneal dialysis: The role of lymphatics

Net ultrafiltration was measured directly during hypertonic peritoneal dialysis exchanges in rats. Simultaneously, lymphatic absorption was measured by monitoring the disappearance of albumin in the instilled dialysis solution from the peritoneal cavity. The albumin method for measuring lymphatic absorption was also tested in rats absorbing Lactated Ringer's solution from the peritoneal cavity where absorption rate could also be measured directly. The findings suggest the following: 1.) lymphatic absorption rate is similar with both hypertonic dialysis solutions and Lactated Ringer's solution; 2.) lymphatic absorption is substantial and net ultrafiltration is well below true transcapillary ultrafiltration; and 3.) in our model, lymphatic absorption occurs at a relatively constant rate over six hours of dwell time.