Abstract P1-15-20: DIetary REstriction as an adjunct to neoadjuvant ChemoTherapy for HER2-negative breast cancer: Final results from the DIRECT trial (BOOG 2013-04)

Background:

Short term fasting (STF) protects from toxicity, while enhancing the efficacy of chemotherapy in cancer bearing mice and is a promising strategy to enhance the efficacy and tolerability of chemotherapy in humans. A specifically designed low calorie, low amino acid substitution diet (“Fasting Mimicking Diet”, FMD) has similar effects in vivo during chemotherapy as STF. The DIRECT trial evaluates the impact of FMD on toxicity and efficacy of neoadjuvant chemotherapy in women with HER2-negative early breast cancer.

Patients and methods:

Eligible patients had histologically confirmed, HER2-negative, stage II/III early breast cancer, adequate bone marrow, liver and renal function, BMI > 19kg/m2 and absence of diabetes mellitus. Women receiving 8 neo-adjuvant AC-T courses (adriamycin/cyclophosphamide - docetaxel) or 6 FEC-T courses (5-fluorouracil, epirubicin and cyclophosphamide - docetaxel); day 1, q 3 weeks, were randomized to receive FMD or regular diet for 3 days prior to and at the day of chemotherapy and 3 days prior to surgery. The FMD group received no dexamethasone during the AC or FEC courses. The primary endpoint of the phase II part was feasibility and grade III/IV toxicity and of the phase III pathological complete response (pCR) rate. Additionally, in a side study increase in DNA damage in lymphocytes before and three hours after chemotherapy was compared between the 2 arms.

Results

From February 2014 to January 2018 131 patients from 11 participating Dutch centers were randomized, whereof 100 received AC-T and 31 received FEC-T. Sixty-six of the patients received FMD. Compliance to the diet was low as 32% fasted at least half of the cycles and 24% of patients fasted during all of cycles. The main reasons of non-compliance were food aversion induced by chemotherapy and the taste of the diet. Intention to treat grade III/IV toxicity was not significantly different between the standard arm (67,2%) and in the FMD arm (79,4%), although the majority of the toxicities in the FMD arm were assessed in patients that did not complete the FMD diet preceding the measurements. The total overall pCR rate was 12,8%, lower than assumed in the sample size calculation and would therefore need minimally a doubling in patient numbers to be able to reach the expected pCR difference between both arms. Due to the poor compliance, slow accrual rate and low overall pCR rate the DIRECT study terminated after completion of the phase II part. Subgroup analysis will be presented at SABCS. In a side study, DNA damage after chemotherapy was significantly less increased in lymphocytes in the FMD group as compared to the control group (p=0.043).

Conclusion

The effect of STF on toxicity and efficacy of chemotherapy was not established due to poor compliance, however STF by FMD reduced a transient increase in chemotherapy induced DNA damage. Close monitoring of patients by nutritionists with expertise in low calorie diets as well as diets with a more variable taste are probably needed to successfully examine the impact on adverse effects and tumor biology.

Citation Format: de Groot S, Lugtenberg RT, Welters MJ, Ehsan I, Vreeswijk MP, Smit VT, de Graaf H, Heijns JB, Portielje JE, van de Wouw AJ, Imholz AL, Kessels LW, Vrijaldenhoven S, Baars A, Meershoek-Klein Kranenbarg E, Duijm-de Carpentier M, van Leeuwen-Stok E, Putter H, Longo VD, van der Hoeven JJ, Nortier JW, Pijl H, Kroep JR. DIetary REstriction as an adjunct to neoadjuvant ChemoTherapy for HER2-negative breast cancer: Final results from the DIRECT trial (BOOG 2013-04) [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P1-15-20.

Similarities and differences between the effects of amino acids and nitroprusside on peritoneal permeability during CAPD

OBJECTIVE

Intraperitoneal administration of amino acid based dialysis solutions affects the surface area available for diffusion, with almost no effect on the intrinsic permeability to macromolecules. Intraperitoneally administered nitroprusside affects the vascular surface area and the intrinsic permeability without effect on the peritoneal blood flow. In the present study, these differences were translated into different effects on the radii of the pores in the peritoneal membrane.

METHODS

Effects of amino acid based dialysate and nitroprusside on peritoneal permeability characteristics were evaluated in standard peritoneal permeability analyses with L-arginine-containing amino acid dialysate (10 patients) or with 1.36% glucose dialysate with nitroprusside (10 patients). In each patient a control experiment with 1.36% glucose was performed. Kinetic modeling was done to analyze the effects in terms of the pore theory.

RESULTS

Both interventions increased the mass transfer area coefficients of low molecular weight solutes. This is in accordance with an increase in the unrestricted area over diffusion distance found with modeling. With amino acids almost no effect was found on the protein clearances; the increase in the large-pore radius was only small. Nitroprusside induced a marked increase in protein clearances. This was in accordance with an evident increase in the average large-pore radius.

CONCLUSIONS

Amino acids affect the radii of the small pores and the large pores to the same extent. Nitroprusside influences especially the large pores. Both amino acids and nitroprusside are vasoactive, although the effects on the peritoneal microcirculation are different.

Correction of sodium sieving for diffusion from the circulation

Transcellular water transport (TCWT) can be estimated by Na- sieving. However, the assumption that the initial Na+ dialysate concentration (D0) is equal to the initial plasma concentration (P0) is not true for each patient. The difference leads to Na+ diffusion from the circulation to the dialysate, which diminishes the Na+ sieving. A model was developed to distinguish transcellular water transport from Na+ diffusion. We previously found evidence that the mass transfer area coefficient of urate (MTACurate) was similar to the MTACNa+. The MTAC is the product of the elimination constant (ke) and the volume of distribution (VD), the mean intraperitoneal volume. Because VD is known, the ke Na+ in each patient can be equated with the ke urate. The Na+ mass transfer from the circulation to the dialysate by diffusion can then be calculated for any time point during a dwell (Dt). Dt was subtracted from the measured Na+ dialysate concentration at 60 minutes. The corrected D/P Na+ then represents the actual Na+ sieving. Using 3.86% glucose dialysate, this approach was investigated in 15 stable peritoneal dialysis (PD) patients (normUF) and in 9 PD patients with low ultrafiltration (lowUF, < 400 mL/4 hours). The MTACurate was calculated according to Waniewski (W) and according to the Garred model (G). Similar calculations were also performed for the MTAC of creatinine (MTACcreat). Initial D/P Na+ was not different between the groups. When no diffusion correction was made, D/P60 Na+ in the lowUF group (median 0.898, range 0.870-0.949) was significantly higher (p < 0.025) than D/P60 Na+ in the normUF group (median 0.881, range 0.816-0.899). The difference disappeared after diffusion correction regardless of the correction model applied. However, at 240 minutes, D/P Na+ in the normUF group was significantly lower than in the lowUF group (median 0.880, range 0.839-0.952 vs median 0.942, range 0.866-0.987; p < 0.004). Even after correction, D/P Na+ in the normUF group was significantly lower: 0.847 normUF versus 0.893 lowUF (Wurate, p < 0.005); and 0.842 normUF versus 0.890 lowUF (Gcreat, p < 0.003). The correlation between the Wurate (the best theoretical diffusion correction) and Gcreat (the least) was: y = 0.99x + 0.0037. Furthermore, Bland and Altman analyses of Wurate and Gcreat at both 60 and 240 minutes resulted in random distribution around the means, with a slight overestimation in relation to the magnitude of Gcreat, as was expected. Gcreat can be used to make an accurate estimation of the contribution of Na+ diffusion in the time course of D/P Na+. It provides a simple way to more precisely determine Na+ sieving, and therefore TCWT. In conclusion, to avoid overestimation of impaired channel-mediated water transport, a Na+ diffusion correction should be made when D0 is not equal to P0 or in the case of a large vascular surface area.

Day-to-day variability of fluid and solute transport in upright and recumbent positions during CAPD

BACKGROUND

The effect of posture on peritoneal transport characteristics during CAPD is unpredictable because (1) although the capillary pressure is higher in the upright position, the intraperitoneal pressure is also elevated, and (2) the contact of dialysate with the subdiaphragmatic lymphatics is probably more extensive during recumbency.

METHODS

In eight CAPD patients, six peritoneal permeability tests (4 h, glucose 2.27%, dextran 70 as volume marker) were performed within 2 weeks, while the body posture was either recumbent (3 tests) or upright (3 tests). In addition, intraperitoneal pressure measurements were done in the recumbent and upright positions.

RESULTS

The intraperitoneal pressure, not corrected for the contribution of the hydrostatic column, was higher in upright position (12.6 +/- 0.8 mmHg, mean +/- SEM) than during recumbency (6.7 +/- 0.8; P < 0.0005). Net ultrafiltration rate was lower when upright: 0.96 +/- 0.09 ml/min/1.73 m2, compared to 1.14 +/- 0.12 in the supine position (P < 0.05). This was achieved because the effective lymphatic absorption rate was marginally higher and the transcapillary ultrafiltration rate was slightly lower in the upright position. The mass transfer area coefficient of creatinine, representing effective peritoneal surface area, decreased from 10.7 +/- 1.3 ml/min/1.73 m2 (recumbent) to 9.9 +/- 1.4 (upright; P = 0.08). The clearances of five serum proteins decreased more the higher the molecular weight. As a consequence the restriction coefficient was 2.07 +/- 0.09 (recumbent) vs 2.23 +/- 0.08 (upright; P = 0.06). Hence the intrinsic permeability to macro-molecules was higher during recumbency. The intraperitoneal pressure was correlated with the net ultrafiltration rate (r = -0.71, P = 0.05) only during recumbency. In upright position relations were found between the effective lymphatic absorption rate and the mass transfer area coefficients of low molecular solutes. The coefficients of variation of fluid and solute parameters were not different between both positions.

CONCLUSIONS

It is concluded that the decrease in net ultrafiltration rate in the upright position is only small and probably caused by counteracting effects of a higher intra-abdominal pressure and the effect of gravity. The upright position also led to only small decreases in solute transport parameters.

Icodextrin's effects on peritoneal transport

OBJECTIVE

To give a survey of the principles of peritoneal fluid transport in general, followed by an analysis of the effects of icodextrin on the transport of fluid and solutes.

DESIGN

A review of the literature and of data on the effects of icodextrin in continuous ambulatory peritoneal dialysis (CAPD) patients at the Academic Medical Center, Amsterdam.

RESULTS

Icodextrin had no effect on the mass transfer area coefficients of low molecular weight solutes. Also no effect was found on the clearances of albumin and larger serum proteins. Due to convective transport, the clearance of beta 2-microglobulin was greater with icodextrin than with glucose solutions. Icodextrin was especially superior to glucose in the induction of net ultrafiltration during long dwells, during peritonitis, and in patients with ultrafiltration failure caused by a large effective peritoneal surface area.

CONCLUSION

Icodextrin has no effect on the permeability characteristics of the peritoneal membrane, but increases convective flow through the small-pore system. As a result, the peritoneal clearance of beta 2-microglobulin is higher than with glucose-based solutions. Icodextrin is especially indicated for long dwells and in patients with impaired ultrafiltration caused by a large peritoneal surface area, leading to high transport rates of low molecular weight solutes.

Effect of electric charge on the transperitoneal transport of plasma proteins during CAPD

BACKGROUND

Controversy exists as to whether electric charges of plasma proteins influence their transport across the peritoneal membrane during CAPD. Fixed negative charges in the peritoneal membrane are diminished during peritonitis in rats.

METHODS

Peritoneal clearances of 10 proteins and their isoforms were used to establish the relationship between peritoneal clearance and molecular weight. The observed protein clearances were compared with the predicted clearances based on molecular weight. Clearances of proteins with different charge but identical size were compared. Stable patients and peritonitis patients were compared. Results. Only the peritoneal clearance of lipase, LDH 4/5 and IgG3 were significantly different from the predicted values (P<=0.05). The peritoneal clearance of slightly anionic beta2 microglobulin (1072 microl/min) and cationic lysozyme (572 microl/min) showed no evidence for charge selectivity; neither did the peritoneal clearance of slightly anionic transferrin (86 microl/min) and highly anionic albumin (99 microl/min). The peritoneal clearance of IgG1, IgG2 and IgG4 were identical (32, 31 and 31 microl/min), despite their different charge. The peritoneal clearance of cationic LDH 4/5 was 137 microl/min and higher than the peritoneal clearance of neutral LDH 3 (97 microl/min, P=0.01) and LDH 1 (59 microl/min, P=0. 02). These results suggested charge selectivity; however in five additional patients during peritonitis the peritoneal clearance of LDH 4/5 increased to 10 times the peritoneal clearance of LDH 1. Local LDH isoenzyme release from the cells present in the dialysate was shown to be responsible in stable and peritonitis patients. Likewise, the higher peritoneal clearance of neutral pancreatic amylase (234 microl/min) compared to anionic salivary amylase (142 microl/min, P=0.03) could probably be attributed to local release of the former from the pancreas, as the peritoneal clearance of lipase (highly anionic) was higher than predicted and the difference remained during peritonitis.

CONCLUSIONS

The peritoneal membrane constitutes a size- but probably not a charge-selective barrier for the transport of macromolecules between blood and dialysate during stable CAPD.

IgG subclasses in CAPD patients

OBJECTIVE

To make a comparison of serum levels of immunoglobulin G (IgG) subclasses in adult continuous ambulatory peritoneal dialysis (CAPD) patients with those in age- and sex-matched hemodialysis patients and healthy volunteers, and to analyze the contribution of removal of these proteins in peritoneal effluent to their plasma values.

DESIGN

A cross-sectional study.

SETTING

A renal unit of a university hospital.

PATIENTS

Twenty-three CAPD patients, 21 hemodialysis patients, and 21 healthy volunteers. Peritoneal transport studies were done in 8 of the 23 CAPD patients.

METHODS

IgG subclasses were measured in serum by nephelometry. For the peritoneal transport studies an ELISA method on ethylenediamine tetracetic acid plasma was used. The same method was used in seven-to-ten-fold concentrated peritoneal dialysate.

RESULTS

CAPD patients had lower IgG2 and IgG4 levels than hemodialysis patients and healthy volunteers (p < 0.01). IgG2 values below 1.5 g/L were present in 43% of the CAPD patients (p < 0.001 compared to healthy volunteers). Peritonitis incidence was not different between CAPD patients with low or normal IgG2 plasma levels. Peritoneal clearance of IgG3 was lower than that of the other subclasses. Evidence was obtained for a depressed synthesis of IgG2 and IgG4 in CAPD patients. The hypothesis that interleukin-2 may be involved in the low synthesis rate of IgG2 is discussed.

CONCLUSION

Low serum IgG2 and IgG4 levels are present in stable, adult CAPD patients. These were not caused by increased peritoneal loss, but by decreased synthesis.

Fluid kinetics in CAPD patients during dialysis with a bicarbonate-based hypoosmolar solution

The magnitude of transcapillary backfiltration by the colloidosmotic pressure within the peritoneal capillaries compared to the effective lymphatic absorption was investigated in continuous ambulatory peritoneal dialysis patients. This was done during a 4-hour dwell period, using a hypoosmolar dialysis fluid (280 mosm/kg H2O) in 8 patients and compared to 5 of these patients using a 1.36% glucose (GS; 324 mosm/kg H2O). The low molecular weight solute transport did not differ between the two solutions. The intraperitoneal dextran 70 concentration increased during the dwell with the hypoosmolar dialysis fluid (from 770 to 945 mg/l; p = 0.000002) and decreased with the GS (from 859 to 719 mg/l; p = 0.007). With the GS the transcapillary ultrafiltration was directed towards the abdominal cavity during the dwell period. With the hypoosmolar fluid, the transcapillary ultrafiltration was continuously directed towards the circulation. In this solution, the magnitude of transcapillary backfiltration due to colloidosmotic pressure within the peritoneal capillaries was 0.4 +/- 0.1 ml/min. In conclusion, intraperitoneal markers can be used in continuous ambulatory peritoneal dialysis patients for determination of effective lymphatic absorption and transcapillary fluid passage in both transport directions.

The standard peritoneal permeability analysis: a tool for the assessment of peritoneal permeability characteristics in CAPD patients

Peritoneal transport characteristics in CAPD patients are often assessed by the peritoneal equilibration test (PET), which uses a four hour dwell with glucose 2.27% dialysate. From the test, the dialysate/plasma ratio of creatinine (D/PCr), the dialysate/initial dialysate ratio of glucose (D/Do) and net ultrafiltration (NUF, drained minus instilled volume) are calculated. The standard peritoneal permeability analysis (SPA) is a modification and extension of the PET: glucose 1.36% dialysate is used, to which dextran 70 (1 g/liter) is added for the calculation of fluid kinetics. Mass transfer area coefficients (MTAC's) of low molecular weight solutes, clearances of proteins and the change in intraperitoneal volume (delta IPV) can be assessed. In this study the SPA was analyzed, and a comparison with the PET was made. A total number of 138 SPA's was analyzed in 86 different clinically stable patients. Normal values were calculated for both SPA and PET parameters in the same tests. Median (ranges) of comparable transport parameters from SPA and PET were: MTACCr, 10.4 ml/min (5.7 to 19.3); glucose absorption, 61% (35 to 87); delta IPV, 9.5 ml (-761 to 310); D/PCr, 0.76 (0.53 to 1.14); D/D0, 0.37 (0.13 to 0.56); NUF, -75 ml (-675 to 450). The agreement between SPA and PET was analyzed using the method of Bland and Altman. A fairly good agreement was present between NUF and delta IPV. Systematic errors were found when D/PCr and MTACCr were compared: D/P overestimated MTAC mainly in the low range, whereas in the high range values were underestimated. A similar pattern was seen for the transport parameters of glucose. In 40 patients negative net ultrafiltration was present, and possible reasons for this were assessed. In 9 patients no reason could be identified. It can be concluded that the SPA provides useful and extensive information on peritoneal transport parameters. Compared to the PET, the SPA has better discriminative power for the transport of glucose and creatinine.

Appearance of tumor necrosis factor-alpha and soluble TNF-receptors I and II in peritoneal effluent of CAPD

Dialysate and serum concentrations of tumor necrosis factor-alpha (TNF-alpha), soluble TNF-receptor I (sTNFRI) and soluble TNF-receptor II (sTNFRII) were measured during stable and infectious CAPD to determine whether these mediators are released intraperitoneally or derived from the circulation. Dialysate/serum ratios were compared to those of various marker proteins for peritoneal transport and to interleukin-6 (IL-6), which is locally produced. Peritoneal immunoreactive TNF-alpha could be detected in 19 of 20 stable CAPD patients after a night dwell, but only occasionally and in lower concentrations during and after a standard four-hour peritoneal permeability test. Both sTNFRs highly exceeded TNF-alpha dialysate concentrations. In case of peritonitis a median 16-fold increase in dialysate TNF-alpha occurred on the first day, which declined towards control values during a longitudinal follow-up of eight consecutive days. sTNFRI and sTNFRII in dialysate increased three- to fourfold. Their peaks, however, appeared on the second peritonitis day. Bioactive TNF-alpha was only detected when immunoreactive levels exceeded 1000 pg/ml. Serum values of all variables were not altered during infection; sTNFRs exceeded TNF-alpha 300- to 400-fold. During stable CAPD indirect evidence was obtained for transperitoneal transport from plasma to dialysate of TNF-alpha (molecular wt 17 kD), sTNFRI (55 kD) and sTNFRII (75 kD). Dialysate/serum (D/S) ratios were higher, the lower the molecular weight; they were related to D/S ratios of those marker proteins with the nearest molecular weight; D/S ratios were unrelated to the intraperitoneally produced IL-6. Furthermore, the observed D/S ratios were as expected theoretically for their molecular weights.(ABSTRACT TRUNCATED AT 250 WORDS)

Fluid and solute transport in CAPD patients using ultralow sodium dialysate

Transcapillary ultrafiltration during CAPD is determined by the ultrafiltration coefficient of the peritoneal membrane and by Starling forces, the latter being mainly determined by the osmolality of the dialysate. Dialysate sodium concentration decreases during a dwell, implying that: (1) sodium passes the peritoneal membrane to a lesser extent than H2O, and (2) more H2O than sodium is removed in overhydrated patients. We therefore compared two dialysate solutions with similar osmolality, but different sodium concentration (Na+ 129 mmol/liter and 102 mmol/liter). Two peritoneal permeability tests (2 x 6 hrs, dextran 70 as volume marker) with an interval of two days were performed in 10 CAPD patients. Transcapillary ultrafiltration rate was higher with ultralow sodium dialysate (USD) than normal sodium dialysate (NSD): 1.80 +/- 0.16 ml/min versus 1.58 +/- 0.18 (P < 0.01). It was especially higher during the last two hours of the dwell: 0.49 +/- 0.12 ml/min (USD) versus 0.27 +/- 0.13 (NSD). The effective lymphatic absorption rate was not different: 1.01 +/- 0.12 ml/min (USD) versus 1.05 +/- 0.09 (NSD). Using two different kinetic models, the reflection coefficients for glucose, sodium and chloride were 0.032, 0.029 and 0.027 (for the convection model) and 0.033, 0.030 and 0.027 (for the diffusion model). As a consequence the decline in osmotic pressure was more gradual during the exchange with USD. The peritoneal membrane characteristics, that is the effective peritoneal surface area and the peritoneal restriction coefficient, were not altered by the composition of the dialysate.(ABSTRACT TRUNCATED AT 250 WORDS)

Clinical significance and detection of individual differences and changes in transperitoneal transport

A review is given on the pathophysiology of the transport of solutes and fluid during continuous ambulatory peritoneal dialysis. Special attention is paid to the assessment of peritoneal permeability in individual patients, its inter- and intraindividual variability, the effect of systemic disease, some regulatory mechanisms, and alterations observed during long-term continuous ambulatory peritoneal dialysis.

Effect of an increased intraperitoneal pressure on fluid and solute transport during CAPD

The effect of an increased intraperitoneal pressure on fluid and solute transport was studied in eight stable CAPD patients. Two permeability tests of two hours each with continuous registration of the intraperitoneal pressure were performed while patients were in supine position. The intra-abdominal pressure was raised by means of a tightening girdle with inflatable cuffs in one of the experiments. Intraperitoneally administered dextran 70 was used as a volume marker in order to determine the peritoneal fluid kinetics. The increment in the intra-abdominal pressure of 10.0 +/- 1.0 mm Hg caused a decline in the net ultrafiltration. This was mainly determined by an increase in the lymphatic absorption: 1.07 +/- 0.18 ml/min (without compression) versus 1.86 +/- 0.25 ml/min (with compression; P < 0.01), whereas the transcapillary ultrafiltration rate tended to decrease: 2.02 +/- 0.23 versus 1.73 +/- 0.27 ml/min (P = 0.08). External compression also diminished solute transport from the circulation to the peritoneal cavity. The decline in the mass transfer area coefficient of urea, creatinine, urate and beta 2-microglobulin was 13%, indicating a smaller effective peritoneal surface area caused by external compression probably due to a decrease in the number of the perfused peritoneal capillaries. The fall in the peritoneal protein clearances was more pronounced the higher the molecular weight of the protein, consistent with a decline in the intrinsic permeability of the peritoneum. Kinetic modeling using computer simulations was used to analyse these effects in terms of the pore theory, using a convection model (large pore radius 184 +/- 14 A) and a diffusion model (large pore radius 1028 +/- 218 A) for the transport of macromolecules.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of dialysate osmolarity on the transport of low-molecular weight solutes and proteins during CAPD

Osmotic-induced fluid and solute transport was studied in ten stable CAPD patients, who were examined twice within one week, using dialysate with 1.36% glucose on the first and 3.86% glucose on the second day. Peritoneal fluid kinetics were determined using intraperitoneally administered dextran 70 as a volume marker. After a four-hour dwell period, an increase in mean transcapillary ultrafiltration rate (TCUFR) with 3.86% glucose compared to 1.36% glucose was found (3.40 +/- 0.62 ml/min vs. 1.20 +/- 0.57, P < 0.001), but the lymphatic absorption was unchanged (1.32 +/- 0.10 ml/min vs. 1.42 +/- 0.15). The increased TCUFR resulted in a higher clearance of beta 2-microglobulin, but no differences were present in the clearances of albumin, transferrin, IgG, IgA and alpha 2-macroglobulin. This is consistent with the two pore theory for transcapillary transport with a small pore size of less than 40 A. The contribution of osmotic induced convection to the total transport of beta 2-microglobulin was small (6% during 1.36% glucose, 16% during 3.86% glucose), suggesting that macromolecules are mainly transported by diffusion or hydrostatic convection. The peritoneal restriction coefficient was 2.37 +/- 0.04, indicating restricted diffusion for macromolecules. In contrast, the restriction coefficient for low-molecular weight solutes was 1.24 +/- 0.03, in accordance with a process of mainly unrestricted diffusion for solutes smaller than 16 A. Higher values of protein clearances were found during the first hour of dialysis compared with the subsequent hours.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of glucose polymers on water removal and protein clearances during CAPD

Two selected groups of 5 continuous ambulatory peritoneal dialysis (CAPD) patients (3 female, 7 male), mean age 60 years, were studied twice with an interval of 4 weeks. The first study was done with glucose-containing dialysate and the second study with dialysate containing glucose polymers (Dextrin 7.5%) after they had been treated with this solution (night dwell) for 4 weeks. The patients collected night bags for 3 consecutive days during the tests. Protein clearances were determined for beta 2-microglobulin, albumin, IgG, fibronectin, and alpha 2-macroglobulin in both periods to examine the influence of crystalloid-induced convection versus "colloid"-induced convection. Group I normally used 1.50% glucose and was therefore considered to have a "high ultrafiltration";group II was the "low ultrafiltration" group because they needed 4.25% glucose dialysate. For their usual glucose solutions the net ultrafiltration was not different between both groups, but the clearance of beta 2-microglobulin was higher in group II:839 +/- 98 microL/min (group I) and 1135 +/- 131 microL/min (group II) (p = 0.08). For glucose polymers the net ultrafiltration increased in both groups, but this was more pronounced in group II: 657 +/- 104 mL (group I) and 918 +/- 85 mL (group II) (p = 0.06). Also, the clearance of beta 2-microglobulin increased with the glucose polymer solution: 1268 +/- 94 microL/min (for glucose polymer) and 987 +/- 85 microL/min (for glucose) (p < 0.05), but the clearances of the larger serum proteins remained unaffected.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

Use of the disappearance rate for the estimation of lymphatic absorption during CAPD

Several studies are discussed which investigated the usefulness of the disappearance rate of macromolecules from the peritoneal cavity for estimating convective fluid loss from the peritoneal cavity into the peritoneal lymphatic system. It is shown that dextrans are removed from the peritoneal cavity by a size-independent process at a mean rate of 1.37 +/- 0.15 ml/min, whereas the clearance from blood to dialysate of dextrans is size-dependent. The fluid removal rate estimated by the difference in bidirectional transport of inulin (1.79 +/- 0.38 ml/min; p < 0.0005) was of the same order of magnitude as has been found using the removal rate of macromolecules from the peritoneal cavity. Also, the role of local accumulation of macromolecules was studied during continuous administration of dextrans. No differences were found in the dextran disappearance rate before and after saturation of the peritoneal interstitium with dextran (1.1 +/- 0.6 vs. 1.0 +/- 0.4 ml/min). During a study using a hypoosmotic solution we calculated a net transcapillary backfiltration of fluid, whereas the dextran removal rate was in the same order of magnitude as found using commercially available dialysate. In our opinion, the disappearance rate of macromolecules is an estimate of convective fluid loss from the peritoneal cavity into the peritoneal lymphatic system.

Initial blood pressure fall on stand up and exercise explained by changes in total peripheral resistance

To elucidate the underlying mechanisms of the initial fall in blood pressure on standing upright from the supine position, we measured the beat-to-beat changes in intra-arterial pressure in eight healthy male subjects in response to standing. Changes in stroke volume, cardiac output, and total peripheral resistance were computed from the pressure waveform using a pulse contour method. To determine possible mechanisms for the changes observed on standing, similar measures were made on passive tilting and a brief (3-s) bout of cycle exercise. Standing elicited a transient 25% (23-mmHg) fall in mean blood pressure as a result of a 36% fall in total peripheral resistance. Head-up tilt elicited a gradual change in haemodynamic parameters, which reached plateau levels in 20-30 s. Cycling elicited a transient 17% (18-mmHg) fall in blood pressure and a 41% fall in total peripheral resistance. In addition, we measured right atrial and esophageal pressures in two subjects on standing and cycling and found a 10- to 15-mmHg rise in right atrial pressure without a corresponding change in esophageal pressure. This points to the cardiopulmonary reflex as the primary effector of peripheral vasodilation, but we cannot exclude the possibility that 1) local metabolic vasodilation and 2) central command-mediated cholinergic vasodilation contributed to the fall in vascular resistance.