Quantification of free water transport in peritoneal dialysis

Quantification of free water transport in peritoneal dialysis.BackgroundIn peritoneal dialysis (PD) total net ultrafiltration (NUF) is dependent on transport through small pores and through water channels in the peritoneum. These channels are impermeable to solutes, and therefore, crystalloid osmotic-induced free water transport occurs through them. Several indirect methods to assess free water transport have been suggested. The difference in NUF between a 3.86% and a 1.36% solution gives a rough indication, but is very time consuming. The magnitude of the dip in dialysate/plasma (D/P) sodium in the initial phase of a 3.86% exchange is another way to estimate free water transport. In the present study, a method was applied to calculate free water transport by calculating sodium-associated water transport in one single 3.86% glucose dwell.MethodsForty PD patients underwent one standard peritoneal permeability analysis (SPA) with a 1.36% glucose solution, and another with a 3.86% glucose solution. At different time points intraperitoneal volume and sodium concentration were assessed. This made it possible to calculate total sodium transport. By subtracting this transport (which must have occurred through the small pores) from the total fluid transport, free water transport remained. These results were compared with the other methods to estimate free water transport.ResultsFor the 1.36% glucose dwell, total transcapillary ultrafiltration in the first hour (TCUF0-60) was 164 mL, transport through the small pores was 129 mL, and free water transport was 35 mL (21%). For the 3.86% glucose solution, total TCUF0-60 was 404 mL, transport through the small pores was 269 mL, and free water transport was 135 mL (34%). The contribution of free water transport in the first minute (TCUF0-1) was 39% of the total fluid transport. From the 40 patients, 11 patients had ultrafiltration failure (NUF <400 mL after 4 hours). For these patients the contribution of free water to TCUF0-1 was significantly lower than for those with normal ultrafiltration (20% vs. 48%, P < 0.05). A strong correlation was present between free water transport as a percentage of total fluid transport and the maximum dip in D/P sodium (r = 0.84). The correlation was not significant with the difference in net ultrafiltration of 3.86% and 1.36% solutions (r = 0.24, P = 0.3).ConclusionThe method applied here is the first direct quantification of free water transport, calculated from a single standard peritoneal function test. It offers a quick possibility to evaluate patients suffering from ultrafiltration failure. In these patients free water transport was impaired, but the origin of this impairment is still to be determined

Augmenting solute clearance in peritoneal dialysis

Augmenting solute clearance in peritoneal dialysis.BackgroundThe removal of low molecular weight solutes by peritoneal dialysis is less than by hemodialysis. The targets for Kt/Vurea and creatinine clearance formulated in the Dialysis Outcome Quality Initiative are unlikely to be achieved in a substantial portion of peritoneal dialysis patients. Possibilities to increase small solute clearances have therefore been subject to many investigations.MethodsA review of the literature and of recent new data on determinants of solute removal, such as residual renal function, the role of drained dialysate volume and manipulation of the diffusive capacity of the peritoneum are presented.ResultsThe contribution of residual GFR is more important for the clearance of creatinine than for Kt/Vurea. It is even more important for the removal of organic acids that are removed from the body by tubular secretion. High dosages of furosemide increase the urinary volume and the fractional Na+ excretion, but have no effect on the magnitude of residual GFR, renal creatinine clearance, renal urea clearance, and peritoneal transport characteristics. The drained dialysate volume per day is the main determinant of the peritoneal removal of urea. Its effect decreases the higher the molecular weight of a solute. It can be augmented by using large instillation volumes, by the application of more exchanges, and by increasing peritoneal ultrafiltration. A large exchange volume is especially effective in patients with an average transport state, but in those with high solute transport rates, Kt/Vurea is especially influenced by the number of exchanges. Possibilities to increase ultrafiltration are discussed. The diffusive capacity of the peritoneum can be augmented by using low dosages of intraperitoneally administered nitroprusside. This increases solute transport most markedly when it is applied in combination with icodextrin as osmotic agent.ConclusionsSmall solutes clearances cannot be increased by furosemide. Increasing the instilled volume of dialysis fluid and the number of exchanges both affect solute clearance. Studies are necessary on long-term effects of manipulation of the peritoneal membrane with nitroprusside

Local Anaesthesia Suppressing Idiopathic Ventricular Tachycardia - A Cause of Non-inducible Arrhythmia During Electrophysiology Study

AbstractA 13year old boy having idiopathic ventricular tachycardia had non-inducible tachycardia twice on electrophysiology (EP) study due to suppression of arrhythmia by local anaesthetic agent, lignocaine. This case report demonstrates a cause of non-inducibility or arrhythmia during EP study and effect of lignocaine in suppression of idiopathic ventricular tachycardia

Peritoneal Dialysis in Western Countries

Peritoneal dialysis (PD) for the treatment of end-stage renal failure was introduced in the 1960s. Nowadays it has evolved to an established therapy that is complementary to hemodialysis (HD), representing 11% of all patients treated worldwide with dialysis. Despite good clinical outcomes and similar results in patient survival between PD and HD, the penetration of PD is decreasing in the Western world. First the major events in the history of the development of PD are described. Then important insights into the physiology of peritoneal transport are discussed and linked to the changes in time observed in biopsies of the peritoneal membrane. Furthermore, the developments in peritoneal access, more biocompatible dialysate solutions, automated PD at home, the establishment of parameters for dialysis adequacy and strategies to prevent infectious complications are mentioned. Finally non-medical issues responsible for the declining penetration in the Western world are analyzed. Only after introduction of the concept of continuous ambulatory PD by Moncrief and Popovich has this treatment evolved in time to a renal replacement therapy. Of all structures present in the peritoneal membrane, the capillary endothelium offers the rate-limiting hindrance for solute and water transport for the diffusive and convective transport of solutes and osmosis. The functional and anatomical changes in the peritoneal membrane in time can be monitored by the peritoneal equilibrium test. Peritonitis incidence decreased by introduction of the Y-set and prophylaxis using mupirocin on the exit site. The decrease in the proportion of patients treated with PD in the Western world can be explained by non-medical issues such as inadequate predialysis patient education, physician experience and training, ease of HD initiation, overcapacity of in-center HD, lack of adequate infrastructure for PD treatment, costs and reimbursement issues of the treatment. (1) PD is cheaper than HD and provides a better quality of life worldwide, but its prevalence is significantly lower than that of HD in all countries, with the exception of Hong Kong. Allowing reimbursement of PD but not HD has permitted to increase the use of PD over HD in many Asian countries like Hong Kong, Vietnam, Taiwan, Thailand, as well as in New Zealand and Australia over the last years. In the Western world, however, HD is still promoted, and the proportion of patients treated with PD decreases. Japan remains an exception in Asia where PD penetration is very low. Lack of adequate education of practitioners and information of patients might as well be reasons for the low penetration of PD in both the East and West. (2) Patient survival of PD varies between and within countries but is globally similar to HD. (3) Peritonitis remains the main cause of morbidity in PD patients. South Asian countries face specific issues such as high tuberculosis and mycobacterial infections, which are rare in developed Asian and Western countries. The infection rate is affected by climatic and socio-economic factors and is higher in hot, humid and rural areas. (4) Nevertheless, the promotion of a PD-first policy might be beneficial particularly for remote populations in emerging countries where the end-stage renal disease rate is increasing dramaticall

Peritoneal changes in patients on long-term peritoneal dialysis

Long-term peritoneal dialysis can lead to morphological and functional changes in the peritoneum. Although the range of morphological alterations is known for the peritoneal dialysis population as a whole, these changes will not occur in every patient in the same sequence and to the same extent. Longitudinal studies are therefore required to help identify which patients might develop the changes. Although longitudinal studies using peritoneal biopsies are not possible, analyses of peritoneal effluent biomarkers that represent morphological alterations could provide insight. Longitudinal studies on peritoneal transport have been performed, but follow-up has often been too short and an insufficient number of parameters have been investigated. This Review will firstly describe peritoneal morphology and structure and will then focus on peritoneal effluent biomarkers and their changes over time. Net ultrafiltration will also be discussed together with the transport of small solutes. Data on the peritoneal transport of serum proteins show that serum protein levels do not increase to the same extent as levels of small solutes with long-term peritoneal dialysis. Early alterations in peritoneal transport must be distinguished from alterations that only develop with long-term peritoneal dialysis. Early alterations are related to vasoactive mediators, whereas later alterations are related to neoangiogenesis and fibrosis. Modern peritoneal dialysis should focus on the early detection of long-term membrane alterations by biomarkers--such as cancer antigen 125, interleukin-6 and plasminogen activator inhibitor 1--and the improved assessment of peritoneal transpor

The Natural Time Course of Membrane Alterations During Peritoneal Dialysis Is Partly Altered by Peritonitis

♦ The quality of the peritoneal membrane can deteriorate over time. Exposure to glucose-based dialysis solutions is the most likely culprit. Because peritonitis is a common complication of peritoneal dialysis (PD), distinguishing between the effect of glucose exposure and a possible additive effect of peritonitis is difficult. The aim of the present study was to compare the time-course of peritoneal transport characteristics in patients without a single episode of peritonitis-representing the natural course-and in patients who experienced 1 or more episodes of peritonitis during long-term follow-up. ♦ This prospective, single-center cohort study enrolled incident adult PD patients who started PD during 1990-2010. A standard peritoneal permeability analysis was performed in the first year of PD treatment and was repeated every year. The results in patients without a single episode of peritonitis ("no-peritonitis group") were compared with the results obtained in patients who experienced 1 or more peritonitis episodes ("peritonitis group") during a follow-up of 4 years. ♦ The 124 patients analyzed included 54 in the no-peritonitis group and 70 in the peritonitis group. The time-course of small-solute transport was different in the groups, with the peritonitis group showing an earlier and more pronounced increase in the mass transfer area coefficient for creatinine (p = 0.07) and in glucose absorption (p = 0.048). In the no-peritonitis group, the net ultrafiltration rate (NUFR) and the transcapillary ultrafiltration rate (TCUFR) both showed a steep increase from the 1st to the 2nd year of PD that was absent in the peritonitis group. Both groups showed a decrease in the NUFR after year 3. A decrease in the TCUFR occurred only in the peritonitis group. That decrease was already present after the year 1 in patients with severe peritonitis. The time-course of free water transport showed a continuous increase in the patients without peritonitis, but a decrease in the patients who experienced peritonitis (p < 0.01). No difference was observed in the time-course of the effective lymphatic absorption rate. The time-courses of immunoglobulin G and α2-macroglobulin clearances showed a decrease in both patient groups, with a concomitant increase of the restriction coefficient. Those changes were not evidently influenced by peritonitis. The two groups showed a similar decrease in the mesothelial cell mass marker cancer antigen 125 during follow-up. ♦ On top of the natural course of peritoneal function, peritonitis episodes to some extent influence the time-course of small-solute and fluid transport-especially the transport of solute-free water. Those modifications increase the risk for overhydratio

Can Free Water Transport Be Used as a Clinical Parameter for Peritoneal Fibrosis in Long-Term PD Patients?

Sodium sieving in peritoneal dialysis (PD) occurs in a situation with high osmotically-driven ultrafiltration rates. This dilutional phenomenon is caused by free water transport through the water channel aquaporin-1. It has recently been described that encapsulating peritoneal fibrosis is associated with impaired free water transport, despite normal expression of aquaporin-1. In this review, it will be argued that free water transport can be used for assessment of fibrotic peritoneal alterations, due to the water-binding capacity of collagen. Finally, the consequences for clinical practice will be discusse

Peritoneal effluent MMP-2 and PAI-1 in encapsulating peritoneal sclerosis

Recently, the use of effluent matrix metalloproteinase 2 (MMP-2) and plasminogen activator inhibitor 1 (PAI-1) as potential biomarkers of peritoneal fibrosis has been demonstrated during longitudinal follow-up of incident peritoneal dialysis (PD) patients. This study focuses on effluent MMP-2 and PAI-1 as early diagnostic markers in the preceding years of patients who develop encapsulating peritoneal sclerosis (EPS). Diagnostic test study. PD patients who developed EPS were compared with controls using a 1:3 case-control design with a minimum PD duration of 57 months. Dialysate appearance rates of MMP-2 and PAI-1. EPS cases identified by 2 experienced nephrologists and a radiologist based on predefined criteria. 11 patients developed EPS within our center. The time course of MMP-2 appearance rates, studied by means of a linear repeated-measures model 4 years prior to the diagnosis of EPS, showed no difference between long-term controls and patients with EPS. In contrast, higher PAI-1 appearance rates were found in patients with EPS compared with controls (P=0.01). At a lag time of 1 year prior to EPS diagnosis, time-specific receiver operating characteristic curve analyses indicated a discriminative ability for PAI-1 appearance rate of 0.77 (95% CI, 0.63-0.91). A discriminative capacity was absent for those of MMP-2. Low event rate of EPS prevented independent validation in this single-center study. Elevated levels of PAI-1 appearance rates are present in patients who develop EPS, pointing to progressive peritoneal fibrosis and sclerosis. The PAI-1 appearance rate has fair discriminative capacity from 3 years prior to EPS diagnosis. Therefore, effluent PAI-1 may aid in monitoring peritoneal fibrosis and serve as a biomarker for EP