Intra- and post-dialytic platelet activation and PDGF-AB release: cellulose diacetate vs polysulfone membranes

Bedside prediction of intradialytic hemodynamic instability in critically ill patients: the SOCRATE study

BACKGROUND

Despite improvements in intermittent hemodialysis management, intradialytic hemodynamic instability (IHI) remains a common issue that could account for increased mortality and delayed renal recovery. However, predictive factors of IHI remain poorly explored. The objective of this study was to evaluate the relationship between baseline macrohemodynamic, tissue hypoperfusion parameters and IHI occurrence.

METHODS

Prospective observational study conducted in a 18-bed medical ICU of a tertiary teaching hospital. Cardiovascular SOFA score, index capillary refill time (CRT) and lactate level were measured just before (T0) consecutive intermittent hemodialysis sessions performed for AKI. The occurrence of IHI requiring a therapeutic intervention was recorded.

RESULTS

Two hundred eleven sessions, corresponding to 72 (34%) first sessions and 139 (66%) later sessions, were included. As IHI mostly occurred during first sessions (43% vs 12%, P < 0.0001), following analyses were performed on the 72 first sessions. At T0, cardiovascular SOFA score ≥1 (87% vs 51%, P = 0.0021) was more frequent before IHI sessions, as well as index CRT ≥ 3 s (55% vs 15%, P = 0.0004), and hyperlactatemia > 2 mmol/L (68% vs 29%, P = 0.0018). Moreover, the occurrence of IHI increased with the number of macrohemodynamic and tissue perfusion impaired parameters, named SOCRATE score (cardiovascular SOFA, index CRT and lactATE): 10% (95% CI [3%, 30%]), 33% (95% CI [15%, 58%]), 55% (95% CI [35%, 73%]) and 80% (95% CI [55%, 93%]) for 0, 1, 2 and 3 parameters, respectively (AUC = 0.79 [0.69-0.89], P < 0.0001). These results were confirmed by analyzing the 139 later sessions included in the study.

CONCLUSIONS

The SOCRATE score based on 3 easy-to-use bedside parameters correlates with the risk of IHI. By improving risk stratification of IHI, this score could help clinicians to manage intermittent hemodialysis initiation in critically ill AKI patients.

The effect of high-flux hemodialysis and post-dilution hemodiafiltration on platelet closure time in patients with end stage renal disease

INTRODUCTION

We aimed to compare prospectively the effect of high-flux hemodialysis and post-dilution hemodiafiltration on platelets.

METHODS

Twenty-two hemodialysis patients were treated with one high-flux hemodialysis and one post-dilution hemodiafiltration procedure. PFA-100 closure times (collagen/epinephrine-CEPI and collagen/adenosine diphosphate-CADP) were measured before and after the procedure, as well as platelet count, hemoglobin, hematocrit, and red blood cell count. All pre-dialysis and post-dialysis samples were taken from the afferent line.

FINDINGS

The platelet count after vs. before hemodialysis did not change significantly (229.3 ± 55.0 x10⁹ /L vs. 233.6 ± 55.8 × 10⁹ /L; P = 0.269), but was significantly lower after post-dilution hemodiafiltration (215.5 ± 51.7 × 10⁹ /L vs. 245.3 ± 59.9 × 10⁹ /L; P < 0.0001). CEPI after vs. before hemodialysis was not significantly prolonged (192.9 ± 60.8 s vs. 173.4 ± 52.5 s; P = 0.147), and the same applied to CADP (143.6 ± 40.3 s vs. 142.6 ± 38.4 s; P = 0.897). CEPI after vs. before post-dilution hemodiafiltration was significantly prolonged (268.3 ± 41.3 s vs. 176.4 ± 54.0 s; P < 0.0001) as was CADP (221.0 ± 53.9 s vs.133.9 ± 31.1 s; P < 0.0001).

DISCUSSION

Only after post-dilution hemodiafiltration, we found a lower platelet count and prolonged platelet closure times.

Acetylsalicylic acid decreases clotting in combination with enoxaparin during haemodialysis in vitro

BACKGROUND

Anticoagulation is a cornerstone in haemodialysis (HD) therapy to avoid clotting of blood when it comes into contact with the dialysis membrane. Although heparins are usually administered as anticoagulants, they are not always sufficient to maintain adequate HD. We investigated the additional effect of acetylsalicylic acid compared with standard anticoagulation on maintaining adequate flow properties during HD in vitro.

METHODS

We collected blood from 42 healthy volunteers, between 18 and 60 years of age, into bags filled with 1, 1.5 or 2 mg enoxaparin, with (treatment group) or without (control group) 100 mg of aspirin. Blood was evaluated before, during and at the end of each experiment to determine coagulation parameters, whole blood aggregation and thromboelastogram measurements. Transmembrane pressure was recorded as indirect estimate of dialysis patency. The primary endpoint was time to filter clotting.

RESULTS

Addition of acetylsalicylic acid significantly prolonged the time to circuit clotting from 120 (105-150) min to >180 min (120-180) min (P = 0.047) and allowed lowering the enoxaparin concentration from 2 mg per circuit to 1 mg without an increase in clotting. Furthermore, it reduced the transmembrane pressure from 46 to 4 mmHg (P < 0.001) after 4 h of dialysis. Acetylsalicylic acid better preserved the platelet count (128 versus 116 × 10E9/L, P = 0.01) and improved platelet aggregation at the end of the dialysis procedure.

CONCLUSION

Adding acetylsalicylic acid to HD circuits lowered the transmembrane pressure, better preserved platelet function and prolonged the time to circuit clotting, which in sum increases haemodialyser performance and may facilitate a more effective HD.

The mechanisms of sulfated polysaccharide drug of propylene glycol alginate sodium sulfate (PSS) on bleeding side effect

Propylene glycol alginate sodium sulfate (PSS), a sulfated polysaccharide derivative, has been used as a heparinoid drug to prevent and treat hyperlipidemia and ischemic cardio-cerebrovascular diseases in China for 30 years. But its bleeding risk should not be overlooked. Here we clarified the reasons and mechanism leading to bleeding side effect of PSS. It was found that PSS fractions with low mannuronic acid (M)/guluronic acid (G) ratio and high molecular weight (Mw) can excessively extend activated partial thromboplastin time (APTT) and thrombin time (TT), over-inhibit the thrombin (FIIa) activity mediated by anti-thrombin III (ATIII) to induce bleeding risk. In addition, the fraction of low M/G ratio can suppress platelet aggregation mediated by adenosine diphosphate (ADP) and induce platelet reduction by improving platelet antibody (PA)-IgA/G in serum and by inhibiting or damaging the bone marrow hematopoietic function. And the fraction of high Mw can restrain the reticulated platelet (RP) production, then reduce mean platelet volume (MPV) and platelet-large cell counts or ratio, and finally decrease platelet amount by inhibiting or damaging the bone marrow hematopoietic function. In brief, PSS fractions with low M/G ratio and high Mw were the main reasons to bring about bleeding by excessively suppressing coagulant factors activities and weakening platelet function. Our results suggested that it is very necessary to control the M/G ratio and the range of Mw of PSS to guarantee its safety and effectiveness in clinical.

Hemodialysis access thrombosis

For the over 400,000 patients in the United States dependent on hemodialysis, arteriovenous (AV) access thrombosis may lead to missed dialysis sessions, inpatient admissions and the need for placement of temporary dialysis catheters. It is also the leading cause of permanent access loss. Percutaneous declotting is generally preferred over surgical thrombectomy. Various percutaneous approaches can be employed including the lyse-and-wait technique, thromboaspiration, pulse spray aided pharmacomechanical thrombolysis, and use of mechanical thrombectomy device.

Increased cyclic guanosine monophosphate levels and continuous-flow left-ventricular assist devices: Implications for gastrointestinal bleeding

OBJECTIVES

We examine the hypothesis that cyclic guanosine monophosphate (cGMP) levels are elevated in recipients of continuous-flow left ventricular assist devices (CF-LVADs) and that elevated cGMP levels are associated with a risk of gastrointestinal (GI) bleeding events.

METHODS

The levels of cGMP, nitric oxide, platelet activation markers, platelet-derived growth factors (PDGF) AB/BB and AA, and the inflammatory mediator C-reactive protein (CRP) were examined in 19 CF-LVAD recipients, 21 patients who had heart failure, and 19 healthy control-group participants.

RESULTS

The median level of cGMP was significantly higher in CF-LVAD recipients, compared with healthy participants (6.6 vs 2.1 pmol/mL, u = 62.5; P = .001; r = -0.55). Median cGMP levels in the heart failure group (12.5 pmol/L) were higher, compared with both CF-LVAD recipients (u = 75.0; P = .001; r = -0.53) and healthy participants (u = 4.0; P < .001; r = -0.83). Compared with the healthy group, median CRP levels were significantly higher in CF-LVAD recipients (2.9 vs 8.0 mg/L; u = 58.0; P < .001; r = -0.63) and heart failure patients (2.9 vs 7.0 mg/L; u = 59.0; P < .001; r = -0.65). In the subgroup of patients supported with the HeartMate II (Thoratec Corporation, Pleasanton, Calif), pulsatility index was significantly negatively correlated with cGMP levels (r = -0.73; P < .05), indicating that low pulsatility index is associated with higher cGMP levels. High cGMP levels were significantly associated with GI bleeding events, but not with bleeding events in general.

CONCLUSIONS

The primary finding of this study is that GI bleeding in CF-LVAD recipients is associated with significantly elevated cGMP levels, despite high levels of CRP, which interfere with cGMP production. Further studies are required to determine whether elevated cGMP levels can be used as a clinical marker for increased risk of GI bleeding in CF-LVAD recipients.

Electron microscopic observation in case of platelet activation in a chronic haemodialysis subject

During haemodialysis (HD), platelets (PLTs) are activated and release granule contents. As HD treatment occurs three times a week, it has been demonstrated that PLTs are exhausted due to the repetitive character of the treatment. To identify PLT depletion morphologically, PLT evaluation was performed by light microscopy and electron microscopy (EM) in a chronic HD subject and a healthy reference subject. Blood samples were taken before the start of HD treatment for measurement of PLT count, PLT volume and size parameters. Blood smears were screened by light microscopy for qualitative evaluation of PLT granule containing cytoplasm, as indicated by its staining density. Morphological PLT parameters of surface area and size of dense bodies were assessed by EM. Data were compared with results of a group of 20 chronic HD subjects and a group of 20 healthy reference subjects. With respect to the percentage of PLTs with appropriate staining density (>75%), light microscopic evaluation showed that this value (9%) was within the range of a group of chronic HD subjects, but considerably below the reference range (70%). EM evaluation revealed an average PLT surface area and dense bodies area of respectively 42% and 31%, if the healthy reference subject was set on 100%. PLTs from a chronic HD subject are considerably smaller and substantially less granular than PLTs from a healthy reference subject. These findings support the hypothesis of PLT depletion in chronic HD subjects due to frequent PLT activation and/or increased urea concentrations.

Different effects of enoxaparin, nadroparin, and dalteparin on plasma TFPI during hemodialysis: a prospective crossover randomized study

BACKGROUND

Low-molecular-weight heparins (LMWHs) are an alternative to unfractionated heparin (UFH) for anticoagulation during hemodialysis (HD). We performed a prospective randomized crossover study of the effect of enoxaparin, nadroparin, and dalteparin on some hemostatic factors, including tissue factor pathway inhibitor (TFPI), in patients with maintenance HD.

METHODS

Plasma levels (immunoassays) of total TFPI, platelet-derived growth factor-AB (PDGF-AB), and prothrombin fragment 1 + 2 (PF 1 + 2) were evaluated pre-HD, after 10 (T10) and 180 (T180) minutes of HD in 21 patients, who completed a 3-period (for 2 months each) crossover study in 6 groups (Latin-square design).

RESULTS

The baseline TFPI, PDGF-AB, and PF 1 + 2 levels were comparable under all LMWH treatments. Tissue factor pathway inhibitor levels, compared with the baseline, significantly increased (all P < 10(-4)), whereas PDGF-AB levels remained stable at each interval during enoxaparin, nadroparin, and dalteparin anticoagulated HD. Interestingly, TFPI increment at T10 was the highest, dose-dependent, and accompanied by PF 1 + 2 decrease under enoxaparin administration.

CONCLUSION

The switch from enoxaparin to nadroparin and dalteparin used as anticoagulants had no long-term effect on the baseline total TFPI and PF 1 + 2 levels in chronically HD patients. Only short-term, overdialytic differences were noticed, indicating a single bolus of enoxaparin (0.75 mg/kg) as the most potent stimulus for endothelial TFPI.

Intradialytic and postdialytic platelet activation, increased platelet phosphatidylserine exposure and ultrastructural changes in platelets in children with chronic uremia

The present research evaluated the intradialytic and postdialytic changes in platelet factor-4 and beta-thromboglobulin plasma levels by enzyme-linked immunoadsorbent assay method and platelet aggregation by ADP as well as flow cytometric percentage of annexin-V-positive platelets as a measure of phosphatidylserine externalization and ultrastructural examination of platelets in 37 uremic patients on regular hemodialysis and 25 age-matched and sex-matched controls. Platelet factor-4 plasma levels increased, remain consistently high during hemodialysis session (20.24 +/- 3.05 IU/ml after 30 min, P < 0.001 and 23.67 +/- 3.68 IU/ml after 240 min, P < 0.001) and returned to control values (6.10 +/- 1.54 IU/ml) only after 24 h following the end of the session. beta-Thromboglobulin showed a trend similar to that of platelet factor-4. Platelet aggregation by ADP showed reduced function in comparison with controls (69.32 +/- 12.37 versus 91.95 +/- 1.59%, P < 0.001). Flow cytometric percentage of annexin-V-positive platelet was significantly elevated (P < 0.001) in uremic patients when compared with normal controls. Ultrastructural studies of platelets 30 min after starting of dialysis showed degranulation of its granules and at 240 min showed complete degranulation, whereas in the postdialytic phase (12 h after the end of dialysis) refilled alpha-granules started to appear. Positive correlations were found between platelet concentration and platelet factor-4 and beta-thromboglobulin plasma levels during and after dialysis (P < 0.001) and with annexin-V-positive platelets percentage (P < 0.001). In conclusion, activated platelets were found in chronic hemodialysis patients, a finding that may explain why uremic patients often suffer from thrombotic accidents. The platelet activation is associated with exposure of phosphatidylserine on the platelet exterior. Platelet factor-4 and beta-thromboglobulin are released from platelets as a result of a defect in their granules membrane as shown by the electron microscopy, mainly as a consequence of the blood-membrane contact during dialysis, and they return only slowly to control values.

Changes in platelet volume, morphology and RNA content in subjects treated with haemodialysis

During haemodialysis treatment, blood flows from the body to the extracorporeal circuit and vice versa. In this study, pathophysiological defects in platelets indicated by alterations in RNA content and aberrations in platelet volume and morphology are detected before and during haemodialysis treatment. In subjects receiving haemodialysis treatment, qualitative interpretation of platelet characteristics with application of light microscopic evaluation reveals only 19+/-11 % of platelets with appropriate staining density of the granule-containing cytoplasm. On the contrary, a reference group of apparently healthy subjects shows 70+/-12 % platelets with appropriate staining density of the granule-containing cytoplasm. During haemodialysis treatment, mean values for platelet volume, platelet distribution width and platelet large cell ratio demonstrate a tendency to decrease by 10 %, 11 % and 6 %, respectively, from the mean initial value to the value at t = 150 min. Reduction of the platelet volume parameters just mentioned is hypothesized to be due to platelet degranulation as a result of platelet activation.

Platelet activation in clinical haemodialysis: LMWH as a major contributor to bio-incompatibility?

BACKGROUND

The sum of undesirable side effects, occurring during haemodialysis (HD), is called bio-incompatibility. Concerning platelets, both an increase in the expression of the cell surface marker P-selectin (CD62p) and release of the intracellular granule product platelet factor 4 (PF4) have been described. However, as PF4 is also abundantly present on endothelium-bound proteoglycans, it is questionable whether the HD-induced increase is exclusively attributable to release from platelets. With respect to the cause of HD-induced bio-incompatibility, interest has been focused mainly on the extracorporeal circuit (ECC), especially the dialyser, whereas only little attention has been paid to other parts of the ECC and the mode of anticoagulation applied. To address the cause and origin of platelet activation and PF4 release during clinical HD, two complementary clinical studies were performed.

MATERIALS AND METHODS

In study I, the relative influence of the various parts of the ECC was evaluated by measuring the expression of CD62p, platelet aggregation and levels of PF4 and serotonin at various sampling points. In study II, low-molecular-weight heparin (LMWH) was administered 10 min before the actual start of HD, in order to separate the effects from LMWH and the ECC on platelet activation.

RESULTS

In study I, CD62p expression increased across the entire length of the ECC, including the roller pump and dialyser (median at t(5) from 26% to 43%, P = 0.008; median at t(30) from 28% to 48%, P = 0.007). Increments in PF4 and aggregation of platelets were relatively modest. Platelet serotonin content, which was below reference values in healthy controls, and plasma serotonin concentration, which was above reference values, did not change. In study II, PF4 levels increased markedly after the injection of LMWH (from 12 IU/ml at t(-10) to 75 IU/ml at t(0), P = 0.018), whereas CD62p expression remained stable until the start of HD.

CONCLUSIONS

Platelet activation, as measured by the up-regulation of CD62p, is an early process, occurring not only within the dialyser, but across the entire length of the ECC. As CD62p remained unaltered after the administration of LMWH 10 min before the actual start of HD, this kind of activation is independent of LMWH. Considering PF4 however, a sharp increment was observed after the administration of LMWH and before the start of HD. This finding suggests that the PF4 release observed early in clinical HD is largely independent from the ECC, and is probably the result of LMWH-induced detachment from the endothelium. As the platelet serotonin content was relatively reduced and the plasma serotonin levels were elevated, platelets from chronic HD patients might be depleted due to chronic repetitive activation. Based on these data, it appears first, that PF4 is an inferior marker of platelet activation in clinical HD and second, that LMWH is a major contributor to HD-induced bio-incompatibility.

Differential effects of dialysis and ultrafiltrate from individuals with CKD, with or without diabetes, on platelet phosphatidylserine externalization

Individuals with chronic kidney disease (CKD) and/or diabetes mellitus (DM) are at increased risk of cardiovascular events and have elevated externalization of phosphatidylserine (PS; which propagates thrombus formation) in a small subpopulation of platelets. The purpose of this study was to examine the effect of 1) removing uremic toxins by hemodialysis on PS externalization in patients with either CKD or CKD and DM and 2) ultrafiltrate (UF) from these individuals on PS externalization in healthy platelets. PS externalization was quantified by a fluorescence-activated cell sorter using annexin V in platelet-rich plasma. PS externalization was elevated threefold in CKD patients and returned to basal values during 3-h hemodialysis. In contrast, it was elevated fivefold in individuals with CKD and DM and was still threefold above control after 3-h treatment. UF significantly increased PS externalization in a small subpopulation of platelets from healthy controls. The effect of UF from individuals with CKD and DM was significantly greater than that from patients with CKD alone, and the responses were partially inhibited by the protein kinase Cδ (PKCδ) inhibitor rottlerin and the 5-hydroxytryptamine (5-HT)2A/2Creceptor antagonist ritanserin. The data suggest that uremic toxins present in UF mediate PS externalization in a small subpopulation of platelets, at least in part, via the 5-HT2A/2Creceptor and PKCδ and demonstrate that DM further enhances platelet PS externalization in CKD patients undergoing hemodialysis. This may explain, at least in part, the additional increase in vascular damage observed in CKD patients when DM is present.

The influence of the haemodialysis procedure on platelets, coagulation and fibrinolysis

In end-stage renal disease, in particularly when treated with haemodialysis, the function of platelets, coagulation and fibrinolytic systems can be disturbed, thus contributing to either thrombotic or bleeding complications. It is important to know whether the currently used haemodialysis procedure itself (by biocompatible membranes and better anticoagulation with nandroparin) affects platelets, coagulation or fibrinolysis. In 15 patients who had been treated with chronic haemodialysis, we measured and compared platelet aggregation (induced by adenosine diphosphate, collagen and epinephrine), the markers of coagulation and fibrinolysis activation (thrombin-antithrombin complexes, thrombin fragments F1+2, D-dimer), and fibrinolytic parameters, i.e. fibrinogen, plasminogen, tissue plasminogen activator (t-PA) and plasminogen activator inhibitor 1 antigen and activity, before and immediately after the regular haemodialysis sessions. We did not find differences between pre- and post-haemodialysis platelet aggregation induced with all agents. Markers of coagulation and fibrinolysis activation remained unchanged during the process of haemodialysis. However, in post-haemodialysis samples, t-PA activity was significantly increased. Other fibrinolytic parameters remained unchanged. In conclusion, our results showed that the current technique of haemodialysis procedure does not affect platelet aggregation or activate coagulation, and therefore, does not contribute to a thrombotic tendency. However, it does directly affect fibrinolysis through activation of t-PA, which might be clinically relevant since this could increase the bleeding tendency in some haemodialysis patients.

Citrate anticoagulation abolishes degranulation of polymorphonuclear cells and platelets and reduces oxidative stress during haemodialysis

BACKGROUND

During haemodialysis (HD), polymorphonuclear cells (PMNs) and platelets are activated and release various granule products, including myeloperoxidase (MPO) and platelet factor 4 (PF4). MPO triggers the generation of reactive oxygen species, leading to irreversible protein, carbohydrate and lipid modification. PF4 probably also contributes to oxidative stress. As previously shown, HD-induced PMN degranulation is almost completely abolished during citrate anticoagulation, most probably due to its calcium chelation ability.

METHODS

In the present study, apart from HD-induced PMN and platelet degranulation, oxidative stress was analysed during three modes of anticoagulation. Heparin, dalteparin and citrate (HDhep, HDdal and HDcit) were compared in a randomized, crossover fashion in eight chronic HD patients. Multiple blood samples were taken during the third HD session of each modality, from both the afferent and efferent line. Besides the degranulation markers MPO and PF4, various markers of oxidative stress were measured, including oxidized low-density lipoprotein (ox-LDL), malondialdehyde (MDA) and carboxymethyllysine (CML).

RESULTS

During HDhep and HDdal, marked degranulation was observed shortly after the start of HD. In contrast, during HDcit, PF4 and MPO levels remained unaltered, suggesting no release at all. After 1 week of HDcit, ox-LDL levels were markedly reduced [median 26% (3-65%), P=0.01], if compared with HDhep and HDdal. As regards MDA and CML, no differences were found.

CONCLUSIONS

This study shows first, that HD-induced PMN and platelet degranulation are early, most probably calcium-dependent processes and, secondly, that the formation of ox-LDL is clearly dependent on the type of anticoagulant applied.

Comparison of continuous and intermittent renal replacement therapy for acute renal failure

BACKGROUND

Mortality rates of critically ill patients with acute renal failure (ARF) requiring renal replacement therapy (RRT) are high. Intermittent and continuous RRT are available for these patients on the intensive care units (ICUs). It is unknown which technique is superior with respect to patient outcome.

METHODS

We randomized 125 patients to treatment with either continuous venovenous haemodiafiltration (CVVHDF) or intermittent haemodialysis (IHD) from a total of 191 patients with ARF in a tertiary-care university hospital ICU. The primary end-point was ICU and in-hospital mortality, while recovery of renal function and hospital length of stay were secondary end-points.

RESULTS

During 30 months, no patient escaped randomization for medical reasons. Sixty-six patients were not randomized for non-medical reasons. Of the 125 randomized patients, 70 were treated with CVVHDF and 55 with IHD. The two groups were comparable at the start of RRT with respect to age (62+/-15 vs 62+/-15 years, CVVHDF vs IHD), gender (66 vs 73% male sex), number of failed organ systems (2.4+/-1.5 vs 2.5+/-1.6), Simplified Acute Physiology Scores (57+/-17 vs 58+/-23), septicaemia (43 vs 51%), shock (59 vs 58%) or previous surgery (53 vs 45%). Mortality rates in the hospital (47 vs 51%, CVVHDF vs IHD, P = 0.72) or in the ICU (34 vs 38%, P = 0.71) were independent of the technique of RRT applied. Hospital length of stay in the survivors was comparable in patients on CVVHDF [median (range) 20 (6-71) days, n = 36] and in those on IHD [30 (2-89) days, n = 27, P = 0.25]. The duration of RRT required was the same in both groups.

CONCLUSION

The present investigation provides no evidence for a survival benefit of continuous vs intermittent RRT in ICU patients with ARF.

Platelet surface receptor activation in patients with chronic renal failure on hemodialysis, peritoneal dialysis and those with successful kidney transplantation

Hemostatic disorders associated with chronic renal failure (CRF) include hemorrhagic and/or thrombotic manifestations, which were ascribed, in part, to uremic platelet dysfunction including abnormalities of expression of platelet glycoprotein receptors. There is, however, still no general agreement on the exact characterization of these platelet abnormalities. This study aims at characterizing the platelet glycoprotein abnormalities associated with CRF, by recording the effect of the three renal replacement therapies, hemodialysis (HD), chronic ambulatory peritoneal dialysis (CAPD), and renal transplantation, on these receptors. The study, which was mainly cross-sectional, included two groups: (i) Patient groups (n = 50): HD patients (n = 20), CAPD patients (n = 10) and successful renal transplant patients (n = 20); (ii) Healthy Controls (n = 34): 23 were men and 11 were women who were age- and sex-matched with the patients. Flow cytometric quantitation of CD41, CD42a, CD42b and CD61 was carried out using a Becton-Dickinson FACScan. The expression of CD41 levels showed a highly significant increase in HD and CAPD patients when compared with the normal control levels. However, levels in transplant patients were comparable to the normal control levels. On the other hand, the expression of CD42a, CD42b, and CD61 showed no significant change in HD and CAPD patients when compared with normal control levels, but there was a significant decrease in transplant patients when compared to the normal control levels. In conclusion, there was evidence of increased expression of one glycoprotein receptor (GpIIb-IIIa) pre-dialysis whether HD or CAPD. In transplant patients, no evidence of platelet activation could be demonstrated.

Plateletpheresis does not cause long-standing platelet-derived growth factor release into the donor blood

BACKGROUND

Recently, long-standing elevations of soluble growth factors released from platelets (PLTs) after contact with artificial surfaces during dialysis were described. They could be jointly responsible for the high frequency of death from cardiovascular diseases in dialysis patients. There are no comparable data on the extent and the duration of a growth factor release by plateletpheresis procedures.

STUDY DESIGN AND METHODS

A total of 37 plateletpheresis procedures were performed with two different devices. PLT-derived growth factor (PDGF) isoform AB, transforming growth factor (TGF)-beta1, and beta-thromboglobulin (beta-TG) were measured in the donors' plasma samples, and PLT activation and function were measured by cytometry and aggregometry before and after plateletpheresis and 1 and 24 hours later.

RESULTS

Before apheresis, the following mean plasma levels were found: beta-TG, 98.6 +/- 37.3 IU per mL; PDGF-AB, 71.5 +/- 38.5 pg per mL; and TGF-beta1, 2.24 +/- 0.80 ng per mL. At the end of the apheresis procedures, the mean PDGF-AB level had increased by a factor of 1.8 (p < 0.05). One hour later, the mean PDGF-AB level had normalized again. No significant change in the levels of beta-TG and TGF-beta1 was found by the apheresis procedures. There was no influence of the blood cell separator type on the results.

CONCLUSION

Only a slight and rapidly reversible increase in soluble PDGF-AB was found during plateletpheresis and no increase in soluble TGF-beta1 and beta-TG was found. This change should not be harmful to the donor.

Platelet activation and PDGF-AB release during dialysis

During hemodialysis the blood-membrane contact causes a release of platelet granule content, which contains Platelet Derived Growth Factor (PDGF-AB). In view of its possible role in accelerated atherosclerotic processes, we evaluated the intra- and post-dialytic changes in PDGF-AB serum levels during hemodialysis sessions performed with Hemophan and Polysulfone membranes. PDGF-AB, PF4, betaTG and MPV levels were determined in the peripheral blood in 30 patients each of whom underwent 6 dialysis sessions: 3 with Hemophan (HE) membrane and 3 with Polysulfone (PS) membrane, interpolated by a wash out session with PS membrane. Blood samples were taken at times 0', 30', 120', 180', 240' during dialysis sessions and at 1, 4 and 20 hours after the end of the session. Statistical analysis was done using the ANOVA one way test and Student's t test PDGF-AB serum levels initially increased and, except for a sharp fall at 120', remained constantly high during HD with both membranes tested, not returning to basal values until 20 hours after the end of the session. PF4, betaTG and MPV all showed a similar trend to PDGF. No statistically significant difference was found between the two membranes tested. PDGF-AB, a powerful growth factor in cells of mesenchymal origin, is released during dialysis mainly as a result of the blood-membrane contact. This we found regardless of the type of dialyzer we tested, and, above all, proved to return very slowly to basal values. We speculate that the release of PDGF-AB could play a part like other atherosclerosis risk-factors in the appearance and worsening of atherosclerotic lesions in hemodialysis patients.

Low TGF-beta1 serum levels are a risk factor for atherosclerosis disease in ESRD patients

BACKGROUND

It is thought that transforming growth factor-beta1 (TGF-beta1) might be a key inhibitor of atherogenesis in non-uremic patients. We evaluated the intra- and post-dialytic serum levels of TGF-beta1 in uremic patients to assess if TGF-beta1 is an independent risk factor for cardiovascular diseases, and if any correlation exists between TGF-beta1 and any yet known atherosclerotic risk factors.

METHODS

We studied 155 patients who were on regular hemodialysis, with or without clinically significant atherosclerotic vascular disease. Forty-one apparently healthy people were enrolled as a control group. TGF-beta1 was evaluated during the midweek dialysis session, at times 0, 30, and 120 minues, at the end of the session, and 3 hours after the session's end. All hitherto known atherosclerotic risk factors also were evaluated. The investigation was performed over a 24-month follow-up.

RESULTS

TGF-beta1 values (mean +/- SD) in dialysis patients were 26.64 +/- 7.0 ng/mL (N=155) compared with 42.31 +/- 6.0 ng/mL in the control group (N=41, P < 0.0001). A weak inverse correlation emerged between TGF-beta1 and age (r=-0.28), TGF-beta1 and lipoprotein(a) [Lp(a); r=-0.35], TGF-beta1 and C-reactive protein (CRP; r=-0.27), and TGF-beta1 and plasminogen activator inhibitor-1 (PAI-1; r=-0.41). TGF-beta1 also correlated with albumin (r=0.31). In the coronary heart disease (CHD) group (N=32) the TGF-beta1 was 26.2 +/- 4.9 ng/mL; in the cerebrovascular disease (CVD) group (N=8) it was 26.7 +/- 3.7 ng/mL and in the peripheral vascular disease (PVD) group (N=9) it was 25.4 +/- 1.7 ng/mL. In dialysis patients with no cardiovascular disease (N=80) TGF-beta1 was 35.1 +/- 6.8 ng/mL (P < 0.0001 vs. CHD, CVD and PVD patients). TGF-beta1 was significantly lower among those patients with triple coronary vessel disease than with the other CHD patients. The Cox analysis demonstrated that a 1 ng/mL reduction in TGF-beta1 concentration was associated with a 9% increase in the relative risk of a cardiovascular event.

CONCLUSIONS

TGF-beta1 was significantly reduced in hemodialysis patients, in particular in those with severe cardiovascular disease. Baseline TGF-beta1, diabetes mellitus and serum albumin levels proved to be the only independent contributors to atherosclerotic risk in dialysis patients.