Effects of iron supplementation on microcytic and hypochromic red blood cells during the third trimester of pregnancy.

INTRODUCTION: Mild anaemia often occurs in the third trimester of pregnancy. Particularly in the Hb range between 101-110 g/L it is difficult to determine whether the decreased haemoglobin concentration is physiological or pathological and whether supplementation is required. The aim of this study was to gain insight into the added value of measuring the percentages of microcytic RBCs (%MicroR) and hypochromic RBCs (%Hypo-He) for monitoring effects of iron supplementation in case of suspected iron-deficient erythropoiesis (IDE) in the third trimester of pregnancy. METHODS: After assessing haematological parameters and zinc protoporphyrin/heme ratio as marker for IDE, subjects were classified into a group with symptoms of IDE (n = 39) or without IDE (n = 106). The subjects with IDE (n = 39) were treated with iron supplementation. After 4 weeks effects of treatment were evaluated. RESULTS: In the group of pregnant women with IDE results of %MicroR and %Hypo-He were increased (p = <.001), compared to the group without haematological symptoms of IDE, whereas RET-He, RBC-He and delta-He were decreased (p = <.001). A significant positive correlation to increased values of %MicroR (r = .75, p = <.001) and %Hypo-He (r = .77, p = <.001) with ZPP was established. However, in the ZPP interval 75-100 µmol/mol heme a slight overlap was demonstrated between subjects with and without symptoms of IDE. After iron supplementation, %Hypo-He decreased (p = .002) while %MicroR remained stable. RET-He, delta-He and RDW-SD increased (p = <.001). CONCLUSION: The added value of %MicroR and %Hypo-He as a single marker for IDE is poor. However, combined interpretation of %MicroR, %Hypo-He, Ret-He and delta-He has added value in monitoring erythropoiesis during pregnancy.

Effects of a Carbohydrate-, Glutamine-, and Antioxidant-Enriched Oral Nutrition Supplement on Major Surgery-Induced Insulin Resistance: A Randomized Pilot Study.

BACKGROUND: Insulin resistance after surgery hampers recovery. Oxidative stress is shown to be involved in the occurrence of postoperative insulin resistance. Preoperative carbohydrate-rich oral nutrition supplements reduce but do not prevent insulin resistance. The aim of the present study was to investigate the effect of a carbohydrate-, glutamine-, and antioxidant-enriched preoperative oral nutrition supplement on postoperative insulin resistance. METHODS: A double-blind randomized controlled pilot study in 18 patients with rectal cancer, who received either the supplement (S) or the placebo (P) 15, 11, and 4 hours preoperatively, was conducted. Insulin sensitivity was studied prior to surgery and on the first postoperative day using a hyperinsulinemic euglycemic 2-step clamp. RESULTS: Hepatic insulin sensitivity (insulin-mediated suppression of glucose production) decreased significantly after surgery in both groups, with no differences between the groups. Peripheral insulin sensitivity (glucose rate of disappearance, Rd) was significantly decreased after surgery in both groups (S: 37.2 [19.1-50.9] vs 20.6 [13.9-27.9]; P: 23.8 [15.7-35.5] vs 15.3 [12.6-19.1] µmol/kg·min) but less pronounced in the supplemented group (P = .04). The percentage decrease in glucose Rd did not differ between the groups. Adipose tissue insulin sensitivity (insulin-mediated suppression of plasma free fatty acids) decreased to the same extent after surgery in both groups. CONCLUSION: Rectal cancer surgery induced profound insulin resistance, affecting glucose and fatty acid metabolism. The preoperative nutrition supplement somewhat attenuated but did not prevent postoperative peripheral insulin resistance.

Blood eosinophilia as a marker of early and late treatment failure in severe acute exacerbations of COPD.

BACKGROUND: Blood eosinophilia is frequently encountered in patients with AECOPD. However the impact of blood eosinophilia at admission in patients with AECOPD on outcome on the short and long term has not been extensively studied which was the objective of the present study. METHODS: We used data of 207 exacerbations from a randomized clinical trial on antibiotic prescription based upon CRP-levels versus GOLD guided strategy and analyzed the impact of blood eosinophils (≥2% of total white cell count and eosinophil count ≥300 cell/microliter) on clinical outcome. RESULTS: 207 patients were included of whom 39 (18·8%) had eosinophilia ≥2%, 23 patients (11.1%) had blood eosinophil ≥300 cell/microliter. Eosinophilia was associated with shorter median length of stay in the eosinophilic groups(≥2% and ≥300 cell/microliter) compared to the non-eosinophilic groups. Early treatment failure was reduced in the both the eosinophilic groups (≥2% and ≥300 cell/microliter). Late treatment failure (day 11-30) did not differ between the groups. Relapse, was more frequent the eosinophilic groups (≥2% and ≥300 cell/microliter), however in the latter group this did not reach statistical significance. Eosinophilia ≥2% was a risk factor for having relapse (eosinophilia ≥2%: HR = 2·351; 95%CI 1·335-4·139), whereas eosinophilia <2% was associated with a lower risk factor for having early treatment failure (HR = 0·339 95%CI 0·122-0·943). CONCLUSION: We showed that blood eosinophilia at admission in patients with an AECOPD is associated with higher short-term treatment success rate. However, blood eosinophilia ≥2% predicts a less favorable outcome due to an increased risk of relapse. CLINICAL TRIAL REGISTRATION: NCT01232140.

Application of Innovative Hemocytometric Parameters and Algorithms for Improvement of Microcytic Anemia Discrimination.

Hemocytometric parameters like red blood cell (RBC) count, mean red blood cell volume (MCV), reticulocyte count, red blood cell distribution width (RDW-SD) and zinc protoporphyrin (ZPP) are frequently established for discrimination between iron-deficiency anemia and thalassemia in subjects with microcytic erythropoiesis. However, no single marker or combination of tests is optimal for discrimination between iron-deficiency anemia and thalassemia. This is the reason why many algorithms have been introduced. However, application of conventional algorithms, only resulted in appropriate classification of 30-40% of subjects. In this mini-review the efficacy of innovative hematological parameters for detection of alterations in RBCs has been considered. It refers to parameters concerning hemoglobinization of RBCs and reticulocytes and the percentages microcytic and hypochromic RBCs, for discrimination between subjects with iron-deficiency anemia (IDA) or thalassemia as well as a combination of both. A new discriminating tool including the above mentioned parameters was developed, based on two precondition steps and discriminating algorithms. The percentage microcytic RBCs is considered in the first precondition step. MCV, RDW-SD and RBC count are applied in the second precondition step. Subsequently, new algorithms, including conventional as well as innovative hematological parameters, were assessed for subgroups with microcytic erythropoiesis. The new algorithms for IDA discrimination yielded results for sensitivity of 79%, specificity of 97%, positive and negative predictive values of 74% and 98% respectively. The algorithms for ß-thalassemia discrimination revealed similar results (74%, 98%, 75% and 99% respectively). We advocate that innovative algorithms, including parameters reflecting hemoglobinization of RBCs and reticulocytes, are integrated in an easily accessible software program linked to the hematology equipment to improve the discrimination between IDA and thalassemia.

Effect of oral taurine on morbidity and mortality in elderly hip fracture patients: a randomized trial.

Hip fracture patients represent a large part of the elderly surgical population and face severe postoperative morbidity and excessive mortality compared to adult surgical hip fracture patients. Low antioxidant status and taurine deficiency is common in the elderly, and may negatively affect postoperative outcome. We hypothesized that taurine, an antioxidant, could improve clinical outcome in the elderly hip fracture patient. A double blind randomized, placebo controlled, clinical trial was conducted on elderly hip fracture patients. Supplementation started after admission and before surgery up to the sixth postoperative day. Markers of oxidative status were measured during hospitalization, and postoperative outcome was monitored for one year after surgery. Taurine supplementation did not improve in-hospital morbidity, medical comorbidities during the first year, or mortality during the first year. Taurine supplementation lowered postoperative oxidative stress, as shown by lower urinary 8-hydroxy-2-deoxyguanosine levels (Generalized estimating equations (GEE) analysis average difference over time; regression coefficient (Beta): -0.54; 95% CI: -1.08--0.01; p = 0.04), blunted plasma malondialdehyde response (Beta: 1.58; 95% CI: 0.00-3.15; p = 0.05) and a trend towards lower lactate to pyruvate ratio (Beta: -1.10; 95% CI: -2.33-0.12; p = 0.08). We concluded that peri-operative taurine supplementation attenuated postoperative oxidative stress in elderly hip fracture patients, but did not improve postoperative morbidity and mortality.

New fluorescent method (PLT-F) on Sysmex XN2000 hematology analyzer achieved higher accuracy in low platelet counting.

OBJECTIVES: In thrombocytopenia, high accuracy and precision of low platelet count is essential for appropriate decisions. The recently introduced Sysmex XN2000 analyzer (Sysmex, Kobe, Japan) offers 3 methods for platelet counting: impedance (PLT-I), optical (PLT-O), and a new fluorescence method (PLT-F). The precision of the PLT-F method in blood samples with platelet counts less than 50 × 10(3)/µL (50 × 10(9)/L) was investigated and compared with the ICSH CD61-ImmunoPLT reference method. For comparison, PLT-I and PLT-O were determined on the Sysmex XN2000 and Sysmex XE2100 analyzer. METHODS: Blood samples with platelet counts less than 50 × 10(3)/µL (50 × 10(9)/L) (n = 37) were analyzed on the Sysmex XN2000 and XE2100 analyzers. The CD61-ImmunoPLT method was performed on a Beckman Coulter FC-500 flow cytometer (Miami, FL). RESULTS: At a platelet count of 20 × 10(3)/µL (20 × 10(9)/L), reproducibility for PLT-I, PLT-O, and PLT-F on the XN2000 demonstrated coefficients of variation of 9.3%, 8.5%, and 3.0%, respectively. Correlation between PLT-O on the XN2000 and XE2100 yielded an r value of more than 0.977. Linear regression analysis between the PLT-F and CD61-ImmunoPLT methods resulted in a PLT-F of 0.71*CD61 - 0.8 (r = 0.988). Linear regression between PLT-F and PLT-O on the XN2000 resulted in a PLT-F of 1.05*PLT-O - 2 (r = 0.975), and using the transfusion threshold of 20 × 10(9)/L platelets resulted in a PLT-F of 0.90*PLT-O - 0.4 (r = 0.956). CONCLUSIONS: The new PLT-F method demonstrated excellent results for reproducibility in samples with platelet counts less than 50 × 10(9)/L. PLT-F could be helpful in making better decisions for platelet transfusions.

Coagulation activation, depletion of platelet granules and endothelial integrity in case of uraemia and haemodialysis treatment.

BACKGROUND: During haemodialysis (HD) treatment, increase of platelet (PLT) activation and induction of procoagulant activity is demonstrated. Although the role of the endothelium and its direct interaction with coagulation and homeostasis is known, it is not elucidated how PLT activation markers and activation of coagulation coincide with markers of endothelial integrity during HD treatment. In the present study uraemia and HD induced changes, with particular emphasis on PLT granules depletion, activation of coagulation and endothelial integrity were investigated. METHODS: To detect depletion of PLT granules, peripheral blood slide smears were screened by light microscopy for qualitative evaluation of PLT granule containing cytoplasm, as indicated by its granules staining density. Activation of coagulation was investigated by establishement of thrombin-antithrombin (TAT) and fibrinogen concentrations. To evaluate endothelial integrity proendothelin (proET-1) plasma concentrations were established. RESULTS: Results of our study demonstrate that proET-1 plasma concentrations were obviously increased in the subjects' group with end-stage chronic kidney disease (CKD) and renal failure if compared with a group of apparently healthy subjects. The amount of depleted PLT granules was obviously increased in the subjects' group with end-stage CKD if compared with the group with renal failure. Mean plasma concentrations of TAT and fibrinogen revealed results within the reference range. CONCLUSIONS: It is demonstrated that uraemia is associated with endothelial damage and aberrations in PLT granules morphology in subjects with HD treatment. We hypothesize that increased proET-1 concentrations reflect ongoing stress on endothelial cells amongst others due to uraemia. Biomarkers like proET-1 and aberrations in PLT granules morphology assist in the early detection of procoagulant activity of the endothelium.

Transient impairment of reticulocyte hemoglobin content and hepcidin-25 induction in patients with community-acquired pneumonia.

INTRODUCTION: Patients with community-acquired pneumonia (CAP) often exhibit a declining hemoglobin (Hb) concentration. During inflammation pro-inflammatory cytokines and cells of the reticuloendothelial system induce disturbances in iron homeostasis. In this study inflammation markers and hepcidin-25 concentrations were monitored together with short-term alterations in reticulocyte hemoglobinization (RET-He). METHODS: A total of 25 patients with CAP participated in the study. The assay for serum hepcidin-25 is based on a combination of weak cation exchange chromatography and time-of-flight mass spectrometry. RESULTS: At hospital admission serum hepcidin-25 concentrations (14.6 ± 6.9 nMol/L, mean ± SD) were established in the upper level of the reference range (0.5-13.9 nMol/L). Results for C-reactive protein (CRP) and Interleukin-6 (IL-6) were obviously increased compared to the reference ranges. From admission until day 14 hepcidin-25, CRP and IL-6 steadily decreased towards the reference ranges. Hb concentrations declined from admission until day 4 from 8.1 ± 1.0 mMol/L to 7.4 ± 0.9 mMol/L. At admission Ret-He results were within the lower region of the reference range (1900-2300aMol) and results demonstrated a decline during admission from 1931 ± 241 aMol until 1845 ± 199 aMol (NS) at day 4. From a minimum Ret-He value at day 4 results increased towards 2129 ± 136 aMol at day14. CONCLUSION: A transient increase of cytokine-stimulated serum hepcidin-25 in combination with a temporary decrease of Hb and Ret-He is demonstrated in patients with CAP. Our results support the hypothesis that hepcidin-25 induces transient impairment of reticulocyte hemoglobin content (Ret-He).

Efficacy of advanced discriminating algorithms for screening on iron-deficiency anemia and ß-thalassemia trait: a multicenter evaluation.

For many years, application of RBC indices has been recommended for discriminating between subjects with iron deficiency from those with thalassemia. However, application of the algorithms resulted in only 30% to 40% of subjects being appropriately classified. The aim of the study was to establish the efficacy of algorithms for anemia screening including new hematologic parameters such as percentage of hypochromic and microcytic RBCs and hemoglobin content of reticulocytes. Subjects with iron deficiency anemia (IDA) (n = 142) and subjects with ß-thalassemia (n = 34) were enrolled in a European multicenter study. Apparently healthy subjects were used as a reference group (n = 309). Hemocytometric investigations were performed on a Sysmex XE5000 hematology analyzer. The algorithms for IDA discrimination yielded results for area under the curve, sensitivity, specificity, and positive and negative predictive values of 0.88, 79%, 97%, 74%, and 98%, respectively. The algorithms for ß-thalassemia discrimination revealed similar results (0.86, 74%, 98%, 75%, and 99%, respectively). We conclude that the advanced algorithms, derived from extended RBC parameters provided by the Sysmex XE5000 analyzer, are useful as laboratory anemia screening devices.

D-dimer levels in assessing severity and clinical outcome in patients with community-acquired pneumonia. A secondary analysis of a randomised clinical trial.

BACKGROUND: D-dimer levels are in several studies elevated in patients with CAP. In this study we assess the use of D-dimer levels and its association with severity assessment and clinical outcome in patients hospitalised with community-acquired pneumonia. METHODS: In a subset of randomised trial patients with community-acquired pneumonia serial D-dimer levels was analysed. CURB-65 scores were calculated at admission. RESULTS: A total of 147 patients were included. D-dimer levels at admission were higher in patients with severe CAP (2166 ± 1258 versus 1630 ± 1197 µg/l, p=0.03), with clinical failure at day 30 (2228 ± 1512 versus 1594 ± 1078 µg/l, p=0.02) and with early failure (2499 ± 1817 µg/l versus 1669 ± 1121 µg/l, p=0.01). Non-survivors had higher D-dimer levels (3025 ± 2105 versus 1680 ± 1128 µg/l, p=0.05). None of the 16 patients with D-dimer levels<500 µg/l died. In multivariate analysis D-dimer levels were not associated with clinical outcome. D-dimer levels have poor accuracy for predicting clinical outcome at day 30 (AUC 0.62, 95% CI 0.51-0.73) or 30 day mortality (AUC 0.71 (95% CI 0.51-0.91)). Addition of D-dimer levels to CURB-65 did not increase accuracy. No differences were observed in serial D-dimer levels between patients with clinical success or failure at day 30. CONCLUSION: D-dimer levels are elevated in patients with CAP. Significantly higher D-dimer levels are found in patients with clinical failure and with severe CAP. D-dimer levels as single biomarker or as addition to the CURB-65 have no added value for predicting clinical outcome or mortality. D-dimer levels<500 µg/l may identify candidates at low risk for complications.

Effects of iron supplementation on red blood cell hemoglobin content in pregnancy.

Although a mild degree of anemia is common in the third trimester of pregnancy, it remains a challenge to establish whether a decrease in hemoglobin (Hb) concentration is physiological or pathological. The World Health Organization suggested a Hb concentration of 110 g/L to discriminate anemia. Several European investigators recommended Hb cut-off values of between 101-110 g/L. The aim of this study was to establish short-term effects of iron supplementation on the hemoglobin content of reticulocytes (Ret-He) and red blood cells (RBC-He) in case of suspected iron deficient erythropoiesis (IDE) in the third trimester of pregnancy. Twenty-five subjects with suspected IDE during pregnancy (Hb ≤110g/L, Ret-He <29.6 pg, zinc protoporphyrin >75 mol/mol hem) participated in the study. After iron supplementation, reticulocyte counts increased from 0.061±0.015×10(12)/L to 0.079±0.026×10(12)/L and Ret-He increased from 23.6±2.8 pg to 28.3±2.6 pg (P=<0.001). RBC-He increased from 26.9±1.9 pg to 27.4±1.8 pg (not significant, NS) and Ret-He/RBC-He ratio increased from 0.97±0.06 towards 1.07±0.05 (P=<0.001). Hb concentrations demonstrated an obvious increase from 105±6 g/L towards 115±5 g/L (P≤0.001) after supplementation. An obvious increase in RBC distribution width was observed from 45.0±3.6 fL towards 52.3±7.0 fL (P≤0.001). We recommend that Ret-He and Ret-He/RBC-He ratio be integrated into the protocols for anemia screening and for monitoring effects of iron supplementation during pregnancy. In particular, the parameters should be considered in subjects with Hb results in the controversial range of 101-108 g/L.

Platelet depletion, platelet activation and coagulation during treatment with hemodialysis.

Bioincompatibility is the total of side effects during hemodialysis (HD) including, amongst others, changes in platelet (PLT) level. Deviations in PLT count, immature PLT count, PLT morphology, CD62p expression, Platelet Factor 4 (PF4), ß-Thromboglobulin (ß-TG), serotonin, Thrombin-Antithrombin III (TAT) and Prothrombin Fragment 1+2 (F1+2) are monitored before and during treatment with HD in order to elucidate the interaction between modifications in PLT morphology, PLT activation and markers concerning activation of coagulation. Different patterns with time indicate that there is no correlation between an increased amount of depleted PLTs and increased amounts of PLT activation markers such as CD62p, PF4, ß-TG and serotonin. A statistically significant correlation between increased PLT activation markers and markers for increased activation of coagulation such as TAT and F1+2 has not been established. Only a weak correlation is demonstrated between the increase of markers for activation of coagulation and the decrease in PLT counts, immature PLT counts and depleted PLTs during HD treatment. The change in the extracorporeal circuit during HD is probably a more critical factor in the mechanism leading to activation of the coagulation pathway than the modifications in PLT morphology.

The role of the extracorporeal circuit in the trapping and degranulation of platelets.

BACKGROUND: Although platelet (PLT) activation and degranulation are well-known phenomena during hemodialysis (HD), controversies still exist about their nature and origin. METHODS: PLT characteristics [PLT numbers, mean PLT volume (MPV), PLT distribution width (PDW), PLT large cell ratio (p-LCR), immature PLT fraction] and activation status [CD62p expression, platelet factor 4 (PF4) and beta-thromboglobulin (BTG) plasma levels] were estimated in 19 patients before and during HD. Blood was sampled from both the afferent and efferent lines. Additionally, the influence of low-molecular-weight heparin (LMWH) on PF4 and BTG concentrations was analyzed. RESULTS: CD62p expression increased in the extracorporeal circuit (ECC) in the first 30 min. Simultaneously, PLT numbers dropped markedly within the ECC. MPV, PDW and p-LCR decreased over time. Like CD62p expression, BTG reached peak values at t30, was exclusively released within the ECC and was not influenced by the application of LMWH. In contrast, PF4 was significantly released outside the ECC in response to LMWH. CONCLUSIONS: PLTs are predominantly activated within the ECC and not on a remote distance. PLTs stick to the ECC, particularly after first passage. BTG is an appropriate marker for HD-induced PLT degranulation, whereas PF4 originates from both activated PLTs and LMWH-induced detachment from the endothelium. PLTs are not exhausted due to the repetitive stimulation of clinical HD. Hence, dialysis modalities with longer duration or greater frequency may be associated with a less beneficial PLT activation profile, which may counteract their clinical benefits.

Post-dilution haemodiafiltration and low-flux haemodialysis have dissimilar effects on platelets: a side study of CONTRAST.

BACKGROUND: Cardiovascular disease (CVD) is the leading cause of death in patients with end-stage renal disease (ESRD). Platelet (PLT) dysfunction, which is a well-known phenomenon in advanced chronic renal failure, corresponds positively with CVD in these patients. The accumulation of retained uraemic toxins might play an important role in this respect. During haemodialysis (HD), both an increase in the expression of the platelet (PLT) cell surface molecule P-selectin (CD62p) and the release of intra-granular substances, such as platelet factor 4 (PF4) and ss-thromboglobulin (BTG), have been described. As the removal of uraemic toxins is superior during haemodiafiltration (HDF), this form of treatment may have quite another impact on PLTs than HD. METHODS: Nineteen chronic HD patients who were treated with low-flux HD for at least 2 months were included in the Dutch CONvective TRAnsport STudy (CONTRAST). After randomization, 10 patients continued low-flux HD and 9 patients switched to post-dilution HDF. The present study describes various parameters of PLT activation and degranulation at baseline (during HD) and after 3 months (during HDF) in the latter group of patients. At both time points, multiple blood samples were drawn. During the first 30 min of treatment, differences over the extracorporeal circuit (ECC) were calculated by taking samples from both afferent (arterial) and efferent (venous) lines. Correlations between various parameters were calculated in the total group of patients after 3 months. RESULTS: Immediately after the start of HD, PLT counts dropped over the ECC. During HDF, PLT counts decreased even more and reached a nadir at t30. CD62p expression increased early during HD and returned to baseline thereafter. During HDF, these changes were more pronounced and more protracted. With respect to degranulation, rather dissimilar results were obtained. During HD, both PF4 and BTG increased over time, whereas during HDF, PF4 increased but BTG did not change. Haemoconcentration and transmembrane pressure (TMP) within the dialyser were, respectively, approximately 10 and 3x higher during HDF than during HD. There was a striking correlation between the changes in haemoconcentration and the changes in both PLT counts and CD62p over the ECC. SUMMARY AND CONCLUSIONS: PLT activation, as measured by the expression of CD62p, was more pronounced and more protracted during HDF than during HD. During HDF, PLTs were trapped abundantly within the ECC, not only after first passage, but also thereafter. The degranulation product BTG increased during HD, but did not change during HDF. These observations may well be explained by the greater haemoconcentration and/or higher TMP during HDF on the one hand, and superior convective transport at the other. Whether the potential harmful effects of enhanced PLT activation are counterbalanced by the beneficial effects of an increased convective transport of degranulation products remains to be established.

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.

Reduction in platelet activation by citrate anticoagulation does not prevent intradialytic hemodynamic instability.

BACKGROUND: The etiology of intradialytic hemodynamic instability is multifactorial. Of the various factors involved, a rise in core temperature seems to be crucial. In this respect, the bioincompatibility of hemodialysis (HD) treatment might play an important role. The application of cool dialysate reduces the number of periods of intradialytic hypotension (IDH) considerably. In rats, roller pump perfusion caused hypotension by shear stress induced platelet aggregation and subsequent serotonin release. During clinical HD, citrate anticoagulation abolished platelet activation almost completely. Hence, citrate anticoagulation might reduce IDH, whereas the beneficial effect of cool dialysate might be partly explained by reduced platelet activation. METHODS: In the present study, blood pressure, IDH episodes, platelet activation, platelet aggregation, and serotonin release were studied crossover in 10 patients during HD with dalteparin anticoagulation at normal and low dialysate temperatures and during HD with citrate. RESULTS: Citrate strongly reduced platelet activation, but did not improve IDH. The blood pressure was best preserved during cool-temperature HD, despite manifest platelet activation. Platelet activation was not accompanied by a rise in the plasma serotonin concentration. CONCLUSIONS: Three major conclusions can be drawn: (1) it is unlikely that platelet activation and subsequent serotonin release underlie IDH in the clinical situation; (2) the protective effects of cool dialysate on IDH appear to be independent of HD-induced platelet activation, and (3) extrapolating results from rat experiments to the human situation requires uppermost prudence.