Influence Of Hematocrit Research Articles

Reference values for thromboelastometry (ROTEM®) in cynomolgus monkeys (Macaca fascicularis)

Introduction The imbalance in clotting homeostasis, tending towards hypercoagulation, is recognized as the real barrier to the long-term survival of porcine xenografts in pig-to-primate xenotransplatation. The present study aimed to validate in primate blood the applicability of whole blood rotation thromboelastometry, performed by ROTEM®, which evaluates the characteristics of clot formation by dynamic monitoring. Materials and Methods ROTEM® (Pentapharm GmbH, Munich, Germany) was used to investigate native coagulation (NATEM®), the intrinsic (INTEM®) and extrinsic (EXTEM®) pathways, the function of fibrinogen (FIBTEM®), and the presence of fibrinolysis in 40 naïve cynomolgus monkeys. Using classic validation approaches, the normal thromboelastographic profile was defined and the influence of haematocrit (Hct,%), platelet count (x10 9/L), fibrinogen (mg/dl), and factor VIII (FVIII,%) was evaluated. Results In all four (NATEM®, INTEM®, EXTEM®, FIBTEM®) assays considered, Clotting Time (CT, sec) and Clot Formation Time (CFT, sec) were shorter in primates than humans. Moreover, α-angle (°), Maximum Clot Firmness (MCF, mm), and MaxVel (mm/min) were also higher in primates than humans. No substantial difference was observed for Hct and platelet count between the two species. On the contrary, FVIII was higher in primates than in humans whereas, interestingly enough, fibrinogen levels were lower in monkeys than in humans. Conclusion ROTEM® depicts a hypercoagulable profile in primates as compared to humans. Taken together these data suggest that, with regard to coagulation, xenotransplantation in cynos may represent a much more difficult situation than xenotransplantation in humans.

A mathematical model to assess the influence of hematocrit on point of care glucose meter performance

Objectives To develop and apply a mathematical model of the relationship between hematocrit, meter glucose and reference glucose concentrations as a tool for evaluation of whole blood glucose meters. Design and Methods Patient blood gas specimens were used to compare the LifeScan SureStep Flexx and the Nova StatStrip glucose meters with reference results obtained from a Radiometer 725 blood gas analyzer. Linear regression analysis was conducted to determine the extent that patient hematocrit and reference glucose concentrations predicted the performance of the glucose meters. Results Bland-Altman graphic analysis depicted that both glucose meters showed variance with the reference method. A mathematical model was derived from IFCC consensus equations that relate glucose meter results, hematocrit and plasma glucose values. Using the model, multivariate regression depicted that hematocrit affected the results of the SureStep Flexx meter in a manner dependent on the glucose concentration, whereas the StatStrip meter was not affected by hematocrit. Conclusions Linear regression can be used to quantify the extent of hematocrit interference on the performance of glucose meters.

Influence of hemorheological parameters and mean blood pressure on carotid blood flow asymmetry in patients with chronic unilateral cerebral infarctions

The study aimed to follow the influence of some hemorheological parameters and mean blood pressure (MBP) on the carotid blood flow asymmetry in 20 patients with chronic unilateral cerebral infarctions (UCI) as compared to 30 patients with transient ischemic attacks (TIAs), 17 patients with risk factors (RF) for cerebrovascular disease (CVD) and 11 healthy controls. Hemorheological variables: hematocrit (HT), plasma (PV) and whole blood viscosity (WBV), serum lipids and echocardiographic parameters were investigated. Blood pressure (systolic, diastolic and mean) was registered and color duplex sonography of the carotid arteries was performed. The lumen diameter, the intima media thickness (IMT) and the blood flow velocity (systolic, mean and diastolic) in the carotid arteries were examined and the velocity asymmetry ratio (AR) was calculated. Significant increase of HT in UCI, of mean blood pressure (MBP) in the patients with RF and TIAs and of IMT and velocity parameters in all patients was established. The correlation analysis revealed parallel influence of HT, MBP, cardiac function, IMT, lumen diameter and some of the modifiable RF on the carotid AR in patients with chronic UCI affecting mainly the collateral circulation. The complex investigation of these factors would enable us to individualize the therapeutic approach in the patients with cerebral ischemic events.

Effect of Blood Hematocrit and Erythrocyte Deformability on Adenosine 5′-Diphosphate Platelet Reactivity in Patients With Acute Coronary Syndromes on Dual Antiplatelet Therapy

Previous studies have explored the association between hemorheologic alterations and aspirin resistance, pointing out the possible interaction between hematologic components and platelet responsiveness to antiplatelet drugs. The aim of this study was to evaluate the association between hemorheologic variables and residual platelet reactivity in patients with acute coronary syndromes (ACSs) who underwent percutaneous coronary intervention on dual antiplatelet therapy. The study population included 528 patients with ACSs. Hemorheologic studies were performed by assessing whole blood viscosity at 0.512 and 94.5/second, plasma viscosity, and erythrocyte deformability index. Post-treatment platelet reactivity was investigated by measuring platelet aggregation by adenosine 5'-diphosphate (ADP) 10 mumol and a value >70% was defined as high ADP platelet reactivity. Significantly (p <0.01) lower values of hematocrit and erythrocyte deformability and higher values of whole blood viscosity at 94.5/second were found in patients with high ADP platelet reactivity. At multivariate analysis, lower values of hematocrit and erythrocyte deformability index and higher values of whole blood viscosity at 94.5/second and leukocytes (highest vs lowest tertile) also resulted in an independent association with high platelet reactivity, except for leukocytes, after simultaneous adjustment for hematocrit, leukocyte count, and erythrocyte deformability index. In conclusion, these results demonstrate the influence of hematocrit and of erythrocyte deformability on ADP platelet reactivity. These variables could be considered to optimize treatment with antiplatelet therapy in these patients.

Micro-Flow Visualization of Red Blood Cell-Enhanced Platelet Concentration at Sudden Expansion

Microscopic steps and crevices are inevitable features within prosthetic blood-contacting devices. This study aimed to elucidate the thrombogenicity of the associated microscopic flow features by studying the transport of fluorescent platelet-sized particles in a suspension of red blood cells (RBCs) flowing through a 100 microm:200 microm sudden expansion. Micro-flow visualization revealed a strong influence of hematocrit upon the path of RBCs and spatial concentration of particles. At all flow rates studied (Re = 8.3-41.7) and hematocrit 20% and lower, RBC streamlines were found to detach from the microchannel wall creating an RBC-depleted zone inside the step that was much larger than the cells themselves. However, the observed distribution of particles was relatively homogeneous. By contrast, the RBC streamlines of samples with hematocrit equal to or greater than 30% more closely followed the contour of the microchannel, yet exhibited enhanced concentration of particles within the corner. The corresponding size of the cell depletion layer was comparable with the size of the cells. This study implies that local platelet concentration in blood within the physiological range of hematocrit can be elevated within the flow separation region of a sudden expansion and implicates the role of RBCs in causing this effect.

Influence of haematocrit on international normalised ratio (INR) differences between a whole blood point-of-care coagulation monitor and reference prothrombin time in plasma

The CoaguChek S system is designed for use in patient self-testing. In this system a whole blood sample without sodium citrate is applied to a test strip containing thromboplastin and iron oxide particles. The detection principle is based on fibrin formation which inhibits and finally stops the movement of the iron oxide particles. In the classic prothrombin time (PT) test, citrate plasma is mixed with thromboplastin and an excess of calcium ions. In the monitoring of vitamin K-antagonist (VKA) treatment, all results are expressed on a common scale, i.e. international normalised ratio (INR). In patients on long-term VKA treatment, INRs were determined by the CoaguChek S system and reference methods for the classic PT. Four different CoaguChek S strip lots were evaluated. The difference in INR between the reference PT and the CoaguChek S system was negatively correlated to the haematocrit of the patients. We conclude that INR differences between CoaguChek S and plasma PT may be explained in part by the haematocrit. The magnitude of the effect of haematocrit, within the reference interval of 0.37 - 0.51, on the INR difference was not greater than approximately 10% for the combined data of the four strip lots. A bias of less than 10% seems to be acceptable clinically.

1123 細血管内を流動する赤血球運動のメゾスコピック解析(J05-1 血液循環系のバイオエンジニアリング:医療技術への展開(1),J05 血液循環系のバイオエンジニアリング:医療技術への展開)

A simulation method to analyze mesoscopic rheology of blood by multi-scale modeling of blood flow was proposed. Blood flow at a microscopic scale was modeled as flowing red blood cells, while blood flow at a macroscopic scale was treated as a continuum where a local variation of viscosity which is a function of a local concentration of red blood cells was taken into account. The simulation results were in good agreement with in vivo results. The paper also discusses the influence of hematocrit on the velocity profile of a macroscale flow.

Characterization of Blood Properties from Coagulating Blood of Different Hematocrits Using Ultrasonic Backscatter and Attenuation

The influence of hematocrit on the change of blood properties during coagulating was extensively investigated using ultrasonic integrated backscatter and attenuation. Measurements were performed with porcine blood at hematocrits ranging from 25 to 55% using a 10 MHz transducer. Results showed that both integrated backscatter and attenuation are able to sensitively differentiate various stages of blood properties during coagulating. The slopes of integrated backscatter (Sr, dB/S) and attenuation (αr, dB·cm-1·MHz-1·mS-1) are increased relative to hematocrit. The best fits for Sr and αr as a function of hematocrit (H) equal to Sr=0.0357+1.62e-0.108H and αr=0.0281+0.003H, respectively. Variations of clotting time (Ts) and reaction time (Tα), estimated respectively from ultrasonic integrated backscatter and attenuation, associated with clot formation are also increased with hematocrit. This study demonstrates that blood hematocrit is a substantial factor affecting viscosity and backscattering properties of blood during coagulation capable of being discerned by ultrasonic backscattering and attenuation.

Influence of hematocrit and localisation of punch in dried blood spots on levels of amino acids and acylcarnitines measured by tandem mass spectrometry

Background Detection of amino acids (AA), acylcarnitines (AC), and guanidinoacetate (GAA) in dried blood spots by tandem mass spectrometry has made it possible to detect different inborn errors of metabolism in neonatal screening programs. Despite its proven sensitivity many issues related to sample preparation remain unsolved. Hematocrit has a profound effect on blood viscosity, and may thereby influence flux and diffusion properties of the blood. As newborn infants show a considerable interindividual variability of hematocrit levels, we investigated its effect on levels of AA and AC in dried blood spots. Methods Blood samples with defined hematocrit levels (20%, 30%, 40%, 50%, 60%) were produced by diluting blood cells with plasma from a single donor. Forty dried blood spots were made for each hematocrit level and a central as well as a peripheral 3 mm disk was punched and analysed for AA, AC, and GAA, respectively. Results Levels of most AA and GAA increased significantly with increasing hematocrit ( p < 0.001), while the effect of hematocrit on some AA was less pronounced. Total AC, free carnitine, some long, medium and short chain AC correlated positively with hematocrit levels ( p < 0.001). In samples with low hematocrit, levels of most AA and free carnitine were higher in the peripheral than in the central disk ( p < 0.0001). Conclusions Both hematocrit and position of the disk within the dried blood spot have a significant and sometimes additive effect on levels of AA, AC and GAA in dried blood spots. Theoretically, diagnoses may be missed depending on hematocrit and position of the disk.

Influence of hematocrit and pump prime on cerebral oxygen saturation in on-pump coronary revascularization

The couplings between cerebral oxygenation (rSO2), on-pump hematocrit and circuit prime are explored in this study. Thirty-eight consecutive patients undergoing coronary revascularization with cardiopulmonary bypass (CPB) were matched on preoperative hematocrit < 40% and > 40% (n = 16). Similarly, six blood prime patients were matched with six crystalloid prime patients. Hematocrit and rSO2 levels were then compared on CPB. The preoperative hematocrit > 40% group retained higher levels on pump run (p < 0.01) and significantly higher rSO2 prior to CPB (64.8 +/- 9.6 versus 73.2 +/- 7.3), and on and off CPB (61.1 +/- 8.8 versus 67.4 +/- 6.4). Blood priming increased absolute rSO2 (2.3 +/- 6.3 versus -10.9 +/- 5.9) and % rSO2 (4.7 +/- 11.8 versus -14.2 +/- 7.4%) in the low hematocrit group. Blood primes are instrumental in high-risk and low preoperative hematocrit patients in preventing cerebral oxygen desaturation during initiation and maintenance of CPB.

Postoperative changes in blood viscosity and the influence of haematocrit and plasma-fibrinogen.

Abstract The blood of 25 patients undergoing surgery has been investigated for levels of whole-blood and plasma viscosity, haematocrit, and plasma-fibrinogen before and after operation. The whole-blood viscosity diminished by between 14 and 23 per cent after operation. The haematocrit fell from a mean preoperative level of 42.3 per cent (S.D. ± 5.2) to a mean postoperative level of 36.3 per cent (S.D. ± 5.5). When the effect on viscosity of this reduction in haematocrit was removed the blood viscosity rose after operation by 9–14 per cent. The level of plasma-fibrinogen rose from a mean preoperative level of 360 mg. per cent (S.D. ± 78) to a mean postoperative level of 714 mg. per cent (S.D. ± 155), an overall increase of 98 per cent. This postoperative rise in the plasma-fibrinogen concentration exerted an effect on the blood viscosity opposite to that of the haematocrit. The deleterious effects of a rise in blood viscosity on tissue perfusion and oxygenation are outlined, and the relevance of the reported findings to the maintenance of an adequate microcirculation in the postoperative period is discussed. Attention is drawn to the benefits of a slight fall in haematocrit during this period.

Haematocrit and the risk of developing end-stage renal disease.

Anaemia is common in patients with renal failure; however, it is not known whether haematocrit level in the general population is a predictor for developing end-stage renal disease (ESRD). A retrospective analysis was conducted to assess the development of ESRD within a population of 71 802 subjects (37 190 men and 34 612 women), 20-99 years, in Okinawa, Japan. Haematocrit data were collected between April 1983 and March 1984 and the subjects were followed forward to the year 2000 whether they were identified in the Okinawa Dialysis Study registry for identification of ESRD. Multivariate logistic analyses were performed to analyse the influence of haematocrit on the development of ESRD after adjusting for age, sex, blood pressure, body mass index, proteinuria and haematuria. In a subgroup of the cohort, similar analyses were repeated adjusting for estimated creatinine clearance by the method of Cockcroft and Gault. The mean (SD) level of haematocrit at the time of screening was 45.3% (3.3%) for men and 38.8% (3.2%) for women. During the 17-year follow-up, 269 patients (171 men and 98 women) were identified with ESRD. The mean time to onset of ESRD was 130.4 (53.6) months. The adjusted odds ratio and 95% confidence interval (CI) for the influence of haematocrit (%) on the development of ESRD was 0.991 and 0.988-0.995 (P<0.0001), suggesting that the lower haematocrit, the greater was the risk of developing ESRD. This finding was repeated in the subgroup analysis that included calculated creatinine clearance (adjusted odds ratio 0.991 and 95% CI 0.984-0.997, P=0.0057). In women, the adjusted odds ratio for haematocrits of 20.0-34.9% was 3.086 (CI 1.770-5.376, P<0.0001) when compared with the reference haematocrits of 35.0-39.9%. In men, the adjusted odds ratio for haematocrits of 25.0-39.9% was 1.927 (CI 1.418-2.625, P<0.0001) when compared with the reference haematocrits of 45.0-49.9%. Subjects with low haematocrits, <40% for men and <35% for women, have a significantly increased risk of ESRD.

Influence of Platelet Count, Acetylsalicylic Acid, von Willebrand’s Disease, Coagulopathies, and Haematocrit on Results Obtained Using a Platelet Function Analyser in Dogs

The platelet function analyser PFA-100 aspirates blood in vitro from a sample reservoir in disposable test cartridges through a microscopic aperture cut into a biologically active membrane at the end of a capillary. In different cartridges the membrane is coated with collagen and adenosine diphosphate (ADP) or collagen and epinephrine (adrenaline) inducing a platelet plug and closure of the aperture. The closure time and total volume of blood flow through the capillary until closure of its aperture were measured. The correlation between platelet count in samples of thrombocytopenic dogs and results of the collagen/ADP cartridge (closure time: r S=−0.579; total volume: r S=−0.549) was closer than between platelet count and capillary bleeding time. No significant correlation was observed between platelet count and the results obtained with the collagen/epinephrine cartridge. In addition, a higher sensitivity was obtained for the collagen/ADP cartridge. Injection of acetylsalicylic acid into healthy dogs significantly increased closure time and total volume of both types of cartridges ( P<0.01). Two dogs with von Willebrand’s disease had abnormal values. In contrast, coagulopathies did not significantly influence the results of the platelet function analyser ( P>0.05). Despite adequate sensitivity of measurements using the collagen/ADP cartridge to assess quantitative and qualitative platelet disorders in dogs, the influence of haematocrit ( P<0.0001) will limit the clinical application of the analyser.

Influence of haematocrit on BOLD signal change. Linear or non-linear?

Influence of haematocrit on BOLD signal change. Linear or non-linear?

Early Detection of Preeclampsia by Determination of Platelet Aggregability

Preeclampsia is still a leading cause of maternal and fetal morbidity and mortality. There is evidence for the involvement of platelets. Therefore, we investigated the suitability of corrected whole blood impedance aggregometry as an early predictor of preeclampsia in 71 consecutive, high-risk pregnancies. According to the occurrence of preeclampsia, defined postpartum by an independent investigator, and the stage of pregnancy (early and late, cutoff: 25 weeks of gestation), four study groups were defined. Platelet aggregation data were corrected for the influence of hematocrit and platelet count by a special purpose software package. Women developing preeclampsia showed significantly higher platelet aggregation response compared to controls in early and late pregnancy. In early pregnancy, all women developing preeclampsia had aggregation responses to collagen higher than the highest responses among the controls. Hence, this test had a 100% positive predictive value of subsequent preeclampsia. Despite being significantly increased, platelet aggregability was of minor predictive value in late pregnancy. We conclude that preeclampsia is accompanied by exaggerated platelet aggregability, particularly perceptible early in the course of pregnancy. We propose collagen-induced whole blood platelet aggregation with correction for the influence of hematocrit and platelet count for early detection of preeclampsia.

Influence of hematocrit on hemostasis in continuous venovenous hemofiltration during acute renal failure

Influence of hematocrit on hemostasis in continuous venovenous hemofiltration during acute renal failure

Cerebral blood flow velocity during isovolemic hemodilution and subsequent autologous blood retransfusion.

To quantify the influence of hematocrit on cerebral blood flow velocity (CBFV) in healthy volunteers undergoing acute isovolemic hemodilution (HD) with hydroxyethyl starch 10% (HES) and subsequent autologous whole blood retransfusion (RT). In 11 volunteers 20 ml x kg(-1) blood was withdrawn over 30 min and simultaneously replaced with HES 10%. Thirty min later, RT was started at a constant rate over 30 min. Recorded parameters included: CBFV pulsatility-index (PI) and resistance-index (RI) of the middle cerebral artery (MCA). Blood pressure (BP), heart rate (HR), hemoglobin (Hb), hematocrit (Hc) peripheral O2-saturation (SpO2), P(ET)CO2, arterial oxygen content (CaO2) and cerebral arterial O2-transport (C(E)-DO2= CaO2 x Vm-MCA) were monitored. An average of 1570 total blood was withdrawn which resulted in a decrease in Hb from 14.5 mg x dl(-1) to 10.3 mg x dl(-1); Hc (and CaO2) decreased from 41.8% (19.8 ml x dl(-1)) to 29.6% (14.2 ml x dl(-1); P < 0.01). Vm-MCA increased from 61.2 cm x sec(-1) to 77.3 cm x sec(-1) (P < 0.01). Following RT, Vm-MCA decreased again, but remained higher than baseline (P < 0.01). PI decreased by 13% following RT (P < 0.05). There were no changes in RI, HR, BP SpO2 and P(ET)CO2. Regression lines could be fitted between Hc and Vm-MCA, Vm-MCA and CaO2, and between Hc and C(E)DO2. Transcranial Doppler changes in blood flow velocities correlated with the simultaneously recorded systemic Hc and CaO2 values. We found a 2% increase in CBFV for each 1% decrease in Hc and CaO2.

Hemodynamic Properties of the Hemopump HP14

The Hemopump HP14 is a catheter-mounted, transvalvular, left ventricular assist device intended for femoral percutaneous insertion. The pump was developed for patients with postoperative or postinterventional low cardiac output and for CABG surgery on the beating heart. Little is known about the effect of afterload and hematocrit on the pump performance. The influence of hematocrit and afterload on the pump flow was tested using an in vitro model filled with heparinized bovine blood. Regression analysis of the pump flow with respect to three hematocrit values (20%, 30%, 40%) and ten afterload levels (30 mmHg-120 mmHg in 10 mmHg increments) was performed for all pump speed levels (n = 7). At all pump speed levels reduction of afterload and hematocrit were significant predictors for increasing pump flow (p<0.001). For hematocrit values between 40% and 20% and highest pump speed, mean pump flow at lowest afterload ranged between 2.34 and 2.53 L/min; and at highest afterload between 1.31 and 1.53 L/min. For speed level 1, afterload of 120 mmHg and hematocrit of 40% there was a maximal retrograde flow of 230+/-35 ml/min. Pump performance is significantly improved by both afterload and hematocrit reduction. In the weaning phase and during the removal of the device, the pump should run at a speed level of at least three to prevent retrograde flow in the pump. Estimates for pump flow in vivo can be extrapolated from our diagrams. Our results show that the Hemopump HP14 is a valuable alternative to intra-aortic balloon counterpulsation.

Influence of hematocrit on the measurement of lipoproteins demonstrated by the example of lipoprotein(a)

The measurement of many parameters of human blood is usually performed in plasma or serum. Since lipoproteins or apolipoproteins, for example, are found almost exclusively in the plasma fraction after low-speed centrifugation, these parameters can be expected to be distributed in a different plasma volume depending on the hematocrit value. Therefore, the measured plasma levels might be relatively too low or too high in comparison to the whole blood concentrations in the case of abnormal hematocrit levels. The aim of our experiments was to evaluate the extent of differences between whole blood and plasma concentrations, taking as an example lipoprotein(a) [Lp(a)] in hemodialysis patients with documented decreased hematocrit values. Lp(a) was measured in plasma as well as whole blood of 15 hemodialysis patients with low hematocrit values (0.29 +/- 0.02) in comparison to 11 control subjects (0.45 +/- 0.04). Plasma concentrations were 27% higher in patients than in controls (19.7 vs. 15.5 mg/dl). The relative difference was twice as high (59%) when measured in whole blood (13.5 vs. 8.5 mg/dl). Similar relative differences were observed when whole blood concentrations of 125 hemodialysis patients and 256 controls were calculated with the formula [Lp(a)plasma * (1-hematocrit)]. Our findings clearly demonstrate that hematocrit is a strong confounding variable of lipoprotein measurement in epidemiological studies when concentrations are measured in plasma, especially in cases of abnormal hematocrit values. Furthermore, studies investigating the longitudinal changes of lipoproteins should consider potential hematocrit changes.

Blood low shear rate rheometry: influence of fibrinogen level and hematocrit on slip and migrational effects

Red blood cell (RBC) aggregation is of prime importance in vivo and in vitro for low flow rates. It may be estimated by rheometrical measurements at low shear rates, but these are perturbed by slip and migrational effects which have already been highlighted in the past. These effects lead to a torque decay with time so that the true value of the stress at low shear rates may be greatly underestimated. Elevated aggregation being associated with different diseases, pathological blood samples show more pronounced perturbing effects and a strong time dependency in low shear rate rheometry. To test the dependence of slip and migrational effects on RBC aggregation, and particularly to determine the way in which they depend upon fibrinogen concentration ([Fb]), a home-made measuring system with roughened internal and external walls (170 μm roughness) was used to study low shear rate rheometry for RBC suspensions in PBS buffer containing albumin (at 50 g/l) and fibrinogen at various concentrations. The influences of hematocrit, shear rate, and fibrinogen concentration were investigated. Particular attention was paid to data acquisition at low shear rates (10 −3 s −1 to 3 × 10 −2 s −1). The combined influence of hematocrit and fibrinogen was investigated by adjusting hematocrit to 44 or 57% and fibrinogen concentration ([Fb]) to 3.0-4.5-6.5 g/l. Microscopic observations of the blood samples at rest were performed. They showed that different structures were formed according to fibrinogen concentration. The rheometrical measurements indicated that torque decay with shearing duration was strongly dependent on fibrinogen concentration and on shear rate at fixed hematocrit. Migrational and slip effects were more pronounced as shear rate decreased, fibrinogen concentration was raised, and hematocrit was lowered. The results have been explained on the basis of the expected microstructure of flowing blood in relation to the microscopic observations at rest.