Viscoelastic Properties Of Blood Research Articles

Method Comparison Analysis of Quantra Relative to Rotational Thromboelastometry and Conventional Coagulation Testing in Cardiac Surgery

Background: Perioperative utilization of viscoelastic testing to guide the hemostatic management of patients undergoing cardiac surgery is recommended. Historically thromboelastography (TEG) and rotational thromboelastometry (ROTEM) have been used in this setting. The Quantra platform is a new cartridge-based, point-of-care, viscoelastic testing device that utilizes ultrasound to characterize dynamic changes in the viscoelastic properties of blood during clot formation. At present, limited studies addressing the interchangeability of viscoelastic testing parameters exist. Consequently, we conducted a method comparison of Quantra relative to rotational thromboelastometry (ROTEM) and conventional coagulation testing (CCT) in patients undergoing surgery requiring cardiopulmonary bypass (CPB). Aims: This study aimed to assess the correlation and agreement between Quantra, ROTEM, and CCT results using blood samples from cardiac surgery patients. Methods: Blood samples were collected during cardiopulmonary bypass from 127 adult patients undergoing cardiac surgery requiring CPB (after rewarming to 36°C) and before protamine administration. Samples were evaluated in parallel using Quantra, ROTEM, and CCT. Quantra parameters using the QPlus Cartridge included clot time (CT), heparinase clot time (CTH), clot time ratio (CTR), clot stiffness (CS), fibrinogen (FCS), and platelet (PCS) contributions to CS. ROTEM measurements assessed included CT, clot firmness at 20 minutes (A20) and maximum clot firmness (MCF). CCTs included PT, PTT, fibrinogen concentration, and platelet count. Method comparison analyses were performed using Deming Regression to assess the correlation between comparable parameters of Quantra, ROTEM, and CCT. To compare CS and A20/MCF parameters, ROTEM clot amplitudes were transformed from millimeter to Pascals using a conversion formula [((500*mm)/(100-mm))/100]. Individual test results were evaluated for agreement of clinical classifications (low, hemostatic function decreased; normal, hemostatic function within established reference range; high, hemostatic function elevated) relative to reference intervals using a clinical composite index (CCI). Results: Deming regression analysis demonstrated a moderate to very strong correlation between Quantra and ROTEM parameters, with rs values between 0.56 to 0.91 (Table 1). A strong correlation was observed between FCS and fibrinogen concentration and PCS and platelet count (rs=0.77 and rs=0.70, respectively). Despite showing acceptable correlation, Deming regression showed significant constant and proportional biases when comparing comparable parameters. As assessed by the CCI, the overall percent agreement between the Quantra and ROTEM parameters and Quantra and CCT were 64% to 82% (Table 2) and 50% to 72%, respectively. Analysis of agreement between each modality using Cohen's weighted kappa indicated fair to a substantial agreement between Quantra and ROTEM parameters and slight to moderate agreement between Quantra and CCTs parameters. Conclusion: Findings from this method comparison demonstrate that Quantra parameters correlated strongly with corresponding parameters from ROTEM and CCT. However, observed biases following Deming regression analysis indicate that these viscoelastic platforms are not interchangeable; local reference ranges should be established before adopting and clinical use of alternative platforms. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Evaluation of Blood Coagulation by Optical Vortex Tracking.

Blood coagulation is a complicated dynamic process that maintains the blood’s fluid state and prevents uncontrollable bleeding. The real-time monitoring of coagulation dynamics is critical for blood transfusion guidance, emergency management of trauma-induced coagulopathy, perioperative bleeding, and targeted hemostatic therapy. Here, we utilize optical vortex dynamics to detect the blood coagulation dynamic process in a rapid and non-contact manner. To characterize the temporal changes in viscoelastic properties of blood during coagulation, we track the stochastic motion of optical vortices in the time-varying speckles reflected from 100 blood samples with varied coagulation profiles. The mean square displacement (MSD) of the vortices increases nonlinearly with time lag during blood coagulation reminiscent of the particles in viscoelastic fluids. The MSD curves with coagulation time are similar to the tracings of thromboelastography (TEG) during the blood coagulation. The retrieved coagulation parameters, such as reaction time and activated clotting time measured using the optical vortex method, exhibit a close correlation to those parameters acquired from TEG. These results demonstrate the feasibility of the optical vortex method for monitoring blood coagulation at the point of care. Our method is also applicable to measuring the viscoelasticity of complex fluids and turbid soft matters.

Blood Viscosity in COVID-19 Patients With Sudden Deafness

BackgroundChanges in blood viscoelastic properties have been proposed previosuly as etiopathogenesis for severe complications in COVID-19 and some cases of Sudden Deafness (SD). This is an attempt to verify if SD cases in patients admitted for SARS-Cov-2 infection can be correlated. Patients and methodsA prospective follow-up was carried out with COVID-19 patients, monitoring their blood viscosity (BV) at high shear rate (300 s−1) and inquiring them periodically for eventual hearing loss. This measurement was extended to cases bearing of SD in 2019 and 2020 without infection and a control group of healthy normoacoustic subjects. ResultsThe normality range was 4,16 ± 0,62 cps. 330 cases admitted for COVID-19 were evaluated from February 24th, 2020 to March 24th, 2021, 85 of them attended in ICU. After anamnesis and Audiometric Tone Thresholds developed as soon as possible, 9 SD were detected, all belonging to ICU group. The mean BV was 4,38 ± 0,43 cps in the ward group, 4,53 ± 0,39 cps in the ICU patients without SD, and 4,85 ± 0,52 cps in the cases with SD, with statistically significant differences. Highest BV elevations in the SD cases were detected between days 6 and 10 of hospital admission. In 2019 four cases consulted with SD, and another two did it in 2020 without a diagnosis of COVID-19, with normal BV values. ConclusionsDuring SARS-Cov-2 infection, patients may show high BV and SS, although an inpatients control group and a larger sample volume are necessary to confirm the predisposition to hyperviscosity. The incidence of hearing damage is considerable if its possible appearance is taken into account, within the limitations of critical patients with COVID-19.

Study of the Effect of Low-Intensity Sub- and Millimeter Waves on the Induction of Adaptation Reactions in Experimental Burn

Burns are an actual problem of modern medicine. Oxidative stress, microcirculation, and hemostasis disorders are important links in the pathogenesis of burn disease. It is shown that these processes are significantly influenced by the point effect of low-intensity (LI) electromagnetic radiation (EMR) of the millimeter (MM) and submillimeter (subMM) ranges. However, the final opinion on the advantages of a particular range has not been formed. We have given a comparative assessment of the results of the effects of various frequency-energy parameters of microwaves on the indicators of adaptive reactions in rats under experimental thermal trauma and viscoelastic properties of blood in the case of burn disease.

The effect of hyperoxia on the hemostasiological status of severely burned patients.

The state of the hemostasis system was studied in 9 patients of the middle age group (44 ± 9.94 years) who received thermal trauma on an area of more than 32% (49.4 ± 18.3) of the body surface, accompanied by the development of burn shock. The standard therapy for burn injury was supplemented with HBO sessions. Treatment with hyperbaric oxygen was carried out in pressure chambers BLKS-307, BLKS-307/1. The state of the coagulation, anticoagulant and fibrinolytic links of the hemostasis system, as well as the viscoelastic properties of the blood, were assessed immediately before the HBO session and immediately after it. The total number of comparison pairs was 45. Under the influence of HBO therapy, there was an increase in the activity of antithrombin III (ATIII), protein C (PrS) and a decrease in the viscoelastic properties of blood (p <0.05). Positive deviations in the values of ATIII, Pr C, von Willebrand factor, APTT, prothrombin and thrombin time, fibrinogen, factor XIII, XIIa-dependent fibrinolysis, D-dimers and thromboelastography parameters were revealed. The maximum frequency of their occurrence was recorded for ATIII (95%), the minimum - for the D-dimer (62%). After HBO procedures, undesirable deviations of the hemostatic system parameters were also noted. They were chaotic, were compensated by an increase in the activity of physiological anticoagulants and were not accompanied by complications of a thrombogenic nature. Thus, conducting HBO therapy sessions in the acute period of burn disease increases the activity of physiological anticoagulants and stabilizes the viscoelastic properties of blood. There is a high frequency of occurrence of positive effects of hyperoxia on the components of the hemostasis system. The identification of its undesirable effects indicates the need to monitor the state of the hemostasis system during HBO procedures.

Thrombogenicity markers for early diagnosis and prognosis in COVID-19: a change from the current paradigm?

Standard biomarkers have been widely used for COVID-19 diagnosis and prognosis. We hypothesize that thrombogenicity metrics measured by thromboelastography will provide better diagnostic and prognostic utility versus standard biomarkers in COVID-19 positive patients. In this observational prospective study, we included 119 hospitalized COVID-19 positive patients and 15 COVID-19 negative patients. On admission, we measured standard biomarkers and thrombogenicity using a novel thromboelastography assay (TEG-6s). In-hospital all-cause death and thrombotic occurrences (thromboembolism, myocardial infarction and stroke) were recorded. Most COVID-19 patients were African--Americans (68%). COVID-19 patients versus COVID-19 negative patients had higher platelet-fibrin clot strength (P-FCS), fibrin clot strength (FCS) and functional fibrinogen level (FLEV) (P ≤ 0.003 for all). The presence of high TEG-6 s metrics better discriminated COVID-19 positive from negative patients. COVID-19 positive patients with sequential organ failure assessment (SOFA) score at least 3 had higher P-FCS, FCS and FLEV than patients with scores less than 3 (P ≤ 0.001 for all comparisons). By multivariate analysis, the in-hospital composite endpoint occurrence of death and thrombotic events was independently associated with SOFA score more than 3 [odds ratio (OR) = 2.9, P = 0.03], diabetes (OR = 3.3, P = 0.02) and FCS > 40 mm (OR = 3.4, P = 0.02).This largest observational study suggested the early diagnostic and prognostic utility of thromboelastography to identify COVID-19 and should be considered hypothesis generating. Our results also support the recent FDA guidance regarding the importance of measurement of whole blood viscoelastic properties in COVID-19 patients. Our findings are consistent with the observation of higher hospitalization rates and poorer outcomes for African--Americans with COVID-19.

Viscosidad sanguínea en pacientes COVID-19 con sordera súbita

AntecedentesLa alteración en las propiedades viscoelásticas de la sangre ha sido anteriormente propuesta como etiopatogenia de complicaciones severas por COVID-19 y algunos casos de sordera súbita (SS). Pretendemos verificar si la aparición de casos de SS en pacientes ingresados por infección por SARS-CoV-2 puede correlacionarse de este modo.Pacientes y métodosEstudio longitudinal prospectivo de pacientes ingresados en nuestro Centro por COVID-19, efectuando monitorización de la viscosidad sanguínea (VS) a alta velocidad de cizallamiento (300 seg-1) y un requerimiento periódico personal sobre hipoacusia. Esta determinación se extendió a casos atendidos por SS sin infección en 2019 y 2020 y un grupo control de sujetos sanos normoacúsicos.ResultadosEl rango de normalidad se situó en 4,16±0,62 cps. Entre el 24 de febrero de 2020 y el 24 de marzo de 2021 se evaluaron 330 casos ingresados por COVID-19, 85 asistidos en la Unidad de Cuidados Intensivos (UCI). Fueron identificadas tras anamnesis y Audiometría Tonal Liminar (ATL) todo lo inmediata que el status clínico lo permitió hasta nueve casos con SS, todos pertenecientes al grupo de UCI. La VS media fue 4,38±0,43 cps en el grupo de sala, 4,53±0,39 cps en los pacientes en UCI sin SS, y 4,85±0,52 cps en los casos con SS, con diferencias estadísticamente significativas. Las mayores elevaciones de la VS en los casos con SS se detectaron entre los días seis y 10 del ingreso hospitalario. En 2019 consultaron cuatro casos y otros 2 en 2020 sin diagnóstico de COVID-19, con valores normales de VS.ConclusionesDurante la infección por SARS-CoV-2 los pacientes pueden presentar elevación en la VS y SS, si bien se hacen necesarios un grupo control hospitalario y un volumen muestral mayor para confirmar la predisposición a la hiperviscosidad. La incidencia del daño auditivo resulta considerable si se tiene en cuenta su posible aparición en pacientes críticos con COVID-19.

Relationship of Edoxaban Plasma Concentration and Blood Coagulation in Healthy Volunteers Using Standard Laboratory Tests and Viscoelastic Analysis.

The capability of viscoelastic measurement parameters to screen anticoagulation activity of edoxaban in relation to its plasma concentrations was evaluated in 15 healthy male volunteers. Blood samples were drawn before the oral administration of edoxaban 60 mg and 2, 4, 6, 8, and 24 hours after administration. At each time, standard coagulation tests were performed, blood viscoelastic properties were measured with a thromboelastometry device ROTEM delta analyzer (Instrumentation Laboratory, Werfen, Barcelona, Spain), and edoxaban plasma concentrations were measured. Our primary interest was the possible correlation between edoxaban plasma concentrations and values for ROTEM ExTEM, and FibTEM. We also studied the correlation of edoxaban plasma concentrations with the results of standard coagulation tests. We saw the effect of a single dose of edoxaban most clearly in clotting time (CT) of ROTEM ExTEM and FibTEM. Changes in these parameters correlated significantly with edoxaban plasma concentrations up to 6 hours from the ingestion of the drug. Activated partial thromboplastin time, prothrombin time, and anti-factor Xa were also affected. Peak changes were observed 2 and 4 hours after administration of edoxaban. The changes were mostly reversed after 8 hours. In conclusion, ROTEM CT correlates significantly with edoxaban plasma concentrations and can be used to estimate the effect of edoxaban. ROTEM should be considered as part of the assessment of coagulation, with the big advantage of being readily available on site.

Thrombin generation and thromboelastometry tests in dogs with chronic kidney disease

ABSTRACT: Patients with chronic kidney disease (CKD) have paradoxical hemostatic potential because they have bleeding episodes but are also prone to thrombosis. Few studies have evaluated blood viscoelastic properties in dogs with kidney disease; on the other hand, hypercoagulability has been observed in these patients. It is also emphasized that the platelet function and its participation in this process have not yet been fully understood. The objective of this study was to evaluate and compare the Thrombin Generation Test (TGT) and also viscoelastic properties of the blood measured by thromboelastometry (TEM) in dogs with proteinuria in CKD. Twenty healthy dogs (Control Group) and 19 dogs with CKD in stage III or IV, classified according to International Renal Interest Society - IRIS, were selected, and the reference test of urine protein:creatinine ratio (UPCR) should be greater than one (CKD group). Blood samples for TEM, thrombin generation, Prothrombin Time (PT), activated Partial Thromboplastin Time (aPTT), and fibrinogen concentration was collected at a single time for both groups after inclusion criteria being confirmed. Statistical analysis was performed according to the distribution of variables at 5% significance level. Differences were observed between healthy dogs and those with proteinuria in CKD noted in TEM. The TGT was unable to differentiate between sick and healthy groups. However, when the nephropathy was stratified, increases in TTP and peak thrombin concentration by TGT were observed in females and dogs over 30 days of diagnosis of CKD. Both tests signaled a discrete state of hypercoagulability. In fact, TEM is more sensitive to detect hypercoagulability in dogs with CKD. However, the TGT has potential clinical application by allowing long-term sample storage.

Numerical simulation of blood flow in abdominal aortic aneurysms: Effects of blood shear-thinning and viscoelastic properties

In this study numerical simulation of blood flow in abdominal aortic aneurysms is presented. The novelty in this study is the consideration of the blood viscoelastic properties to account for the presence of red blood cells in addition to the shear-thinning behavior. The Oldroyd-B model is used to account for the viscoelasticity while the Carreau–Yasuda model is used to represent the shear-thinning property. The artery with its aneurysms is modeled as a planar channel with rigid wavy walls. The governing equations are solved numerically using the Galerkin/least-squares finite element method. Results are obtained for different values of flow rate under steady conditions. Our results assert that the blood shear-thinning behavior and viscoelasticity cannot be neglected especially for low shear rates conditions.

Trauma-induced coagulopathy. A narrative review of goal-directed hemostatic resuscitation

Post-traumatic haemorrhage is the leading cause of death in trauma patients. The development of coagulopathy substantially contributes to bleeding severity and to the ensuing unfavourable outcome. Trauma-induced coagulopathy (TIC) can be seen in 10-25% of patients with major trauma, and its early and appropriate therapeutic management leads to considerable reduction of mortality risk. Due to the extreme complexity of TIC pathophysiology, the limitations of conventional coagulation tests (CCTs) have become evident in recent years. Unlike these routine tests, point of care viscoelastic tests (VET) such as thromboelastogram (TEG) or rotational thromboelastography (ROTEM) provide valuable clinical information by real time assessment of changes in viscoelastic properties of blood throughout clot formation. This review was aimed to collect and discuss available evidence on goal-directed hemostatic resuscitation, based on TEG or ROTEM data. We included studies with patients aged 18 years or older, major trauma, and needing massive transfusions. Overall, 6 studies totalling 1533 patients were finally included. A total number of 288 patients died, 98 of whom in the TEG- or ROTEM-guided cohorts (i.e., intervention groups). A 36% reduction of death was observed in the intervention groups (relative risk, 0.641; 95% CI 0.517-0.795; P&lt;0.001). Our results show that VET-guided management is effective to reduce mortality compared to conventional management with CCTs. Except for mortality, all others endpoints were heterogeneous across the studies. This emphasize the need of scheduling new and well-designed trials, aimed to better define the optimal strategy for TIC management.

Enhanced microvascular function in the cutaneous circulation with platelet inhibition is not related to alterations in blood viscoelastic properties

Platelet inhibition with aspirin and/or clopidogrel are part of a comprehensive strategy for the primary and secondary prevention of cardiovascular disease, respectively. In the cutaneous microcirculation, treatment of clopidogrel (CLO) but not aspirin (ASA) increases cutaneous microvascular relaxation in response to reactive hyperemia. CLO is mechanistically distinct from ASA in that it works through inhibiting the platelet P2Y12 receptor and may change blood viscosity and thus the shear stimulus on the microcirculation. In this study, we sought to determine if platelet inhibition with CLO changes whole blood viscoelastic properties and is related to increased microvascular function. Nine middle‐aged healthy subjects (5 men, 4 women; 56 ± 1 yr) participated in a randomized, double blind, placebo‐controlled crossover experiment. Treatment phases included a sucrose placebo, CLO (75 mg; Bristol‐Myers Squibb), and ASA (81 mg; Bayer) for 7–10 days with a two week washout period between each treatment. On the final day of treatment, laser Doppler flux (LDF) was measured during a standardized 5 minutes reactive hyperemia protocol and area under the curve (AUC) and total hyperemic response (THR) were calculated and normalized to maximal cutaneous vascular conductance (%CVCmax: 43°C and 28 mM sodium nitroprusside). Blood viscoelasticity was measured using a Vilastic‐3 viscoelasticity analyzer at 2 Hz across a physiologically relevant shear rate range of 25 to 1000 s−1. Blood temperature was maintained at time of draw using a heat exchanger. CLO and ASA did not change hematocrit relative to the placebo control (41.6 ± 0.9, 41.9 ± 0.6, and 41.5 ± 0.7 % respectively). AUC and THR increased in the CLO trial (AUC = 3783 ± 342, THR = 2306 ± 266 %CVCmax * s; P&lt;0.0001 vs. placebo) but there was no difference between ASA (AUC = 3101 ± 325, THR = 1695 ± 197 %CVCmax * s) and placebo (AUC = 3000 ± 283, THR = 1675 ± 170 %CVCmax * s, P&gt;0.05) Apparent kinematic viscosity and elasticity was unchanged in either CLO or ASA treatment relative to placebo across the entire range measured when normalized to a hematocrit of 45 %. 7–10 days of CLO or ASA does not change hematocrit or blood viscoelastic properties in healthy humans and is not related to functional measures of microvascular function (p&gt;0.05). Improvements in cutaneous microvascular function by CLO is not a result of shear‐stress induced vasodilation, further indicating that CLO may alter sensory nervous activity and/or endothelium‐derived hyperpolarizing factor mechanisms.Support or Funding InformationNIH R01 HL093238‐07

System Identification of TEG Themostatic System

Thrombelastograph device (TEG) is a measuring instrument of blood viscoelastic properties during coagulation. The measuring temperature of TEG is fixed at 37oC while in some surgery cases, lower temperature surroundings may be adopted. Therefore a new type of TEG with a controllable themostatic system has been designed to mimic various temperature surroundings in surgery. In this paper, a small-sized high accuracy thermostatic system for TEG was designed and its system identification was built to facilitate the development of control strategy. ARX model was supposed to analyze the system identification of the thermostatic system by Matlab System Identification Toolbox. Residual analysis method was adopted to verify the identified model. The results showed that the simulation data of ARX model was consistence with the measured data (matching degree was about 93%). Transfer function of the system can be applied to develop its control strategy.

Analysis of the Effect of Magnetostimulation on Viscoelastic Properties of Blood in Patients with Lasting Pain

The aim of the current work was to analyze the in uence of alternating magnetic eld on the viscoelastic properties of blood in vivo in patients with lasting pain problems. Oscillatory techniques, also called the dynamic mechanical analysis, have been used in the current work to study the viscoelastic properties of blood. The blood samples were collected from patients of a neurological ward complaining about spinal cord and lower limbs pain. Altogether 25 patients took part in the study. A blood sample was collected from each patient twice: before the magnetostimulation and after ve treatments. For each blood sample, the hematocrit value was measured using the standard method. Plasma viscosity and the complex whole blood viscosity were measured by means of a rotary-oscillating rheometer Contraves LS40. Magnetic eld was generated by the instrument Viofor JPS and the magnetostimulation treatments were performed using di erent programs. The analysis of the results included estimation of the hematocrit value, plasma viscosity, complex whole blood viscosity and its components: viscous and elastic viscosity at four chosen amplitudes of the shear rate as a function of the applied treatment program. The results obtained in the study suggest that rheological properties of blood change depending on the applied magnetostimulation program.

Haematological Performances of Carbon Coated PTFE by Plasma-Based Deposition

Materials in contact with tissue and biological fluids affect cell reaction that could eventually lead to clinical complications (i.e. thrombosis, restenosis). Improving the biological performances of the materials used for biomedical applications is the main goal of this study. In particular, cardiovascular devices require excellent haemo- and biocompatibility properties. PTFE is currently the main material used for vascular prostheses. After long contact periods with blood, clinical complications leading to thrombosis and restenosis are often reported. Improving the haematological performances of PTFE could significantly increase its life-time and decrease long-term complications. However, inadequately engineered surfaces could trigger the coagulation cascade with the formation of a clot, the first step towards a thrombosis. Plasma carbon-based coatings with varying nitrogen contents deposited on PTFE have been studied as promising coating to improve the haematological performances of PTFE implants. In this work, several techniques were applied to study the viscoelastic properties of blood after contact with virgin and treated PTFE as well as the presence and the clot morphology eventually formed onto the surfaces. The chemical composition of the surfaces was analysed with XPS and FTIR.

Haematological Performances of Carbon Coated PTFE by Plasma-Based Deposition

Materials in contact with tissue and biological fluids affect cell reaction that could eventually lead to clinical complications (i.e. thrombosis, restenosis). Improving the biological performances of the materials used for biomedical applications is the main goal of this study. In particular, cardiovascular devices require excellent haemo- and biocompatibility properties. PTFE is currently the main material used for vascular prostheses. After long contact periods with blood, clinical complications leading to thrombosis and restenosis are often reported. Improving the haematological performances of PTFE could significantly increase its life-time and decrease long-term complications. However, inadequately engineered surfaces could trigger the coagulation cascade with the formation of a clot, the first step towards a thrombosis. Plasma carbon-based coatings with varying nitrogen contents deposited on PTFE have been studied as promising coating to improve the haematological performances of PTFE implants. In this work, several techniques were applied to study the viscoelastic properties of blood after contact with virgin and treated PTFE as well as the presence and the clot morphology eventually formed onto the surfaces. The chemical composition of the surfaces was analysed with XPS and FTIR.

Perioperative coagulation profile in living liver donors as assessed by rotational thromboelastometry

Transient postoperative coagulation abnormalities frequently occur in living liver donors, particularly after right liver resection. Usually, this coagulopathy is diagnosed by alterations in conventional coagulation tests (CCTs) such as the international normalized ratio (INR) of the prothrombin time. However, recent studies using other methods of coagulation monitoring have suggested that postoperative hypercoagulability may also occur in living donors. The rotational thromboelastometry (ROTEM) system is a coagulation monitor based on the viscoelastic properties of blood. The use of ROTEM for perioperative coagulation monitoring in the setting of living liver donors has not been reported. We evaluated the perioperative coagulation profile as assessed by ROTEM in 16 consecutive donors who underwent either right or left liver resection at our institution. ROTEM analysis and CCTs were performed at the baseline (before skin incision) and on postoperative days 1 and 3. According to the CCTs, hypocoagulability was revealed in all but 1 (left liver) donor. The INR was highest on postoperative day 1 [median = 1.67 (interquartile range = 1.37-1.8)]. In contrast, all donors had a normal coagulation profile as assessed by the ROTEM system throughout the study period. In conclusion, this study showed the disagreement between the CCTs and the ROTEM system, as no significant coagulation abnormalities could be revealed with the latter method during the study period. Further studies are needed to confirm the role of the ROTEM system as a perioperative coagulation monitor in this setting and ultimately its influence on the outcome of living donors.

Evaluation of coagulation stages of hemorrhaged swine: comparison of thromboelastography and rotational elastometry

Thromboelastography (TEG) or rotational thromboelastometry (ROTEM) assesses blood viscoelastic properties and clotting kinetics that can be measured by Haemoscope TEG and Pentapharm ROTEM devices using slightly different methodologies. These devices were compared by measuring blood samples associated with various degrees of coagulopathy. Blood samples, collected from swine undergoing three types of severe injury and resuscitation protocol resulting in normal, hypercoagulopathy, and hypocoagulopathy, were assessed with TEG or ROTEM before the surgical procedures, and after injury, fluid resuscitation, and simulated hospital phase. Standard clotting parameters were compared by Student's t-test at a significance of a P value less than 0.05. Regression analysis indicated a positive correlation between TEG and ROTEM for reaction time (R), clotting rate (K), and maximum amplitude (Ma) parameters. With samples of normal coagulation, R (440 +/- 136 vs. 391 +/- 73 s), K (99 +/- 39 vs. 81 +/- 20 s), and Ma (74 +/- 4 vs. 69 +/- 5 mm) were higher, whereas (alpha) (68 +/- 8 vs. 75 +/- 3 mm) was lower with TEG than ROTEM, respectively; a P value is less than 0.05. The magnitude of changes from baseline in hypercoagulable or hypocoagulable samples due to level of injury was equivalent with TEG and ROTEM indicating comparable use of the instruments. However, when samples were extremely hypocoagulopathic due to resuscitation fluid, the TEG values could not be readily determined. Overall, TEG readings were higher than ROTEM readings; this disparity between the two instruments was attenuated with hypercoaguable samples. Both devices yielded similar information regarding the status of coagulation related to trauma. Because of operating characteristics, the same instrument should be used for monitoring the same patient or study.

Comparative analysis of chosen hemorheological methods in a group of stroke patients

Blood viscosity is one of the most important factors determining the blood flow. In this report we describe changes in whole blood viscosity in a group of patients after stroke measured as a function of the shear rate (flow curve) and also blood visco-elastic properties measured using oscillatory methods (dynamical mechanical analysis). The principle of the latter method is based on the measurement of the amplitude and phase of the sample oscillations driven by controlled harmonic strain. All measurements were performed by means of a rotary-oscillatory rheometer Contraves LS-40.

Development of standard tests to examine viscoelastic properties of blood of experimental animals for pediatric mechanical support device evaluation.

We investigated the applicability of measuring the viscoelasticity of bovine, ovine, and porcine whole blood for the evaluation of sublethal damage to red blood cells (RBCs). An increase in blood viscosity and elasticity without changes in hematocrit and plasma viscosity would signify a decrease in RBC deformability. Blood viscoelasticity was assessed using a Vilastic Scientific viscoelastometer. Due to the natural absence of RBC aggregation and small RBC size in normal bovine and ovine blood, viscoelastic properties are less readily detected. However, we found that adjustment of blood hematocrit to a standard level of 40-50% allows for sensitive assessment of viscoelasticity in these blood types demonstrating a marked non-Newtonian behavior mostly related to RBC deformability. Porcine blood showed a pronounced non-Newtonian behavior at all tested hematocrit values, which makes it rheologically comparable to human blood. Both viscosity and elasticity were elevated after blood exposure to a uniform mechanical stress. RBCs rigidified by heat exposure demonstrated a loss of viscoelasticity dependence on shear rate. Measurements of blood viscoelasticity can be meaningful in bovine, ovine, and, especially, porcine blood, and can be used for evaluation of sublethal blood damage during in vitro and animal trials of heart-assist devices.