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At least 649 records · Page 36Linked to original sources
PubMed1999

Near-site monitoring of the antiplatelet drug abciximab using the Hemodyne analyzer and modified thrombelastograph.

OBJECTIVE: This investigation examines the hypothesis that the antiplatelet effect of abciximab and its reversal can be monitored using the Hemodyne (Hemodyne, Inc, Midlothian, VA) analyzer and modified Thrombelastograph (Haemoscope, Skokie, IL). DESIGN: In vitro dose-response and reversal study. SETTING: Anesthesia Research (Dallas, TX) and Special Studies Coagulation Laboratories (Washington, DC). PARTICIPANTS: Nine healthy volunteers. INTERVENTIONS: The addition of increasing concentrations of abciximab, 0 to 10 microg/mL, and purified fibrinogen, 50 to 400 mg/dL. The reversal of abciximab, 4 microg/mL, with the addition of fresh platelet-rich plasma (PRP) sufficient to increase the platelet concentration by approximately 10%. MEASUREMENTS AND MAIN RESULTS: Platelet aggregation and platelet contractile force using the Hemodyne analyzer were used as platelet-specific measurements. The Thrombelastograph maximum amplitude (MA) for platelets (MA(PLT)) was calculated by subtracting the MA from a platelet-poor plasma (PPP) sample (MA(ppp)) determined in one thromboelastography well from that of whole-blood MA (MA(WB)) run simultaneously in the second thromboelastography well. The addition of abciximab, 0 to 10 microg/mL, resulted in significant concentration-dependent reductions in platelet aggregation (p < 0.001), platelet contractile force (p < 0.001), and MA(PLT) (p < 0.001). Platelet contractile force (p < 0.03) and MA(PLT) (p < 0.05) were significantly more responsive than MA(WB) to the effect of abciximab, 4 microg/mL, and its reversal with the addition of fresh PRP. Purified fibrinogen concentration directly correlated with thromboelastography MA (r(s) = 0.97; p < 0.001), yet had no effect on platelet contractile force. The addition of abciximab had no measurable influence on the MA(ppp). CONCLUSION: This in vitro study suggests that the Hemodyne analyzer and modified Thrombelastograph might be clinically useful methods to monitor the platelet inhibitory effects of agents such as abciximab.

Abciximab↗
PubMed1999

Sonoclot coagulation analysis: a study of test variability.

OBJECTIVE: To test the reproducibility of Sonoclot coagulation analysis (SCA; Sienco Inc, Morrison, CO). The authors wished to determine if the mix/release of the preloaded celite activator in standard Sono-cuvettes could be responsible for the high variation coefficients for SCA parameters with citrated whole blood and if citrated whole blood is optimal for SCA. DESIGN: A prospective trial. SETTING: A large academic teaching medical center. PARTICIPANTS: Eight healthy volunteers. INTERVENTIONS: Repeated blood sampling was performed through indwelling radial artery catheters. Seven different Sonoclot analyzers were used to test seven different types of analysis procedures in the volunteers, involving activators of different types and amounts and in different forms, and the use of citrated or native whole blood. MEASUREMENTS AND MAIN RESULTS: Two-way and one-way ANOVA, variance, variance analysis, and Tukey's test were used to evaluate differences in SCA methods and volunteer influence. A high variance, with SDs up to 200% of the median values of the SCA parameters with recalcified citrated blood and the standard Sono-cuvette, was confirmed. SCA with native blood and/or the use of other types of preloaded activators, ie, kaolin, significantly (p < 0.05) reduced this variance. Repeated SCAs further reduced the variance to 10% to 35% of the variance for a single analysis (standard cuvette and native blood). CONCLUSION: Improvement of the activator in the Sonocuvette, use of native whole blood, and repeated Sonoclot analyses reduced the previously reported high variability of this instrument.

Adult↗
PubMed1999

Coagulation tests during cardiopulmonary bypass correlate with blood loss in children undergoing cardiac surgery.

OBJECTIVES: To examine whether coagulation tests, sampled before and during cardiopulmonary bypass (CPB), are related to blood loss and blood product transfusion requirements, and to determine what test value(s) provide the best sensitivity and specificity for prediction of excessive hemorrhage. DESIGN: Prospective. SETTING: University-affiliated, pediatric medical center. PARTICIPANTS: Four hundred ninety-four children. INTERVENTIONS: Coagulation tests. MEASUREMENTS AND MAIN RESULTS: Demographic, coagulation test, blood loss, and transfusion data were noted in consecutive children undergoing cardiac surgery. Laboratory tests included hematocrit (Hct), prothrombin time, partial thromboplastin time (PTT), platelet count, fibrinogen concentration, and thromboelastography. Stepwise linear regression analysis indicated that platelet count during CPB was the variable most significantly associated with intraoperative blood loss (in milliliters per kilogram) and 12-hour chest tube output (in milliliters per kilogram). Other independent variables associated with blood loss were thromboelastography maximum amplitude (MA) during CPB, preoperative PTT, preoperative Hct, and preoperative thromboelastography angle and shear modulus values. Thromboelastography MA during CPB was the only variable associated with total products transfused (in milliliters per kilogram). Of all tests studied, platelet count during CPB (< or = 108,000/microL) provided the maximum sensitivity (83%) and specificity (58%) for prediction of excessive blood loss (receiver operating characteristic analysis). Blood loss was inversely related to patient age; neonates received the most donor units (median, 8 units; range, 6 to 10 units). CONCLUSIONS: During cardiac surgery, coagulation tests (including thromboelastography) drawn pre-CPB and during CPB are useful to identify children at risk for excessive bleeding. Platelet count during CPB was the variable most significantly associated with blood loss.

Blood Coagulation Tests↗
PubMed2004

Can we rely on arterial line sampling in performing activated plasma thromboplastin time after cardiac surgery?

BACKGROUND AND OBJECTIVE: Arterial catheters are routinely used to sample blood for clotting studies in most cardiothoracic intensive care units. The clotting profile in surgical bleeding after cardiac surgery influences further management. Aspiration and discard of a certain amount of blood from the line, prior to sampling, are assumed to clear heparin contamination. We have investigated this assumption through analysis of the clotting profile by simultaneous arterial line and peripheral venous samples. METHODS: The morning following cardiac surgery, simultaneous arterial line and peripheral venous blood samples were taken for activated plasma thromboplastin time (APTT) ratio and international normalized ratio (INR) in 49 randomly selected patients. Also, a thromboelastogram analysis (TEG) (n = 7) was made. A survey of 22 UK cardiothoracic intensive care units was carried out to determine the practice for the withdrawal of blood for clotting studies. RESULTS: The median arterial APTT ratio value was 1.32 +/- 0.52 as compared to the median peripheral APTT ratio value which was 1.1 +/- 0.24 (P < 0.001). INR values were statistically similar by both routes. Heparin contamination was confirmed by TEG which revealed that the R-value for arterial catheter blood samples without heparinase in the cup was higher (406.00 +/- 64.44 s) compared with the value for arterial samples with heparinase in the cup (318.28 +/- 47.26s, P < 0.05). The survey of 22 UK cardiothoracic intensive care units showed that heparinized arterial lines were by far the commonest ports used for blood withdrawal for the measurement of APTT ratio results. CONCLUSIONS: Samples withdrawn from heparinized arterial lines cannot be relied upon for APTT ratio results.

Blood Coagulation Tests↗
PubMed2006

Just scratching the surface: varied coagulation effects of polymer containers on TEG variables.

BACKGROUND AND OBJECTIVE: Different types of polymer surfaces affect the activation of platelets and coagulation pathway containers depending on their surface qualities. Importantly, this could produce variability of coagulation results obtained with thrombelastographical analysis. We assessed the effects of blood storage on thrombelastograph, TEG, variables using polypropylene and polycarbonate containers. METHODS: An in vitro experiment was performed, with eight volunteers in each limb. Fresh whole blood was stored in polypropylene or polycarbonate tubes prior to TEGanalysis, to assess the role of these plastics in the TEG results obtained. RESULTS: The polycarbonate tubes displayed slower onset of coagulation and greater variability of data for all four basic TEG variables (r-time, k-time, alpha-angle and maximum amplitude, P < 0.05). Polycarbonate results fell outside manufacturer reference ranges. CONCLUSIONS: It is likely that this is due to the altered surface properties and charge effects of the containers affecting proteins and platelets differently. Caution should be used in choosing which containers are used for storage of fresh blood prior to coagulation assessment, as variable results will follow where different types of plastic containers are employed.

Blood Coagulation↗
PubMed2006

The haemodilution enhanced onset of coagulation as measured by the thrombelastogram is transient.

BACKGROUND AND OBJECTIVE: Crystalloid haemodilution has been widely found to enhance coagulation onset, but the duration of this effect has never been documented. METHODS: Twelve healthy, consenting volunteers had a rapid infusion of 14 mL kg-1 of normal (0.9%) saline. Blood samples were taken, prior to (control), and immediately after (30 min) the rapid saline infusion was completed (30 min). They were then repeated at regular intervals up to 120 min. Haematocrit/platelet counts were taken to determine the degree of dilution and thrombelastograms, with and without platelet antagonists (ReoPro, Abciximab), were measured in all samples. Antithrombin levels were selectively measured. RESULTS: The haematocrit and platelet count showed a rapid dilutional decrease at 30 min (mean of -12.2% and -14.4%, respectively), with values returning towards baseline within 15 min after finishing the infusion. There was a significantly faster onset of coagulation (decrease in r-time) in the post-infusion sample (30 min) compared to control (P<0.05), again returning towards normal as the dilution effect was reversed. Similar thrombelastograms findings were evident in the plasma factor only group (platelets inhibited by ReoPro). Antithrombin levels changed in keeping with the haemodilution effect (P<0.0001). There was a linear relationship between antithrombin and thrombelastograms r-time (P=0.012). CONCLUSION: The faster onset of coagulation brought on by haemodilution return towards normal as the dilutional effect is reversed. This effect is mediated through plasma clotting factors. Of interest is the significant inverse correlation of the onset of coagulation increasing as the antithrombin levels decreased with dilution.

Blood Coagulation↗
PubMedDate not supplied

Oligochitosan derivatives bearing electron-deficient aromatic rings for adsorption of amitriptyline: implications for drug detoxification.

The objective of this work is the synthesis of water-soluble oligochitosan derivatives with electron deficient aromatic rings for selective and rapid adsorption of amitriptyline through pi-pi complexation. Oligochitosan was chemically modified under homogeneous conditions in dimethyl sulfoxide (DMSO). (1)H NMR, FT-IR, and MALDI-TOF were employed in characterization, confirming that the electron deficient aromatic rings were chemically attached to the backbone of oligochitosan. Thromboelastography (TEG) revealed functionalized oligochitosan derivatives did not affect blood clotting. (1)H NMR was also utilized to observe the aromatic-aromatic interaction between electron deficient aromatic rings on oligochitosan and electron rich aromatic rings in amitriptyline. The chemical shift variation of aromatic protons in oligochitosan derivatives was followed to monitor the aromatic-aromatic interaction. Upfield shift of aromatic protons on benzenesulfonyl and dinitrobenzenesulfonyl groups was observed upon the addition of amitriptyline, supporting the formation of pi-pi complexes through aromatic-aromatic interactions. Dinitrobenzenesulfonyl rings show a larger variation in chemical shift due to the presence of the electron deficient nitro groups.

Adsorption↗
PubMed2006

Surface modification of silica core-shell nanocapsules: biomedical implications.

In this article we present the synthesis of oil core silica shell nanocapsules with different shell thicknesses. The surface of the nanocapsules was modified with polyethyleoxide (PEO) and succinic anhydride. Two biomedical tests were then used to study the biocompatibility properties of these nanocapsules with different surface treatments, hemolysis and thromboelastography (TEG). PEO surface modification greatly reduced the damaging interactions of nanocapsules with red blood cells (RBCs) and platelets and attenuated particle size effects. It was found that the blood toxicity of charged particles increased with the acid strength on the surface. Experiments toward the assessment of detoxification of these nanocapsules in model drug overdose concentrations are currently underway.

Animals↗
PubMed2006

Oxide hemostatic activity.

The tunable in vitro blood clotting activity of high-surface-area hemostatic bioactive glass is evaluated by Thromboelastograph, a clinical instrument for quantifying changes in blood during coagulation. The hemostatic trends associated with hemostatic bioactive glass and a new preparation of spherical hemostatic bioactive glass, along with similar Si- and Ca-containing oxides, are described and related to Si:Ca ratios, Ca2+ availability and coordination environment, porosity, DeltaHHydration, and surface area. Hemostatic bioactive glass is a new material with an excellent efficacy for inducing hemostasis and is chemically distinct from the traditional bioglass employed for bone growth.

Blood Coagulation↗
PubMed2006

Blood compatible carbon nanotubes--nano-based neoproteoglycans.

Although nanotechnology has provided a rich variety of nanomaterials (1-100 nm) for in vivo medical applications, the blood compatibility of all these nanobiomaterials is still largely unexamined. Here, we report the preparation of blood-compatible carbon nanotubes (CNTs) that potentially represent the building blocks for nanodevices having in vivo applications. Activated partial thromboplastin time (APTT) and thromboelastography (TEG) studies prove that heparinization can significantly enhance the blood compatibility of nanomaterials.

Biocompatible Materials↗
PubMed1999

In vitro effects of propofol on blood coagulability and fibrinolysis by the use of thromboelastograph technique.

BACKGROUND: To investigate the in vitro effects of propofol on blood coagulability and fibrinolysis by the use of thromboelastograph (TEG) technique. METHODS: The blood samples, obtained from 14 healthy volunteers, were divided into two groups: propofol (n = 7) and intralipid (n = 7), and 360 microliters volumes of whole blood were incubated with 2 microliters of 1% propofol and with its solvent intralipid, respectively. The incubated sample was then used for TEG measurements. RESULTS: The maximum amplitude (MA), which reflects coagulability, in the intralipid group significantly increased by about 7% and 16% compared to the control and propofol groups, respectively (P < 0.05), whereas the MA in the propofol group did not change. The fibrinolytic rate (FR) in the propofol group significantly increased by about 170% and 210% compared to the control and intralipid groups, respectively (P < 0.05), whereas the FR in the intralipid group did not change. CONCLUSIONS: Propofol, per se, has at the concentration of 55.6 micrograms.ml-1 an in vitro accelerative effect on blood fibrinolysis detected by TEG.

Anesthetics, Intravenous↗
PubMed2003

The effects of hydroxyethyl starch solutions on thromboelastography in preoperative male patients.

BACKGROUND: Hydroxyethyl starches (HES) have been shown to decrease clot strength and to increase coagulation times assessed by thromboelastography (TEG). HES with minimal anticoagulant side-effects is beneficial for plasma volume expansion in the perioperative setting. A comparison of the in vivo effects of high, middle and low molecular weight HES solutions on TEG variables has not been performed so far. METHODS: Blood was obtained before and after intravenous infusion (10 ml kg-1) of either saline, HES 70/0.5/4 (molecular weight in kDa/degree of substitution/C2:C6 ratio), HES 130/0.4/9, HES 200/0.6/9.4, or HES 450/0.7/4.6 in 50 otherwise healthy patients. Thromboelastography was performed in 360 micro l of 1% celite activated citrated whole blood after recalcification. RESULTS: HES 450/0.7/4.6 prolonged reaction time indicating impairment of the plasmatic coagulation system. TEG parameters indicative for platelet function, including angle alpha, maximum amplitude and coagulation time, deteriorated after infusion of HES 450/0.7/4.6 and HES 70/0.5/4. HES 200/0.6/9.4 and HES 130/0.4/9 impaired platelet contribution to hemostasis only partially, decreasing two or one TEG platelet parameters, respectively. CONCLUSION: Infusion of HES 450/0.7/4.6 compromises TEG parameters more than the other solutions tested, whereas HES 130/0.4/9 has the smallest effect. Further outcome-related studies are needed in order to assess the clinical relevance of our findings.

Adult↗