Coagulation tests predict bleeding after cardiopulmonary bypass

To determine the accuracy of coagulation profile laboratory tests, thromboelastography, and Sonoclot (SCT) values for predicting microvascular bleeding after cardiopulmonary bypass (CPB). A prospective, blinded trial. A large academic medical center. Eighty-two adult patients undergoing elective cardiac surgery. Ten minutes after CPB, thromboelastography, SCT, and coagulation profile tests (bleeding time, prothrombin time, activated partial thromboplastin time, fibrinogen, fibrin split products, platelet count, mean platelet volume, and platelet hematocrit) were determined from a whole blood sample taken from an existing arterial catheter. Patients were subjectively defined as “bleeders” or “non-bleeders” by blinded clinical observers. Preoperative baseline tests were also obtained.

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Thirty of the 82 patients (36.6%) were characterized as bleeders. Coagulation profile tests had the best correlation with intraoperative and postoperative blood loss. The specificity, sensitivity, and negative and positive predictive values were determined by receiver operating characteristic analysis, and the test values that differentiated normal from abnormal (bleeding) patients were determined. The coagulation profile laboratory tests had the greatest maximal sensitivity and specificity for predicting bleeding. These predictive values were outside the normal range for these laboratory tests. The thromboelastography values that produced maximal sensitivity and specificity were in the normal range for that test. Contrary to previous studies, coagulation profile tests had the greatest sensitivity and specificity to differentiate patients with excessive bleeding (abnormal) from those without excessive bleeding (normal) after CPB. Therefore, these tests should be used to guide transfusion therapy in patients who have excessive bleeding after CPB.     

Impact of Sonoclot hemostasis analysis after cardiopulmonary bypass on postoperative hemorrhage in cardiac surgery

Purpose The Sonoclot Analyzer provides a functional test of whole blood coagulation by measuring the viscous property of the blood sample. In this study, we used a modified Sonoclot assay, using cuvettes with a glass bead activator containing heparinase, and compared the Sonoclot data before and after cardiopulmonary bypass (CPB) to assess the usefulness in predicting postoperative hemorrhage. Methods In 41 cardiac surgery patients, Sonoclot data were obtained immediately after heparin administration (pre-bypass) and just before protamine administration (post-bypass). Excessive bleeding was defined as chest tube drainage greater than 2 ml·kg⁻¹·h⁻¹ in 1 h during the first 4 h after surgery. Results There were no significant differences in Sonoclot values before and after CPB in patients with acceptable bleeding (n = 29). In patients with excessive bleeding (n = 12), Sonoclot variables reflecting fibrin formation (activated clotting time [ACT], rate of fibrin formation [clot rate], and peak clot signal) were preserved after CPB; however, the variables reflecting platelet-fibrin interaction (time to peak, peak angle, and clot retraction rate) were significantly different from their respective pre-bypass values. Sonoclot analysis showed impairment of clot maturation after CPB in patients with excessive postoperative bleeding. Conclusion Our results suggest that abnormal postoperative hemorrhage can be predicted by Sonoclot analysis with a new glass bead-activated heparinase test performed after CPB.     

Monitoring of blood coagulation in perioperative care

Coagulation disorders often occur perioperatively and monitoring of blood coagulation should be fast and adequate to treat these disorders to protect patients from massive bleeding. Control of hemostasis is one of the main issues in major surgeries. Coagulation test results from a central laboratory may delay making such a perioperative decision. Recently, point-of-care monitoring (POCM), which is able to examine coagulation disorder in an operation theater with short waiting time, has become important. Both prothrombin time (PT) and activated clotting time (ACT) are very useful and popular, but also criticized because they can be monitored only until fibrin formation. On the other hand, viscoelastic monitorings of whole blood, are able to estimate fibrin formation, clot fixation, platelet function and fibrinolysis. In this review article, among variable perioperative POCMs of blood coagulation, three thromboelastographic monitorings, such as TEG ROTEM, and Sonoclot as well as PT and ACT, are described along with their utilities and limits to examine perioperative coagulation.     

Thrombelastograph (TEG) analysis of platelet gel formed with different thrombin concentrations

Autologous blood transfusion is the safest and most successful way to decrease transfusion-related risks such as postoperative infections, allo-immunization, and short- and long-term immunosuppression. In addition, these fibrin sealants are known to provide coagulation support at the surgical site and act as an adjunct to the control of postoperative bleeding. The physical formation of autologous platelet fibrin gel clot is dependent on both the common pathway of the coagulation cascade and platelet activation. Platelet gel can help provide control of intraoperative and postoperative bleeding. The Thrombelastograph Hemostasis Analyzer (TEG) measures the viscoelastic properties of a clot as it forms. Based on the information that the TEG provides, it promises to be a good choice for point of care measurement of the integrity of thrombus formed by platelet gels. Bovine blood from a single donor was sequestered into platelet-rich plasma and was made into platelet gel using calcium and three different concentrations of thrombin. The platelet gel samples were then analyzed with the TEG analyzer. The results for MA, tMA, CI, and angle were recorded and statistical analysis was performed to accept or reject the null hypothesis, which is: There is no difference between TEG parameters when analyzing platelet gels formed with calcium chloride, platelet-rich plasma and three different concentrations of thrombin A one-way analysis of variance test was performed between thrombin concentrations for MA (p = 0.19), tMA (p = 0.443), CI (p = 0.257), and angle (p = 0.323). The results showed that thrombin concentration did not affect the MA, tMA, CI, or angle as measured by the TEG analyzer. The null hypothesis was accepted. Based on a one-way analysis of variance test for MA, tMA, CI, and angle there was no significant statistical difference for the TEG samples in this experiment as reported with a 95% confidence interval.     

Thrombelastography. Present and future perspectives in clinical practice

Thrombelastography (TEG) is a method for evaluating the viscoelastic properties of the blood clot, from its formation to its lysis. All major surgeries may be associated with massive blood loss, with blood component transfusion therapy often becoming mandatory. The clinician's goal is thus to optimize and possibly minimize blood components usage. To this end, TEG allows for a qualitative and dynamic analysis of the specific blood clotting process, from clot formation through its lysis, highlighting alterations at every single step in the cascade. With TEG is thus possible to know if bleeding is due to a failure to provide adequate surgical hemostasis, if there is platelet dysfunction, or to detect anomalies in coagulation proteases or their inhibitors, or if the blood loss is associated to early, excessive fibrinolysis. The theoretical advantages of TEG are the ease of performing the test, the fast sample reading times (now 30 minutes) and the informative RESULTS:     

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.     

Sonoclot凝血和血小板功能分析仪监测肝移植术中凝血功能变化的应用

目的 探讨肝移植术中凝血功能的变化和Sonoclot凝血及血小板功能分析仪(sonoct coagution & piatelet function analgzer,SCA)在肝移植术中的应用.方法 24例择期肝移植手术患者全部采用原位经典非转流手术方法.于麻醉诱导前(TO)、手术开始后60 min(T1),无肝期30 min(T2)、新肝期30 min(T3)、新肝期120 min(T4)和术毕(T5)时分别采集桡动脉血检测,硅燥土激活的全血血栓弹性描记图(thrombelastography,TEG),指标包括R值、K值、Alpha角和MA值;玻璃珠激活的全血SCA,指标包括ACT、CR和PF值;常规凝血指标包括PT、APTT、INR、Fbg和Plt.结果 (1)SCA和TEG诊断凝血因子缺乏、纤维蛋白凝胶形成速度和血小板功能(都正常或者都异常)的Kappa值分别是0.371(P<0.05)、0.363(P<0.05)、0.438(P<0.05).gbACT与R、CR与α角、PF与MA呈正相关(r=0.790,P<0.05;r=0.766,P<0.05;r=0.502,P<0.05),CR与K呈负相关(r=-0.588,P<0.05).(2)与T0时比较,T3～T5时PT、INR、gbACT及R延长和FBG、CR、α及MA降低(P<0.05),T1～T5时APTT、T3时K延长(P<0.05),T2～T4时PF降低.结论SCA能够准确地监测肝移植术中凝血功能的变化.     

Does Hemodilution by the Crystalloid Priming Solution Derange the Efficacy of Anticoagulation During Cardiopulmonary Bypass?

BACKGROUND AND AIM: Recent studies suggest the development of a procoagulant state with hemodilution. We conducted this study to investigate the effect of hemodilution, by the priming solution in a cardiopulmonary bypass (CPB) circuit, on "point of care" coagulation assays (activated clotting time [ACT] and thromboelastography [TEG]). METHODS: Twenty patients undergoing cardiac surgery with crystalloid priming of CPB circuit were evaluated. Confounding variables arising from contact activation were eliminated by minor modifications. Ten milliliter per kilogram body weight of priming solution (lactated Ringer's) was infused via the aortic cannula. ACT and TEG were performed, both prior to and immediately after hemodilution. In case of latter, four variables, reaction time (r), coagulation time (k), maximum amplitude (MA), and clot formation rate (angle alpha), were estimated and considered for the results. To see if these results are duplicated "in vitro," prebypass blood samples from eight heparinized patients, diluted (4:1) with priming solution from the venous reservoir, were also analyzed. RESULTS: Falls in ACT, from a mean of 659.7 (+/-260.6) seconds to 251.5 (+/-103.2) seconds (p < 0.01), r time (678.1 [+/-318.1] sec to 468.7 [+/-152.7] sec) (p < 0.01), and k time (211.7 [+/-161.7] sec to 123.8 [+/-32.1] sec) (p < 0.05) on TEG were noted upon hemodilution. Angle alpha and MA increased, but were not statistically significant. Results from the in vitro study closely matched the results from our in vivo analysis. CONCLUSION: The study suggests that hemodilution by crystalloid priming solution may impair the efficacy of anticoagulation during CPB. The mechanism for this phenomenon remains to be elucidated.     

Effects of hypothermia on thrombelastography in patients undergoing cardiopulmonary bypass

Thrombelastography (TEG) correlates with postoperative chest drain output in patients undergoing cardiopulmonary bypass (CPB). In vitro incubation with heparinase allows TEG monitoring during CPB, despite heparin anticoagulation. Hypothermia impairs coagulation, but these effects cannot be assessed by standard coagulation tests performed at 37 degrees C. The aim of this study was to assess the effects of hypothermia on TEG. Therefore, we have compared normothermic and temperature-adapted TEG in 30 patients undergoing CPB. Our data showed significantly impaired reaction time (r), kinetic time (k), and angle alpha (alpha) in temperature-adapted compared with normothermic TEG. Maximum amplitude (MA), reflecting absolute clot strength, was not affected at temperatures of 33-37 degrees C. These findings indicate a decrease in the speed of clot formation, but not absolute deterioration in clot quality. Furthermore, heparinase-modified TEG indicated that there were nine cases in which heparin effects persisted after heparin reversal with protamine, providing a rational guide to protamine therapy.      

急性ANH 联合低中心静脉压对肝癌手术患者凝血功能的影响

目的：观察急性等容血液稀释（ANH）联合低中心静脉压（ANH+LCVP）在肝癌手术中对患者凝血功能的影响。 方法：40例ASA I~II级拟行肝癌切除手术患者随机均分为观察组与对照组,观察组于全麻后行ANH,入室到肝实质横断分离完成前行控制性LCVP,对照组按常规处理。记录患者术中、术后的出血量和术后因腹腔出血需再次手术的患者例数,以及不同时间点患者的血红蛋白（Hb）、红细胞压积（HCT）、血小板（PLT）、纤维蛋白原（FIB）、活化部分凝血酶时间（APTT）、凝血酶原时间（PT）、国际标准化比例（INR）,凝血时间（ACT）、血块凝结速率（CR）、血小板功能（PF）等。 结果：观察组患者术中出血量明显少于对照组（P<0.05）,而术后出血量两组间差异无统计学意义（P>0.05）,两组均无因继发性出血而再次手术的患者;观察组在采血后、肝癌切除后、恢复容量后Hb、HCT、PLT、FIB、CR、PF较术前均明显下降,APTT、PT、INR、ACT较术前均明显升高,但恢复容量后比肝癌切除前各指标均明显改善（P<0.05）;对照组患者从手术开始至结束,Hb、HCT、PLT、FIB、CR、PF呈进行性降低,APTT、PT、INR、ACT呈进行性升高;手术结束后观察组各项指标明显较对照组改善（P<0.05）。 结论：ANH+LCVP能够减少术中出血,对患者的凝血功能有一定的影响,但是不会导致异常出血,可以安全应用肝癌手术中。

     

Intraoperative coagulation was more interfered by HES 200/0.5 than normal saline in off-pump coronary artery bypass surgery

AIM: Rapid fluid administration is often necessary for anesthesiologists to maintain intravascular volume in off-pump coronary artery bypass (OPCAB) with acceptable hematocrits. Postoperative hypocoagulation involving postoperative bleeding and hypercoagulation involving graft patency were focused in previous studies but bleeding and blood transfusion are often peaked during vascular anastomoses during OPCAB. This study is designed to investigate the sequential effects of intraoperative coagulation with normal saline and hydroxyethyl starch (HES) solution by thromboelastography (TEG) and standard coagulation tests (SCT). METHODS: Twenty adult patients scheduled for OPCAB were enrolled in this study. After anesthetic induction, one group received HES 200/0.5 infusion up to 20 mL/kg and the other received 0.9% normal saline (NS) to maintain central venous pressure (CVP) and pulmonary artery occlusion pressures (PAOP). SCT and TEG were measured at T0 (baseline), T1 (after heparin 150 IU/kg, before vascular anastomoses), T2 (after protamine reversal), and T3 (24 hrs after the surgery) to compare the coagulation status. RESULTS: Baseline data were comparable in both groups. The number of patient who need blood components is higher in HES group. Dilutional hypocoagulation was shown by a significant prolongation of R time at T1 and T2 but also returned comparable at T3 in both groups. K, a-angle, CI and G remained unchanged in NS group but significantly affected in HES group. A statistically significant interaction between groups and treatments on maximal amplitude (MA) (P<0.01) with more blood loss in HES group 24 hours postoperatively (P=0.05). International Normalized Ratio (INR) increased significantly at T2 and T3 in both groups. CONCLUSION: A rapid infusion of either normal saline or HES solution to maintain intraoperative intravascular volume induce a significant diluted hypocoagulation during OPCAB. The use of HES solution has a prolonged dilutional hypocoagulation and a significant decrease of MA by specific platelet inhibition effects and more transfusion of blood components. All the above changes were not shown in standard coagulation tests.     

Effects of ultrafiltration on enoxaparin: an in vitro analysis

The use of low molecular weight heparins (LMWH) as an anticoagulant in the heparin-resistant patient poses challenges during cardiopulmonary bypass (CPB). The ultrafiltrability of LMWH has not been previously examined. The purpose of this study was to determine the effects of continuous ultrafiltration on the concentraton of a LMWH, enoxaparin. An in vitro analysis was performed using fresh whole human blood and an extracorporeal circuit containing four parallel ultrafiltrators and a cardiotomy reservoir with an integrated heat exchanger. Constant conditions included temperature (37 degrees C), flow (0.20 L-min(-1)) transmembrane pressure (200 mmHg), and hematocrit (25 +/- 2%). Samples were collected at the inlet, outlet, and ultrafiltrate line at one and three min for one control trial and again for each of the four hemoconcentrators following the bolus of enoxaparin. Coagulation measurements included a viscoelastic monitor (TEG), activated clotting time (ACT), activated partial thromboplastin time (aPTT), and quantitative analysis utilizing a membrane-based electrode for potentiometric measurement of polyanionic concentrations of enoxaparin. Enoxaparin concentration, from inlet to outlet, increased from 2.95 +/- 0.64 to 5.89 +/- 0.95 (p < .001) at 1 min and 4.24 +/- 0.49 to 7.89 +/- 0.606 (p < .001) at 3 min. Kinetic clot activity, as assessed by the TEG index, decreased from -3.8 +/- 2.5 vs. -10.5 +/- 6.0; (p < .01) pre- to postultrafiltrator samples after 3 min. ACT and aPTT results demonstrated no significant change. In conclusion, this study demonstrates enoxaparin is concentrated with the use of continuous ultrafiltration. Functional coagulation studies also indicate a concentrating effect, primarily via the TEG.     

Sonoclot analysis in cardiac surgery in dialysis-dependent patients

BACKGROUND: Dialysis-dependent patients have multiple disorders of hemostasis; however, there are no reports of viscoelastic changes during cardiac surgery in such patients. METHODS: Hemostasis in dialysis-dependent patients during cardiac operations was evaluated. Thirty patients who underwent cardiopulmonary bypass (CPB) were studied: 6 with chronic renal failure undergoing dialysis (HD group), and 24 without hemodialysis. Blood samples were obtained at four points: before sternotomy, 30 and 90 minutes after the start of CPB, and after protamine administration. RESULTS: Activated clotting time (ACT) measured with Sonoclot analyzer was significantly correlated with ACT measured traditionally (r = 0.92; p < 0.001; y = 36.1 + 0.95x). Values for ACT measured with Sonoclot analyzer as well as traditional ACT increased significantly during CPB. Values for ACT measured with Sonoclot analyzer in the HD group were significantly longer than those in the control group. Before CPB, both ACT measured with Sonoclot analyzer and traditional ACT in the HD group were significantly longer than those in the control group; however, there were no significant differences in ACT measured with Sonoclot analyzer between the groups after CPB. Clot rates and peak signal values were significantly decreased during CPB in both groups, and returned to preoperative values after protamine administration. There were no significant differences in clot rate and peak signal values between the two groups. There were no differences between the two groups in changes of time to peak. Platelet counts in the HD group were significantly higher (p < 0.05) than those in the control group. There were no differences in platelet counts after CPB between the two groups. Antithrombin III levels decreased below 50% during and after CPB. Antithrombin III in the HD group was significantly lower (p < 0.01) than those in the control group. A significant time-group interaction was observed in antithrombin III levels. CONCLUSIONS: Sonoclot signatures in HD patients showed no significant differences in viscoelastic changes compared with non-HD patients.     

The effects of aprotinin on platelet function in blood exposed to eptifibatide: an in vitro analysis

The preoperative use of platelet inhibitors has increased the risk of bleeding during cardiac surgery. Aprotinin has been shown to preserve hemostatic function in patients undergoing CPB. The purpose of this study was to investigate the effect of aprotinin on coagulation in blood exposed to eptifibatide. Freshly collected bovine blood was used in an in vitro model of extracorporeal circulation. Blood was separated into two groups: activated (60 minutes exposure to bubble oxygenation) and nonactivated. Within each group there were four subgroups: control (n = 3), eptifibatide (2.8 microg/mL, n = 3), aprotinin (250 KIU/mL, n = 3), and eptifibatide with aprotinin (2.8 microg/mL, 250 KIU/mL, n = 3). Twenty-four modified extracorporeal circuits utilizing a hard-shell venous reservoir and cardioplegia heat exchangers were used. Blood flow was maintained at a rate of 1.25 L/min for a total of 170 minutes, at 37 +/- 1 degree C. Samples were collected at 0, 20, 50, and 110 minutes with the following variables measured: thromboelastograph (TEG), activated clotting time (ACT), and hematocrit (Hct). Results demonstrated that at 110 minutes, the TEG index (TI) was decreased by four-fold in the activated group compared to the nonactivated group (-4.6 +/- 1.2 vs. 1.4 +/- 1.5, p < .05). The administration of aprotinin resulted in preservation of the TI as compared to eptifibatide-treated blood (-4.9 +/- 1.2 vs. -7.9 +/- 1.2, p < .05). Aprotinin combined with eptifibatide reduced coagulation derangements when compared to eptifibatide alone (-5.2 +/- 1.2 vs. -7.9 +/- 1.2, p < .05). In conclusion, aprotinin attenuated the platelet inhibition effect of eptifibatide during in vitro CPB, resulting in improved coagulation.     

不同年龄发绀型先心病患儿围体外循环期凝血功能的比较

Objective To investigate the changes in blood coagulation during cardiopulmonary bypass (CPB) in children of different ages undergoing open heart surgery for cyanotic congenital heart disease.Methods Sixty children with cyanotic congenital heart disease undergoing open heart surgery under CPB were divided into 3 age groups: Group A(age≤12 mort, n=25), Group B (12mon＜age≤24 mon, n= 17) and Group C (24 mon＜ age＜4 yr, n=18). Venous blood samples were taken immediately after induction of anesthesia(T1) and at 10 min after protamine administration (T2)for determination of activated coagulation time (SonACT), clot rate and platelet function (PF) using Sonoclot coagulation and platelet function analyzer-type DP2951 (Sieuco Co., USA).Results There was significant difference in SonACT, clot rate and PF at T1 among the 3 groups: the SonACT was significantly shorter in Groups B and C than in Group A, the clot rate was significantly higher in Group B than in Group C, and the PF was significantly lower in Group C than in Group A. At T2 , the SonACT was significantly prolonged in all 3 groups, the clot rate was significantly decreased in Groups A and B, and the PF was significantly decreased in Group A.Conclusion There are significant differences in blood coagulation and PF among the 3 different age groups of children with cyanotic congenital heart disease after induction of anesthesia and CPB has different effects on their blood coagulation and PF.     

Bupivacaine inhibits whole blood coagulation in vitro.

BACKGROUND AND OBJECTIVES: Epidural anesthesia decreases the risk of postoperative deep venous thrombosis in selected patients. Intravascular local anesthetic levels resulting from epidural anesthesia may contribute to this effect by impacting coagulation. We studied the effects of bupivacaine (1-10 micromol/L) on whole blood coagulation measured by thrombelastography (TEG) and activated clotting time (ACT). METHODS: We incubated whole blood with bupivacaine (1, 2, and 10 micromol/L) or Tyrode's solution (control) for 60 minutes and measured TEG and ACT clotting parameters. RESULTS: Bupivacaine (1 or 10 micromol/L) prolonged ACT when compared with control. The thromboxane A2 (TX) receptor antagonist SQ29548 also prolonged ACT significantly. The combination of SQ29548 and bupivacaine was equally effective as bupivacaine alone, compatible with the hypothesis that bupivacaine at these concentrations blocks TX signaling. Because SQ29548 + bupivacaine prolonged ACT more than did SQ29548 alone, bupivacaine likely inhibits processes in addition to TX signaling. This was evaluated further using TEG. After incubation with 2 microm bupivacaine, TEG reaction time and clot growth time increased significantly, and maximal amplitude decreased. CONCLUSIONS: Bupivacaine in clinically relevant concentrations influences whole blood clotting characteristics as measured by TEG and ACT. Thromboxane receptor antagonism increases ACT, confirming a role for TX in coagulation. Bupivacaine may also inhibit TX signaling, but seems to block additional factors as well. These findings might partly explain the beneficial effects of epidural anesthesia on postoperative thrombotic events.     

Hematological assessment of patients undergoing plasmapheresis during cardiac surgery

Methods of reducing patient exposure to homologous blood transfusions include the technique of intraoperative plasmapheresis for the production of platelet rich plasma (PRP). The present study was designed to determine the patient benefits of PRP by examining hemostatic changes in coagulation screens and viscoelastic whole blood monitoring (Thrombelastography, [TEG]). One hundred fifteen patients undergoing elective cardiac surgery were prospectively randomized into a blinded study. Sixty-three patients had 20 percent of the circulating plasma volume sequestered prior to heparinization and pheresed into PRP, which was reinfused 10 minutes following heparin reversal with protamine. The control (CTR) group of 52 patients were exposed to no sequestration procedure. Patients were followed to discharge and 112 parameters, including anthropometric, operative, and postoperative factors, were measured. There were no significant differences between patient groups in preoperative, cardiopulmonary bypass (CPB), or surgical parameters. Average PRP volume was 600+/-100 ml with a total platelet yield of 1.1 billion platelets per patient. TEG indices were determined at four distinct times during the surgical procedure. The CTR group had significantly higher pre-CPB TEG indices of 2.3+/-1.2 and 2.1+/-1.2 (mean+/-SD), vs. 1.8+/-1.5 and 1.4+/-1.7 in the PRP group (p less than .04). Following heparin reversal, pre-PRP reinfusion TEG values were similar between groups, although both groups had significantly decreased indices when compared to pre-CPB values. Thirty minutes post-PRP infusion the treatment group had significantly improved TEG recovery when compared to the CTR group, 1.0+/-1.2 vs. 0.3+/-1.7 (p less than .05).(ABSTRACT TRUNCATED AT 250 WORDS)     

Reproductibilité et interchangeabilité du Thromboélastographe®, Sonoclot® et du temps de coagulation activé (Hémochron®), en chirurgie cardiaque

PURPOSE: Despite their common use in cardiac surgery, few studies have evaluated the reproducibility of the Thromboelastograph (TEG), of the Sonoclot (SCT), and of the activated coagulation time with celite (ACT-C) or kaolin (ACT-K) measured with the Hemochron, in clinical conditions of on-site monitoring of hemostasis. This study determined the reproducibility of those measurements, and evaluated the ability of various devices to substitute for the ACT-C. METHODS: Blood samples collected from 20 volunteers and 21 patients undergoing myocardial revascularization were analyzed in the two channels of the TEG, in two SCT and four Hemochron analyzers. The overall of TEG and SCT coagulation profiles were analyzed by a computerized TEG and an experienced observer respectively. The variation rate (V%) was calculated for each variable. The ability of ACT-K and SCT to substitute for ACT-C under different clinical conditions was evaluated. RESULTS: ACT-C and ACT-K V% ranged between 5.6% and 10.8% and between 6.7% and 12.4% respectively. TEG and SCT V% ranged between 3.1% and 9.5% and between 5.8% and 33.6% respectively, according to different conditions and parameters. In volunteers and non-heparinized patients, the ACT-C and ACT-K were interchangeable. No other test can substitute for the ACT-C when patients are heparinized during cardiopulmonary bypass (CPB). CONCLUSIONS: In the clinical conditions of use, on-site hemostasis monitoring devices providing the most reproducible measurements are, in decreasing order, the TEG, the Hemochron and the SCT. In heparinized patients and during CPB, results from different tests are not interchangeable, stressing the importance of establishing appropriate instrument-specific values for monitoring anticoagulation during cardiac surgery.     

Coagulation monitoring during extracorporeal membrane oxygenation: the role of thrombelastography

Patients undergoing extracorporeal membrane oxygenation (ECMO) are at an increased risk for developing coagulopathies due to the adverse effects of extracorporeal circulation on the hemostatic mechanism. Methods of determining causative factors of bleeding diathesis are often inconsistent and non-specific. ECMO patients require aggressive transfusion therapy with autogenic blood products to stabilize and maintain hemostasis. The present study evaluated the coagulation status of newborn patients undergoing ECMO therapy, using a viscoelastic monitor (Thrombelastograph -TEG) that measures functional aspects of clot development and stabilization. Seventeen neonatal patients undergoing ECMO for severe respiratory dysfunction were entered into this study. Serial blood samples were obtained and routine coagulation assessment including fibrinogen concentration, platelet count and ionized calcium was performed. In addition, fibrin(ogen) degradation products (FDP), d-Dimers, antithrombin III and plasma free hemoglobin were measured. Transfusion indicators were established and total transfusion requirements recorded. TEG profiles were determined with the use of heparinase, an enzyme that degrades heparin but has little effect on other coagulation factors. The most commonly encountered complication was hemorrhaging which was diagnosed by laboratory and clinical assessment in 11 of 17 patients. Transfusion requirements (measured in ml/kg/ECMO hour) were the following: packed red blood cells--1.34 +/- 0.5; platelets--0.71 +/- 0.57; fresh frozen plasma--0.09 +/- 0.12; cryoprecipitate 0.05 +/- 0.05. Thrombelastograph profiles reflected hemostatic conditions that ranged from severe coagulopathies (DIC) to hypercoagulability. Interpretation of TEG profiles identified hemostatic abnormalities in 57 of 101 profiles (46.5%), with the most common etiology related to platelet dysfunction.(ABSTRACT TRUNCATED AT 250 WORDS)     

The detection of changes in heparin activity in the rabbit: a comparison of anti-xa activity,thrombelastography, activated partial thromboplastin time,and activated coagulation time

Thrombelastography (TEG) has been used to detect both exogenous and endogenous circulating heparin activity in clinical and laboratory settings. Thus, in this study I sought to compare the sensitivity of TEG, activated partial thromboplastin time (aPTT), and activated coagulation time (ACT) values with changes in anti-Xa activity after small-dose heparin administration in rabbits. Conscious rabbits (n = 11) had blood obtained from ear arteries for hematological analyses after the administration of 0, 10, 20, and 30 U/kg of IV heparin. Anti-Xa activities after the administration of 0, 10, 20, and 30 U/kg of heparin were, respectively, 38 +/- 9 mU/mL, 74 +/- 15 mU/mL, 105 +/- 14 mU/mL, and 134 +/- 17 mU/mL; all values were significantly different from each other. TEG variables (R and alpha) significantly (P < 0.05) changed between 0, 10, and 20 U/kg heparin doses, but a difference between 20 and 30 U/kg could not be discerned secondary to loss of a detectable clot. The aPTT was significantly (P < 0.05) different between 0, 20, and 30 U/kg doses. ACT values were significantly different between the 0 U/kg heparin dose and all other doses; however, there were no significant differences between the 10, 20, and 30 U/kg heparin doses. Changes in anti-Xa activity were significantly linearly related to R (r = 0.81, P < 0.0001), alpha (r = -0.85, P < 0.0001), aPTT (r = 0.74, P < 0.0001), and ACT (r = 0.41, P = 0.005). In this model of small-dose heparin administration, TEG variables were more sensitive to changes in heparin activity than aPTT and ACT. IMPLICATIONS: Changes in thrombelastography (TEG) variables more sensitively reflect changes in circulating heparin activity than activated partial thromboplastin time (aPTT) and activated coagulation time (ACT) after small-dose heparin administration in rabbits. Thus, TEG may be more helpful than aPTT and ACT in the detection of heparin in both laboratory and clinical settings wherein heparin may play a role in coagulopathy.