The influence of induced hypothermia for hemostatic function on temperature-adjusted measurements in rabbits

In hypothermic patients, a tendency to bleed may be observed even when hemostatic tests seem to be normal. Coagulation and platelet function tests are usually performed at 37 degrees C. We investigated the influence of induced hypothermia on temperature-adjusted hemostasis function testing using Sonoclot Analyzer (Sonoclot) and Thromboelastography (TEG). Anesthesia was induced and maintained with IV ketamine and fentanyl on 15 male New-Zealand White rabbits. A water blanket was used to induce hypothermia to 30 degrees C and to rewarm to 37 degrees C. Blood samples were obtained at four points: before hypothermia, at 34 degrees C, at 30 degrees C, and after rewarming. Standard coagulation tests were performed at 37 degrees C (C method), and simultaneously, real temperature hemostasis function tests (R method) were run. In Sonoclot(R), activated clotting time and time to peak increased and clot rate decreased significantly at 30 degrees C in the R method compared with those in the C method. In TEG(R), reaction time and clot formation time were prolonged and clot formation rate was diminished at 30 degrees C in the R method compared with those in the C method. Induced hypothermia delayed the coagulation cascade and reduced platelet function. During hypothermia, hemostatic measurements should be performed at real temperature to avoid overestimating patient hemostatic function based on results measured at the standard 37 degrees C. IMPLICATIONS: We investigated the influence of induced hypothermia on temperature-adjusted hemostasis function tests in rabbits using Sonoclot Analyzer and Thromboelastography. Induced hypothermia delayed the coagulation cascade and reduced platelet function. The conventional coagulation tests performed at 37 degrees C failed to detect these hypothermia-induced degradations in hemostasis performance.     

应用血小板功能分析仪PFA-100和血栓弹性描记仪评估健康孕妇和先兆子痫孕妇止血功能的比较研究

背景PFA-100是一种即时血小板功能分析仪，用于测定体外血小板血栓形成的速度，即凝血时间（closure time，CT）。该仪器可用于区域麻醉前的凝血功能评估。本次前瞻性、观察性研究旨在探讨血小板功能分析仪PFA-100和血栓弹性描记仪（thromboelastograph，TEG）对先兆子病和正常分娩者血小板功能的评价能力。本研究首先确立正常妊娠人群中PFA-100和TEG测量值的95％参考区间，然后再用PFA-100和TEG检测分娩时先兆子痫患者和正常孕妇的血小板功能状况，并进行可信区间分析和方差分析。方法常规进行患者的止血和凝血功能检查，同时测量von Willebrand因子、CT和TEG。数据以均数±标准差表示。结果先兆子痫的严重程度与CT延长呈正相关，即使在血小板计数正常的情况下也是如此。在重度先兆子痫患者中，PFA-100测得的CT值（均数±标准差为155±65秒）超过了对照组的95％参考区间（70～139秒）。相比之下，在重度先兆子痫患者中测得的TEG最大振幅（maximum amplitude，MA）（71±8mm）仍位于正常孕妇MA值的95％参考区间（64～82mm）内。结论本研究提示，与先兆子痫严重程度相关联的初期止血功能损害可被PFA-100而不是TEG识别。     

A prospective study of thromboelastography (TEG) and filter life during continuous veno-venous hemofiltration

Anticoagulants are commonly used to prolong circuit life during continuous hemofiltration. However, a clear correlation between routinely performed blood coagulability tests and circuit life has not been demonstrated. This lack of correlation may derive from the limited ability of such tests to describe the likelihood of in vivo clotting. We hypothesized that thromboelastography (TEG), which derives its variables from a closer reproduction of in vivo coagulation, would significantly correlate with filter life. Accordingly, we conducted a prospective pilot study of the correlation between filter life and TEG-derived variables in 21 hemofilters used in 6 critically ill patients admitted to a tertiary intensive care unit. It involved the performance of TEG during steady state anticoagulation, measurement of circuit life, and of routine coagulation variables. The results showed that the mean circuit life was 20.7+/-4.0 h despite an average aPTT of 67.7+/-12.8 s and a mean heparin dose of 472.5+/-96.2 IU/h. The mean INR was 1.4+/-1 and the mean platelet count was 118+/-16 x 10(3)/mm3. Although several TEG variables correlated with heparin dose (p < 0.03), no correlation was found between any of the routine coagulation variables or any of the TEG variables and circuit life. In conclusion, no significant correlation between TEG derived variables or routinely measured coagulation variables and circuit life could be demonstrated. These findings suggest that such tests are not useful indicators of circuit anticoagulation adequacy and that factors other than blood coagulability may play a role in circuit failure.     

The effect of graded hypothermia (36 degrees C-32 degrees C) on hemostasis in anesthetized patients without surgical trauma

The isolated effects of hypothermia on hemostasis have not been investigated in healthy humans. We cooled 16 anesthetized patients scheduled for elective intracranial surgery to 32 degrees C body core temperature and assessed prothrombin time (PT), activated partial thromboplastin time, thrombelastogram (TEG), closure time, and platelet count at 36 degrees C, 34 degrees C, and 32 degrees C body core temperature after the induction of anesthesia but before surgical intervention. Activated partial thromboplastin time, hematocrit, and closure time did not change, whereas PT and platelet count decreased during cooling. Platelet count decreased without a decrease in hematocrit; hence, a dilution by administered fluids seemed unlikely. The small decrease of platelet count is probably clinically irrelevant in patients with normal platelet count and function. The small decrease in PT indicates an alteration of the extrinsic pathway of coagulation. TEG measurements showed a delay of clot formation in temperature-adjusted measurements but showed no change if the test temperature was 37 degrees C. This indicates that hypothermia reduces plasmatic coagulation and platelet reactivity. However, the clot strength is not altered by hypothermia. All coagulation variables remained within the normal ranges. Our results may indicate that moderate short-term (4-h) hypothermia has only minor adverse effects in healthy humans. We can make no statement about the effects of hypothermia of longer duration. IMPLICATIONS: This study investigated the isolated effects of hypothermia in healthy anesthetized humans. We found only minor effects of body temperature reduction to 32 degrees C on assessed coagulation variables, indicating only minor effects in otherwise healthy humans.     

In vitro fertilization-induced alterations in coagulation and fibrinolysis as measured by thromboelastography

Supraphysiologic increases in estrogen produced by in vitro fertilization (IVF) promote the expression of hemostatic markers. Although quantitative studies of individual markers have been performed during IVF, their results are conflicting and do not reveal the qualitative effect of each marker on the overall coagulation and fibrinolytic processes. Thrombelastograph (TEG) coagulation analysis, by contrast, provides a global measure of coagulation and fibrinolysis and can indicate the relative contributions of clotting factors, fibrinogen, and platelets to each process. We studied the serum estrogen concentrations and TEG variables in 24 women at the beginning and conclusion of an IVF stimulation cycle. Serum estradiol (E(2)) concentrations (mean +/- SD) increased from 26.9 +/- 8.6 to 2098 +/- 913 pg/mL (P < 0.005) at baseline and oocyte retrieval, respectively. The measured TEG indices demonstrated alterations in coagulation rather than fibrinolysis. Although significant changes were noted in both the clot formation time and the coagulation index (P < 0.005), all TEG values remained within the normal range. In addition, an increased role of fibrinogen in promoting clot strength was observed. These findings may assist in the treatment of IVF patients who ultimately develop thromboembolic complications as a result of ovarian hyperstimulation. IMPLICATIONS. The dramatic changes in estrogen produced by in vitro fertilization therapies result in hemostatic marker alterations. Thrombelastograph coagulation analysis, which provides a global assessment of these changes, demonstrated significant alterations in two coagulation indices (clot formation time, coagulation index), although all variables remained within normal limits. The relative importance of fibrinogen versus platelets in determining clot strength was observed. No significant alterations in fibrinolysis were detected.     

Evaluation of the platelet function analyzer (PFA-100) vs. the thromboelastogram (TEG) in the parturient

BACKGROUND: The platelet function analyzer (PFA-100) is a bedside test of coagulation designed to evaluate platelet function. It measures the time required for whole blood to occlude a membrane impregnated with either epinephrine (EPI) or adenosine 5'diphosphate (ADP). The results are reported as closure time (CT-EPI or CT-ADP) in seconds. The thromboelastogram (TEG) measures whole blood clotting and the maximum amplitude (MA) correlates with platelet count and function. We wished to establish whether there is a correlation between the CT and platelet count, between the CT and MA, and between the MA and platelet count. METHODS: Platelet count, CT, and MA were measured in blood drawn from 172 healthy term parturients using the PFA-100. RESULTS: We were unable to detect a significant correlation between the CT-EPI and platelet count (r=-0.1, P=0.21), or the CT-ADP and platelet count (r=-0.02, P=0.83). We also did not find a correlation between the CT-EPI and MA (r=-0.13, P=0.12) or between the CT-ADP and MA (r=-0.11, P=0.19). However, we found a significant correlation between platelet count and MA (r=0.33, P<0.001). CONCLUSIONS: We conclude that the CT does not correlate with the platelet count or MA in the parturient, but the TEG does. Therefore the TEG may be a better tool to evaluate coagulation in the parturient with thrombocytopenia.     

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)     

Use of abciximab-modified thrombelastography in patients undergoing cardiac surgery.

Thrombelastography (TEG) is a reliable coagulation monitoring system that can guide blood product transfusion in cardiac surgery. The maximum amplitude (MA) of TEG measures clot strength, which is dependent on both fibrinogen level and platelet function. Inhibition of platelet function with abciximab-fab is suggested to permit quantitative assessment of the contribution of fibrinogen to clot strength. We hypothesized that abciximab-modified TEG permits prediction of plasma fibrinogen levels and that the difference of standard MA and abciximab-modified MA (deltaMA) is a correlate for platelet function. We correlated abciximab-modified MA with plasma fibrinogen levels and deltaMA with platelet count in patients undergoing coronary revascularization. Correlation between plasma fibrinogen levels and abciximab-modified MA was significant (adjusted r2: 0.8; P < 0.0001). Correlation of deltaMA with platelet count was not significant when calculated in millimeters (adjusted r2: 0.04; P = 0.73). However, when deltaMA was calculated in dynes per square centimeter (deltaGMA), it correlated significantly with platelet count (adjusted r2: 0.51; P < 0.0001). We conclude that abciximab-modified TEG may therefore help to discriminate between hypofibrinogenemia and platelet dysfunction as a cause of decreased MA. IMPLICATIONS: We examined the use of abciximab-modified thrombelastography in patients undergoing cardiac surgery. Modification of thrombelastography with abciximab-fab allows prediction of fibrinogen levels, despite coagulation altered by cardiac surgery. The difference of standard maximum amplitude and abciximab-modified maximum amplitude correlates with platelet function when expressed in dynes per square centimeter.     

Celite-activated thrombelastography in children

STUDY OBJECTIVE: To quantify global coagulation and establish normal ranges for the celite-activated thrombelastograph (TEG) in healthy pediatric patients. DESIGN: Prospective observational study. SETTING: Operating suite of a university-based hospital. PATIENTS: 110 healthy pediatric patients in four age groups and 25 healthy adult patients. INTERVENTIONS: Blood sampling for the celite-activated TEG was carried out after anesthetic induction. MEASUREMENTS: TEG indices: R time (reflecting time to fibrin formation), K time and alpha angle (fibrinogen-platelet interaction), maximum amplitude (reflecting maximal clot strength, platelet and fibrinogen function), TEG index (mathematical incorporation of the prior four measurements), and percent fibrinolysis at 30 minutes, were all recorded. MAIN RESULTS: Statistically significant differences between <12-month group in angle (compared to 25-48 month group) and % fibrinolysis (compared to all other pediatric groups). Significant differences in angle between two pediatric groups and adult group, and in the TEG index between three pediatric groups and adult group (all differences p < 0.05). CONCLUSIONS: These data identify changes of small magnitude in three celite-TEG parameters in healthy children compared to adults, without implication of abnormal coagulation between groups. Changes do not seem to be consistently related to age and will be useful for clinicians using the TEG to monitor (ab) normal coagulation in pediatric patients.     

Plateletworks platelet function test compared to the thromboelastograph for prediction of postoperative outcomes

Approximately 3.5 million units of platelets are transfused in the United States each year to patients undergoing open-heart surgery with cardiopulmonary bypass (CPB). CPB is a known contributor to platelet loss and platelet dysfunction leading to disruption of hemostasis. Impaired hemostasis results in excess bleeding in 5-25% of all patients undergoing CPB. For this reason, it may be beneficial to measure platelet number and function in these patients. The purpose of this study was to compare the Plateletworks platelet function analyzer to the thromboelastograph (TEG) in predicting postoperatiave hemostatic outcomes as measured by blood product use and chest tube (CT) drainage. This study consisted of 35 adult patients undergoing cardiac surgery with cardiopulmonary bypass at Rush-Presbyterian-Saint Luke's Medical Center (RPSLMC). The Plateletworks and TEG tests were performed preoperatively, after protamine was given, and 24 hours postoperatively on all patients. Plateletworks demonstrated a statistically significant change in platelet function as shown by the adenosine diphosphate (ADP) reagent tube from the preoperative period to the removal of the aortic cross clamp (p = .011). The TEG did not demonstrate a significant change in the k-time and maximum amplitude (MA), but did show a significant change in the alpha-angle from the pre-operative to postoperatiave sample (p = .035). A correlation was found between Plateletworks collagen reagent tubes preoperatively and CT drainage (p = .048, r -0.324). No statistical correlation was established between TEG parameters and CT drainage at any time interval. TEG preoperative MA showed a correlation to receipt of blood products (p = .016). When comparing the Plateletworks to the TEG in this study, the Plateletworks system was a more useful predictor of blood product use and chest tube drainage.     

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.     

A prospective, randomized, double-blind, placebo-controlled study of the platelet and global hemostatic effects of Ganoderma lucidum (Ling-Zhi) in healthy volunteers

Ganoderma lucidum is a Chinese herbal medicine popular with cancer patients. Previous in vitro studies suggested that Ganoderma lucidum might impair hemostasis. In this prospective, randomized double-blind study, healthy volunteers received orally Ganoderma lucidum capsules 1.5 g (n = 20) or placebo (n = 20) daily for 4 wk. We monitored subjects before drug administration and at 4 and 8 wk thereafter by routine coagulation screen, fibrinogen concentration, von Willebrand ristocetin cofactor activity, platelet function analyzer PFA-100, and thrombelastography. There were no significant between-group differences and all measurements remained within the normal range. Ganoderma lucidum ingestion over 4 wk was not associated with impairment of hemostasis. IMPLICATIONS: Ingestion of Ganoderma lucidum does not cause impairment of hemostatic function in healthy volunteers, despite earlier in vitro reports that it may cause platelet inhibition and may have other antithrombotic and fibrinolytic activity. The use of Ganoderma lucidum preoperatively is unlikely to increase the risk of surgical bleeding in otherwise healthy patients.     

The kaolin-activated Thrombelastograph predicts bleeding after cardiac surgery

OBJECTIVE: The objective of this study was to determine the relationship of the kaolin-activated Thrombelastograph (TEG) with postoperative bleeding and laboratory tests of coagulation in the setting of cardiac surgery with the routine use of -aminocaproic acid. DESIGN: Prospective observational study. SETTING: An adult heart center at a tertiary referral, university hospital. PARTICIPANTS: Thirty adult cardiac surgical patients. INTERVENTIONS: The kaolin-activated TEG, platelet counts, prothrombin times, activated partial thromboplastin times, and fibrinogen levels were measured before induction of anesthesia, during cardiopulmonary bypass, and on arrival in the intensive care unit. Mediastinal and thoracostomy drainage were measured every hour for 4 hours after arrival in the intensive care unit. MEASUREMENTS AND MAIN RESULTS: Correlation and multivariate linear regression modeling were used to describe relationships among coagulation tests, TEG parameters, and early postoperative bleeding. The TEG maximum amplitude (MA) parameter correlated well with postoperative bleeding (r = -0.6, p = 0.0018), more so than platelet count (r = -0.45, p = 0.02), fibrinogen level (r = -0.40, p = 0.06), or prothrombin time (r = 0.43, p = 0.02). The receiver operating characteristic curve c-index describing MA as a predictor for postoperative bleeding is 0.78. Abnormalities in all the laboratory test results were associated with an abnormal MA. CONCLUSIONS: In conclusion, the kaolin-activated TEG is associated with early coagulopathic bleeding. It may reflect the severity of a global coagulopathy affecting both platelets and coagulation factors and be a guide to incremental prohemostatic therapy in this setting.     

Thromboelastography in elective total hip arthroplasty

BACKGROUNDHypercoagulability plays an important role in predisposing patients to venous thromboembolism (VTE) after total hip arthroplasty (THA). We used thromboelastography (TEG) to examine the coagulation status of patients undergoing THA.AIMTo examine coagulation as measured by TEG in patients undergoing THA who received standard VTE chemoprophylaxis with enoxaparin. METHODSAfter ethical approval, we performed a retrospective analysis of data collected in patients undergoing primary elective THA. We analyzed TEG data on samples performed before skin incision, intraoperatively and for 5 d postoperatively. Conventional coagulation tests were performed preoperatively and on postoperative day 5. RESULTSTwenty patients undergoing general anesthesia and 32 patients undergoing spinal anesthesia (SA) were included. TEG demonstrated a progressively hypercoagulable state postoperatively, characterized by elevated maximum amplitude. TEG also demonstrated transient intraoperative hypercoagulability in patients receiving SA. In contrast, conventional coagulation tests were normal in all patients, pre- and postoperatively, except for an increase in plasma fibrinogen day 5 postoperatively. CONCLUSIONDespite VTE prophylaxis, patients following total hip replacement remain in a hypercoagulable state as measured by both TEG and conventional tests. This group may benefit from more optimal anticoagulation and/or additional perioperative hemostatic monitoring, via TEG or otherwise.     

Intraoperative changes in blood coagulation and the effectiveness of ulinastatin during liver resection

The blood coagulation status of 16 patients undergoing liver resection was monitored by thrombelastograph (TEG). Coagulation test by TEG was performed at three different times: before and one hour after induction of anesthesia and after liver resection. The four variables such as r (reaction time), k (coagulation velocity), ma (maximum amplitude) and me (maximum elasticity) were measured. In 8 patients, Ulinastatin was not administered during the operation and FFP was transfused after the second measurement of TEG (group I). The other 8 patients were administered totally 300,000 units of Ulinastatin after induction until the second measurement of TEG, thereafter FFP was transfused (group II). The TEG showed poor preoperative coagulation state in both groups. In group I, TEG variables showed coagulopathy was exacerbated significantly during liver resection. In group II TEG variables showed no significant changes during operation. Between the two groups there were statistical differences in the TEG variables during the operation. The TEG was useful for monitoring coagulation function during liver resection. It was impossible to improve TEG data by only replacement of FFP. Ulinastatin was useful in normalizing the coagulation function and in preventing the changes in TEG measurements during liver resection.(Okida M, Masako O, Maruya H, et al.: Intraoperative changes in blood coagulation and the effectiveness of Ulinastatin during liver resection. J Anesth 5: 43–47, 1991)     

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)     

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.     

血栓弹性图评价肾移植围术期的凝血状况

目的：采用血栓弹性图（TEG）评价肾移植围术期的凝血状况，并探讨术前血液透析对凝血功能的影响，方法：38例行肾移植术病人，按术前最后一次血液透析距手术的时间分为三组，A组（16例），小于6h，B组（12例）：6－24h,C组（10例），超过24h。三组均于术前，称植肾动静脉开放后10min及术毕采静脉血检测TEG（r,k,α角，MA及CI）。结果：A组术前TEG参数中r,k值均小于正常值，α角，MA及CI值均明显增高，B组术前TEG参数均在正常值范围内，C组术前r值的平均值为6.89min，超过了正常上限值，其MA平均值为57.21mm,低于正常下限值，与C组术前r值的平均值为6.89min，超过了正常上限值，其MA平均值为57.21mm，低于正常下限值；与C组相比，A组术前r值显著降低，α角，MA及CI值均升高（P＜0．05）。B,C两组动静脉开放10min后的TEG参数与术前值相比，均表现为r值缩短，MA与CI增加（P＜0．05），三组术毕TEG参数比较无显著差异（P＞0．05）。结论：TEG提示血透后的6h内血液呈高凝状态，24h后有纤溶的倾向。移植肾动静脉开放后血液亦呈高凝状态，有潜在的血栓形成的危险性。     

Comparison of viscoelastic measures of coagulation after cardiopulmonary bypass

Postoperative hemorrhage remains a major cause of morbidity after cardiopulmonary bypass (CPB). Treatment remains empiric because of the need for immediate correction and the lack of availability of rapid intraoperative coagulation monitoring (except for ACT) at most institutions. Thrombelastography (TEG) and Sonoclot analysis (SCT) are measures of viscoelastic properties of blood which allow rapid intraoperative evaluation of coagulation factor and platelet activity as well as overall clot integrity from a single blood sample. Routine coagulation tests (RCT) including activated clotting time (ACT), prothrombin time (PT), partial thromboplastin time (PTT), fibrinogen level (FIB), and platelet count (PLT) were determined and compared to TEG and SCT to assess which best predicted clinical hemostasis after CPB. Forty-two patients prospectively felt to be at high risk for excessive post-CPB bleeding had blood obtained for RCT, TEG, and SCT analysis before systemic heparinization and 30 min after protamine administration. Nine of 42 patients had excessive chest tube drainage, but no reoperations were required. After CPB, mean values for RCT were normal, but there were abnormalities in TEG and SCT parameters that reflect platelet-fibrin interaction. Both TEG and SCT were 100% accurate in predicting bleeding in these nine patients and, overall, both tests were significantly better predictors of postoperative hemorrhage than RCT. We conclude that viscoelastic determinants of clot strength may be abnormal after CPB and that SCT and TEG are, therefore, more useful than RCT for the detection and management of coagulation defects associated with CPB.     

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.