Effect of heparin, platelets, activated platelets, platelet fragments, and hematocrit on activated clotting time

Activated clotting time (ACT) is the most commonly used laboratory test to control the heparin effect during extracorporeal techniques. The study was undertaken in order to test in vitro the influence of heparin, platelet count, hematocrit, platelet fragmentation, and platelet activation on ACT. Blood was drawn from volunteer donors into syringes containing citrate. Platelet counts and hematocrit were modified. Platelets were fragmented by sonifier or activated by collagen and adenosine diphosphate (ADP). Different heparin final concentrations were created. Increasing concentrations of heparin had a significant effect on ACT. However, it was not predictable in every case in concentrations lower than 1.0 U/ml. Platelet count generally had no significant effect on ACT. The effect of hematocrit was detectable in a group but not in single cases. Fragmented platelets significantly shortened ACT only without addition of heparin, and the effect was only partly predictable. Activation of platelets by collagen and ADP induced no significant changes. Our results show that heparin is reflected by ACT but that effect is not predictable in every specific patient. Our results also show that other variables that may be altered during extracorporeal techniques such as platelet count, hematocrit, activation, and fragmentation of platelets do not severely influence the ACT.     

Maintenance of blood heparin concentration rather than activated clotting time better preserves the coagulation system in hypothermic cardiopulmonary bypass

In cardiopulmonary bypass (CPB), despite heparin regimens in which the activated clotting time (ACT) is kept at more than 400 s, there is biochemical evidence of thrombin generation indicating activation of the coagulation system and increased fibrinolytic activity. Therefore, to reduce the coagulant activation has been one of the main issues in the improvement of CPB. The purpose of this study was to compare the heparin concentration with the ACT and to evaluate the effect of keeping higher heparin concentration on the coagulation and fibrinolytic systems during hypothermic CPB, employing moderate hypothermia (MHT) or deep hypothermic circulatory arrest (DHT). Heparin was either administered to maintain an ACT >400 s (ACT group) or to maintain a whole blood heparin concentration of 3 mg/kg (heparin group). At the lowest core temperature during CPB, the ACT and the heparinase ACT (unrelated to heparin concentration) were increased the most whereas the whole blood heparin concentration was less than half the initial concentration in both ACT groups of MHT and DHT. The thrombin-antithrombin III (TAT) content just after CPB in both MHT and DHT was significantly lower in the heparin group than in the ACT group. In conclusion, ACT does not reflect the whole blood heparin concentration during hypothermic CPB. Furthermore, maintenance of the higher heparin concentration during hypothermic CPB may suppress the activation of the coagulation system via thrombin inhibition. That effect was more remarkable in deep hypothermic CPB. Therefore, we believe that anticoagulation management during hypothermic CPB should be based on the maintenance of the higher blood heparin concentration.     

Measurement of activated clotting time in children--comparison of the Celite i-STAT ACT with the Medtronic ACT II

BACKGROUND: To evaluate a recently introduced blood-saving method for the measurement of activated clotting time (ACT), the Celite i-STAT ACT, by comparing the values obtained with those from the widely used Medtronic ACT II device. METHODS: In a prospective clinical study, we compared ACT values from the i-STAT device with the Medtronic ACT II device in 60 paediatric, interventional, cardiac catheterization procedures necessitating prophylactic heparinization. Blood samples were pair-analyzed using two i-STAT analyzers and one Medtronic ACT II device with double-tube-cartridges before and after heparinization. Data were compared using Bland-Altman bias analysis, Student's t-test and simple regression analysis. RESULTS: Bias and precision between the Medtronic ACT II and the i-STAT ACT values was -5.4 +/- 26.3. The i-STAT and Medtronic ACT II values were similar before heparinization (P = 0.22), but i-STAT ACT values became significantly longer than Medtronic ACT II values after heparinization (P = 0.021). The increase of ACT after heparinization was greater (median 86.3; range 40-187 s) in the i-STAT analyzer than in the Medtronic ACT II analyzer (median 73.0; range 19-235.5 s). Increase in ACT values was inversely affected by intraoperative haemoglobin concentration in the Medtronic ACT II analyzer (P = 0.001) but not in the i-STAT analyzer. CONCLUSION: Activated clotting times obtained from the Celite i-STAT ACT and the Medtronic ACT II demonstrated poor agreement. The technical principles are quite different and the two methods showed diverse susceptibility to intraoperative haemoglobin concentration. Users have to be aware of technique-specific ACT target ranges and their confounders, which need to be provided by the manufacturers.     

Intraoperative measurement of activated partial thromboplastin time and prothrombin time with a new compact monitor

A prospective study was conducted to evaluate a new compact portable coagulation monitor (Ciba–Corning Biotrack 512 Monitor), which enables the clinician to perform instantaneous activated partial thromboplastin time (APTT) and prothrombin time (PT). 126 patients scheduled for heparinized and nonheparinized vascular surgery, and gynaecological surgery, were included. A drop of capillary or venous whole blood was applied in disposable cartridges to successively perform APTT and PT, and the results of the tests were compared with conventional laboratory methods, performed in two different laboratories (Lab. A and B). Comparisons between Lab. A. and Lab. B. enables determination of the bias, precision, and percent of outliers (patients whose values differed more than 20%) in conventional methods. The reference value was defined as the mean of Lab. A. and Lab. B. values. For PT, there were no statistical differences between the capillary and venous samples performed with the portable monitor, and the reference value, for the bias, the precision and the proportion of outliers. For APTT, there were no statistical differences between the capillary and venous samples performed with the portable monitor, and the reference value, for the bias and the precision. The percent of outliers, however, was significantly greater with the venous sample of the compact monitor than with the reference (48 versus 22%), and even if it did not reach the statistical significance ( P = 0.07) it was also higher with the capillary sample performed with the Ciba Monitor than with the reference (33%). In conclusion the assessment of blood coagulation using this new compact monitor could be of major interest during the intraoperative period when immediate results are mandatory, even if PT is more accurate than APTT with this new method.     

Comparison of point-of-care activated clotting time systems utilized in a single pediatric institution

This study compares four different activated clotting time (ACT) point-of-care (POC) testing systems used at our institution for the management of patients undergoing heparin therapy. We evaluated these systems under identical conditions to determine their accuracy, reproducibility, ease of use, and cost. Two separate testing stations containing four ACT systems were used. The testing order was randomized for every sample and performed by two trained individuals. Samples of fresh heparinized whole blood were taken at regular intervals and distributed to each station. Each operator tested 50 samples, totaling 400 ACT tests. The ACT value was significantly affected by the type of machine used at both stations 1 and 2 (p < .001). Compared with all systems, the Medtronic ACT Plus Automated Coagulation Timer System (ACT Plus) resulted in the most consistent ACT values (median = 171, Interquartile Range (IQR): 169-175) and least variability (172.17 +/- 5.24). The Hemochron Signature Elite Whole Blood Microcoagulation System had the most variability (221.10 +/- 14.78) and yielded consistently higher ACT values (median = 220, IQR: 210-229.5) compared with other systems. The ACT values reported by the i-STAT Handheld and Test Cartridge Blood Analysis System (153.30 +/- 7.87) were consistently lower (median = 154, IQR: 147-161) in comparison to the ACT Plus and Medtronic HMS Plus Hemostasis Management System (180.60 +/- 7.60, median = 181, IQR: 175-186). There was no statistical difference in results between the two testing sites (p > .05) or the operators (p > .05). The significant finding of this study was the affect each system has on the ACT value. This investigation demonstrates the variability that exists among different ACT monitoring systems at our institution. The discrepant variation in ACT values that exists with the Hemochron system questions the reliability of its use in the management of patients undergoing heparin therapy.     

Heparin monitoring in sheep by activated partial thromboplastin time

Heparin anticoagulation is utilized during and after vascular surgery in animals to reduce the risk of acute or chronic thromboembolic problems. In this study, we examined variation of activated partial thromboplastin time APTT) after the intravenous bolus IV bolus) and subcutaneous SC) heparin injection in order to monitor heparin therapy in sheep. Nine healthy sheep were assigned to 3 groups A, B, and C) according to their body weights: less than 40 kg, 40 to 80 kg, and more than 80 kg, respectively. All animals were treated with heparin 300 IU/kg body weight) through two routes, and the APTT, fibrinogen, and platelet count were measured before and every hour after treatment. This showed that the APTT was increased significantly between 1 to 4 hours after IV bolus injection and between 2 to 6 hours after SC injection P < 0.05). The APTT was returned to baseline values 6 and 10 hours after the respective treatments. The APTT in Group C was consistently higher than in Group A and B after heparin treatment by the two routes. The APTT ratio entered the subtherapeutic range 5 and 8 hours after IV bolus and SC injection, respectively. The APTT ratio was maintained in the therapeutic range for about 1 and 4 hours after IV bolus and SC injection, respectively. The highest APTT ratio in Group C after SC injection of heparin was significantly higher than that in Groups A and B P < 0.05). The mean platelet counts in Groups A, B, and C before the injection were 3197 +/- 365.6, 2886 +/- 78.2, and 1861 +/- 298.0 102/microL, respectively. The mean platelet count gradually decreased without significant variation after IV bolus and SC injection. These results produced elementary data for monitoring in sheep using APTT, and suggested that heparin should be administrated by the SC route at 4-hour intervals in order to remain in the therapeutic range, after an initial IV bolus dose.     

It is the goal of this section to publish material that provides information regarding specific issues, aspects of artificial organ application, approach, philospphy, suggestions, and/or thoughts for the future. New Bedside Test for Monitoring Anticoagulation During Hemodialysis

Heparin therapy in patients can be monitored bedside during dialysis treatment by activated partial thromboplastin time (APTT) measurements using portable coagulation monitors. We verified the efficacy of the CoaguChek Plus System (Boehringer Mannheim, GmbH, Mannheim, Germany) for this purpose. The first series of results was obtained using CoaguChek Plus APTT controls (Level 1 and Level 2) on 3 instruments. The coefficients of variation (CVs) were found to be in the range of 3.6 to 5.0% based on results per instrument (n = 20) and per control level (n = 60). The second series of results was obtained using whole blood drawn from the arterial lines of patients during dialysis treatment. Three determinations out of 1 ml of fresh whole blood gave an overall mean CV of 4.9% from the 123 samples tested. Samples were taken before the onset of heparin treatment, 2 h after treatment was started, and at the end of treatment. The CoaguChek Plus APTT measurements were compared to measurements made using laboratory routine method STA APTT (Boehringer Mannheim GmbH) with results from 104 whole blood samples. Regression analysis according to Passing and Bablok showed good correlation (r = 0.885) and good agreement ( y = 0.997 x − 6.6) between both methods. Ease of use, excellent performance, reliability, and rapid availability of results within 3 min make the CoaguChek Plus APTT measurements suitable for monitoring patients during dialysis.     

Factor Xa-activated whole blood clotting time (Xa-ACT) for bedside monitoring of dalteparin anticoagulation during haemodialysis.

BACKGROUND: Low molecular weight heparins (LMWH) like dalteparin are increasingly used for anticoagulation during haemodialysis (HD). The available laboratory tests for monitoring LMWH anticoagulation are time-consuming and expensive, and the suitability of the conventional activated clotting time (ACT) is controversial. A simple and cheap bedside test would be useful. METHODS: We studied the factor Xa-activated whole blood clotting time (Xa-ACT) in vitro and in vivo in nine patients undergoing chronic HD with i.v. dalteparin bolus anticoagulation and compared it with the conventional ACT. Plasma anti-factor Xa (antiXa) activity was determined with a chromogenic assay. Thrombin-antithrombin complexes were measured to detect coagulation activation. RESULTS: Xa-ACT and ACT were prolonged with rising dalteparin concentration. In vitro, both clotting times were strongly correlated with the antiXa levels (r = 0.94 and 0.89, respectively). Nevertheless, compared with the ACT, the Xa-ACT was considerably more sensitive to the LMWH in vitro (healthy blood: Xa-ACT 90 s/U vs ACT 26 s/U; uraemic blood: Xa-ACT 96 s/U vs ACT 31 s/U) as well as in vivo (Xa-ACT 81 s/U vs ACT 22 s/U) and reflected different intensities of anticoagulation. An initial dalteparin bolus of 80+/-11 U/kg body weight was able to prevent coagulation activation for up to 4 h of HD. CONCLUSION: For monitoring LMWH anticoagulation the Xa-ACT was superior to the conventional ACT in vitro as well as in vivo during HD. The Xa-ACT can be useful as a LMWH bedside test. The ACT was not sensitive enough to serve as a LMWH monitoring tool.     

Heparin monitoring during cardiopulmonary bypass surgery using the one-step point-of-care whole blood anti-factor-Xa clotting assay heptest-POC-Hi

The activated clotting time (ACT) generally used for monitoring heparinization during cardiopulmonary bypass (CPB) surgery does not specifically measure heparin anticoagulant activities. This may result in heparin over- or under-dose and subsequent severe adverse events. A new point-of-care whole blood clotting assay (Heptest POC-Hi [HPOCH]) for quantifying heparin anticoagulant activity specifically was compared with ACT and anti-factor Xa (anti-Xa) heparin plasma levels (Coatest heparin) in 125 patients undergoing CPB surgery. The analytical reliability of the HPOCH and the influence of preanalytical variables on assay results were also examined. The ACT and HPOCH clotting times determined throughout the entire observation period correlated closely (n=683; r = 0.80; p < .0001). Similarly, there was a significant linear correlation between HPOCH and Coatest anti-Xa levels (n=352; r = 0.87; p < .0001). Pre- and post-CBP values of HPOCH, ACT, and anti-Xa plasma levels correlated closely with each other (correlation coefficients between r = 0.90 and r = 0.99; p < .0001). During CPB, there was no significant relationship between ACT and whole blood or plasma heparin levels determined by HPOCH (n=157; r = 0.19) and the chromogenic anti-Xa assay (n=157; r = 0.04), respectively. In contrast, HPOCH and anti-Xa plasma levels correlated strongly during CPB (n=157; r = 0.57; p < .0001). However, bias analysis showed that the HPOCH and Coatest heparin could not be used interchangeably. The HPOCH was well reproducible and not influenced by aprotinin, hemodilution, or other factors affecting ACT. The HPOCH seems to be a promising new tool for specific on-site measurement of heparin activities in whole blood during CPB.     

Effects of heparin, haemodilution and aprotinin on kaolin-based activated clotting time: in vitro comparison of two different point of care devices

BACKGROUND: During cardiopulmonary bypass (CPB), measurement of kaolin-based activated clotting time (kACT) is a standard practice in monitoring heparin-induced anticoagulation. Despite the fact that the kACT test from the Sonoclot Analyzer (SkACT) has been commercially available for several years, no published data on the performance of SkACT are available. Thus, the aim of this in vitro study was to compare SkACT with an established kACT from Hemochron (HkACT). METHODS: Blood was withdrawn from 25 patients before elective cardiac surgery. SkACT and HkACT were measured in duplicate after in vitro administration of heparin (0, 1, 2 and 3 U/ml), calcium-free lactated Ringer's solution (25% and 50% haemodilution) and aprotinin (200 kIU/ml). RESULTS: A total of 600 duplicate kACT measurements were obtained from 25 cardiac surgery patients. Overall, mean bias +/- SD between SkACT and HkACT was 7 +/- 70 s (1.3% +/- 14.1%). Administration of heparin, haemodilution and aprotinin induced a comparable effect on both activated clotting time (ACT) tests. Mean bias ranged from -4 +/- 39 s (-1.7% +/- 12.9%) to 4 +/- 78 s (3.2% +/- 15.6%) for heparinzed blood samples after haemodilution or aprotinin application and increased after combined aprotinin administration and haemodilution. After haemodilution and administration of aprotinin, both ACT tests were less reliable for values >480 s in heparinized blood samples. CONCLUSION: Accuracy and performance of SkACT and HkACT were comparable after in vitro administration of heparin, aprotinin and haemodilution. Both ACT tests were considerably affected by aprotinin and haemodilution.     

Heparinase in the activated clotting time assay: monitoring heparin-independent alterations in coagulation function.

The activated clotting time (ACT) is routinely used to monitor heparin during cardiopulmonary bypass surgery. Activated clotting times may be influenced by a number of factors other than heparin. The presence of heparin in blood samples disguises the occurrence of non-heparin-related changes in coagulation function. During cardiopulmonary bypass, it is difficult to ascertain baseline clotting time fluctuations with ACT alone. Previous attempts to establish accurate baseline data were imprecise and involved extensive sample handling. In this study, we present data obtained using a modified (ACT) assay that incorporates heparinase. The heparinase test cartridge (HTC) instantaneously, specifically, and completely removes heparin in the blood sample at the initiation of the test. In conjunction with standard ACT techniques, the clinician is provided with heparin-independent (baseline) and functional clotting data. The HTC/ACT assay was used in a case study involving 19 patients undergoing cardiopulmonary bypass surgery. The data gathered indicate the usefulness of this assay in monitoring incidents of baseline drift, hemodilution, and hypercoagulation and the efficacy of protamine reversal.     

In vitro removal of beta-2-microglobulin from uremic blood with an immunoadsorption wall

Dialysis-related amyloidosis (DRA), caused by the accumulation of beta-2-microglobulin (β-2M), remains a major concern in long-term renal replacement therapies. For years, we have developed an immunoadsorption wall (iWall) for the removal of β-2M. In this study, we employed a new approach taking advantage of the melting of a buffer ice rod to improve the conditions associated with the manufacturing of an iWall and tested its performance with uremic serum and blood. The preliminary results reveal that the present iWalls thus prepared not only possess the superior properties of affinity and specificity but also show structural stability and acceptable hemocompatibility. We believe that this breakthrough might provide a promising path to successful treatment of DRA as well as establish a useful platform for studying removal of certain pathological toxins accumulated in the blood.     

Anticoagulation monitoring during vascular surgery: accuracy of the Hemochron low range activated clotting time (ACT-LR)

Background. Activated clotting time (ACT) is currently usedto monitor high concentrations of heparin anticoagulation. Anew instrument, the Hemochron® Jr Signature device, hasbeen specifically designed to measure ACT in low-range heparinplasma concentrations (ACT-LR). The purpose of this study wasto compare ACT-LR with anti-Xa activity in patients receivinglow-dose i.v. heparin during vascular surgery. Methods. Thirty patients, undergoing arterial vascular surgery,were included in the study and received unfractionated heparin(initial dose 50 u kg^–1). One hundred and thirty-two pairsof blood samples were simultaneously collected during surgeryto determine ACT-LR and anti-Xa activity. Pearson correlation,Kappa test, ROC curve and a specific clinical interpretationof the correlation were performed. Results. ACT-LR ranged from 68 to 380 s, anti-Xa activity from0 to 1.45 u ml^–1. We observed a strong correlation betweenanti-Xa activity and ACT-LR (r²=0.87; P<0.0001). Accuracyof ACT-LR was good for anti-Xa activity up to 0.6 u ml^–1(Kappa, 0.94; accuracy, 97%) and 0.8 u ml^–1 (Kappa, 0.79;accuracy, 90%), and poor for anti-Xa activity above 1 u ml^–1(Kappa, 0.59). A clinical interpretation of the correlationgraph found 98% of measured ACT-LR values to be accurate. Conclusion. Hemochron® Jr Signature provides measurementsof ACT-LR, which are accurate for monitoring heparin anticoagulationat anti-Xa activity below 0.8 u ml^–1.     

Pulse push/pull hemodialysis: in vitro study on new dialysis modality with higher convective efficiency

Abstract:  Midsize molecule retention is related with renal-failure-associated mortality. Here, the authors describe a new dialysis modality, pulse push/pull hemodialysis (PPPHD), which increases convective clearance. Blood and dialysate are circulated by a pulsatile pump, but with pulsatile flow patterns that are 180° out of phase. This causes blood-to-dialysate pressure gradients that oscillate between positive and negative, and which cause consecutive periods of ultrafiltration and backfiltration. The devised PPPHD was compared with conventional high-flux hemodialysis (CHFHD) in terms of solute clearances, albumin loss, and total protein levels. Human plasma containing dissolved uremic marker molecules was used as a blood substitute, and clearances were investigated for blood urea nitrogen, creatinine, vitamin B12, and inulin. Observed clearances were found to be significantly higher for PPPHD by approximately 3–14% for low-molecular-weight solutes, by 47–48% for vitamin B12, and by 38–49% for inulin than for CHFHD. No albumin loss was observed in either of these two study groups. The authors conclude that PPPHD offers a simple straightforward means of enhancing uremic molecule removal by increasing total ultrafiltration volume without the need to infuse replacement fluid.     

Saving the zone of stasis in burns with activated protein C: An experimental study in rats

Salvage of the zone of stasis is a major subject of focus in burn research. Use of various antithrombotic, anti-inflammatory and antioxidant drugs have been studied experimentally, with reports of favourable results; however, none became popular in clinical practice.     

23例终末期肾病患者透析时机影响因素的调查分析

目的 评估基层医院终末期肾病患者的透析时机,探讨过晚透析的影响因素及改进措施.方法 以郸城县人民医院透析科2007年7月1日至2009年7月1日开始透析的所有非糖尿病性终末期肾病患者为研究对象,分析其开始透析时血肌酐、肾小球滤过率、尿毒症症状、尿毒症心、脑血管并发症、首次透析情况,调查过晚透析的影响因素.结果 (1)进入透析时肾小球滤过率平均为(3.6±0.9)ml/min;(2)所有患者均有尿毒症并发症、营养状态下降,30.4%患者需急诊透析;(3)91.3%患者系透析时机过晚,其原因以经济原因多见,其次与就诊晚和认识不足有关.结论 基层医院开始血液透析的终末期肾病患者多数为透析时机过晚.经济原因、就诊过晚及认识不足是影响透析时机的关键因素.     

Citrate lock versus heparin lock for the prevention of catheter related infections in hemodialysis patients with tunneled catheters: a Meta-analysis of randomized controlled trials

ObjectiveTo study whether citrate lock is superior to heparin lock in the prevention of catheter related infections, bleeding complications and catheter malfunctions among hemodialysis patients with tunneled catheters. MethodsBy searching in Pubmed, the Cochrane Library, EMBASE, Ovid, WanFang, VIP, CNKI and CBM databases as well as related journals, qualified randomized controlled trials were included in a Meta - analysis using Revman 5.0 and STATA 10.0 software. The endpoints included catheter related infection, bleeding complication, thrombolytic treatment, catheter removal for malfunction, catheter thrombosis and all - cause death. ResultsFifteen randomized controlled trials were included with 1621 patients involved. Eight studies compared citrate alone with heparin lock, while 7 trials focused on citrate in combination with other antimicrobials. Pooled analysis demonstrated that incidence of catheter related infections in patients receiving citrate lock decreased by 47% compared with those on heparin (RR=0.53, 95%CI 0.36-0.77, P＜0.01). Subgroup analysis by types of citrate lock indicated that all combined lock solutions of citrate and other antimicrobials (citrate + gentamicin, citrate + taurolidine, citrate + methylene blue + methylparaben + propylparaben) were superior to heparin lock in preventing catheter-related infections (P＝0.01, 0.04, 0.01, respectively); citrate alone seemed to reduce catheter-related infection risk (RR＝0.68), but no statistically significant difference was observed (95%CI 0.38-1.21, P＝0.19). There were fewer patients with bleeding complications in citrate group (RR＝0.53, 95%CI 0.34-0.84, P＜0.01), while citrate showed no advantage over heparin lock in terms of thrombolytic treatment (P＝0.93), catheter removal for malfunction (P＝0.35), catheter thrombosis (P＝0.64) and all - cause death (P＝0.35). ConclusionsFor hemodialysis patients with tunneled catheters, combined lock solutions of citrate and other antimicrobials, rather than citrate alone, are superior to heparin in preventing catheter related infections. Citrate locks are associated with less bleeding complications, and are comparable to heparin in the maintenance of catheter patency.     

5-氟尿嘧啶不同容量腹腔化疗的药代动力学及活性炭应用对其的影响

目的　探讨不同药物浓度及缓释剂应用对 5 氟尿嘧啶 (5 Fu)药代动力学的影响。方法　以家兔为模型 ,用高效液相色谱法 ,检测相同 5 Fu剂量下 (10 0mg/kg) ,大容量腹腔化疗、小容量腹腔化疗、小容量缓释腹腔化疗 (加入活性炭 )在不同时间点的药物浓度 ,计算药代动力学参数。结果　大容量腹腔化疗峰浓度 69.75 3mg/L ,半衰期 0 .80 1h。小容量腹腔化疗峰浓度略低大容量腹腔化疗 60 .3 65mg/L ,半衰期 1.10 8h ,作用时间较长。小容量缓释腹腔化疗 ,虽然浓度较小2 0 .693mg/L ,但半衰期 19.10 2h ,作用时间最长。 结论　从药代动力学的角度 ,小容量腹腔化疗是一种较为理想的化疗方式。加入活性炭以后可以更进一步增加药物的作用时间。