The precision of ROTEM EXTEM is decreased in hypocoagulable blood: a prospective observational study.

BACKGROUND: The use of viscoelastic tests is becoming increasingly popular. There is a paucity of validation of the reproducibility of varying coagulation states. Therefore, we aimed to study the coefficient of variation (CV) for the ROTEM EXTEM parameters clotting time (CT), clot formation time (CFT), alpha-angle and maximum clot firmness (MCF) in blood with varying degrees of coagulation strength. The hypothesis was that CV increases in states of hypocoagulability. METHODS: Critically ill patients and patients subjected to neurosurgery at a university hospital during three separate periods were included. Each blood sample was tested in eight parallel channels, yielding the CVs for the tested variables. In 25 patients, the blood samples were analysed both at baseline and after dilution with albumin 5%, as well as after being spiked with fibrinogen, simulating weak and strong coagulation. RESULTS: In total, 225 unique blood samples were collected from 91 patients. All samples were analysed in eight parallel ROTEM channels, resulting in 1,800 measurements. In hypocoagulable samples, defined as those with values outside the normal reference range, the CV of CT was higher (median (interquartile range)) (6.3% (5.1-9.5)) than for normocoagulable samples (5.1% (3.6-7.5)), p < 0.001. CFT showed no difference (p = 0.14), while the CV of alpha-angle was higher in hypocoagulable samples (3.6% (2.5-4.6)) than in normocoagulable samples (1.1% (0.8-1.6), p < 0.001. The CV of MCF was higher in hypocoagulable samples (1.8% (1.3-2.6)) than in normocoagulable samples (1.2% (0.9-1.7)), p < 0.001. The CV ranges for the different variables were as follows: CT: 1.2%-37%, CFT: 1.7%-30%, alpha-angle: 0.0%-17% and MCF: 0.0%-8.1%. CONCLUSIONS: CVs for the EXTEM ROTEM parameters CT, alpha-angle, and MCF increased in hypocoagulable blood compared to blood with normal coagulation, confirming the hypothesis for CT, alpha-angle, and MCF but not for CFT. Furthermore, the CVs for CT and CFT were much higher than those for alpha-angle and MCF. The results demonstrate that EXTEM ROTEM results from patients with weak coagulation should be interpreted with the notion of limited precision and that procoagulative treatment, based only on ROTEM EXTEM, should be given with some caution.

Biomarkers of Complement and Platelet Activation are not correlated with the One or Twenty-Four Hours Corrected Count Increments in Prophylactically Platelet Transfused Hematological Patients: a Prospective Cohort Study.

Platelet transfusion refractoriness is a serious clinical concern that complicates the management of thrombocytopenic patients. Previous studies have suggested a potential role for both complement and platelet activation based on in vitro analyses of platelet concentrates. In this study, the post-transfusion platelet response, as indicated by the corrected count increment at 1 and 24 h after prophylactic platelet transfusions, respectively, was correlated with the 1 h post-transfusion Δconcentration (1 h post-transfusion - pretransfusion) of complement and platelet activation biomarkers. The study was registered as a clinical trial at ClinicalTrials.gov (identifier: NCT02601131) and patients were recruited during inpatient care in the hematological department. Soluble terminal complement complexes, soluble P-selectin and soluble CD40 ligand were analyzed. Confirmed alloimmunized patients were excluded. Included subjects were either given platelet transfusions (n = 43) and categorized into four clinical study groups or included in a non-transfused control group (n = 10). In total, 54 transfusions were included. No transfusion-mediated complement activation was observed. The transfusions were associated with a significant increase in the concentration of soluble P-selectin (p < .001), primarily corresponding to the passive infusion of soluble P-selectin-containing plasma residuals. The Δconcentration of soluble P-selectin was, however, not significantly correlated with the corrected count increments. Thus, significant correlations between biomarkers of complement and platelet activation and the post-transfusion platelet response could not be demonstrated in this study.

Mechanical complications of central venous catheter insertions: A retrospective multicenter study of incidence and risks.

BACKGROUND: Incidence and risk factors for complications after insertion of central venous catheters have previously been reported for smaller cohorts. The aim of this observational multicenter study was to study risk factors for mechanical complications in a large, recently collected cohort of patients. METHODS: Records of central venous catheter insertions from 8 hospitals in southern Sweden from 2013 to 2016 were collected from the regional chart system. Data on blood coagulation tests, use of ultrasonography, central venous catheter location, bore size, number of needle passes, arterial puncture, the chronological order of the central venous catheter insertion, and mechanical complications were extracted. Only one insertion/patient was included using worst-case selection criteria. Predefined primary outcome was mechanical complications defined as bleeding, pneumothorax, nerve injury, or malignant arrhythmia. Severe mechanical complications were defined as bleeding requiring intervention or transfusion, pneumothorax, persistent nerve injury, or non-self-limiting arrhythmias. RESULTS: We included 10 949 insertions and identified 118 (1.1%) incidents of mechanical complication, of which 85 (0.8%) were bleedings, 21 (0.2%) were pneumothoraces, 7 (0.06%) were transient nerve injuries, and 5 (0.05%) were self-limiting arrhythmias. Severe mechanical complications occurred in 23 (0.2%) cases. CONCLUSIONS: In this retrospective, multicenter observational study on 10 949 central venous catheter insertions, mechanical complications were rare. Preprocedural coagulopathy, number of needle passes, and arterial puncture were associated with grade 2-4 bleeding. Subclavian vein insertions, arterial puncture, and chronological order of the central venous catheter insertion were associated with pneumothorax.

High-dose omega-3 fatty acids have no effect on platelet aggregation or coagulation measured with static and flow-based aggregation instruments and Sonoclot; an observational study in healthy volunteers.

The effect of omega-3 fatty acids on platelet aggregation and coagulation is highly unclear. Studies both support and refute the impacts of omega-3 fatty acids on prolonged bleeding time and platelet inhibition as well as its purported positive effects on cardiovascular disease. In a previous pilot study we suggested an inhibition of platelet aggregation measured with multiple electrode aggregometry. Following on that, the aim of the present study was to investigate the effects of supplementary high doses of omega-3 fatty acids on platelet aggregation and coagulation in a sample-size calculated number of healthy volunteers using Sonoclot, multiple electrode aggregometry, and flow-based Cellix instruments after 10 days of omega-3 fatty acid intake. Twelve healthy human volunteers ingested 2520 mg of supplementary omega-3 fatty acids per day for 10 days. Venous blood was sampled and platelet aggregation and coagulation were measured before and after the treatment period. The viscoelastic test instrument Sonoclot, multiple electrode aggregometry, and flow-based Cellix instruments with collagen-coated channels were used to evaluate platelet aggregation and coagulation. There were no differences in any of the measured variables after the treatment period as compared to before. In this well-powered study on healthy volunteers, no effects of high doses of omega-3 fatty acids after 10 days of intake could be demonstrated, either on coagulation or platelet function. Further studies are needed to clarify whether omega-3 fatty acids have a role in the regulation of the putative complex processes in vivo.

Linear decline of corrected platelet count increment within 24 hours after platelet transfusion in haematological patients: A prospective observational study.

OBJECTIVES: The aim of this study was to prospectively explore the detailed longitudinal development of platelet increments in patients with chemotherapy-induced bone marrow aplasia during the first 24 hours after platelet transfusion. METHODS: Patients admitted to the Haematology department during 7 months, and fulfilled inclusion criteria were divided into 4 groups: Group 1, patients with acute leukaemia; Group 2, patients after autologous stem cell transplantation (SCT); Group 3, patients after allogeneic SCT; and Group 4, patients given platelet transfusion prior to intervention. We used frequent blood sampling within 24 hours after platelet transfusion to investigate the kinetics of platelet counts following transfusion. RESULTS AND CONCLUSIONS: Fifty-four platelet transfusion occasions in patients with chemotherapy-induced bone marrow aplasia were included. The decrease in corrected count increment (CCI) 1-24 hours after platelet transfusions in all groups could be described as linear functions. For patients in the aggregated Groups 1-3, the decline was 2.0% ± 0.6% (mean ± standard deviation) per hour. For patients in Group 4, the decline of CCI was 2.8% ± 1.2% per hour. We found no differences between the groups, either in the rate of platelet elimination from the bloodstream or in the mean CCI, in the first 24 hours post-transfusion.

Vitamin K and cancer.

Subclinical vitamin K deficits refer to carboxylation defects of different types of vitamin K-dependent hepatic and extrahepatic so-called Gla proteins without prolongation of the prothrombin time. This condition has been reported in different clinical situations due to insufficient supply or malabsorption of vitamin K as well as drug interactions. This review discusses the effects of different vitamin K subspecies on tumour growth and the possible anti-tumour effects of increased vitamin K intake. Blocking carboxylation of vitamin K-dependent proteins with warfarin anticoagulation - what are the risks/benefits for carcinogenesis? Previous studies on both heparin and low molecular weight heparin blocking of the vitamin K-dependent factors X and II have shown tumour suppressive effects. Vitamin K has anti-inflammatory effects that could also impact carcinogenesis, but little data exists on this subject.

A pilot study on the applicability of thromboelastometry in detecting brain tumour-induced hypercoagulation.

Patients with intracranial tumours have an increased risk of venous thromboembolism, particularly during the first month after neurosurgery. A proposed explanation for this increased risk, are procoagulant tumour-derived substances, such as tissue factor, usually measured in peripheral blood. The aim of the present study is to investigate whether a rotational thromboelastometry (ROTEM) can measure the procoagulative activity of tumour tissue. The study included 21 patients who were undergoing a craniotomy and complete tumour resection after written consent and ethical approval were obtained. Tumour tissue was biopsied during surgery and used for in vitro spiking of patients own citrated whole blood. Blood samples with or without spiking were analyzed with ROTEM using different activating reagents. ROTEM clotting time significantly decreased (p < .001), indicating a hypercoagulative response on clot initiation that was strongest for glioma tumours. However, ROTEM clot formation time was significantly prolonged (p < .001), which was an opposite response that indicated poor initial clot propagation. ROTEM maximum lysis was increased in the tumour tissue-spiked samples (p < .001), indicating a strong fibrinolytic activity in brain tumour tissue. Tissue extracts from intracranial tumours have both procoagulant and fibrinolytic effects that are detectable with ROTEM. Glioma tumours had the strongest hypercoagulative response in our in vitro model. Larger studies are necessary to test the clinical relevance and accuracy of tumour extract spiked viscoelastic tests to predict the individual patient risk for developing a thrombotic complication.

Detection of subclinical vitamin K deficiency in neurosurgery with PIVKA-II.

Vitamin K is known for supporting the carboxylation of hepatic coagulation proteins. Levels of proteins induced by vitamin K absence for factor II (PIVKA-II) reflect hypocarboxylated prothrombin and can be used to detect subclinical vitamin K deficiency. The aim of this study was to determine the prevalence of perioperative subclinical vitamin K deficiency among neurosurgical patients using PIVKA-II and investigate the existence of any correlation to standard coagulation assays. Also, the antitumor effects of vitamin K were reviewed. Thirty-five patients undergoing brain tumor resection were included. Blood samples were drawn preoperatively, at the end of surgery and in the morning after surgery. In addition to PIVKA-II, factor II and the Owren and Quick prothrombin times were analyzed. Seventeen of 35 patients had elevated PIVKA-II levels before surgery, which continued to be above normal range postoperatively. Median PIVKA-II and Owren prothrombin time (PT-INR) were increased on the morning day 1 postoperatively compared to before surgery, whereas Quick end-stage prothrombin time (EPT) decreased and factor II was unaffected. Postoperative complications were connected to high PIVKA-II increases. Positive correlations between PIVKA-II and factor II and body mass index (BMI) were found. In conclusion, PIVKA-II was increased in many patients preoperatively and then increased by the morning following surgery. Standard coagulation assays were largely non-pathological. Correlations were demonstrated between PIVKA-II and factor II and BMI. The effect of perioperative treatment with different vitamin K supplements should be investigated in future studies, as well as clinical trials evaluating their antitumor effects.

ROTEM monitoring of activated and non-activated prothrombin complex concentrate correction of dilutional coagulopathy.

OBJECTIVES: Prothrombin complex concentrates have been used to correct dilutional coagulopathy, but many preparations contain anticoagulants, such as heparin, to counteract their prothrombotic effects. These anticoagulants can interfere with haemostatic assays. The aim of this study was to monitor two different prothrombin complex concentrates for the treatment of albumin dilution in vitro, using rotational thromboelastometry with or without the heparin-antagonising agent protamine. METHODS: Citrated blood from 10 healthy volunteers was, in vitro, diluted 1:1 with 5% albumin and then corrected with a four-factor prothrombin complex concentrate with heparin anticoagulant (Confidex®) corresponding to a clinical dose of 43 IU/kg. Blood samples were tested with or without protamine. An activated prothrombin complex concentrate (APCC) (FEIBA®) without heparin in doses of 50 IU/kg and 100 IU/kg was also tested. Thromboelastometry was performed after recalcification. RESULTS: Albumin dilution significantly affected all thromboelastometry parameters. The four-factor PCC had an additional anticoagulant effect when added to the albumin-diluted blood; it was partially corrected by protamine for all parameters except maximum clot firmness. The APCC significantly improved all parameters, with over-correction of clotting time but only partial correction of maximum clot firmness. CONCLUSIONS: The anticoagulant content of many prothrombin complex concentrates needs to be considered when performing in vitro testing. A heparin-free APCC better corrected an in vitro albumin-induced dilutional coagulopathy than a four-factor PCC, despite of blocking heparin with protamine.

Desmopressin in vitro effects on platelet function, monitored with Multiplate, ROTEM and Sonoclot.

Background and aims The vasopressin analogue desmopressin has demonstrated efficacy in decreasing bleeding time by increasing the circulating levels of coagulation factor VIII and von Willebrand factor, but also by direct effects on platelets. Previous studies have demonstrated contrasting results regarding the effect of desmopressin on platelets in vitro. The aim of this study was to investigate the dose-response effects of in vitro desmopressin in whole blood. Our hypothesis was that desmopressin could increase platelet function in anticoagulated whole blood being stored up to 4 hours. Methods Desmopressin was administered with up to four different concentrations to venous whole blood, sampled with standard vacutainer tubes from 10 healthy volunteers after consent. Platelet function was analyzed with three different point-of-care techniques: Multiplate platelet aggregometry with adenosine diphosphate, collagen, thrombin receptor activating peptide-6, ristocetin and arachidonic acid agonists, tissue factor-activated thromboelastometry and Sonoclot glass bead viscoelastic coagulation tests at baseline and 4 hours later using different activator reagents. Results Thromboelastometry and Sonoclot did not show any significant change between baseline and 4 h later. A significant decrease in area under curve (AUC) could be seen with the Multiplate between baseline and after 4 h. Desmopressin did not improve any of these tests at baseline or during a 4 h storage and incubation period. Conclusion In vitro administered desmopressin could not increase normal platelet function or coagulation being measured with thromboelastometry and Sonoclot. Multiplate indicated decreased platelet aggregation over time, without any effect of in vitro added desmopressin.

Effects of naturopathic medicines on Multiplate and ROTEM: a prospective experimental pilot study in healthy volunteers.

BACKGROUND: Of patients undergoing surgery, 22 to 57% have been reported to be using naturopathic medicines. Several of these medicines have been reported to increase bleeding or enhance the effect of other drugs that increase bleeding. The Swedish Medical Products Agency recommends cessation of the use of the naturopathic medicines echinacea, fish oil, ginkgo biloba, ginseng, St. John's wort, valeriana and garlic 2 weeks before surgery. The aim of this pilot study was to examine the effects of these 7 naturopathic medicines in healthy humans by utilising multiple electrode aggregometer (Multiplate) and viscoelastic rotational thromboelastometer (ROTEM) to obtain data for sample size calculation before a larger trial. METHODS: Thirty-five healthy volunteers ingested one of the listed naturopathic medicines for 7 days. Each naturopathic medicine was taken in a recommended standard dose by 5 volunteers. ROTEM clot initiation (CT), clot formation (CFT), α-angle (AA) and clot structure (MCF) were analysed with tissue factor activated (EXTEM) and native (NATEM) assays. The Multiplate platelet aggregation area under curve (AUC) was measured with adenosine diphosphate (ADP), collagen (COL) and arachidonic acid (ASPI) assays. RESULTS: Multiplate with ADP agonist decreased from 73 ± 8.7 AUC to 60 ± 5.9 AUC (P = 0.003, 95% confidence interval (CI) -19.2 to -7.6) after medication with fish oil, but fish oil had no effect on COL or ASPI reagents. None of the other naturopathic medicines had any effect on Multiplate aggregometry. ROTEM NATEM-CFT increased from 217 ± 32 s to 283 ± 20 (P = 0.009, 95% CI 26.8 to 107), and NATEM-AA decreased from 52 ± 3.9° to 44 ± 2.3° (P = 0.009, 95 % CI -12.0 to -3.2) after medication with fish oil. There were no significant changes in the other NATEM or EXTEM parameters. The other naturopathic medicines had no significant effects on ROTEM or Multiplate aggregometry. CONCLUSIONS: We have demonstrated that a recommended standard intake of 1260 mg Ω-3 polyunsaturated fatty acids (fish oil) daily - but not echinacea, ginkgo biloba, ginseng, St. John's wort, valeriana or garlic - may decrease platelet aggregation and clot formation. A larger trial in this setting would be meaningful to perform. TRIAL REGISTRATION: Trial registration ISRCTN78027929. Registered 19 May 2015.

Temperature effects on haemostasis in whole blood from ticagrelor- and aspirin-treated patients with acute coronary syndrome.

BACKGROUND: Comatose survivors after cardiac arrest are treated with mild induced hypothermia and potent platelet- inhibiting drugs after coronary stenting. Previous studies have shown an increased incidence of stent thrombosis during clopidogrel and aspirin treatment in conjunction with induced hypothermia. The aim of this study was to investigate the in vitro effect of induced hypo- and hyperthermia on blood from patients undergoing ticagrelor- and aspirin-mediated platelet inhibition. METHODS: Whole blood from 15 patients with acute coronary syndrome who were treated with ticagrelor and aspirin and from eight healthy volunteers was incubated for 1 hour at 28, 33, 37, and 39°C. RESULTS: In blood from patients with acute coronary syndrome, the activated clotting time (Sonoclot) was prolonged in mild hypothermic (33°C) compared to normothermic (37°C) samples. Sonoclot, clotting rate and platelet function were decreased in hypothermic compared to normothermic samples. Platelet-induced activation and aggregation (Multiplate) was unchanged in mild hypothermic compared to normothermic samples. In contrast, mild hypothermia supported increased platelet activation as measured with flow cytometry with up-regulation of PAC-1 and P-selectin on the platelet surface. CONCLUSION: In acute coronary syndrome patients treated with ticagrelor and aspirin, in vitro hypothermia to 33°C markedly increased platelet activity measured with flow cytometry, whereas viscoelastic coagulation test (Sonoclot) revealed a hypocoagulative response. Prospective clinical trials studying platelet inhibition at different temperatures and correlating changes in platelet function to bleeding or stent occlusion are needed.

Perioperative changes in PIVKA-II.

BACKGROUND AND AIMS: Proteins induced by vitamin K absence for factor II (PIVKA-II) is an enzyme-linked immunosorbent assay that monitors uncarboxylated prothrombin and responds to vitamin K deficits prior to changes in the prothrombin test. The aim of this project was to study perioperative PIVKA-II changes during various types of surgery in a prospective observational study. METHODS: Patients undergoing abdominal or orthopaedic surgery were included. Blood was sampled on the day of surgery (preoperatively) and up to 5 days after surgery. The activated partial thromboplastin time, Quick and Owren prothrombin times were analyzed, together with PIVKA-II. RESULTS: Thirty-nine patients were included, 27 +male and 12 +female. All but 7 +patients had elevated PIVKA-II levels preoperatively. PIVKA-II levels had already increased significantly (p < 0.017) on day 1 after surgery as compared to presurgery plasma levels. The median PIVKA-II was highest on day 5. Routine tests were mostly normal. No significant difference in PIVKA-II was seen when comparing patients undergoing abdominal versus orthopaedic surgeries. There was no significant correlation between PIVKA-II and routine coagulation tests. Patients with anterior resection, emergency laparotomy and emergency hip fractures had higher postoperative increases, which could be linked to increased gastrointestinal recovery times, paralytic ileus, peritonitis and comorbidities. CONCLUSIONS: PIVKA-II levels increase during the perioperative period, despite mostly normal routine coagulation tests. Pre- and perioperative vitamin K supplementation in patients with elevated PIVKA-II levels should be studied, and its clinical significance be defined in future studies.

Comparison of fibrin-based clot elasticity parameters measured by free oscillation rheometry (ReoRox ®) versus thromboelastometry (ROTEM ®).

BACKGROUND: Whole blood viscoelastic tests such as the fibrin-based thromboelastometry (ROTEM(®)) test FIBTEM are increasingly used in the perioperative setting to quickly identify deficits in fibrin quality, and to guide hemostatic therapy. The recently developed FibScreen2 test of the ReoRox(®) method, based on free oscillation rheometry, also provides an evaluation of fibrin clot quality. To date, little information is available on the performance of this test in hemodiluted blood, by comparison to FIBTEM. METHODS: Whole blood samples from eight healthy volunteers were analyzed using FIBTEM and Fibscreen2. Native and diluted (to 33% and 50% using saline, gelatin or hydroxyethyl starch [HES]) samples were analyzed. Clot strength parameters, including FIBTEM maximum clot firmness (MCF), FIBTEM maximum clot elasticity (MCE) and Fibscreen2 maximum elasticity (G'max), were measured. RESULTS: In repeatedly measured samples from two volunteers, FIBTEM MCF and Fibscreen2 G'max revealed a coefficient of variation (CV) of 5.3 vs. 16.3% and 5.6 vs. 31.7% for each volunteer, respectively. Hemodilution decreased clot strength. Both Fibscreen2 G'max and FIBTEM parameters decreased proportionally to the dilution ratio when saline was used. The observed reductions in FIBTEM and Fibscreen2 parameters were more severe in samples diluted with gelatin and HES, compared to saline. Finally, a regression analysis between FIBTEM MCE and Fibscreen2 G'max revealed a poor goodness of fit (r(2) = 0.37, p < 0.0001). CONCLUSIONS: ReoRox(®) Fibscreen2 test has a high coefficient of variation, and its application in various hemodilution conditions showed limited comparability with the ROTEM(®) FIBTEM test.

Thromboelastometry versus free-oscillation rheometry and enoxaparin versus tinzaparin: an in-vitro study comparing two viscoelastic haemostatic tests' dose-responses to two low molecular weight heparins at the time of withdrawing epidural catheters from ten patients after major surgery.

BACKGROUND: Monitoring low molecular weight heparins (LMWH's) in the perioperative period is prudent in patients at high risk of coagulative complications, especially when the patient has an epidural catheter requiring withdrawal, which is associated with the risk of spinal haematoma. The aim of this study was to evaluate the in vitro dose-responses of two different LMWH's on two different viscoelastic haemostatic tests, using blood sampled from patients with normal routine coagulation parameters, on the day after major surgery when their epidural catheters were due to be withdrawn. METHODS: Enoxaparin or tinzaparin were added in vitro to blood from ten patients who had undergone oesophageal resection, to obtain plasma concentrations of approximately 0, 0.5, 1.0 and 1.5 IU/mL. Coagulation was monitored using thromboelastometry (ROTEM®) using the InTEM® activating reagent; and free oscillation rheometry (FOR: ReoRox®), activated using thromboplastin. Clot initiation was measured using ROTEM-CT, ReoRox-COT1 and ReoRox-COT2. Clot propagation was measured using ROTEM-CFT, ROTEM-Alpha Angle and ReoRox-Slope. Clot stability was measured using ROTEM-MCF and ReoRox-G'max, and clot lysis was measured using ROTEM-ML and ReoRox-ClotSR. RESULTS: Clot initiation time assessed by thromboelastometry and FOR was prolonged by increasing concentrations of both LMWH's (P < 0.01). Equivalent doses of tinzaparin in international units (anti-FXa units) per millilitre prolonged clot initiation more than enoxaparin (P < 0.05). There was significant inter-individual variation - the ranges of CT and COT1 at LMWH-concentrations of 0 and 1.5 IU/mL overlapped. None of the tests reflecting clot formation rate or stability showed a dose-response to either LMWH but clot lysis showed a tentative negative dose-response to the LMWH's. CONCLUSIONS: Clot initiation time's dose-dependent prolongation by LMWH's in this study agrees with previous research, as does tinzaparin's stronger anti-coagulative effect than enoxaparin at equivalent levels of anti-FXa activity. This casts doubt on the validity of using anti-FXa assays alone to guide dosage of LMWH's. The significant inter-individual variation in dose-response suggests that the relationship between dose and effect in the postoperative period is complicated. While both ROTEM and FOR may have some role in postoperative monitoring, more research is needed before any conclusion can be made about their clinical usefulness.

Platelet aggregation and clot formation in comatose survivors of cardiac arrest treated with induced hypothermia and dual platelet inhibition with aspirin and ticagrelor; a prospective observational study.

INTRODUCTION: We conducted a prospective observational study in cardiac arrest survivors treated with mild induced hypothermia, evaluating different platelet function tests at hypo- and normothermia. We also investigated the relation between gastric emptying and vasodilator stimulated phosphoprotein (VASP). METHODS: Comatose survivors of out of hospital cardiac arrest were included and divided into two groups, depending on whether dual platelet inhibition with peroral ticagrelor and aspirin was given or not. The first blood samples (T1) were collected 12-24 hours after reaching target temperature (33°C) and were compared to blood samples collected 12-28 hours after reaching normothermia (37°C) (T2) within each group. All samples were analysed by Sonoclot viscoelasticity, flow cytometry based VASP and with multiple electrode aggregometry, Multiplate®; adenosine diphosphate (ADP), collagen (COL), thrombin receptor agonist peptide (TRAP) and arachidonic acid (ASPI). Sonoclot and Multiplate® instruments were set on in vivo temperatures. Gastric secretion from the nasogastric tube was measured to assess absorption of per orally administered antiplatelet drugs. Differences between T1 and T2 within each group were calculated using Wilcoxon matched pairs signed test. Significance levels were set at P <0.01. RESULTS: In total, 23 patients were included. In patients with dual platelet inhibition (n =14) Multiplate®-analyses showed no changes in ADP stimulated platelets. COL, TRAP and ASPI aggregations were higher at T2 compared to T1. Sonoclot-analyses showed that activated clotting time (ACT) was unchanged but both clot rate (CR) and platelet function (PF) were higher at T2 compared to T1. VASP decreased from 53 ± 28(T1) to 24 ± 22(T2), (P <0.001). The average volume of gastric secretion aspirated before T1 correlated well with VASP (T1), r =0.81 (P <0.001). In patients with no platelet inhibition, (n =9) similar changes between T1 and T2 were seen as in patients with dual platelet inhibition while VASP was unchanged. CONCLUSIONS: We have demonstrated increased platelet aggregation and strengthened clot formation over time in out of hospital cardiac arrest patients treated with hypothermia. In patients on oral dual platelet inhibition, the effect of ticagrelor was delayed, probably due to slow gastric emptying.

The effect and duration of prophylactic platelet transfusions before insertion of a central venous catheter in patients with bone marrow failure evaluated with point-of-care methods and flow cytometry.

BACKGROUND: Patients with bone marrow failure and severe thrombocytopenia are frequently given prophylactic platelet transfusion before interventions. The clinical effects of such transfusions, however, are poorly defined. We performed a prospective observational study on patients with bone marrow failure scheduled for prophylactic platelet transfusion before the insertion of a central venous catheter. The objectives were to evaluate the effect and duration of prophylactic platelet transfusions on central venous catheter insertion in thrombocytopenic patients with bone marrow failure. METHODS: Thirty-nine adult patients with bone marrow failure and platelet counts below 50 × 10/L were consecutively enrolled before prophylactic platelet transfusion for subclavian central venous catheter insertion. Blood samples were drawn from the patients before platelet transfusion, 1 hour, and 4 hours after completion of the transfusion. The coagulation profile was assessed by conventional hematological tests, thromboelastometry (ROTEM) assays (EXTEM and FIBTEM), multiple electrode aggregometry (Multiplate) assays including adenosine diphosphate, collagen, and thrombin receptor agonist peptide, and by flow cytometry for the platelet expression of P-selectin (CD62P) and activated glycoprotein IIb-IIIa (PAC-1). Bleeding complications were classified with a 5-grade scale, according to the Common Terminology Criteria for Adverse Events. RESULTS: Seventeen women and 22 men were included in the study. Platelet count was increased from 24 × 10/L (18-32) before to 42 × 10/L (31-50) 1 hour after transfusion (P < 0.0001) and was not significantly different 4 hours after transfusion (40 × 10/L (29-50), P = 0.047). Maximal clot firmness EXTEM was increased from 38 mm (32-45) before to 46 mm (41-52) 1 hour after transfusion (P < 0.0001) and did not change 4 hours after transfusion. Clotting time EXTEM was decreased from 58.5 seconds (50-78) beforehand to 53 seconds (45-61) 1 hour after transfusion (P = 0.0006) and was not significantly different 4 hours after transfusion (57 seconds (52-70, P = 0.025). FIBTEM results were all unchanged after transfusion. All Multiplate analyses were significantly increased after 1 hour and were not diminished 4 hours after transfusion. Four grade 1 bleeding episodes occurred, but no grade 2 to 5 bleeding could be detected. Flow cytometry analyses showed mixed results with no overall trend. CONCLUSIONS: Prophylactic platelet transfusions in thrombocytopenic patients with bone marrow failure improve hemostatic parameters on ROTEM and Multiplate by increasing the number of platelets, and not through enhancement of platelet function. Improved clotting parameters on ROTEM and platelet aggregation on Multiplate appear to persist between 1 and 4 hours after transfusion.

Albumin-induced coagulopathy is less severe and more effectively reversed with fibrinogen concentrate than is synthetic colloid-induced coagulopathy.

BACKGROUND: Synthetic colloids cause dilutional coagulopathy. The aims of our study were to determine whether the natural colloid albumin induces a lesser degree of coagulopathy compared to synthetic colloids, and the comparative effectiveness of fibrinogen concentrate to reverse coagulopathy following dilution with these solutions. METHODS: Coagulation was assessed with rotational thrombelastometry after stimulation with tissue factor (EXTEM) and in the presence of a platelet inhibitor (FIBTEM). With EXTEM, clotting time (CT), clot formation time CFT), alpha angle (AA) and maximum clot firmness (MCF) were recorded. With FIBTEM, only MCF was recorded. These parameters were assessed ex vivo in blood from 10 healthy volunteers; diluted 1:1 with either saline, Ringer's acetate, buffered/unbuffered hydroxyethyl starch, buffered/unbuffered dextran (synthetic colloids) or 5% albumin. Samples were analyzed before/after addition of fibrinogen concentrate. RESULTS: FIBTEM MCF decreased significantly upon dilution (> 50% reduced) with all colloid solutions (p ≤ 0.02), although a significantly greater coagulopathic effect was seen for samples diluted with synthetic colloids versus albumin (p ≤ 0.001). A significant reduction in the platelet component of clot strength (EXTEM MCF - FIBTEM MCF) was seen for samples diluted with synthetic colloids (p < 0.001) but not albumin (p = 0.10). Following addition of fibrinogen, FIBTEM MCF, EXTEM MCF and AA were significantly higher, and CFT was significantly shorter in samples diluted with albumin versus those treated with synthetic colloids (p ≤ 0.001). CONCLUSION: Hemodilution using albumin induced a lesser degree of coagulopathy compared with the synthetic colloids. In addition, albumin-induced coagulopathy was more effectively reversed following addition of fibrinogen concentrate compared with coagulopathy induced by synthetic colloids.

Fibrinogen and FXIII dose response effects on albumin-induced coagulopathy.

OBJECTIVES: Natural colloid albumin induces a lesser degree of dilutional coagulopathy than synthetic colloids. Fibrinogen concentrate has emerged as a promising strategy to treat coagulopathy, and factor XIII (FXIII) works synergistically with fibrinogen to correct coagulopathy following haemodilution with crystalloids. Our objectives were to examine the ability of fibrinogen and FXIII concentrates to reverse albumin-induced dilutional coagulopathy. METHODS: High and low concentrations of both fibrinogen and FXIII were used to reverse coagulopathy induced by 1:1 dilution in vitro with 5% albumin of blood samples from healthy volunteers, monitored by rotational thromboelastometry (ROTEM). RESULTS: Haemodilution with albumin significantly attenuated EXTEM maximum clot firmness (MCF), alpha angle (AA), clotting time (CT) and clot formation time (CFT), and FIBTEM MCF (p < 0.001). Following haemodilution, both doses of fibrinogen significantly corrected all ROTEM parameters (p ≤ 0.02), except the lower dose did not correct AA. Compared to the lower dose, the higher dose of fibrinogen significantly improved FIBTEM MCF and EXTEM MCF, AA and CFT (p < 0.001). The lower dose of FXIII did not significantly correct any of the ROTEM parameters, and the high dose only improved EXTEM CT (p = 0.004). All combinations of high/low concentrations of fibrinogen/FXIII significantly improved all ROTEM parameters examined (p ≤ 0.001). Fibrinogen concentration generally had a greater effect on each parameter than did FXIII concentration; the best correction of ROTEM parameters was achieved with high-dose fibrinogen concentrate and either low- or high-dose FXIII. CONCLUSIONS: Fibrinogen concentrate successfully corrected initiation, propagation and clot firmness deficits induced by haemodilution with albumin, and FXIII synergistically improved fibrin-based clot strength.