Pre-operative reference ranges for ROTEM® sigma in patients undergoing cardiac surgery: a secondary analysis of two prospective trial cohorts

INTRODUCTION

Rotational thromboelastometry (ROTEM®) is used widely in cardiac surgery. Reference ranges are derived from healthy volunteers but may not be interchangeable with those from patients undergoing cardiac surgery. Furthermore, sex and age seem to influence rotational thromboelastometry profiles. We performed a secondary analysis of two prospective observational study cohorts from a single centre in the Netherlands, which establishes pre-operative ROTEM® sigma reference ranges for adult patients undergoing cardiac surgery and examines sex- and age-specific variations.

METHODS

Reference ranges (2.5-97.5th percentiles) were compared with those reported by the manufacturer by calculating 95%CIs around the percentiles. Sex- and age-specific variations were evaluated similarly by creating subgroups (comparing males with females and different age groups) and calculating the 95%CIs for the ranges in each subgroup. Non-overlapping CIs indicated statistically significant different ranges.

RESULTS

We included 381 patients in the analysis. Differences were found in ROTEM sigma reference ranges compared with those stated by the manufacturer: EXTEM and FIBTEM clot firmness upper limits were higher, and clotting time ranges in EXTEM and INTEM were wider. The lower limit of LI60 EXTEM was lower. When comparing males (n = 260) and females (n = 121), female patients had shorter CT EXTEM and higher A5, A10 and MCF in EXTEM and FIBTEM, but the reference ranges were not significantly different. No differences in medians or reference bounds were found across four age categories, divided by quartiles.

DISCUSSION

Reference ranges for patients undergoing cardiac surgery differed from the manufacturer reference ranges. Pre-operatively, female patients exhibited a slightly more hypercoagulable ROTEM profile than males when comparing medians, though the reference ranges were similar. No differences were found across age categories. Cardiovascular-specific, but not sex- or age-specific ROTEM sigma reference ranges might be needed.

Investigation of Blood Coagulation Using Impedance Spectroscopy: Toward Innovative Biomarkers to Assess Fibrinogenesis and Clot Retraction

This study focused on a coagulation assessment based on the novel technique of blood-impedance-magnitude measurement. With the impedance characterization of recalcified human blood, it was possible to identify two significative biomarkers (i.e., measurable indicators) related to fibrin formation (1st marker) and clot retraction (2nd marker). The confocal microscopy of clotting blood provided a complete visual analysis of all the events occurring during coagulation, validating the significance of the impedance biomarkers. By analyzing the impedance phase angle (Φ) of blood during coagulation, as well as those of the clot and serum expelled after retraction, it was possible to further clarify the origin of the 2nd marker. Finally, an impedance-magnitude analysis and a rotational thromboelastometry test (ROTEM®) were simultaneously performed on blood sampled from the same donor; the results pointed out that the 1st marker was related to clotting time. The developed technique gives rise to a comprehensive and evolutive insight into coagulation, making it possible to progressively follow the whole process in real time. Moreover, this approach allows coagulation to be tested on any materials' surface, laying the ground for new studies related to contact coagulation, meaning, thrombosis occurring on artificial implants. In a near future, impedance spectroscopy could be employed in the material characterization of cardiovascular prostheses whose properties could be monitored in situ and/or online using effective biomarkers.

Rotational thromboelastometry (ROTEM® ) in gestational diabetes mellitus and coagulation in healthy term pregnancy: A prospective observational study in Australia

BACKGROUND

Rotational thromboelastometry (ROTEM^® ) is a point-of-care test of coagulation. ROTEM^® -defined hypercoagulability has been identified in pregnant women and in non-pregnant patients with diabetes mellitus. Pregnancy is known to be a hypercoagulable state, but the influence of gestational diabetes mellitus (GDM) on coagulation is unknown.

AIM

The aim of this study was to assess the combined effect of pregnancy and GDM on coagulation using ROTEM^® and to compare this to healthy pregnant women presenting for elective caesarean delivery.

MATERIALS AND METHODS

Ethics approval was granted for recruitment of women presenting for elective caesarean delivery. Women with pre-existing conditions affecting coagulation were excluded. Group N included health pregnant women at term and Group G included pregnant women at term with GDM. Data regarding GDM management and glycaemic control were collected. Poor glycaemic control was defined by markers of accelerated fetal growth and elevated fasting or postprandial blood glucose levels. The ROTEM^® parameters (extrinsically activated thromboelastometric test (EXTEM) / fibrin polymerisation test (FIBTEM) amplitude at five minutes, coagulation time, maximum clot firmness and clot formation time) were compared between the two groups using Student's t-test.

RESULTS

There were 75 women in Group N and 21 women in Group G. Mean age and median body mass index values were comparable for both groups. There were no statistical differences found between the EXTEM and FIBTEM parameters analysed for the two groups.

CONCLUSIONS

There was no association between GDM and increased hypercoagulability as demonstrated by ROTEM^® parameters in healthy pregnant women presenting for elective caesarean delivery at term.

Combined Administration of Fibrinogen and Factor XIII Concentrate Does Not Improve Dilutional Coagulopathy Superiorly Than Sole Fibrinogen Therapy: Results of an In-Vitro Thrombelastographic Study

The early administration of fibrinogen has gained wide acceptance for the treatment of major hemorrhage, whereas the substitution of coagulation factor XIII (FXIII) is only supported by a low level of evidence. This study aimed to answer the question of whether a combined therapy of fibrinogen/FXIII substitution performs superiorly to sole fibrinogen administration in the treatment of dilutional coagulopathy. An in-vitro model of massive transfusion was used to compare the effect of combined fibrinogen/FXIII administration to that of sole fibrinogen therapy for the treatment of dilutional coagulopathy. For this purpose, the blood of red blood cell concentrates, fresh frozen plasma, and platelet concentrates were reconstituted in a ratio of 4:4:1, and then diluted with gelatin by 20% and 40%, respectively. Clot formation and stability were analyzed by thrombelastography. Both sole fibrinogen therapy (equivalent to 50 mg/kg) and the combined administration of fibrinogen (equivalent to 50 mg/kg) and FXIII (equivalent to 75 International Units (IU)/kg) increased fibrinogen-dependent mean clot firmness independently of the degree of dilution (20% dilution: 7 (6.3–7.8) mm; 20% dilution fibrinogen: 13.5 (13–17.3) mm; 20% dilution fibrinogen/FXIII: 16.5 (15.3–18.8) mm; 40% dilution: 3 (2–3.8) mm; 40% dilution fibrinogen: 8 (7–11.3) mm; 40% dilution fibrinogen/FXIII: 10 (8.3–11.8) mm; all p < 0.01). However, no differences were identified between the two treatment arms. Compared to fibrinogen therapy, no beneficial effect of the combined administration of fibrinogen and FXIII for the treatment of dilutional coagulopathy was detected in this in-vitro massive transfusion model. The result was independent of the degree of dilution.

Global Coagulation Assays in Transgender Women on Oral and Transdermal Estradiol Therapy

CONTEXT

The thrombotic effects of estradiol therapy in transgender women are unclear. Global coagulation assays (GCA) may be better measures of hemostatic function compared with standard coagulation tests.

OBJECTIVE

To assess the GCA profiles of transgender women in comparison to cisgender controls and to compare how GCA differ between routes of estradiol therapy in transgender women.

DESIGN

Cross-sectional case-control study.

SETTING

General community.

PARTICIPANTS

Transgender women, cisgender male and cisgender female controls.

MAIN OUTCOME MEASURES

Citrated blood samples were analyzed for (i) whole blood thromboelastography (TEG®5000), (ii) platelet-poor plasma thrombin generation (calibrated automated thrombogram); and (iii) platelet-poor plasma fibrin generation (overall hemostatic potential assay). Mean difference (95% confidence intervals) between groups are presented.

RESULTS

Twenty-six transgender women (16 oral estradiol, 10 transdermal estradiol) were compared with 98 cisgender women and 55 cisgender men. There were no differences in serum estradiol concentration (P = 0.929) and duration of therapy (P = 0.496) between formulations. Transgender women demonstrated hypercoagulable parameters on both thromboelastography (maximum amplitude + 6.94 mm (3.55, 10.33); P < 0.001) and thrombin generation (endogenous thrombin potential + 192.62 nM.min (38.33, 326.91); P = 0.009; peak thrombin + 38.10 nM (2.27, 73.94); P = 0.034) but had increased overall fibrinolytic potential (+4.89% (0.52, 9.25); P = 0.024) compared with cisgender men. No significant changes were observed relative to cisgender women. Route of estradiol delivery or duration of use did not influence the GCA parameters.

CONCLUSION

Transgender women on estradiol therapy demonstrated hypercoagulable GCA parameters compared with cisgender men with a shift towards cisgender female parameters. Route of estradiol delivery did not influence the GCA parameters.

Reference intervals for rotational thromboelastometry measurements using the ROTEM® delta device in dogs

Aims of the present study were to define reference intervals for viscoelastic analyses of canine haemostasis using the ROTEM® delta analyser, and as a secondary aspect to determine the precision (repeatability) of this method. Blood samples from 125 clinically healthy dogs were included. Measurements were performed with commercially available activating reagents (ex-tem, in-tem and kaolin solution) as well as without activation. Additional fourfold measurements were done in 3 of the normal blood samples and in 3 samples with haemostatic alterations to evaluate the precision of the method. Coefficients of variation (CVs) for most of the ROTEM variables were < 10%. Clot formation time and maximum clot elasticity showed a wide inter-individual variation in comparison with alpha angle and maximum clot firmness. A multivariate analysis on various ROTEM parameters revealed particularly a significant influence of neuter status and a significant interrelationship between the factors sex and neuter status for measurements with different activating reagents. These results reflected the fact that significant differences occurred only between intact and neutered females, but not in males. No or only occasionally significant differences were found between groups of sex, age, and size. In conclusion, CVs demonstrated that the method delivers repeatable results in canine citrated whole blood. Established reference intervals should deliver valuable orientation for the evaluation of viscoelastic properties of clotting whole blood in dogs using the ROTEM delta analyser. Neuter status in females appeared to be the most relevant influencing factor and should be considered for the interpretation of ROTEM delta test results.

A preliminary study using rotational thromboelastometry to investigate perioperative coagulation changes and to identify hypercoagulability in obese patients undergoing total hip or knee replacement

Surgery and obesity are known risk factors for thromboembolic events due to the presence of a hypercoagulable state. Rotational thromboelastometry is a viscoelastic assay that can provide a measure of hypercoagulability via a comprehensive assessment of the coagulation process. This prospective study investigates haemostatic changes over time, presence of hypercoagulability and the association between body mass index and thromboelastometry results in patients undergoing major orthopaedic surgery. Fifty adult patients undergoing total hip or knee replacement surgery had serial thromboelastometry measures performed prior to and following surgery, and on postoperative days 1 and 3. A hypercoagulable state, defined by an ExTEM maximum clot firmness G score ≥11 dyne/cm2, was present in 28% of the patients at baseline. The mean ExTEM maximum clot firmness G score increased by an average of three units from 10 (95% confidence interval (CI) 9–11) dyne/cm2 at baseline to 13 (95% CI 13–14) dyne/cm2 on postoperative day 3, with 85% of patients having a G score ≥11 dyne/cm2. A decrease in ExTEM and InTEM clot formation time and an increase in ExTEM, InTEM and FibTEM clot amplitude at 10 minutes, alpha angle and maximum clot firmness were observed by postoperative day 3 ( P <  0.001). There was no significant difference in the mean thromboelastometry values between patients with a body mass index <35 kg/m2or ≥35 kg/m2. Although a modest association between body mass index and the ExTEM maximum clot firmness G score was observed with exploratory data analysis, further study is required in a large cohort to test the effects of confounders, validate these findings, and determine their clinical importance.

A comparison of the new ROTEM® sigma with its predecessor, the ROTEMdelta

Thromboelastometry point-of-care coagulation testing facilitates optimised management of bleeding. Previous thromboelastometry systems required the blood sample and liquid reagents to be pipetted in several manual steps by trained personnel. The ROTEMsigma coagulation analyser is a fully automated point-of-care device. We aimed to assess the reference ranges of the new device and to compare the results with those of the predecessor device, the ROTEMdelta. We took blood from healthy volunteers and from hyper- or hypocoagulable patients; blood samples from healthy volunteers served to determine reference ranges for the most important parameters for the ROTEMsigma: CT_EXTEM 48-61 s; A5_EXTEM 30-51 mm; MCF_EXTEM 54-70 mm; CT_INTEM 138-174 s; MCF_INTEM 51-67 mm and MCF_FIBTEM 5-24 mm. We then used blood samples from patients to compare the results obtained between the old and the new device. We found a strong correlation between the same tests performed on two ROTEMsigma devices and between the ROTEMsigma and the ROTEMdelta with respect to the determination of thromboelastometry parameters of hyper- and hypocoagulable patients (all p < 0.001 and R > 0.8). Performance evaluation for the ROTEMsigma device showed very high precision (R > 0.99, p < 0.001). Our reference ranges can serve as an important aid for other hospitals using this new device.

Validation of a modified thromboelastometry approach to detect changes in fibrinolytic activity

Background

Thus far, validated whole blood assays used in in vitro fibrinolysis experiments using thromboelastometry (ROTEM) are lacking or have yet to be tested in humans.

The objective was first, to establish a standardized modified ROTEM approach to detect both hypo- and hyperfibrinolysis. And second, to perform a technical and clinical validation of the assay.

Methods

Blood was used of healthy volunteers, patients with sepsis, patients after cardiothoracic surgery, pregnant women, and cirrhotic liver disease patients. A whole blood tissue factor (TF) activated ROTEM assay with and without the addition of recombinant tissue plasminogen activator (rTPA) was developed. Plasma fibrinolysis determinants were measured in all volunteers and patients.

Results

Thirty five pM TF and additions of 125 and 175 ng/ml rTPA resulted in full lysis within 60 min in healthy volunteers. Coefficients of variation were below 10 % without and below 20 % with rTPA addition. In sepsis the hypofibrinolytic ROTEM profiles with 175 ng/ml rTPA were in line with the plasma determinants (high PAI-1, high fibrinogen, low tPA activity, and high d-dimers). After cardiothoracic surgery, reduced fibrinogen and platelet levels accounted for the reduced maximum clot firmness. The hypofibrinolytic profile is attributed to tranexamic acid use and elevated PAI-1 levels. The lowest rTPA concentration in cirrhosis resulted in hyperfibrinolysis in only few of the patients. In pregnancy normal profiles were found.

Discussion

Our high rTPA concentration demonstrates hypofibrinolytic profiles adequately in sepsis and after cardiothoracic surgery. Our low rTPA concentration of 125 ng/ml seems too high for demonstrating hyperfibrinolysis in cirrhotic liver disease.

Conclusions

We were able to present a validated whole blood ROTEM approach to fibrinolysis testing using added rTPA, which can be of added value next to classical plasma based fibrinolysis assays.

Effect of synthetic colloid administration on coagulation in healthy dogs and dogs with systemic inflammation

Background

Synthetic colloids are often used during fluid resuscitation and affect coagulation.

Objective

To compare the effects of an isotonic crystalloid and synthetic colloid on coagulation in healthy dogs and dogs with systemic inflammation.

Animals

Sixteen adult purpose‐bred Beagles.

Methods

Randomized, placebo‐controlled, blinded study. Dogs were randomized into one of two groups receiving fluid resuscitation with either 40 mL/kg IV 0.9% NaCl or tetrastarch after administration of lipopolysaccharide or an equal volume of placebo. After a 14‐day washout period, the study was repeated such that dogs received the opposite treatment (LPS or placebo) but the same resuscitation fluid. Blood samples were collected at 0, 1, 2, 4, and 24 hours for measurement of coagulation variables.

Results

Administration of either fluid to healthy dogs and dogs with systemic inflammation resulted in similar increases in prothrombin time and activated clotting time. In comparison to saline administration, tetrastarch administration resulted in significantly decreased R (P = .017) in healthy dogs, as well as significantly increased activated partial thromboplastin time (P ≤ .016), CL30% (P ≤ .016), and K (P < .001) and significantly decreased platelet count (P = .019), α (P ≤ .001), MA (P < .001), and von Willebrand factor antigen (P < .001) and collagen binding activity (P ≤ .003) in both healthy dogs and dogs with systemic inflammation.

Conclusions and Clinical Importance

Tetrastarch bolus administration to dogs with systemic inflammation resulted in a transient hypocoagulability characterized by a prolonged activated partial thromboplastin time, decreased clot formation speed and clot strength, and acquired type 1 von Willebrand disease.

Thromboelastometry: A contribution to perioperative free-flap management

BACKGROUND

Microvascular tissue transfer is a fundamental part of reconstructive surgery. Different perioperative anticoagulation regimens exist, influencing hemostatic parameters. Since bleeding and thrombosis are major reasons for revision procedures and flap loss, current practice regarding anticoagulative treatment needs further refinement. Thromboelastometry has been demonstrated as worthwhile in the determination of alterations of the anticoagulation cascade. We evaluated this aspect of thromboelastometry for free flap surgery.

METHODS

Thirty-five patients undergoing free-flap surgery were enrolled in this study. Blood samples were obtained at three time points: at the beginning of surgery, at time of anastomosis and after 24 h. At each time point, thromboelastometry with special regard to clotting times for the intrinsic and extrinsic paths of coagulation was immediately performed. Global coagulation markers and clinical parameters were collected simultaneously.

RESULTS

Hemostatic changes were deducible using thromboelastometry perioperatively. Measured parameters differed significantly over time (p < 0.05). Heparin therapy showed a significant effect on the measured slope of INTEM-clotting times (p < 0.001). Altered values of thromboelastometry suggested non-inferiority to standard testing. Neither standard testing nor thromboelastometry were capable of predicting adverse events such as thrombosis, bleeding or flap loss (p > 0.05).

CONCLUSIONS

Thromboelastometry monitors hemostatic effects almost in real-time and could serve as a supplementary tool in microvascular tissue transfer once its use has been standardized. The utilization of thromboelastometry allows for assessment of the anticoagulation needs of individual patients undergoing free flap surgery, which is frequently accompanied by hemostatic changes in the perioperative setting. Our findings implicate further validation of thromboelastometry in free-flap surgery.

Prospective evaluation of blood coagulability and effect of treatment in patients with stroke using rotational thromboelastometry

BACKGROUND

Stroke is the second largest cause of death worldwide. Abnormalities in hemostasis play an important role in the pathophysiology of ischemic stroke (IS). These hemostatic defects can be detected using rotational thromboelastometry (ROTEM) as a global method of measuring coagulation. This study assessed the effects of IS on blood hypercoagulability using ROTEM method, before and subsequent to therapeutic interventions.

METHODS

In a prospective observational cohort study, whole blood coagulation using ROTEM, along with full blood count and standard coagulation tests, were compared between patients with IS and an age-matched control group of healthy volunteers. Further assessment took place at 2-4 hours and at 24 hours in the stroke group after therapy to assess the effects of therapeutic intervention.

RESULTS

Seventy-two patients with IS were age-matched to 71 healthy subjects. Clotting time (CT) INTEM (P = .01) and maximum clot firmness (MCF) INTEM (P = .02) were significantly different between stroke patients at baseline and healthy subjects, but this difference disappeared when controlled for by smoking status. There was no association between ROTEM parameters and time from stroke symptom onset or stroke severity as reflected in The National Institute of Health Stroke Scale score. Significant but small changes in the values of MCF-EXTEM, clot formation time (CFT) EXTEM, and alpha-EXTEM CT were observed after therapeutic intervention (thrombolysis or aspirin treatment).

CONCLUSIONS

ROTEM testing does not seem to detect a hypercoagulable state in patients with IS. Nonetheless, some ROTEM parameters had a small change after antiplatelet therapy or thrombolysis.

Interchangeability of rotational elastographic instruments and reagents

BACKGROUND

Viscoelastic measurements are frequently being used in clinical and research settings for a rapid assessment of the hemostatic processes of blood clot formation and degradation. These measurements are being performed on either of two instruments (TEG and ROTEM) using their proprietary reagents. Standardization between the instruments and the reagents has been lacking but is necessary to compare results across instruments. In this study, we perform a crossover analysis between the TEG and ROTEM instruments using proprietary reagents from each manufacturer.

METHODS

We tested three sets of reagents as follows: (1) in-tem and ex-tem (Tem International GmbH); (2) kaolin and RapidTEG (Haemonetics); (3) a well-characterized control recombinant tissue factor-phospholipid reagent. Blood was drawn from six healthy donors, and each reagent was run concurrently in the TEG and ROTEM instruments. The volume of commercial reagent and calcium used was adjusted for crossover measurements to maintain the same concentration of each reagent in the blood. The outputs of clot time, rate of clot formation, and maximum firmness of the clot of the ROTEM and the TEG tracings were evaluated.

RESULTS

The in-tem and RapidTEG reagents showed no disparity between instruments for any parameter. Significant differences between the instruments were found in the α angle and maximum firmness of the clot for ex-tem and kaolin reagents as well as in the clot time and maximum firmness of the clot for the recombinant tissue factor-phospholipid reagent.

CONCLUSION

Although significant differences were observed for some parameters, the magnitudes were small compared with the differences between tests or the normal range variation in parameter values observed for these tests. These findings indicate that the instruments are more interchangeable than previously reported.