The predictive value of modified computerized thromboelastography and platelet function analysis for postoperative blood loss in routine cardiac surgery

Viscoelastic Testing Methods

Viscoelastic testing methods examine the real-time formation of a clot in a whole blood sample, and include thromboelastography (TEG), rotational thromboelastometry (ROTEM), and several other testing platforms. They allow for concurrent assessment of multiple aspects of clotting, including plasmatic coagulation factors, platelets, fibrinogen, and the fibrinolytic pathway. This testing is rapid and may be performed at the point-of-care, allowing for prompt identification of coagulopathies to guide focused and rational administration of blood products as well as the identification of anticoagulant effect. With recent industry progression towards user-friendly, cartridge-based, portable instruments, viscoelastic testing has emerged in the 21st century as a powerful tool to guide blood transfusions in the bleeding patient, and to identify and treat both bleeding and thrombotic conditions in many operative settings, including trauma surgery, liver transplant surgery, cardiac surgery, and obstetrics. In these settings, the use of transfusion algorithms guided by viscoelastic testing data has resulted in widespread improvements in patient blood management as well as modest improvements in select patient outcomes. To address the increasingly wide adoption of viscoelastic methods and the growing number of medical and laboratory personnel tasked with implementing, performing, and interpreting these methods, this chapter provides an overview of the history, physiology, and technology behind viscoelastic testing, as well as a practical review of its clinical utility and current evidence supporting its use. Also included is a review of testing limitations and the contextual role played by viscoelastic methods among all coagulation laboratory testing.

Viscoelastic testing: Critical appraisal of new methodologies and current literature

United States Food and Drug Administration (FDA)-approved viscoelastic testing (VET) methodologies have significantly changed in the last 10 years, with the availability of cartridge-based VET. Some of these cartridge-based methodologies use harmonic resonance-based clot detection. While VET has always allowed for the evaluation of real-time clot formation, cartridge-based VET provides increased ease of use as well as greater portability and robustness of results in out-of-laboratory environments. Here we review the use of VET in a variety of clinical contexts, including cardiac surgery, trauma, liver transplant, obstetrics, and hypercoagulable states such as COVID-19. As of now, high quality randomized trial evidence for new generation VET (TEG 6s, HemoSonics Quantra, ROTEM sigma) is limited. Nevertheless, the use of VET-guided transfusion algorithms appears to result in reduced blood usage without worsening of patient outcomes. Future work comparing the new generation VET instruments and continuing to validate clinically important cut-offs will help move the field of point-of-care coagulation monitoring forward and increase the quality of transfusion management in bleeding patients.

Emerging technology for early detection and management of postpartum hemorrhage to prevent morbidity

Despite advances in hemorrhage detection and management, postpartum hemorrhage remains the single leading cause of maternal death worldwide. Within the United States, hemorrhage is the leading cause of maternal death on the day of delivery and within the first week after delivery. Blood transfusion after hemorrhage represents a large proportion of severe maternal morbidity during and after delivery. Blood loss during delivery has historically been assessed visually by inspecting soiled pads, linens, and laparotomy sponges. These methods underestimate the volume of blood loss by as much as 40%, becoming increasingly inaccurate as blood loss increases. Young, healthy obstetrical patients compensate for blood loss via peripheral vasoconstriction, maintaining heart rate and blood pressure in a normal range until over 1 L of blood has been lost. A significant decrease in blood pressure along with marked tachycardia (>120 bpm) may not be seen until 30% to 40% of blood volume has been lost, or 2.0 to 2.6 L in a healthy term pregnant patient, after which the patient may rapidly decompensate. In resource-poor settings especially, the narrow window between the emergence of significant vital sign abnormalities and clinical decompensation may prove catastrophic. Once hemorrhage is detected, decisions regarding blood product transfusion are routinely made on the basis of inaccurate estimates of blood loss, placing patients at risk of underresuscitation (increasing the risk of hemorrhagic shock and end-organ damage) or overresuscitation (increasing the risk of transfusion reaction, fluid overload, and alloimmunization). We will review novel technologies that have emerged to assist both in the early and accurate detection of postpartum hemorrhage and in decisions regarding blood product transfusion.

Are Risk Factors for Postoperative Significant Hemorrhage following Total Knee Arthroplasty Potentially Modifiable? A Retrospective Cohort Study

Total knee arthroplasty (TKA) is the treatment of choice for end-stage osteoarthritis (OA) of the knee, because it alleviates pain and restores function of the knee. However, TKA-associated hemorrhage and subsequent anemia remain a concern. Most previous studies have defined meaningful postoperative bleeding as blood loss > 500 mL or hemoglobin (Hb) drop > 20 g/L. Therefore, we defined significant hemorrhage as a postoperative Hb drop more than 20 g/L in this study, and we investigated possible risk factors related to significant hemorrhage in TKA and whether these risk factors are modifiable. This retrospective study was conducted through a comprehensive review of the perioperative records of patients with OA of the knee who underwent TKA between January 2009 and December 2015 at our hospital. Patients were allocated into two groups: patients in Group A had their Hb drop ≤ 20 g/L; patients in Group B had their Hb drop > 20 g/L. Factors analyzed included sex, age, body mass index (BMI), the American Society of Anesthesiologists (ASA) classification, comorbidities, preoperative platelet count, use of tranexamic acid (TXA), operation time, and type of anesthesia. A total of 3350 patients met the criteria for analysis, with 1782 patients allocated to Group A and 1568 patients to Group B. Five independent risk factors for significant hemorrhage were identified: male sex (odds ratio(OR), 1.29; 95% confidence interval(CI), 1.08−1.53; p = 0.005), age (OR, 1.02; 95% CI, 1.01−1.03; p = 0.001), use of TXA (OR, 0.39; 95% CI, 0.34−0.45; p < 0.001), spinal anesthesia versus general anesthesia (OR, 0.71; 95% CI, 0.56−0.90; p = 0.004), and preoperative platelet count (OR, 0.96; 95% CI, 0.93−0.98; p = 0.001). Of these identified risk factors, preoperative platelet count, use of TXA, and spinal anesthesia are modifiable. These potentially modifiable risk factors need to be taken into consideration when making both the perioperative care and anesthesia plan by surgeons and anesthesiologists, especially in patients at risk of significant hemorrhage.

Interaction of heparin and protamine in presence of overdosage: in vitro study

BACKGROUND

Heparin is used for anticoagulation during cardiopulmonary bypass. After weaning from bypass, protamine is administered to neutralize the effects of heparin and thus reestablish hemostasis. Rotational thrombelastometry has been shown to discriminate between heparin and other impairing effects on coagulation. We analyzed the interaction of heparin and protamine under different conditions of overdosage in an in-vitro trial.

METHODS

Blood samples were taken from 17 healthy volunteers, separated, and spiked in vitro with heparin, protamine for heparin neutralization, an overdosage of protamine, and two dosages of re-heparinization to evaluate heparin effects under the condition of protamine overdosage. All samples were analyzed in a standard ROTEM rotational thromboelastometry device after intrinsic activation with and without addition of heparinase. Coagulation time, maximum clot firmness, and clot formation time were recorded.

RESULTS

Heparin led to prolongation of coagulation and clot formation times in the test without heparinase. Adequate protamine addition normalized the test, and overdosage of protamine led to significant prolongation of both times. Addition of heparin in the presence of protamine overdosage normalized these parameters.

CONCLUSION

We reconfirmed that the ROTEM device enables discrimination of the effects heparin and protamine on coagulation and detection of the coagulation-impairing effects of protamine overdosage. Furthermore, we were able to show a positive effect on coagulation times by heparin in the presence of protamine overdosage. Because this was an in-vitro study, these findings need to be confirmed in vivo, requiring further research.

The Utility of Thromboelastography to Guide Blood Product Transfusion

OBJECTIVES

To provide an overview of the clot viscoelastic testing technology and to describe its utility in guiding blood product transfusions.

METHODS

A case scenario will be discussed as well as interpretation of thromboelastography (TEG) tracings. In addition, literature examining the utility of viscoelastic testing in guiding patient management and blood product transfusions will be reviewed.

RESULTS

TEG/rotational thromboelastometry (ROTEM) is useful in evaluating clot kinetics in trauma and acutely bleeding patients. TEG/ROTEM parameters are reflective of values measured using standard coagulation assays; however, TEG/ROTEM parameters are more rapidly available and more costly. TEG and ROTEM are used in three main settings: cardiac surgery, liver transplantation, and trauma to assess global hemostasis and administration of blood products.

CONCLUSIONS

TEG/ROTEM can be helpful in guiding resuscitation and blood product transfusion. Several studies have demonstrated a reduction in transfusion of blood components with TEG/ROTEM; however, other studies have suggested that TEG/ROTEM is not clinically effective in guiding transfusion.

Thromboelastography-guided transfusion in dogs with hypocoagulable disorders: a case series

BACKGROUND

Thromboelastography (TEG) is a global whole blood hemostasis assay which includes plasma as well as cellular components of hemostasis in the analysis and follows the quality and dynamics of clot development, stabilization, and lysis. In human medicine TEG is also a valuable asset in the therapeutic setting, allowing evaluation of the effect of transfusion therapy in vitro. This case series describes the use of TEG as a guiding tool for transfusion therapy in four dogs with hypocoagulable hemostatic disorders.

CASE PRESENTATION

Four dogs presented with hypocoagulable disorders of hemostasis, diagnosed as rodenticide intoxication, angiostrongylosis, disseminated intravascular coagulation following severe systemic inflammation, and immune-mediated thrombocytopenia, respectively. TEG was used as a diagnostic tool as well as a guiding tool in the decision of whether or not, and in what dose, fresh frozen plasma would be of benefit in the treatment protocol for each dog.

CONCLUSIONS

TEG may be applied in the therapeutic setting as a means to tailor individual patient transfusion therapy in critically ill dogs with hypocoagulable states.

The velocity curve of the clotting waveform of rotational thromboelastometry predicts bleeding after cardiac surgery but conventional rotational thromboelastometric parameters do not

BACKGROUND

Early detection of a risk of postoperative bleeding is essential in cardiac surgery patients. The aim of the present study was to evaluate the utility of the first derivative curve (the V-curve) of the clotting waveform of rotational thromboelastometry (ROTEM) in terms of predicting bleeding after cardiac surgery.

METHODS

We retrospectively analysed 534 cardiac surgery patients. We used the chest tube output during the stay in the intensive care unit to divide patients into a higher blood loss group (HBL group; the fourth quartile) and a lower blood loss group (LBL group; the lower quartiles). We performed multivariable logistic regression using the V-curve parameters and potential confounders including conventional ROTEM parameters.

RESULTS

In the multivariable model, the adjusted odds ratios for HBL of patients with a lower maximum clotting velocity (MaxVel ≤9 mm*100 s-1) as revealed by extrinsically activated ROTEM (EXTEM), and the area under the velocity curve (AUC ≤988 mm*100) of the fibrin-based extrinsically activated ROTEM (FIBTEM), both measured at skin closure in the end of surgery, were 1.78 (95% CI 1.03 to 3.07) and 2.14 (95% CI 1.20 to 3.82), respectively. However, conventional ROTEM parameters were not included in the final model. Additionally, lower EXTEM MaxVel and FIBTEM AUC values were associated with the need for a higher transfusion volume, longer postoperative intensive care unit and hospital stays, and more frequent re-exploration to control bleeding.

CONCLUSIONS

The ROTEM V-curve parameters can predict postoperative bleeding and clinical outcomes after cardiac surgery.

Transfusion Medicine and Coagulation Management in Organ Transplantation

Organ transplantation recipients present unusual challenges with regard to blood transfusion. Although this patient population requires a larger proportion of blood product resources, liberal transfusion of allogeneic blood products can lead to a plethora of complications. Recent trends suggest that efforts to minimize bleeding, conserve products, and target transfusion to specific deficits and needs are increasingly becoming the standard practice; these must all occur with optimization of graft function and preservation in mind. With newer monitoring modalities and factor concentrates, the approach toward transfusion and bleeding in organ transplantation has rapidly improved in recent years.

Platelet Aggregometry Testing: Molecular Mechanisms, Techniques and Clinical Implications

Platelets play a fundamental role in normal hemostasis, while their inherited or acquired dysfunctions are involved in a variety of bleeding disorders or thrombotic events. Several laboratory methodologies or point-of-care testing methods are currently available for clinical and experimental settings. These methods describe different aspects of platelet function based on platelet aggregation, platelet adhesion, the viscoelastic properties during clot formation, the evaluation of thromboxane metabolism or certain flow cytometry techniques. Platelet aggregometry is applied in different clinical settings as monitoring response to antiplatelet therapies, the assessment of perioperative bleeding risk, the diagnosis of inherited bleeding disorders or in transfusion medicine. The rationale for platelet function-driven antiplatelet therapy was based on the result of several studies on patients undergoing percutaneous coronary intervention (PCI), where an association between high platelet reactivity despite P2Y12 inhibition and ischemic events as stent thrombosis or cardiovascular death was found. However, recent large scale randomized, controlled trials have consistently failed to demonstrate a benefit of personalised antiplatelet therapy based on platelet function testing.

A Novel Device for the Evaluation of Hemostatic Function in Critical Care Settings

Major surgical procedures often result in significant intra- and postoperative bleeding. The ability to identify the cause of the bleeding has the potential to reduce the transfusion of blood products and improve patient care. We present a novel device, the Quantra Hemostasis Analyzer, which has been designed for automated, rapid, near-patient monitoring of hemostasis. The Quantra is based on Sonic Estimation of Elasticity via Resonance Sonorheometry, a proprietary technology that uses ultrasound to measure clot time and clot stiffness from changes in viscoelastic properties of whole blood during coagulation. We present results of internal validation and analytical performance testing of the technology and demonstrate the ability to characterize the key functional components of hemostasis.

Thromboelastographic profile of goat blood after the experimental injury of the femoral artery and use of QuikClot gauze and Celox gauze dressings

The aim of this study was to evaluate the suitability of thromboelastometry for the analysis of blood test results in goats after the use of hemostatic dressings to control massive bleeding. The study was carried out on 12 goats, 6 animals in each of two subgroups. In all experimental animals incision of the femoral artery was performed, and bleeding was controlled with QuikClot gauze in the first group and Celox gauze in the second group. Dressings were applied for 60 minutes. Blood samples for thromboelastometry were collected from the jugular vein before the incision and 60 min after the application of a dressing. Clotting time (CT), clot formation time (CFT), maximum clot firmness (MCF) and α angle (°) were measured in three standard ROTEM assays (system with generation of reaction curve, numerical parameters and size of the blood clot): intrinsic coagulation pathway (INTEM), extrinsic coagulation pathway (EXTEM) and functional fibrinogen (FIBTEM). Complete hemostasis of the injured femoral artery was found in all goats. No significant differences between pre- and post-incision thromboelastometric parameters were found in any tests in any of the groups, which indicates that the use of dressings was not associated with blood coagulation disorders. This study is the first to describe the use of thromboelastometry in goats for the assessment of clot formation and hemostatic disorders.

Platelet reactivity in thromboelastometry. Revision of the FIBTEM test: a basic study

This study aimed to investigate modifications to the FIBTEM test to better assess fibrinogen levels and the quality of fibrin polymerization in citrated blood using Multiplate impedance aggregometry to verify platelet inhibition. Blood samples from 26 healthy volunteers were subjected to thromboelastometry studies (EXTEM/FIBTEM tests) in accordance with the standard study protocol (cytochalasin D) and according to a modified protocol (synthetic IIbIIIa receptor antagonist vs. acetylsalicylic acid [ASA] + synthetic IIbIIIa receptor antagonist instead of cytochalasin D). Independent of thromboelastometry, Multiplate impedance aggregometry was used to assess the degree of restriction by the platelet blocked with the following treatments: (1) cytochalasin D, (2) synthetic IIbIIIa antagonist or (3) ASA + synthetic IIbIIIa antagonist to assess the aggregation response to activation with an agonist (ADP, collagen, thrombin receptor activating peptide-6 [TRAP-6], and arachidonic acid). Via aggregometry, cytochalasin D more weakly inhibited platelet aggregation than simultaneous administration of the -IIbIIIa receptor antagonist with ASA. However, total platelet aggregation inhibition was observed after simultaneous administration of cytochalasin D combined with a synthetic IIbIIIa receptor antagonist. In the thromboelastometry, a significant decrease of the A10, A20 and MCF parameters were observed in the EXTEM/FIBTEM tests after they were modified by the addition of a synthetic IIbIIIa receptor antagonist alone or in combination with ASA. In conclusion, in this Multiplate- and ROTEM-based laboratory approach, a two-way blockade (IIbIIIa-antagonist + cytochalasine D) was sufficient to completely inhibit procoagulant platelet function as observed by aggregometry and thromboelastometry.

Coagulation competence for predicting perioperative hemorrhage in patients treated with lactated Ringer's vs. Dextran--a randomized controlled trial

BACKGROUND

Perioperative hemorrhage may depend on coagulation competence and this study evaluated the influence of coagulation competence on blood loss during cystectomy due to bladder cancer.

METHODS

Forty patients undergoing radical cystectomy were included in a randomized controlled trial to receive either lactated Ringer's solution or Dextran 70 (Macrodex ®) that affects coagulation competence.

RESULTS

By thrombelastography evaluated coagulation competence, Dextran 70 reduced "maximal amplitude" (MA) by 25 % versus a 1 % reduction with the administration of lactated Ringer's solution (P <0.001). Blinded evaluation of the blood loss was similar in the two groups of patients - 2339 ml with the use of Dextran 70 and 1822 ml in the lactated Ringer's group (P = 0.27). Yet, the blood loss was related to the reduction in MA (r = -0.427, P = 0.008) and by multiple regression analysis independently associated with MA (P = 0.01). Thus, 11 patients in the dextran group (58 %) developed a clinical significant blood loss (>1500 ml) compared to only four patients (22 %) in the lactated Ringer's group (P = 0.04).

CONCLUSIONS

With the use of Dextran 70 vs. lactated Ringer's solution during cystectomy, a relation between hemorrhage and coagulation competence is demonstrated. Significant bleeding develops based on an about 25 % reduction in thrombelastography determined maximal amplitude. A multivariable model including maximal amplitude discriminates patients with severe perioperative bleeding during cystectomy.

TRIAL REGISTRATION

The study was accepted on January 7(th), 2013 at www.clinicaltrialsregister.eu EudraCT 2012-005040-20.

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.

Electronic supplementary material

The online version of this article (doi:10.1186/s12871-015-0145-2) contains supplementary material, which is available to authorized users.

The role of point-of-care platelet function testing in predicting postoperative bleeding following cardiac surgery: a systematic review and meta-analysis

This systematic review and meta-analysis appraises the utility of point-of-care platelet function tests for predicting blood loss and transfusion requirements in cardiac surgical patients, and analyses whether their use within a transfusion management algorithm is associated with improved patient outcomes. We included 30 observational studies incorporating 3044 patients in the qualitative assessment, and nine randomised controlled trials including 1057 patients in the meta-analysis. Platelet function tests demonstrated significant variability in their ability to predict blood loss and transfusion requirements. Their use within a blood transfusion algorithm demonstrated a reduction in blood loss at longest follow-up (mean difference -102.9 ml (95% CI -149.9 to -56.1 ml), p < 0.001), and transfusion of packed red cells (RR 0.86 (95% CI 0.78-0.94), p = 0.001) and fresh frozen plasma (RR 0.42 (95% CI 0.30-0.59), p < 0.001). Viscoelastic methods used in combination with other platelet function tests achieved greater reduction in blood loss (mean difference -111.8 ml (95% CI -174.9 to -49.1 ml), p = 0.0005) compared with their use alone (mean difference -90.6 ml (95% CI 166.1-15.0 ml), p = 0.02). We conclude that incorporation of point-of-care platelet function tests into transfusion management algorithms is associated with a reduction in blood loss and transfusion requirements in cardiac surgery patients.

Predictive factors for bleeding-related re-exploration after cardiac surgery: A prospective cohort study

BACKGROUND

Bleeding-related re-exploration is a life-threatening complication after cardiac surgery. Nurses must be aware of important risk factors for this complication so that their assessment, monitoring and evaluation activities can be prioritized, focused and anticipated.

AIMS

To identify the predictive factors for bleeding-related re-exploration after cardiac surgery and to describe the sources of postoperative bleeding.

METHODS

This is a prospective cohort study at a tertiary cardiac school-hospital in São Paulo/SP, Brazil. Adult patients (n=323) submitted to surgical correction of acquired cardiac diseases were included. Potential risk factors for bleeding-related re-exploration within the 24 hours following admission to the intensive care unit were investigated in the patients' charts. A univariate analysis and a multiple analysis through logistic regression were conducted to identify the outcome predictors. The area under the receiver-operating characteristic curve was calculated as a measure of accuracy considering the cut-off points with the highest sensitivity and specificity.

RESULTS

The univariate factors significantly associated with bleeding-related re-exploration were a lower preoperative platelet count, a lower number of bypasses in coronary artery bypass surgery and postoperatively, a lower body temperature, infusion of lower intravenous volume, a higher positive end-expiratory pressure during mechanical ventilation and transfusion of blood products. The independent predictors of bleeding-related re-exploration included postoperative red blood cell transfusion, and transfusion of fresh frozen plasma, platelet or cryoprecipitate units. These predictors had a sensitivity of 87.5%, a specificity of 99.28% and an accuracy of 97.93%.

CONCLUSIONS

Blood product transfusion postoperatively is an independent predictor of bleeding-related re-exploration. Surgical errors prevailed as sources of bleeding.

Alterations in hemostasis during cytoreductive surgery and hyperthermic intraperitoneal chemotherapy in patients with peritoneal carcinomatosis

BACKGROUND

Cytoreductive surgery and hyperthermic intraperitoneal chemotherapy (HIPEC) is frequently associated with coagulation impairment and perioperative blood transfusion. Our aim was to investigate the impact of each procedure step on hemostasis, as measured by rotational thromboelastometry™ (ROTEM), fibrinogen level and platelet count as a primary outcome, along with its relationship with transfusion needs.

METHODS

A prospective longitudinal study was performed. Hemoglobin level, fibrinogen level, platelet count and ROTEM parameters: clotting time (CT), clot formation time (CFT), maximum clot firmness (MCF), α-angle (EXTEM, INTEM, FIBTEM) were measured before the procedure, at the end of cytoreductive surgery and after HIPEC. Appropriate statistical tests were used for comparison. A P<.05 was considered as significant.

RESULTS

Forty-one women, with median age 54 (range 34-76) were recruited. Cytoreductive surgery was followed by a reduction of hemoglobin level from 11,4±1,5g/dl to 10,6±1,6g/dl, a reduction of serum fibrinogen level from 269±69mg/dl to 230±48mg/dl (P<.01) and MCF decline from 20±10 to 16±8mm (P<.01), in the FIBTEM test. HIPEC was followed by no hemostatic impairment. The number of packed red blood cells administered during patients stay kept a mild significant relationship with both fibrinogen level (ρ = -0.5, P=.002), and MCF EXTEM values (ρ= -0.43, P=0.006), recorded after HIPEC.

CONCLUSIONS

The mild observed hemostatic impairment appeared after cytoreductive surgery instead of HIPEC, involving surgical hemorrhage as the most likely responsible factor. Further studies are required to confirm a correlation between transfusion needs and postoperative hemostatic tests.

Omitting pre-operative coagulation screening tests in hip fracture patients: stopping the financial cascade?

BACKGROUND

Coagulation screening continues as a standard of care in many hip fracture pathways despite the 2011 guidelines from the Association of Anaesthetists of Great Britain and Ireland (AAGBI) which recommend that such screening be performed only if clinically indicated. This study aims to evaluate the use of pre-operative coagulation screening and explore its financial impact.

METHODS

Prospective data was collected in accordance with the "Standardised Audit of Hip Fractures in Europe" (SAHFE) protocol. All patients admitted to our hospital with hip fractures during a 12-month period from November 2011 to November 2012 were analysed. Data including coagulation results and the use of vitamin K or blood products were collected retrospectively from the hospital computer system. Patient subgroup analysis was performed for intraoperative blood loss, post-operative blood units transfused, haematoma formation and gastrointestinal haemorrhage.

RESULTS

814 hip fractures were analysed. 91.4% (n=744) had coagulation tests performed and 22.0% (n=164) had an abnormal result. Of these, 55 patients were taking warfarin leaving 109 patients who had abnormal results and were not taking warfarin. When this group (n=109) was compared to those who had normal test results (n=580) and to all other patients (n=705) there was no difference in intraoperative blood loss (p=0.79, 0.78), postoperative transfusion (p=0.38, 0.30), postoperative haematoma formation (p=0.79, 1.00), or gastrointestinal haemorrhage (p=0.45, 1.00), respectively. In those who were not taking warfarin, but had abnormal results, none had treatment to reverse their coagulopathy with either vitamin K or blood products. By omitting pre-operative coagulation tests in patients who are not taking warfarin, we estimate a financial saving of between £66,500 and £432,250 per annum.

CONCLUSIONS

This study supports the hypothesis that routine pre-operative coagulation screening is unnecessary in hip fracture patients unless they take warfarin or have a known coagulopathy. Moreover, its omission represents significant cost-saving potential.

Comparison of three point-of-care testing devices to detect hemostatic changes in adult elective cardiac surgery: a prospective observational study

Background

Bleeding complications in cardiac surgery may lead to increased morbidity and mortality. Traditional blood coagulation tests are not always suitable to detect rapid changes in the patient's coagulation status. Point-of-care instruments such as the TEG (thromboelastograph) and RoTEM (thromboelastometer) have been shown to be useful as a guide for the clinician in the choice of blood products and they may lead to a reduction in the need for blood transfusion, contributing to better patient blood management.

Methods

The purpose of this study was to evaluate the ability of the TEG, RoTEM and Sonoclot instruments to detect changes in hemostasis in elective cardiac surgery with cardiopulmonary bypass and to investigate possible correlations between variables from these three instruments and routine hematological coagulation tests. Blood samples from thirty-five adult patients were drawn before and after surgery and analyzed in TEG, RoTEM, Sonoclot and routine coagulation tests. Data were compared using repeated measures analysis of variance and Pearson's test for linear correlation.

Results

We found significant changes for all TEG variables after surgery, for three of the RoTEM variables, and for one variable from the Sonoclot. There were significant correlations postoperatively between plasma fibrinogen levels and variables from the three instruments.

Conclusions

TEG and RoTEM may be used to detect changes in hemostasis following cardiac surgery with CPB. Sonoclot seems to be less suitable to detect such changes. Variables from the three instruments correlated with plasma fibrinogen and could be used to monitor treatment with fibrinogen concentrate.

Assessment of platelet function: Laboratory and point-of-care methods

In the event of blood vessel damage, human platelets are promptly recruited on the site of injury and, after their adhesion, activation and aggregation, prevent blood loss with the formation of a clot. The consequence of abnormal regulation can be either hemorrhage or the development of thrombosis. Qualitative and/or quantitative defects in platelets promote bleeding, whereas the residual reactivity of platelets, despite antiplatelet therapies, play an important role in promoting arterial thrombotic complications. Platelet function is traditionally assessed to investigate the origin of a bleeding syndrome, to predict the risk of bleeding prior surgery or during pregnancy or to monitor the efficacy of antiplatelet therapy in thrombotic syndromes that, now, can be considered a new discipline. “Old” platelet function laboratory tests such as the evaluation of bleeding time and the platelet aggregation analysis in platelet-rich plasma are traditionally utilized to aid in the diagnosis and management of patients with platelet and hemostatic disorders and used as diagnostic tools both in bleeding and thrombotic diathesis in specialized laboratories. Now, new and renewed automated systems have been introduced to provide a simple, rapid assessment of platelet function including point of care methods. These new methodologies are also suitable for being used in non-specialized laboratories and in critical area for assessing platelet function in whole blood without the requirement of sample processing. Some of these methods are also beginning to be incorporated into routine clinical use and can be utilized as not only as first panel for the diagnosis of platelet dysfunction, but also for monitoring anti-platelet therapy and to potentially assess risk of both bleeding and/or thrombosis.

Low dose of hydroxyethyl starch impairs clot formation as assessed by viscoelastic devices

OBJECTIVE

High doses of the synthetic colloid hydroxyethyl starch (HES) used for plasma expansion have been associated with impaired haemostasis and hypocoagulation. Less is known about effects on clot formation in the low haemodilutional range (< 40%). This study evaluated the effects of low haemodilution with HES and albumin on coagulation using two different viscoelastic methods.

METHODS

Clot formation was studied in vitro in healthy donor blood after 10% and 30% haemodilution with 60 g/L HES 130/0.4 or 50 g/L albumin with free oscillation rheometry (FOR) and rotational thromboelastography.

RESULTS

Clotting time was not significantly affected at 10% haemodilution but was prolonged with both substances at 30% dilution (p < 0.01-0.001). The effect was significantly more pronounced with HES than with albumin. The elasticity of the clot was slightly reduced at 10% dilution with albumin, more pronounced at 10% dilution with HES (p < 0.05), further reduced at 30% dilution with albumin and to a still greater extent at 30% dilution with HES (p < 0.05). With albumin the functional activity of fibrinogen was not reduced in excess of the dilutional effect. HES in contrast produced a further reduction in clot elasticity than caused by mere dilution at both 10% and 30% dilutions (p < 0.001).

CONCLUSIONS

There is an adverse effect on clot formation even at low grade haemodilution with both albumin and HES. The effect on coagulation is significantly more pronounced with HES than with albumin.

Abnormal whole blood thrombi in humans with inherited platelet receptor defects

To delineate the critical features of platelets required for formation and stability of thrombi, thromboelastography and platelet aggregation measurements were employed on whole blood of normal patients and of those with Bernard-Soulier Syndrome (BSS) and Glanzmann's Thrombasthenia (GT). We found that separation of platelet activation, as assessed by platelet aggregation, from that needed to form viscoelastic stable whole blood thrombi, occurred. In normal human blood, ristocetin and collagen aggregated platelets, but did not induce strong viscoelastic thrombi. However, ADP, arachidonic acid, thrombin, and protease-activated-receptor-1 and -4 agonists, stimulated both processes. During this study, we identified the genetic basis of a very rare double heterozygous GP1b deficiency in a BSS patient, along with a new homozygous GP1b inactivating mutation in another BSS patient. In BSS whole blood, ADP responsiveness, as measured by thrombus strength, was diminished, while ADP-induced platelet aggregation was normal. Further, the platelets of 3 additional GT patients showed very weak whole blood platelet aggregation toward the above agonists and provided whole blood thrombi of very low viscoelastic strength. These results indicate that measurements of platelet counts and platelet aggregability do not necessarily correlate with generation of stable thrombi, a potentially significant feature in patient clinical outcomes.

Intraoperative blood loss during orthognathic surgery is predicted by thromboelastography

PURPOSE

The aim of this prospective study was to evaluate the predictive value of the viscoelastic properties of whole blood samples collected preoperatively in relation to intraoperative blood loss in patients subjected to orthognathic surgery.

MATERIALS AND METHODS

Forty-one consecutive patients underwent simultaneous mandibular and maxillary osteotomy. Whole blood samples were collected preoperatively. The intraoperative blood loss volume was precisely estimated. The viscoelastic properties of whole blood samples were evaluated by thromboelastography (TEG), a global method that addresses the complex interplay among coagulation factors, blood platelets, and components of the fibrinolytic system. Blood platelet count, activated partial thromboplastin time, prothrombin time, plasma fibrinogen concentration, and D-dimer concentration were determined by routine methods.

RESULTS

Patients were separated into 2 groups according to their intraoperative bleeding volume (≤ 400 mL and >400 mL). No significant associations were observed between routine coagulation tests and intraoperative bleeding volume. The TEG results for the groups were compared. Significant associations were observed between intraoperative blood loss and the clot formation time, maximum clot firmness, and α angle, whereas bleeding volume was not related to the fibrinolytic resistance of the blood clot. An α angle exceeding 67° predicted with 95% certainty a blood loss of 400 mL or less.

CONCLUSIONS

We conclude that intraoperative bleeding volume in patients subjected to orthognathic surgery can be predicted by means of preoperative TEG analysis. TEG results provide optimization of patient safety and can be used for the evaluation of bleeding risk.

An assessment of thromboelastometry to monitor blood coagulation and guide transfusion support in liver transplantation

BACKGROUND

Rotation thromboelastometry (TEM) has been proposed as a convenient alternative to standard coagulation tests in guiding the treatment of coagulopathy during orthotopic liver transplantation (OLT). This study was aimed at assessing the value of TEM in monitoring blood coagulation and guide transfusion support in OLT.

STUDY DESIGN AND METHODS

Standard coagulation and TEM (EXTEM and FIBTEM) tests were performed at four preestablished intraoperative time points in 236 OLTs and prospectively recorded in a dedicated database together with the main operative and transfusion data. Transfusion thresholds were based on standard coagulation tests. Spearman's rank correlation (ρ), linear regression, and receiver operating characteristic curves were used when appropriate.

RESULTS

EXTEM maximum clot firmness (MCF(EXTEM)) was the TEM variable that best correlated with the platelet (PLT) and fibrinogen levels (ρ = 0.62 and ρ = 0.69, respectively). MCF(FIBTEM) correlated with fibrinogen level (ρ = 0.70). EXTEM clot amplitude at 10 minutes (A10(EXTEM)) was a good linear predictor of MCF(EXTEM) (R(2) =0.93). The cutoff values that best predicted the transfusion threshold for PLTs and fibrinogen were A10(EXTEM) = 35 mm and A10(FIBTEM) = 8 mm. At these values, the negative and positive predictive accuracies of TEM to predict the transfusion thresholds were 95 and 27%, respectively.

CONCLUSION

A10(EXTEM) is an adequate TEM variable to guide therapeutic decisions during OLT. Patients with A10(EXTEM) of greater than 35 mm are unlikely to bleed because of coagulation deficiencies, but using A10(EXTEM) of not more than 35 mm as the sole transfusion criterion can lead to unnecessary utilization of PLTs and fibrinogen-rich products.

Impact of cell salvage during cardiac surgery on the thrombelastomeric coagulation profile: a pilot study

Intraoperative cell salvage of the cardiopulmonary bypass residual volume can dilute platelets and coagulation factors. This is a report of a randomised control trial of 20 patients undergoing coronary bypass surgery. Residual cardiopulmonary bypass volume was processed and transfused after surgery in the cell salvage group and the residual volume was transfused unprocessed in the control group. The coagulation profile was measured using the Rotem(®) thrombelastometry system. Mean (SD) maximum clot firmness after surgery was 52.8 (5.4) mm in the cell salvage group compared to 57.2 (5.0) mm in the control group (p=0.04). Clot formation time was prolonged after surgery by 39 (27) s in the cell saver group compared to 19 (17) s in the control group (p=0.045). Platelet count was reduced after surgery by 96 (32) x 10(9).L(-1) in the cell saver group and 70 (19) x 10(9).L(-1) in the control group (p=0.03). Blood volume in the chest drains 4 hours after surgery was similar in both groups. There was a strong association between clot formation time after surgery and blood loss (R = 0.68, p=0.001). The increase in blood loss was 4.1 ml for every one-second increase in clot formation time (95% CI 1.9 - 6.4, p=0.001). Cell salvage of the residual cardiopulmonary bypass volume reduced platelet numbers and prolonged clot formation time and maximum clot firmness was less in this group.

Can RoTEM® analysis be applied for haemostatic monitoring in paediatric congenital heart surgery?

BACKGROUND

Successful management of bleeding disorders after congenital heart surgery requires detection of specific coagulation disturbances. Whole-blood rotation thromboelastometry (RoTEM®) provides continuous qualitative haemostatic profiles, and the technique has shown promising results in adult cardiac surgery.

SETTING

To compare the performance of RoTEM® with that of conventional coagulation tests in children, we conducted a descriptive study in children undergoing congenital cardiac surgery. For that purpose, 60 children were enrolled and had blood samples taken before, immediately after, and 1 day after surgery. Conventional coagulation tests included: activated partial thromboplastin time, prothrombin time, fibrinogen, fibrin D-dimer, thrombin clotting time, factor XIII, and platelet count.

RESULTS

Post-surgical haemostatic impairment was present to some degree in all children, as seen by pronounced changes in activated partial thromboplastin time, prothrombin time, thrombin clotting time, and platelet count, as well as RoTEM® analysis. RoTEM® showed marked changes in clotting time - prolonged by 7-18% - clot formation time - prolonged by 46-71% - maximum clot firmness - reduced by 10-19%, and maximum velocity - reduced by 29-39%. Comparison of the two techniques showed that conventional coagulation tests and RoTEM® performed equally well with regard to negative predictive values for excessive post-operative drain production - more than 20 millilitres per kilogram per 24 hours after surgery - with an area under the curve of approximately 0.65.

CONCLUSION

RoTEM® can detect haemostatic impairments in children undergoing cardiac surgery and the method should be considered as a supplement in the perioperative care of the children where targeted transfusion therapy is necessary to avoid volume overload.

Comparison of thromboelastometry (ROTEM®) with standard plasmatic coagulation testing in paediatric surgery

BACKGROUND

Thromboelastometry (ROTEM(®)) might be useful to detect intraoperative coagulation disorders early in major paediatric surgery. This observational trial compares this technique to standard coagulation tests.

METHODS

Intraoperative blood sampling was obtained in children undergoing elective major surgery. At each time point, standard coagulation tests [activated partial thromboplastin time (aPTT), prothrombin time (PT), and fibrinogen level] and ROTEM(®) analyses (InTEM, ExTEM, and FibTEM) were performed simultaneously by trained hospital laboratory staff.

RESULTS

A total of 288 blood samples from 50 subjects were analysed. While there was a poor correlation between PT and aPTT to ExTEM clotting time (CT) and InTEM CT, respectively, a good correlation was detected between PT and aPTT to clot formation time, and a very good correlation between fibrinogen level and FibTEM assay (r=0.882, P<0.001). Notably, 64% of PT and 94% of aPTT measurements were outside the reference range, while impaired CT was observed in 13% and 6.3%, respectively. Standard coagulation test results were available after a median of 53 min [inter-quartile range (IQR): 45-63 min], whereas 10 min values of ROTEM(®) results were available online after 23 min (IQR: 21-24 min).

CONCLUSIONS

PT and aPTT cannot be interchangeably used with ROTEM(®) CT. Based on the results of ROTEM(®), recommended thresholds for PT and aPTT might overestimate the need for coagulation therapy. A good correlation was found between the fibrinogen level and the FibTEM assay. In addition, ROTEM(®) offered faster turnaround times.

Monitoring patients at risk of massive transfusion with Thrombelastography or Thromboelastometry: a systematic review

BACKGROUND

Thrombelastography (TEG) and Thrombelastometry (ROTEM) are viscoelastic whole-blood assays evaluating the haemostatic capacity of blood. These devices are used in algorithms to guide transfusion of haemostatic blood components.

METHODS

The methods used for this study were systematic reviews with meta-analyses and trial sequential analyses of randomised clinical trials (RCTs) of TEG/ROTEM-based algorithm compared with standard treatment in patients with bleeding. Primary outcome was all-cause mortality. We searched the literature in seven databases (up to 31 October 2010), reference lists, registers of ongoing trials, and contacted authors and experts. We extracted data from included studies related to study methods, interventions, outcomes, bias risk and adverse events using Cochrane methodology. All trials irrespective of blinding or language status were included.

RESULTS

Nine trials involving 776 participants were included. Eight trials involved cardiac surgery with an average blood loss of 390-960  ml, and one trial investigated liver transplantations. One trial was classified as low-risk-of-bias trial. We found two ongoing trials. No impact was identified on mortality, amount of blood transfused, incidence of surgical reinterventions, time to extubation, or length of stay in hospital and intensive care unit. We identified a significant reduction in blood loss favouring the use of TEG/ROTEM {85  ml [95% confidence interval (CI) 29.4-140.7]} and in the proportion of patients receiving freshly frozen plasma and platelets [relative risk 0.39 (95%CI 0.27-0.57)].

CONCLUSION

There is currently weak evidence to support the use of TEG/ROTEM as a tool to guide transfusion in patients with severe bleeding. Further studies need to address other clinical settings and with larger blood losses.

Change in hemostatic intervention after implementation of thromboelastometry

OBJECTIVE

To monitor the use of blood products and hemostatic intervention after implementation of thromboelastometry.

DESIGN

Observational prospective study using a historic control.

SETTING

Single-center university hospital.

PARTICIPANTS

Patients undergoing cardiac surgery during 2008 (n = 811) were compared with similar patients in 2009 (n = 865).

INTERVENTIONS

Thromboelastometry was implemented in December 2008. Changes in transfusion of blood products and changes in use of recombinant factor VIIa and fibrinogen were studied.

MEASUREMENTS AND MAIN RESULTS

Use of blood products was not decreased significantly after implementation of thromboelastometry. However, in patients receiving blood products, the units of red blood cells were decreased significantly (p = 0.04). Regarding hemostatic reagents, the use of recombinant factor VIIa was decreased significantly (p = 0.04), and the use of fibrinogen increased significantly (p < 0.001). Most blood products (>70%) were given to a minority of patients (∼10%) in 2008 and 2009. In 2009, thromboelastometry was performed in 146 patients (17%), and the use of blood products (p < 0.0001), recombinant factor VIIa (p < 0.001), and fibrinogen (p < 0.001) was significantly higher compared with patients in whom thromboelastometry was not performed.

CONCLUSIONS

After implementation of thromboelastometry, the use of recombinant factor VIIa was decreased significantly, whereas the use of blood products was not decreased significantly in patients undergoing cardiac surgery.