The Incremental Value of Thrombelastography for Prediction of Excessive Blood Loss After Cardiac Surgery

Risk factor prediction of severe postoperative acute kidney injury at stage 3 in patients with acute type A aortic dissection using thromboelastography

Objective

Perioperative blood transfusions and postoperative drainage volume not only are the commonly recognized risk factors for acute kidney injury (AKI) but also are indirect indicators of coagulopathy in patients with acute type A aortic dissection (ATAAD). However, standard laboratory tests fail to accurately reflect and assess the overall coagulopathy profile in patients with ATAAD. Thus, this study aimed to explore the association between the hemostatic system and severe postoperative AKI (stage 3) in patients with ATAAD using thromboelastography (TEG).

Methods

We selected 106 consecutive patients with ATAAD who underwent emergency aortic surgery at Beijing Anzhen Hospital. All participants were categorized into the stage 3 and non-stage 3 groups. The hemostatic system was evaluated using routine laboratory tests and TEG preoperatively. We undertook univariate and multivariate stepwise logistic regression analyses to determine the potential risk factors for severe postoperative AKI (stage 3), with a special investigation on the association between hemostatic system biomarkers and severe postoperative AKI (stage 3). The receiver operating characteristic (ROC) curves were generated to assess the predictive ability of hemostatic system biomarkers for severe postoperative AKI (stage 3).

Results

A total of 25 (23.6%) patients developed severe postoperative AKI (stage 3), including 21 patients (19.8%) who required continuous renal replacement therapy (RRT). Multivariate logistic regression analysis demonstrated that the preoperative fibrinogen level (OR, 2.02; 95% CI, 1.03 to 3.00; p = 0.04), platelet function (MA level) (OR, 1.23; 95% CI, 1.09 to 1.39; p = 0.001), and cardiopulmonary bypass (CPB) time (OR, 1.01; 95% CI, 1.00 to 1.02; p = 0.02) were independently associated with severe postoperative AKI (stage 3). The cutoff values of preoperative fibrinogen and platelet function (MA level) for predicting severe postoperative AKI (stage 3) were determined to be 2.56 g/L and 60.7 mm in the ROC curve [area under the curve (AUC): 0.824 and 0.829; p < 0.001].

Conclusions

The preoperative fibrinogen level and platelet function (measured by the MA level) were identified as potential predictive factors for developing severe postoperative AKI (stage 3) in patients with ATAAD. Thromboelastography could be considered a potentially valuable tool for real-time monitoring and rapid assessment of the hemostatic system to improve postoperative outcomes in patients.

A prospective, controlled study on the utility of rotational thromboelastometry in surgery for acute type A aortic dissection

To evaluate the hemostatic system with ROTEM in patients undergoing surgery for acute type aortic dissection (ATAAD) using elective aortic procedures as controls. This was a prospective, controlled, observational study. The study was performed at a tertiary referral center and university hospital. Twenty-three patients with ATAAD were compared to 20 control patients undergoing elective surgery of the ascending aorta or the aortic root. ROTEM (INTEM, EXTEM, HEPTEM and FIBTEM) was tested at 6 points in time before, during and after surgery for ATAAD or elective aortic surgery. The ATAAD group had an activated coagulation coming into the surgical theatre. The two groups showed activation of both major coagulation pathways during surgery, but the ATAAD group consistently had larger deficiencies. Reversal of the coagulopathy was successful, although none of the groups reached elective baseline until postoperative day 1. ROTEM did not detect low levels of clotting factors at heparin reversal nor low levels of platelets. This study demonstrated that ATAAD is associated with a coagulopathic state. Surgery causes additional damage to the hemostatic system in ATAAD patients as well as in patients undergoing elective surgery of the ascending aorta or the aortic root. ROTEM does not adequately catch the full coagulopathy in ATAAD. A transfusion protocol in ATAAD should be specifically created to target this complex coagulopathic state and ROTEM does not negate the need for routine laboratory tests.

Systematic Review and Meta-Analysis of Diagnostic Test Accuracy Studies Evaluating Point-of-Care Tests of Coagulopathy in Cardiac Surgery

Treatment guidelines recommend the routine use of point-of-care diagnostic tests for coagulopathy in the management of cardiac surgery patients at risk of severe bleeding despite uncertainty as to their diagnostic accuracy. We performed a systematic review and meta-analysis of studies that evaluated the diagnostic accuracy of viscoelastometry, platelet function tests, and modified thromboelastography (TEG) tests, for coagulopathy in cardiac surgery patients. The reference standard included resternotomy for bleeding, transfusion of non-red cell components, or massive transfusion. We searched MEDLINE, EMBASE, CINAHL, and Clinical Trials.gov, from inception to June 2019. Study quality was assessed using QUADAS-2. Bivariate models were used to estimate summary sensitivity and specificity with (95% confidence intervals). All 29 studies (7440 participants) included in the data synthesis evaluated the tests as predictors of bleeding. No study evaluated their role in the management of bleeding. None was at low risk of bias. Four were judged as low concern regarding applicability. Pooled estimates of diagnostic accuracy were; Viscoelastic tests, 12 studies, sensitivity 0.61 (0.44, 0.76), specificity 0.83 (0.70, 0.91) with significant heterogeneity. Platelet function tests, 12 studies, sensitivity 0.63 (0.53, 0.72), specificity 0.75 (0.64, 0.84) with significant heterogeneity. TEG modification tests, 3 studies, sensitivity 0.80 (0.67, 0.89), specificity 0.76 (0.69, 0.82) with no evidence of heterogeneity. Studies reporting the highest values for sensitivity and specificity had important methodological limitations. In conclusion, we did not demonstrate predictive accuracy for commonly used point-of-care devices for coagulopathic bleeding in cardiac surgery. However, the certainty of the evidence was low.

Viscoelastic testing in cardiac surgery

Bleeding complications are common in cardiac surgery and lead to an increase in morbidity and mortality. This is multifactorial in aetiology including the effects of cardiopulmonary bypass, the drugs given to manipulate the coagulation system and the vascular nature of the surgery itself. Viscoelastic tests provide a point of care, rapid assessment of coagulation which offer the advantage of faster turnaround times and a nuanced view of the elements of the coagulation system allowing targeted therapy to be delivered quickly. Both thomboelastography (TEG)and thromboelastometry (ROTEM) have been recommended for use in cardiac surgery, both have shown a reduction in transfusion and bleeding when used as part of a testing algorithm. They are particularly useful in assessing residual heparinisation and fibrinogen levels. Additionally, TEG allows the evaluation of the effects of anti-platelet agents on platelet function. This review discusses the mechanisms by which bleeding occurs in cardiac surgery and explores three uses of viscoelastic testing in cardiac surgery: to predict bleeding, to assess platelet function and peri-operative testing to reduce transfusion.

Thromboelastography and rotational thromboelastometry for the surgical intensivist: A narrative review

BACKGROUND

Viscoelastic tests (VETs), specifically thromboelastography (TEG) and rotational thromboelastometry (ROTEM), are gaining popularity in the management of critically ill surgical patients with hemorrhage or thrombosis due to their comprehensive characterization of the coagulation process and point-of-care availability in comparison to conventional coagulation tests (CCTs). We review current evidence for VET use in patients in the surgical intensive care unit (SICU).

METHODS

We searched PUBMED, EMBASE and the Cochrane Library through May 30, 2018 for articles that evaluated the use of VETs in patient populations and clinical scenarios germane to the surgical intensivist. Individual articles were critically evaluated for relevance and appropriate methodology using a structured technique. Information on patient characteristics, timing and methods of CCTs/VETs, and outcomes was collected and summarized in narrative form.

RESULTS

Of 2,589 identified articles, 36 were included. Five (14%) were interventional studies and 31 (86%) were observational. Twenty-five (69%) evaluated TEG, 11 (31%) ROTEM and 18 (50%) CCTs. Investigated outcomes included quantitative blood loss (13 (36%)), blood product transfusion (9 (25%)), thromboembolic events (9 (25%)) and mortality (6 (17%)). We identified 12 clinical scenarios with sufficient available evidence, much of which was of limited quantity and poor methodological quality. Nonetheless, research supports the use of VETs for guiding early blood product administration in severe traumatic hemorrhage and for the prediction of abstract excess bleeding following routine cardiac surgery. In contrast, evidence suggests VET-based heparin dosing strategies for venous thromboembolism prophylaxis are not superior to standard dosing in SICU patients.

CONCLUSION

While VETs have the potential to impact the care of critically ill surgical patients in many ways, current evidence for their use is limited, mainly because of poor methodological quality of most available studies. Further high-quality research, including several ongoing randomized controlled trials, is needed to elucidate the role of TEG/ROTEM in the SICU population.

LEVEL OF EVIDENCE

Systematic review, level IV.

Preventing and managing catastrophic bleeding during extracorporeal circulation

The use of extracorporeal circulation for cardiac surgery and extracorporeal life support poses tremendous challenges to the hemostatic equilibrium given its diametric tendency to trigger hyper- and hypocoagulopathy. The necessity of anticoagulant therapy to counteract the hemostatic activation by the extracorporeal circuitry compounded by unfavorable patient and surgical factors significantly increase the risk of catastrophic bleeding in patients who require extracorporeal circulation. Preoperative measures, such as stratification of high-risk bleeding patients, and optimization of the modifiable variables, including anemia and thrombocytopenia, provide a crude estimation of the likelihood and may modify the risk of catastrophic bleeding. The anticipation for catastrophic bleeding subsequently prompts the appropriate preparation for potential resuscitation and massive transfusion. Equally important is intraoperative prevention with the prophylactic application of tranexamic acid, an antifibrinolytic agent that has promising benefits in reduction of blood loss and transfusion. In the event of uncontrolled catastrophic bleeding despite preemptive strategies, all effort must be centered on regaining hemostasis through surgical control and damage control resuscitation to protect against worsening coagulopathy and end organ failure. When control of bleeding is reinstated, management should shift focus from systemic therapy to targeted hemostatic therapy aimed at the potential culprits of coagulopathy as identified by point of care hemostatic testing. This review article outlines the strategies to appropriately intervene using prediction, prevention, preparation, protection, and promotion of hemostasis in managing catastrophic bleeding in extracorporeal circulation.

Relationship between maximum clot firmness in ROTEM® and postoperative bleeding after coronary artery bypass graft surgery in patients using clopidogrel

Background:

The aim of the present study was to investigate the relationship between maximum clot firmness (MCF) in rotational thromboelastometry (ROTEM^®) and postoperative bleeding in patients on clopidogrel after emergency coronary artery bypass graft surgery (CABG).

Methods:

This observational study recruited 60 patients posted for emergency CABG following unsuccessful primary percutaneous coronary intervention (PCI) while on 600 mg of clopidogrel. The study population was divided into 2 groups on the basis of their MCF in the extrinsically activated thromboelastometric (EXTEM) component of the (preoperative) ROTEM^® test: patients with MCF <50 mm (n = 16) and those with MCF ≥50 mm (n = 44). Postoperative chest tube drainage amount, need for blood product transfusion, postoperative complications, and duration of mechanical ventilation after CABG were recorded.

Results:

No significant differences were observed between the two groups regarding duration of surgery, cardiopulmonary bypass, and aortic cross-clamp time. Chest tube drainage at 6, 12, and 24 h after Intensive Care Unit admission were significantly higher in the patients with MCF below 50 mm. The need for blood product transfusion was higher in the group with MCF <50 mm. In patients who experienced postoperative bleeding of 1000 mL or more, the ROTEM^® parameters of INTEM (Intrinsically activated thromboelastomery) α and MCF, EXTEM α and MCF, and HEPTEM (INTEM assay performed in the presence of heparinase) MCF (but not FIBTEM (Thromboelastometric assay for the fibrin part of the clot) values) were significantly lower than those with postoperative bleeding <1000 mL (P ≤ 0.05).

Conclusions:

When platelet aggregometry is not available, the ROTEM^® test could be useful for the prediction of increased risk bleeding after emergency CABG in patients who have received a loading dose of clopidogrel.

Thromboelastograph with Platelet Mapping(TM) predicts postoperative chest tube drainage in patients undergoing coronary artery bypass grafting

OBJECTIVE

The goal of this study was to evaluate the ability of Thromboelastograph with Platelet Mapping (TEG-PM(TM)) to predict postoperative bleeding tendency in patients with a history of recent anti-platelet therapy undergoing coronary artery bypass grafting (CABG).

DESIGN

A retrospective analysis. Association between predictor variables (MAADP [maximum amplitude produced by adenosine diphosphate], MAAA [maximum amplitude produced by arachidonic acid], percent of platelets inhibited by clopidogrel, percent of platelets inhibited by aspirin) and the outcomes as elevated chest tube drainage (CTD) and blood transfusion were investigated by logistic regression model. CTD was considered elevated if it was ≥ 600 mL within 12 hours after surgery.

SETTING

A university hospital.

PARTICIPANTS

Patients on antiplatelet therapy scheduled to undergo CABG that had TEG-PM(TM) done as a point-of-care test.

INTERVENTIONS

None.

RESULTS

A total of 78 patients had preoperative TEG-PM(TM) test and on-pump CABG surgeries performed on the same day. Among them, 20 patients (25.6%) had elevated CTD. Decreased MAADP (odds ratio [OR] 0.94), increased percent inhibition of platelets by clopidogrel (OR 1.03), and lower body mass index (BMI) (OR 0.78) were significantly associated with elevated CTD. The same parameters were also associated with platelets transfusion: MAADP (OR 0.94), percent of inhibition of platelets by clopidogrel (OR 1.03) and BMI (OR 0.77).

CONCLUSIONS

TEG-PM(TM) parameters and BMI are predictive of elevated CTD and platelets transfusion. A 1 mm decrease in MAADP increases the likelihood of elevated CTD and the likelihood of platelets transfusion by 6% whereas 1 unit decrease in BMI is associated with an increased likelihood of elevated CTD and platelets transfusion by 22% and 23% respectively.

BMI Is an Independent Preoperative Predictor of Intraoperative Transfusion and Postoperative Chest-Tube Output

Background An increasing obese population in the United States focuses attention on perioperative management of obese and overweight patients. Objective We sought to determine if obesity, determined by body mass index (BMI), was a preoperative indicator of bleeding in coronary artery bypass graft (CABG) surgery as measured by intraoperative packed red blood cell transfusion frequency and 24-hour chest-tube output amount. Methods A retrospective chart review examined 290 consecutive patients undergoing single-surgeon off-pump or on-pump CABG surgery between November 2003 and April 2009. Preoperative variables of age, gender, hematocrit, platelet count, and BMI, chest tube output during the immediate 24-hour postoperative period, and the type of procedure (on-pump vs. off-pump) were analyzed. Logistic regression analysis was used to evaluate the likelihood of intraoperative transfusion. Linear regression analysis was used to evaluate 24-hour chest-tube output. Results Preoperative variables that significantly increased the likelihood of intraoperative transfusions were older age and low hematocrit; a significant decrease in likelihood was found with male gender, overweight BMI, and off-pump procedures. Preoperative variables that significantly increased 24-hour chest-tube output were low hematocrit, high hematocrit, and low platelets while a significant decrease in output was seen with overweight BMI and obese BMI. Conclusion Overweight and obese BMI are significant independent predictors of decreased intraoperative transfusion and decreased postoperative blood loss.

Impact of retransfusion of blood processed in cell-saver on coagulation versus cardiopulmonary bypass: a prospective observational study using thromboelastography

AIMS

To compare an impact of retransfusion of blood processed in cell-saver (CS) with that of cardiopulmonary bypass (CPB) on blood coagulation in patients undergoing cardiac surgery.

METHODS

Prospective observational study using thromboelastography (TEG).

RESULTS

TEG samples from 170 patients were analyzed. Cardiopulmonary bypass was used in 100 patients while 70 patients were operated off-pump. In 20 off-pump patients collected blood was processed by cell-saver and returned. In all patients clot formation after heparin neutralization by protamine was unimpaired. However, there was a significant increase in fibrinolysis defined by the TEG parameter Lysis time 30 min after the maximum amplitude of the clot was reached (Ly30) in groups with CPB or CS but this increase still did not exceed the threshold for clinical fibrinolysis (Ly30 > 7.5%). In the group without CPB there was no significant impact on coagulation.

CONCLUSION

Surgery that avoids CPB and/or CS is the gentlest method for inducing blood coagulation.

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.

Platelet function measurement-based strategy to reduce bleeding and waiting time in clopidogrel-treated patients undergoing coronary artery bypass graft surgery: the timing based on platelet function strategy to reduce clopidogrel-associated bleeding related to CABG (TARGET-CABG) study

BACKGROUND

Aspirin and clopidogrel therapy is associated with a variable bleeding risk in patients undergoing coronary artery bypass graft surgery (CABG). We evaluated the role of platelet function testing in clopidogrel-treated patients undergoing CABG.

METHODS AND RESULTS

One hundred eighty patients on background aspirin with/without clopidogrel therapy undergoing elective first time isolated on-pump CABG were enrolled in a prospective single-center, nonrandomized, unblinded investigation (Timing Based on Platelet Function Strategy to Reduce Clopidogrel-Associated Bleeding Related to CABG [TARGET-CABG] study) between September 2008 and January 2011. Clopidogrel responsiveness (ADP-induced platelet-fibrin clot strength [MA(ADP)]) was determined by thrombelastography; CABG was done within 1 day, 3-5 days, and >5 days in patients with an MA(ADP) >50 mm, 35-50 mm, and <35 mm, respectively. The primary end point was 24-hour chest tube drainage and key secondary end point was total number of transfused red blood cells. Equivalence was defined as ≤25% difference between groups. ANCOVA was used to adjust for confounders. Mean 24-hour chest tube drainage in clopidogrel-treated patients was 93% (95% confidence interval, 81-107%) of the amount observed in clopidogrel-naive patients, and the total amount of red blood cells transfused did not differ between groups (1.80 U versus 2.08 U, respectively, P=0.540). The total waiting period in clopidogrel-treated patients was 233 days (mean, 2.7 days per patient).

CONCLUSIONS

A strategy based on preoperative platelet function testing to determine the timing of CABG in clopidogrel-treated patients was associated with the same amount of bleeding observed in clopidogrel-naive patients and ≈50% shorter waiting time than recommended in the current guidelines.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT00857155.

Peri-operative platelet function testing: the potential for reducing ischaemic and bleeding risks

The pivotal role of platelet activation and reactivity during atherothrombotic event occurrence associated with acute coronary syndromes (ACS) or percutaneous coronary interventions (PCI) is well established. Numerous translational research studies have established a threshold level of platelet reactivity during dual antiplatelet therapy above which a higher risk for ischaemic event occurrence has been observed. The clinical validity of these threshold values in reducing ischemic event occurrence with modified P2Y12 receptor therapy is currently under investigation in large-scale clinical trials. The association between on-treatment platelet reactivity measured by an ex vivo assay and the occurrence of bleeding events is less established. Currently, there is limited evidence of an association between platelet inhibition and coronary artery bypass grafting (CABG)- related bleeding in patients on clopidogrel therapy indicating that preoperative platelet function monitoring may guide both the timing of elective CABG and the administration of blood products in patients needing surgery. However, in the absence of a large-scale prospective clinical trial, routine platelet function monitoring and modification of timing of surgery based on platelet function monitoring are currently not recommended.