Thromboelastography for the Orthopaedic Surgeon

Direct Oral Anticoagulants: How Do These Drugs Work, How to Monitor, and What Is Their Role in Orthopaedic Surgery

Postoperative venous thromboembolism is a major adverse event associated with orthopaedic surgery. With the addition of perioperative anticoagulation and antiplatelet therapy, the rates of symptomatic venous thromboembolism have dropped to 1% to 3%, and as such, practicing orthopaedic surgeons must be familiar with these medications, including aspirin, heparin, or warfarin, and the use of direct oral anticoagulants (DOACs). DOACs are increasingly being prescribed due to their predictable pharmacokinetics and increased convenience, as they do not require routine monitoring, and 1% to 2% of the general population is currently anticoagulated. Although the introduction of DOACs has yielded additional treatment options, this has also led to confusion and uncertainty regarding treatment, specialized testing, and when and what reversal agents are appropriate. This article provides a basic overview of DOAC medications, their suggested use in the perioperative setting, effects on laboratory testing, and consideration for when and how to use reversal agents in orthopaedic patients.

What Proportion of Patients With Musculoskeletal Tumors Demonstrate Thromboelastographic Markers of Hypercoagulability? A Pilot Study

BACKGROUND

Thromboelastography (TEG) is a point-of-care venipuncture test that measures the elasticity and strength of a clot formed from a patient's blood, providing a more comprehensive analysis of a patient's coagulation status than conventional measures of coagulation. TEG includes four primary markers: R-time, which measures the time to clot initiation and is a proxy for platelet function; K-value, which measures the time for said clot to reach an amplitude of 20 mm and is a proxy for fibrin cross-linking; maximum amplitude (MA), which measures the clot's maximum amplitude and is a proxy for platelet aggregation; and LY30, which measures the percentage of clot lysis 30 minutes after reaching the MA and is a proxy for fibrinolysis. Analysis of TEG-derived coagulation profiles may help surgeons identify patient-related and disease-related factors associated with hypercoagulability. TEG-derived coagulation profiles of patients with musculoskeletal oncology conditions have yet to be characterized.

QUESTIONS/PURPOSES

(1) What TEG coagulation profile markers are most frequently aberrant in patients with musculoskeletal oncology conditions presenting for surgery? (2) Among patients with musculoskeletal oncology conditions presenting for surgery, what factors are more common in those with TEG-defined hypercoagulability? (3) Do patients with musculoskeletal oncology conditions with preoperative TEG-defined hypercoagulability have a higher postoperative incidence of clinically symptomatic venous thromboembolism (VTE) than those with a normal TEG profile?

METHODS

In this retrospective, pilot study, we analyzed preoperatively drawn TEG assays on 52 patients with either primary bone sarcoma, soft tissue sarcoma, or metastatic disease to bone who were scheduled to undergo either tumor resection or nail stabilization. Between January 2020 and December 2021, our orthopaedic oncology service treated 410 patients in total. Of these, 13% (53 of 410 patients) had preoperatively drawn TEG assays. TEG assays were collected preincision as part of a division initiative to integrate the assay into a clinical care protocol for patients with primary bone or soft tissue sarcoma or metastatic disease to bone. Unfortunately, failures to adequately communicate this to our anesthesia colleagues on a consistent basis resulted in a low overall rate of assay draws from eligible patients. One patient on therapeutic anticoagulation preoperatively for the treatment of active VTE was excluded, leaving 52 patients eligible for analysis. We did not exclude patients taking prophylactic antiplatelet therapy preoperatively. All patients were followed for a minimum of 6 weeks postoperatively. We analyzed factors (age, sex, tumor location, presence of metastases, and soft tissue versus bony disease) in reference to hypercoagulability, defined as a TEG result indicating supranormal clot formation (for example, reduced R-time, reduced K-value, or increased MA). Patients with clinical concern for deep vein thrombosis (DVT) (typically painful swelling of the affected extremity) or pulmonary embolism (typically by dyspnea, tachycardia, and/or chest pain) underwent duplex ultrasonography or chest CT angiography, respectively, to confirm the diagnosis. Categorical variables were analyzed via a Pearson chi-square test and continuous variables were analyzed via t-test, with significance defined at α = 0.05.

RESULTS

Overall, 60% (31 of 52) of patients had an abnormal preoperative TEG result. All abnormal TEG assay results demonstrated markers of hypercoagulability. The most frequent aberration was a reduced K-value (40% [21 of 52] of patients), followed by reduced R-time (35% [18 of 52] of patients) and increased MA (17% [9 of 52] of patients). The mean ± SD TEG markers were R-time: 4.3 ± 1.0, K-value: 1.2 ± 0.4, MA: 66.9 ± 7.7, and LY30: 1.0 ± 1.2. There was no association between hypercoagulability and tumor location or metastatic stage. The mean age of patients with TEG-defined hypercoagulability was higher than those with a normal TEG profile (44 ± 23 years versus 59 ± 17 years, mean difference 15 [95% confidence interval (CI) 4 to 26]; p = 0.01). In addition, female patients were more likely than male patients to demonstrate TEG-defined hypercoagulability (75% [18 of 24] of female patients versus 46% [13 of 28] of male patients, OR 3.5 [95% CI 1 to 11]; p = 0.04) as were those with soft tissue disease (as opposed to bony) (77% [20 of 26] of patients with soft tissue versus 42% [11 of 26] of patients with bony disease, OR 4.6 [95% CI 1 to 15]; p = 0.01). Postoperatively, symptomatic DVT developed in 10% (5 of 52; four proximal DVTs, one distal DVT) of patients, and no patients developed symptomatic pulmonary embolism. Patients with preoperative TEG-defined hypercoagulability were more likely to be diagnosed with symptomatic postoperative DVT than patients with normal TEG profiles (16% [5 of 31] of patients with TEG-defined hypercoagulability versus 0% [0 of 21] of patients with normal TEG profiles; p = 0.05). No patients with normal preoperative TEG profiles had clinically symptomatic VTE.

CONCLUSION

Patients with musculoskeletal tumors are at high risk of hypercoagulability as determined by TEG. Patients who were older, female, and had soft tissue disease (as opposed to bony) were more likely to demonstrate TEG-defined hypercoagulability in our cohort. The postoperative VTE incidence was higher among patients with preoperative TEG-defined hypercoagulability. The findings in this pilot study warrant further investigation, perhaps through multicenter collaboration that can provide a sufficient cohort to power a robust, multivariable analysis, better characterizing patient and disease risk factors for hypercoagulability. Patients with TEG-defined hypercoagulability may warrant a higher index of suspicion for VTE and careful thought regarding their chemoprophylaxis regimen. Future work may also evaluate the effectiveness of TEG-guided chemoprophylaxis, as results of the assay may inform selection of antiplatelet versus anticoagulant agent.

LEVEL OF EVIDENCE

Level III, therapeutic study.

Blood Conservation Techniques and Strategies in Orthopedic Anesthesia Practice

Orthopedic surgery procedures involving joint arthroplasty, complex spine, long bone and pelvis procedure, and trauma and oncological cases can be associated with a high risk of bleeding and need for blood transfusion, making efforts to optimize patient care and reduce blood loss very important. Patient blood management programs incorporate efforts to optimize preoperative anemia, develop transfusion protocols and restrictive hemoglobin triggers, advance surgical and anesthesia practice, and use antifibrinolytic therapies. Perioperative management of anticoagulant therapies, a multidisciplinary decision-making task, weighs in risks and benefits of thromboembolic risk and surgical bleeding and is patient- and surgery-specific.

Viscoelastic Hemostatic Assays for Orthopedic Trauma and Elective Procedures

The application of viscoelastic hemostatic assays (VHAs) (e.g., thromboelastography (TEG) and rotational thromboelastometry (ROTEM)) in orthopedics is in its relative infancy when compared with other surgical fields. Fortunately, several recent studies describe the emerging use of VHAs to quickly and reliably analyze the real-time coagulation and fibrinolytic status in both orthopedic trauma and elective orthopedic surgery. Trauma-induced coagulopathy—a spectrum of abnormal coagulation phenotypes including clotting factor depletion, inadequate thrombin generation, platelet dysfunction, and dysregulated fibrinolysis—remains a potentially fatal complication in severely injured and/or hemorrhaging patients whose timely diagnosis and management are aided by the use of VHAs. Furthermore, VHAs are an invaluable compliment to common coagulation tests by facilitating the detection of hypercoagulable states commonly associated with orthopedic injury and postoperative status. The use of VHAs to identify hypercoagulability allows for an accurate venous thromboembolism (VTE) risk assessment and monitoring of VTE prophylaxis. Until now, the data have been insufficient to permit an individualized approach with regard to dosing and duration for VTE thromboprophylaxis. By incorporating VHAs into routine practice, orthopedic surgeons will be better equipped to diagnose and treat the complete spectrum of coagulation abnormalities faced by orthopedic patients. This work serves as an educational primer and up-to-date review of the current literature on the use of VHAs in orthopedic surgery.

Pelvic Ring Injury Mortality: Are We Getting Better?

OBJECTIVES

To determine if changes in pelvic trauma care and treatment protocols have affected overall mortality rates after pelvic ring injury.

DESIGN

Retrospective cohort study.

SETTING

Level I trauma center.

PATIENTS/PARTICIPANTS

A total of 3314 patients with pelvic ring injuries who presented to a single referral center from 1999 to 2018 were included in the study.

INTERVENTION

Pelvic ring management, years 1999-2006 versus years 2007-2018.

MAIN OUTCOME MEASUREMENTS

In hospital mortality. Other examined variables included change in patient demographics, fracture characteristics, date of injury, associated injuries, length of hospital stay, Abbreviated Injury Severity Score.

RESULTS

The composite mortality rate was 6.5% (214/3314). The earliest cohort presented a mortality rate of 9.1% [111/1224; 95% confidence interval (CI), 7.6%-10.8%] compared with the more recent cohort mortality rate of 4.9% (103/2090; 95% CI, 4.1%-5.9%). Overall mortality was significantly lower in the more recent period, a risk difference of 4.1% (95% CI, 2.3%-6.1%; P < 0.01). After adjusting for age and Abbreviated Injury Severity Score of the brain, chest, and abdomen, the mortality reduction was more pronounced with an adjusted risk difference of 6.4% (95% CI, 4.7%-8.1%; P < 0.01).

CONCLUSION

Significant improvement in the mortality rate of pelvic ring injuries has been demonstrated in recent years (4.9% vs. 9.1%) and the difference is even large when accounting for known confounders. Improvement appears to coincide chronologically with changes in trauma resuscitation and implementation of adjuvant treatments for managing patients with severe hemorrhagic shock. Although the exact benefit of each treatment awaits further research, these data might indicate improved care over time for these difficult patients.

LEVEL OF EVIDENCE

Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Thromboelastography is predictive of mortality, blood transfusions, and blood loss in patients with traumatic pelvic fractures: a retrospective cohort study

PURPOSE

In patients with traumatic pelvic fractures, thromboelastography (TEG) is a useful tool to rapidly evaluate and identify coagulation disturbances. The purpose of this study was to examine the coagulation kinetics of patients with traumatic pelvic fractures (pelvic ring and/or acetabulum) by analyzing the TEG results at initial presentation and its relationship with mortality and blood loss.

METHODS

A retrospective review at our Level-1 trauma center was conducted to identify Full Trauma Team activations (FTTa) with traumatic pelvic and/or acetabular fractures who were evaluated with a TEG on initial presentation between 2012 and 2016. In-hospital mortality, product transfusion, and hemoglobin changes were analyzed. Subgroup analysis was performed based on pelvic fracture type.

RESULTS

141 patients with a mean age of 49.0 ± 20.8 years and mean Injury Severity Score (ISS) of 25.18 ± 12.8 met inclusion criteria. PRBC transfusion occurred in 78.0% of patients; a total of 1486 blood products were transfused. A total of 65 patients (46.1%) underwent operative treatment for the pelvic injuries, and 18 patients (12.7%) required embolization. The overall in-hospital mortality rate was 14.9%. The degree of clot lysis at 30 min (LY30) was significantly associated with blood loss (p < 0.0001), units of packed red blood cells (PRBCs) transfused (p < 0.0001), and mortality rate (p = 0.0002).

CONCLUSION

Increased fibrinolysis evidenced by an elevated LY30 on initial TEG in patients with traumatic pelvic fractures is associated with increased blood loss, blood product transfusions, and mortality. Future studies should evaluate the clinical utility of reversing hyperfibrinolysis on initial TEG.

LEVEL OF EVIDENCE

Prognostic level III.

Identification of hypercoagulability with thrombelastography in patients with hip fracture receiving thromboprophylaxis

Background:

Venous thromboembolism (VTE) is the second most common complication after hip fracture surgery. We used thrombelastography (TEG), a wholeblood, point-of-care test that can provide an overview of the clotting process, to determine the duration of hypercoagulability after hip fracture surgery.

Methods:

In this prospective study, consecutive patients aged 51 years or more with hip fractures (trochanteric region or neck) amenable to surgical treatment who presented to the emergency department were eligible for enrolment. Thrombelastography, including calculation of the coagulation index (CI) (combination of 4 TEG parameters for an overall assessment of coagulation) was performed daily from admission until 5 days postoperatively, and at 2 and 6 weeks postoperatively. All patients received 28 days of thromboprophylaxis. We used single-sample t tests to compare mean maximal amplitude (MA) values (a measure of clot strength) to the hypercoagulable threshold of greater than 65 mm, a predictor of in-hospital VTE.

Results:

Of the 35 patients enrolled, 11 (31%) were hypercoagulable on admission based on an MA value greater than 65 mm, and 29 (83%) were hypercoagulable based on a CI value greater than 3.0; the corresponding values at 6 weeks were 23 (66%) and 34 (97%). All patients had an MA value greater than 65 mm at 2 weeks. Patients demonstrated normal coagulation on admission (mean MA value 62.2 mm [standard deviation (SD) 6.3 mm], p = 0.01) but became significantly hypercoagulable at 2 weeks (mean 71.6 mm [SD 2.6 mm], p < 0.001). There was a trend toward persistent hypercoagulability at 6 weeks (mean MA value 66.2 mm [SD 3.8 mm], p = 0.06).

Conclusion:

More than 50% of patients remained hypercoagulable 6 weeks after fracture despite thromboprophylaxis. Thrombelastography MA thresholds or a change in MA over time may help predict VTE risk; however, further study is needed.

Plasma D-dimer and FDP are promising biomarkers to predict perioperative fibrinolysis and bleeding following primary total joint arthroplasty: A STROBE compliant article

Perioperative bleeding is associated with postoperative hyperfibrinolysis caused by surgical trauma in the setting of total hip and knee arthroplasty (THA/ TKA). The study aimed to clarify the dynamics of postoperative fibrinolytic activity and the values of fibrin degeneration products and thromboelastography (TEG) to guide precisive antifibrinolytic therapy.Forty three patients undergoing primary unilateral THAs and 40 TKAs were included to the prospective observational cohort study. Venous blood sample at different time points (preoperative, intraoperative, postoperative 6 hours, 12 hours, 24 hours, 48 hours) were drawn to test D-dimer, fibrin (-ogen) degradation products (FDP) and TEG.The TEG parameters associated with coagulation (R, K, α, MA, and CI) and fibrinolysis (estimate percent lysis and Ly30) were all in normal range although had a higher level than preoperative time (P < .05). The postoperative levels of D-dimer and FDP were higher than preoperative level (P < .05). The dynamics of D-dimer and FDP presented a bimodal pattern, which peaked at 6 hours postoperatively, then remained and decreased until 24 hours, but would rebound at 48 hours postoperatively with smaller amplitude. Moreover, FDP6h (P = .028), D-Dimer6h (P = .044), FDP12h (P = .009), D-dimer12h (P = .007), and FDP48h (P = .016) were all correlated with total blood loss on POD3.FDP and D-dimer were effective and practical markers for prediction of acute postoperative fibrinolytic activity, which peaked at 6 hours after end of surgery and would maintain for at least 24 hours.