Thromboprophylaxis and thrombosis in medical, surgical, trauma, and obstetric/gynecologic patients

Aspirin as Venous Thromboembolism Prophylaxis in Arthroplasty Patients: An Analysis of Clinical Practice Guidelines Recommendations

BACKGROUND

Venous thromboembolism (VTE) is a recognized postoperative complication of hip or knee arthroplasty and incurs major morbidity and mortality. While anticoagulants are the mainstay of chemoprophylaxis, aspirin has recently emerged as a popular prophylactic agent. However, there is a lack of high-quality evidence comparing aspirin to anticoagulants as a method of VTE prophylaxis, and current guidelines are conflicting regarding using aspirin as first-line chemoprophylaxis. We aimed to investigate guideline characteristics that are associated with the recommendation for or against aspirin as a first-line agent.

METHODS

MEDLINE, Embase, Cumulative Index to Nursing and Allied Health Literature, and PubMed databases were searched from 1966 to January 2024 to identify clinical practice guidelines for VTE prophylaxis in adult hip or knee arthroplasty inpatients of average risk. The characteristics of the guideline were collected by 2 independent reviewers. Logistic regression was used to test the association between the recommendation for or against aspirin and guideline characteristics.

RESULTS

There were 26 guidelines published from February 2003 to September 2023 and included in this study. There were 5 guidelines that recommended aspirin and 11 guidelines that recommended against aspirin as first-line therapy. With a more recent year of publication, aspirin was more likely to be recommended (odds ratio 1.72, 95% confidence interval: 1.05 to 2.84) and less likely to be recommended against (odds ratio 0.61, 95% confidence interval: 0.41 to 0.90). No other variables, including the level of evidence used, the composition of the guideline working group, or the objective of the guideline, were associated with the recommendation for or against aspirin.

CONCLUSIONS

Guidelines were inconsistent in their recommendations regarding aspirin as first-line therapy as VTE prophylaxis in arthroplasty patients. Adequately powered randomized controlled trials using modern practices, such as early postoperative mobilization, are needed to better inform clinical practice guidelines.

Inherited Factor XII Deficiency—What Is the Real Concern for Neuroanesthesiologist: Bleeding or Clotting

Factor XII deficiency is a rare disorder that can complicate the perioperative management of a patient. Factor XII plays an important role in the activation of intrinsic pathway of coagulation; the deficiency, therefore, results in prolongation of activated partial thromboplastin time (aPTT). This aPTT prolongation is expected to cause increased bleeding during surgery. However, on the contrary, in vivo isolated factor XII deficiency is associated with increased risk of thromboembolism (this risk being higher than the risk of bleeding). We report the perioperative management of a patient with factor XII deficiency who underwent cervical vertebral fusion (C1–C2) for atlantoaxial dislocation.

Characterization of thromboelastography of patients with different pathological types of nephrotic syndrome

To investigate the changes in blood coagulability as measured by thromboelastography (TEG) in patients with nephrotic syndrome of different etiologies as well as in patients with venous thromboembolic events (VTE).From January 2013 to October 2017, patients who were diagnosed as idiopathic membranous nephropathy (IMN), minimal change disease (MCD) and focal segmental glomerulosclerosis (FSGS) were enrolled into this retrospective study in which their clinical characteristics, including TEG variables, were investigated. According to the presence or absence of VTE, the patients with IMN were divided into 2 groups of VTE and non-VTE. The risk factors of VTE were analyzed with logistic regression.Significant differences in TEG parameters were found among the 3 groups of patients with R and K values lower, while the α-angle, maximum amplitude (MA) and confidence interval (CI) values higher, in the IMN group than those in the MCD and FSGS groups (P < .01). Multiple linear regression analysis indicated that the histologic subtype was an independent relevant factor of K time, angle, MA, and CI values. Multivariate logistic regression analysis revealed that serum albumin and CI value were independent risk factors of VTE (P < .05).The results showed that IMN patients may have higher whole blood coagulability than MCD and FSGS patients. The hypercoagulability in IMN patients may be attributed to platelet hyperactivity and the accelerated fibrin-platelet interaction. Hypoproteinemia and increased CI value were independent risk factors of VTE in IMN.

Coagulation and fibrinolysis during lung surgery:an experimental study

OBJECTIVES

Postoperative thromboembolism is a serious complication, but the incidence following surgery for lung cancer appears to be much lower compared with other surgical specialties. The reason is unknown and one may speculate that the lungs are reservoirs of anticoagulants or fibrinolytic substances, which are released by manipulation of the lung parenchyma during surgery.

METHODS

Standardized lung manipulation, single-lung ventilation and pneumonectomy were performed in 10 anaesthetized pigs. Baseline and serial postmanipulation intravenous and intra-arterial blood samples were analysed for a wide range of fibrinolytic substances as well as pro- and anticoagulant factors.

RESULTS

We found a transient but significant decrease in activated partial thromboplastin time (aPTT) and plasminogen activator inhibitor following manipulation of the lungs. Pneumonectomy resulted in minor but significant decrease in antithrombin and a significant increase in aPTT. All other measured substances were virtually constant.

CONCLUSIONS

A wide range of fibrinolytic and anticoagulant substances remained unchanged during experimental lung manipulation. Minor changes were transient and not considered clinically relevant. Future studies should be initiated in humans because we have no deeper understanding why thromboembolic complications are relatively uncommon after general thoracic surgery compared with other surgical specialties.

Traumatic injury may be a predisposing factor for cerebrovascular accident

The purpose of the study was to assess whether trauma may be an independent risk factor for stroke. Evidence has shown that trauma patients experience a hypercoagulable state postinjury, increasing the risk of thrombotic events. A case-controlled, retrospective analysis was performed on admitted trauma patients over a 2-year period. Results revealed that trauma patients are 1.6 times more likely to have a cerebrovascular accident (CVA) during their hospital admission, when compared with nontrauma patients with similar CVA risk factors. Several statistically significant differences between the groups were identified. On the basis of these results, trauma appears to be an independent, nonmodifiable risk factor for CVA.

Progressive postinjury thrombocytosis is associated with thromboembolic complications

BACKGROUND

Our previous investigation demonstrated that despite routine chemoprophylaxis, thrombelastography, which is a comprehensive test measuring the viscoelastic properties of blood, identified a hypercoagulable state in a cohort of critically ill surgical patients that was associated with thromboemobolic events. Furthermore, because thrombelastography allows for the comprehensive assessment of coagulation status, this work suggested that platelet hyperactivity is a component of the hypercoagulable state. We hypothesized that progressive postinjury thrombocytosis contributes to a hypercoagulable state that is associated with thrombelastography.

METHODS

One thousand four hundred and forty severely injured patients surviving >48 h were entered into a database prospectively over 12 years. The variables that were evaluated in associated with thrombocytosis (platelet count >450,000) included age, Injury Severity Score, packed red blood cell transfusions in 12 h, and thromboemobolic complications (TE) (deep venous thrombosis, pulmonary embolus, mesenteric thrombosis, stroke, and arterial thrombosis). The time frame for the development of thrombocytosis was assessed at greater or less than 7 days postinjury. Logistic regression was used to identify the independent variables predictive of thrombocytosis and to adjust the association of thrombocytosis with TE for other risk factors. C-statistic was used to assess the discriminative power of thrombocytosis for prediction of TE.

RESULTS

The mean age was 37.4 ± 0.4 years. The Injury Severity Score was 29.3 ± 0.3, and mean red blood cell transfusions in 12 h was 4.4 ± 0.2 units. Injury via blunt force occurred in 76% of patients, and 72% of patients were male. Thrombocytosis was identified in 447 (31%) patients and was noted almost exclusively >7 days postinjury (98%). TE developed in 35 (8%) of the 447 patients with thrombocytosis, compared with 45 (4.5%) of the remaining 993 patients who did not develop thrombocytosis. Persistent thrombocytosis >7 days was associated with TE (P > .0001). Logistic regression analysis indicated that when adjusted for intensive care unit duration of stay, transfusions, age, and Injury Severity Score, patients with sustained thrombocytosis more than 3 days were noted to have a 1.4 × increased risk of TE (odds ratio, 1.12; 95% confidence interval, 1.04-1.2; P = .002; C-statistic = 0.82).

CONCLUSION

Persistent thrombocytosis in critically injured patients receiving routine chemoprophylaxis is associated with thrombotic complications. Subsequent investigation is warranted to differentiate enzymatic from platelet hypercoagulability to ascertain the role of antiplatelet therapy for prevention of TE.

Rapid thrombelastography (r-TEG) identifies hypercoagulability and predicts thromboembolic events in surgical patients

BACKGROUND

Despite routine prophylaxis, thromboembolic events (TEs) in surgical patients remain a substantial problem. Furthermore, the timing and incidence of hypercoagulability, which predisposes to these events is unknown, with institutional screening programs serving primarily to establish a diagnosis after an event has occurred. Emerging evidence suggests that point of care (POC) rapid thrombelastography (r-TEG) provides a real-time analysis of comprehensive thrombostatic function, which represents an analysis of both enzymatic and platelet components of thrombus formation. We hypothesized that r-TEG can be used as a screening tool to identify hypercoagulable states in surgical patients and would predict subsequent thromboembolic events.

METHODS

Rapid thrombelastography r-TEG analyses were performed on 152 critically ill patients in the surgical intensive care unit (ICU) during 7 months. Hypercoagulability was defined as clot strength (G)>12.4 dynes/cm(2). Variables of interest for identifying hypercoagulability and thromboembolic events included sex, age, operating hospital service, specific injury patterns, injury severity score (ISS), transfusion within first 24 h, ICU duration of stay, ventilator days, hospital admission days, and thromboprophylaxis. Comparisons between the hypercoagulable and normal groups or between the groups with and without thromboembolic events were performed using Chi-square tests or the Fisher exact test for categorical variables and independent sample t tests or Wilcoxon rank sum tests for continuous variables. Multivariate logistic regression analysis (LR) was performed to identify independent predictors of thromboembolic events. A receiver operating characteristic curve was used to measure the performance of G for predicting the occurrence of a TE event. All tests were 2-sided with significance of P < .05.

RESULTS

In all, 86 patients (67%) were hypercoagulable by r-TEG. More than 85% of patients in the hypercoagulable group and 79% in the normal group received thromboprophylaxis during the study period. The differences between hypercoagulable and normal groups by bivariate analysis included high-risk injuries (52% vs 35%; P = .03), spinal cord injury (27% vs 12%; P = .03), median ICU duration of stay (13 vs 7 days; P < .001), median ventilator days (6 vs 2; P < .001), and median hospital duration of stay (20 vs 13 days; P < .001). A total of 16 patients (19%) of the hypercoagulable group suffered a thromboembolic event, and 10 hypercoagulable patients (12%) had thromboembolic events predicted by prior r-TEG hypercoagulability. No patients with normal coagulability by r-TEG had an event (P < .001). LR analysis showed that the strongest predictor of TE after controlling for the presence of thromboprophylaxis was elevated G value (odds ratio: 1.25, 95% confidence interval [CI]: 1.12-1.39). For every 1 dyne/cm(2) increase in G, the odds of a TE increased by 25%.

CONCLUSION

These results indicate that the presence of hypercoagulability identified by r-TEG is predictive of thromboembolic events in surgical patients. Subsequent study is necessary to define optimal prophylactic treatment strategies for patients with r-TEG proven hypercoagulability.

Does thromboelastography predict postoperative thromboembolic events? A systematic review of the literature

BACKGROUND

Since thromboelastography (TEG) can detect hypercoagulable states, it is a potentially useful test for predicting postoperative thromboembolic complications. Therefore, we performed a systematic review of the literature to evaluate the accuracy of TEG in predicting postoperative thromboembolic events.

METHODS

PUBMED and EMBASE electronic databases were searched by two independent investigators to identify prospective studies involving adult patients undergoing operative procedures in which a TEG test was performed perioperatively and outcomes were measured by reference standards. The quality of included studies was assessed and measures of diagnostic test accuracy were estimated for each included study.

RESULTS

Ten studies (with a total of 1056 patients) were included in this analysis; however, only five reported measures of TEG test accuracy. The overall quality of the studies and level of diagnostic evaluation of the studies were highly variable, from poor to good. As there were variations in the definition of hypercoagulability, TEG methodology and patient characteristics, reference standards used and outcomes measured, a meta-analysis was not undertaken. The sensitivity and specificity ranged from 0% to 100% and 62% to 92%, respectively. The diagnostic odds ratio ranged from 1.5 to 27.7; area under the curve ranged from 0.57 to 0.91. Of the TEG variables, maximum amplitude seems to be the best parameter to identify hypercoagulable states and to predict thromboembolic events.

CONCLUSIONS

The predictive accuracy of TEG for postoperative thromboembolic events is highly variable. To determine if the TEG is a clinically useful screening test in high-risk surgical populations, more prospective studies are needed.

Primary prophylaxis of venous thromboembolism in surgical patients

Venous thromboembolism is a major risk for surgical patients during the perioperative period. Prevention of perioperative venous thromboembolism remains a critical component of surgical patient care. The risk for venous thromboembolism in surgical patients can be stratified by their risk factors and by the type of operation. Pharmacological prophylaxis for venous thromboembolism includes unfractionated heparin, low-molecular weight heparin, fondaparinux, warfarin, antiplatelet therapy, and direct thrombin inhibitors. Mechanical devices such as graduated compression stockings, intermittent pneumatic compressions, and venous foot pumps are also effective modalities for venous thromboembolism prophylaxis. The optimal preventive measure of venous thromboembolism should be based on the degree of risk for venous thromboembolism with the intensity of prophylaxis while balancing potential treatment benefits and risks in each individual patient. The epidemiology of venous thromboembolism, the methods for achieving venous thromboembolism prophylaxis, and the approach to institute venous thromboembolism prophylaxis in surgical patients undergoing various operative interventions are reviewed in this article.

Anesthesia in pregnant patients for nonobstetric surgery

Anesthesiologists in every subspecialty encounter, with varying regularity, patients presenting for surgery during the course of pregnancy. With the increasing sophistication of surgical and anesthetic techniques, increasingly complex surgeries are being undertaken. In this review, we address the fundamental physiologic principles central to the care of pregnant patients and fetuses in this difficult clinical situation.

Thrombosis and Coagulation: Deep Vein Thrombosis and Pulmonary Embolism Prophylaxis

Venous thromboembolism (deep venous thrombosis and pulmonary embolism, VTE) is a common complication in surgical patients and is the primary cause of preventable deaths in hospitalized patients. Despite well-known risk factors, VTE prophylaxis is frequently not practiced according to recommended guidelines. Patients can readily be stratified according to their risk of perioperative VTE, and mechanical and pharmacologic prophylactic regimens can be tailored to their individual risk. Pharmacologic VTEprophylaxis should be the standard of care in most clinical settings given its ease of administration, low risk, and cost-effectiveness.

Thromboelastography maximum amplitude predicts postoperative thrombotic complications including myocardial infarction

Postoperative thrombotic complications increase hospital length of stay and health care costs. Given the potential for thrombotic complications to result from hypercoagulable states, we sought to determine whether postoperative blood analysis using thromboelastography could predict the occurrence of thrombotic complications, including myocardial infarction (MI). We prospectively enrolled 240 patients undergoing a wide variety of surgical procedures. A cardiac risk score was assigned to each patient using the established revised Goldman risk index. Thromboelastography was performed immediately after surgery and maximum amplitude (MA), representing clot strength, was determined. Postoperative thrombotic complications requiring confirmation by a diagnostic test were assessed by a blinded observer. Ten patients (4.2%) suffered a total of 12 postoperative thrombotic complications. The incidence of thrombotic complications with increased MA (8 of 95 = 8.4%) was significantly (P = 0.0157) more frequent than that of patients with MA < or =68 (2 of 145 = 1.4%). Furthermore, the percentage suffering postoperative MI in the increased MA group (6 of 95 = 6.3%) was significantly larger than that in the MA < or =68 group (0 of 145 = 0%) (P = 0.0035). In a multivariate analysis, increased MA (P = 0.013; odds ratio, 1.16; 95% confidence interval, 1.03-1.20) and Goldman risk score (P = 0.046; odds ratio, 2.39; 95% confidence interval, 1.02-5.61) both independently predicted postoperative MI. A postoperative hypercoagulable state as determined by thromboelastography is associated with postoperative thrombotic complications, including MI, in a diverse group of surgical patients.

Molecular and pharmacologic profile of tinzaparin and a comparable low-molecular-weight bacterial sulfaminoheparosan

Low-molecular-weight heparins (LMWH) represent depolymerized porcine mucosal heparin derivatives, which are commonly used for the management of thrombotic disorders. Because of their widespread usage, the supplies of the raw material namely unfractionated heparin are nearly exhausted. Porcine mucosal tissue is almost exclusively used for the preparation of these agents. Thus, there is a timely need for the production of heparin like drugs from other sources. Fermentation techniques have been used to produce carbohydrates such as dextran and innulin for therapeutic purposes. Bacterial cell wall polysaccharide mimics the linear hexose units, which constitute heparin. Utilizing Escherichia coli cell membranes produced by fermentation technology, chemical sulfation and enzymatic epimerization, sulfaminoheparosan type of polymer mimicking the structure of heparin has been produced. These semi-synthetic sulfaminoheparosans exhibit biologic actions comparable to that observed with heparin. The sulfaminoheparosan core can also be degraded to obtain low-molecular-weight (LMW) derivatives mimicking LMWHs. Using this technique, a novel LMW sulfaminoheparosan derivative (Q93C/239) was produced by Inalco, Milan, Italy. To compare this heparin analogue, a LMWH, namely tinzaparin, was used to determine the relative anticoagulant, antiprotease, and molecular profile. Additional studies were carried out to determine the susceptibility of this agent to heparinase-I. These comparative studies exhibited both antiprotease and anticoagulant properties similar to those of tinzaparin. However LMW sulfaminoheparosan resisted heparinase-I digestion at low heparinase-I concentrations. These studies demonstrate that the sulfaminoheparosan derived LMW components exhibit similar molecular and anticoagulant profile as tinzaparin and warrant additional preclinical and clinical development to determine their potential usefulness as antithrombotic agents.