The Impact of Once- versus Twice-Daily Enoxaparin Prophylaxis on Risk for Venous Thromboembolism and Clinically Relevant Bleeding:

Unfractionated Heparins, Low-Molecular-Weight Heparins, and Indirect Factor Xa Inhibitors in Plastic and Reconstructive Surgery: An Evidence-Based Review

SUMMARY

Venous thromboembolism can present with devastating complications and sequalae, particularly in the surgical patient. Current data support prophylactic anticoagulant use in high-risk hospitalized patients, defined as those with a Caprini Risk Assessment Model score of 7 or greater. The most frequently used chemoprophylaxis agents include unfractionated heparin, low-molecular-weight heparin, and indirect factor Xa inhibitors. The authors review the mechanisms of action, metabolism, reversal agents, indications, contraindications, advantages, and disadvantages of these medications in plastic and reconstructive surgery.

Comparison of Standard Versus Intermediate Prophylaxis Dose for Venous Thromboembolism Prophylaxis in Patients Hospitalized With COVID-19 Infection

Background: COVID-19 infection is associated with a high risk of venous thromboembolism (VTE) events. VTE prophylaxis reduces the risk of these events. The optimal dose of VTE prophylaxis however remains uncertain. Objectives: To compare the incidence of VTE in patients treated with either standard dose VTE versus intermediate dose VTE prophylaxis. Methods: In this retrospective cohort study, we analyzed data from 1786 adult patients admitted into the hospital with polymerase chain reaction confirmed COVID-19 infection between April 2020 to September 2021. For analysis, patients were divided into 2 cohorts: either standard dose prophylaxis treatment group (patients who received either unfractionated heparin 5000units 3 times a day or enoxaparin 30-40 mg daily subcutaneously) or intermediate dose VTE prophylaxis group (patients received either unfractionated heparin 7500 units 3 times daily or enoxaparin 30-40 mg twice a day subcutaneously). The primary outcome was incidence of VTE events described as either deep vein thrombosis (DVT) or pulmonary embolism (PE). Secondary outcome was bleeding events. Results: During the study period, 398 (22%) patients were primarily treated with standard dose VTE prophylaxis, whereas 1388 (78%) patients were treated with intermediate dose VTE prophylaxis. There was a significantly higher incidence of venous thromboembolism events noted in the standard dose prophylaxis treatment group when compared with the intermediate dose prophylaxis group (25/398 (6.3%) vs 35/1388 (2.5%) P < .001, [Odds Ratio 2.6197, 95% confidence interval = 1.5482-4.4327]). Multivariable-adjusted logistic regression, adjusting for age, obesity, and smoking, with the intermediate dose prophylaxis treatment group as the referent category revealed higher odds for incident venous thromboembolism events in the standard dose prophylaxis group. There was no statistically significant difference in bleeding events between the 2 treatment groups (9 (2.3%) for standard dose prophylaxis group vs 46 (3.3%) for intermediate dose prophylaxis group P = .26). Conclusions: Among patients hospitalized with COVID-19 infection, patients receiving intermediate dose VTE prophylaxis experienced lower incident rates of venous thromboembolism events compared to those receiving standard dose VTE prophylaxis without a statistically significant increase in the risk of bleeding events.

Methodological Quality of Open Access Compared to Traditional Journal Publications in the Plastic Surgery Literature

BACKGROUND

The methodological quality of open access studies has long been questioned due to increasing popularity and accessibility. The objective of this study is to compare the methodological quality of open access versus traditional journal publications in the plastic surgery literature.

METHODS

Four traditional plastic surgery journals with their sister open access journals were chosen. For each of the eight journals, 10 articles were randomly selected for inclusion. Methodological quality was examined using validated instruments. Publication descriptors were compared to methodological quality values using ANOVA. Logistic regression was used to compare quality scores between open access and traditional journals.

RESULTS

There was a wide distribution of levels of evidence, with a quarter being level one. Regression of non-randomized studies indicated a significantly higher proportion of traditional journal articles were of high methodological quality (89.6%) when compared to open access journals (55.6%; p < 0.05). This difference persisted in three quarter of the sister journal groups. No publication descriptions were associated with methodological quality.

CONCLUSIONS

Methodological quality scores were higher among traditional access journals. Higher degrees of peer review may be necessary to ensure appropriate methodological quality in open access plastic surgery publications.

LEVEL OF EVIDENCE V

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Acetylsalicylic Acid is Not Associated With Improved Clinical Outcomes After Microsurgical Breast Reconstruction

INTRODUCTION

Microvascular thrombosis with resultant flap loss remains a devastating complication in autologous breast reconstruction. While acetylsalicylic acid (ASA) for prevention of microvascular thrombosis is commonly administered postoperatively, clinical evidence supporting this practice remains insufficient. Here, we investigate the association of postoperative ASA administration with differences in clinical outcomes following microsurgical breast reconstruction.

METHODS

A prospectively maintained database was queried to identify patients who had undergone microsurgical breast reconstruction. Patients were categorized based on whether they had received postoperative ASA for 30 d (Group 1) or had not received ASA (Group 2). Patient demographics, reconstructive outcomes, complications, and transfusion requirements were retrieved.

RESULTS

One hundred thirty six patients with a mean age of 49.5 y and a mean body mass index of 28.5 kg/m² who had undergone a total of 216 microsurgical breast reconstructions were included. No significant differences were noted with regard to patient demographics with the exceptions of increased rates of neoadjuvant chemotherapy and delayed reconstruction in Group 1. There were no significant differences in the rates of postoperative complications including breast hematoma, mastectomy skin flap necrosis, partial flap necrosis, seroma, and deep venous thrombosis between patients who did or did not receive ASA postoperatively. Similarly, no difference was noted regarding postoperative blood transfusion rates (Group 1: 9.9% versus Group 2: 9.1%; P = 0.78). Finally, patients in Group 1 had significantly longer hospital stays (Q1 = 4, median = 4.5, Q3 = 5).

CONCLUSIONS

Postoperative ASA administration is not associated with improved postoperative clinical outcomes. The use of ASA routinely after autologous breast reconstruction does not appear to be a necessity in practice.

Venous Thromboembolism Rates After Free Flap Reconstruction of the Head and Neck Region

BACKGROUND

Venous thromboembolism (VTE) is a major concern for the postoperative hospitalized patient, especially after long and complex procedures. Cancer itself also contributes to the hypercoagulable state, further complicating the management of patients. Despite prophylaxis, breakthrough events can occur. We aimed to assess our institutional VTE and bleeding rates after free flap reconstruction of the head and neck (H&N) region and the factors associated with VTE events.

METHODS

A retrospective review of the patients who underwent H&N free flap reconstruction at an academic center from 2012 to 2021 was performed from a prospectively maintained database. Data regarding patient demographics, medical history, surgical details, and overall outcomes were collected. Outcomes studied included postoperative 30-day VTE rates and major bleeding events. Patients who had a VTE event were compared with the rest of the cohort to identify factors associated with VTE.

RESULTS

Free flap reconstruction of the H&N region was performed in 949 patients. Reconstruction after cancer extirpation for squamous cell carcinoma was the most common etiology (79%). The most common flap was thigh based (50%), followed by the fibula (29%). The most common postoperative VTE chemoprophylaxis regimen was enoxaparin 30 mg twice daily (83%). The VTE and bleeding rates over the 10-year period were 4.6% (n = 44) and 8.7% (n = 83), respectively. Body mass index (28.7 ± 5.8 vs 26.2 ± 6.6, P = 0.013) and pulmonary comorbidities were found to be significantly higher in patients who had a VTE event (43% vs 27%, P = 0.017). Patients with a VTE event had a prolonged hospital stay of 8 more days (19.2 ± 17.4 vs 11 ± 7, P = 0.003) and a higher incidence of bleeding events (27% vs 8%, P < 0.001).

CONCLUSIONS

Postoperative VTE is a significant complication associated with increased length of hospitalization in patients undergoing free flap reconstruction of the H&N region. Institutional measures should be implemented on an individualized basis based on patient comorbidities to improve the postoperative VTE rates, while balancing the bleeding events.

Chemoprophylaxis and Management of Venous Thromboembolism in Microvascular Surgery

This review aims to highlight the common pharmacological and nonpharmacological interventions utilized for thromboprophylaxis as well as flap salvage in microsurgery. A literature review was conducted in PubMed/National Center for Biotechnology Information, Scopus, Web of Science, and MEDLINE databases. Articles with a focus on thromboprophylaxis in microsurgical procedures spanning head and neck surgery, breast and extremity microvascular reconstruction, deep venous thrombosis/pulmonary embolus in microvascular surgery, and flap thrombosis and salvage were included in this review. The majority of available evidence supports mechanical venous thromboembolism (VTE) prophylaxis in all patients undergoing microsurgery given the presence of multiple risk factors for VTE within this particular patient population. Based on the literature review, addition of VTE chemoprophylactic agents is beneficial and an algorithmic approach to thromboprophylaxis in microsurgery patients and management of patients with thrombosis based on literature review and senior authors' experience is recommended and outlined.

Assessment of BMI and Venous Thromboembolism Rates in Patients on Standard Chemoprophylaxis Regimens After Undergoing Free Tissue Transfer to the Head and Neck

Importance

Venous thromboembolism (VTE) is a severe complication after free tissue transfer to the head and neck (H&N). Enoxaparin 30 mg twice daily (BID) is a common regimen for chemoprophylaxis. However, differences in enoxaparin metabolism based on body weight may influence its efficacy and safety profile.

Objective

To assess the association between BMI and postoperative VTE and hematoma rates in patients treated with prophylactic enoxaparin 30 mg BID.

Design, Setting, and Participants

This was a retrospective review of a prospectively collected cohort from 2012 to 2022. Postoperative VTE, hematoma, and free flap pedicle thrombosis were recorded within 30 days of index surgery. The setting was a tertiary academic referral center. Participants included patients undergoing H&N reconstruction with free flaps that received fixed-dose subcutaneous enoxaparin 30 mg BID postoperatively. Statistical analysis was conducted from April to May 2022.

Main Outcomes and Measures

Outcomes include incidence of VTE, hematoma, and flap pedicle thrombosis events within 30 days of the surgery. Univariate and multivariable regression models were used to evaluate associations between BMI and other patient factors with these outcomes.

Results

Among the 765 patients included, 262 (34.24%) were female; mean (SD) age was 60.85 (12.64) years; and mean (SD) BMI was 26.36 (6.29). The rates of VTE and hematoma in the cohort were 3.92% (30 patients) and 5.09% (39 patients), respectively. After adjusting for patient factors, BMI was the only factor associated with VTE (OR, 1.07; 95% CI, 1.015-1.129). Obesity (BMI >30) was associated with increased odds of VTE (OR, 2.782; 95% CI, 1.197-6.564). Hematoma was not associated with BMI (OR, 0.988; 95% CI, 0.937-1.041). Caprini score of at least 9 was not associated with VTE (OR, 1.259; 95% CI, 0.428-3.701).

Conclusions and Relevance

This cohort study found that obesity was associated with an increased risk of VTE in patients after microvascular H&N reconstruction and while on standard postoperative chemoprophylaxis regimens. This association may suggest insufficient VTE prophylaxis in this group and a potential indication for weight-based dosing.

Optimizing Perioperative Venous Thromboembolism Chemoprophylaxis on a Gynecologic Oncology Service

BACKGROUND

Perioperative venous thromboembolism (VTE) is a significant cause of morbidity and mortality after gynecologic cancer surgery. Here we report a quality improvement intervention to increase perioperative VTE chemoprophylaxis compliance.

STUDY DESIGN

All operations performed by a gynecologic oncologist at a tertiary urban university medical center admitted to the hospital for at least one midnight were included. Using a pre/post design with a washout period, we sought to increase perioperative VTE chemoprophylaxis compliance from 22% in the historical control (HC) cohort to 90% in the quality improvement (QI) cohort. The perioperative VTE chemoprophylaxis process was standardized by addressing four domains: preoperative VTE chemoprophylaxis, surgical time-out, postoperative VTE chemoprophylaxis, and intervention education and compliance tracking. Pearson's chi-square test was used to compare HC vs QI cohort compliance.

RESULTS

There were 130 surgical cases in the HC cohort and 131 in the QI cohort. Forty-two percent underwent laparotomy, and 57% had cancer at the time of operation. VTE chemoprophylaxis compliance improved from 22% in the HC cohort to 82% in the QI cohort (p < 0.001). Preoperative VTE chemoprophylaxis compliance improved from 76% in the HC cohort to 94% in the QI cohort (p < 0.001), and postoperative VTE chemoprophylaxis compliance improved from 27% to 87% (p < 0.001). Thirty-day postoperative VTE occurred in three patients (2%) in the HC cohort and none in the QI cohort (p = 0.08).

CONCLUSIONS

A low-cost and low-technology QI initiative intervention improved perioperative compliance with VTE chemoprophylaxis.

Enoxaparin titrated by anti-Xa levels reduces venous thromboembolism in trauma patients

BACKGROUND

Trauma is a major risk factor for the development of a venous thromboembolism (VTE). After observing higher than expected VTE rates within our center's Trauma Quality Improvement Program data, we instituted a change in our VTE prophylaxis protocol, moving to enoxaparin dosing titrated by anti-Xa levels. We hypothesized that this intervention would lower our symptomatic VTE rates.

METHODS

Adult trauma patients at a single institution meeting National Trauma Data Standard criteria from April 2015 to September 2019 were examined with regards to VTE chemoprophylaxis regimen and VTE incidence. Two groups of patients were identified based on VTE protocol-those who received enoxaparin 30 mg twice daily without routine anti-Xa levels ("pre") versus those who received enoxaparin 40 mg twice daily with dose titrated by serial anti-Xa levels ("post"). Univariate and multivariate analyses were performed to define statistically significant differences in VTE incidence between the two cohorts.

RESULTS

There were 1698 patients within the "pre" group and 1406 patients within the "post" group. The two groups were essentially the same in terms of demographics and risk factors for bleeding or thrombosis. There was a statistically significant reduction in VTE rate (p = 0.01) and deep vein thrombosis rate (p = 0.01) but no significant reduction in pulmonary embolism rate (p = 0.21) after implementation of the anti-Xa titration protocol. Risk-adjusted Trauma Quality Improvement Program data showed an improvement in rate of symptomatic pulmonary embolism from fifth decile to first decile.

CONCLUSION

A protocol titrating prophylactic enoxaparin dose based on anti-Xa levels reduced VTE rates. Implementation of this type of protocol requires diligence from the physician and pharmacist team. Further research will investigate the impact of protocol compliance and time to appropriate anti-Xa level on incidence of VTE.

LEVEL OF EVIDENCE

Therapeutic/care management, Level IV.

A Review of Venous Thromboembolism Risk Assessment and Prophylaxis in Plastic Surgery

BACKGROUND

Venous thromboembolism is a significant cause of postoperative death and morbidity. While prophylactic and treatment regimens exist, they usually come with some risk of clinically relevant bleeding and, thus, must be considered carefully for each individual patient.

METHODS

This special topic article represents a review of current evidence regarding venous thromboembolism risk, biology, and prevention in plastic surgery patients. The specific types and duration of available prophylaxis are also reviewed. The balance of venous thromboembolism risk must be weighed against the risk of hemorrhage.

RESULTS

Though alternatives exist, the most validated risk assessment tool is the 2005 modification of the Caprini Risk Assessment Model. Controversies remain regarding recommendations for outpatient and low risk cosmetic patients. The authors additionally make recommendations for high-risk patients regarding the use of tranexamic acid, estrogen therapy, anesthesia, and prophylaxis regimens.

CONCLUSION

Our profession has made great strides in understanding the science behind venous thromboembolism, risk stratification for patients, and prophylactic regimens; yet, continued studies and definitive data are needed.

Optimal Dosing of Prophylactic Enoxaparin after Surgical Procedures: Results of the Double-Blind, Randomized, Controlled FIxed or Variable Enoxaparin (FIVE) Trial

BACKGROUND

The accepted "one-size-fits-all" dose strategy for prophylactic enoxaparin may not optimize the medication's risks and benefits after surgical procedures. The authors hypothesized that weight-based administration might improve the pharmacokinetics of prophylactic enoxaparin when compared to fixed-dose administration.

METHODS

The FIxed or Variable Enoxaparin (FIVE) trial was a randomized, double-blind trial that compared the pharmacokinetic and clinical outcomes of patients assigned randomly to postoperative venous thromboembolism prophylaxis using enoxaparin 40 mg twice daily or enoxaparin 0.5 mg/kg twice daily. Patients were randomized after surgery and received the first enoxaparin dose at 8 hours after surgery. Primary hypotheses were (1) weight-based administration is noninferior to a fixed dose for avoiding underanticoagulation (anti-factor Xa <0.2 IU/ml) and (2) weight-based administration is superior to fixed-dose administration for avoiding overanticoagulation (anti-factor Xa >0.4 IU/ml). Secondary endpoints were 90-day venous thromboembolism and bleeding.

RESULTS

In total, 295 patients were randomized, with 151 assigned to fixed-dose and 144 to weight-based administration of enoxaparin. For avoidance of under anticoagulation, weight-based administration had a greater effectiveness (79.9 percent versus 76.6 percent); the 3.3 percent (95 percent CI, -7.5 to 12.5 percent) greater effectiveness achieved statistically significant noninferiority relative to the a priori specified -12 percent noninferiority margin (p = 0.004). For avoidance of overanticoagulation, weight-based enoxaparin administration was superior to fixed-dose administration (90.6 percent versus 82.2 percent); the 8.4 percent (95 percent CI, 0.1 to 16.6 percent) greater effectiveness showed significant safety superiority (p = 0.046). Ninety-day venous thromboembolism and major bleeding were not different between fixed-dose and weight-based cohorts (0.66 percent versus 0.69 percent, p = 0.98; 3.3 percent versus 4.2 percent, p = 0.72, respectively).

CONCLUSION

Weight-based administration showed superior pharmacokinetics for avoidance of underanticoagulation and overanticoagulation in postoperative patients receiving prophylactic enoxaparin.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, I.

Safety of Rivaroxaban for Postoperative Venous Thromboembolism Prophylaxis Following Abdominal Body Contouring Surgery: 600 Patients

BACKGROUND

Reducing the incidence of venous thromboembolism (VTE) following abdominal body contouring surgery remains a top priority for patient safety. There is a lack of consensus regarding the optimal chemoprophylactic agent for postoperative VTE prophylaxis, and the role of oral anticoagulants warrants further investigation.

OBJECTIVES

The aim of this multisurgeon, single-institution study was to determine the safety and efficacy of a 7-day postoperative rivaroxaban regimen for VTE prophylaxis in abdominal body contouring surgery.

METHODS

A retrospective chart review was performed of all patients who underwent abdominoplasty, circumferential body lift, fleur-de-lis panniculectomy, or circumferential fleur-de-lis panniculectomy at our surgical center from August 2014 to November 2019. A 7-day postoperative course of once-daily 10 mg rivaroxaban, starting on postoperative day 1, was administered to every patient unless there was a contraindication. The 2 primary endpoints were the incidence of VTE and bleeding events.

RESULTS

A total of 600 patients were included in the study. There were no deaths. There were 4 (0.7%) incidents of VTE events: 2 (0.3%) patients suffered pulmonary embolus and 2 (0.3%) patients suffered a lower-extremity deep venous thrombosis. A total of 13 (2.2%) patients suffered complications related to bleeding. Of these, operative intervention for control and evacuation was required in 7 (1.2%) patients.

CONCLUSIONS

A 7-day postoperative course of once-daily rivaroxaban for VTE risk reduction in abdominal body contouring surgery is associated with a low incidence of VTE events and a low risk of bleeding complications.

LEVEL OF EVIDENCE: 4

The Impact of Coagulopathy on Clinical Outcomes following Microsurgical Breast Reconstruction

SUMMARY

Autologous breast reconstruction has evolved considerably from pedicled muscle-based approaches to microsurgical perforator-based techniques. Patients with documented coagulopathy, however, remain a particularly challenging population. The authors present their experience in microsurgical breast reconstruction in patients with coagulopathy and discuss their treatment protocol. A prospectively maintained database was queried for patients with coagulopathy who underwent microsurgical breast reconstruction between 2016 and 2019. Information regarding patient demographics, type of coagulopathy, and anticoagulation regimen were retrieved, and clinical outcomes were investigated. Nineteen patients who underwent 34 microsurgical breast reconstructions with free abdominal flaps were included in the study. The most common coagulopathy was factor V Leiden [n = 7 (38.6 percent)]. Nine patients (47.4 percent) developed thrombotic complications (the majority occurring intraoperatively); notably, arterial and venous thrombosis in four (21.1 percent) and two patients (10.5 percent), respectively. Postoperative thrombotic complications included pulmonary embolism [n = 2 (10.5 percent)] and flap congestion secondary to venous thrombosis [two flaps (5.9 percent)]. Only one flap loss was observed secondary to delayed venous thrombosis on postoperative day 6 (2.9 percent). The anticoagulation regimen in the majority of patients consisted of intraoperative intravenous administration of heparin (2000 U [bolus]) followed by a 5-day heparin infusion at 500 U/hour [n = 10 (52.6 percent)]. The high rate of thrombotic complications in patients with coagulopathy who underwent microsurgical breast reconstruction is contrasted by a low flap loss rate. Although coagulopathy is a risk factor for thrombotic complications, successful microsurgical breast reconstruction is still possible in the majority of patients.

Effect of Intermediate-Dose vs Standard-Dose Prophylactic Anticoagulation on Thrombotic Events, Extracorporeal Membrane Oxygenation Treatment, or Mortality Among Patients With COVID-19 Admitted to the Intensive Care Unit: The INSPIRATION Randomized Clinical Trial

IMPORTANCE

Thrombotic events are commonly reported in critically ill patients with COVID-19. Limited data exist to guide the intensity of antithrombotic prophylaxis.

OBJECTIVE

To evaluate the effects of intermediate-dose vs standard-dose prophylactic anticoagulation among patients with COVID-19 admitted to the intensive care unit (ICU).

DESIGN, SETTING, AND PARTICIPANTS

Multicenter randomized trial with a 2 × 2 factorial design performed in 10 academic centers in Iran comparing intermediate-dose vs standard-dose prophylactic anticoagulation (first hypothesis) and statin therapy vs matching placebo (second hypothesis; not reported in this article) among adult patients admitted to the ICU with COVID-19. Patients were recruited between July 29, 2020, and November 19, 2020. The final follow-up date for the 30-day primary outcome was December 19, 2020.

INTERVENTIONS

Intermediate-dose (enoxaparin, 1 mg/kg daily) (n = 276) vs standard prophylactic anticoagulation (enoxaparin, 40 mg daily) (n = 286), with modification according to body weight and creatinine clearance. The assigned treatments were planned to be continued until completion of 30-day follow-up.

MAIN OUTCOMES AND MEASURES

The primary efficacy outcome was a composite of venous or arterial thrombosis, treatment with extracorporeal membrane oxygenation, or mortality within 30 days, assessed in randomized patients who met the eligibility criteria and received at least 1 dose of the assigned treatment. Prespecified safety outcomes included major bleeding according to the Bleeding Academic Research Consortium (type 3 or 5 definition), powered for noninferiority (a noninferiority margin of 1.8 based on odds ratio), and severe thrombocytopenia (platelet count <20 ×103/µL). All outcomes were blindly adjudicated.

RESULTS

Among 600 randomized patients, 562 (93.7%) were included in the primary analysis (median [interquartile range] age, 62 [50-71] years; 237 [42.2%] women). The primary efficacy outcome occurred in 126 patients (45.7%) in the intermediate-dose group and 126 patients (44.1%) in the standard-dose prophylaxis group (absolute risk difference, 1.5% [95% CI, -6.6% to 9.8%]; odds ratio, 1.06 [95% CI, 0.76-1.48]; P = .70). Major bleeding occurred in 7 patients (2.5%) in the intermediate-dose group and 4 patients (1.4%) in the standard-dose prophylaxis group (risk difference, 1.1% [1-sided 97.5% CI, -∞ to 3.4%]; odds ratio, 1.83 [1-sided 97.5% CI, 0.00-5.93]), not meeting the noninferiority criteria (P for noninferiority >.99). Severe thrombocytopenia occurred only in patients assigned to the intermediate-dose group (6 vs 0 patients; risk difference, 2.2% [95% CI, 0.4%-3.8%]; P = .01).

CONCLUSIONS AND RELEVANCE

Among patients admitted to the ICU with COVID-19, intermediate-dose prophylactic anticoagulation, compared with standard-dose prophylactic anticoagulation, did not result in a significant difference in the primary outcome of a composite of adjudicated venous or arterial thrombosis, treatment with extracorporeal membrane oxygenation, or mortality within 30 days. These results do not support the routine empirical use of intermediate-dose prophylactic anticoagulation in unselected patients admitted to the ICU with COVID-19.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT04486508.

Release characteristics of enoxaparin sodium-loaded polymethylmethacrylate bone cement

BACKGROUND

This study aimed to prepare the polymethylmethacrylate (PMMA) bone cement release system with different concentrations of enoxaparin sodium (ES) and to investigate the release characteristics of ES after loading into the PMMA bone cement.

METHODS

In the experimental group, 40 g Palacos®R PMMA bone cement was loaded with various amount of ES 4000, 8000, 12,000, 16,000, 20,000, and 24,000 AXaIU, respectively. The control group was not loaded with ES. Scanning electron microscopy (SEM) was used to observe the surface microstructure of the bone cement in the two groups. In the experiment group, the mold was extracted continuously with pH7.4 Tris-HCL buffer for 10 days. The extract solution was collected every day and the anti-FXa potency was measured. The experiment design and statistical analysis were conducted using a quantitative response parallel line method.

RESULTS

Under the SEM, it was observed that ES was filled in the pores of PMMA bone cement polymer structure and released from the pores after extraction. There was a burst effect of the release. The release amount of ES on the first day was 0.415, 0.858, 1.110, 1.564, 1.952, and 2.513, respectively, from the six groups with various ES loading amount of 4000, 8000, 12,000, 16,000, 20,000, and 24,000 AXaIU, all reaching the peak of release on the first day. The release decreased rapidly on the next day and entered the plateau phase on the fourth day.

CONCLUSION

The prepared ES-PMMA bone cement has high application potential in orthopedic surgery. ES-PMMA bone cement shows good drug release characteristics. The released enoxaparin sodium has a local anti-coagulant effect within 24 h after application, but it will not be released for a long time, which is complementary to postoperative anti-coagulation therapy.

Venous thromboembolism in burns patients: Are we underestimating the risk and underdosing our prophylaxis?

BACKGROUND

Burns patients exhibit all factors of Virchow's triad and are thus at high theoretical risk of venous thromboembolism (VTE). At our tertiary referral burns unit, a standard dose of low molecular weight heparin, which acts primarily by inhibiting Factor Xa, is given for thromboprophylaxis. However, the pharmacokinetics of enoxaparin are altered following a burn injury, and thus burns patients are likely underdosed on their thromboprophylaxis. The objectives of this study were to determine the incidence and risk factors for VTE among burns patients at the Victorian Adult Burns Service (VABS) and to determine the adequacy of the current enoxaparin thromboprophylaxis regimen through measurement of anti-factor Xa (AFXa) levels and comparison with established reference ranges.

METHODS

This study consisted of two parts. In part 1, the Burns Registry of Australia and New Zealand (BRANZ) was reviewed for cases of VTE in burns patients admitted to the VABS from 2013 - 2018. Part 2 was a prospective study that determined peak and trough AFXa levels in patients admitted to the VABS with >10% total body surface area (TBSA) burns.

RESULTS

Part 1. Totally, 1,475 patients were admitted to the VABS between 2013 - 2018. There were 20 cases of VTE (1.36%). Percent TBSA of burn (OR = 1.04, 95% CI: 1.03 - 1.06), full thickness burns (OR = 2.78, 95% CI: 1.15 - 6.73), ICU admission (OR = 15.08, 95% CI: 5.01 - 45.44), mechanical ventilation (OR = 10.62, 95% CI: 4.05 - 27.91), operative procedures (OR = 1.43, 95% CI: 1.29 - 1.59), and a longer hospital stay (OR = 1.05, 95% CI: 1.04 - 1.07) were all associated with an increased VTE risk. Part 2. A total of 20 participants with >10% TBSA burns were recruited to the prospective study. Peak anti Factor Xa (AFXa) levels were measured for all 20 participants with 15% recording an initial prophylactic peak AFXa level within reference range. Upon subsequent measurements, 50% of participants reached a prophylactic peak AFXa level. Trough AFXa levels were measured for 17 participants with no participant recording an initial or subsequent trough AFXa level at or above the prophylactic threshold.

CONCLUSION

Our study demonstrates a high incidence of VTE among burns patients at the VABS, especially among the major burns patients, and a thromboprophylaxis protocol that is ineffective in achieving prophylactic levels of AFXa level. The evidence suggests a need to evaluate different dosing protocols among burns patients in order to improve AFXa levels, with the aim of decreasing incidence of VTE in high-risk patients.

Postoperative Venous Thromboembolism Prophylaxis Utilizing Enoxaparin Does Not Increase Bleeding Complications After Abdominal Body Contouring Surgery

BACKGROUND

Venous thromboembolism (VTE) chemoprophylaxis warrants an individualized, risk-stratified approach, and constitutes a relatively controversial topic in plastic surgery.

OBJECTIVES

The aim of this study was to determine the safety of a 7-day postoperative enoxaparin regimen for VTE prophylaxis compared with a single preoperative dose of heparin in abdominal body contouring surgery.

METHODS

This single-institution pre-post study investigated the safety of a 7-day enoxaparin postoperative regimen in abdominal body contouring procedures performed by a single surgeon from 2007 to 2018. Four procedures were included: traditional panniculectomy, abdominoplasty, fleur-de-lis panniculectomy, and body contouring liposuction. Group I patients received a single dose of 5000 U subcutaneous heparin in the preoperative period, and no postoperative chemical prophylaxis was administered. Group II patients received 40 mg subcutaneous enoxaparin in the immediate preoperative period, then once daily for 7 days postoperatively.

RESULTS

A total of 195 patients were included in the study, 66 in Group I and 129 in Group II. The groups demonstrated statistically similar VTE risk profiles, based on the 2005 Caprini risk-assessment model. There were no statistically significant differences in the 2 primary outcomes: postoperative bleeding and VTE events. Group I patients had higher reoperation rates (22.7% vs 10.1%, P = 0.029), which was secondary to higher rates of revision procedures.

CONCLUSIONS

A 7-day postoperative course of once-daily enoxaparin for VTE risk reduction in abdominal body contouring surgery does not significantly increase the risk of bleeding. Implementation of this regimen for postdischarge chemoprophylaxis, when indicated following individualized risk stratification, is appropriate.

LEVEL OF EVIDENCE: 4

Venous thromboembolism in plastic surgery: the current state of evidence in risk assessment and chemoprophylactic options

The application of venous thromboembolism (VTE) prophylaxis has been the topic of intense debate in plastic surgery. The overall incidence of VTE is low in plastic surgery patients as compared to other surgical subspecialties but may be higher in the inpatient rather than outpatient plastic surgery populations. The Caprini Risk Assessment Model is the most highly studied and validated tool to assess VTE risk in plastic surgery patients. However, the Caprini model lacks procedure-specific risk assessment and patient-specific risk factor calculations. Due to these limitations, such as the low incidence and the heterogeneous nature of the specialty, trials lacked the power to capture proof of benefit, except in the highest-risk inpatient population. The emerging use of aspirin and novel oral anticoagulants may provide an alternative, as noninferiority in terms of efficacy and safety has been demonstrated in other fields. In this review, the authors intend to summarize the current state of evidence for prevention and explore the modalities available for prophylaxis, including novel oral anticoagulants.

Local Pro- and Anti-Coagulation Therapy in the Plastic Surgical Patient: A Literature Review of the Evidence and Clinical Applications

The risks of systemic anti-coagulation or its reversal are well known but accepted as necessary under certain circumstances. However, particularly in the plastic surgical patient, systemic alteration to hemostasis is often unnecessary when local therapy could provide the needed adjustments. The aim of this review was to provide a summarized overview of the clinical applications of topical anti- and pro-coagulant therapy in plastic and reconstructive surgery. While not a robust field as of yet, local tranexamic acid (TXA) has shown promise in achieving hemostasis under various circumstances, hemostats are widely used to halt bleeding, and local anticoagulants such as heparin can improve flap survival. The main challenge to the advancement of local therapy is drug delivery. However, with increasingly promising innovations underway, the field will hopefully expand to the betterment of patient care.

Double-Blind Randomized Clinical Trial to Examine the Pharmacokinetic and Clinical Impacts of Fixed Dose versus Weight-based Enoxaparin Prophylaxis: A Methodologic Description of the FIxed or Variable Enoxaparin (FIVE) Trial

Venous thromboembolism is an important patient safety in plastic surgery, and multiple clinical trials in the past 10 years have provided increased understanding of the risks and benefits of venous thromboembolism prevention strategies. This paper provides an exhaustive discussion of the rationale behind and methodology for an in progress randomized double-blind clinical trial in plastic surgery inpatients, in which the 2 study arms are enoxaparin 40 mg twice daily and enoxaparin 0.5 mg/kg twice daily. The trial's primary aims are to: (1) demonstrate whether enoxaparin 0.5 mg/kg twice daily is superior to enoxaparin 40 mg twice daily for the pharmacokinetic endpoint of overanticoagulation (anti-Factor Xa > 0.4 IU/mL) and (2) demonstrate whether enoxaparin 0.5 mg/kg twice daily is not inferior to enoxaparin 40 mg twice daily for the pharmacokinetic endpoint of underanticoagulation (anti-Factor Xa < 0.2 IU/mL). The results of this trial will provide Level I evidence to help guide plastic surgeon's choice of postoperative prophylactic anticoagulation.

The Expanding Role of Diagnostic Ultrasound in Plastic Surgery

Supplemental Digital Content is available in the text.

Background:

Ultrasound in plastic surgery is quickly finding new applications. Ultrasound surveillance may replace ineffective individual risk stratification and chemoprophylaxis for deep venous thromboses. Abdominal penetration can be a catastrophic complication of liposuction. Preoperative screening for fascial defects may reduce risk. Limiting buttock fat injections to the subcutaneous plane is critical for patient safety, but it is difficult to know one’s injection plane.

Methods:

The author’s use of diagnostic ultrasound was evaluated from May 2017 to May 2018. Ultrasound scans were used routinely to detect deep venous thromboses. Patients undergoing abdominal liposuction and/or abdominoplasty were scanned for possible hernias. Other common applications included the evaluation of breast implants, breast masses, and seroma management. The device was used in surgery in 3 patients to assess the plane of buttock fat injection.

Results:

One thousand ultrasound scans were performed during the 1-year study period. A distal deep venous thrombosis was detected in 2 patients. In both cases, the thrombosis resolved within 1 month, confirmed by follow-up ultrasound scans. A lateral (tangential) fat injection method was shown to safely deposit fat above the gluteus maximus fascia.

Conclusions:

Ultrasound scans are highly accurate, noninvasive, and well-tolerated by patients. Some of these applications are likely to improve patient safety. Early detection of deep venous thromboses is possible. Unnecessary anticoagulation may be avoided. Subclinical abdominal defects may be detected. Ultrasound may be used in the office to evaluate breast implants, masses, and seromas. In surgery, this device confirms the level of buttock fat injection.

Analysis of sulfates on low molecular weight heparin using mass spectrometry: structural characterization of enoxaparin

INTRODUCTION

Structural characterization of low molecular weight heparin (LMWH) is critical to meet biosimilarity standards. In this context, the review focuses on structural analysis of labile sulfates attached to the side-groups of LMWH using mass spectrometry. A comprehensive review of this topic will help readers to identify key strategies for tackling the problem related to sulfate loss. At the same time, various mass spectrometry techniques are presented to facilitate compositional analysis of LMWH, mainly enoxaparin. Areas covered: This review summarizes findings on mass spectrometry application for LMWH, including modulation of sulfates, using enzymology and sample preparation approaches. Furthermore, popular open-source software packages for automated spectral data interpretation are also discussed. Successful use of LC/MS can decipher structural composition for LMWH and help evaluate their sameness or biosimilarity with the innovator molecule. Overall, the literature has been searched using PubMed by typing various search queries such as 'enoxaparin', 'mass spectrometry', 'low molecular weight heparin', 'structural characterization', etc. Expert commentary: This section highlights clinically relevant areas that need improvement to achieve satisfactory commercialization of LMWHs. It also primarily emphasizes the advancements in instrumentation related to mass spectrometry, and discusses building automated software for data interpretation and analysis.