Weight-adjusted tinzaparin for venous thromboembolism prophylaxis in bariatric surgery patients weighing 160 kg or more

Unresolved questions on venous thromboembolic disease. Venous thromboembolism (VTE) management in obese patients. Consensus statement of the French Society of Vascular Medicine (SFMV)

Obesity is an alarming worldwide public health issue and is defined as a body mass index (BMI) of 30kg/m2 or more. It is considered as a risk factor for first thrombotic event and is associated with a significant risk of recurrence. Consequently, obese patients are often treated by anticoagulant therapy but data from randomised control trial are scarce. We will review in this narrative review the state of the art of the prescription of anticoagulant for the prevention and treatment of venous thromboembolism (VTE) in obese patients.

A Three-year Retrospective Study Looking at Preventing Hospital Acquired Thrombosis

BACKGROUND

Hospital-acquired venous thromboembolism (HA-VTE) is defined as cases of venous thromboembolism (VTE) that occur in a hospital and within ninety days of a hospital admission. Deep vein thromboses (DVTs) most commonly occur within the deep veins of the pelvis and legs. If the thrombus dislodges and travels to the lungs, it can result in a pulmonary embolus (PE). VTE is associated with significant morbidity and mortality, accounting for almost 10% of all hospital deaths. If risk factors are correctly identified and VTE prophylaxis is prescribed, VTE can be a preventable condition. In 2010, NHS England launched The National Venous Thromboembolism Prevention Programme. This included NICE guidance, and a VTE risk assessment tool, which must be completed for at least 95% of patients on admission. The National Thrombosis Survey, published by Thrombosis UK, studied how this program was implemented locally, and audited HA-VTE prevention strategies nationally.

OBJECTIVES

Using the Thrombosis Survey and NICE guidance as an aide, this study collects data about hospital-acquired DVT (HA-DVT) at the Queen Elizabeth Hospital in Gateshead (QEH) and aims to: 1. Identify cases of HA-DVT and understand the clinical circumstances surrounding these cases 2. Assess the quality of VTE preventative measures at QEH 3. Outline potential improvement in reducing the incidence of HA-VTE at this hospital Methods: This retrospective cohort study used electronic records to identify all cases of DVT between April 2019 and April 2022 at QEH. Cases of HA-DVT were defined as: a positive ultrasound doppler report and either the case occurring in the 90 days following an inpatient stay, or beyond two days into an admission. For these cases of HA-DVT, we recorded the: reason for admission; admitting specialty; presence of an underlying active cancer and deaths occurring within 90 days of diagnosis. We assessed the quality of VTE preventative measures, by recording the: completion of VTE risk assessments; prescription of weight-adjusted pharmacological VTE prophylaxis and provision of VTE prophylaxis on discharge. For HA-DVT cases occurring within 90 days of an inpatient stay, the preventative measures were assessed on the original admission. Electronic records were used to record the completion rate of the National VTE risk assessment tool for all inpatients during this time frame.

RESULTS

The VTE risk assessment tool was completed for 98.5% of all admissions. One hundred and thirty-five cases of HA-DVT were identified between April 2019 and April 2022. Sixteen patients with HA-DVT did not have VTE prophylaxis prescribed on admission. Eleven of these patients had a clearly documented reason why anticoagulation was avoided. In HA-DVT cases where pharmacological VTE prophylaxis was prescribed, 23% were prescribed an inappropriate dose for their weight. If anticoagulation was required on discharge, this was prescribed appropriately in 94% of cases. About 31% of the patients with HA-DVT had an underlying active malignancy. Thirty-nine patients died within 90 days of the DVT being diagnosed; in only 1 case was VTE thought to be a contributing factor to death.

CONCLUSION

The hospital exceeded the national standard of VTE risk assessment completion on admission (greater than 95%). For almost a quarter of patients with HA-DVT, the dose of thromboprophylaxis prescribed was not appropriate for weight. In five cases of HA-DVT, thromboprophylaxis was omitted with no clear justification. HA-DVT often affects the most clinically vulnerable patients and is associated with a high mortality.

Increased bleeding risk with enoxaparin venothromboembolism prophylaxis compared with heparin in patients undergoing bariatric surgery

BACKGROUND

Perioperative venothromboembolism (VTE) chemoprophylaxis is an established tenant of bariatric surgery; however, there is little comparative data to guide medication choice. The objective of this study was to determine if a change in VTE prophylaxis from heparin to enoxaparin was associated with differing rates of postoperative bleeding and VTE occurrence after bariatric surgery.

METHODS

This retrospective cohort study included patients 18 years or older who underwent primary bariatric surgery (sleeve gastrectomy (SG) or Roux-en-Y gastric bypass (RYGB)) at a single institution between March 2012 and December 2021. Subcutaneous unfractionated heparin was utilized for VTE prophylaxis from March 2012 through February 2018 and then enoxaparin was used from March 2018 through December 2021. Postoperative bleeding was defined as requiring a blood transfusion or reoperation for bleeding within 30 days of surgery. Chi-square test was used to test for differences between groups.

RESULTS

There were 2159 patients who underwent bariatric surgery with 1324 (61.3%) patients in the heparin group and 835 (38.7%) in the enoxaparin group. Overall, 1,503 (69.6%) patients underwent SG and 656 (30.4%) RYGB. There was no difference in the ratio of SG to RYGB between the heparin and enoxaparin groups. Most patients were female (n = 1709, 79.2%) with a median age of 43.2 years (interquartile range (IQR): 35.6-52.2), and median BMI of 44.9 (IQR: 40.9-50.5). Overall postoperative bleeding occurred more frequently in the enoxaparin group (n = 26, 3.1%) compared with the heparin group (n = 12, 0.9%) (p < 0.01). Additionally, reoperation for bleeding was more frequent with enoxaparin (enoxaparin 0.8% vs. heparin 0.2%, p = 0.04). There was no difference in VTE occurrence between the two groups (heparin: n = 14, 1.1%, enoxaparin: n = 7, 0.8% (p = 0.61)).

CONCLUSIONS

An institutional change from heparin to enoxaparin for bariatric surgery perioperative VTE prophylaxis was associated with a significant increase in postoperative bleeding, with no difference in VTE complications.

Weight-adjusted dosing of tinzaparin for thromboprophylaxis in obese medical patients

Background

The optimal dose of tinzaparin for prophylaxis in obese medical patients is not well defined.

Objectives

To evaluate the anti-Xa activity in obese medical patients on tinzaparin prophylaxis adjusted for actual bodyweight.

Methods

Patients with a body mass index of ≥30 kg/m² treated with 50 IU/kg tinzaparin once daily were prospectively included. Anti-Xa and anti-IIa activity; von Willebrand factor antigen and von Willebrand activity; factor VIII activity; D-dimer, prothrombin fragments; and thrombin generation were measured 4 hours after subcutaneous injection between days 1 and 14 after the initiation of tinzaparin prophylaxis.

Results

We included 121 plasma samples from 66 patients (48.5% women), with a median weight of 125 kg (range, 82-300 kg) and a median body mass index of 41.9 kg/m² (range, 30.1-88.6 kg/m²). The target anti-Xa activity of 0.2 to 0.4 IU/mL was achieved in 80 plasma samples (66.1%); 39 samples (32.2%) were below and 2 samples (1.7%) above the target range. The median anti-Xa activity was 0.25 IU/mL (IQR, 0.19-0.31 IU/mL), 0.23 IU/mL (IQR, 0.17-0.28 IU/mL), and 0.21 IU/mL (IQR, 0.17-0.25 IU/mL) on days 1 to 3, days 4 to 6, and days 7 to 14, respectively. The anti-Xa activity did not differ among the weight groups (P = .19). Injection into the upper arm compared to the abdomen resulted in a lower endogenous thrombin potential, a lower peak thrombin, and a trend to a higher anti-Xa activity.

Conclusion

Dosing of tinzaparin adjusted for actual bodyweight in obese patients achieved anti-Xa activity in the target range for most patients, without accumulation or overdosing. In addition, there is a significant difference in thrombin generation depending on the injection site.

Strategies for sustained release of heparin: A review

Heparin, a sulfate-containing linear polysaccharide, has proven preclinical and clinical efficacy for a variety of disorders. Heparin, including unfractionated heparin (UFH), low-molecular-weight heparin (LMWH), and ultra-low-molecular-weight heparin (ULMWH), is administered systematically, in the form of a solution in the clinic. However, it is eliminated quickly, due to its short half-life, especially in the case of UFH and LMWH. Frequent administration is required to ensure its therapeutic efficacy, leading to poor patient compliance. Moreover, heparin is used to coat blood-contacting medical devices to avoid thrombosis through physical interaction. However, the short-term durability of heparin on the surface of the stent limits its further application. Various advanced sustained-release strategies have been used to prolong its half-life in vivo as preparation technologies have improved. Herein, we briefly introduce the pharmacological activity and mechanisms of action of heparin. In addition, the strategies for sustained release of heparin are comprehensively summarized.

Direct oral anticoagulants after bariatric surgery-What is the evidence?

BACKGROUND

Obesity is a global epidemic and bariatric surgery is used with increasing frequency to treat its complications. The extent to which bariatric surgery alters the efficacy, safety, and pharmacokinetics of direct oral anticoagulants (DOACs) is unknown.

AIMS

In this review, we summarize the evidence supporting the use of DOACs after bariatric surgery and apply our findings to resolve several clinical cases.

MATERIALS & METHODS

We systematically searched MEDLINE, EMBASE, Cochrane Library, CINAHL and ClinicalTrials.gov from January 1, 2000, to June 15, 2021 for randomized and non-randomized studies evaluating the use of DOACs for any indication after bariatric surgery. Two reviewers independently screened titles, abstracts, and full-text articles. Clinical and pharmacokinetic outcomes were pooled by random-effects meta-analysis with inverse variance weighting. We used the Newcastle-Ottawa scale to assess risk of bias in non-randomized studies and assessed the certainty of evidence with GRADE.

RESULTS

From 2519 records, we included 28 studies (n = 3229 patients): no randomized trials, 7 cohort studies, 6 case series, and 15 case reports. Incidence rates for arterial thromboembolism, venous thromboembolism and major bleeding were: 0.73 (95% confidence interval [CI]: 0.01-5.10), 2.45 (95% CI: 0.40-7.94), and 3.40 (95% CI: 0.80-9.36) events per 100 patient-years, respectively. The pooled proportion of peak direct oral anticoagulant drug levels within the expected range was 58% (95% CI: 39%-74%).

CONCLUSION

There appears be substantial risk of DOAC malabsorption after bariatric surgery that could affect clinical outcomes, however the certainty of evidence was very low.

PROSPERO

CRD42020202636.