Prevention of thromboembolism with low-molecular-weight heparin in orthopedic surgery: a 5-year experience

Incidence and risk factors of preoperative deep venous thrombosis in closed tibial shaft fracture: a prospective cohort study

OBJECTIVE

To investigate the preoperative morbidity of deep venous thrombosis (DVT) and predictive risk factors associated with DVT after closed tibial shaft fracture.

METHODS

Ultrasonography and blood analyses were performed preoperatively in patients who sustained tibial shaft fracture between October 2014 and December 2018. Univariate analyses were used in the data of demographics, comorbidities, mechanism of injury, concomitant fractures and laboratory biomarkers. Multivariate logistic regression analyses were conducted to determine the independent risk factors associated with DVT.

RESULTS

In total, 918 patients with an operatively treated tibial shaft fracture were included, among whom 122 patients had preoperative DVTs, indicating a crude morbidity of 13.3%. Ninety-two of 758 (12.1%) patients with isolated tibial shaft fracture developed DVT, while 30 of 160 (18.8%) patients with concurrent fracture presented with DVT. The average interval between fracture and initial diagnosis of DVT was 3.1 days (median, 2 days), ranging from 0 to 33 days. Among DVT-positive patients, 16 (13.1%) patients presented with proximal DVT and 106 (86.9%) patients had distal DVT. Multivariate logistic regression analysis showed four independent risk factors were significantly correlated to the development of DVT, including increased age (OR = 1.17, p = 0.003), diabetes (OR = 1.99, p = 0.009), serum hydroxybutyrate dehydrogenase > 182 U/L (OR = 1.83, p = 0.008), and delay to DUS (in each day) (OR = 1.13, p < 0.001).

CONCLUSION

In the present cohort study, the incidence of DVT was 12.1% in patients with isolated tibial shaft fracture. We suggest individualized risk stratification and early anticoagulation for patients with high risk factors including pre-existing diabetes, HBDH > 182 U/L, delay to DUS and older age.

LEVEL OF EVIDENCE

Level III, a prospective cohort study.

Duplex ultrasound for evaluation of deep venous blood flow in fractured lower extremities

Purpose

Early identification of deep venous thrombosis (DVT) in trauma patients would result in an early initiation of treatment, thereby decreasing the frequency of complications. The aim of the current study was to evaluate the role of duplex ultrasound (DUS) in the evaluation of deep venous blood flow in fractured lower extremities to rule out DVT prior to orthopedic surgery.

Material and methods

In this prospective study a total of 58 patients (42 males and 16 females; mean age of 51.5 ± 19.5 years) with fractured lower extremities were thoroughly evaluated prior to surgery with respect to medical history, fracture pattern, associated injuries, comorbid conditions, and venous duplex ultrasound (VDUS) findings. Each affected limb was assessed for the presence of DVT using a Sonoline G 60S ultrasound unit. The analysis was performed with the Statistical Package for the Social Sciences (SPSS) version 20.

Results

DVT was found in 36 (62.1%) patients with single closed fractures, 9 (15.5%) patients with single opened fractures, 10 (17.2%) patients with multiple closed fractures, and in 3 (5.2%) patients with multiple opened fractures. Sensitivity and specificity of the findings of compressibility and phasicity for DVT detection in patients with fractured lower extremities were 81.25% and 87.50% and 100% and 100% respectively. In addition, the absence of compressibility and phasicity had positive predictive value of 100% and 100% and negative predictive value of 93.75% and 95.65% respectively.

Conclusions

US of DVs in the brightness mode (B-mode) with compression maneuvers should be the first-line imaging modality for suspected DVT in patients with fractured lower extremities.

Symptomatic venous thromboembolism following circular frame treatment for tibial fractures

INTRODUCTION

Venous thromboembolism (VTE) is a significant cause of morbidity and mortality following tibial fractures. The risk is as high as 77% without prophylaxis and around 10% with prophylaxis. Within the current literature there are no figures reported specifically for those individuals treated with circular frames. Our aim was to evaluate the VTE incidence within a single surgeon series and to evaluate potential risk factors.

METHODS

We retrospectively reviewed our consecutive single surgeon series of 177 patients admitted to a major trauma unit with tibial fractures. All patients received standardised care, including chemical thromboprophylaxis within 24h of injury until independent mobility was achieved. We comprehensively reviewed our prospective database and medical records looking at demographics and potential risk factors.

RESULTS

Seven patients (4.0% ± 2.87%) developed symptomatic VTE during the course of frame treatment; three deep vein thrombosis (DVTs) and four pulmonary embolisms (PEs). Those with a VTE event had significantly increased body mass index (BMI) (p = 0.01) when compared to those without symptomatic VTE. No differences (p > 0.05) were observed between the groups in age, gender, smoking status, fracture type (anatomical allocation or open/closed), delay to frame treatment, weight bearing status post-frame, inpatient stay or total duration of frame treatment.

CONCLUSION

This study suggests that increased BMI is a statistically significant risk factor for VTE, as reported in current literature. In addition, we calculated the true risk of VTE following circular frame treatment for tibial fracture in our series is from 1.13% to 6.87%, which is at least comparable to other forms of treatment.

Symptomatic venous thromboembolism and mortality in orthopaedic surgery - an observational study of 45 968 consecutive procedures

Background

Little information exists on the presentation of symptomatic venous thromboembolism (VTE) in orthopaedic surgery when a defined protocol for thromboprophylaxis is used. The objective with this study was to establish the VTE rate and mortality rate in orthopaedic surgery.

Methods

We performed a prospective, single centre observational cohort study of 45 968 consecutive procedures in 36 388 patients over a 10 year period. Follow-up was successful in 99.3%. The primary study outcome was the incidence of symptomatic deep vein thrombosis (DVT), symptomatic pulmonary embolism (PE) and mortality at 6 weeks, specified for different surgical procedures. The secondary outcome was to describe the DVT distribution in proximal and distal veins and the proportion of VTEs diagnosed after hospital discharge. For validation purposes, a retrospective review of VTEs diagnosed 7–12 weeks postoperatively was also performed.

Results

In total, 514 VTEs were diagnosed (1.1%; 95% CI: 1.10-1.14), the majority (84%) after hospital discharge (432 out of 514).With thromboprophylaxis, high incidence of VTE was found after internal fixation (IF) of pelvic fracture (12%; 95% CI: 5–26), knee replacement surgery (3.7%; 95% CI: 2.8-5.0), after internal fixation (IF) of proximal tibia fracture (3.8%; 95% CI: 2.3-6.3) and after IF of ankle fracture (3.6%; 95% CI: 2.9-4.4). Without thromboprophylaxis, high incidence of VTE was found after Achilles tendon repair (7.2%; 95% CI: 5.5-9.4). In total 1094 patients deceased (2.4%; 95% confidence interval (CI): 2.33- 2.44) within 6 weeks of surgery. Highest mortality was seen after lower limb amputation (16.3%, CI: 13.8-19.1) and after hip hemiarthroplasty due to hip fracture (9.6%, CI; 7.6-12.1).

Conclusion

The overall incidence of VTE is low after orthopaedic surgery but our study highlights surgical procedures after which the risk for VTE remains high and improved thromboprophylaxis is needed.

Deep venous thrombosis following different isolated lower extremity fractures: what is known about prevalences, locations, risk factors and prophylaxis?

INTRODUCTION

Deep venous thrombosis (DVT) offers a high risk of morbidity and mortality, especially in case of pulmonary embolism. Precise data as to DVT after isolated lower extremity fractures (ILEFs) are rare. Even organizations like the American Academy of Orthopaedic Surgeons or the American College of Chest Physicians do not state exact recommendations as to optimal DVT prophylaxis (ppx) after ILEFs.

PREVALENCE

The incidence of DVT ranges from 5 to 86 % depending on the fracture whereas femur fractures offer the highest risk for clotting. The incidence seems to decrease in more distal fractures.

LOCATION

The risk to develop proximal clots is likely low, however, especially these are feared by surgeons. DVT can occur in both the injured and uninjured leg with a trend for higher incidences in the injured leg.

RISK FACTORS

Risk factors for DVT after ILEF seem to be similar to risk factors for DVT development after orthopaedic surgery and in general. Risk factors caused by surgeons are the use of a tourniquet, prolonged operative time and a delay from injury to surgery.

PROPHYLAXIS

Low molecular weight heparin is favoured by many authors, however, warfarin and acetylsalicylic acid are also used. Clear recommendations are still missing.

CONCLUSION

The rate of morbidity caused by DVT after ILEF is poorly understood so far. Exact data on prevalences are missing and optimal DVT prophylaxis still has to be defined.

Utility of once-daily dose of low-molecular-weight heparin to prevent venous thromboembolism in multisystem trauma patients

INTRODUCTION

Venous thromboembolism is a preventable cause of death in the severely injured patient. Low-molecular-weight heparins (LMWHs) have been recommended as effective, safe prophylactic agents. However, LMWH use remains controversial in patients at risk for bleeding, those with traumatic brain injury, and those undergoing multiple invasive or operative procedures. We hypothesized that a protocol utilizing once-daily LMWH prophylaxis in high-risk trauma patients, regardless of the need for invasive procedures, is feasible, safe, and effective.

METHODS

From August 1998 to August 2000, all patients admitted to our American College of Surgeons-verified Level I trauma facility following injury were evaluated for deep venous thrombosis (DVT) risk and prospectively followed. Patients at high risk for DVT, including those with stable intracranial injuries, were placed on our institutional protocol and prospectively followed. Patients on the protocol received daily injections of the LMWH, dalteparin; DVT screening was performed with duplex ultrasonography within 48 hours of admission and after 7 to 10 days after injury. Regimen compliance, bleeding complications, DVT rates, and pulmonary embolus (PE) rates were analyzed.

RESULTS

During the 2-year study period, 6247 trauma patients were admitted; 743 were considered at high risk for DVT. Most of the patients were men (72%), with a mean age of 38.7 years (range 15-89 years) and a mean injury severity score (ISS) of 19.5. Compliance with the daily regimen was maintained in 74% of patients. DVT was detected in 3.9% and PE in 0.8%. The wound complications rate was 2.7%, and the need for unexplained transfusions was 3%. There were no exacerbations of head injury following dalteparin initiation due to bleeding. There were 16 patient deaths; none was caused by PE or late hemorrhage.

CONCLUSIONS

Once-daily dosing of prophylactic LMWH dalteparin is feasible, safe, and effective in high-risk trauma patients. Our protocol allows one to "operate through" systemic prophylaxis and ensures timely prophylaxis for brain-injured and multisystem trauma patients.

Unfractionated heparin compared with low-molecular-weight heparin as related to heparin-induced thrombocytopenia

PURPOSE OF REVIEW

Heparin-induced thrombocytopenia is a severe side effect of treatment with unfractionated heparin. The relation of low-molecular-weight heparin to heparin-induced thrombocytopenia is less well understood. This review will summarize what is known about the similarities and differences between thrombocytopenia induced by low-molecular-weight heparin and that induced by unfractionated heparin.

RECENT FINDINGS

The pathophysiology of unfractionated heparin-induced thrombocytopenia, caused by the development of antibodies to heparin/platelet factor 4 complexes, holds true for low-molecular-weight heparin because the molecules of the latter are of the same saccharidic structure as those of unfractionated heparin. Owing to their smaller size, however, low-molecular-weight heparin does not interact with platelet factor 4 and platelets as efficiently as does unfractionated heparin. This translates to a two- to threefold lower risk of immune sensitization (antibody generation and occurrence of clinical heparin-induced thrombocytopenia). Low-molecular-weight heparin-induced thrombocytopenia antibodies are more often immunoglobulin A and immunoglobulin M, in contrast to the immunoglobulin G antibodies generated with unfractionated heparin-induced thrombocytopenia, which tend to be more often associated with clinical heparin-induced thrombocytopenia. The clinical expression of low-molecular-weight heparin-induced thrombocytopenia is generally similar to that of unfractionated heparin-induced thrombocytopenia but can have a slower onset, more severe thrombocytopenia, and slower platelet count recovery. Given that low-molecular-weight heparin, of itself, is linked with heparin-induced thrombocytopenia pathophysiology and it can interact with most preexisting heparin-induced thrombocytopenia antibodies generated after exposure to unfractionated heparin, treatment of heparin-induced thrombocytopenia patients with low-molecular-weight heparin is contraindicated.

SUMMARY

The risk of the development of heparin-induced thrombocytopenia with low-molecular-weight heparin treatment is reduced relative to the frequency of unfractionated heparin-induced thrombocytopenia, but it is not eliminated, and platelet counts should be monitored with treatment.