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Tran et al	
a past history of VTE for prescriber to consider using
extended thromboprophylaxis with LMWH and acknowledged obese patients had increased risk of VTE.13 These
guidelines also do not make reference to the prophylactic
dose of enoxaparin in obesity.
Obese individuals have an increased percentage of fat per
kilogram of total bodyweight and blood flow in adipose tissue is lower than lean body mass.8 In thromboprophylaxis
studies, including those investigating fixed-dose enoxaparin,
morbidly obese patients (BMI ≥35 kg/m2) are underrepresented, creating several challenges.14 Federal Drug
Administration-approved doses for thromboprophylaxis (eg,
enoxaparin 40 mg once daily or dalteparin 5000 International
Units once daily) are fixed doses that do not take into account
actual body weight and, as the drug distribution of LMWHs
is weight dependent, anticoagulant levels may differ in obese
patients when fixed-doses are prescribed.15
In morbidly obese, medically ill patients, the use of
weight-based enoxaparin dosed at 0.5 mg/kg once daily is
feasible and results in peak anti-Xa levels within or near recommended range for thromboprophylaxis, without any evidence of excessive anti-Xa activity.16 These results suggest
that actual weight-based regimen may be more effective than
standard fixed-dose enoxaparin.9 Patients at extremes of
weight require special consideration to determine appropriate enoxaparin doses.17 Optimal enoxaparin dosing strategies
for VTE prophylaxis and treatment for patients at extremes
of weight have not yet been elucidated by clinical trials;
however, data suggest that standard dosing regimens may not
be appropriate in these patients.18 In patients with BMIs
≥40 kg/m2, 40 mg subcutaneously twice daily is recommended, with consideration for higher doses in patients with
BMIs ≥50 kg/m2.15
Low-molecular-weight heparins are the preferred agents
for prophylaxis as they reduce VTE more effectively than
mechanical prophylaxis.1 They should always be the preferred choice, but, however, are associated with bleeding
risk.19 Bleeding risk can be categorized into absolute bleeding risk (active hemorrhage, thrombolytics used within the
past 24 hours) or relative bleeding risk (international normalized ratio [INR] ≥2.0, severe trauma to spinal cord, multiple
traumas).20 Patients with both an absolute or relative bleeding risk should be reevaluated daily for changes in bleeding
risk status. This status may influence a prescriber assessment
to increasing prophylaxis doses in obese patients.

excluded relevant articles published before 1998 from inclusion and critical analysis. One such relevant publication in
1995 concluded a fixed dose of enoxaparin 40 mg subcutaneously daily was appropriate for orthopedic patients with a
body weight less than 100 kg. They conceded that there were
no recommendations for patients heavier than 100 kg and
concluded the need for additional studies on obese patients
with BMI >32 kg/m2.21 Limited additional studies branching
from this conclusion were discovered as part of this search.
We also concede this search did not separate major traumatic orthopedic-related surgeries from minor elective
orthopedic-related surgeries in obese patients. We recognized high-risk procedures (pelvic and multiple fractures)
are more likely to develop VTE when compared with lower
risk procedures (arthroscopic procedures); thus, individual
surgeon's clinical assessment is paramount for all patients.

Conclusion
The results of a multiple database search draw one to the
conclusion that there is very limited evidence in the literature
with regard to prophylactic enoxaparin dosing in obese
orthopedic-specific patients.
Orthopedic patients are among the highest of all surgical
specialties at risk of VTE. There is strong evidence to support an increased prophylactic LMWH doses in obese
patients; thus, the authors recommend higher dose prophylactic enoxaparin in obese orthopedic patients.
Acknowledgments
The authors acknowledge Associate Professor Andrew Bucknill,
head of orthopaedics, and the pharmacy practice research committee at the Royal Melbourne Hospital, for their contribution in
reviewing this report.

Declaration of Conflicting Interests
The author(s) declared no potential conflicts of interest with respect
to the research, authorship, and/or publication of this article.

Funding
The author(s) received no financial support for the research, authorship, and/or publication of this article.

ORCID iD
Van N. Tran

Limitations of Literature Review
The search of English-only literature excluded the review of
possible studies published in other languages from critical
analysis. Unfortunately, this restriction may create a bias,
which previous similar reviews may not have as a result of
broadening their search to include all articles.
The inclusion criteria were restricted to articles published
within the last 20 years. We recognized this restriction

https://orcid.org/0000-0001-8864-2187

References
	1.	 Falck-Ytter Y, Francis CW, Johanson NA, et al. Prevention
of VTE in orthopedic surgery patients: antithrombotic therapy
and prevention of thrombosis, 9th ed: American College of
Chest Physicians evidence-based clinical practice guidelines.
Chest. 2012;141(2 suppl):e278S-e325S.
	 2.	 Treasure T, Chong LY, Sharpin C, Wonderling D, Head K,
Hill J. Developing guidelines for venous thromboembolism
https://www.orcid.org/0000-0001-8864-2187
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