Practice patterns in high-risk bariatric venous thromboembolismprophylaxis

Howard I. Pryor II • Adam Singleton •

Elissa Lin • Paul Lin • Khashayar Vaziri

Received: 11 April 2012 / Accepted: 30 July 2012 / Published online: 6 October 2012

� Springer Science+Business Media, LLC 2012

Abstract

Background In the morbidly obese population that

undergoes bariatric surgery, venous thromboembolism

(VTE) is the leading cause of morbidity and mortality.

Certain factors place a patient at higher risk for VTE. No

consensus exists on VTE screening or prophylaxis for the

high-risk patient. This report describes the results of a

survey on VTE screening and prophylaxis patterns in high-

risk bariatric surgery.

Methods Members of the Society of American Gastro-

intestinal and Endoscopic Surgeons (SAGES) were queried

on factors that identified bariatric patients as high risk for

VTE and on routine screening and prophylaxis practices.

This included mechanical and chemical prophylaxis,

duration of therapy, and use of inferior vena cava (IVC)

filters.

Results Of the 385 surgeons who responded to the survey,

81 % were bariatric surgeons, and the majority managed

more than 50 cases annually. One or more of the following

risk factors qualified patients as high risk: history of VTE,

hypercoagulable status, body mass index (BMI) exceeding

55 kg/m2, partial pressure of arterial oxygen (PaO2) lower

than 60 mmHg, and severe immobility. Preoperative

screening of patients for VTE was practiced routinely by

56 % of the surgeons, and 92.4 % used preoperative che-

moprophylaxis. The most common agent used preopera-

tively was heparin (48 %), and Lovenox was most

commonly used postoperatively (49 %). Whereas 48 % of

the patients discontinued chemoprophylaxis at discharge,

43 % continued chemoprophylaxis as outpatients, and

47 % routinely screened for VTE postoperatively. Use of

IVC filters was routine for 28 % of the patients, who most

commonly removed them after 1–3 months.

Conclusions This study describes current practice pat-

terns of VTE screening and prophylaxis in high-risk bari-

atric surgery. Nearly all surgeons agree on risk factors that

qualify patients as high risk, but only half routinely screen

patients preoperatively. Preoperative VTE chemoprophy-

laxis is used by nearly all surgeons, but the duration of

therapy varies. Use of IVC filters is not routine, and

postoperative screening was performed by less than half of

the respondents. An understanding of current practice

patterns yields insight into the rates of VTE and shows

variability in the need for evidence-based prophylaxis and

standardized screening.

Keywords Bariatric � Obesity � Pulmonary � Vascular

Approximately 32.2 % of adult men and 35.5 % of adult

women are considered obese, and in 2009, almost 220,000

bariatric surgeries were performed in the United States

[1, 2]. In the morbidly obese population that undergoes

either open or laparoscopic bariatric surgery, venous

thromboembolism (VTE) is the leading cause of morbidity

and mortality. Deep vein thrombosis (DVT) and pulmonary

embolism (PE) are major complications of bariatric sur-

gery, with nearly 50 % of all deaths due to PE [3]. The

increasing number of obese individuals coupled with the

increased number of bariatric surgeries performed each

year makes VTE an ever more important pathology.

The risk of VTE is faced by all patients who undergo

bariatric surgery. However, several other factors place a

patient at an even higher risk for the development of DVT/

H. I. Pryor II � A. Singleton � E. Lin � P. Lin � K. Vaziri (&)

Department of Surgery, The George Washington University,

2150 Pennsylvania Avenue, NW, Suite 6B, Washington,

DC 20037, USA

e-mail: kvaziri@mfa.gwu.edu

123

Surg Endosc (2013) 27:843–848

DOI 10.1007/s00464-012-2521-z

and Other Interventional Techniques

PE. The role of obesity as an independent risk factor for

VTE is debated. Recent studies indicate that obesity places

patients at a higher risk for VTE [4–7], and in addition to

obese status, numerous other risk factors have been iden-

tified including a history of DVT/PE, a known history of a

hypercoagulable disorder, severe immobility, estrogen

medication, and advanced age [5, 8, 9]. This suggests that

all bariatric surgery patients are at increased risk.

A study that surveyed members of the American Society

for Bariatric Surgery in 2000 demonstrated that 86 % of

the patients who had surgery performed by bariatric sur-

geons were considered to be at high risk for VTE [10].

However, the specific factors that place an obese patient in

the high-risk category were not elucidated, and since then,

no consensus has been formulated.

Due to the silent nature of VTE and the difficulty

establishing a diagnosis of DVT/PE before the onset of

symptoms, prophylaxis against VTE is paramount. A

variety of treatment regimens for prophylaxis of VTE have

been proposed. The majority of studies describe some form

of pharmaceutic treatment coupled with the use of

mechanical compression devices or mechanical compres-

sion devices alone [10–14]. However, no universally

established protocol exists specifically for the high-risk

bariatric patient.

We report the results of a survey encompassing mem-

bers of the Society of American Gastrointestinal Endo-

scopic Surgeons (SAGES) who perform bariatric surgery.

The respondents were asked to identify factors that put

bariatric patients at high risk for VTE. The respondents

also were asked to report the prophylactic treatment regi-

mens they used to prevent DVT/PE in the high-risk bari-

atric patient group.

Materials and methods

Members of SAGES were contacted and asked to complete

an online survey. The survey consisted of 26 questions

regarding their current practices. The surgeons were asked

to identify whether they performed bariatric surgery, their

approach, and the total number of cases they managed

annually. They were further queried on the preoperative

risk factors they thought identified patients at high risk for

VTE. Routine preoperative screening methods and pro-

phylaxis patterns among high-risk patients were queried,

including mechanical and pharmacologic prophylaxis.

Members were asked to identify the chemoprophylactic

agent together with initiation and duration of treatment.

Their use of inferior vena cava (IVC) filters and postop-

erative screening also was queried. The results are descri-

bed as percentages of completed surveys.

Results

Of the 385 surgeons who responded to the survey, 313

(81 %) reported themselves to be bariatric surgeons. The

majority of the respondents were from the United States

(75.8 %). They were stratified into three groups based on

the number of bariatric cases they managed annually: fewer

than 50 cases (25.6 %), 51–100 cases (31.6 %), or more

than 100 cases (42.8 %). Most of those surveyed (98.7 %)

routinely performed bariatric procedures laparoscopically.

The respondents were asked about their practice patterns

with regard to preoperative, operative, and postoperative

VTE prophylaxis for high-risk patients.

Preoperative risk factors

The respondents identified the following individual factors

as qualifying their patients to be considered at high risk for

VTE: history of DVT/PE (99.7 %), known hypercoagula-

ble status (99.7 %), severe immobility (98.6 %), body mass

index (BMI) exceeding 55 kg/m2 (88.6 %), and partial

pressure of arterial oxygen (PaO2) lower than 60 mmHg

(65.9 %). A history of DVT/PE was identified by 69.9 % of

respondents as the most significant single factor, followed

by known hypercoagulable status (17.8 %), severe immo-

bility (9.6 %), BMI exceeding 55 kg/m2 (1.4 %), and PaO2

lower than 60 mmHg (1.4 %) (Fig. 1). Nearly half of those

surveyed (47.7 %) considered that three or more of these

Fig. 1 The most important

single factor for determining

VTE risk for bariatric patients

844 Surg Endosc (2013) 27:843–848

123

factors placed a patient at high risk for VTE compared with

7 % who considered high risk to be indicated by two fac-

tors. For 44.4 %, only one factor was necessary to identify

a patient at high risk, whereas 1 % thought none of these

factors placed a patient at high risk for VTE.

More than half of the surgeons (56 %) routinely

screened high-risk patients preoperatively for DVT:

33.1 % by clinical exam alone and 20.9 % with routine

ultrasound. As reported, 46 % did not routinely screen

high-risk bariatric patients for DVT. Only 23.2 % of the

respondents routinely screened patients for previously

unidentified hypercoagulable status.

Routine preoperative VTE chemoprophylaxis was

applied by 92.4 % of the respondents (Fig. 2), with 48 %

using unfractionated heparin, 33.4 % using Lovenox,

2.6 % using Fondaparinux, and 8.3 % using another anti-

coagulant. As reported, 28.1 % of the surgeons routinely

used retrievable IVC filters preoperatively for high-risk

bariatric patients, 0.3 % routinely used permanent filters,

and 71.5 % did not routinely use IVC filters for high-risk

patients.

Operative and postoperative prophylaxis

Intraoperatively, 96.3 % of respondents placed sequential

compression devices (SCD) on high-risk patients. As

reported, 15 % used additional intraoperative chemical

prophylaxis beyond the preoperative dose, with 7.3 %

using additional heparin, 4.3 % using Lovenox, 0.7 %

using Fondaparinux, and 2.7 % using other agents.

Postoperatively, 91.6 % of the surgeons used SCDs on

their high-risk patients, with 97 % also using chemical

prophylaxis. The most commonly used postoperative che-

moprophylactic agent was Lovenox (49.5 %), followed by

heparin (33 %), other agents (9.1 %), and Fondaparinux

(5.4 %).

Postoperative chemoprophylaxis was started most

commonly on postoperative day 0 (70 %), followed by

postoperative day 1 (27.3 %). Chemical prophylaxis was

discontinued at discharge in most cases (48.5 %). How-

ever, 43.8 % of the surgeons continued postoperative

chemoprophylaxis for outpatients. The most common

chemoprophylactic agent used for outpatients was Lovenox

(39.7 %). The most common durations of outpatient ther-

apy were 2 to 4 weeks (40.1 %) and fewer than 2 weeks

(20.2 %).

Routine use of IVC filters for high-risk bariatric patients

was reported by 28.1 % of the respondents, and 51.2 % of

the surgeons routinely discharged patients using IVC filters

coupled with chemoprophylaxis. The most common agent

used was Lovenox (36.4 %), followed by other agents

(8.8 %), heparin (3.7 %), and Fondaparinux (2.4 %). The

most common duration of therapy was 2–4 weeks, fol-

lowed by fewer than 2 weeks. The IVC filters were most

commonly removed 30–90 days postoperatively (55.2 %).

The remaining filters were removed after 90 days (23.2 %)

or within 30 days (21.5 %).

Discussion

A significant percentage of morbidly obese bariatric

patients are described as high risk by surgeons, but no

consensus exists regarding which risk factors or what

number of risk factors are required by physicians to iden-

tify a patient as high risk. Our study sought to identify

these factors and also to describe current practice patterns

regarding screening and the use of chemoprophylaxis and

IVC filters.

Among the risk factors identified for considering patients at

high risk (BMI [ 55 kg/m2, history of DVT/PE, hypercoag-

ulable status, severe immobility, and PaO2 \ 60 mmHg), the

majority of respondents considered a history of DVT/PE as the

Fig. 2 Routine chemical prophylaxis for high-risk bariatric patients

Surg Endosc (2013) 27:843–848 845

123

most important single risk factor. Whereas 44 % of surgeons

needed only one of these risk factors to identify a patient at

high risk, 47 % required a combination of three or more

factors.

Previous VTE has been established as an independent

risk factor for future VTE [15], and research has shown that

among patients with previous VTE events, recurrent DVT/

PE occurred for 33 % of patients who underwent bariatric

surgery [16]. The same study demonstrated that among

patients with no history of VTE, the incidence of sub-

sequent DVT/PE was zero.

Our study found that 69.9 % of the respondents identi-

fied a history of DVT/PE as the most important risk factor

for VTE, but only 54 % routinely screened high-risk

patients preoperatively for DVT. As reported, 33.1 % of

the surgeons used clinical exam alone, and 20.9 % used

ultrasound. Overall, the majority of surgeons used a history

of DVT/PE as an important marker to identify high-risk

patients, but only 20 % screened patients with preoperative

ultrasound.

The inconsistency between evaluation of risk and pre-

operative screening also was seen in patients with possible

hypercoagulable status. Although 99.7 % of the surgeons

considered a patient with known hypercoagulable status at

high risk for VTE, only 23.2 % evaluated for a previously

unrecognized hypercoagulable status.

Research has shown that up to 70 % of patients pre-

senting with VTE have a demonstrable inherited or

acquired thrombophilia. These include protein C and pro-

tein S deficiency, antithrombin deficiency, factor V-Leiden

mutation, elevated factor VIII, antiphospholipid syndrome,

and hyperhomocysteinemia [17]. Further research has

shown that patients wishing to undergo bariatric surgery

have high rates of both acquired and inherited thrombo-

philias [18].

Although no currently existing data links bariatric sur-

gery patients with known thrombophilias to higher rates of

DVT/PE, inference from previous research suggests that

this could be the case. Surgeons should strongly consider

preoperative assessment for the high-risk patient with

inherited or acquired hypercoagulable status.

Severely obese patients, especially those with BMIs

exceeding 55 kg/m2, tend to experience respiratory insuf-

ficiency, which consists of obesity hypoventilation syn-

drome (arterial PaO2 \ 60 mmHg or arterial partial

pressure of carbon dioxide [PaCO2] [ 47), obstructive

sleep apnea, or both [19].

Obesity hypoventilation syndrome was considered by

65.9 % of our respondents as a factor placing a bariatric

patient in the high-risk category. Patients with respiratory

insufficiency who undergo bariatric surgery have a mor-

tality rate seven times higher than patients without respi-

ratory insufficiency before surgery [20]. This further

establishes low PaO2 as a significant preoperative risk

factor.

The stratification of morbidly obese patients into a high-

risk category should prompt a more aggressive VTE pro-

phylaxis regimen. However, no prophylactic regimen is

uniformly accepted, and no evidence-based approach has

been defined. Although the overall incidence of VTE from

bariatric surgery is 1–3 % and considered low, the presence

of VTE among patients undergoing surgery likely is

underreported [21]. Clinically evident PE may occur

without prodromal signs or symptoms of DVT, so the

opportunity for medical intervention may have already

passed. Additionally, the increasing number of bariatric

procedures performed each year likely will further increase

the number of VTE events that occur.

Preoperative use of unfractionated heparin or its low-

molecular-weight variant is well agreed upon as a mainstay

of VTE chemoprophylaxis for all bariatric surgery patients

[11, 12, 14, 15]. Most (92.4 %) of our respondents used

preoperative chemoprophylaxis for high-risk patients. This

chemoprophylaxis was continued postoperatively, with the

majority (70 %) receiving the first dose on postoperative

day 0. The duration of chemoprophylaxis was much more

variable. Whereas 5 % of the surgeons discontinued che-

moprophylaxis at ambulation, 48.5 % discontinued treat-

ment at discharge. For high-risk patients, 43.8 % of the

surgeons continued chemoprophylaxis on an outpatient

basis for 2–4 weeks. Despite continuation of chemopro-

phylaxis for outpatients, only 47.4 % of the surgeons

routinely screened high-risk patients postoperatively for

DVT, with the majority of screening performed by physical

examination alone.

Although previous studies have shown that high-risk

patients are more likely to experience VTE formation for

3 months postoperatively and that continued chemopro-

phylaxis reduces the incidence of VTE [15, 22], no defin-

itive practice pattern was identified by our study. Nearly

half of the respondents continued chemoprophylaxis,

whereas the other half did not, and the surgeons did not

identify whether the patients discharged with medication

were considered higher risk than the patients discharged

without medication. Furthermore, no standardized postop-

erative screening method was used before discontinuation

of chemoprophylaxis.

Even more aggressive treatment is used by some sur-

geons, with placement of IVC filters. The use of IVC filters

has increased dramatically from 7 % of bariatric patients in

1997 to 55 % in 2007 [23]. Our survey demonstrated that

28.5 % of surgeons routinely use IVC filters in high-risk

bariatric patients. Nearly all the filters placed (99 %) are

the retrievable form (rIVCF). Although findings have

shown the permanent form of IVC filter to be beneficial in

preventing VTE for bariatric patients [24] in the short term,

846 Surg Endosc (2013) 27:843–848

123

a long-term study has shown an increase in DVT frequency

during a period extending to 8 years [25].

In the high-risk bariatric patient population, rIVCFs are

shown to have a low incidence of DVT, no clinically

evident PE, and the advantage of removal when the

greatest risk to the patient subsides [26]. The literature is

replete with data both supporting and refuting the use of

IVC filters. However, our survey showed that the majority

of surgeons do not use IVC filters routinely for high-risk

bariatric patients.

Conclusions

Overall, our study describes practice patterns with respect to

VTE identification, screening, and prophylaxis among high-

risk bariatric surgery patients. Nearly all the surgeons

(99.7 %) who responded to this survey agreed that high-risk

patients are identified by a group of risk factors (history of

DVT/PE, BMI [ 55 kg/m2, hypercoagulable disorders,

severe immobility, and PaO2 \ 60 mmHg). However, only

half (54 %) routinely screen for DVT preoperatively. Of

these, the majority use clinical examination alone.

Preoperative chemoprophylaxis for high-risk patients

was used by 92 % of the respondents, but the duration of

chemoprophylaxis varied. Nearly half of them discontinued

VTE chemoprophylaxis at discharge, with the remaining

surgeons doing so at 2–4 weeks. As reported, IVC filters

were not routinely used for the high-risk bariatric surgery

population, and less than half of the responding surgeons

routinely screened for DVT postoperatively.

Although certain practice patterns were apparent in this

survey, the duration of treatment and screening varied

significantly. Further studies are needed to determine

whether this variability is clinically significant. Ideally,

future prospective studies will compare screening and

prophylaxis patterns in an effort to determine which

regimen is the most efficacious and to establish an evi-

dence-based prophylactic treatment for VTE as well as

standardized screening for the high-risk bariatric patient.

Disclosures Howard I. Pryor II, Adam Singleton, Elissa Lin, Paul

Lin, and Khashayar Vaziri have no conflict of interest or financial ties

to disclose.

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