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consequences of withholding prophylaxis are o en over-
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looked. In addition to the short-term costs of delayed
hospital discharge due to an acute VTE event or patient
readmission for DVT, failure to prevent VTE increases
the risk of long-term morbidity due to PTS and recurrent thrombosis. Patients with symptomatic DVT have a
high risk of recurrent VTE that persists for at least 8years,
and which may increase with comorbidities such as can-
5
Estimates based on a recent cost-of-illness study con-
cer.
ducted by our group suggest that in the United States, the
annual per-patient cost of severe PTS is $3,816 in the rst
year and $1,677 therea er, while the cost of DVT and PE
complications were estimated at $3,798 and $6,604, respec-
41
erefore, prevention of DVT can have an enor-
tively.
mous impact on both the patient’s quality of life and the
long-term cost ofcare.
Mechanical methods of prophylaxis provide a cheaper
alternative to pharmacological methods taken on a direct
cost-per-patient basis, but this must be balanced with
issues of safety and e cacy. Mechanical devices, such as
intermittent pneumatic compression (IPC) and graduated
compression stockings (GCS), do not increase the risk of
bleeding and can o er important protection in some groups
of patients for whom anticoagulant therapy is contraindicated or is impractical because of their clinical status (e.g.,
trauma patients). One early study comparing ve methods
of thromboprophylaxis found that antistasis modalities performed well compared to the drug modalities (UFH, dextran, and aspirin), with the lowest incidence of DVT events
42
reported in the IPC group.
Asubsequent study evaluating
the e ectiveness of combining a pharmacologic drug with
an antistasis modality reduced the incidence of DVT to just
43
1.5% in a group of 328 surgical patients.
e value of combination therapy has been further highlighted in the more
recent APOLLO trial, which compared the use of IPC plus
fondaparinux with IPC alone in 1,300 high-risk abdominal
44
surgery patients in North America.
IPC was chosen on the
basis of a survey that found approximately half of clinicians
in the United States use this modality for the prevention
of thrombosis in general surgery patients. IPC showed 5%
incidence of DVT by venography—and is therefore itself
an e ective modality. A 1.7% incidence was reported for
IPC plus fondaparinux. A bene t is also suggested when
2
mechanical methods are combined with LMWH.
In a
review of trials comparing the use of GCS alone or in combination with LMWH in high-risk surgical patients (general and orthopedic), combination therapy was found to be
45
more e ective than pharmacological methods alone.
Overall, however, mechanical means of prophylaxis have
been less extensively studied than pharmacological methods,
and are generally considered less e cacious than anticoagulants for the prevention of DVT. While there is evidence
supporting the e cacy of mechanical devices in low-risk
2
patients,
they do not provide adequate prophylaxis in those
at high-risk. e most recent ACCP guidelines recommend
combination therapy for high-risk patients with multiple
risk factors, and that, in general, mechanical prophylaxis be
used primarily in patients who are at high risk of bleeding or
2
as an adjunct to anticoagulant-based prophylaxis.
THE BIGGEST PROBLEM:LACK OF
CLEA RDATA?
ere are established international guidelines based on
level-1 evidence that estimate the incidence of VTE in various populations, and then assess in as scienti c a way as possible the e cacy and safety of prophylactic methods based
on sound prospective randomized trials. However, only a
small subset of what is done in medicine has been tested in
appropriate, well-designed studies. Appropriate trials for
every clinical situation have not been, and probably never
will be, carried out for every situation.
When clinical data are either lacking or insu cient to
guide treatment, the physician has to use clinical reasoning
to identify the approach that best ts the patient and the
pathology involved. It can be frustrating to see patients not
being given e ective prophylaxis simply because there are
“no data available.” Such individuals may be at very high risk
of a thrombotic event, but there is no clear treatment path
because their clinical situations have yet to be subjected to
randomized prospective trials. So how do we ensure such
patients are treated appropriately?
MATCHING RISK WITH
PROPHYLACTIC STRATEGY
Routine screening of patients for symptomatic DVT is
logistically di cult, and both clinically and economically
2
ine cient.
Equally, reliance on clinical surveillance to
identify early symptoms or signs of DVT is inadequate to
prevent clinically important VTE events:the rst manifestation of VTE may be a fatalPE.
rombotic risk assessment allows patients to be strati ed according to their overall VTE risk and thromboprophylaxis to be tailored appropriately, but it is a complex
task that must take into account both exposing risk factors
relating to the clinical situation (e.g., duration/type/site of
surgery, type of anesthesia, concomitant illness, presence
of infection, etc.), and predisposing factors unique to the
individual patient (e.g., age, thrombophilic abnormalities,
history/family history of DVT, etc.). Many patients have
more than one VTE risk factor and are considered to be at
46–48
increased risk due to their cumulative e ect
(although
interestingly, a recent paper from the MEDENOX study
reported an insigni cant relationship between the number
49
of VTE events and the number of risk factors).
Risk assessment models (RAMs) have been developed with the intention of simplifying and standardizing the scoring of VTE
risk, and to allow optimization of prophylactic strategies.
298 • VENOUS THROMBOEMBOLISM
Unfortunately, there has been a history of poor compliance
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with RAMs, with a common complaint from physicians
being that they are overly complicated and logistically dif cult to implement in their own clinical setting. Many early
VTE risk-scoring systems also relied on diagnostic information not readily available from clinical examination (e.g.,
laboratory values such as euglobulin lysis levels), which has
led to reluctance among many doctors to implement such
systems.
A simple, clinically validated, easy-to-use RAM based on
factors in the patient’s medical history and clinical examination is needed, and has the potential to be widely adopted.
e model should be used to stratify patients according to
risk and the treatment strategy applied in conjunction with
academic guidelines where available, that is, the “hybrid
approach” to risk assessment.
A RAM developed by our team and implemented in
our hospital overcomes the complexities and practical constraints associated with previous models (Table 38.3).
50
e model includes clear lists of risk factors with a simple
accompanying scoring system, which allows patients to be
assigned to one of the four VTE risk categories identi ed in
the ACCP guidelines (low, moderate, high, very high), and
an appropriate prophylaxis regimen to be recommended
(Table 38.4). is RAM represents a thorough history
and physical relative to thrombotic risk. e following case
study highlights the value of a simple RAM in determining the prophylactic action required for a patient whose
risk of VTE is not easily categorized according to current
guidelines.
C A S E S T U D Y
Patient history
A 65-year-old man with a body mass index (BMI) > 30kg/m 2 ,
who received irradiation treatment for prostate cancer 5years
earlier, was found to have a 2-cm
during routine colonoscopy. e patient had been su ering
from in ammatory bowel disease for many years was taking
a statin for elevated cholesterol levels, had mild hypertension
with treatment and was on a baby aspirin daily. e patient
underwent a laparoscopically assisted colon resection that
lasted 2h 30 min. e patient did well postoperatively and
was discharged 6 d later. e path report con rmed the presence of an early cancer without signs of metastasis.
ere are no speci c data based on prospective randomized
trials on VTE risk and prophylaxis in a group of individuals with
this exact combination of risk factors. at is not to say there are
no relevant data because it is known that age >60years, BMI >
30kg/m
abdominal surgery for colon cancer are all risk factors for the
patient developing a VTE.
this patient receive given his risk factor pro le?
2
, in ammatory bowel disease, a history of cancer, and
2
3
carcinoma of the cecum
What form of prophylaxis should
TREATMENT
e patient received 5,000 U of heparin preoperatively and
during the operation, the patient was protected with pneumatic compression devices and elastic stockings to reduce stasis of blood in the legs during and immediately following the
procedure. In addition, a prophylactic LMWH was administered once daily for a month starting 24 h postoperatively. No
complications were reported during a 90-d follow-up period.
is approach may be considered extreme, and is endorsed at
the present time by only a minority of physicians in the United
States and worldwide.
So what is the clinical basis of this treatment strategy?
LINKING THERAPY ANDRISK
Based on clinical research to date, a patient undergoing a surgical procedure with more than ve risk factors has a 40 to
80% chance of developing a VTE, and this is associated with
2
a 0.2 to 5% rate of fatality from a PE.
According to the RAM
shown in Table38.3, the patient described in the case study
presented with ve VTE risk factors, which clearly placed him
in the highest risk category (age, cancer, obesity, abdominal
surgery, and IBD; Table38.4). Based on clinical trial data, in
abdominal surgery cancer patients 1month of daily LMWH
injections were done. Although there may be concerns about
the expense, the risk of bleeding or other adverse events, these
are small compared to the ≤5% risk of a fatal event in this
patient group ( ve factors; see Table38.4). Few passengers
would board a plane knowing there to be up to a 5% risk of
a fatal crash, which begs the question as to why an individual
would choose not to use e ective prophylaxis when there are
no clinical data contraindicating such an approach.
Furthermore, o en overlooked in this equation is the
impact of postoperative thrombosis. While postoperative
DVT can occur asymptomatically in the lower limbs, if
part of a clot breaks o , it may embolize to the right atrium.
Right-to-le shunt may then occur through a patent foramen ovale that temporarily opens due to atrial dilation in
response to the thrombus. Known as a “paradoxical embolism,” this allows the clot to pass into the systemic circulation,
whereupon it may lodge in the brain and lead to nonhemorrhagic stroke. In such cases, not only is there a 50% chance of
residual damage, including paralysis due to stroke, but 20%
of patients may die (Salinger, Disease-a-Month Feb-Mar,
2005). Is this a risk worth taking in postoperative patients
simply because they may be perceived to be at low risk?
Finally, these patients will probably not be fully ambulatory
while hospitalized and during the rst week post discharge.
ACCUMULATING EVIDENCE YET
ABSENCE OF GUIDELINES
In situations for which speci c data are not available, a conservative approach should be followed, and physicians must
THROMBOTIC RISK ASSESSMENT:AHYBRID APPROACH • 299
Table38.3 EXAMPLE OF APRACTICAL, EASYTOUSE, VTERAM
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rombosis risk factor assessment
Patient’s name:
Each factor represents 1 point:
• Age 41 to 60years
• Minor surgery planned
• History of prior major surgery (<1month)
• Varicose veins
• History of in ammatory bowel disease
• Swollen legs (current)
• Obesity (BMI > 25kg/m2)
• Acute myocardial infarction
• Congestive heart failure (<1month)
• Sepsis (<1month)
• Serious lung disease including pneumonia (<1month)
• Abnormal pulmonary function (chronic obstructive pulmonary disease)
• Medical patient currently on bed rest
• Other risk factors (specify)
Each factor represents 2 points:
• Age 60 to 74years
• Arthroscopic surgery
• Malignancy (present or previous)
• Major surgery (>45 min)
• Laparoscopic surgery (>45 min)
• Patient con ned to bed (>72 h)
• Immobilizing plaster cast (<1month)
• Central venous access catheter
Age: Gender: Weight:
Each factor represents 3 points:
• Age > 75years
• History of DVT/PE
• Family history of thrombosis*
• Positive Factor V Leiden
• Positive prothrombin 20210A
• Elevated serum homocysteine
• Positive lupus anticoagulant
• Elevated anticardiolipin antibodies
• Heparin-induced thrombocytopenia
• Other congenital or acquired thrombophilia
If yes, enter type:______________________
*Most frequently missed risk factor
Each factor represents 5 points:
• Elective major lower extremity arthroplasty
• Hip, pelvis, or leg fracture (<1month)
• Stroke (<1month)
• Multiple trauma (<1month)
• Acute spinal cord injury (paralysis; <1month)
(continued)
300 • VENOUS THROMBOEMBOLISM
Table38.3 CONTINUED
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For women only (each factor represents 1 point):
• Oral contraceptives or hormone-replacement therapy
• Pregnancy or postpartum (<1month)
• History of unexplained stillborn infant, recurrent abortion (≥3), premature birth with toxemia or growth-restricted infant
TOTAL RISK FACTOR SCORE
Prophylaxis safety considerations:Check box if answer is “YES”
Anticoagulants:Factors associated with increased bleeding
• Is patient experiencing any active bleeding?
• Does patient have (or has patient had history of ) heparin-induced thrombocytopenia?
• Is patient’s platelet count < 100,000/mm
• Is patient taking oral anticoagulants, platelet inhibitors (e.g.., nonsteroidal anti-in ammatory drugs, clopidogrel)
• Is patient’s creatinine clearance abnormal? If yes, please indicate value
If any of the above boxes are checked, the patient may not be a candidate for anticoagulant therapy and should consider alternative prophylactic
measures.
Intermittent pneumatic compression
• Does patient have severe peripheral arterial disease?
• Does patient have congestive heart failure?
• Does patient have an acute super cial/deep vein thrombosis?
If any of the above boxes are checked, the patient may not be a candidate for intermittent compression therapy and should consider alternative
prophylactic measures.
3
?
use reason where level-1 evidence is lacking. For example,
in terms of our exact case study patient, no clear guidelines
exist to guide management. Yet looking at the literature,
we see a strong case for prolonged prophylaxis. Two stud-
51
ies using the LMWHs dalteparin
and enoxaparin 52 have
shown that prolonging LMWH prophylaxis for a further 3
weeks is e ective in preventing DVT a er major abdominal
surgery in patients with cancer with no increase in bleeding
complications. Meta-analysis of these two studies con rmed
that prolonging LMWH for an additional 3 weeks following discharge signi cantly reduces the risk of late-occurring
Table38.4 PROPHYLAXIS DECISIONMAKING TOOL BASED ON VTE RISK SCORES
TOTAL VTE
RISK SCORE
0–1 <10 Low No speci c measures; early ambulation <0.01
2 10–20 Moderate LWMH (≤3,400 U once daily) or LDUH, (5,000 U bid)
3–4 20–40 High LMWH (>3,400 U daily), LDUH (5,000 U tid) or oral
≥ 5 40–80 Highest LMWH (>3,400 U daily) or LDUH (5,000 U tid) or oral
*Combining GCS with other prophylactic methods (LDUH, LMWH, or IPC) may give better protection.
e total risk score guides the physician to the most appropriate prophylactic treatment; risk categories correspond to the ACCP guidelines.
bid, twice daily; DVT, deep venous thrombosis; GCS, graduated compression stockings; IPC, intermittent pneumatic compression; LDUH, low-dose unfractionated
heparin; LMWH, low molecular weight heparin; PE, pulmonary embolism; tid, three times daily; VTE, venous thromboembolism.
(Modi ed with permission from Reference 2).
INCIDENCE
OF DVT %
RISK LEVEL RECOMMENDED PROPHYLACTIC REGIMEN RISK OF FATAL PE WITHOUT
or GCS* or IPC
anticoagulant alone or in combination with GCS or IPC
anticoagulant alone or in combination with GCS or IPC
VTE by 62%.
from 2,500 IU to 5,000 IU once daily for 7 d signi cantly
reduced the incidence of VTE in cancer patients, with no
increase in bleeding complications, a result of particular signi cance given that cancer patients are at increased risk for
bleeding.
6months) has also been shown to be more e ective than
an oral anticoagulant in reducing recurrent VTE in cancer
patients with no increased risk for bleeding,
studies suggest bene ts of LMWH for improved cancer sur-
56,57
vival.
53
An increased dose of the LMWH dalteparin
54
Long-term LMWH (dalteparin 200 IU/kg for
55
while further
is improved survival is thought to be associated
PROPHYLAXIS %
0.1–0.4
0.4–1.0
0.2–5
2
THROMBOTIC RISK ASSESSMENT:AHYBRID APPROACH • 301
with the antiangiogenic properties of LMWH that inhibit
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58
tumor progression.
THE IMPORTANCE OF WEIGHTING
RISK FACTORS
Without accounting for all risk factors, inadequate prophylaxis may result. While the aim is to develop a practicable
RAM that overcomes the hindering complexities of its predecessors, this must not be at the expense of oversimpli cation. For instance, in its categorization of risk groups, the
current ACCP guidelines lists patients >60years undergoing surgery as a high-risk group, with IPC as an acceptable
2
sole means of prophylaxis.
Is this misleading when we note
the increased incidence of VTE in cancer patients (up to 6
59
times higher than individuals without a malignancy
) and
see that LMWH or UFH are presented as the mainstays
of prophylaxis in this group? By assigning 6 points to such
a patient (2each for surgery, cancer, and age >60years) as
suggested in our RAM, the patient would clearly be placed
in the highest risk group, underlining the importance of
weighting the factors. In this case the IBD and obesity
reinforce placing this patient in the highest risk group.
Another key element was studied by Borow and Goldson
42
where incidence of venographic DVT was found to be
related to surgery duration (20% at 1–2 h, 46.7% at 2–3
h, 62.5% at >3 h). In this same study, age was also strati ed
(40–60, 61–70, 61–70, >71years), a weighting that is also
employed in our RAM and further validates the weighted
scoring system. e incidence of DVT in those over 71
is more than 60% compared to only 20% for ages 40–60.
We are currently in the process of implementing the RAM
in the electronic record and adding a reminder to encourage prophylaxis. e aim is to build on the positive results
(a41% reduced risk of VTE at 90 d) shown with the elec-
60
tronic alert developed by Kucher etal.
by combining it
with a strati ed approach to prophylaxis methods using
weighted risk factors.
VALIDATION OF THE CAPRINIRAM
Since 2007, several important validation studies have
appeared using the scoring system and correlating the score
with the subsequent development of clinically evident
61
imaging-proven VTE. In the rst study Seruya
performed
1,156 operations over a 2-year period and applied the risk
score to all of these patients. e authors identi ed 173
operations (15%) involving 120 patients with a risk score
greater than 4.Nine patients su ered a VTE (7.5%) including one nonfatal PE. All patients received prophylaxis with
either physical, pharmacologic, or combined modalities.
e authors suggested that combined physical and pharmacologic prophylaxis be used in patients with a score greater
than 4 along with outpatient LMWH. No clinical VTE
events occurred in patients with a score of less than4.
A major validation study reported from the University
of Michigan involved 8,216 surgical patients. Aretrospective score was obtained using the Caprini risk template
based on electronic medical records, the pharmacy database, and hospital coding records. e score was compared
to the 30-d incidence of clinically evident imaging-proven
62
VTE events.
Risk level was signi cantly associated with VTE
(1.9; 1.3–2.6, P < 0.01). e bivariate probit model
demonstrated signi cant correlation between the
probability of VTE and lack of adherence to pro-
phylaxis guidelines (0.299, P = 0.013). e over-
all incidence of acquired VTE within 30days was
1.44%. e incidence was associated with an increase
in risk level; of the patients in the highest risk level,
1.94% acquired a VTE; of the high-risk patients,
0.97%; moderate-risk patients, 0.70%; and low-risk
patients, 0%. e di erence between high and high-
est risk levels was statistically signi cant ( P < 0.001).
Further score breakdown revealed that patients with a
score of 5–6 had a 1.33% VTE incidence, those with a score
of 7–8 had a VTE incidence of 2.58%, and this percentage
rose to 6.51% in those with a score of 9 or above. Many of
us feel that these data are critical because the score can be
correlated with the eventual development of clinically signi cant VTE events.
Another recent validation study involving the Caprini
score involved over 1,126 patients in the Venous romboembolism Prevention Study (VTEP) in ve tertiary care
63
centers involving plastic surgery patients.
ey included
1,126 historic control patients .
e overall VTE incidence was 1.69%.
Approximately 1 in 9 (11.3%) patients with Caprini
score >8 had a VTE event. Patients with Caprini
score >8 were signi cantly more likely to develop
VTE when compared with patients with Caprini
score of 3 to 4 (odds ratio [OR] 20.9, p_0.001), 5
to 6 (OR9.9, p_0.001), or 7 to 8 (OR4.6, p_0.015).
Among patients with Caprini score 7 to 8 or Caprini
score >8, VTE risk was not limited to the immedi-
ate postoperative period (postoperative days 1-14).
In these high-risk patients, more than 50% of VTE
events were diagnosed in the late (days 15-60) post-
operative period.
e authors conclude that “ e Caprini RAM e ectively risk-strati es plastic and reconstructive surgery
patients for VTE risk. Among patients with Caprini
score >8, 11.3% have a postoperative VTE when chemoprophylaxis is not provided. In higher risk patients, there
was no evidence that VTE risk is limited to the immediate postoperative period.” is allows the clinician to
302 • VENOUS THROMBOEMBOLISM
recommend continued prophylaxis for those with high
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scores. Unfortunately, the ACCP guidelines contain little data regarding out-of-hospital prophylaxis except for
certain very speci c orthopedic and abdominal surgery
patients. e vast majority of patients seen in clinical practice have not been included in these trials so without risk
scores the clinician has very little data to formulate an
outpatientplan.
We are becoming aware that the vast majority of VTE
events occur following hospital discharge. e GLORY
orthopedic registry, according to the authors, has shown
the following:
e cumulative incidence of venous thromboem-
bolism within three months of surgery was 1.7%
in the THR and 2.3% in the TKR patients. e
mean times to venous thromboembolism were
21.5 days (SD 22.5) for THR, and 9.7 days (SD
14.1) for TKR. It occurred a er the median time
to discharge in 75% of the THR and 57% of the
TKA patients who developed venous thromboem-
bolism. Of those who received recommended forms
of prophylaxis, approximately one-quarter (26% of
THR and 27% of TKR patients) were not receiv-
ing it seven days a er surgery, the minimum dura-
tion recommended at the time of the study. e risk
of venous thromboembolism extends beyond the
usual period of hospitalization, while the duration
of prophylaxis is o en shorter than this. According
to the authors, practices should be re-assessed to
ensure that patients receive appropriate durations of
64
prophylaxis.
S U M M A R Y
High-quality clinical data are unlikely to be available to
guide thromboprophylactic decisions in all clinical situations, particularly for medical patients, in whom VTE has
been less extensively studied. orough and up-to-date academic guidelines are available and are the foundation for
treatment regimens; however, with new trial data constantly
emerging, there will always be some disparity between the
guidelines and clinical practice.
Despite the availability of e ective methods of prophylaxis, both surgical and nonsurgical patients continue to be
placed at risk of VTE and its potentially fatal complications,
such as PE or stroke, through the underuse of thromboprophylaxis. Prophylaxis is also being prescribed inappropriately, with patients at highest risk o en receiving ine ective
treatment due to misconceptions of VTE risk and concerns
about the safety of anticoagulant therapy.
Where rm recommendations are available, the physician should treat according to the evidence, but where evidence is lacking, the physician should assess each patient
based on their medical and clinical status and use a risk
factor model to help stratify patients according to risk.
Now that the scoring system has been validated, an additional guide to ongoing prophylaxis is available. Using
this “hybrid approach,” which combines clinical guidelines and intelligent clinical practice, more patients should
receive appropriate prophylactic treatment tailored to their
individualrisk.
R E F E R E N C E S
Another large, real-world database—the RIETE
registry—indicates that 77% of patients develop VTE
following hospital discharge, and in 55% of these individuals the thrombotic event occurred a er anticoagulant
65
prophylaxis was stopped.
e million-women study also
has shown the following, according to the authors:
Compared with not having surgery, women were 70
times more likely to be admitted with venous throm-
boembolism in the rst six weeks a er an inpatient
operation (relative risk 69.1, 95% con dence inter-
val 63.1 to 75.6) and 10 times more likely a er a
day case operation (9.6, 8.0 to 11.5). e risks were
lower but still substantially increased 7–12 weeks
a er surgery (19.6, 16.6 to 23.1 and 5.5, 4.3 to 7.0,
respectively). is pattern of risk was similar for
pulmonary embolism (n=2487) and deep venous
66
thrombosis (n=3529).
As can be seen from all of these data, the ongoing use of
prophylaxis is becoming increasingly important and can be
guided by risk scores until further studies aredone.
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THROMBOTIC RISK ASSESSMENT:AHYBRID APPROACH • 305
39.
https://t.me/med1917
VENOUS THROMBOEMBOLISM PROPHYLAXIS IN THE
GENERAL SURGICAL PATIENT
J. I. Arcelus and J. A. Caprini
INTRODUCTION
Patients undergoing major surgery are at a twenty-fold
increased risk for development of venous thromboembolism (VTE), an o en asymptomatic condition that encompasses both deep venous thrombosis (DVT) and pulmonary
embolism (PE).
1975 that the observed rate of DVT by an isotopic technique in general surgery patients who did not receive VTE
prophylaxis was nearly 30%.
ized trials in general, orthopedic, and urologic surgery conducted 30years later reported similar results (27% incidence
of DVT and 3.4% incidence of fatal PE).
more than y trials published between 1970 and 1985
showed that the overall postoperative incidence of DVT as
assessed by brinogen uptake test (FUT), a study in which
radiolabeled brinogen is incorporated into newly formed
thrombi, and/or contrast venography ranges from 19 to
29% in untreated patients who undergo general surgery.
Rates of total and fatal PE were approximately 1.6% and
0.9%, respectively. e majority of patients included in this
pooled analysis underwent elective gastrointestinal surgery,
although some study populations also included patients
who had undergone gynecologic, thoracic, urologic, or vascular surgery.
In the United States, DVT is reported to a ect up to
145 individuals per 100,000 per year in the general population, and it is accompanied by PE in up to 69 individuals
per 100,000.
VTE diagnosed in European or North American countries occurred in patients who underwent surgery several
weeks before, and almost half of them were general surgical patients.
high risk of VTE in general surgery patients, clinical studies
without prophylaxis are no longer performed in this patient
population and, thus, the current risk of VTE is unknown.
e incidence of VTE in this patient population without
prophylaxis was approximately 30% in studies done in
the 1970s and 1980s.
the incidence ranges from 4.6 to 8%. Despite the seriousness of the condition and its high prevalence, it has been
1
Kakkar and colleagues demonstrated in
2
Ameta-analysis of random-
3
Pooled data from
5
Approximately 11 to 16% of all symptomatic
6
Because of the strong data demonstrating the
2,3
With pharmacologic prophylaxis,
4
demonstrated that 25 to 62% of general surgery patients
do not receive any form of prophylaxis, as opposed to stan-
7,8
dard therapy in clinical trials.
Furthermore, a recent epidemiologic study shows that only 59% of surgical patients
at high risk to develop postoperative VTE received appropriate prophylaxis according to ACCP recommendations.
Clearly, there is a need to improve venous thrombosis prevention in general surgery patients at high thromboticrisk.
Postoperative VTE is di cult to diagnose because it is
o en asymptomatic or, when symptoms are present, they
usually are nonspeci c. Symptoms of DVT include leg pain,
swelling, and heaviness. Symptoms of PE include chest
pain, shortness of breath, tachypnea, transient orthostatic
hypotension, fainting spell, hypoxia, and sudden death.
Although many surgeons may feel that they do not o en
see VTE postoperatively, many most likely see these signs of
VTE o en, but overlook their possible connection to VTE.
Actually, in 70 to 80% of patients who died from a PE con rmed by autopsy, this diagnosis was not even considered
prior to a patient’s death.
10,11
e prevention of VTE is important because both
symptomatic and asymptomatic VTE are associated
with long-term consequences, even when the condition
is diagnosed and treated. A common, serious complication associated with DVT is postthrombotic syndrome
(PTS). PTS is characterized by permanent vein damage
that results in chronic leg swelling that worsens during the
day, which may be accompanied by the presence of varicose
veins, edema, skin discoloration, and skin ulcerations. In
a prospective inception cohort study of 528 patients with
venography-con rmed DVT, 19% of whom were postoperative, the cumulative incidence of PTS at 2, 5, and
8years following initial diagnosis and treatment was 24.5%,
12
29.6%, and 29.8%, respectively.
PTS also represents a signi cant economic impact of DVT. It has been estimated
that 15million Americans are a icted with PTS and that
2million work days are lost annually due to the condition.
Recurrent DVT or PE is also a common clinical consequence of VTE. e cumulative incidence of recurrent
VTE a er 2, 5, and 8years of follow-up in the above mentioned study by Prandoni was 17.2%, 24.3% and 29.7%,
9
306
respectively. Arare but serious consequence that is associ-
https://t.me/med1917
ated with symptomatic and asymptomatic DVT is fatal PE.
It has been estimated that less than 50% of patients are alive
13
1year following an acute PE.
According to the results of
the RIETE registry, the mortality of acute PE is around 12%
6
in the rst 3months a er diagnosis.
In addition, almost 4%
of patients who survive an acute PE will develop chronic
14
pulmonary hypertension.
PE is also associated with embolic stroke in patients
with patent foramen ovale (PFO), a condition estimated
to be present in 10% to nearly 30% of the general popula-
15,16
tion.
PE can lead to elevated pressures in the right side
of the heart, which can lead to expansion of PFO. Aclot
or part of a clot can move from the right to le chamber
of the heart through the expanded PFO, causing cerebral
and peripheral ischemic events characteristic of paradoxical embolism (passage of a clot from a vein to an artery).
17
ese serious, disabling, and sometimes fatal consequences
of VTE underscore the importance of prevention in patients
at risk, including patients undergoing general surgery.
Although a high incidence of VTE has been demonstrated in general surgery patients, risk for VTE varies
among general surgery patients, and di erent methods of
prophylaxis are appropriate for di erent levels of risk. An
optimal approach to risk assessment and VTE prophylaxis
should combine evidence-based and clinical practice guidelines with clinical experience where a lack of science exists.
Several risk factor assessment models have been proposed to
predict VTE risk preoperatively, but only one of them has
18–22
been validated prospectively.
Table39.1 RISK FACTORS FORVTE
Patient Factors
• Age >40years • Pregnancy
• Prolonged immobility • Puerperium
• Obesity • High-dose estrogen therapy
• History of DVT or PE • Varicose veins
Medical/Surgical Risk Factors
• Major surgery (especially
involving the abdomen, pelvis,
lower extremities)
• Malignancy (especially pelvic,
abdominal, metastatic)
• Myocardial infarction • In ammatory bowel disease
• Stroke • Nephrotic syndrome
• Fractures of the pelvis, hip, or leg • Pacemaker wires
• Polycythemia • Paraproteinemia
• Paroxysmal nocturnal
hemoglobinuria
Hypercoagulable States
• Lupus anticoagulant and
antiphospholipid antibodies
• Homocystinemia • HIT
• Dys brinogenemia • Protein C de ciency
• Myeloproliferative disorders • Protein S de ciency
• Antithrombin de ciency • Hyperviscosity syndromes
• Factor V Leiden • Prothrombin gene mutation
• Disseminated intravascular
coagulation
• Acute respiratory failure
• Congestive heart failure
• Behcet’s disease
• Disorders of plasminogen
and plasminogen activation
20210A
RISK FACTORS FORVTE
Although the risk for VTE is increased in most patients
undergoing major general surgery, the relative risk for postoperative development of this complication varies among
individual patients based on numerous factors, including the length of immobilization following surgery, the
type of surgery performed, and the presence of comorbid
1,23,24
conditions (Table 39.1).
Important patient-speci c
or intrinsic risk factors for VTE include age greater than
40years, ethnicity, cancer, and body mass index (BMI) over
25. Arecent retrospective study in general surgery patients
found that, while a steady rise in the incidence of VTE is
seen between 40 and 75years of age, this increase does not
23
continue above the age of 75years.
Among the extrinsic or exposing risk factors related to
the hospital admission, immobilization for an extended
period of time is a well-established risk factor for VTE,
and early mobilization following surgery has been shown to
25
lower the risk for postoperative VTE.
ere is also strong
evidence that the type of surgical procedure a patient undergoes is predictive of the risk for postoperative VTE. Major
general surgery (usually de ned as abdominal or thoracic
operations that require general anesthesia lasting >45 minutes) is associated with a high risk of VTE. Orthopedic
surgery is also associated with a high risk for VTE. In a retrospective study of more than 1million surgery patients, the
incidence of symptomatic VTE was highest among patients
who underwent orthopedic surgery of the hip or knee as well
as those who had invasive neurosurgery involving brain incision, excision, or biopsy. Other procedures associated with a
substantially increased risk for VTE included major vascular
surgery, small or large bowel resection, gastric bypass, radical cystectomy, kidney transplantation, and below-the-knee
amputation. Alow risk of VTE was reported with radical neck dissection, inguinal hernia repair, appendectomy,
laparoscopic cholecystectomy, transurethral prostatectomy,
repair of a cystocoele or rectocoele, cruciate ligament repair,
23
and thyroid or parathyroid surgery.
Certain medical conditions, including congestive heart
failure, chronic obstructive pulmonary disease, recent
myocardial infarction, stroke, nephrotic syndrome, in ammatory bowel disorder, and systemic lupus erythematosus
13
are known to increase the risk for VTE.
ticularly strong association between cancer and VTE.
ere is a par-
26,27
VTE PROPHYLAXIS IN THE GENERAL SURGICAL PATIENT • 307
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