INTRODUCTION
Deep vein thrombosis (DVT) prophylaxis in burns patients has always been a contentious
issue. Burn injury results in the hypercoagulable state due to increase in prothrombotic
factors such as factors V, factor VIII, platelet count and fibrinogen[1] which increases the risk of DVT and fatal pulmonary embolism (PE). The American
College of Chest Physicians (ACCP) guidelines published in 2008 recommend DVT prophylaxis
in burn patients with specific risk factors.[2]
The reported incidence of DVT in burn patients range from 0.25% to 23% in various
case series,[3]
[4] but various issues such as the actual incidence of DVT, the need for chemoprophylaxis,
the duration, dosage and complications of low molecular weight heparins (LMWH) remain
unanswered due to the absence of any randomised controlled trial.
We conducted a survey amongst plastic surgeons attending National Academy of Burns
India Conference (NABICON) 2012 held in New Delhi, India, regarding the type of DVT
prophylaxis in burns patients so as to get the data about the current practice in
our country and as a positive step in the ultimate goal of formulating Indian guidelines
for better care of patients suffering from burns based on the existing literature.
METHODOLOGY
This survey was conducted during the NABICON 2012 held at India Habitat Centre, New
Delhi from February 3, 2012 to February 5, 2012 by circulating a questionnaire containing
20 questions [Table 1] among the delegates attending the conference.
Table 1
Questionnaire
-
Do you practice Burns?
-
What percentage of your practice constitutes Burns? ______%
-
Do you practice DVT prophylaxis in Burns?
-
What is the incidence of DVT in Burns in your practice______%
-
How do you diagnose DVT in your practice?
-
a. Clinical
-
b. Duplex Scan
-
What are the criteria for selecting DVT prophylaxis in your practice?
-
What is the minimum percentage of burns that you start DVT prophylaxis in your practice?______%
-
Do you use DVT prophylaxis in children with burns?
-
When do you start DVT prophylaxis?
-
What is the modality of DVT prophylaxis do you use?
-
a. Chemoprophylaxis
-
b. Crepe bandage
-
c. Pneumatic compression
-
d. Combined
-
How long do you continue the prophylaxis?
-
a. Specific period (______days)
-
b. Till the patient is ambulated
-
c. Till the time of discharge
-
Which molecule do you prefer using in DVT prophylaxis?
-
a. Enoxaparin
-
b. Rivaparin
-
c. Dalteprin
-
d. Bemiparin
-
e. Others if any
-
What is the dose of L.M.W.H. you use in DVT prophylaxis? ______
-
Did you ever encounter morbidity/mortality related to DVT?
-
Did you ever encounter complication related to L.M.W.H.?
-
Do you stop L.M.W.H. prior to surgery?
-
Do you think L.M.W.H. dosage is to be adjusted based on % of burns?
-
Do you think L.M.W.H is under utilized in burn?
-
What do you suggest to promote DVT prophylaxis in burns?
______
-
Why do you think DVT prophylaxis is not required in burns? Kindly brief
______
Name: ______
Signature: ______
Address: _____
|
The questionnaire was not announced before the conference, was distributed at the
beginning of a scientific session in the forenoon on the 1st day of the conference and collected back during the same session. This was done to
prevent any discussion among the delegates and possible bias while answering the questionnaire.
Out of the 60 questionnaires’ circulated, 46 participants responded. The data collected
was then tabulated and the results were analysed for each question. The respondents
were divided into two groups based on their response to question number 2. Group I
consisted of respondents whose practice constituted >50% of burns patients, we labelled
them as Burns’ surgeons and Group II were respondents whose practice constituted <50%
of burns patients and were plastic surgeons who practiced burns’ regularly. Then,
to test for the level of significance between the two groups, the Chi-square test
was used to calculate the “p” value.
RESULTS
Among all the respondents, 68.2% of them practiced some form of DVT prophylaxis in
their practice, whereas 75.2% in Group I and 64.3% in Group II practiced DVT prophylaxis,
but this difference was not significant between the two groups (P = 0.468).
Only 40% of the respondents used a duplex scan to diagnose DVT; the rest preferred
clinical methods, 41.7% in Group 1 and 38.9% in Group 2 used duplex scanning, here
again, the difference between the two groups was not significant (P = 0.681).
When the respondents were asked as to what factors they considered to be criteria
for DVT prophylaxis in their practice (Q no 6), most of them (72.7%) responded that
they would consider all the factors (age, % of burns, comorbidities and type of burn)
as criteria for starting DVT prophylaxis in any burn patient. Nearly 9.1% of respondents
in the Group I said that they would consider age as a sole criteria, but none in Group
II (0%), whereas 5.6% of respondents in Group II said that they would consider associated
Comorbidities of the patient as a criteria for starting DVT prophylaxis and none of
the respondents in the Group I considered associated comorbidities as a criteria.
The majority of the respondents (79.3%) said that they would not use DVT prophylaxis
in children (Group I-66.7%, Group II-88.2%, P = 0.158).
Two-thirds (63.3%) of the study participants opined that they would start DVT prophylaxis
once the patient is haemodynamically stable, 36.7% wanted to start DVT prophylaxis
on admission itself, there was no significant difference between the two groups in
this aspect (Group I-61.1%, 38.9%, Group II-63.3%, 36.7%, P = 0.757).
When the participants were asked as to what modality of DVT prophylaxis they preferred,
the majority of them (70%) said that they would use a combined approach of prophylaxis
that included chemo-prophylaxis, pneumatic compression and crepe bandage application.
The responses were similar between the two groups (Group I-75% (all), 25% (chemo alone),
Group II-66.7% (all), 5.6% (pneum comp), 27.8% (chemo alone) P = 0.684).
The majority (73.3%) of the respondents in this survey said that they would continue
DVT prophylaxis only until the patient became ambulant, whereas others would continue
DVT prophylaxis till discharge. (Gr. I-66.7% (ambulation.), 16.7% (discharge), 16.7%
(1 week.), Group II-77.8% (ambulation.), 5.6% (discharge.), 16.7% (1 week.), P = 0.603).
The majority of the study participants has encountered morbidity related to DVT in
burns patients (overall-76.7%, Group I-75%, Group II-77.8% P = 0.860).
When participants were asked whether they have encountered any complication with LMWH,
none of the respondents in Group II had experienced any complications, whereas 41.7%
of respondents in the Group I had experienced complications with LMWH (P = 0.003).
The majority of the respondents feels that LMWH is underutilized in burns (overall-89.7%,
Group I-91.7%, Group II-88.2% P = 0.765) and also that it should be stopped before surgery (overall-73.3%, Group
I-75%, Group II-72.2% P = 0.866).
Most of the respondents (62.1% Group I-75% Group II-52.9% P = 0.228) do not adjust the dose of LMWH depending on the percentage of burns. The
results are tabulated as the questions with two answers as options [Table 2] and the questions with four answers as options [Table 3].
Table 2
Results for the questionnaire with two options as answers
|
Question number
|
<50%
|
>50%
|
Combined
|
P
|
|
A (%)
|
B (%)
|
A (%)
|
B (%)
|
A (%)
|
B (%)
|
|
3
|
64.3
|
35.7
|
75.0
|
25.0
|
68.2
|
31.8
|
0.521
|
|
5
|
61.1
|
38.9
|
58.3
|
41.7
|
60.0
|
40.0
|
0.879
|
|
8
|
11.8
|
88.2
|
33.3
|
66.7
|
20.7
|
79.3
|
0.198
|
|
9
|
38.9
|
61.1
|
33.3
|
66.7
|
36.7
|
63.3
|
0.757
|
|
14
|
77.8
|
22.2
|
75.0
|
25.0
|
76.7
|
23.3
|
0.860
|
|
15
|
0.0
|
100.0
|
41.7
|
58.3
|
83.3
|
16.7
|
0.003
|
|
16
|
72.2
|
27.8
|
75.0
|
25.0
|
73.3
|
26.7
|
0.866
|
|
17
|
52.9
|
47.1
|
75.0
|
25.0
|
62.1
|
37.9
|
0.228
|
|
18
|
88.2
|
11.8
|
91.7
|
8.3
|
89.7
|
10.3
|
0.765
|
Table 3
Results for the questionnaire with four options as answers
|
Question number
|
<50%
|
>50%
|
Combined
|
P
|
|
A
|
B
|
C
|
D
|
A
|
B
|
C
|
D
|
A
|
B
|
C
|
D
|
|
6
|
0.0
|
22.2
|
5.6
|
72.2
|
9.1
|
18.2
|
0.0
|
72.7
|
3.4
|
20.7
|
3.4
|
72.4
|
0.512
|
|
10
|
27.8
|
0.0
|
5.6
|
66.7
|
25.0
|
0.0
|
0.0
|
75.0
|
26.7
|
0.0
|
3.3
|
70.0
|
0.684
|
|
11
|
16.7
|
77.8
|
5.6
|
-
|
16.7
|
66.7
|
16.7
|
-
|
16.7
|
73.3
|
10.0
|
-
|
0.603
|
|
12
|
96.43
|
0.0
|
0.0
|
3.57
|
100.0
|
0.0
|
0.0
|
0.0
|
97.73
|
0
|
0
|
2.27
|
-
|
DISCUSSION
There is a paucity of data regarding DVT prophylaxis in burns’ patients due to limited
research on this subject. The ACCP 2008 guidelines recommend routine chemical venous
thromboembolism (VTE) prophylaxis in burn patients with specific risk factors. These
risk factors are as follows: older age, lower extremity burns, morbid obesity, associated
trauma, the use of femoral central venous catheters or prolonged immobilisation.[2]
The National Burn Conference held in New Delhi was the ideal location to conduct this
survey as it provided us a unique opportunity where the entire community of Burns’
specialists of India would come together.
The rationale for dividing the respondents into two groups depending on how much of
their percentage of practice constituted burns’ patients was to ascertain whether
the respondents whose practice constituted >50% of burns patients, whom we could call
as “burns” surgeons’ were any different than other plastic surgeons whose practice
constituted <50% but treated burns on a regular basis with respect to their current
knowledge on DVT prophylaxis in burns. The only significant difference between the
two groups was in the area of complications related to LMWH, where the plastic surgeons
whose practice of burns was <50% did not encounter any complication with LMWH, whereas
41.7% of the burns’ surgeons did.
Nearly 68.2% of the respondents in our survey practiced DVT prophylaxis in burns;
this is in accordance with the recent survey of 84 burn centres in the United States
revealed that 76.1% of these centres used some form of DVT prophylaxis.[5] In our country where there are no existing guidelines regarding burns’ management,
our survey reveals an interesting finding that a majority of plastic surgeons considered
DVT prophylaxis as necessary in burns’ patients.
There is enough evidence to suggest that most of the DVT, which occurs in burns’ patients,
is asymptomatic and goes unnoticed by the physician.[4] This has been exemplified by the fact that the incidence of DVT in retrospective
studies is quite low (<1%),[6]
[7] whereas in a small prospective study by Wahl et al. where all burns’ patients were screened for DVT the incidence was as high as 23%.[3] This difference can be attributed to the fact that in retrospective studies only
symptomatic patients underwent duplex scanning.
In our survey, only 40% of the respondents preferred duplex scanning to clinical examination
as the method to diagnose DVT. This is surprising as only 40% of patients with DVT
manifest any clinical signs and duplex is mandatory to confirm the diagnosis of DVT.[8]
There is evidence from retrospective studies that there are specific risk factors
for development of symptomatic DVT in burns’ patients, Pannuci et al. have used the National Burn Repository of America (NBR) data to develop a predictive
model for VTE which identifies many risk factors such as increased age, medical comorbidities,
presence of inhalation injury, the need for intensive care unit (ICU) admission, increased
number of ICU days, mechanical ventilation over 48 h, increased number of operative
procedures, and increased TBSA(Total Body Surface Area).[4]
The ACCP guidelines also recommend that the presence of specific risk factors mandates
chemoprophylaxis. The majority of the respondents in our survey opined that they would
consider all the risk factors (% of burns, age, medical comorbidities, type of burn)
as criteria to initiate prophylaxis, which is in accordance with the ACCP guidelines.
However, Wahl et al. retrospective study showed that the risk factors enunciated by Pannuci et al. did not hold good in their subset of patients and that DVT developed in patients
without any of those risk factors and the only two factors which increased the risk
of DVT/VTE were the presence of lower extremity burns and infection of the burn wound.[8]
There are no existing guidelines regarding the timing and duration of DVT prophylaxis
in burns patients. Lin et al. in their study have used nonambulation for >48 h and ICU admission as criteria for
starting DVT prophylaxis and prophylaxis was discontinued in their study when the
patient was able to ambulate at least thrice a week or a distance of 125 feet.[9]
Conventionally for other indications such as major general/gynecological/orthopedic
surgeries, the ACCP recommends prophylaxis for up to 35 days with LMWH and a minimum
of 10 days.[2] There are problems in using ambulation as criteria to stop DVT prophylaxis, first
being that it is a subjective criterion and secondly, that DVT can develop even in
the ambulatory patients.[10]
In our survey, the majority of the respondents opined that they would start DVT prophylaxis
once the patient is haemodynamically stable. Even though this decision appears prudent
in the authors’ opinion, there is no evidence to back it up.
Chemical method of prophylaxis has been shown to be the most effective and LMWH is
the drug of choice in the majority of the patients,[11]
[12] except in certain circumstances where LMWH has been contraindicated, such as decreased
creatinine clearance. Other methods come into play in combination with LMWH, or when
LMWH has been contraindicated, these methods include graduated compression stockings,
intermittent pneumatic compression devices, warfarin, fondaparinux and Vitamin K antagonists.[12]
In burns’ patients chemoprophylaxis appears to be more suitable as the application
of compression stockings and devices would be difficult if the lower extremity is
involved. The ACCP guidelines recommend LMWH as the drug of choice.[11] In cases of an increased risk of bleeding, the guidelines recommend mechanical thromboprophylaxis
in the form of graduated compression stockings or intermittent pneumatic compression
devices.
Most of the respondents in our survey used a standard dosage of 1 mg/kg of Enoxaparin
twice daily for DVT prophylaxis. The ACCP recommends that clinicians need to follow
the manufacturer's guidelines while deciding the dosage.[2] In the study by Lin et al. 30 mg bid has been used for prophylaxis and 1 mg/kg bid as a therapeutic dose, but
the same authors have proved that this tradition dosing is inadequate by measuring
anti-factor Xa levels in severely burned patients and have devised a formula to calculate
enoxaparin dosing which incorporates the TBSA and body weight.
(Enoxaparin dose (mg every 12 h) = 22.8 + 3.3 × (TBSA/10) + 1.89 × (wt/10).[9] However, further studies are needed to recommend routine clinical usage of this
formula.
Causes of death after severe burn have changed over time; in the international literature,
multisystem organ failure is seen as the most important cause,[13] but 76.7% of the respondents in our survey have experienced morbidity/mortality
related to DVT in burns’ patients. This is in accordance with the data from prospective
studies by Wahl et al.[3]
LMWH are relatively safe drugs, known complications include thrombocytopenia and increased
risk of bleeding, allergic reactions, mild elevation of hepatic transaminases, osteoporosis,
injection site abscess, or hematoma. LMWH are contraindicated if creatinine clearance
is <30 ml/min as they are excreted through the kidney.[14]
Nearly 41.7% of the study participants in Group I had encountered complications related
to LMWH in our study; whereas none of the participants in the other group had encountered
any morbidity with LMWH. This could be explained by the fact that the burns’ surgeons
had more experience in identifying complications of LMWH, although the explanation
may not be completely satisfactory.
Although it may appear logical to stop LMWH before surgery, as 73.3% of our respondents’
do, due to the fear of excess intraoperative bleeding, Recent evidence, however, suggests
that the risk of developing a potential complication with LMWH has to be balanced
against the potential for developing VTE in the particular patient. There are known
reports of patient developing epidural hematomas who are on LMWH, leading to neurological
deficits. Hence, it is advised that for patients on anticoagulation, neuraxial blockade/subarachnoid
block be given when the effect of the anticoagulant is minimal.[15] Kearon et al. have recommended that it is necessary to stop LMWH 12 h before surgery.[16]
The conventional dosing of LMWH does not change with respect to percentage of burns,
but Lin et al. in their study on enoxaparin dosing have used the TBSA as part of their formula,
Harrington et al. in their study of 1300 thermally injured patients have concluded that the sum of
age and TBSA has the potential to identify those group of patients at high risk of
developing DVT/PE.[17] Pannucci et al. in their analysis of the data from the NBR have shown that those patients with burns
between 40% and 59% have the highest risk of developing DVT/VTE (2.4%), whereas for
those with higher TBSA (<60%) the risk appeared to be lower.[4] This could be due to physicians being more aggressive while treating salvageable
burns (<60%) or due to the higher chances of developing disseminated intravascular
coagulation which could derail the clotting process in patients with >60% burns or
the patients died before they developed DVT and VTE.[18]
When our respondents were asked as to what they would suggest to promote DVT prophylaxis
in burns, the suggestions were that it needs to be incorporated into the textbooks,
more importance needs to be placed on them during conferences, and more multicentre
studies were needed before promotion and also to maintain a high index of suspicion
in burns’ patients. The ACCP guidelines suggest that to increase adherence to thromboprophylaxis
the use of computer decision support systems (Grade 1A), preprinted orders (Grade
1B) and periodic audit and feedback (Grade 1C). Passive methods such as the distribution
of educational materials or educational meetings are not recommended as sole strategies
to increase adherence to thromboprophylaxis.[2]
The available LMWHs approved for use in the U. S. include enoxaparin, dalteparin and
tinzaparin.[19] There are similarities as well as the difference between these molecules with respect
to molecular weight, and biological action. However, enoxaparin is the most widely
used and extensively available.[20] White et al. in their review on LMWH have concluded that enoxaparin, dalteparin and tinzaparin
have roughly comparable clinical efficacy in the treatment and prevention of VTE.
This topic has not been given its due importance in international conferences by various
burns’ association all over the world, for example, since 2013 the topic has appeared
only in 9 abstracts, which forms <2% of the total number of abstracts presented at
the annual conference of the American burns’ association.[21]
[22]
[23] It is similar to the British Association, having no important session about DVT
prophylaxis in burns’ patients in their latest annual conference.[24]
This survey represents a small group of plastic surgeons of India who attended NABICON,
and generalisation of the data are difficult. Other limitations of our survey were
that the questionnaire did not include factor Xa assay and there were open-ended questions.
The authors strongly feel the need for a simple protocol which includes various risk
factors like % and degree of burns, lower limb involvement, age, obesity, wound infection,
and other comorbidities to decide on starting the DVT prophylaxis and simpler formula
to adjust the dosage of LMWH, which necessitates a large prospective multi-centric
randomised control trials.
