Practice of DVT prophylaxis among Orthopedic Surgeons in Eastern Nigeria
Madu K.A, Madu A.J, Lekwa N.K
Abstract
Objectives: Deep vein thrombosis (DVT) is a common complication of major orthopedic surgery
with a very potentially lethal outcome. Thromboembolic prophylaxis has been established to be
effective in the prevention of deep vein thrombosis and various regimen are in use. Prophylactic
guidelines follow the recommendations of the American College of Chest Physicians (ACCP).
The aim of the study was to evaluate the practice pattern of orthopedic surgeons in eastern
Nigeria with regards to DVT prophylaxis.
Subjects and Methods: This was a prospective study spanning 12 months and involving patients
who had major orthopedic surgery in that period. The sample size was 139 patients and the data
collected included the Caprini risk category and DVT prophylaxis received. Adequacy of
prophylaxis received was assessed using the ACCP guidelines. The patients were followed till
discharge to monitor for any adverse venous event.
Results: DVT prophylaxis was given to 46% of the patients in this study while the use of anti
coagulation was found to conform to the ACCP recommendations in 43.2% of the patients.
Defaults in duration of anti coagulation was the problem in 70.9% of patients whose prophylaxis
did not conform to the guidelines. Non use was observed in the remaining patients. The age of
the patient and the risk categorization were found to positively correlate with the use of
prophylaxis.
Conclusion: Inadequate DVT prophylaxis was a common problem in our environment. Sub
optimal prophylaxis and omission of prophylaxis were found to be common problems among
patients who had major orthopedic surgery.
Short title: DVT prophylaxis in south east Nigeria
Key words: deep vein thrombosis, prophylaxis, practice pattern, risk category.
Introduction
Deep vein thrombosis (DVT), and pulmonary embolism, occurs at an annual incidence of
approximately 1 in 1000 adults. (1) The incidence of post-surgical venous thromboembolism
(VTE) was found to be 0.8%, for all surgeries. (2) In orthopedic patients with fractures the
overall incidence of DVT is 28% and tends to be higher when the proximal aspects of the lower
limb are affected. (3) However, the highest incidence of thromboembolism has been reported
post-operatively in females with knee replacement arthroplasty and hip fracture surgery. (4, 5)
The true incidence of VTE in the Nigerian population is difficult to determine, since half of the
post-operative cases develop VTE after 91 days (2) by which time they must have been
discharged. However studies done by Osime et al in Nigerian patients post-surgery revealed the
incidence of clinically evident DVT to be 2.2%. (6) Major orthopedic surgery is associated with
a very high risk of venous thromboembolism. (3) There is a marginal variation in incidence
across the various races with a higher incidence in the Caucasians and African-Americans
compared to Asians and Hispanics. (1) Without prophylaxis, DVT may occur in up to 60% of
patients within 2 weeks after lower extremity orthopedic surgery 2. Deep vein thrombosis, thus,
is a common complication of major orthopedic procedures with the potentially lethal outcome of
pulmonary embolism, respiratory distress and death.
Various thromboprophylactic regimen exist and have proven to be effective for DVT prophylaxis
including use of agents like low molecular weight heparin (warfarin, dabigatran etexilate,
fondaparinux) (7) as well as anti-platelet (aspirin) and intermittent compression pneumatic
devices. Low molecular weight heparin prophylaxis reduces the incidence of DVT and
pulmonary embolism to about 5.3% and 0.13%, respectively. (8) However, fractures as well as
procedures affecting certain sites have not be associated with a high risk of thromboembolism,
(9) thus the need for risk categorization. Deep vein thrombosis risk is classified into risk
categories ranging from low risk to highest risk using the Caprini risk assessment model4. (10)
The protocol of DVT prophylaxis varies widely across various institutions and surgical units, (8)
while some controversy exists with acceptance of a particular protocol or the necessity for the
use of prophylaxis at all. (11-13) Individual risk factor assessments, by the Caprini or Padua risk
assessment model, have also found use in surgical practice. (11) These models score patients
using the presence or absence of clinical variables to return scores predictive of the likelihood of
thromboembolism.
The American College of Chest Physicians (ACCP) guidelines first published in ninth edition is
the most widely accepted and validated, (7, 13, 14) and was used for the purpose of this study.
The ACCP guidelines have undergone several modifications and the current practice guideline
for orthopedic surgery patients was updated in February, 2012. (7, 14) This update used surgery
specific risks and made recommendations involving the use of both pharmacological and
mechanical agents for various categories of orthopedic surgery. Recommendations also included
no prophylaxis for some categories of surgery. The ACCP-9 has also been found to be superior
to other practice guidelines in terms of treatment outcome. (15) The practice of DVT prophylaxis
has been observed to have improved in past years, while significantly sub-optimal use of DVT
prophylaxis has been reported in patients undergoing surgery. (16) Confirmation of suspected
cases is usually necessary and involves duplex ultrasound of the affected limb to assess patency
of the large veins. However, venography though an invasive diagnostic modality has proven to
have higher specificity. (17) There is wide acceptance of the need to individualize application of
prophylactic anticoagulation in surgical patients at risk, (18) thus the risk categorization.
Previous studies have emphasized on compliance by surgery staff was a key factor, irrespective
of the protocol adopted by any institution. (8, 19) This study was aimed at assessing the current
practice pattern of DVT prophylaxis among orthopedic surgeons (at the National Orthopedic
Hospital, Enugu) and to evaluate the conformance of these practice patterns to the ACCP
guidelines. The study also aimed to determine the short term outcome of the patients postoperatively. This was defined in terms of developing clinically apparent signs of VTE while on
admission.
Patients and Methods
This was a prospective study done over a 12 month interval, from the 1st of January 2012 to the
31st of December 2012. All admitted patients who consented and who had major orthopedic
surgery in this period were included in this descriptive study. A proforma was employed to
obtain data including demographic data, diagnosis, procedure had, co-morbidities, ACCP-9 risk
category and DVT prophylaxis received. A hundred and thirty nine patients were recruited into
the study and followed throughout the duration of their hospital stay. The managing unit solely
determined if any and what DVT prophylactic regimen was employed in the management of
each patient. Patients were followed up until discharge and records of any adverse venous
thrombotic events were recorded where present.
Ethical approval was obtained from the hospital review board and all protocol used was in line
with the Helsinki declaration of 1979. Only patients who gave informed written consent were
recruited for the study.
Data analysis
Statistical analysis was done using the Statistical Package for Social Sciences (SPSS) 17.0
Illinois,Chicago. The Chi square test was done to evaluate the relationship for ordinal and
nominal variables, while the Kendall’s tau_b correlation coefficient (2 – tailed) was done for all
numerical variables, without assuming equal variance. The p values were assumed to be
significant for all values < 0.05.
Results
One hundred and thirty nine patients were recruited aged 17 to 78 years, median age of 41 years.
There were 89 (64%) males and 50 (36%) females. Thirty three patients (23.7%) had comorbidities, while 106 (76.3%) did not. DVT prophylaxis was administered in 64 (46%) of the
patients, 75 (54%) patients did not receive any DVT prophylaxis. The patients were categorized
into: very high risk; 11 patients (7.7%), high risk; 27 (18.9%), moderate risk; 71 (41.7%) and
low risk; 30 (21%). Figure 1a shows the distribution of the age and risk categories of the patients
in the 2 sexes. Patients who had co-morbidities received a longer duration of anti-coagulation as
shown in figure 1b. None of the patients in this group developed clinically obvious DVT or
pulmonary embolism while on admission.
In 60 (43.2%) of the patients, the use of anticoagulation was in conformance with American
college of chest physicians (ACCP-9) recommendations. However, 79 (56.8%) did not receive
their anticoagulants according the ACCP-9 guidelines. There were observed differences in
defaults in duration of anti-coagulation in 56 patients (70.9%) and in 23 patients (29.1%) anticoagulation therapy was completely omitted. The Chi square value for the conformance to the
ACCP-9 guideline was found to be 1.317 (p = 0.075). However, a positive correlation was found
between conformance to the ACCP-9 guidelines and patient’s age, 0.19 (p=0.007) as well as the
risk categorization, 0.335 (p=0.001).
The association between patients’ age, sex, risk categorization and presence of co-morbidities
and the duration of anti-coagulation are shown in Table 1. The duration of DVT prophylaxis as
well as its use was found to positively correlate with the age of the patients 0.296 (p=0.034). This
was also found to have an inverse relationship with presence of co-morbidities -0.42 (p=0.016).
The gender of the patients however did not have any association with the length of time DVT
prophylaxis was administered -0.046 (0.782). The risk categorization was observed to have a
positive association with the duration of prophylaxis 0.48 (0.001); the higher the risk category,
the longer the duration of anticoagulation given.
Table 1. Association between duration of administration of DVT prophylaxis and other
patient related factors in patients that received prophylaxis
Category
DVT
Prophylaxis
Correlation(Kendaull
tau_b)
Significance
Age
Yes (n=64)
0.131
0.184
Gender
Yes (n=64)
0.179
0.131
-0.227
0.055
0.234
0.037*
Presence
of
morbidities
Co- Yes (n=64)
Risk Categorization

Yes (n=64)
* Significant p value < 0.05
Figure 1a. Age distribution of the patients amongst the various risk categories and gender
Figure 1b. Presence of co-morbidites Vs the duration of DVT prophylaxis in the patients
Discussion
About a quarter of the patients in this study were categorized as high or very high risk and
majority of these patients received prophylaxis, though not in conformance with ACCP-9. Also
it was observed in this study that the older the patient, the more the tendency to conform to the
guideline. However, DVT prophylaxis was omitted in about 20% of the patients who actually
were qualified to receive it according to ACCP-9. The 2 trends above give the impression that
adequate DVT prophylaxis was practiced only for patients who were either older or who were
assessed to have a higher risk of DVT. The possible explanation is that managing surgeons tend
to utilize their knowledge of the risk factors in deciding DVT prophylaxis rather than individual
patient assessment and adherence to ACCP-9. This ascribed to the attention to caution and
patient-associated predisposition to thrombosis rather than conformance to standard risk
assessment in each case. The end result being that a significant number of patients were exposed
to the risk of VTE, as we found no evidence, however, of any formal risk assessment of
individual patients in their notes.
The results of this study demonstrates a significant underuse of DVT prophylaxis, with less than
half of the sample population receiving DVT prophylaxis in accordance with the guidelines laid
down by the ACCP in its 9th edition. This trend had been observed in previous studies carried out
in surgery patients (8) and thus indicates the need for further studies to assess the reasons given
by surgical staff for this sub-optimal trend. This is despite the availability of evidence based
guidelines for DVT prophylaxis in orthopedic practice spanning a wide spectrum of orthopedic
procedures. Several authors working in developed countries have reported a similar trend in their
practice, (20) though in Nigeria data on conformance to guidelines for DVT prophylaxis is
difficult to find. This may be explained by the lower incidence of DVT in the general population,
possibly owing to under-reporting or a lower genetic predisposition. (1, 18)This will be
supported by our observation that though majority of the patients were received sub-optimal
anticoagulation, none developed DVT or pulmonary embolism.
Among patients who received inadequate prophylaxis, there was an observed sub-optimal
duration of administration of anti-coagulating agents. Prophylactic agents used were found to
have been given for fewer days than recommended in the guidelines. This widespread trend may
be due to financial constraints as most of the patients make out-of-pocket purchase of their
prescription. There may also be a knowledge gap with regards to dosing protocol for DVT
prophylaxis and this may explain why erroneously shorter durations were employed. However, it
is noteworthy that from our study no harm was done to the patients involved in this study. This
cannot be completely ruled out due to the short duration of follow-up and lack of
ultrasonographic evidence of venous patency. (20, 21) The importance of duplex ultrasonography
for confirmation of suspected cases and possible screening cannot be over-emphasized as results
of previous studies show. (22) There may also be a need to create a separate, less intense anticoagulation regimen/protocol in areas where the incidences of thrombo-embolic diseases are
significantly lower. (6) Older patients and patients who were seen as having a greater risk of
DVT universally received a longer duration of prophylaxis, thus conforming to the ACCP
guidelines.
Workers in developed countries have listed the major problem as being due to an initial lack of
risk assessment rather than problems with the pharmacological prescriptions.(23) They have also
listed problems with poor prescription of mechanical methods like, foot pumps and graduated
elastic stockings, in their environment. Various studies have also advocated strategies to improve
the conformance to guidelines in DVT prophylaxis and have reported large increases in
compliance10. Poor prescription of mechanical methods is not a feature in Nigeria as most
hospitals lack these amenities. The absence of any documentation of a formal risk assessment
may have also contributed the under prescription observed.
CONCLUSION
Inadequate DVT prophylaxis remains a relevant feature in orthopedic practice in the African
context. Orthopedic surgical units were observed to use anti-coagulation in older patients with
higher risk of developing DVT, while some younger patients who needed to be anti-coagulated
were left unprotected. In majority of the patients who received anti-coagulation the duration of
therapy was observed to be sub-optimal. Measures to improve risk assessment habits and proper
prophylaxis may be necessary to reverse these trends. Also there may be need to develop a
different risk assessment profile and anti-thrombotic protocol suited for areas with lower
incidence of thromboembolic diseases in their general population.
Conflict of interest: Authors declare there was no conflict of interest
Source of funding: The research was funded by the authors
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