Deep venous thrombosis (DVT) is a big potential problem for many trauma patients, particularly those with orthopedic injuries. Patients at high risk are frequently given a prophylaxis regimen to take home after discharge while they are still at higher risk for clots. The particular choice of medication typically comes down to oral (warfarin or aspirin) vs injectable (low molecular weight heparin (LMWH)).
There is quite a bit of literature on patient compliance with their medication routines, or should I say noncompliance? The group at ShockTrauma in Baltimore evaluated how well orthopedic surgery patients adhered to their prescribed DVT prophylaxis schedule after discharge.
They conducted a randomized, prospective trial on all patients who underwent operative management of extremity or pelvic fractures. These patients were prescribed either oral low dose aspirin (81mg) or subcutaneous injections of LMWH (30mg bid). All completed a standardized 8-question tool to gauge their compliance with the medication regimen. Nicely, a power analysis was performed to identify the minimum number of patients needed to achieve statistical significance ( 126 total patients).
Here are the factoids:
Of 1450 potential patients undergoing operative fracture fixation, 329 were eligible for the study. All but 150 were excluded primarily due to no need for prophylaxis or inability to contact.
Overall adherence to the prophylaxis plan was fairly high, with 65% of patients having high adherence, 21% medium, and 20% low.
A quarter of the LMWH patients felt “hassled” by their regimen, while only 9% of the aspirin group did
LMWH prophylaxis was associated with low or medium adherence
Having to self-administer the prophylactic agent, being a male, and young was also associated with lower compliance
Bottom line: Interesting study. And unfortunately it suggests that our patients don’t always do what they are told, especially if they have to stick themselves with needles. So they may not be getting the prophylaxis we think they are. Furthermore, we’re not even sure if aspirin (or LMWH for that matter) make a difference in the incidence of death or major pulmonary embolism in these patients.
There are a lot of opportunities for mayhem in this study. A third of the enrolled patients were not even compliant with completing the survey. This is certainly a source of bias, and most likely suggests that the overall compliance rates would have been even lower if they had.
Keep in mind the risk factors for compliance (age, sex, drug route) when deciding how and what to provide for DVT prophylaxis. Your patient may not be doing what you assume they are!
Many surgeons and surgical subspecialists are nervous about operating on people who are taking anticoagulants. This seems obvious when it involves patients on therapeutic anticoagulation. But it is much less clear when we are talking about lower prophylactic doses.
Spine surgeons are especially reluctant when they are operating around the spinal cord. Yet patients with spine injury are generally at the highest risk for developing venous thromboembolic (VTE) complications like deep venous thrombosis (DVT) or pulmonary embolism (PE). Is this concern warranted?
Surgeons at the Presley Trauma Center in Memphis examined this issue by performing a retrospective review of six years worth of patients who underwent spine stabilization surgery. They specifically looked at administration of any kind of preop prophylactic anticoagulant, and the most feared complications of bleeding complications and postop VTE.
Here are the factoids:
A total of 705 patients were reviewed, with roughly half receiving at least one preop prophylactic dose and the other half receiving none
There were 447 C-spine, 231 T-spine, and 132 L-spine operations, performed an average of 4 days after admission
Overall, bleeding complications occurred in 2.6% and VTE in 2.8%
Patients with VTE were more severely injured (ISS 27 vs 18)
Those who received at least half of their possible prophylactic doses had a significantly lower PE rate (0.4% vs 2.2%) but no significant difference in DVT or bleeding complications
Bottom line: So what to make of this? It’s a relatively small, retrospective study, and there is no power analysis. Furthermore, this hospital does not perform routine DVT screening, so that component of VTE may be underestimated, rendering the conclusions invalid.
However, the information on bleeding complications is more interesting, since this is much more reliably diagnosed using an eyeball check under the dressing. So maybe we (meaning our neurosurgeons and orthopedic spine surgeons) need to worry less about preop prophylactic VTE drugs. But we still need better research about whether any of this actually makes a dent in VTE and mortality from PE. To be continued.
Reference: Early chemoprophylaxis is associated with decreased venous thromboembolism risk without concomitant increase in intraspinal hematoma expansion after traumatic spinal cord injury. J Trauma 83(6):1108-1113, 2017.
Spine trauma is one of the high-risk indicators for deep venous thrombosis (DVT). Unfortunately, there is a great deal of variability in the start time for chemical prophylaxis for this injury, especially after the patient has undergone surgery. In part, this is due to a lack of good literature and guidelines, and in part due to the preferences of the spine surgeons who operate on these patients.
A group at the University of Arizona in Tucson performed a large database review (looks like National Trauma Databank, although they don’t say in the abstract) looking at “early” vs “late” administration of prophylaxis after surgery in these patients. The spine injury was the predominant one, with all other systems having an abbreviated injury score (AIS) < 3. They matched two years worth of patients for demographics, initial vitals, type of operative intervention, and type of heparin to assess the impact of prophylaxis timing.
Here are the factoids:
Nearly 40,000 patient records were reviewed, and over 9,500 met the spine injury criteria with operation and prophylaxis. A total of 3,556 could be matched for analysis.
These patients were split in half for matching, late (>48 hrs) versus early (<48 hrs)
DVT rate was significantly lowe in the early prophylaxis group (2% vs 11%)
PE rate and mortality were the same between groups
Return to OR and blood transfusion rates were identical (1% and 1-2 units)
Bottom line: Once again, we see that “early” prophylaxis for DVT is probably desirable and mostly harmless, even after a spine operation. Many surgeons still have an irrational fear of giving heparin products in patients who have some risk of bleeding. The body of literature that supports early use just keeps growing. One observation, though: as in most other studies, pretty much whatever we do for DVT has a negligible impact on PE and mortality. We can only treat the clots, but not their major aftermath.
Reference: Optimal timing of initiation of thromboprophylaxis in spinal trauma after operative intervention: – propensity-matched analysis. JACS 225(4S1):S59-S69, 2017.
Venous thromboembolism (VTE) is an ongoing problem for trauma professionals. Most trauma programs have settled on their own flavor of screening, prophylaxis, and treatment once the problem actually surfaces in a patient. Most prophylaxis centers around a combination of mechanical (leg squeezers) and chemical (some type of heparin) management.
Aspirin has been used for prophylaxis for elective orthopedic surgery, and occasionally in trauma patients managed by orthopedic surgeons for years. Existing literature supporting this has been sparse and unconvincing. But since VTE involves platelets as part of the process, why not have another look?
A recently published paper from Scripps in San Diego looked tried to gauge the effect of aspirin on trauma patients where taking it before they were injured. Novel idea. Can the findings be useful? The authors performed a retrospective, case-controlled study of patients who developed post-traumatic deep venous thrombosis (DVT). The patients were matched for 7 covariates, and the authors looked at an additional 26 risk factors. Those taking aspirin pre-injury were compared with those who were not.
Here are the factoids:
172 cases were identified over the 5 ½ year study, and 62 (36%) were excluded because a matched control could not be found
7% of the remaining110
patients were taking aspirin (why?)
13% of controls were taking aspirin
7% were taking warfarin, and 4% were taking clopidogrel
The mean age was 52, ISS was 13-14, and hospital stay was 7-10 days (!)
Multivariate analysis showed a significant protective effect from DVT with a risk ratio of 0.17 (!!)
But this effect was found only when used in conjunction with heparin prophylaxis after admission
Bottom line: Interesting findings. What does it mean? First, this is a very small retrospective study. It was conducted over 5+ years, so changes in VTE screening and prophylaxis may have occurred at this hospital. But even so, the finding were compelling. The biggest problem is that we can’t expect people to predict that they will need to start taking aspirin. But the study does raise the interesting question of whether it might be helpful to start taking it as soon as the patient arrives at the hospital. This is one of those thought provoking studies that should prompt someone (hint hint) to design a nice prospective study to see if this ultra-cheap drug might help us bring down our VTE rates even more.
Reference: Aspirin as added prophylaxis for deep vein thrombosis in trauma: A retrospective case-control study. J Trauma 80(4):625-630, 2016.
As with adults a decade ago, the incidence of venous thromboembolism (VTE) in children is now on the rise. Whereas adult VTE occurs in more than 20% of adult trauma patients without appropriate prophylaxis, it is only about 1% in kids, but increasing. There was a big push in the early 2000′s to develop screening criteria and appropriate methods to prevent VTE. But since the incidence in children was so low, there was no impetus to do the same for children.
The group at OHSU in Portland worked with a number of other US trauma centers, and created some logistic regression equations based on a large dataset from the NTDB. The authors developed and tested 5 different models, each more complex than the last. They ultimately selected a model that provided the best fit with the fewest number of variables.
The tool consists of a list of risk factors, each with an assigned point value. The total point value is then identified on a chart of the regression equation, which shows the risk of VTE in percent.
Here are the factors:
Note that the highest risk factors are age >= 13, ICU admission, and major surgery.
And here is the regression chart:
Bottom line: This is a nice tool, and it’s time for some clinical validation. So now all we have to do is figure out how much risk is too much, and determine which prophylactic tools to use at what level. The key to making this clinically usable is to have a readily available “VTE Risk Calculator” available at your fingertips to do the grunt work. Hmm, maybe I’ll chat with the authors and help develop one!
Reference: A Clinical Tool for the Prediction of Venous Thromboembolism in Pediatric Trauma Patients. JAMA Surg 151(1):50-57, 2016.
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