Tag Archives: VTE

Complications

My VTE Rate Is Really Low! Are You So Sure…?

I’ve seen hospitals (and trauma programs) boast that their venous thromboembolism (VTE) rate is very low. The numbers they report to state agencies or TQIP may be fractions of a percent. But is it real?

The main problem is a phenomenon called surveillance bias. This occurs when a condition appears more common in one group because that group is scrutinized more closely, is tested more often, or is screened more aggressively.

For those of you who are old enough to have read House of God by Samuel Shem (1978), there were 13 laws. Law 10 was: if you don’t take a temperature, you can’t find a fever.  Similarly, if you rely solely on clinical signs and symptoms to diagnose VTE, you won’t detect it in most cases.

But how big is the difference, anyway? Several recent papers compared them, and of course, the numbers vary widely:

  1. In a prospective, randomized study of 3,236 patients, surveilled patients had 12.5% below-knee and 1.9% above-knee VTE, vs 0.8% and 0.8% in unscreened patients. The pulmonary embolism (PE) rate was 0.1% among screened patients vs 0.9% in the unscreened, possibly because screened patients were more likely to receive treatment
  2. In another prospective study, patients screened as high-risk using Greenfield criteria were studied based on their screening status. Although not randomly assigned, 11.6% of 259 screened patients had VTE, compared with 2.1% of 143 patients who were not screened. PE rate was 1.9% in screened patients vs 7.0% in unscreened patients.
  3. Over 5,000 retrospectively reviewed patients were compared for VTE based on whether they were screened or not (not randomized). A total of 7% of screened patients were found to have VTE, and only 0.06% of unscreened patients had it.

But I think you get the idea. If you look for it, you will find it. If you are not looking, you may be missing a clinically significant finding that could result in significant complications.

Bottom line: trauma patients, and especially the more severely injured ones, are at significant risk for developing VTE. The data show us that looking for clinical signs and symptoms is not very accurate. Reference 4 shows that even one of the common risk assessment tools, the Risk Assessment Profile (RAP), is not very accurate in these patients. Don’t be complacent just because your unscreened VTE rates look good. If you don’t look, you won’t find it. If you don’t screen, the studies listed above tell us that you should probably multiply your unscreened rate by about 5x to get a glimpse of what your real number is. I strongly suggest you incorporate VTE screening into your VTE practice guidelines. 

References:

  1. Trauma patients at risk for venous thromboembolism who undergo routine duplex ultrasound screening experience fewer pulmonary emboli: A prospective randomized trial. J Trauma Acute Care Surg. 2021 May 1;90(5):787-796. doi: 10.1097/TA.0000000000003104. PMID: 33560104.
  2. Surveillance and Early Management of Deep Vein Thrombosis Decreases Rate of Pulmonary Embolism in High-Risk Trauma Patients. J Am Coll Surg. 2016 Jan;222(1):65-72. doi: 10.1016/j.jamcollsurg.2015.10.014. Epub 2015 Nov 4. PMID: 26616034.
  3. The Utility of Lower Extremity Screening Duplex for the Detection of Deep Vein Thrombosis in Trauma. J Surg Res. 2022 Jan;269:151-157. doi: 10.1016/j.jss.2021.08.010. Epub 2021 Sep 23. PMID: 34563841.
  4. The Risk Assessment Profile is suboptimal for guiding duplex ultrasound surveillance in trauma patients. Surg Pract Sci. 2022 Sep 6;11:100127. doi: 10.1016/j.sipas.2022.100127. PMID: 39845166; PMCID: PMC11750042.
Pelvis

Pelvic Fracture Intervention And Venous Thromboembolism Risk

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Earlier this year, I wrote a series of posts on the two commonly used pelvic fracture interventions: preperitoneal packing (PPP) and angioembolization (AE). To sum up, both are equally effective in controlling hemorrhage, but the hospital costs for patients undergoing angioembolization are significantly less. This is probably because there is no need to perform repeated operations to insert and remove the preperitoneal packs when angiography is used.

But what about venous thromboembolism risk? Patients with pelvic fractures are already at high risk for it. Couldn’t the increase in pressure on the pelvic veins or the use of thrombogenic materials increase the risk? Authors from several well-known trauma centers collaborated to re-analyze data from the CLOTT study. This is another cute acronym for an extensive study, the Consortium of Leaders in the Study of Traumatic Thromboembolism. It looked at the incidence and risk factors for VTE in trauma patients. This analysis focused on VTE risk in patients with pelvic fractures, comparing those undergoing one of the two interventions with those who had neither.

Here are the factoids:

  • The original data were derived from a 17-center study conducted from 2018-2020; this study only included 1,387 patients who had pelvic fractures (as well as other injuries).
  • The primary outcome was the development of VTE during the hospitalization. DVT was detected using duplex ultrasound, and PE was detected by CT angiography. If pulmonary clots were seen without concomitant DVT, they were not considered to be of embolic origin.
  • For all comers, the overall incidence of VTE was 5.6%
  • Breaking them down by type, there were 2.7% PE, 2.7% DVT, and 1.9% pelvic thrombi (some patients had more than one event)
  • Chemical prophylaxis appeared to be very effective. If started within 24 hours, the incidence was 2.9% vs. 8.4%* if started later.
  • Missed doses did not appear to increase the incidence of VTE (about 5% for both groups)
  • Patients with PPP had a 9% incidence of VTE, pelvic angioembolization had 2.6%, and patients with ORIF had 16%. The incidence was 5.7% if no interventions at all were performed and 16% if more than one occurred.

Bottom line: There are a lot of tidbits in this paper. Most importantly, the use of PPP or AA does not significantly increase VTE risk. Interestingly, ORIF of the pelvis increases it. It’s not clear whether this is due to the procedure itself or is just a surrogate for the severity of pelvic injury. Multivariate analysis suggests that this is not a significant risk factor.

The finding that early chemoprophylaxis reduced VTE incidence to only 3% is very interesting. All too often, prophylaxis is delayed due to solid organ or head injuries. If it can be started safely in such patients, it should be to reduce the occurrence of this complication. One of the banes of management of major trauma is the potential need for repeated surgical procedures, which leads to a phenomenon known as “prophylaxis interruptus.” Thankfully, this study did not find that this increased VTE risk, although it did not stratify by how many doses were missed.

So put your mind at ease about increasing the risk of VTE risk by using procedures to decrease bleeding through mechanical means. But do remember to begin chemoprophylaxis soon and you safely can.

Reference: Does preperitoneal packing increase venous thromboembolism risk among trauma patients? A prospective multicenter analysis across 17 level I trauma centers. Journal of Trauma and Acute Care Surgery 97(5):p 791-798, November 2024.

Abstracts

Best Of EAST 2024 #8: Whole Blood And VTE

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The pendulum has swung from the use of whole blood in the early 20th century, to component therapy in the 1960s, and now a gradual move toward incorporating whole blood again. More and more papers are being published, and many trauma centers are looking for ways to integrate whole blood into their massive transfusion protocols.

Much of the literature has been dedicated to safety and effectiveness, but little has examined thrombotic complications from its use.  The trauma group at the University of Texas in Houston performed what looks to be a retrospective review of whole blood usage at two Level I trauma centers. Adult patients receiving at least one emergency-release whole blood unit were compared with those receiving only component therapy. They looked at the incidence of venous thromboembolic (VTE) complications such as pulmonary embolism (PE) or deep venous thrombosis (DVT).

Here are the factoids:

  • Nearly 3,500 patients were enrolled and were fairly evenly split between whole blood and component therapy only
  • Whole blood patients were slightly younger, were much more likely to have penetrating injury, and had significantly higher ISS (26 vs 19)
  • The whole blood patients were also significantly more likely to receive TXA, VTE chemoprophylaxis within 48 hours (86% vs. 79%) and lower 30-day survival (74% vs 84%)
  • Crude incidence of VTE was similar (7% whole blood vs. 9% component), but logistic regression “revealed that whole blood was protective of VTE,” while red cell transfusion and TXA increased VTE risk
  • Each unit of red cells increased VTE risk by 3%

The authors concluded that whole blood was associated with a 30% reduction in VTE, and TX was associated with a 2.5x increase in risk. They cautioned against the use of TXA in the setting of whole-blood resuscitation.

Bottom line: A lot is going on here. First, this is a retrospective study, which limits the number of variables that can be collected reliably. It also makes it much more difficult to perform regression analysis because there are many other possible variables to control for than just the ones collected. 

Next, as quoted in bullet point 4 above, this study can’t show that whole blood was protective, only that it was (maybe) associated with decreased VTE when the variables they collected were controlled. 

Most of the confidence intervals for the “significant” results were very close to the 1.0 line. This leaves the possibility that the result could easily be changed by adding other pertinent variables not included in the data. The only impressive one was the association of TXA exposure and VTE. I think this demands further work.

The authors need to answer several questions in their presentation to help explain the results:

  • Was there any relationship between the number of units of packed cells given and the likelihood of VTE?
  • Similarly, was there a relationship between the number of units of whole blood and possible “protection” from VTE?
  • Did you examine other physiologic or anatomic variables and their relationship with VTE? Specific ones that come to mind are shock, long bone or spine fractures, and TBI. These are some of the variables that need to be included in the regression model to improve it.

Overall, this is an interesting abstract that makes one think. But it either needs some good explanations during the presentation or additional data analysis to make it even more interesting.

Reference: Does whole blood resuscitation increase risk for venous thromboembolism in trauma patients? A comparison of component therapy vs whole blood in 3468 patients. EAST 2024, Podium paper 33.

Abstracts

Best of EAST 2024 #3: VTE Prophylaxis For Pediatric Trauma

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Venous thromboembolism (VTE) after trauma in adults has generated a considerable body of literature for guidance. However, there is much less information available regarding pediatric trauma. High-risk criteria for pediatric VTE after trauma have recently been released.

These criteria have not yet been evaluated prospectively or coupled with the administration of chemoprophylaxis. The Medical College of Wisconsin trauma group organized a prospective, multi-institutional study involving eight pediatric trauma centers. They studied VTE events within 30 days and bleeding complications. The children were stratified into three groups: no prophylaxis, early prophylaxis (within 24 hours), and late prophylaxis.

Here are the factoids:

  • A total of 460 patients were enrolled during a three-year period
  • The number of VTE events was very low at 25 (5.4%)
  • Patients who developed VTE had a median of 4 of the high-risk criteria, most commonly ICU stay>48 hours and TBI.
  • Half of patients received prophylaxis
  • VTE occurred in 1.6% receiving an early dose and 6.7% with late dosing
  • There were no bleeding complications

The authors concluded that prophylaxis in children at high risk for VTE was safe, but they could not demonstrate any risk reduction for those who had received chemoprophylaxis compared to those who had not.

Bottom line: This is another study that was cursed by low numbers. See the breakdown chart below:

There is a trend toward higher VTE in children receiving prophylaxis late or never. However, the number of subjects is far too low to detect significance. The good news is that there were no bleeding events in this modest sample of 257 patients. 

So what next? The authors state that “further subgroup analysis is ongoing to refine the high-risk criteria.” Good luck with that because subgrouping will deplete the numbers even further.

There are several things the authors could do to improve this work:

  • Get more subjects! Increase the number of centers participating, and consider sending it through the EAST Multicenter Trial process.
  • Streamline the list of high-risk criteria. There are quite a few of them. Try to focus on the most obvious ones and make sure each one has clear definitions. And set a threshold of how many must be present to trigger chemoprophylaxis.
  • Define the pediatric patient precisely. As children approach puberty, they behave more like adults as it pertains to VTE. State an explicit age cutoff.

This presentation should be a springboard to soliciting help from other pediatric trauma centers so this group can return to this meeting with compelling information.

Reference: The No Clot VTE study in high-risk pediatric trauma patients. EAST 2024 Podium paper #6.

Complications, Device

Should I Apply Compression Devices To Patients With DVT?

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Everyone knows that venous thromboembolism (VTE) is a potential problem in hospitalized patients, and especially so in trauma patients. Several groups of them are at higher risk by virtue of the particular injuries they have sustained and the activity restriction caused.

Nearly every trauma program uses some form of screening and prophylaxis in an attempt to reduce the occurrence of this problem, which can result in deep venous thrombosis (DVT) and/or pulmonary embolism (PE). Screening looks at patient factors such as age, obesity, and previous VTE, as well as injury risk factors like spine and pelvic fractures and decreased mobility.

Based on the screening protocol, prophylaxis may be prescribed depending upon the level of VTE risk, which is then balanced with bleeding risk from the brain, solid organ, or other injuries. The choices we have are primarily mechanical vs chemical and consist of compression devices (sequential or not) and various heparins.

But an age-old question continues to resurface: if a patient breaks through their prophylaxis and develops DVT, is it safe to apply compression devices to the extremity?

There has always been the fear that doing things that increase flow in the affected extremity may cause clots to dislodge and ultimately cause a PE. Seems logical, right? But we know that often, our common sense about things is completely wrong.  Couldn’t just moving around cause pieces to break off? A meta-analysis of 13 studies published in 2015 showed that early ambulation was not associated with a higher incidence of new PE. Furthermore, patients who suffered from pain in the affected extremity noted significant improvements with early ambulation.

If ambulation makes the pain better, could the veins be recanalizing more quickly? Another study examined a small group of 72 people with DVT receiving anticoagulants, half of whom were prescribed exercise and compression stockings and the other half stockings only. There was a huge amount of variability in the rates of recanalization, but ultimately, there were no significant differences with or without exercise.

So just lying in bed is not good, and exercise/ambulation may actually make people feel better. But interestingly, bedrest alone does not appear to increase the likelihood of PE! It does decrease the risk of developing problems other than the VTE, like pulmonary complications.

But what about compression devices? Common sense would say that you are intermittently  increasing pressures in the leg veins, which could dislodge any loose clots and send them flying to the lungs, right?

Unfortunately, I couldn’t find a paper from anyone who had the courage to try this. Or perhaps no institutional review board (IRB) would approve it. But the key fact is that every compression device manufacturer includes existing DVT as a contraindication in their product documentation. They don’t have any literature either, so I assume it’s an attempt to limit litigation, just in case.

Bottom line: Walking provides at least as much muscle compression as compression devices. But the simple truth is that we have no solid research that either supports or condemns the use of active compression devices in patients with known DVT. And we probably won’t, ever.

Compression stockings seem to be safe, but they really don’t do much. They are white, but don’t do much more than contribute to hospital clothing fashion. Since the manufacturers define existing DVT as a contraindication, application of their product would be considered an off-label use. So it looks like we cannot in good faith use these devices in patients with diagnosed DVT.

References:

  • Bed Rest versus Early Ambulation with Standard Anticoagulation in The Management of Deep Vein Thrombosis: A Meta-Analysis. PLOS One , April 10, 2015, https://doi.org/10.1371/journal.pone.0121388
  • Bed Rest or Ambulation in the Initial Treatment of Patients With Acute Deep Vein Thrombosis or Pulmonary Embolism: Findings From the RIETE Registry. Chest 127(5):1631-1636, 2005.
  • Does supervised exercise after deep venous thrombosis improve recanalization of occluded vein segments? A randomized study. J Thrombosis Thrombolysis 23:25-30, 2006.