Category Archives: Complications

Complications

Fat Embolism vs Fat Embolism Syndrome

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It’s fat embolism week! I’ll cover this uncommon, yet very important clinical condition in my next four posts.

Fat embolism syndrome (FES) is one of those clinical problems that trauma professionals read about during their training, then rarely ever see. Although the clinical manifestations are frequently mild, they can progress rapidly and become life-threatening. Over the next five days, I’ll try to  help you better understand this condition, and provide details on diagnosis and treatment.

Fat embolism syndrome (FES) is a constellation of findings that arise from a single, unified cause: the escape of fat globules into the circulation (fat embolism). The ultimate resting places of those globules determine the specific manifestations of FES seen in clinical practice. When it occurs, it typically becomes apparent 24 to 72 hours after injury.

Simple fat embolism occurs to some degree any time tissues containing fat are manipulated or injured. It has been demonstrated during plastic surgical injections for cosmetic purposes and lipid infusions. It is more frequently seen with orthopedic injuries, especially those involving the femurs and pelvis. And it makes sense that the more fractures that are present, the more likely fat embolism will occur. Embolism is also known to occur when performing orthopedic procedures, particularly those involving the marrow cavity (intramedullary nailing), but has also been reported in total knee and hip procedures.

Fat embolism syndrome has a generally reported incidence of 1 – 10%, although I believe that is on the high side. I see a case every 3 – 4 years in a predominantly blunt, fracture-laden practice. Fat embolism without symptoms occurs much more frequently. A study from 1995 using transesophageal echo found evidence of emboli in 90% of patients with long bone fractures.

But how do these fat globules get into the circulation and produce such chaos? We know that they can be mechanically pushed into small venules when tissues containing fat cells or bone marrow are injured. In bone, there are numerous small venules located throughout that are anchored to it. When the bone is fractured, these venules tear and are held open so yellow (fatty) marrow can be pushed into them.

If enough emboli enter the blood stream, they may accumulate in the end vessels of tissues and block flow. Although this is a simple and appealing explanation, it may not be the full story. If the emboli primarily occur during and after injury, why does it take several days for the full-blown syndrome to develop?

A likely explanation is that the fat globules begin to degrade while in the circulatory system. Breakdown into free fatty acids results in the release of a cascade of cytokines and other mediators. The inflammatory response around the end vessels create the gross pathology that we associate with fat embolism syndrome.

In the next post, clinical manifestations of fat embolism syndrome.

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Complications, Resuscitation

Are Transfusing Too Much Blood During The MTP?

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The activation of the massive transfusion protocol (MTP) for hypotension is commonplace. The MTP provides rapid access to large volumes of blood products with a simple order. Trauma centers each design their own protocol, which usually includes four to six units of PRBC per MTP “pack.”

This rapid delivery system, coupled with rapid infusion systems, allows the delivery of large volumes of blood and other blood products very quickly. But could it be that this system is too slick, and we are a bit too zealous, and could even possibly transfuse too much blood?

The trauma group at Cedars-Sinai in Los Angeles retrospectively reviewed their own experience via registry data with their MTP over a 2.5 year period for evidence of overtransfusion. All patients who received blood via the MTP were included. Patients who had a continuous MTP > 24 hours long, those who died within 24 hours, and those who had a missing post-resuscitation hemoglobin (Hgb) were excluded.

The authors arbitrarily defined overtransfusion as a Hgb > 11 at 24 hours. They also compared the Hgb at the end of the MTP and upon discharge with this threshold. They chose this Hgb value because it allows for some clinical uncertainty in interpreting the various endpoints to resuscitation.

Here are the factoids:

  • 240 patients underwent MTP during the study period, but 100 were excluded using the criteria above, leaving 140 study patients
  • Average injury severity was high (24) and 38% suffered penetrating injury
  • Median admission Hgb was 12.6
  • At the conclusion of the MTP, 71% were overtransfused using the study definition, 44% met criteria 24 hours after admission, and 30% did at time of discharge
  • Overtransfused patients were more likely to have a penetrating mechanism, lower initial base excess, and lower ISS (median 19)

The authors concluded that overtransfusion is more common than we think. This may lead to overutilization of blood products, which has become much more problematic during the COVID epidemic. They recommend that trauma centers track this metric and consider it as a quality of care measurement.

Bottom line: This is a nicely crafted and well-written study. It asks a simple question and answers it with a clear design and analysis. The authors critique their own work, offering a comprehensive list of limitations and a solid rationale for their assumptions and conclusions. They also offer a good explanation for their choice of Hgb threshold in defining overtransfusion.

I agree that overtranfusion truly does occur, and I have seen it many times first-hand. The most common reason is the lack of well-defined and reliable resuscitation endpoints. How do we know when to stop? What should we use? Blood pressure? Base excess? TEG or ROTEM values? There are many other possibilities, but none seem reliable enough to use in every patient. 

Patients with penetrating injury proceeding quickly to OR more commonly experience overtransfusion. This may be due to the reflexive administration of everything in each cooler and the sheer speed with which our rapid infuser technology can deliver products. The more product in the cooler, the more that is given, which may lead to the overtranfused condition. 

The authors suggest reviewing the makeup of the individual MTP packs, and this makes sense. Are there too many in it? This could be a contributing factor to overtransfusion. It might be an interesting exercise to do a quick registry review at your own center to obtain a count of the number of MTP patients with a final Hgb > 11. If you find that your numbers are high, consider reducing the number of red cell packs in the cooler to just four. But if you already only include four, don’t reduce it any further. And in any case, critically review the clinical indicators your  surgeons use to decide to end the MTP to see if, as a group, they can settle on one to use consistently. 

Reference: Overtransfusion of packed red blood cells during massive transfusion activation: a potential quality metric for trauma resuscitation. Trauma Surg Acute Care Open 7:e000896., July 26 2022.

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Complications

The Impact Of NSAIDs On Fracture Healing

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In my last post I discussed some of the basic effects of NSAIDs on bone healing. Now let’s see if theory applies to practice.

In 2003, several papers brought to light possible interactions between these drugs and fracture healing. Specifically, there were questions about these drugs interfering with the healing process and of increasing the number of delayed unions or nonunions. But once again, how convincing were these papers, really?

It would seem to make sense that NSAIDs could interfere with bone healing. The healing process relies heavily on the regulation of osteoblast and osteoclast function, which itself is regulated by prostaglandins. Since prostaglandins are synthesized by the COX enzymes, COX inhibitors like the NSAIDs should have the potential to impair this process. Indeed, animal studies in rats and rabbits seem to bear this out.

But as we have seen before, good animal studies don’t always translate well into human experience. Although a study from 2005 suggested that NSAID administration in older patients within 90 days of injury had a higher incidence of fracture nonunion, the study design was not a very good one. It was equally likely that patients who required these drugs in this age group may have been at higher risk for nonunion in the first place.

A meta-analysis of human studies was performed in 2011. Out of 558 potential studies, only 5 met criteria review. (This is yet another reminder of the sheer amount of sub-par research out there.) The authors found that short-term use (< 14 days) of normal dose NSAIDS was not associated with non-union. High doses of ketorolac (> 120mg/day) and diclofenac sodium (> 300mg total) did have an association. But remember, this does not show causation. There are many other factors that can impede healing (smoking, diabetes, etc).

A study from 2016 examined the effect of ketorolac administration on fracture healing in patients undergoing repairs of femoral and tibial fractures. It did not find an association between non-union and ketorolac, but did find one with smoking. Unfortunately, the study was small (85 patients given ketorolac, 243 controls without it). It probably does not have the statistical power to detect any difference with the NSAID. A power analysis was not provided in the methods section.

Bottom line: Once again, the animal data is clear and the human data less so. Although there are theoretical concerns about NSAID use and fracture healing, there is still not enough solid risk:benefit information to abandon short-term NSAID use in patients who really need them. NSAIDs can and should be prescribed in patients with short-term needs and simple fractures, and consider COX-1 specific drugs like ketorolac while your patient is in the hospital. And we do have some evidence that high-dose NSAIDs may have some impact, so stick to the usual doses for just as long as they are needed for pain management.

References:

  1. Effects of nonsteroidal anti-inflammatory drugs on bone formation and soft-tissue healing. J AM Acad Orthop Surg 12:139-43, 2004.
  2. Effect of COX-2 on fracture-healing in the rat femur. J Bone Joint Surg Am 86:116-123, 2004.
  3. Effects of perioperative anti-inflammatory and immunomodulating therapy on surgical wound healing. Pharmacotherapy 25:1566-1591, 2005.
  4. Pharmacological agents and impairment of fracture healing: what is the evidence? Injury 39:384-394, 2008.
  5. High dose nonsteroidal anti-inflammatory drugs compromise spinal fusion. Can J Anaesth 52:506-512, 2005.
  6. Nonsteroidal Anti-Inflammatory Drugs and Bone-Healing: A Systematic Review of Research Quality. JBJS Rev 4(3), 2016.
  7. High-dose ketorolac affects adult spinal fusion. Spine 36(7):E461-E468, 2011.
  8. Ketorolac administered in the recovery room for acute pain management does not affect healing rates of femoral and tibial fractures. J Orthop Trauma 30(9):479-482, 2016.
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Complications

NSAIDs And Bone Healing: How Do They Impact It?

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The arguments about whether NSAID administration has any effect on bone healing continues to be argued by our orthopedic and spine surgery colleagues. In the early days of research in this area (about 20 years ago) there were concerns in animal models that there might be a problem. Apparently lots of rats and bunnies were suffering from fractures in those days.

But physiologically, how could NSAIDS do this? Here’s a simplified diagram of how the bone healing process works.

First, an acute injury occurs and macrophages and other cells move into the area to start the inflammatory process. COX-2 receptors are highly expressed on these cells, resulting in an increase in prostaglandin E2 (PGE2) production.

PGE2 then promotes proliferation of stem cells that differentiate into osteoblasts, which in turn begin forming bone to repair the injury.  In theory, if PGE2 is reduced in the healing area there is the possibility that bone formation may be impaired, leading to non- or malunion or refracturing.

Administration of NSAIDs can block COX-1 and COX-2 receptors throughout the body. This serves to decrease prostaglandin production and hence reduces inflammation and pain. Doesn’t it follow that giving these drugs should be bad for bone formation in patients with fractures?

Not so fast! There are a number problems with this argument. First, not all NSAIDs are created alike. Here is a chart that shows where the primary focus of COX inhibition is with some common NSAIDs.

Note how the common over-the-counter drugs affect both COX-1 and COX-2, yet there are some that are more selective. So the choice of drug may be relevant.

And we can’t assume that an in vitro effect in a Petri dish of cells actually carries over into the in vivo world. Many researchers rely initially on animal models to study drug effects in vivo. Predictions based on studies of rats and bunnies frequently do not pan out in humans.

We are left with only a theory based on an understanding of the basic mechanism of bone healing. Tune in to my next post where I discuss the research that’s been done in this field and whether it actually translates into human bone healing or not.

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Complications

The Tertiary Survey For Trauma: Residents vs APPs

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This is the final installment of my series on the tertiary survey for trauma.  For years, this exam was performed by trauma surgeons or residents. However, over the years advanced practice providers (APPs) such as physician assistants and nurse practitioners have become more common in trauma. It is now commonplace for these providers to participate on the trauma service, perform procedures, and document examinations such as the tertiary survey.

But until now, no one has compared the accuracy of this exam when performed by a physician vs an APP. One would assume that the results should be the same, but as we’ve seen time and time again, common sense doesn’t always pan out. A group at the Royal Brisbane and Women’s Hospital in Queensland, Australia tried to answer this question using a retrospective review of their experience.

This busy trauma center admits about 2,250 patients per year, and began to employ clinical nurse consultants on the trauma service nearly ten years ago. Since there was no formal trauma curriculum for these nurses, they were required to complete the Trauma Nursing Core Curriculum (TNCC) or an equivalent prior to hire. The nurses were supervised by one of the trauma / emergency physicians.

For this study, 165 patients who underwent a tertiary survey by both an emergency medicine resident and a trauma nurse over a three year period were reviewed. The surveys were typically performed within 24 hours of admission to a ward bed or 24 hours before transfer from ICU to the ward. Typically, the resident and nurse tertiary surveys were performed within 30 minutes of each other to avoid any effects from injury progression.

All missed injuries were graded for severity by an attending physician using the Clavien-Dindo system. Here’s what it looks like:

And here are the factoids:

  • A total of 3,065 patients had a tertiary survey performed during the study period, but only 165 had it performed by both a resident and an APP
  • Based on their surveys, additional investigations were ordered in 35 patients, 14 by the trauma nurse, 11 by the resident, and 10 by both
  • Eight of 14 studies ordered by the nurse identified a missed injury, two of 11 studies ordered by the resident did, and two were identified in the studies ordered by both
  • Of the 12 identified missed injuries, the Clavien-Dindo (C-D) score was 0 in one, I in ten patients, and III (required surgery) in one
  • The nurses identified a higher number of missed injuries (10 of 24) than the residents (4 of 21) without significantly increasing the number of tests ordered

The authors concluded that performance of the nurses was similar to that of the house officers.

Bottom line: Maybe the authors were trying to be gentle on their residents. But it looks to me like the trauma nurses did a much better job of finding occult injuries. I wish the authors had broken down the C-D scores to see which group identified the score III patient.

To be fair, this study has some significant limitations. Out of more than 3,000 eligible patients, only 165 had a dual tertiary survey. So the sample may not be representative. But the results were impressive enough that I would speculate the results of a larger group may be similar.

So I think it is safe to assume that APPs (specifically nurse practitioners, but this can probably be generalized to physician assistants as well) can do a tertiary survey just as well as a resident. And possibly better!

Reference: Trauma tertiary survey: trauma service medical officers and trauma nurses detect similar rates of missed injuries. J Trauma Nursing 28(3):166-172, 2021.

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