All posts by The Trauma Pro

General

Fatigue: Sleep Deprivation Changes The Way We Make Risky Decisions

Leave a comment

I’m expanding my series dealing with the issues surrounding lack of sleep. As you all know, trauma professionals are expected to perform even if they have not had adequate sleep. This can occur with certain shift schedules, long periods of work, or due to call schedules and duration of call. What do we really know about the effects of sleep deprivation on us?

For the next few weeks I’ll be writing about the effects of fatigue on trauma professionals, including prehospital providers, residents, surgeons, and nurses. And I’ll finish up with some new research on the effects on our patients.

In this post, we’ll talk about decision making. Neuroscientists at Duke looked at how we approach risky decisions when we are sleep deprived. A total of 29 adults (average age 22) were studied. They were not allowed to use tobacco, alcohol and most medications prior to sleep deprivation, which lasted for 24 hours. They were given a risky decision making task (a controlled form of gambling), and two other tests while in a functional MRI unit to watch areas of brain activation.

The researchers found that, when well rested, the subjects had a bias toward avoiding loss in the gambling test. After a single night of sleep deprivation, this shifted to pursuing gain. The MRI also showed an increased activity in the reward anticipation parts of the brain. Overall decreased vigilance was noted, but this did not correlate with the shift away from risk avoidance.

Bottom line: Sleep deprivation appears to create an optimism bias. Fatigued individuals act like positive outcomes are more likely and negative consequences are less likely. One of the most common and important things that trauma professionals do is to make decisions that may affect patient outcome (e.g. choose a destination hospital, intubate, order and interpret a test, move to the operating room, choose a specific operative procedure). We all have a set of thresholds that help us come to the “right” decision based on many variables. It appears that a single night of sleep deprivation has the potential to skew those thresholds, potentially in directions that may not benefit the patient.

In the next post, I’ll turn my attention to the impact of sleep loss on prehospital providers.

Reference: Sleep deprivation biases the neural mechanisms underlying economic preferences. J Neuroscience 31(10):3712-3718, March 9, 2011.

Mechanism

Closing Velocity And Injury Severity

Leave a comment

Trauma professionals, both prehospital and in trauma centers, make a big deal about “closing velocity” when describing motor vehicle crashes.  How important is this?

So let me give you a little quiz to illustrate the concept:

Two cars, of the same make and model, are both traveling on a two lane highway at 60 mph in opposite directions. Car A crosses the midline and strikes Car B head-on. This is the same as:

  1. Car A striking a wall at 120 mph
  2. Car B striking a wall at 60 mph
  3. Car A striking a wall at 30 mph

2010-saab-9-5-head-on-crash-test_100313384_m1

The closing velocity is calculated by adding the head-on components of both vehicles. Since the cars struck each other exactly head-on, this would be 60+60 = 120 mph. If the impact is angled there is a little trigonometry involved, which I will avoid in this example. And if there is a large difference in mass between the vehicles, there are some other calculation nuances as well.

So a closing velocity of 120 mph means that the injuries are worse than what you would expect from a car traveling at 60 mph, right?

Wrong!

In this example, since the masses are the same, each vehicle would come to a stop on impact because the masses are equal. This is equivalent to each vehicle striking a solid wall and decelerating from 60 mph to zero immediately. Hence, answer #2 is correct. If you remember your physics, momentum must be conserved, so both of these cars can’t have struck each other at the equivalent of 120 mph. The injuries sustained by any passengers will be those expected in a 60 mph crash.

If you change the scenario a little so that a car and a freight train are traveling toward each other at 60 mph each, the closing velocity is still 120 mph. However, due the the fact that the car’s mass is negligible compared to the train, it will strike the train, decelerate to 0, then accelerate to -60 mph in mere moments. The train will not slow down a bit. For occupants of the car, this would be equivalent to striking an immovable wall at 120 mph. The injuries will probably be immediately fatal for all.

Bottom line: Closing velocity has little relationship to the injuries sustained for most passenger vehicle crashes. The sum of the decelerations of the two vehicles will always equal the closing velocity. Those injuries will be consistent with the change in speed of the vehicle the occupants were riding, and not the sum of the velocities of the vehicles. 

Head

What Is The Zumkeller Index in TBI?

Leave a comment

I learned something new today: the Zumkeller index. Exciting! Most trauma professionals who take care of serious head trauma have already recognized the importance of quantifying extra-axial hematoma thickness (HT) and midline shift (MLS) of the brain. Here’s a picture to illustrate the concept:

Source: Trauma Surgery Acute Care Open

Zumkeller and colleagues first described the use of the mathematical difference between these two values in prognosticating outcomes in severe TBI in 1996.

Zumkeller Index (ZI) = Midline shift (MDI) – Hematoma thickness (HT)

Intuitively, we’ve been using this all along. At some point, we recognized that if the degree of midline shift exceeds the hematoma thickness, it’s a bad sign. The easiest way to explain this is that there is injury to the brain that is causing swelling so the shift is greater than the size of the hematoma. 

The authors of the current paper from Brazil decided to quantify the prognostic value of the ZI by doing a post-hoc analysis of a previously completed prospective study.  They limited their study to adult patients with an acute traumatic subdural hematoma confirmed by CT scan. It used data from the 4-year period from 2012-2015.

They compared demographics and outcomes in three cohorts of ZI:

  • Zero or negative ZI, meaning that the midline shift was less than the size of the hematoma
  • ZI from 0.1 mm to 3.0 mm
  • ZI > 3.0 mm

And here are the factoids:’

  • A total of 114 patients were studied, and the mechanism of injury was about 50:50 from motor vehicle crashes vs falls
  • About two thirds were classified as severe and the others were mild to moderate, based on GCS
  • Median initial GCS decreased from 6 in the low ZI group to 3 in the highest ZI group, implying that injuries were worse in the highest ZI group
  • Mortality (14-day) was 91% in the highest ZI group and only in the low 30% range in the others
  • Regression analysis showed that patients with ZI > 3 had an 8x chance of dying within 14 days compared to the others

Source: Trauma Surgery Acute Care Open

Bottom line: This study confirms and quantifies something that many of us have been unconsciously using all along. Of course there are some possible confounding factors that were not quantified in this study. Patients with the more severe injuries tended to also have subarachnoid hemorrhage and/or intra-ventricular blood. Both are predictors of worse prognosis. But this is a nice study that quantifies our subjective impressions.

The Zumkeller Index is an easily applied tool using the measuring tool of your PACS application. It can be used to determine how aggressively to treat your patient, and may help the neurosurgeons decide who should receive a decompressive craniectomy and how soon.

Reference: Mismatch between midline shift and hematoma thickness as a prognostic factor of mortality in patients sustaining acute subdural hematomaTrauma Surgery & Acute Care Open 2021;6:e000707. doi: 10.1136/tsaco-2021-000707

Equipment

So You Want Your Own Hybrid Room?!

Leave a comment

You’re hooked! You are thinking back to a number of cases that you think might have done better with a hybrid room. And now let’s assume you already have one in your OR suite. Now what do you do? Here’s my final post in this series to give you some things to think about.

The key is to avoid jumping right in and sending your next eligible patient straight to that room. You absolutely must take some time to develop policies and guidelines to make sure things go smoothly.

Here are some important things to think about:

  • Identify which specific patients are eligible so you don’t squander this resource
  • Who calls the OR to secure the room (surgeon, resident, other)?
  • Who calls the interventional radiologist?
  • What if another case (TEVAR, etc) is already on the table?
  • What if another case is getting ready to use the OR? How are conflicts resolved?
  • Develop an initial in-room report process so all the teams know the game plan
  • Assign an extra circulator to the room. You’ll need them!
  • Make sure all retractor and positioning systems (abdomen, crani) fit the table! Remember that little asterisk in the previous section? Some retraction systems may need adaptors to work with your table. Don’t find this out at the last minute!
  • What about lithotomy position? How will this work with your hybrid table? Most don’t have sections that break away, so this will not be available to you.
  • Ensure radiation protection for all, including thyroid shields.
  • Bag the bottom x-ray detector, otherwise it will get very, very gross!
  • Create an external fixator equipment cart that can be moved into the hybrid room. This will save time over having someone go pick individual items from the central core.
  • Create an embolization cart with appropriate wires, catheters, coils, etc. This stuff may not be stocked normally in the hybrid room.
  • If embolization is needed, be sure to have a “gopher” to fetch any equipment that’s not already on the cart or in the room.

And I’m sure there are more details that I haven’t thought of. If you have some helpful suggestions, policies, or protocols, please share them with me!

Equipment

Is The Hybrid OR For Trauma Useful? Part 2

Leave a comment

In my last post I reviewed several older papers that showed some positive associations with the use of a hybrid room for trauma patients. However, these rooms were not dedicated to the trauma patient. This means that they may not be staffed at all hours, or other elective cases could be scheduled in them. In either case, there were periods of time where the hybrid room might not be available for trauma procedures.

A study of the experience of one trauma center (University of Florida, Gainsville) with a truly dedicated, always available hybrid room for trauma patients was published just last month. Three and a half years of experience with the room was compared with historical controls from a similar period of time before implementation.  Patients younger than 18 were excluded, as were patients operated for reasons other than bleeding control (i.e. emergent trach). The room itself was a repurposed and remodeled angiography suite located one floor above the emergency department trauma bays.

Here are the factoids:

  • Overall patient demographics, including mechanism, severity of injury, prehospital intubation, and initial blood pressure.
  • Median Injury Severity Score (ISS) was 18 pre-hybrid and 22 post (not statistically significant but probably clinically so)
  • There was greater use of REBOA in the post-hybrid group (8%) vs pre-hybrid OR (1%)
  • The hybrid group achieved earlier hemorrhage control (49 vs 60 minutes); this is both statistically and clinically significant!
  • Blood and plasma transfusions given between 0 and 4 hours of arrival were the same pre- vs post-hybrid (3 vs 2.5 units PRBC and 2 vs 1.5 units plasma)
  • Although the authors claim significantly fewer transfusions of both products between 4 and 24 hours, the numbers  are clinically the same (1 vs 0 units of each)
  • The number of infectious complications was significantly less (27% pre- vs 15% post), but was entirely driven by pneumonia reduction from 12% to 4%. All other infections (bloodstream, surgical site, UTI, C. Diff, graft infection) were the same.
  • The number of days on the ventilator decreased from 3 to 2, which was statistically significant but clinically questionable

Bottom line: This paper was a bit problematic for me. I want to believe that a hybrid room is valuable because I’ve been involved with a handful of cases where I believe it made a big difference. And if you read only the abstract or the conclusions of the paper, it sounds great!

Always be careful of papers that go along with your confirmation bias. Read them even more carefully than you normally would. I have a few comments / questions:

  • First, the good news. The time to hemorrhage control decreased from 60 to 49 minutes using the hybrid room. Eleven minutes. Doesn’t seem like a lot, but this is probably the most important conclusion. Ongoing bleeding rapidly decreases survival, and literally, every minute counts.
  • Why was so little blood and plasma given? I can’t recall a hybrid room case where we have given less than 10 units of blood and other products. The volumes given in this study were just a couple of units, and the decrease of half a unit was statistically significant. In my opinion, this is not clinically relevant in these sick patients. But this fact is touted in the abstract and conclusion. And you can’t chalk it up to REBOA, because they only used it in 8% of the hybrid room patients.
  • The decrease in pneumonia was indeed clinically significant, dropping from 27% to 15%. However, all other infectious complications remained the same. But once again, the fact that infections (generically) were significantly decreased was called out in the abstract and conclusions. Just focus on pneumonia because that’s all it was.
  • Ventilator days decreased from 3 to 2 days, which may or may not be clinically significant even though statistical significance was achieved. This, too, is emphasized in the abstract and conclusions.

I really wanted this to paper to soundly demonstrate how great a dedicated hybrid room is. But what I see is a single-center experience that only shows that it clinically significantly decreases time to hemorrhage control and the incidence of pneumonia and not much more. The authors hit the nail on the head with their last sentence:

Association between time to hemorrhage control and clinical outcomes require further investigation, ideally using granular, standardized electronic health record data from multiple institutions.

I will keep waiting for the next paper and hope it really answers these questions! This one left me wanting a lot more.

Reference: Clinical impact of a dedicated trauma hybrid operating room. JACS 232(4):560-571, 2021.