This paper is from the group at ShockTrauma in Baltimore, who are really pushing the envelope of REBOA. We always worry about distal ischemia after balloon inflation, because the ischemia produced can be detrimental to the gut and lower extremities. This group was curious about what the flow patterns looked like with inflation of the balloon. So in select cases, they obtained CT scans with contrast in patients while the balloon was fully inflated (!!).
They reviewed their experience over a four year period, looking at patients receiving a CT scan with the REBOA balloon partially or fully inflated.
Here are the factoids:
- Nine patients were included. This makes sense because unstable patients should not go to CT scan, so this should be a very limited group.
- Mean injury severity score (ISS) was 48, which makes sense. These patients are hurt bad!
- Four patients had supraceliac REBOA (aortic zone I) and five had infrarenal (zone III)
- Contrast was seen below the REBOA balloon in all patients, and was seen distal to the insertion site in half
- Collateral flow around the balloon was identified in all patients
Bottom line: The authors found that REBOA decreased blood flow to the distal aorta, but certainly did not stop it. Collateral flow is underestimated, and probably provides a protective effect for the viscera and other structures while inflated. This is good news for REBOA proponents, because it suggests that placement may not cause as much risk from ischemia as originally thought.
But why oh why did they have to go to CT in the first place?
Reference: Assessment of blood flow patterns distal to aortic occlusion (AO) using computed tomography in patients with resuscitative endovascular balloon occlusion of the aorta. JACS 225(4S1):S50, 2017.
The annual Clinical Congress for the American College of Surgeons will be held at the end of the month. A large number of research papers are presented there, and a smaller subset are related to trauma and critical care.
I’m going to spend the next week and a half or so reviewing many of the ones I believe are the most promising. Keep in mind that these are works in progress, and that many will never see the light of print. I’ll take them apart, trying to see how good each one is. Some are very good, some are hopelessly flawed.
I hope you enjoy the analysis! Let’s see if we learn something new along the way.
I’ve been discussing the little research there is on stay and play vs scoop and run. And now, hot off the press, we have a paper about the ultimate version of scoop and run, the “drive-by ambulance.” This one looks at outcomes in patients who are dropped at the emergency department by private vehicle. This is the most basic form of prehospital care, with no interventions, just transportation. This type of transport is used by parents with their injured children, police who act as very basic first responders in some cities, and on occasion, gang members.
A multi-institutional group of authors used data in the National Trauma Databank to try to answer this question. They used three years worth of data, comparing outcomes from patients with ground EMS vs private transport who were treated at Level I and Level II trauma centers. Only gunshots and stabs were included, and all patients were 16 or older. The authors were focused on only one thing: mortality. This included death in the ED, and a model was developed to adjust risk based on vital signs, injury severity score (ISS), race, and insurance status. Just over 100,000 were included in he final analysis.
Here are the factoids:
- Black and hispanic patients were more frequently transported by private vehicle, but only by about 3%
- White patients were more frequently taken by ground EMS, by about 6%
- Stabs were more likely to be brought by private car than gunshots, 56% vs 44%
- Mean ISS was significantly higher for those transported by ground EMS (10 vs 5.5)
- Unadjusted mortality was lower overall for private vehicle, 2% vs 12%
- The chance of dying in the ED was also decreased in the private transport patients, from 7% to 1%
- Mortality from both gunshots and stabs were also significantly lower (5% vs 9%, and 0.2% vs 3% respectively)
- Once adjusted for risk, the lower mortality with private transport remained, with a 60% risk reduction of death. This persisted in the gunshot and stab cohorts as well.
Bottom line: Wow! Although this study has the usual limitations of using a large external database, it was very well designed to compensate for that. And the degree of improvement in survival is surprising. What this study can’t tell us is why. Certainly, some patients benefit from a little extra time to give fluid or blood, intubate, or provide some other treatments. But the patient with penetrating frequently does not need this, they just need definitive control of hemorrhage. The authors even go so far as to suggest that at-risk populations receive education on “scoop and run” if people they know suffer penetrating injury.
The next step is to tease out which components of the stay and play paradigm are the most valuable, and which contribute to the increased mortality in penetrating injury patients.
Reference: Association of Prehospital Mode of Transport With Mortality in Penetrating Trauma A Trauma System–Level Assessment of Private Vehicle Transportation vs Ground Emergency Medical Services. JAMA Surgery, Published online September 20, 2017.
Scoop and run or stay and play. Is one better that the other? Over my last two posts, I reviewed a couple of papers that were older (6-7 years) and had smaller patient groups. Now let’s look at a more recent one with a larger experience using a state trauma registry.
This one is from the Universities of Pittsburgh and Rochester, and used the Pennsylvania state trauma registry for study material. The authors wanted to really slice and dice the data, postulating that previous studies were not granular enough, such that significant trends could not be seen due to lumping all prehospital time together. They divided prehospital time into three components: response time, scene time, and transport time. To some degree, the first and third components are outside of the prehospital providers’ control.
The records for over 164,000 patients were analyzed. These only included those for patients transported from the scene by EMS, and excluded burns. The prehospital time (PH time) was divided into the three components above. A component was determined to be prolonged if it contributed > 50% of the total PH time.
Here are the factoids:
- Half of the patients had a prolonged PH time interval (52%)
- Response time was prolonged in only 2%, scene time was prolonged in 19%, and transport time was longer in 31%
- Mortality was 21% higher in those with a prolonged scene time component
- There was no mortality difference in patients with no prolonged time components, or those with prolonged response or transport times
- These patterns held for both blunt and penetrating injury
- Extrication and intubation were common reasons for prolonged scene time. Extrication added an average of 4.5 minutes, and intubation 6.5 minutes.
- Mortality was increased with prehospital intubation, but this effect lessened in severe TBI
- Increasing experience with extrication and intubation appeared to decrease the mortality from the increased scene time they caused
Bottom line: This paper suggests that the dichotomy of “scoop and run” vs “stay and play” may be too crude, and that a more nuanced approach should be considered. In plain English, the optimal management lies somewhere in between these polar opposites. Actual on scene time appears to be the key interval. EMS providers need to be aware of scene time relative to response and transport times. Patients with specific injury patterns that benefit from short scene times (hypotension, flail, penetrating injury) can quickly be identified and care expedited. Increased scene time due extrication cannot be avoided, but prehospital intubation needs to be considered carefully due to the potential to increase mortality in select patients.
Reference: Not all prehospital time is equal: Influence of scene time on mortality. J Trauma 81(1):93-100, 2016.
Yesterday, we looked at an older study that kind of examined the scoop and run vs stay and play debate. Let’s move forward in time a little bit, and evaluate the two options in a penetrating trauma model.
This one is from the anesthesia and intensive care departments at the university hospital in Copenhagen. The authors prospectively captured information on 462 penetrating trauma victims, then looked up their 30 day survival status in a national administrative database.
Here are the factoids:
- Only 95% of patient records (446) were available for 30 day review (better that in the US!)
- Of those, 40 were dead (9%)
- Using raw statistics, there seemed to be a significant increase in mortality if the prehospital crew was on scene more than 20 minutes
- However, when corrected for age, sex, injury pattern, etc. there was no significant difference in survival for short vs longer scene stays
- Multivariate analysis identified the number of procedures performed at the scene as a significant predictor of mortality, regardless of time
Bottom line: We still can’t seem to show a difference in patients who are tossed in the back of the squad and driven vs those who have IVs, immobilization, and other things done to begin resuscitation and increase safety prior to transport! However, the bit about number of procedures is intriguing. Is this just another surrogate for time? Are there unrecognized complications from them that affect survival?
Next time, I’ll look at a recent publication from the US that gives us yet another angle on this question.
Reference: On-scene time and outcome after penetrating trauma: an observational study. Emerg Med J 28(9):87-801, 2011.