# Can Prehospital Providers Accurately Estimate Blood Loss? Part 2

I’ve previously written about the difficulties estimating how much blood is on the ground at the trauma scene. In general, EMS providers underestimated blood loss 87% of the time. The experience level of the medic was of no help, and the accuracy actually got worse with larger amounts of blood lost!

A group in Hong Kong developed a color coded chart (nomogram) to assist with estimation of blood loss at the scene. It translated the area of blood on a non-absorbent surface to the volume lost. A convenience study was designed to judge the accuracy that  could be achieved using the nomogram. Sixty one providers were selected, and estimated the size of four pools of blood, both before and after a 2 minute training session on the nomogram.

Here’s what it looks like:

Note the areas across the bottom. In addition to colored square areas, the orange block is a quick estimate of the size of a piece of paper (A4 size since they’re in Hong Kong!)

Here are the factoids:

• The 61 subjects had an average of 3 years of experience
• Four scenarios were presented to each: 180ml, 470ml, 940ml, and 1550ml. These did not correspond exactly to any of the color blocks.
• Before nomogram use, underestimation of blood loss increased as the pool of blood was larger, similar to the previous study
• There was a significant increase in accuracy for all 4 scenarios using the nomogram, and underestimation was significantly better for all but the 940ml group
• Median percentage of error was 43% before nomogram training, vs only 23% after. This was highly significant.

Bottom line: This is a really cool idea, and can make estimation of field blood loss more accurate. All the medic needs to do is know the length of their shoe and the width of their hand in cm. They can then estimate the length and width of the pool of blood and refer to the chart . Extrapolation between colors is very simple, just look at the line. The only drawback I can see occurs when the blood is on an irregular or more absorbent surface (grass, inside of a car).

Related posts:

Reference:  Improvement of blood loss volume estimation by paramedics using a pictorial nomogram: a developmental study. Injury article in press Oct 2017.

# Can Prehospital Providers Accurately Estimate Blood Loss?

EMS providers are the trauma professional’s eyes and ears when providing transportation from the scene of an accident. We rely on their assessment of the mechanism of injury and the amount of blood lost. We tend to believe in the accuracy of those assessments.

A study was carried out that tested EMS personnel on their ability to accurately estimate specific amounts of blood that were left at a simulated accident scene. The blood volumes tested were 500cc, 1000cc, 1500cc and 2100cc. A total of 92 professionals participated, and there was an even split into basic EMTs (34%), intermediate/critical care EMTs (33%) and paramedics (31%). Experience levels were as follows: 0-5 years 43%, 6-10 years 30%, >10 years 31%.

The results were as follows:

• 87% underestimated the quantity of blood
• 9% overestimated
• 4% guessed the exact amount
• Experience or credentialing level did not matter

Only 8% of the subjects were within 20% of the actual volume, and an additional 19% were within 50%. In general, most medics underestimated the amount of blood lost, and their guesses were worse with higher volumes. The median guess for the 2100cc loss group was only 700cc!

Bottom line: Visual estimates of blood loss are extremely inaccurate, and are most likely  underestimates. Physicians in the ED should rely on exam and physiology to help determine the amount of blood loss. For safe measure, multiply the reported blood loss of the EMT or paramedic by 2 or 3 to get a realistic number.

Reference: Patton et al. Accuracy of Estimation of External Blood Loss by EMS Personnel. J Trauma 50(5), 914, 2001.

# Uber / Lyft For Medical Transport???

Yesterday I discussed nonstandard first responders (police). Today I’ll share some info on nonstandard ambulances.

In this day and age of ride sharing apps like Uber and Lyft, it is possible to get a cheap ride virtually anywhere there is car service and a smart phone. And of course, some people have used these services for transportation to the hospital in lieu of an ambulance ride. What might the impact be of ride services on patient transport, for both patient and EMS?

A paper in preparation suggests that ambulance service calls decreased by 7% after the introduction of UberX rides. Now, there are a lot of questions here, because the full paper has not yet been peer reviewed, and the results write-up is pretty sketchy. But it does beg the question.

Ambulance rides are expensive. Depending on region, they may range from \$500-\$5000. And although insurance may reduce the out of pocket cost, it can still be expensive. So what are the pros vs the cons of using Uber or Lyft for medical transport?

Pros:

• Ride shares are inexpensive compared to an ambulance ride
• They may arrive more quickly because they tend to circulate around an area, as opposed to using a fixed base
• Riders may select their preferred hospital without being overridden by EMS (although it may be an incorrect choice)
• May reduce EMS usage for low acuity patients

Cons:

• No professional medical care available during the ride
• May end up being slower due to lack of lights and siren
• Damage fees of \$250+ for messing up the car

Bottom line: Uber and Lyft are just another version of the “arrival by private vehicle” paradigm. Use of these services relies on the customer/patient having very good judgment and insight into their medical conditions and care needs. And from personal experience, this is not always the case. I would not encourage the general public to use these services for medical transport, and neither do the companies themselves!

Reference: Did UberX Reduce Ambulance Volume? Unpublished paper, October 24, 2017.

(This paper remains unpublished! Hmm… but the link will take you to a copy of the manuscript)

# Trauma Patient Transport By Police, Not EMS

When I was at Penn 30+ years ago, I was fascinated to see that police officers were allowed to transport penetrating trauma patients to the hospital. They had no medical training and no specific equipment. They basically tossed the patient into the back seat, drove as fast as possible to a trauma center, and dropped them off. Then they (hopefully) hosed down the inside of the squad car.

Granted, it was fast. But did it benefit the patient? The trauma group at Penn decided to look at this to see if there was some benefit (survival) to this practice. They retrospectively looked at 5 years of data in the mid-2000’s, thus comparing the results of police transport with reasonably state of the art EMS transport.

They found over 2100 penetrating injury transports during this time frame (!), and roughly a quarter of those (27%) were transported by police. About 71% were gunshots vs 29% stabs.

Here are the factoids:

• The police transported more badly injured patients (ISS=14) than EMS (ISS=10)
• About 21% of police transports died, compared to 15% for EMS
• But when mortality was corrected for the higher ISS transported by police, it was equivalent for the two modes of transport

Although they did not show a survival benefit to this practice, there was certainly no harm done. And in busy urban environments, such a policy could offload some of the workload from busy EMS services.

Bottom line: Certainly this is not a perfect paper. But it does add more fuel to the “stay and play” vs “scoop and run” debate. It seems to lend credence to the concept that, in the field, less is better in penetrating trauma. What really saves these patients is definitive control of bleeding, which neither police nor paramedics can provide. Therefore, whoever gets the patient to the trauma center in the least time wins. And so does the patient.

Related posts:

Reference: Injury-adjusted mortality of patients transported by police following penetrating trauma. Acad Emerg Med 18(1):32-37, 2011.

# Prehospital Use Of The ABC Score And MTP

Early and appropriate resuscitation is critical in any severely injured trauma patient. Typically, the trauma team assesses the patient upon arrival and makes a determination as to what type of resuscitation fluids are most appropriate. If blood is judged to be necessary, individual units can be given, or the massive transfusion protocol (MTP) can be activated.

I’ve previously written about two objective methods to assist in the decision to activate your MTP, shock index (SI) and assessment for blood comsumption (ABC). These have traditionally been applied once the patient arrived. What would happen if you used prehospital information to calculate the ABC score and were able to activate your MTP sooner rather than later?

The group at the University of Colorado in Aurora studied this concept. The charge nurse captured information to calculate the ABC score from the initial prehospital information received by phone while the patient was enroute. He or she would then activate the MTP in order to have blood products delivered as close to patient arrival as possible.

They reviewed their experience over a 29-month period. The first 15 months used their original system, calculating ABC on arrival and then deciding whether to activate MTP. During the final 14 months, it was calculated prior to patient arrival and the MTP was “pre”-activated when the score was 2 or more. The primary outcome studied was mortality, and secondary variables were appropriate activation of MTP, and adherence to balanced resuscitation ratios.

Here are the factoids:

• A total of 119 patients with hypotension and/or MTP activation were studied; 24 occurred pre-implementation and 95 post
• Pre-implementation, 63% of 24 hypotensive patients had MTP activation and only 6 (40%) received blood. Only 2 patients (33%) had RBC:FFP ratios between 1:1 and 2:1.
• Post-implementation, 98% of hypotensive patients had MTP activation, a 6-fold increase
• Also post-implementation, 42% of the activations received the blood, and balanced product ratios increased to 77%
• Overall mortality decreased from 42% to 19% after implementation, all of which occurred in the penetrating injury group
• Hospital and ICU lengths of stay were unchanged and there were no readmissions

Bottom line: The authors actually rolled two studies into one here. The main focus of the paper was to look at use of ABC score using prehospital information, but they also changed their MTP setup at the same time. During the initial part of the study, they did not have thawed plasma available, so the first cooler contained only red cells. Plasma was delivered when available, usually about 45 minutes after the first cooler had arrived. Post-implementation, thawed plasma was included in the first cooler.

So is the reduction in mortality (only in penetrating injury) due to early availability of the entire cooler, or because the desired product ratios were much more consistently met? Unfortunately, we can’t know.

This is a relatively small study, but the results with respect to blood actually being given, attainment of ratios, and mortality are impressive. Is the takeaway message to activate MTP early based on prehospital info or to make sure all coolers stock plasma? My take is that it’s probably best to do both!

Related posts:

Reference: Effect of pre-hospital use of the assessment of blood consumption score and pre-thawed fresh frozen plasma on resuscitation and trauma mortality. JACS 228:141-147, 2019.