Category Archives: Resuscitation

Resuscitation

How To Remember Those “Classes of Hemorrhage”

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The Advanced Trauma Life Support course lists “classes of hemorrhage”, and various other sources list a similar classification for shock. I’ve not been able to pinpoint where these concepts came from, exactly. But I am sure of one thing: you will be tested on it at some point in your lifetime.

Here’s the table used by the ATLS course:

classes_of_shock

The question you will always be asked is:

What class of hemorrhage (or what % of blood volume loss) is the first to demonstrate systolic hypotension?

This is important because prehospital providers and those in the ED typically rely on systolic blood pressure to figure out if their patient is in trouble.

The answer is Class III, or 30-40%. But how do you remember the damn percentages?

multiscore-maxi1

It’s easy! The numbers are all tennis scores. Here’s how to remember them:

Class I up to 15% Love – 15
Class II 15-30% 15 – 30
Class III 30-40 30 – 40
Class IV >40% Game (almost) over!

Bottom line: Never miss that question again!

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Resuscitation

MTP And The Blood Availability Trap In Trauma Team Activations

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Early availability of blood is a key component in the successful resuscitation of severely injured trauma patients. All trauma centers have implemented massive transfusion protocols (MTP) to ensure rapid delivery of blood products to the trauma bay.

Unfortunately, locating the blood bank in some remote corner of the basement is common practice, as far from the trauma bay as possible. This guarantees a delivery delay once the MTP is activated. To offset this, many centers have implemented policies to make a limited quantity of blood products available in the trauma bay.

This supply can be located in a blood refrigerator located nearby. Or it may be a practice of calling for emergency release blood if the trauma professionals believe it might be necessary. Some trauma centers have codified this so that highest-level activations automatically have a cooler of blood products delivered, hopefully before patient arrival.

However, I have observed while visiting numerous centers that this often causes an unintended consequence. It can actually slow MTP activation!

How can that be, you say? It’s simple. Critically injured patients result in an intense and highly charged trauma activation. The surgeon is concentrating on keeping the patient alive and orders the emergency release blood to be hung. The resuscitation continues. “Hang another unit.” And so on.

Eventually, the temporary supply runs out. Then everybody looks at each other and does a facepalm. Nobody thought to activate the MTP!

How can this be avoided? The key is to do everything possible to activate it from the very start. Here are some tips:

  • Use an objective scoring system to trigger MTP. The two most common ones are the ABC score and the Shock Index. Both are easy to calculate, and can frequently be used based on the prehospital report. This means the MTP can be activated before the patient even arrives.
  • If you open the blood refrigerator or touch the emergency release blood, activate the MTP. This will give you two to four units to buy time for the first MTP cooler to arrive.
  • Empower everyone in the trauma bay to speak up. Make sure everyone knows the rules listed above, and encourage them to speak up if they see that any of them are met. “Team leader, should we activate the MTP?”
  • Don’t be shy! If you only transfuse one unit of refrigerator blood and stop, no harm, no foul. The unopened MTP cooler can be sent back to the blood bank with no risk of waste.

Bottom line: Don’t get suckered into forgetting to activate the MTP just because it looks like you have blood available. Automate the process so you never run out again.

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Resuscitation

MTP Activation Criteria For Pediatric Patients

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Early resuscitation, particularly with blood products in patients with hemorrhage, is literally a lifesaver.  As each minute ticks by, survival slowly diminishes. To facilitate this, massive transfusion protocols (MTP) have been designed to rapidly deliver sizable quantities of blood products to the trauma resuscitation bay.

One of the recurring issues I see at trauma centers is the lack of a reliable way of activating the MTP. Many centers publish what I consider “psychic criteria.” These promote criteria that involve the amount of blood loss over four or twenty-four hours. Who even knows?

Delays in activating the MTP frequently occur because no one thinks about it when a critically injured patient arrives. All of the trauma professionals are busy with the patient and are rudely surprised when they ask for the first unit of blood.

Objective MTP activation criteria have been developed and are well-supported by the literature. The ABC score and the shock index are two of the more common methods. Both are based on observations made upon patient arrival (and possibly before if a prehospital report is received).

The ABC score uses four criteria:

  • Heart rate > 120
  • Systolic blood pressure < 90
  • FAST positive
  • Penetrating mechanism

If any two of these are present, there is a 50% chance that massive transfusion is warranted.

The Shock Index (SI) uses the initial vital signs to perform a quick and dirty calculation by dividing the heart rate by the systolic blood pressure.  A score greater than or equal to one predicts at least a 2x higher need for blood. Of the two, SI is more easily calculated and gives a marginally more accurate result.

But what about children? The ABC score was evaluated in pediatric patients and was found to be much less sensitive than in adults. Combining the ABC score with an age-adjusted Shock Index improved the accuracy only slightly. This was named the ABC-S score.

Several adult and pediatric trauma centers in the Denver area collaborated to test a new score using the ABC-S score in combination with serum lactate and base deficit. This was termed the ABC-D score. Clever.

Here are the factoids:

  • A retrospective review of patients aged 1-18 from a single trauma registry who had received a blood transfusion during their initial care
  • The study included 211 children, of whom 66 required massive transfusion
  • The three methods listed above were compared, and the ABC-D score was found to be the most predictive of MTP
  • ABC-D was 77% sensitive and 79% specific
  • The authors showed that the accuracy and balance between sensitivity and specificity improved for each point increase in the ABC-D score.
  • They concluded that ABC-D may be a useful tool to expedite the delivery of blood products during a trauma resuscitation.

Bottom line: Hmm. The system that they developed and the analysis of their experience appears to be sound. But unfortunately, it fails the practicality test. Here’s the sticking point. How long does it take to obtain that initial blood specimen, send it to your lab, and then return stat results to your trauma bay? Once you receive the results, you then activate the MTP and wait another 5-10 minutes for the first cooler to arrive!

That’s an awful long time to wait for blood while you watch a child hemorrhaging in front of you. So what to do? For now, use one of the existing systems to make a rapid decision. And always err on the side of activation. You can always send the blood back if you don’t need it!

Reference:  The ABC-D score improves the sensitivity in predicting need for massive transfusion in pediatric trauma patients. J Pediatr Surg. 2020 Feb;55(2):331-334. doi: 10.1016/j.jpedsurg.2019.10.008. Epub 2019 Nov 1. PMID: 31718872.

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Resuscitation

Artificial Platelets Under Development!

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Uncontrolled bleeding is the bane of trauma professionals everywhere. Early in a resuscitation, we focus on identifying potential sources. We’ve developed numerous techniques for plugging them up. And we have processes in place to replace the blood that’s been lost.

Unfortunately, blood products are a perishable item. Packed red blood cells have a typical shelf-life of 42 days. Whole blood lasts only 21-35 days. Plasma is only suitable for up to five days once thawed. However, it can be frozen and used only when needed.

Platelets are another short-lifespan product, typically lasting only five days. This is a major reason for the relative lack of availability, especially at smaller hospitals. Unfortunately, freezing them or attempting cold storage renders them less active. For this reason, the platelet shortage persists.

As you know, platelets are fragments of cells produced by the bone marrow that have a major function in hemostasis. They bind to injured surfaces of disrupted blood vessels. Seconds later, they become activated and begin to clump with other platelets. They also release factors that result in fibrin deposition, creating a clot that helps stop bleeding.

Researchers have been trying to develop artificial blood substitutes for decades. I remember reading about rat experiments using these products in the 1980s. Unfortunately, they remain experimental to this day.

I found a recent article describing recent work on artificial platelets that piqued my interest. It was published by the biomedical engineering groups at North Carolina State University and UNC Chapel Hill. They used nanoparticles made of an ultrasoft microgel that were similar in size and shape to natural platelets. Fibrin-binding antibody fragments were embedded on the surface. These were selected to target only activated fibrin and not circulating fibrinogen.

Source: Science Translational Medicine

The groups devised a rat and pig trauma model by creating a liver laceration and then infusing varying doses of the artificial platelets (AP). Postmortem analysis of the wounds showed:

  • The APs did home in on the injured sites and were found in the injured areas
  • There was increased fibrin deposition at the wound site when compared to saline controls
  • Less bleeding was seen in the animals that received the APs vs saline
  • No significant deposition of APs was found in other tissues
  • The APs were excreted in the urine of the animals

Bottom line: This is very exciting, if preliminary, work. These artificial platelets are relatively easy to produce and can be frozen or stored at room temperature for extended periods. They appear harmless to the animals and decrease bleeding from the liver injury.

I am still somewhat cautious in my assessment. This same excitement was present 40 years ago in the early years of artificial hemoglobin solutions. And look where we are now. But, fingers crossed, there may be a solution to our chronic platelet shortage at some point in the future.

Reference: Ultrasoft platelet-like particles stop bleeding in rodent and porcine models of trauma. Sci Transl Med. 2024 Apr 10;16(742):eadi4490. doi: 10.1126/scitranslmed.adi4490. Epub 2024 Apr 10. PMID: 38598613.

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Resuscitation

Giving TXA Via An Intraosseous Line?

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Seriously injured patients frequently develop coagulopathy, which makes resuscitation (and survival) more challenging. A few years ago, the CRASH-2 study lent support for using tranexamic acid (TXA) in select trauma patients to improve survival. This drug is cheap and has antifibrinolytic properties that may be beneficial if given for life-threatening bleeding within 3 hours of initial injury. It’s typically given as a rapid IV infusion, followed by a slower followup infusion. The US military has adopted its routine use at forward combat hospitals.

But what if you don’t have IV access? This can and does occur with military type injuries. Surgeons at Madigan Army Medical Center in Washington state tried using a common alternative access device, the intraosseous needle, to see if the results were equivalent. This study used an adult swine model with hemorrhage and aortic crossclamping to simulate military injury and resuscitation. Half of the animals then received IV TXA, the other half had it administered via IO. Only the bolus dose was given. Serum TXA levels were monitored, and serial ROTEM determinations were performed to evaluate coagulopathy.

Here are the factoids:

  • The serum TXA peak and taper curves were similar. The IV peak was higher than IO and approached statistical significance (0.053)
  • ROTEM showed that the animals were significantly hyperfibrinolytic after injury, but rapidly corrected after administration of TXA. Results were the same for both IV and IO groups.

Bottom line: This was a very simple and elegant study. The usual animal study issues come into play (small numbers, pigs are not people). But it would be nearly impossible to have such a study approved in humans. Even though the peak TXA concentration via IO is (nearly significantly) lower, this doesn’t appear to matter. The anti-fibrinolytic effect was very similar according to ROTEM analysis.

From a practical standpoint, I’m not recommending that we start giving TXA via IO in civilian practice. We don’t typically see military style injuries, and are usually able to establish some type of IV access within a reasonably short period of time. But for our military colleagues, this could be a very valuable tool!

Reference: No intravenous access, no problem: Intraosseous administration of tranexamic acid is as effective as intravenous in a porcine hemorrhage model. J Trauma 84(2):379-385, 2018.

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