Category Archives: Laboratory

Serial Hemoglobin / Hematocrit – Huh? Part 2

May 20, 2020 The Trauma Pro Leave a comment

In my last post, I waxed theoretical. I discussed the potential reasons for measuring serial hemoglobin or hematocrit levels, the limitations due to the rate of change of the values, and conjectured about how often they really should be drawn.

And now, how about something more practical? How about an some actual research? One of the more common situations for ordering serial hemoglobin draws occurs in managing solid organ injury. The vast majority of the practice guidelines I’ve seen call for repeating blood draws about every six hours. The trauma group at the University of Florida in Jacksonville decided to review their experience in patients with liver and spleen injuries. Their hypothesis was that hemodynamic changes would more likely change management than would lab value changes.

They performed a retrospective review of their experience with these patients over a one year period. Patients with higher grade solid organ injury (Grades III, IV, V), either isolated or in combination with other trauma, were included. Patients on anticoagulants or anti-platelet agents, as well as those who were hemodynamically unstable and were immediately operated on, were excluded.

Here are the factoids:

A total of 138 patients were included, and were separated into a group who required an urgent or unplanned intervention (35), and a group who did not (103)
The intervention group had a higher ISS (27 vs 22), and their solid organ injury was about 1.5 grades higher
Initial Hgb levels were the same for the two groups (13 for intervention group vs 12)
The number of blood draws was the same for the two groups (10 vs 9), as was the mean decrease in Hgb (3.7 vs 3.5 gm/dl)
Only the grade of spleen laceration predicted the need for an urgent procedure, not the decrease in Hgb

Bottom line: This is an elegant little study that examined the utility of serial hemoglobin draws on determining more aggressive interventions in solid organ injury patients. First, recognize that this is a single-institution, retrospective study. This just makes it a bit harder to get good results. But the authors took the time to do a power analysis, to ensure enough patients were enrolled so they could detect a 20% difference in their outcomes (intervention vs no intervention).

Basically, they found that everyone’s Hgb started out about the same and drifted downwards to the same degree. But the group that required intervention was defined by the severity of the solid organ injury, not by any change in Hgb.

I’ve been preaching this concept for more than 20 years. I remember hovering over a patient with a high-grade spleen injury in whom I had just sent off the requisite q6 hour Hgb as he became hemodynamically unstable. Once I finished the laparotomy, I had a chance to pull up that result: 11gm/dl!

Humans bleed whole blood. It takes a finite amount of time to pull fluid out of the interstitium to “refill the tank” and dilute out the Hgb value. For this reason, hemodynamics will always trump hemoglobin levels for making decisions regarding further intervention. So why get them?

Have a look at the Regions Hospital solid organ injury protocol using the link below. It has not included serial hemoglobin levels for 18 years, which was when it was written. Take care to look at the little NO box on the left side of the page.

I’d love to hear from any of you who have also abandoned this little remnant of the past. Unfortunately, I think you are in the minority!

Click here for the Regions Hospital Solid Organ Injury Protocol

Reference: Serial hemoglobin monitoring in adult patients with blunt solid organ injury: less is more. J Trauma Acute Care Open 5:3000446, 2020.

Laboratory

Serial Hemoglobin / Hematocrit – Huh? Part 1

May 18, 2020 The Trauma Pro Leave a comment

The serial hemoglobin (Hgb) determination. We’ve all done them. Not only trauma professionals, but other in-hospital clinical services as well. But my considered opinion is that they are not of much use. They inflict pain. They wake patients up at inconvenient hours. And they are difficult to interpret. So why do them?

First, what’s the purpose? Are you looking for trends, or for absolute values? In trauma, the most common reason to order is “to monitor for bleeding from that spleen laceration” or some other organ or fracture complex. But is there some absolute number that should trigger an alarm? If so, what is it? The short answer is, there is no such number. Patients start out at a wide range of baseline values, so it’s impossible to know how much blood they’ve lost using an absolute value. And we don’t use a hemoglobin or hematocrit as a failure criterion for solid organ injury anymore, anyway.

What about trends, then? First, you have to understand the usual equilibration curve of Hgb/Hct after acute blood loss. It’s a hyperbolic curve that reaches equilibrium after about 3 days. So even if your patient bled significantly and stopped immediately, their Hgb will drop for the next 72 hours anyway. If you really want to confuse yourself, give a few liters of crystalloid on top of it all. The equilibration curve will become completely uninterpretable!

And how often should these labs be drawn? Every 6 hours (common)? Every 4 hours (still common)? Every 2 hours (extreme)? Draw them frequently enough, and you can guarantee eventual anemia.

Bottom line: Serial hemoglobin/hematocrit determinations are nearly worthless. They cost a lot of money, they disrupt needed rest, and no one really knows what they mean. For that reason, my center does not even make them a part of our solid organ injury protocol. If bleeding is ongoing and significant, we will finding it by looking at vital signs and good old physical exam first. But if you must, be sure to explicitly state what you will do differently at a certain value or trend line. If you can’t do this and stick to it, then you shouldn’t be ordering these tests in the first place!

In my next post, I’ll discuss a newly published paper that objectively shows the (lack of) utility of this testing method.

Laboratory, Resuscitation

MTP Week Part 4: How To Build Your Massive Transfusion Protocol

January 31, 2019 The Trauma Pro Leave a comment

Massive Transfusion Protocol (MTP) week continues! I’m releasing the next Trauma MedEd newsletter to subscribers at the end of the week, which deals with advanced MTP topics. So leading up to that, I am reviewing the basics for the next several days. I’ll continue today with MTP activation triggers.

What criteria should trigger your massive transfusion protocol? Sometimes, it’s obvious. The EMS report indicates that your incoming patient is in shock. Or there was notable blood loss at the scene. Or they have a mangled extremity and will need blood products in the OR, if not sooner.

But sometimes the need for ongoing and large quantities of blood sneaks up on you. The patient is doing well but has an unexplained pressure dip. And it happens again. You give one of your uncrossmatched units of blood. It happens again. At some point, you come to the realization that you’ve given six units of blood and no plasma or other products! Ouch!

Many trauma centers have adopted MTP criteria like:

More than 4 units given over 4 hours
More that 10 units to be given over 24 hours
Loss of half a blood volume over 24 hours

I call these the “psychic power” criteria, because one must surely be prescient to know this information just shortly after the patient arrives. Don’t include criteria like these at your center!

Instead use some sort of objective criteria. A simple one is the use of any of your blood refrigerator products or emergency release blood, or a calculated score such as the ABC score or shock index (SI).

ABC score is the Assessment of Blood Consumption score and gives one point each for a heart rate > 120, SBP < 90, positive FAST, penetrating mechanism. ACS score > 2 was predictive of requiring MTP with sensitivity and specificity of about 85%. Overtriage was about 15%.

Shock index (SI) is defined as the heart rate divided by the SBP. Normal values are in the range of 0.5 to 0.7. Need for MTP was found to increase to 2x for SI of 0.9, 4x with an SI of 1.1, and 7x with SI 1.3.

A recent paper compared these two systems retrospectively on 645 trauma activations over a 5-year period. They found that they both worked well with the following results:

Shock index > 1 – 68% sensitive 81% specific
ABC > 2 – 47% sensitive, 90% specific

The study suggests that shock index is more sensitive, and takes less technical skill to calculate. Bottom line: just pick the some objective criterion you are most comfortable with and use it!

Reference: Accuracy of shock index versus ABC score to predict need for massive transfusion in trauma patients. Injury 49(1): 15-19, 2018

Well folks, that’s it for MTP week! Hope you enjoyed it.

And don’t forget to subscribe to TraumaMed if you want to get a full newsletter discussing advanced MTP topics tomorrow. Otherwise, you’ll be reading a post on CT scans and rib fractures in the elderly! Subscribe and download back issues by clicking here.

Links: (note – future links will not be live until 9am the day they are published)

Laboratory, Resuscitation

MTP Week Part 3: How To Build Your Massive Transfusion Protocol

January 30, 2019 The Trauma Pro Leave a comment

Deactivation. There are two components to this: recognizing that high volume blood products are no longer needed, and communicating this with the blood bank. As bleeding comes under surgical control, and CBC and clotting parameters (and maybe TEG/ROTEM) normalize, the pace of transfusion slows, and ultimately stops. Until this happens, the MTP must stay active. Even a low level of product need should be met with coolers stocked with the appropriate ratios of products.

There are two ways to stop the MTP: the surgeon or their surrogate calls the blood bank (when no more blood products are to be used), or the blood bank calls the surgeon after the next cooler has been waiting for pickup for a finite period of time. This is typically about 30 minutes. It is extremely helpful if the exact deactivation time is recorded in the electronic medical record. However, this information can be obtained from the blood bank.

Analysis. It’s all over, and now the real fun begins. For most trauma centers, the blood bank maintains extensive data about every aspect of each MTP event. They record what units were released and when, when they were returned, which ones were used, were they at a safe temperature on return or were they wasted, and much, much more! Typically, one of the blood bank supervisors or a pathologist then compiles and reviews this data. What happens next varies by hospital.

Ideally, the information from every MTP activation gets passed on to the trauma program. Presentation at your transfusion committee is fine, but this data is most suitable for presentation at the trauma operations committee. And if significant variances are present (e.g. product ratios are way off) then it should also be discussed at your multidisciplinary trauma PI committee as well.

There are relatively few standard tools out there that allow the display of MTP data in an easily digestible form. Here are some of the key points that must be reviewed by the trauma PI program:

Demographics
Components used (for ratio analysis)
Lab values (INR, TEG, Hgb, etc)
Logistics
Waste

I am aware of two tools, the Broxton form and an MTP audit tool from the Australian National Blood Authority. The Broxton tool covers all the basics and includes some additional data points that cover activation criteria, TXA administration, and administration of uncrossmatched blood. Click here to check it out. The Australian tool is much more robust with more data points that make a lot of sense. You can download a copy by clicking here.

Tomorrow, I’ll continue with activation criteria for the MTP.

And don’t forget to subscribe to TraumaMed if you want to get a full newsletter discussing advanced MTP topics this Friday. Otherwise, you’ll be reading a post on CT scans and rib fractures in the elderly! Subscribe and download back issues by clicking here.

Links: (note – future links will not be live until 9am the day they are published)

Laboratory, Resuscitation

MTP Week Part 2: How To Build Your Massive Transfusion Protocol

January 29, 2019 The Trauma Pro Leave a comment

MTP logistics include details such as who will be delivering the blood, what actually goes in each cooler, what ratios should be used, limitations imposed by the use of frozen plasma, and documentation. I’ll discuss details about ratios and FFP in the next Trauma MedEd newsletter.

The runners who travel between blood bank and the patient need to be selected carefully. Blood bank tech? Not ideal because they’ve got more important work to do. ED or OR tech? Maybe, as long as you’ve got a reliable pool. Student or resident? Probably not, because they may not know their way to the blood bank, which are typically placed in the farthest corner of the basement as possible. One of the most creative solutions I’ve seen is the use of a hospital security officer. Think about it. They know the hospital layout cold, including that obscure corner where the blood bank is located. And there are plenty around all the time!

Documentation is critically important, both in the trauma bay and the blood bank. Trauma activations, especially ones requiring MTP, are very fast moving and complex. Two sets of documentation are crucial: accurate records of blood product administration (on the trauma flow sheet), and documentation of just about everything else (in the blood bank). A specific timestamp on the trauma flow sheet that records the exact time of activation of MTP is a big plus.

What about coolers? I’ve seen everything used from uninsulated plastic buckets, picnic coolers, and pneumatic tube containers to large, self-contained rolling refrigeration units. The choice of container really boils down to cost vs waste. The cheaper it is, the less insulated it is, the more likely that blood products will be discarded due to high temperature if not transfused promptly. The best blend of cost vs utility seems to be the good, old-fashioned picnic cooler. It’s very portable, reasonably cheap, and can be tested for temperature maintenance. Just be sure to secure a pouch to the outside to keep platelets at room temperature to maintain full functionality.

Here’s a sample MTP cooler that’s ready for use. The platelets are in the pouch on the left. Note the reminder to prompt the team to give TXA if not contraindicated. This is often forgotten in the heat of the trauma activation.

Who actually runs your MTP? In some ways, it should run itself. Coolers get delivered, products get transfused. However, some decision making is needed to decide how long to continue and whether any tweaking of product ratios needs to happen. In the emergency department, the surgeon or emergency physician can do this. But once a trauma patient arrives in the OR, that is no longer the case. The emergency physician was left behind in the ED and the surgeon is up to her elbows in trouble. What about the anesthesiologist? Nope, they are busy keeping the patient safely asleep, regulating rapid infusions, and actually administering the blood.

Most of the time, however, these two physicians actually end up running the MTP while multi-tasking at their other job. Unfortunately, this can lead to errors and delays. One best practice to consider: a highly trained trauma resuscitation nurse or advanced practice provider (APP) can run the MTP from the sidelines. They travel with the patient from ED to OR, managing the MTP the entire time. This offloads responsibility from busier people.

Tomorrow, I’ll continue with MTP deactivation and analysis.

Links: (note – future links will not be live until 9am the day they are published)

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