Every trauma center verified by the American College of Surgeons Committee on Trauma (ACS-COT) must have a massive transfusion protocol (MTP). The details and logistics of the protocol are up to the individual center. The difficult question is: how is a trauma professional to know that the MTP should be activated?
Sometimes it’s extremely obvious. The patient is very hypotensive. Blood is spurting all over the room. But sometimes it’s more subtle and the need just seems to creep up on you. And frequently, this delays activation and the actual arrival of the blood that is so desperately needed.
I’ve previously written about common triggers for the MTP, including psychic powers, shock index, and ABC index. See the links below to read my MTP week posts. But is one better than the other? The group at Vancouver General Hospital in British Columbia, Canada performed a systematic review of the literature to try to answer this question.
A total of 45 pertinent articles were identified in the literature up to 2017. Fifteen different scoring systems were evaluated involving combinations of clinical assessment, laboratory tests, and ultrasound evaluation.
Here are the factoids:
- The best validated score using clinical assessment plus ultrasound was the Assessment of Blood Consumption score (click here for my post). This was the easiest to score compared to other systems using ultrasound.
- Shock index (SI) was the only validated system using just the clinical exam
- Some other studies were promising, with excellent areas under the receiver operating characteristic curve (AUROC), but had not been validated. The best of the bunch was one from Mina et al, but it is complicated enough to require a smartphone tool for calculation.
- Other promising studies required laboratory evaluations which preclude their use at the time of patient arrival
- Scoring systems that used more variables generally showed better correlation with actual need for MTP, but were more less likely to provide suficiently early predictions
- Most validation studies involved single centers
- No studies were designed to or able to show improved outcomes
Bottom line: There are many, many systems out there for predicting need for activation of the MTP (at least 15 to date)! This review concludes that the system used should be tailored to the center implementing it.
Simpler is better. I still recommend either Shock Index (SI) or ABC. Shock index is quickly calculated based on physical exam as heart rate divided by systolic blood pressure. The normal range is 0.5 to 0.7. The likelihood of MTP escalates 2x with SI > 0.9, 4x if SI > 1.1, and 7x with SI > 1.3. The ratio can easily be calculated based on numbers available from EMS providers prior to arrival. Basically, pick your threshold.
The Assessment of Blood Consumption (ABC) uses four parameters, three of which could be reported prior to patient arrival:
- Heart rate > 120
- Systolic blood pressure < 90
- FAST positive
- Penetrating mechanism
If two or more criteria are met, the patient has a 41% likelihood of needing MTP.
So basically, use a system that works for you. From my experience, centers that use a system tend to use ABC. But definitely pick a system, don’t leave it up to chance with the trauma surgeon. And use your trauma PI program to assess utilization to see if it’s the best tool for your center.
- ABC: a quick and dirty way to predict massive transufsion
- Using shock index to identify risk for massive transfusion
- MTP week part 1 (Monday): Universality and activation
- MTP week part 2 (Tuesday): Logistics
- MTP week part 3 (Wednesday): Documentation and analysis
- MTP week part 4 (Thursday): MTP activation triggers
Reference: Systematic Reviews of Scores and Predictors to Trigger Activation of Massive Transfusion Protocols. Accepted ahead of print, J Trauma, 2019.