Triage: START and STM

~ soovinyoon

In the aftermath of the mass-casualty incidents(MCIs), there is a sudden increase in demand for emergency services. As resources(like ambulance vehicles, medical staffs,..) are limited,  even the patients in critical condition may have to wait before receiving care, therefore limited medical resources need to be rationed efficiently. This process is called triage. Patients are classified into triage classes given the severity of the patient’s medical condition. Those in the most severe classes are treated first, and the less severe groups wait until treated afterwards.

The most commonly adopted triage process in United States is Simple Triage and Rapid Treatment (START). START classifies patients into following four different classes:

  1. Immediate: deemed to be critically injured and to require immediate intervention
  2. Delayed: injured byt not expected to die within the first hour if case is delayed
  3. Expectants: presumed deceased or have catastrophic injuries, and survival is not expected.
  4. Minor: can walk away

After patients are classified, START gives the highest priority to immediates, then to delayed. Expectants and Minors are served after two time-critical classes are cleared.

This is a simple and easy-to-implement prioritization scheme. But there have been a number of literatures indicating limitations of START method and similar methods, like

  • There is no consideration for resource availability.
  • A tacit assumption is that there is no deterioration.
  • A worst-first strategy make poor use of scarce resources. More salvageable victims could be left to deterioratee while limited resources are being used on patients with less chance of survival.

In particular, Sacco et al(2005,2007) proposed the Sacco Triage Method (STM) to overcome these drawbacks. They set up a mathematical formulation of resource-constrained triage to maximize the expected number of survivors, subject on the timing and availability of transport and treatment resources. The model also need predictions of survival probability and changes in it over time (deterioration). Their formulation fits Linear Programming framework, so the problem can be solved efficiently for large-scale MCIs.

From their computation result, STM provided higher number of expected survivors than did START in all of the simulations. STM appeared to mitigate the impact of declining resources when there is a resource change, whereas START dramatically drops in survivorship.

In my presentation on Thursday, I will introduce another, a very different approach to resource-based patient prioritization.

Soovin

References:

  • Argon NT, Winslow JE, Ziya S (2011) Triage in the aftermath of mass-casualty incidents. Wiley Encyclopedia of Operations Research and Management Science.
  • Sacco WJ, Navin DM, Fiedler KE, Waddell RK, II, Long WB, Buckman Jr RF (2005) Precise formulation and evidence-based application of resource-constrained triage. Acad. Emergency Medicine.
  • Sacco WJ, Navin DM, Waddell RK, Fiedler KE, Long WB, Buckman RF (2007) A new Resource-Constrained triage method applied to victims of penetrating injury. J. Trauma: Injury, Infection, Critical Care.
  • Uzun Jacobson E, Argon NT, Ziya S (2012) Priority assignment in emergency response. Oper. Res.

4 thoughts on “Triage: START and STM”

  1. As someone who has worked on an emergency department simulation before, I found this really interesting.

    I did have one question, though. Did the authors discuss what happens to the patients with “less chance of survival”? Do they just determine that the patient will be too hard to save and provide them with what more or less amounts to “hospice” care? While the results show that will improve the overall number of survivors, I just wonder how a patient’s family members would react to that kind of an approach.

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    1. I think that’s a good point. When responders are overwhelmed by the sudden increase of patients, although it can’t be a desirable thing to give up serving some patients just because they have less chance of survival, some kind of choice should be made after all … I guess that’s the essence of triage, a process of determining who to serve(equivalently who to not serve now) when it is forced to make the decision.

      There also could be some argument about where we draw the lines between the patients we serve immediately because their condition is severe and the patients we serve later because their condition is ‘too’ severe. OR can treat this problem, but at the level when there’s not enough data given to make OR decision, I think this often seems to be more of a medical question than an OR one.

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