Page 41 - Journal of Special Operations Medicine - Spring 2014

of survival affecting a proportionately large cohort of implies the prioritization strategy to be used. These for-
patients. mulas lead to two different methods, which we name
ReSTART and Simple-ReSTART.
Scenario 2. When there are few immediate and few de-
layed patients (region B) and/or relatively ample supply Description of ReSTART and Simple-ReSTART
of ambulances, immediate patients should get priority. For the purposes of the illustrative examples in this re-
This is because transportation resources are not severely port, we assume all the patients will be transported to
restricted compared with the number of patients, which a single hospital (or if there are multiple hospitals, the
makes it possible to attend to the immediate patients travel time to each hospital is approximately the same).
first without significantly compromising the lives of the Both methods make use of the following information to
delayed patients. Thus, the current practice, which pri- determine the prioritization policy:
oritizes immediate patients, works well when transpor-
tation resources are not severely limited. V = total number of transport resources (e.g., ambu-
lances) available for transporting patients.
Scenario 3. When there are not too many delayed pa- R = expected round-trip travel time (between the inci-
tients but a significant number of immediate patients dent location and the hospital).
with respect to the number of available ambulances
(region C), immediate patients should have priority ini- I = number of patients classified as immediate.
tially, but priority should switch to the delayed patients D = number of patients classified as delayed.
at some point in time during the response effort. In this
case, because there are not too many delayed patients, T = the estimated point in time when the survival rate
there is no need to start with the delayed patients. There of the delayed patients begins to decrease faster than the
is some time that can be devoted to the immediate pa- survival rate of the immediate patients.
tients immediately after the incident. However, because
there are relatively a large number of immediate pa- Note that when determining V, a transport resource is a
tients, it is necessary to switch to the delayed patients unit that can transport one patient. If each ambulance
at some point even if there are still immediate patients can transport two patients, then V would be two times
waiting, in order to improve their chance of surviving. the number of ambulances because each ambulance
Continuing to dedicate all resources to immediate pa- would represent two resources. Except for T, estimating
tients will face diminishing returns, as their place on the the above information does not require any extensive
survival curve has continued to descend. At the same effort on the part of providers. Estimation of T is more
time, the deflection point for the survival curve for the difficult, and it is a very important topic for future re-
delayed patients is approaching, and resources should search. Nevertheless, this is a task that should ideally be
be redirected to the delayed patients as in scenario 1. carried out in advance, not on the field, so that T would
be defined prior to the occurrence of a mass-casualty in-
The model depicted in Figure 2 provides a broad descrip- cident. In an actual disaster setting, the triage personnel
tion as to how priorities should be determined but is kept could also use their clinical gestalt based on the type of
intentionally nonspecific due to the many complexities injuries seen to estimate the time at which the delayed
of the patient prioritization problem in practice, some of patients’ survival rate would begin to markedly deterio-
which are difficult or impossible to quantify mathemati- rate as compared to the immediate patients while wait-
cally. Thus, Figure 2 could be useful in providing a model ing for transport. Given the variety of injuries and types
for guiding decisions in the field, but it cannot replace of disasters this may be the only realistic way to estimate
triage personnel, who will be able to assess the overall T. To get a better understanding of the time T, see Figure
situation much better, interpret the model’s suggestions, 1. As indicated on the figure, T is the time point at which
and override them as he or she sees fit. However, it is the rate of decline for the delayed patients surpasses the
possible to extend the analysis and make the model more rate of decline for the immediate patients.
specific by providing precise definitions for “many” de-
layed patients and “many” immediate patients relative to The only calculation needed to determine the priority
the availability of transport, and when exactly to switch policy is S = T – DR .
priorities from the immediate to the delayed (if at all). It 2V
is clear that more research is needed to define these in a
way that is scientifically credible. However, as a proof of (An online tool that can perform the above calculation
concept for how Figure 2 can be helpful in practice, we can be found at http://www.restarttriage.com/. A mo-
derived simple formulas using our mathematical analysis bile web site that can perform the same calculation can
that can be used to determine in which of the three re- be found at http://bit.ly/ZR7667 or by scanning the QR
gions a given mass-casualty situation lies, which in turn code found in Figure 3.) Even though we are making

ReSTART: Resource-Based Triage in Mass-Casualty Events 33