Mathematical estimation of victim severity distribution in nerve-agent mass casualty incidents.

De Rouck, R. (Speaker), Debacker, M. (Contributor), Hubloue, I. (Contributor)

Activiteit: Talk or presentation at a conference


Introduction: Recent events with public usage of chemical warfare agents have highlighted the importance of chemical disaster preparedness, to which resource estimation is paramount. Mathematical modeling systems for casualty estimation already exist for military purposes, as reported in the AMedP-7.5 and AMedP-8C publications. This methodology was applied to the general population for victim estimation in a civilian chemical mass casualty incident. Sarin gas was used as an exemplary agent due to the large amount of available evidence for clinical course and treatment, based on human and animal exposures. Methods: The AMedP-7.5 mathematical model and AMedP-8 victim profile for casualty distribution calculation, were adapted for the general population using the methodology described originally by Crosier & Sommerville. Using the parameters obtained, severity estimations were assigned using the NATO Triage system which is divided in 3 main categories: T3 (= green) representing the least severe category, T2 (orange) representing moderate symptoms and T1 (= red) representing severely injured victims. Triage was assumed to take place in between 30 and 90 minutes after exposure, using signs and symptoms expected during this period. Untreated victims with lethal injuries are presumed to have died in this period. Victims triaged as T1 are severely injured and require airway management and antidote treatment, while T2 victims are able to support their own breathing. T3 victims mainly have ocular symptoms and slightly to no respiratory compromise. Three exposure levels were selected for further analysis, representing mild, moderate and severe exposures, adapted from AMedP-7.5. These exposure levels assume a normal sized adult of 70kg. Results: Calculated exposure values were 0.81, 16.9 and 22.3 mg.min.m-3 for mild, moderate and severe exposures respectively. Mild exposures will result in 18.1% unaffected individuals and 81.9% T3 victims, having no T2 or T1 victims. Moderate exposures will result in 0.3% T3 victims, 84.2% T2 victims, 8.5% T1 victims and 7.0% deaths on site. Severe exposures will result in no T3 victims, 59.1 T2 victims, 16.4% T1 victims and 24.4% deaths on site. Discussion: Hospital capacity estimation is usually done using an assumed relationship between T1, T2 and T3 victims, based on earlier experiences in traumatic mass casualty incidents. A commonly cited distribution in Belgium is 4-2-1, meaning 4 T3s and 2 T2s for every T1. This mathematical modeling exercise casts doubts on the applicability of these rules-of-thumb and suggest the need for flexibility. While in this exercise Sarin was used as the principal chemical agent, other agents can be modeled by adapting the parameters. This approach uses a one-size-fits-all approach and assumes equal exposure throughout the population. Caution should be used when extrapolation these results to selected populations such as children or elderly, as they are assumed to be more severely affected. Conclusion: Victim severity distribution during chemical incidents can vary from a large percentage of mildly intoxicated victims, to a high number of victims requiring intensive treatment, depending on their intoxication level. Hospitals should include for both extremes in their hospital disaster plan.
Periode19 sep 202022 sep 2020
EvenementstitelEUSEM 2020: European Congress on Emergency Medicine
Mate van erkenningInternational