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Hospital Surge Model Version 1.3: Description

Public Health Emergency Preparedness

This resource was part of AHRQ's Public Health Emergency Preparedness (PHEP) program, which was discontinued on June 30, 2011, in a realignment of Federal efforts.

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Chapter 12. Improvised Explosive Device

This chapter describes the assumptions in the improvised explosive device (IED) scenario, including:

  • The severity categories.
  • The arrival pattern of casualties at the hospital(s).
  • The length of stay by hospital unit (i.e., ED, ICU, and the floor).
  • The path probability within the hospital(s) and the length of stay.
  • The overall outcome probabilities (i.e., probability of discharge and probability of death).
  • The assumed level of resource consumption per patient per day per hospital unit.

Footnotes in the text of a particular section refer to references at the end of the section. In the absence of specific references, parameter estimates were obtained from general references listed in the Hospital Module section.

12.1 Severity Categories

For the IED scenario, patients arrive at the hospital(s) in one of three conditions:

  1. Affected: Victims suffer from one type of blast injuries, including lacerations, fractures, burns, and pulmonary blast.
  2. Moderate: Victims suffer from two types of blast injuries, including lacerations, fractures, burns, and pulmonary blast.
  3. Severe: Victims suffer from three or more types of blast injuries, including lacerations, fractures, burns, and pulmonary blast.

If the user specifies only the number of casualties, the model assumes the casualties arriving at the hospital(s) are randomly selected from among all casualties from the attack. The distribution of casualty types in this case is as follows:

Casualty Condition Percent
Affected: Victims suffer from one type of blast injuries, including lacerations 10%
Moderate: Victims suffer from two types of blast injuries, including lacerations 55%
Severe: Victims suffer from three or more types of blast injuries, including lacerations 35%

This breakdown by casualty condition is based on an analysis of the Madrid and London subway bombings in 2004 and 2005, respectively.

12.2 Casualty Arrival Pattern

All casualties present at the hospital(s) on the day of the attack. Patients are assumed to be taken directly to the ED for triage.

12.3 Length of Stay by Hospital Unit

The assumed average lengths of stay (in days) of patients in the ED, in the ICU, and on the floor are:

Average Length of Stay by Hospital Unit Affected Moderate Severe
ED 1 1 1
Floor, not via ICU 3.6 11.2 13.8
Floor, via ICU 3 3 6
ICU 3.2 6.4 6.4

12.4 Combined Path Probabilities and Lengths of Stay

The table below shows the assumed probabilities of different "paths" through the hospital(s).

Path Affected Moderate Severe
ED → Discharge 0% 0% 0%
ED → Death 0% 1% 7%
ED → Floor → Discharge 91% 64% 26%
ED → Floor → Death 1% 2% 0%
ED → Floor → ICU → Death 1% 0% 1%
ED → Floor → ICU → Floor → Discharge 3% 7% 25%
ED → Floor → ICU → Floor → Death 0% 0% 1%
ED → ICU → Death 1% 1% 2%
ED → ICU → Floor → Discharge 3% 23% 36%
ED → ICU → Floor → Death 0% 0% 2%

The breakdown of length of stay by patient type summed over all paths is:

Average Length of Stay by Patient Outcome Affected Moderate Severe
Survivors 5.18 11.80 15.49
Fatalities 4.04 5.69 5.26
Average Combined 5.15 11.47 14.14

12.5 Overall Outcome Probabilities

Based on these inputs, the overall discharge and death probabilities are:

Outcome Affected Moderate Severe
Discharge 97.1% 94.6% 86.8%
Death 2.9% 5.4% 13.2%

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