Chapter 8. Radiological Dispersal Device (RDD)
This
chapter describes the assumptions for the RDD 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.
8.1 Severity
Categories
For the RDD
scenario, patients arrive at the hospital(s) in one of two conditions:
- Mild: 1Gy equivalent dose for blood
effects, no other equivalent dose (some bleeding and infection issues).
- Severe: 4Gy for blood effects
(problems with bleeding and infection) and about 0.75 Gy for lethality and
GI effects (some small fraction of people will die and others get nausea,
vomiting, etc.).
Users have
the option of specifying either the number and type or simply the
number of casualties who present at their hospital(s).
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 follow:
Casualty
Condition
|
Percent
|
Mild: 1Gy equivalent dose for blood
effects, no other equivalent dose (some bleeding and infection issues) |
99.5% |
Severe: 4Gy for blood effects (problems
with bleeding and infection) and about 0.75 Gy for lethality and GI effects
(some small fraction of people will die and others get nausea, vomiting,
etc.) |
0.5% |
This
breakdown by casualty condition is based on work performed during development
of the original Surge Model in 2005. In brief, in this scenario we focus on the
casualties from dispersed radiation rather than the few casualties from the
explosive force of the device.
First, we used plume modeling to estimate the
number of individuals exposed to different levels of radioactive particles
depending on their distance from the point of dispersal. Based upon amount of
particles inhaled and the half-life within the human body, we then calculated
the dose accumulated by day for the first 60 days after an attack for each of
four categories of exposure. Radiation can cause many ill effects, including
gastrointestinal effects and damage to the blood. Each of these effects occurs
at different likelihoods over time, with blood effects manifesting later than
GI effects.
We categorized as severe the percentage of people in each exposure
category who would likely show severe effects of the blood or GI tract, while
mild symptoms were found in individuals with mild GI or blood effects. Because
individuals are expected to present to the hospital when they first show
symptoms (especially after a known attack), it is assumed that only those
individuals highly affected on the first day will already have reached severe
symptoms before arriving at the hospital.
8.2. Casualty
Arrival Pattern
Casualties
are assumed to present at the hospital(s) when symptoms appear. For this
scenario, we used available data on radiation effects at low doses in humans.
This showed the probability of having blood, gastrointestinal, or mental
effects of radiation and the number of days after exposure at which each of
these symptoms would first manifest. Blood effects tend to appear several days
after GI effects, and people with lower exposures present later than those with
higher exposures.
8.3 Length of
Stay By Hospital Unit
The assumed
average length of stay (in days) of patients the ED, ICU, and the floor (based
on references no. 3,5, 6, and 10 listed at the end of this section) are:
Average
LOS by Hospital Unit
|
Mild
|
Severe
|
ED |
1 |
1 |
Floor, not
via ICU |
1 |
7 |
Floor, via
ICU |
2 |
14 |
ICU |
1 |
28 |
8.4 Combined
Path Probabilities and Lengths of Stay
The table
below shows the assumed probabilities of different "paths" through the
hospital(s).
Path
|
Mild
|
Severe
|
ED → Discharge |
0% |
0% |
ED → Death |
0% |
0% |
ED → Floor → Discharge |
75% |
7% |
ED → Floor → Death |
0% |
1% |
ED → Floor → ICU → Death |
0% |
1% |
ED → Floor → ICU → Floor → Discharge |
0% |
1% |
ED → Floor → ICU → Floor → Death |
0% |
0% |
ED → ICU → Death |
0% |
43% |
ED → ICU → Floor → Discharge |
25% |
40% |
ED → ICU → Floor → Death |
0% |
7% |
The
breakdown of length of stay by patient type summed over all paths is:
Average LOS by Patient Outcome
|
Mild
|
Severe
|
Survivors |
2.49 |
38.33 |
Fatalities |
2.65 |
17.03 |
Average
Combined |
2.49 |
27.27 |
8.5 Overall
Outcome Probabilities
Based on
these inputs (and references no. 3,5, 6, and 10 listed at the end of this section), the overall
discharge and death probabilities* are:
Outcome
|
Mild
|
Severe
|
Discharge |
100% |
48% |
Death |
0% |
52% |
*Note: These figures do not include
late (>2 months) mortality from radiation exposure)
8.6 Resources
Consumed Per Patient Per Day
The assumed
level of resource consumption per patient per day is shown in the table below:
Resource
|
Units
|
Category
|
Subcategory
|
Lambda1
|
Mild
|
Severe |
ED |
ICU |
Floor |
ED |
ICU |
Floor |
Med/Surg Bed |
One Bed |
Capacity |
Floor |
1 |
0.083 |
0 |
0 |
0.083 |
0 |
0 |
ICU Bed |
One Bed |
Capacity |
ICU |
1 |
0 |
1 |
0 |
0 |
1 |
0 |
Burn Bed |
One Bed |
Capacity |
Burn |
1 |
0 |
0 |
0 |
0 |
0 |
0 |
Operating Room |
One OR Suite |
Capacity |
OR |
1 |
0 |
0 |
0 |
0 |
0 |
0 |
Airborne Isolation Room |
One Bed |
Capacity |
Isolation |
0.9 |
0 |
0 |
0 |
0 |
0 |
0 |
Intensivists (CCM) |
FTE |
Staff |
CCM |
0.7 |
0.021 |
0.083 |
0 |
0.083 |
0.083 |
0 |
Critical care nurses (CCN) |
FTE |
Staff |
CCN |
1 |
0.021 |
0.33 |
0 |
0.083 |
0.33 |
0 |
Surgeons |
FTE |
Staff |
Surgeon |
0.3 |
0 |
0.042 |
0 |
0 |
0.042 |
0 |
Non-intensivists (MD) |
FTE |
Staff |
MD |
0.9 |
0.083 |
0 |
0.042 |
0.083 |
0 |
0.042 |
Non-critical care nurses (RN/LPN) |
FTE |
Staff |
RN |
1 |
0.042 |
0 |
0.146 |
0.042 |
0 |
0.146 |
Respiratory Therapists (RT) |
FTE |
Staff |
RT |
0.7 |
0 |
0.042 |
0 |
0.083 |
0.083 |
0 |
Radiology machines |
Machine Time |
Lab/Radiology |
Radiology |
0.3 |
0 |
0.021 |
0 |
0 |
0.021 |
0 |
Radiologic Technicians |
FTE |
Staff |
Rad Tech |
0.3 |
0 |
0.021 |
0 |
0 |
0.021 |
0 |
Pharmacists (PharmD/RPh) |
FTE |
Staff |
Pharmacist |
0.7 |
0.021 |
0.042 |
0.042 |
0.021 |
0.042 |
0.042 |
Mechanical ventilator |
Machine Time |
Capacity |
Ventilator |
0.9 |
0 |
0 |
0 |
0 |
0 |
0 |
Ventilator equipment |
One Ventilator |
Equipment |
Vent Tubing |
0.9 |
0 |
0 |
0 |
0 |
0 |
0 |
Oxygen (O2) |
24h O2 for Vent |
Supplies |
Oxygen |
0.9 |
0 |
1 |
0 |
0 |
1 |
0 |
Oxygenation monitoring equipment |
Machine Time |
Equipment |
O2 Monitoring |
0.9 |
0.083 |
1 |
0 |
0.083 |
1 |
0 |
Surgical supplies |
Trauma Set |
Supplies |
Surgical |
0.3 |
0 |
0 |
0 |
0 |
0 |
0 |
Radiology supplies |
Radiographic Film |
Supplies |
Radiological |
0.3 |
0 |
1 |
0 |
0 |
1 |
0 |
Cirprofloxacin or Doxycycline |
400mg/100mg bid |
Pharmacy |
Antibiotics |
1 |
0 |
0 |
0 |
0 |
0 |
0 |
Rifampin or other 2nd line agent |
600mg po bid |
Pharmacy |
Antibiotics |
1 |
0 |
0 |
0 |
0 |
0 |
0 |
Antibiotcs for Secondary Pneumonia |
Assorted |
Pharmacy |
Antibiotics |
1 |
0 |
1 |
0 |
0 |
1 |
0 |
Surgical Infection Prophylaxis/Treatment |
Assorted |
Pharmacy |
Antibiotics |
1 |
0 |
0 |
0 |
0 |
0 |
0 |
Neutropenia Prophylaxis/Treatment |
Assorted |
Pharmacy |
Antibiotics |
1 |
0 |
0 |
0 |
1 |
1 |
1 |
Antibiotics intravenous infusion set |
One IV Piggyback |
Supplies |
IV set |
1 |
0 |
0 |
0 |
1 |
0.5 |
0.5 |
Hemodynamic medications |
Assorted |
Pharmacy |
Hemodynamic |
0.7 |
0 |
1 |
0 |
0 |
1 |
0 |
Intravenous fluids |
24h LR or equiv. |
Pharmacy |
IVF |
0.7 |
1 |
1 |
1 |
1 |
1 |
1 |
Intravenous infusions set |
One IV Set |
Supplies |
IV Set |
0.7 |
1 |
1 |
1 |
1 |
1 |
1 |
Laboratory machines |
Machine Time |
Lab/Radiology |
Laboratory |
0.7 |
0.042 |
0.083 |
0.042 |
0.083 |
0.166 |
0.083 |
Laboratory supplies |
CBC/CMP Reag. |
Supplies |
Laboratory |
0.7 |
2 |
2 |
2 |
3 |
6 |
3 |
Temperature monitoring equipment |
Machine Time |
Equipment |
Temperature |
1 |
0.083 |
1 |
0 |
0.083 |
1 |
0 |
Thromboembolism prophylaxis |
Enoxaparin 40mg sc
qd |
Pharmacy |
DVT Prophylaxis |
1 |
0 |
1 |
0 |
0 |
1 |
0 |
Urine output monitoring equipment |
Catheter and Bag |
Equipment |
U/O |
1 |
0 |
1 |
0 |
0 |
1 |
0 |
Universal Precautions PPE |
Glove/gown/mask |
PPE |
Universal |
1 |
1 |
1 |
1 |
1 |
1 |
1 |
Chemical PPE |
Level D |
PPE |
Chemical |
0.3 |
0 |
0 |
0 |
0 |
0 |
0 |
Radiological PPE |
Level D |
PPE |
Radiological |
0.3 |
1 |
0 |
0 |
1 |
0 |
0 |
Waste Disposal |
Level D |
PPE |
Decon Waste |
0.3 |
1 |
1 |
1 |
1 |
1 |
1 |
Mortuary Decontamination Materials |
Level D |
PPE |
Mortuary |
0.3 |
0 |
0 |
0 |
0 |
0 |
0 |
Atropine sulfate |
2mg |
Pharmacy |
Atropine |
0.1 |
0 |
0 |
0 |
0 |
0 |
0 |
Pralidoxime |
2g |
Pharmacy |
Pralidoxime |
0.1 |
0 |
0 |
0 |
0 |
0 |
0 |
Diazepam |
10mg |
Pharmacy |
Diazepam |
0.1 |
0 |
0 |
0 |
0 |
0 |
0 |
EEG |
Machine Time |
Equipment |
Chemical |
0.1 |
0 |
0 |
0 |
0 |
0 |
0 |
IV Steroids |
Hydrocortisone
50mg IV q6h |
Pharmacy |
Steroids |
0.7 |
0 |
0 |
0 |
0 |
0 |
0 |
DPTA |
1g IV |
Pharmacy |
DPTA |
0.1 |
1 |
1 |
1 |
1 |
1 |
1 |
Prussian blue |
3mg po tid |
Pharmacy |
Prussian Blue |
1 |
1 |
1 |
1 |
1 |
1 |
1 |
Growth Factors |
Pegfilgrastim 6mg
sc qw |
Pharmacy |
Growth factors |
1 |
0 |
0 |
0 |
0 |
1 |
1 |
Stem Cell Transfusion |
Unit of Use |
Heme/Onc |
Stem Cell Trans |
1 |
0 |
0 |
0 |
0 |
1 |
0 |
Geiger counter |
Machine Time |
Equipment |
Radiation |
0.1 |
0.42 |
0.21 |
0.21 |
0.42 |
0.21 |
0.21 |
Enteral feedings (3/day/patient) |
Unit of Use |
Nutrition |
Enteral |
1 |
0 |
0.5 |
0 |
0 |
0.5 |
0.5 |
Oral food (3 meals per day per patient) |
Unit of Use |
Nutrition |
Oral |
1 |
0 |
0.5 |
1 |
0 |
0.5 |
1 |
Sheet change |
1 linen change |
Housekeeping |
Laundry |
1 |
1 |
1 |
1 |
1 |
1 |
1 |
Patient infection control |
FTE |
Epidemiology |
Infection Control |
0.5 |
0.021 |
0.042 |
0.042 |
0.021 |
0.042 |
0.042 |
Engineering |
FTE |
Engineering |
Facility |
0.7 |
0.042 |
0.083 |
0.042 |
0.042 |
0.083 |
0.042 |
Janitorial/Housekeeping |
FTE |
Housekeeping |
Janitorial |
1 |
0.125 |
0.125 |
0.083 |
0.125 |
0.125 |
0.083 |
Nutrition |
FTE |
Nutrition |
Counseling |
0.5 |
0 |
0.083 |
0.083 |
0 |
0.083 |
0.083 |
Psychological support |
FTE |
Ancillary |
Psychologist |
0.5 |
0 |
0 |
0.042 |
0 |
0 |
0.042 |
Mortuary |
FTE |
Mortuary |
Morgue |
0.1 |
0 |
0.042 |
0 |
0.042 |
0.042 |
0 |
1. Lambda captures the resource requirement decay rate for a resource. Lambda = 1
implies no decay; the patient requires a constant amount of the resource while
s/he is hospitalized. Lambda <1 implies that less of the resource is
required each day the patient is hospitalized. Go to section 2.2 for details.
8.7
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