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:

1. Mild:  1Gy equivalent dose for blood effects, no other equivalent dose (some bleeding and infection issues).
2. 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 References

1. Barrett JA. SRP meeting on radiological terrorism: prevention and response. J Radiol Prot 2004;24(3):331-2.

2. Elcock D, Klemic GA, Taboas AL. Establishing remediation levels in response to a radiological dispersal event (or "dirty bomb"). Environ Sci Technol 2004;38(9):2505-12.

3. Koenig KL, Goans RE, Hatchett RJ,et al. Medical treatment of radiological casualties: Current concepts. Ann Emerg Med 2005;45(6):643-52.

4. Moulder JE. Post-irradiation approaches to treatment of radiation injuries in the context of radiological terrorism and radiation accidents: a review. Int J Radiat Biol 2004;80(1):3-10.

5. Norwood WD. Radiation casualties: emergency plans and medical care. Arch Environ Health 1971;23(2):129-34.

6. Schleipman AR, Gerbaudo VH, Castronovo FP, Jr. Radiation disaster response: preparation and simulation experience at an academic medical center J Nucl Med Technol 2004;32(1):22-7.

7. Shoikhet YN, Kiselev VI, Zaitsev EV, et al. A registry for exposure and population health in the Altai region affected by fallout from the Semipalatinsk nuclear test site. Radiat Environ Biophys 1999;38(3):207-10.

8. Turai I, Veress K, Gunalp B, et al. Medical response to radiation incidents and radionuclear threats. BMJ 2004;328(7439):568-72.

9. Waselenko JK, MacVittie TJ, Blakely WF, et al. Medical management of the acute radiation syndrome: recommendations of the Strategic National Stockpile Radiation Working Group. Ann Intern Med 2004;140(12):1037-51.

10. World MJ. Casualties resulting from nuclear explosion: an overview. J R Army Med Corps 2004;150(3 Suppl 1):3-4.

Return to Contents
Proceed to Next Section