Public Health Emergency Preparedness

Chapter 6. Sarin

This chapter describes the assumptions for the sarin 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.

6.1. Severity Categories

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

1. Mild: Miosis, ocular pain, tearing, rhinorrhea, bronchospasm, slight dyspnea, respiratory secretions, salivation, diaphoresis.
2. Moderate: Moderate dyspnea, nausea, vomiting, diarrhea.
3. Severe: Loss of consciousness, convulsions, paralysis, copious secretions, apnea.

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: Miosis, ocular pain, tearing, rhinorrhea, bronchospasm, slight dyspnea, respiratory secretions, salivation, diaphoresis	95.4%
Moderate: Moderate dyspnea, nausea, vomiting, diarrhea	3.6%
Severe: Loss of consciousness, convulsions, paralysis, copious secretions, apnea	1.0%

This breakdown by casualty condition is based on work performed during development of the original Surge Model in 2005. In brief, the modeled sarin attack is based upon a release of the agent indoors in a theater. We used air exchange rates to estimate exposure both within the theater and to pedestrians nearby who were exposed to sarin released from the exhaust vents. Individuals who were nearby in the attack were considered partially protected if they were in a building but unprotected if outdoors. Initially, four categories of condition were estimated: mild, moderate, or severe symptoms, or death,. However, in the largest attacks, all those directly exposed to the attack would receive a lethal dose, and those outdoors would receive only enough to illicit mild symptoms.

6.2 Casualty Arrival Pattern

For the sarin scenario, all casualties are assumed to present at the hospital(s) on Day 1.

6.3 Length of Stay By Hospital Unit

The assumed average length of stay (in days) of patients the ED, ICU, and the floor^6,13 are:

Average Length of Stay by Hospital Unit	Irritated	Moderate	Severe
ED	1	1	1
Floor, not via ICU	1	2	7
Floor, via ICU	1	2	7
ICU	1	2	7

 

6.4 Combined Path Probabilities and Lengths of Stay

The table below shows the assumed probabilities of different "paths" through the hospital(s). The table shows, for example, that a patient presenting with severe sarin exposure has a 50 percent chance of dying in the ED prior to transfer to the ICU.

Path	Irritated	Moderate	Severe
ED → Discharge	50%	15%	0%
ED → Death	0%	0%	0%
ED → Floor → Discharge	50%	63%	0%
ED → Floor → Death	0%	0%	0%
ED → Floor → ICU → Death	0%	0%	0%
ED → Floor → ICU → Floor → Discharge	0%	7%	0%
ED → Floor → ICU → Floor → Death	0%	0%	0%
ED → ICU → Death	0%	0%	0%
ED → ICU → Floor → Discharge	0%	15%	100%
ED → ICU → Floor → Death	0%	0%	0%

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

Average Length of Stay by Patient Outcome	Irritated	Moderate	Severe
Survivors	1.50	3.24	15.00
Fatalities	0.00	0.00	0.00
Average Combined	1.50	3.24	15.00

6.5 Overall Outcome Probabilities

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

Outcome	Irritated	Moderate	Severe
Discharge	100%	100%	100%
Death	0%	0%	0%

6.6 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	Lambdaa	Moderate			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	0.042	0.042	0	0.083	0.083	0
Critical care nurses (CCN)	FTE	Staff	CCN	1	0.083	0.33	0	0.083	0.33	0
Surgeons	FTE	Staff	Surgeon	0.3	0	0	0	0	0.083	0
Non-intensivists (MD)	FTE	Staff	MD	0.9	0.083	0	0.021	0.083	0	0.021
Non-critical care nurses (RN/LPN)	FTE	Staff	RN	1	0.33	0	0.33	0.33	0	0.33
Respiratory therapists (RT)	FTE	Staff	RT	0.7	0.083	0.083	0.042	0.083	0.083	0.042
Radiology machines	Machine Time	Lab/Radiology	Radiology	0.3	0.021	0.021	0	0.021	0.021	0
Radiologic technicians	FTE	Staff	Rad Tech	0.3	0.021	0.021	0	0.021	0.021	0
Pharmacists (PharmD/RPh)	FTE	Staff	Pharmacist	0.7	0.021	0.042	0.042	0.021	0.042	0
Mechanical ventilator	Machine Time	Capacity	Ventilator	0.9	0	1	0	1	1	0
Ventilator equipment	One Ventilator	Equipment	Vent Tubing	0.9	0	1	0	1	1	0
Oxygen (O2)	24h O2 for Vent	Supplies	Oxygen	0.9	1	2	1	2	2	1
Oxygenation monitoring equipment	Machine Time	Equipment	O2 Monitoring	0.9	0.083	1	0	0.083	1	0.5
Surgical supplies	Trauma Set	Supplies	Surgical	0.3	0	0	0	0	0.25	0
Radiology supplies	Radiographic Film	Supplies	Radiological	0.3	1	1	0	1	1	0
Ciprofloxacin 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
Antibiotics for secondary pneumonia	Assorted	Pharmacy	Antibiotics	1	0	0	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	0	0	0
Antibiotics intravenous infusion set	One IV Piggyback	Supplies	IV set	1	0	0	0	0	0	0
Hemodynamic medications	Assorted	Pharmacy	Hemodynamic	0.7	0	0	0	1	1	0
Intravenous fluids	24h LR or equiv.	Pharmacy	IVF	0.7	0	0	0	1	1	0
Intravenous infusions set	One IV Set	Supplies	IV Set	0.7	0	0	0	1	1	0
Laboratory machines	Machine Time	Lab/Radiology	Laboratory	0.7	0.021	0.021	0.021	0.021	0.021	0.021
Laboratory supplies	CBC/CMP Reag.	Supplies	Laboratory	0.7	1	1	0.05	1	1	0.05
Temperature monitoring equipment	Machine Time	Equipment	Temperature	1	0.083	1	1	0.083	1	1
Thromboembolism prophylaxis	Enoxaparin 40mg sc qd	Pharmacy	DVT Prophylaxis	1	0	1	1	0	1	1
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	1	0	0	1	0	0
Radiological PPE	Level D	PPE	Radiological	0.3	0	0	0	0	0	0
Waste disposal	Level D	PPE	Decon Waste	0.3	1	0	0	1	0	0
Mortuary decontamination materials	Level D	PPE	Mortuary	0.3	0	0	0	0	0	0
Atropine sulfate	2mg	Pharmacy	Atropine	0.1	2	2	0	3	3	0
Pralidoxime	2g	Pharmacy	Pralidoxime	0.1	2	2	0	2	2	0
Diazepam	10mg	Pharmacy	Diazepam	0.1	1	1	0	2	2	0
EEG	Machine Time	Equipment	Chemical	0.1	1	1	1	1	1	1
IV steroids	Hydrocortisone 50mg IV q6h	Pharmacy	Steroids	0.7	0	0	0	0	0	0
DPTA	1g IV	Pharmacy	DPTA	0.1	0	0	0	0	0	0
Prussian blue	3mg po tid	Pharmacy	Prussian Blue	1	0	0	0	0	0	0
Growth factors	Pegfilgrastim 6mg sc qw	Pharmacy	Growth factors	1	0	0	0	0	0	0
Stem cell transfusion	Unit of Use	Heme/Onc	Stem Cell Trans	1	0	0	0	0	0	0
Geiger counter	Machine Time	Equipment	Radiation	0.1	0	0	0	0	0	0
Enteral feedings (3/day/patient)	Unit of Use	Nutrition	Enteral	1	0	0.5	0	0	0.5	1
Oral food (3 meals/ day/ patient)	Unit of Use	Nutrition	Oral	1	0	0.5	1	0	0.5	1
Sheet change	1 linen change	House-keeping	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	0.083	0.042
Engineering	FTE	Engineering	Facility	0.7	0.042	0.083	0.042	0.042	0.083	0.042
Janitorial/Housekeeping	FTE	House-keeping	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	0	0	0

^a 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.

6.7 References

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