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radiation_emergencies

Radiation emergencies

Summary

  • a person or object exposed to radiation does not make them radioactive
  • a person or object contaminated by radioactive material whether on the skin or ingested, does become radioactive, although the risk to others is very small if adequate precautions are taken
  • minimise radiation dose by:
    • minimise duration of exposure
    • keep your distance
    • avoid getting contaminated by wearing protective clothing - lead aprons are NOT helpful for gamma rays
  • 3 types of radiation detectors in hospitals:
    • area radiation monitor at entrances - only for significant gamma ray sources
    • RADOS personal monitors - keeps track of accumulated dosage & dose rates
      • if alarms, then dose rate too high, rotate staff to minimise exposure
    • Cypher contamination monitor - used to measure contamination levels on parts of a person
      • ensure it does not get contaminated itself by using a glove over it & holding it 2cm from skin and above it so that dust will not drop onto the probe.
      • initially this will be used in the external control area to triage & assess decontamination measures
      • later this will be used in ED treatment area to survey patients who have bypassed decontamination due to medical condition and also to assess staff
      • finally this will be used in the survey of cleaning process & waste management in any potentially contaminated areas within hospital such as ED and theatre
  • medical emergency stabilisation has higher priority than radioactive decontamination.
  • try to minimise clean up operations by protecting the room and keeping contaminants contained in waterproof plastic bags.

Possible scenarios:

  • terrorism:
    • intentional dispersion of radioactive materials using conventional explosives creating a contamination “nuisance”
    • deliberate introduction of radioactive substances into essential services such as major water supplies or food chains creating a scare but radiation doses would be negligible
    • exposure of small numbers of people to a highly radioactive source resulting in clinical effects after a few hours to a few days

Basic principles of radiation protection:

minimise time of exposure:

  • dose is proportion to time exposed
  • do not spend unnecessary time in an area of elevated radiation levels

maximise distance from source:

  • dose is inversely proportion to the square of the distance thus dose rate at 3m is 1/9th that at 1m from source

shielding:

  • type of shielding needed depends on radiation type
  • should not interfere with provision of medical aid to casualties

Victorian radiation emergency response:

  • involves all agencies
  • Vic. Govt Dept. Human Services (DHS):
    • regulates the use of radioactive sources & radiation equipment through Part 5 of the Health Act & the Health (Radiation Safety) Regulations
    • under the Emergency Management Act 1986, DHS is the control agency for incidents involving radioactive material
  • Radiation Safety Program (RSP):
    • radiological response role:
      • contact & response:
        • contact DHS EHU on ph: 13 2222, #87457 to contact RSP officers
        • RSP officers are on 24hr call & have a fully equipped vehicle
        • RSP is able to provide initial advice over the phone prior to attending at a radiation emergency & will be able to attend in about 30min in the case of most metropolitan areas
    • restoration of radiological safety:
      • measurement of radiation levels
      • localisation of distinct radioactive sources (pre-explosion) and areas of contamination (post-explosion)
      • retrieval of distinct sources & supervise clean up of contaminated areas
      • establishment of hot, warm & cold zones with police assistance
      • safety perimeter set where level is < 0.1mSv/hr
      • control points to be up-wind of the source
      • control point at the safety perimeter to ensure access to & from zone is limited and decontamination is controlled
      • a more distant access control point to act as a staging area & command post
      • advice on decontamination - personal (may be via MFB/CFA), onsite & off-site
      • assistance with counselling of exposed or contaminated persons
  • MFB / CFA
  • police
  • ambulance
  • medical DISPLAN
  • hospitals:
    • critically ill are managed in ED resus without need for prior decontamination procedures
    • medically stable patients are checked for radiological contamination & if contaminated are decontaminated prior to entering “Clean” area in hospital

Radiation monitoring equipment for hospitals:

area radiation monitors:

  • selected hospitals will have 2 of these monitors, one for ambulatory entrance and one for ambulance entrance to the ED
  • designed to alarm upon the entry of a hazardous radioactive source into the ED, eg. as shrapnel embedded in a patient
  • will not usually detect radioactive contamination on pts entering ED unless they stand for more than 2 secs near the probe.
  • only detects gamma radiation with measurement range of 1microSv/hr to 5mSv/hr
  • wall mountable with separate detector probe with cable >3m that can also be used to scan patients
  • AC powered with rechargeable battery backup
  • audible alarm 90dba at 30cm (can turn volume down by rotating plastic wheel over the speaker to muffle it)
  • visible red flashing light alarm
  • alarm able to be set to any point on measurement scale
  • what do do if alarm goes off:
    • ask patient who set alarm off if have been to nuclear med (eg. for bone scan, V/Q scan) recently, if so, just turn alarm off and ignore
    • if unable to determine who set alarm off, can use the probe to scan each person - ensure probe does not touch anything to avoid it being contaminated (can use a glove over it if contamination is a possibility)
    • if person sets alarm off and has not had a nuclear med exam recently or reasonable explanation for the radiation, then contact senior staff to consider activating the radiation emergency response as above.
    • NB. the NUM has an operation manual for this device.

RADOS personal monitors:

  • DHS supplies 2 per hospital to be worn by key hospital personnel treating contaminated pts
  • detects gamma radiation
  • measures both dose rate & accumulated dose
  • normal background level is 0 microSv/hr, set to alarm at 100 microSv/hr
  • slow response time - up to 20secs 
  • time to receive dose of 20mSv (ie. 1000 CXR's) = 200hrs if 100 microSv/hr ie. 8days 8hrs
  • usage:
    • long press to turn monitor on
    • 4 short presses to get to CLR
    • long press displays accumulated dose (flashing)
    • long press zeroes accumulated dose, monitor then reverts to dose rate mode after ~8secs
    • in dose rate mode:
      • long press displays accumulated dose (flashing)
      • 2 short presses to get to OFF, then one long press turns monitor off

Cypher contamination monitor:

  • DHS supplies 1 monitor per hospital to be used by hospital health physicist or RSO to detect radiological contamination on patients

detects alpha, beta & gamma radiation

  • typical background reading is 0-2 counts per second (cps) in which case a reading > 6 cps indicates contamination
  • cut-off level for contamination is different if background reading is higher than 2cps - ask RSP
  • usage:
    • connect probe to monitor
    • press power button on, monitor goes to cps mode after a couple of “test displays”
    • the up-arrow button toggles audio on & off
    • remove plastic cover on probe
    • place probe in surgical glove to avoid contamination of probe (will not detect alpha rays when glove on)
    • holding probe ~2cm from pt skin, systematically survey the entire body from head to toe on all sides, moving the probe slowly at a few cm per second
    • do not let the probe touch anything - if it gets contaminated you will get false readings!
    • try to maintain a constant distance & pay particular attention to hands, face & feet

additional accessories supplied by DHS:

  • warning signs
  • barricade tape

Pre-hospital care of casualties:

  • medical problems take priority over radiological concerns
  • medical triage principles are the same regardless of contamination
  • do not delay rescue or transport of a seriously injured, contaminated patient
  • remove victims from the exposure area once stabilised
  • radiological triage to determine contamination status

Transport of contaminated casualties:

  • remove contaminated outer clothing
  • place casualty on a clean sheet on the stretcher
  • fold the sheet over the casualty to form a “package” to contain any remaining contamination
  • advise hospital of presence of contamination
  • transport
  • ambulance personnel & vehicle must be “cleared” before departing hospital

Hospital treatment area:

  • establish controlled area with temporary barriers, signs & security staff
  • cover floor of controlled area and tape in place to enable cleaning afterwards to be easier - don't delay medical Rx if not done.
  • large bins with plastic liners for waste
  • sufficient plastic bags for samples
  • remove or cover non-essential equipment from controlled area
  • establish control lines & monitor anyone or anything leaving the controlled area

PPE for hospital staff:

  • gown & waterproof apron
  • cap
  • waterproof shoe covers
  • double glove - the inner pair taped to the gown, the outer to remove & replace as indicated
  • surgical mask
  • eye protection
  • personal radiation dosimeters
  • NB. lead aprons do not provide sufficient shielding from gamma radiation and are unnecessary

Hospital casualty management:

  • triage casualties with life threatening conditions to treatment area & stabilise, PRIOR to decontamination
  • casualties with less serious injuries should be directed to a controlled area for radiation monitoring by the hospital RSO & decontamination

Personnel monitoring:

  • have the person stand on a clean pad
  • instruct person to stand straight, feet spread slightly, arms extended with palms up & fingers straight out
  • monitor both hands & arms, then repeat with hands & arms turned over
  • starting at top of head, cover the entire body, monitoring carefully the forehead, nose, mouth, neckline, torso, knees & ankles
  • have the subject turn around, and repeat survey on the back of the body
  • monitor soles of feet

Decontamination:

  • establish incident site decontamination facilities upwind
  • commence decontamination as soon as feasible - this may be at hospital following stabilisation of life-threatening injuries
  • preferably decontaminate walking wounded at the incident site to avoid transfer of contamination to hospitals
  • remove clothing, double bag & set aside for monitoring
  • decontamination priorities:
    • wounds
    • orifices
    • intact skin
  • local:
    • for localised contamination, may be able to wash under a tap rather than have a shower
  • whole body:
    • wash under running tepid water for at least 5 mins with soap, soft brush or cotton wool swab
    • wounds are first draped to limit spread of radioactive material, then irrigated with saline or water
  • body orifices:
    • mouth - brush teeth & rinse frequently
    • pharyngeal region - gargle with 3% hydrogen peroxide
    • swallowed radioactive material - gastric lavage
    • eyes - direct stream of water (?normal saline) from inner to outer canthus whilst avoiding contamination of the nasolacrimal duct
    • ears - external rinsing & ear syringe if tympanic membrane intact
  • decontamination end point:
    • avoid harsh scrubbing resulting in erythema or abrasion, as this will result in increased absorption of contaminant
    • repeat radiation survey at end of decontamination, paying special attention to areas of greatest contamination
    • it is unlikely all contamination will be removed
    • a satisfactory end point is a reading which is twice that of background radiation.

Decorporation

  • radioactive iodine:
    • 130mg KI tablet
    • blocks thyroid deposition
  • rare earths, plutonium, transplutonics, yttrium:
    • chelation Rx with zinc-DTPA or calcium-DTPA iv
  • uranium:
    • urinary alkalinisation, reduces chance of renal tubular necrosis
  • caesium, rubidium, thallium:
    • Prussian blue in aqueous solution blocks absorption from GIT & prevents recycling
  • tritium:
    • Rx with water which results in isotopic dilution
radiation_emergencies.txt · Last modified: 2008/09/30 23:54 (external edit)