Medical response to a major radiologic emergency - handout

Adapted from Wolbarst et al, Medical Response to a Major Radiologic Emergency: A Primer for Medical and Public Health Practitioners. Radiology: Volume 254: Number 3—March 2010

Medical Response to a Major Radiologic Emergency

Planning in radio-nuclear (R/N) events revolves around 4 basic scenarios

Detonation of a nuclear weapon

Meltdown of a nuclear reactor,

Explosion of a large radiologic dispersal device (“dirty bomb”)

Surreptitious placement of a radiation exposure device in a public area of high population density

Basic concepts in Radiological exposures

Units (traditional vs SI) are in almost all emergency situations numerically equivalent

Absorbed dose is a measure of the actual energy deposited in an irradiated mass

Equivalent dose adds a measure of biological impact of the radiation type

Effective dose is an aggregation of per tissue/organ estimates of the Equivalent dose weighted for the sensitivity

of the organs involved, giving an estimate of the impact of absorbed dose on an organism

Health effects of radiation Depend on:

Dose absorbed

Part of the body exposed

Rate

Route

Type (ɑ, β, γ, x rays or neutrons)

Stochastic effects

o Random effects of transformation of genetic material within 1 or more cells, with increasing probability of

occurrence with dose, but may occur even at low dose. E.g. carcinogenesis

Farooq Khan MDCM PGY3 FRCP-EM

McGill University November 14

th 2011


Deterministic effects

o Predictable dose-dependent effect of radiation-induced acceleration of cellular processes, damage or apoptosis

leading to organ dysfunction. Can be acute or late in onset.

General Principles of Radiation Safety

Direct exposure to ionizing radiation o Patients nearby during or after a R/N event, irradiated but not rendered radioactive or contaminated

themselves.

Contamination with radioactive materials o Patients around contaminated objects, environments or people having now contaminated themselves through

various routes. HCPs should wear PPE and keep exposure as low as reasonable achieved (ALARA).

ALARA principles

Minimize time

Maximize distance

Use shielding when appropriate,

Ensure prompt removal or containment of contamination

Type of radiological contamination

ɑ-particles: large, slow moving, deposit energy locally, cannot traverse epidermis. Internal hazards

β- particles: can penetrate several cm into skin. Internal and external hazard

γ and x-rays: non-particulate, high energy radiation capable of penetrating the whole body and require

lead or concrete shielding. Internal and external hazards

External contamination

Clothing should be removed and placed in identified radio-hazard bags

Surveys with sealed radiation detection equipment should start with open wounds, then facial orifices followed

by skin

Nasal and buccal swabs should be taken for analysis

Gentle irrigation of wounds followed by usual scrubbing of skin is appropriate, use waterproof paper for run-off

into plastic garbage containers or bags that can be disposed of separately. Dab away excess fluid 1 gauze at a

time. Perform another detection survey after irrigation before proceeding with surgical closure; small amounts

of contamination is acceptable before closure.

Repeat survey-wash-rinse sequence until readings drop to 2-3× background levels.

Whole body shower is rarely needed.

Internal contamination

Via inhalation, ingestion, percutaneous transdermal, or open wounds/abrasions.

Little can or needs to be done acutely

Specialized equipment and expertise is required to assess for and prevent organ uptake (e.g. iodine in the

thyroid, or radium, americium or plutonium in the bone)


Protection of personnel

o Personnel in the proximity of or in contact with a few individuals who are lightly contaminated externally will be

exposed to ionizing radiation, although this generally (depending on the isotopes) involves very little risk.

o Personnel dealing with a multitude of more heavily contaminated patients, on the other hand, may accumulate

a substantial dose over time, unless they are careful and follow standard precautions against any hazardous

materials. Moreover, they can inadvertently transfer contamination to themselves and from there to others.

Planning and training Protocol should be scalable, user-friendly, and directly outline each participant’s role.

Planning should be community-wide including:

Medical personnel, local public safety, public health, psychologic services, and emergency management officials,

together with first responders from fire departments, EMS, law enforcement, and other agencies.

At the ED level involve:

Radiation safety staff, the radiology and radiation oncology departments, security and communications, hospital

administration, clinical affairs, and public relations.

Components of plan include:

Personnel and resource management

Worker health and safety

o Establish common transport pathways, safe areas for family etc. In addition to PPE

Communication

o Establish and routinely test redundant systems, have back-ups for systems that could be incapacitated

by a nuclear blast.


ARS See separate ARS handout for further details.


General Management Principles: Dose estimated by

time to onset vomiting,

lymphocyte depletion rates,

distance from radioactive source

o Confirmed by dicentric chromosome analysis of swabs/tissues etc

Triage patients to

o Mild exposure

Many individuals who arrive at the ED will be physically intact but emotionally traumatized

o Severe potentially life threatening exposure

With excellent supportive care, victims may recover following acute whole-body exposures of 5–6 Sv

o Highly likely to be fatal exposure

Patients rarely survive >10 Sv

Combined injury leads to more effects at low doses

in chaotic situation track the contamination status, diagnosis, and treatment of patients by attach a hard copy of the

medical record package, or at least a brief note, either to clothing or to a cord hung around the neck

heavy internal contamination is suspected, significant intervention may be required early on to prevent

incorporation of radionuclides into critical organs


Use diagnostic risk assessment and management algorithm below as a guide, tailored to specific situation


Immediate General Medical Care and Monitoring of the Heavily Exposed but

Potentially Salvageable Patient

First priority:

Acutely life- and limb-threatening medical and surgical conditions

Concurrent collection of medical history and the history of the event

Once the patient is stabilized:

Management of direct exposure and of external and internal contamination,

Signs and symptoms of radiation injury and/or illness might not appear for hours to days and sometimes weeks.

Loss of fluids and electrolytes:

particularly problematic in infants, children, and the elderly

Medication

Antiemetics

o Phenothiazines, like prochlorperazine or chlorpromazine not very effective

o 5-HT 3 receptor inhibitors like ondansetron (Zofran) may be required for radiation-induced vomiting

Pain control

Antimicrobials

o not needed immediately (infections do not appear for days)

o prophylaxis if doses high enough to cause ARS

o infection-directed antibiotics, antivirals, antifungals and antihelminthic agents

G-CSF and GM-CSF

Surgical Intervention

Try to do surgeries within 24-36h of exposure while patients are:

o not immunocompromised,

o have better wound healing

o no bleeding diathesis

Bone marrow stem cell transplant

For exposures of 6-10 Sv without comorbid conditions

Internal contamination

GM counters screen for γ and β (which is also detected by scintillators) ɑ and neutron difficult to detect

Once in the body, nearly all radioisotopes behave chemically exactly like stable isotopes of the same element

Thus management similar to treatment of poisoning, best carried out by EM physicians and medical toxicologists

Reduce uptake and/or enhance clearance with standard decon and detox techniques i.e. antacids or a cathartic

e.g. castor oil or Mg sulphate

Specific countermeasures for significant contamination by identified radionuclides, e.g. KI for radioiodines,

Zn/CA-DTPA for plutonium/americium, Prussian Blue for Cesium and Thallium, HCO3- for uranium renal toxicity

Children

Higher risk of pulmonary contamination (hyperventilate)

Tissues more sensitive to carcinogens

Psychologically less resilient

Health & Medicine

Medical response to a major radiologic emergency - handout