Radiation Exposure

Radiation can be subdivided into two categories ionizing and non-ionizing, both of which have an effect on human tissue. Knowledge of the effects of ionizing radiation exposure and how medical personnel should respond is useful and has also become more topical given the raised awareness of potential terrorist attacks.

Despite heightened media interest, radiation exposure accidents on a large scale are extremely rare. The number of recorded deaths from unintentional radiation incidents, such as the Chernobyl disaster, is 134 deaths in 420 incidents from 1944-2002. Small-scale accidents also occur with industrial, diagnostic and therapeutic application of radiation and in the storage of spent devices. Deaths from intentional radiation exposure incidents such as the bombing of Hiroshima are obviously much higher. The most likely form of radiation incident that we are likely to encounter will be from a terrorist dirty bomb or an industrial accident.

Environmental exposure to radiation occurs from natural sources such granite, cosmic rays and man-made sources. The effects of ionizing radiation can be immediate (burns, radiation sickness) or long term (haematopoetic cancers, solid tumours.) This module will cover the immediate and short term effects only.

Environmental exposure to ionising radiation occurs from natural sources (e.g. granite, cosmic rays) and man-made sources.

This session will cover the presentation and management of immediate and long-term effects only.

Immediate effects of ionising radiation	Long-term effects of ionising radiation
Burns	Haematopoetic cancers
Radiation sickness	Solid tumours

Radiation kills cells by disrupting neutral atoms. It dislodges orbital electrons to form an ion pair consisting of a dislodged electron and the residual atom. Ion pairs are highly chemically reactive.

Rapidly dividing cells are more vulnerable. The clinical outcome depends on how many and which cells die. At lower doses, cells do not die but are at risk of DNA damage and subsequent malignant change. Potential carcinogenesis can occur at lower exposures.

The effects of radiation depend not only on the type of radiation but also on time, distance and shielding all of which must be considered when planning decontamination of the exposure areas. The absorbed dose is directly proportional to time. Only the minimal amount of time should be spent in the vicinity of a radioactive source.

Without medical management, the lethal dose to kill 50% of the population at 60 days is 4.5 sieverts (Sv). With medical management, 50% of the population would survive exposure to 5-6 Sv.

Cumulative Dose

The half-life of radionucleotides varies from days (iodine) to years (strontium, cobalt).

What might the cumulative dose depend on?

The cumulative dose will depend on:

• The measured dose at exposure
• The duration of exposure
• The date of decay
• The distance from the radioactive source (also affects radiation dose as absorbed radiation decreases proportionally to the square of the distance)
• Shielding (lead in some cases can reduce the effective absorbed dose)

History

Introduction

Exposure to radiation can result in localised or whole-body exposure and internal or external radioactive contamination. Recognition of radiation exposure is based on history and examination.

History

The priority is to assess the dose of radiation received, obtaining and recording as much information as possible about:

• The type and extent of exposure (what, where, when, and for how long?)
• The date and time of onset
• The severity of all symptoms and signs
• Sites of any erythema or local injury (see Lund and Browder charts)

Examination (Local)

Short-term sequelae

In the acute setting, a radiation burn appears similar to a thermal burn with signs of:

• Erythema desquamation (dry or wet)
• Blistering
• Oedema
• Pain

Long-term sequelae

The long-term sequelae are:

• Vascular insufficiency
• Ulceration
• Necrosis
• Acting as an entry point for infection in a potentially immunocompromised patient

Short- and Long-term Effects of Radiation Exposure

There are a number of short- and long-term effects of radiation exposure. These effects can be used as indicators to assess factors such as the dose and duration of exposure.

Examination (Systemic)

Radiation syndrome manifests as an acute or delayed result of exposure of the whole body to high doses of ionising radiation.

It causes a non-specific clinical picture, including:

• Gastrointestinal effects
• Cardiovascular effects
• Neurological effects
• Haematological changes

The most vulnerable tissues are affected first, and the severity, speed of onset and duration of effects depend on dose. This can be broken down into four phases:

Prodromal phase

The typical picture starts with a prodromal phase lasting about 12 hours:

• Nausea
• Vomiting
• Weakness
• Fatigue
• Neurological signs

Latent phase

In the latent phase, which lasts 5-7 days, the patient seems to recover.

Period of obvious illness

The latent phase is followed by a period of obvious illness:

• Gingival bleeding
• Epistaxis
• Petechiae
• Systemic infections and gastrointestinal symptoms lasting up to 4 weeks

The risk of infection is highest at 25-35 days due to marrow suppression.

Recovery or death

The final stage is recovery or death.

Radiation Effects

The table below shows the effects of radiation exposure on the human body at varying doses

The table below shows the effects of radiation exposure on the human body at varying doses

Dose (Sv)	Clinical picture	White blood cell	Other
1	Mild or absent symptomsEpisodic vomiting and nausea for 48 hours	Mildly depressed white blood count at 2-4 weeks	No fetal effectsCounselling needed if pregnant and >100 mSv
1-8	Haematopoetic syndrome, anorexia nausea and vomiting, fatigue 1-4 hours after exposureLatent 2-28 days, bone marrow suppression, leukopenia, infection, thrombocytopenia, bleeding, bruisingHair loss at 2-4 weeks	Serial lymphocyte counts predict severity	Survival about 50% without treatment, 60% with medical treatment
6-20	Gastrointestinal syndrome, early nausea and vomiting. Fatigue and anorexia, latent hours – 1 week, severe gastrointestinal symptoms: fever, abdominal pain, cramps, watery diarrhoea, haemorrhage, electrolyte imbalance, dehydration	Also associated with bone marrow suppression	>10 Sv usually results in death within 2 weeks
>20	Almost instant vomiting, explosive bloody diarrhoea, headache, collapse, level of consciousness, agitation, burning sensation of skin, may have lucid interval in hours, death from coma, convulsions, hypotension, shock		Death in a few days

Risk Stratification

Acute radiation syndrome system

The acute radiation syndrome (ARS) system is used by the British Institute of Radiology. It grades involvement of four specific systems with scores from 1-4:

• Neurovascular (N)
• Haematological (H)
• Cutaneous (C)
• Gastrointestinal (G)

A grading code is then generated with a severity index ‘i’. This grading code can be used to generate a response category (RC) and is specific to a time point. For example: ‘3d’ is day 3. The RC is used to guide further examinations and investigation and the likelihood of recovery.

There are also computer-assisted models that can predict exposure risk. Another early indictor of the severity of exposure is the lymphocyte count after 12 hours.

External indicators

Radioactivity can easily be detected with:

• Geiger counters (see image)
• Area survey meters
• Personal dose-rate meters

These are usually available in radiology and radiotherapy departments.

Blood tests

Full blood counts should be done at 12 hours and then every 4 hours. Lymphocyte counts decrease depending on the dose absorbed by the body and consequent severity of radiation sickness. Urea and electrolytes should be measured to assess the level of dehydration from vomiting and diarrhoea and to guide on-going fluid therapy.

Introduction

The management of radiation incidents can be divided into:

• General measures dealing with managing the incident
• Specific measures for the exposed patients

General measures can be subdivided into:

• Preparation
• Acute crisis management
• Management of the long-term consequences

General Measures: Preparation

At the planning stage, consideration must be made for command/control issues, nominating organisation responsibility, personnel training, notification criteria and obtaining appropriate equipment such as protective clothing.

In most emergency departments (EDs), senior medical and nursing staff will have chemical, biological, radiological and nuclear (CBRN) training and will be familiar with the response plan and equipment for that hospital. Information can accessed on the Health Protection Agency (HPA) website (see Further Reading and Activites in Resources).

The safety officer or a deputy for the radiotherapy department should be involved in a significant radiation incident.

Learning Bite

The safety officer for the radiotherapy department should be involved.

General Measures: Acute Crisis Management

In the acute crisis management stage, one must consider how to:

• Triage and deal with injured patients
• Limit further exposure to population and personnel
• Organise decontamination and evacuation

Long-term Consequences: Personal Safety

Recommendations about exposure are:

• At 0.1 mGy/h, personnel can enter and give life-saving or time-critical treatment
• At >0.1 mGy/h, exposure is life-threatening so personnel should not proceed
• All staff dealing with contaminated patients should wear protective clothing and carry a personal radiation meter

All staff dealing with contaminated patients should wear protective clothing and carry a personal radiation meter.

Long-term Consequences: Initial Assessment and Triage

Initial assessment should be based on the airway, breathing, circulation (ABC) system, allowing categorisation of patients into two groups:

• Those with life-threatening injuries
• Those with non-life-threatening injuries

All patients with life-threatening injuries should be treated as contaminated and evacuated to a medical facility that has been pre-alerted to their arrival.

Patients with non-life-threatening injuries and the non-injured population should be evacuated upwind and then formally assessed for contamination.

Long-term Consequences: Decontamination

 

On-scene decontamination is usually not possible if large numbers of people have been affected.
By removing clothes, up to 90% of contamination is removed. Exposed individuals are then hosed down with warm water (to prevent hypothermia) and detergent. Decontamination should use the rinse-wipe-rinse; system. It is important not to abrade the skin barrier during decontamination. All contaminated materials and water must be disposed of appropriately.

Learning Bite

Removing clothes removes up to 90% of decontamination. Avoid abrading skin during contamination as this allows infections in potentially immunocompromised people.

Specific Measures

The ED receiving patients from the exposure zone should be divided into areas to deal with those who are radiation-contaminated and those who are not.

Safe transfer of patients between areas can be achieved by wrapping each patient in a sheet, which limits cross-contamination. When patients arrive, they can be further segregated into those who are externally contaminated only, internally contaminated only, and those with combination injuries and trauma associated with detonation devices such as blast, flash and thermal injuries.

Learning Bite

The department should be separated into ‘dirty’ and ‘clean’ areas.

External radiation injuries

Wounds should be rinsed with saline and left open until debrided and decontaminated. Surgical excision of some long half-life materials may be required. After this, wounds should be closed or covered to prevent entry of infection. In addition, the clinical approach is to provide adequate analgesia and antibiotic prophylaxis as well as considering vasodilator therapy and referring the patient for plastic surgery for definitive grafting/amputation as appropriate.

Internal contamination

The aim of internal contamination is to reduce the overall radiation dose by strategies for reduction of absorption, dilution, blocking, displacement by non-radioactive nucleotides, increased elimination from tissues, chelation and decorporation. The particular strategy will depend on the radioactive substance to which the patient has been exposed. For example: decorporation, which is the removal of internal contamination by exploiting the chemical and biological properties of the radioisotope; Prussian blue is used for caesium exposure or bicarbonate for uranium exposure.

Acute radiation sickness

Management of acute radiation sickness is mainly supportive and includes:

• IV fluids
• Antiemetics
• Analgesia
• Nutritional support
• Antibiotics
• Antifungals
• Antivirals
• Blood component substitution
• Reduction of brain oedema (mannitol and ventilation strategies)

The doctors best qualified to look after these patients are usually haematologists as the condition is very similar to aplastic anaemia and haematologists are familiar with the preparation processes for bone marrow transplants.

Long-term management

Potassium iodide or iodate is given to prevent radioiodine in thyroid accumulation.

Adults	Children	1m 3y	Neonates
130 mg	65 mg	32 mg	16 mg

Options for definitive therapies include stimulation therapies such as:

• Granulocyte-stimulating factor (GSF)
• Granulocyte-macrophage colony-stimulating factor (GM-CSF)
• Bone marrow transplant
• Stem cell therapy
• Definitive surgery
• Cancer surveillance
• Infertility and potential teratogenesis management
• Addressing the psychosocial impact of exposure

1. Health Protection Agency. CBRN incidents: A Guide to Clinical Management and Health Protection. 2008; London: HPA.
2. Health Protection Agency. Radiation.
3. British Institute of Radiology.
4. British Institute of Radiology. Medical Management of Radiation Accidents: Management of the Acute Radiation Syndrome. 2001; London: BIR.
5. National Poisons Information Service.
6. Bland SA. Management of the irradiated casualty. J R Army Med Corps 2004;150:5-9.