Jeffrey Nemhauser, MD
Medical Officer
Radiation Studies Branch
Division of Environmental Hazards and Health Effects (EHHE)
National Center for Environmental Health (NCEH)
Centers for Disease Control and Prevention (CDC)
In the aftermath of a radiological or nuclear incident, clinicians should expect large numbers of both physically and psychologically injured individuals to present to hospital emergency departments – this may include people not in close physical proximity to the event.
For the purposes of triage following such a disaster, individuals can be divided into 1 of 4 categories:
Since we assume that clinicians are already well-trained to handle patients that fall into the latter 2 categories – that is, those not exposed to radiation – this lecture will focus on the management of persons who have suspected or confirmed radiation exposure.
Radiation exposure – also referred to as “irradiation” – can cause serious or life-threatening illness.
At sufficiently high doses, irradiation by itself may precipitate the onset of early, life-threatening adverse health effects.
This occurs, however, only at levels of exposure likely to be seen in instances like the detonation of a nuclear bomb or an improvised nuclear device.
Individuals who have been exposed to radiation and who have sustained physical trauma are said to have combined injury.
Combined injury is defined as physical, thermal, and/or chemical trauma combined with radiation exposure at a dose sufficient to threaten overall survival or recovery.
Thus, management of any traumatic, thermal, or chemical injury can be complicated by the added presence of radiation exposure and triage and treatment decisions must include consideration of the health effects of radiation exposure.
Treatment decisions for individuals with combined injury should be based on the following four criteria:
Combined, these 4 factors can help guide the emergency clinician in the proper management and treatment of a patient in a mass casualty situation, especially when resources may be limited.
I’m now going to spend a little time discussing how the presence of characteristic adverse health effects and certain laboratory test results can assist the clinician in the mass casualty management of victims of radiation exposure.
“Adverse health effects due to radiation exposure” form one important set of clinical clues that the emergency clinician can use to assist in triage of the Radiation Mass Casualty victim.
These initial adverse health effects form one part of an illness known as Acute Radiation Syndrome or ARS.
ARS is caused by irradiation of the whole body – or significant portions of it – over a relatively short period of time.
The type and severity of ARS health effects and the timing of their onset depend on the total amount of energy deposited in – or absorbed by – the body.
This is known as the radiation dose.
All cases of ARS may be divided into 3 Stages:
The prodrome is the stage most likely to be seen by the emergency clinician and is the stage during which early triage and management decisions will be made.
Depending on the dose of exposure, clinicians in the emergency department may – or may not – witness the onset of the latent period and the manifest illness stages of ARS.
The prodrome stage of ARS is the first stage of this illness.
Onset is usually rapid – and, for most radiation exposures, lasts approximately 24–48 hours.
Adverse health effects most commonly seen during the prodromal stage include nausea and vomiting, possibly diarrhea, fatigue, headache, salivary gland inflammation, erythema or redness to the skin, and fever.
By themselves, none of these adverse health effects should be considered life-threatening although fluid and electrolyte loss due to vomiting and diarrhea may become problematic.
The prodrome of ARS is particularly helpful in the triage of patients with acute radiation exposure.
During this stage, the onset of adverse health effects occurs more rapidly with more severe forms of ARS than with the more mild forms.
Nausea and vomiting, in particular, are reliable indicators of acute radiation sickness.
The time to emesis following an exposure is roughly correlated to the absorbed dose – as we shall see on the next slide.
The rapid onset of vomiting following a radiological or nuclear incident indicates a high dose of exposure and an increasingly poor prognosis.
Conversely, vomiting occurring more than 2 hours after a possible exposure is indicative of a lower dose of exposure, a milder course of ARS, and a better overall prognosis.
Another useful clinical sign of high dose radiation exposure is a rise in core body temperature.
As seen in this table, a rise in core body temperature can be used – like nausea and vomiting – as a marker for exposure and a rough estimate of dose and outcome.
Vital signs should therefore be checked on presentation and as often as staff resources will allow.
This slide – and the one that follows – summarizes the clinical findings characteristic of the final stage of ARS – and the prognosis for recovery – based on the ARS prodrome.
Simply put, as the time to disease onset shortens and severity of prodromal health effects worsen, the worse the prognosis becomes.
I’m not going to take the time to fully discuss these slides now but I encourage you to use them as references.
In this slide, we see the worsening spectrum of disease.
In each case, vomiting occurs within the first 2 hours after exposure and possibly even sooner.
In the bottom row, for example, a severe prodrome – characterized by the onset of vomiting (within minutes) and diarrhea – combined with CNS injury, fever, and shock – is indicative of certain death, usually within days.
Using these clinical clues can help to give clinicians an estimate of radiation-induced injury and an indication of how best to allocate limited resources in the face of a mass casualty event.
Lymphocytes are among the most radiosensitive cells in the body and clinicians can use that fact to help aid their triage decisions.
A progressive decline in absolute lymphocyte counts provides an early estimate of injury caused by acute radiation exposure – if within the first two days of exposure, lymphocytes have decreased by 50% and are less than 1000 cells per μL, the patient has received at least a moderate dose of radiation.
This is seen in the graph on this slide – the Andrews nomogram.
We recommend that victims of acute radiation exposure should have – as part of their workup – a complete blood count drawn at baseline.
This should be repeated in 4–6 hours and then every 6–8 hours thereafter for 24–48 hours.
Results should be plotted and compared to the curves on this nomogram – significant, rapid declines in absolute lymphocyte count during the first 2 days indicate both a higher dose of radiation exposure and a poorer likelihood for recovery.
This slide now reintroduces the concept of Combined Injury discussed earlier.
Mass casualty patients following a radiological or nuclear incident may be triaged as either exposed or not exposed to radiation.
Radiation Mass Casualty events in which there are large numbers of patients having combined injury will test limited health care resources significantly and triage decisions will need to be made that consider long-term prognosis.
Trauma victims having radiation exposure have what is referred to as “Combined Injury” and, in general, will have a worse prognosis.
Trauma victims not having radiation exposure will be managed by emergency teams as usual.