Combined injury is defined as any wound, infection or exposure to other noxious agent occurring at or around the same time as a radiation injury. Combined injuries have a much worse prognosis than single-modality injuries, and, when mass casualties have occurred, should be triaged accordingly (see Table 16.1).
Table 16.1 Triage categories without and with radiation exposure
|Triage category without radiation exposure||Triage category adjusted for radiation exposure||Triage category adjusted for radiation exposure||Triage category adjusted for radiation exposure|
|< 1.5 Gy||1.5 - 4.5 Gy||4.5 - 10 Gy|
|Minimal||Minimal||Minimal (2)||Minimal (2)|
|No injury||Ambulatory monitoring||monitor; treat as needed||monitor; treat as needed|
(2) Although the concomitant injury may require no or minimal treatment, the patient will need monitoring and eventual treatment for ARS. Colony-Stimulating Factors, if available, should be administered as soon as possible to those with significant exposures.
Adapted from: Waselenko et al. Medical Management of the Acute Radiation Syndrome: Recommendations from the Strategic National Stockpile Radiation Working Group. Ann Intern Med 2004; 140:1037-1051
Radiation and woundsRadiation injury impairs wound healing. Open wounds are prone to infection and increase the mortality rate by a considerable margin, so wound repair should be undertaken where possible. Where not possible, such as in extensive blast injuries or heavily-contaminated wounds, the survival rate will be appreciably lower.
Debridement and primary closure of wounds should occur in the first 24 - 48 hours after exposure. After 48 hours the body's capacity for repair is severely reduced, and no further surgical intervention should be carried out for approximately 8 -10 weeks.
Radiation and burnsThe combination of thermal burns and radiation exposure has a synergistic effect on mortality, and even a small dose of radiation can transform a survivable burn into a lethal burn. In mass casualty incidents, a patient with greater than 30% BSA burn and any amount of radiation exposure should be triaged to the "expectant" category.
Initial treatment should proceed as for thermal burns, but the prognosis is much worse, firstly, because the radiation-induced damage affects the basal cell layer (from which new skin growth originates) and secondly, because of systemic inhibition of wound healing. Unfortunately, the difficulty in assessing skin dose and the delay in manifestation of cutaneous radiation injury makes it difficult to formulate a definitive treatment plan in the early stages.
If a thermal burn is contaminated with radioactive material, decontamination should be attempted in a very gentle way so as not to further damage the burnt skin. Blisters should be left intact if possible, but open blisters should be trimmed and irrigated. Any residual material will be sloughed off in the normal way over the succeeding days or weeks, thus reducing the body burden.
Early administration of keratinocyte growth factor may enhance recovery in damaged and grafted skin. Radiation-damaged skin is not suitable for harvest for grafting, and if skin damage is extensive then allografts, xenografts or artificial substrates must be considered.
Radiation and chemical agentsAlthough there are very few data on the combined effects of chemical agents and radiation exposure, it is known that radiation decreases the ability of the body to respond to chemical insult. For those patients who survive the initial exposure, the mortality rate for combined chemical and radiation exposure over the next few weeks will be higher than for chemical or radiological exposure alone.
Mustard agents and T2 mycotoxins (both strong alkylating agents) have a radio-mimetic effect and can produce a syndrome that resembles ARS. A patient with combined mustard/T2 and radiation exposure will develop a more severe radiation-like syndrome than would be expected from the initial assessment.
Radiation and infectionBecause radiation has a profoundly inhibiting effect on the body's immune system, patients are exquisitely susceptible to infection. Care must be taken to disinfect the skin and gut (the two most common sources of infection in the irradiated patient), and to debride and close wounds wherever possible.
Apart from non-absorbable oral antibiotics for the gut, antibiotics should not be given prophylactically, but should be administered for specific infections, preferably after blood/swab cultures and sensitivity results are known. Anti-virals and anti-fungals may be required.