Radiation poisoning can come from numerous sources--many of which are linked to terrorism, which is a growing concern in almost every part of the world today. From accidents like Chernobyl to potential "dirty bomb" scenarios, physicians have to be at the ready in case of an event requiring massive mortality and morbidity. A good way to judge the amount of poisoning is to judge how long it takes after exposure for vomiting to occur. If it occurs under four hours, roughly 3.5 Gy (Grays) have been delivered and the mortality after 30 days is roughly 50%. If it occurs in under one hour, the estimated dose is as high as 65 Gy. Poisoning can affect many systems in the short and long term.
Hematopoietic
Symptoms that begin to occur after a dosage of 1.5 to 2 Gy has been delivered include lymphopenia (drop in lymphocyte count), neutropenia (loss of white blood cells and their parent progenitor cells), thrombocytopenia (loss of platelet progenitors, which causes greatly reduced platelet counts) and anemia. The greater half life of red blood cells makes anemia less of a problem in the acute setting and stem cell transplantation is a possibility with severe exposures.
Gastrointestinal (GI)
Radiation doses in the 6 to 20 Gy range will start to affect the GI system and signal a poor prognosis. There will be diarrhea where fluid losses can trigger shock, infection caused by opportunistic organisms invading when membrane integrity is compromised and bleeding when the vasculature present in the submucosa is damaged as well. Mainstays of treatment include fluid resuscitation and empiric therapy to treat infections, especially in a host with decreased lymphocytes/neutrophils from the hematopoietic syndrome.
Neurovascular Syndrome
This is poorly defined and usually occurs with doses in the 20 to 30 Gy range. Mental status changes accompanied by seizures along with depressed reflexes and ataxia are the early changes, and often appear to improve. Usually the improvement is followed by a precipitous decline and symptoms of shock. Within 48 hours, the combination of hypotension, increased cerebral pressure and brain anoxia will usually cause death.
Cutaneous Symptoms
Damage to the skin usually includes the epidermis and in some cases, the dermis as well; severe exposures can reach as deep as the muscle and bone. The patient is at increased risk for fluid loss and edema, which can subsequently put the patient at risk for compartment syndrome. Radiation burns present later than thermal burns, and if the burns present themselves almost immediately, they are likely thermal in nature.
Pulmonary Injury
The effects on the pulmonary system are not acute and usually appear one to six months after exposure, especially after therapeutic exposures. Pneumonitis with resultant alveolar hemorrhage and pulmonary edema occurs earlier than the dreaded post-radiation pneumonia, which is often fatal. Patients that recover from the pneumonia almost invariably have pulmonary fibrosis (scar tissue replacing normal pulmonary parenchyma), which can cause serious disability.
Renal Injury
Renal toxicity occurs comparably late, usually months to years after initial exposure to doses in the 10 to 20 Gy range. Structural damage and scarring occur within the glomerulus and tubular epithelial cells, with resultant increases in levels of protein and nitrogen in the urine. Hypertension soon follows and most medical treatment is based around suppression of the renin-angiotensin system via ACE Inhibitors and angiotensin receptor blockers.
References
- Clinical Pediatric Emergency Medicine. "Preparation for Terrorist Threats: Radiation Injury." Siegel D. Volume 10, Issue 3 (September 2009)
- Health Physics. "Health effects in those with acute radiation sickness from the Chernobyl accident." Mettler F. 01-NOV-2007; 93(5): 462-9
- Cecil Medicine, 23rd ed. Goldman 2007
