TABLE 90.13 DOSE–EFFECT RELATIONSHIP AFTER ACUTE WHOLE-BODY RADIATION EXPOSURE Whole-body absorbed dose (Gy) Comments 0.1 Asymptomatic (minimal detectable dose using cytogenetics) Asymptomatic (minor depression of white blood cell and platelets) Nausea and vomiting in approximately 15% of patients within days of exposure 0.5 Nausea and vomiting in most patients Nausea, vomiting, and diarrhea within 48 hrs; severe hematologic depression; 50% mortality without medical treatment 100% mortality within 30 days without medical treatment; 50% mortality with medical treatment Gastrointestinal syndrome; survival unlikely; death in 2–3 wks 50 Cardiovascular/Neurovascular syndrome; death in 24–72 hrs With doses of to Gy, the primary effect of whole-body radiation is to depress the bone marrow Although the absolute lymphocyte count ( Fig 90.12 ) decreases rapidly within the first 24 hours, there is no need for specific medical treatment The patient will be at greatest risk to weeks after the radiation exposure when the total white blood cell, neutrophil, and platelet counts reach a nadir ( Fig 90.13 ) At this time, the patient is vulnerable to death from infection and bleeding If the patient can be supported during this period of vulnerability and if the bone marrow is not irreversibly damaged, a recovery phase ensues The gastrointestinal syndrome occurs from absorbed doses of more than approximately Gy During the prodromal phase there is prompt onset of severe nausea, vomiting, and diarrhea There is a latent period of approximately week and then recurrence of GI symptoms, sepsis, electrolyte imbalance, and likely