Time to emesis

Past studies have suggested time to emesis (TE) as one clinical parameter that can be used to indirectly determine dosage exposure. TE postradiation exposure seems to decrease as dosage increases. For TE less than 1 hour, the whole-body dose is estimated to be greater than 4 Gy. For TE between 1 and 2 hours, whole-body dose is estimated to be greater than 3 Gy, and for TE greater than 4 hours, whole-body dose is estimated to be around 1 Gy.

The most useful laboratory test in the setting of acute radiation exposure is the serial complete blood count with differential obtained every 6-12 hours. Lymphocyte count serves as an indicator for prognosis and as an estimate for the dose of radiation received. Patients with a minimal lymphocyte count (MLC) of 1000-1499/mm³ have an approximate absorbed dose of 0.5-1.9 Gy. Although these patients may have clinically significant effects, their prognosis is good because the absorbed dose is usually nonlethal.

Patients with MLC of 500-999/mm³ have an approximate absorbed dose of 2.0-3.9 Gy with severe injuries and fair prognosis. An MLC of 100-499/mm³ coincides with an approximate absorbed dose of 4.0-7.9 Gy predicting severe injury and a poor prognosis, and those with MLC less than 100/mm³ have an estimated absorbed dose of greater than 8 Gy and have a high incidence of death despite bone marrow stimulation. Survival has not been documented for those exposed to greater than 10 Gy.

Blood can also be drawn for cytogenetic evaluation. If dicentrics (chromosomes with 2 centromeres) are found, they can be used to indicate extent of radiation exposure. Cytogenetic studies are time-consuming processes that are currently not being used for mass screening strategies. Realistically, these studies may be more useful from an inpatient standpoint.

Prehospital care

In the instance of radiation accidents, prehospital personnel should wear appropriate protective gear prior to arrival at the scene and follow the guidance of the radiation safety officer or operations commander. If possible, field personnel should elicit type of radioactive material involved and extent of exposure. If a high radiation field is discovered, areas of operation should be determined. Clinical operations may be required in higher exposure areas, but exposure limits should be strictly regulated by supervisors.

Decontamination at or near the site of exposure is important, as simple clothing removal is believed to eliminate up to 90% of contamination. Unfortunately, proper decontamination is difficult to perform in the field, and personnel at receiving hospitals may find this step bypassed. If prehospital decontamination is possible, contaminated clothing and water should be collected as biohazardous material. If other injuries have occurred, BLS/ATLS protocols should be initiated and unstable patients should be rapidly transported to appropriately equipped hospitals.

Date: 2015-01-12; view: 1146