A colleague a children's hospital in the southeast USA would like to know how frequently other institutions adjust their blood irradiator time settings to assure delivery of 2500 centigray (cGy) to the center of an irradiated donor unit. She also wants to know if institutions set the irradiator to deliver exactly 2500 cGy, or if the dose is set higher to allow for the inevitable deterioration of the source. In addition, she also wants to know how center dose is determined when irradiating syringes containing blood. She reports that she has checked the AABB Technical Manual, numerous other written sources, and has discussed these questions with various peers. She reporting having found that some hospitals do not address the issue of source decay, which might allow the dose to drop below 2500 cGy, possibly putting them out of compliance. She has discovered that some facilities have a computer controlling the exposure time, but her facility is not one of them. She requests that colleagues share their experience, procedures, etc., regarding practical strategies to assure that blood is properly irradiated.

The following comments have been received.

ADDENDA Apr. 28, 2005

1. A colleague in a sunbelt state reports that the manufacturer of one of their blood irradiators calculates for them on a monthly basis the length of time that blood products need to be irradiated when using that piece of equipment. Because the amount of radiation coming from the source decreases over time, the time it takes to administer an irradiation dose needs to be adjusted upwards on a periodic basis, based on a dosimetry reading/mapping submitted to the manufacturer every 5 years. The irradiator manufacturer sends them a chart showing what the irradiation timer should be set for each month (for 5 years). The increase is then essentially validated every 6 months by a dosimetry reading/mapping to ensure that a minimum of 2500 cGy is being consistently delivered to the central part of the cannister/product.
She has a question for colleagues regarding the irradiation of blood in syringes: She is interested to learn if colleagues who irradiate syringes have validated the quality of the blood after the syringe has been irradiated. In other words, she would like to know if there are data that show what happens to blood that has been irradiated while in a plastic syringe. Does the irradiation cause changes in the plastic that might be harmful for the RBCs or platelets (and the patient)? The syringe manufacturers with whom she has spoken have not provided her with such data. Rather, they suggest that her hospitals irradiate blood in aliquot bag and then transfer the irradiated blood to a syringe. Such a protocol means double labeling (bag and syringe) and multiple opportunities for error.

ADDENDA Apr. 29, 2005

2. A transfusion medicine physician in California reports that in his past experience at a regional blood provider the policy was to perform calibration every 6 months to increase the time of irradiation to allow for decay of the cesium source. In addition, the policy was also to use 3000 cGy (based on looking at dose maps) to be certain that all parts of any bag (or bags) placed in an irradiator received an adequate dose. He adds that in the UK Redbook and in Germany, per their regulations, the recommended dose is 3000 cGy. Finally, he does not think that irradiating a syringe of blood makes a difference in terms of its safety and efficacy, but looking at a dose map might help assure an appropriate dose is delivered. In any case, he has used 3000 cGy to make sure that the whole area gets sufficient irradiation.

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Ira A. Shulman, MD
CBBS e-Network Forum Editor & Moderator