Answer to Question #10877 Submitted to "Ask the Experts"

What are the added issues when dealing with a dialysis patient who is given either a hyperthyroid dose or an oblation dose of iodine-131 (¹³¹I): retention of the ¹³¹I in the blood stream, dose to the poorly functioning kidneys, dependence on physical half-life rather than biological half-life, issues at the dialysis center, etc.? I haven't run across this issue in the past.

I think a key to success is in preplanning and the sharing of information. Treating a patient on dialysis is a team effort. When staff members are informed in advance through training or meetings, and have the opportunity to ask questions, they feel more comfortable in handling the case.

At my institution, we admit thyroid cancer patients, treat them with ¹³¹I in the afternoon, and then dialyze daily starting the next morning for two to three days. Because our objective is to remove as much of the circulating ¹³¹I as possible the day after treatment, with our last patient the dialysis unit dialyzed for four hours rather than the typical three hours. Not all patients can medically handle that length of dialysis, but in this case it was very successful. In all cases, we have found that we have removed about 95% of the circulating ¹³¹I at the time of discharge based on serial blood draws. The patient then returns to his or her normal dialysis schedule as an outpatient.

We have had no significant contamination issues and the hospital dialysis equipment (less the tubing that is removed as standard practice as well as the blood pressure cuff, which we routinely replace) was returned to the renal service on the day of discharge. We have measured the doses received by the dialysis team as well as the other nurses involved with the patients' care and have yet to see anyone receive a dose in excess of 0.50 mSv.

From the medical perspective, your nuclear medicine physician should consider the prescribed dose so that they take into account the increased exposure to the red marrow. I think most facilities lower the prescribed dose by 25–50% from what they would normally use to assure that the marrow is not adversely impacted. Kidney dose is difficult to assess, as the range of function of these patients varies. Removing as much of the ¹³¹I from the circulation within 18–48 hours after therapy will help to keep the dose to other organs as low as possible. Another thing to consider is the fact that many dialysis providers use an iodine-based cleaning product on the patients' skin (such as Povidone). This should be stopped in advance of treatment as the iodine can cross the skin and block the thyroid.

Though I have no personal experience with patients receiving low doses of ¹³¹I for benign thyroid conditions, I would think that treatment could be successfully carried out on an outpatient basis. Again, planning and communication among the members of the team that are managing the case is the key to success.

Linda Kroger, MS
Radiation Safety Officer