Thyroid hormone metabolism in pediatric cardiac patients treated by continuous povidone–iodine irrigation for deep sternal wound infection

Objective: The purpose of this study was to assess the influence of povidone–iodine mediastinal irrigation used for the treatment of deep sternal wound infection (DSWI) on thyroid function. Methods: Thyroid function was studied in 18 pediatric cardiac patients treated with continuous povidone–iodine irrigation for DSWI. The median age of patients was 8 months (18 days–5.3 years). Serum concentrations of total triiodothyronine (TT3), total thyroxine (TT4), free triiodothyronine (FT3), free thyroxine (FT4), thyroid-stimulating hormone (TSH), reverse triiodothyronine (rT3) and thyroxine-binding globulin (TBG) were measured at three time points: (a) prior to mediastinal reexploration (before povidone–iodine exposure); (b) immediately after discontinuation of povidone–iodine irrigation; (c) 2 weeks after discontinuation of mediastinal irrigation. Urinary iodine excretion was examined on the last day of povidone–iodine exposure. Results: Prior to the mediastinal reexploration, the median TT3 and TT4 levels were below the normal range, then increased significantly to concentrations within the normal range. The median serum FT3 levels were within the normal range throughout the observation period, though a significant increase of FT3 levels was observed after discontinuation of irrigation. The median serum FT4 concentrations were within the normal range prior to irrigation and did not change significantly. The median rT3 levels were within the normal range, close to upper normal limit. The median TBG levels were within the normal range throughout the observation period, though a significant increase of TBG levels was observed during the period of mediastinal irrigation. The median TSH level was within the normal range prior to mediastinal irrigation and did not change significantly. Urinary iodine concentrations in infants with povidone–iodine irrigation were significantly higher 6700 μg/l (range, 1600–15 000 μg/l) than in the group of 53 healthy infants 200 μg/l (range, 20–780 μg/l, P<0,001). Conclusions: Our data showed that the use of povidone–iodine irrigation in the patients with DSWI has not lead to any significant alteration in thyroid function within the study period.