Discussion
Betadine is a topical antimicrobial agent with a large iodine content
frequently used for wound care. Excessive iodine intake has
well-characterized toxicities within the body. Specifically, elevated
serum levels of iodine may lead to thyroid dysfunction resulting in both
psychological and metabolic effects. In this patient, iodine likely
permeated tissues during wound care therein entering the meninges.
Furthermore, iodine absorption is enhanced on denuded skin or other
tissues without a protective barrier. 5 Every
milliliter of betadine 10% contains 10 mg of iodine. Once iodine is
absorbed, it reaches equilibrium rapidly with the extracellular space
and distributes evenly except in certain areas, one of which is the
thyroid where it is used to make thyroxine (T4) and triiodothyronine
(T3). Excessive iodine may result in a transient reduction in thyroid
hormone synthesis (Wolff-Chaikoff effect) by inhibiting thyroid
peroxidase (TPO) activity.6 Iodine also prevents the
release of preformed thyroid hormones (called the Plummer effect) by
inhibiting proteolysis of thyroglobulin.6 Upon
checking her thyroid status, she was found to have a low normal TSH at
0.44 (0.3 – 4.2) and a low normal FT4 at 1.1 (0.9 – 1.7).
A reduction in thyroid hormone influences other organs, such as the
pancreas and the brain. In the pancreas, it may lead to decreased
insulin secretion, via decreased stimulatory signal on pancreatic beta
cells, thus leading to hyperglycemia and worsening of
diabetes.7 In the brain, reduced thyroid hormones may
result in pseudo-depression due to alterations in metabolic activity of
neurons. 8 Thinking back at our patient’s initial
presentation to her PCP, we suspect that the systemic absorption of
iodine from betadine was exacerbating her chronic medical conditions
leading to her worsening mood and diabetes despite taking her
medications as prescribed. Given that the half-life of iodine is about
66 days, we theorize that her actual plasma iodine level was much
higher.
Given the lack of significant differences seen on imaging as well as her
benign physical exam and lab results, we suspected that the patient had
a chronic sterile cerebritis due to the Betadine used in wound cares and
an acute soft tissue infection of the scalp. We theorized that the
irritation seen on imaging resulted from Betadine exposure via seepage
thru the cranial mesh fenestration. To confirm this theory, a serum
iodine level was obtained which returned elevated at 404 (normal: 40 –
92). Unfortunately, we were unable to obtain an iodine level from the
CSF as no such test exists.
During her hospital course, her creatinine improved with intravenous
fluids and was determined to be secondary to dehydration from poorly
controlled diabetes. She declined any additional procedures to close the
defect. Despite being on broad spectrum antibiotics, she began to
experience new episodes of confusion. Repeat imaging revealed new
enhancement of the scalp overlying the craniectomy defect as well as
extra-axial abscess formation, concerning for a worsening scalp
infection with involvement of the mesh. The patient was ultimately
discharged home on hospice with empiric oral antibiotics for the scalp
soft tissue infection and new wound care instructions (using Vashe
moistened sterile gauze rather than betadine to avoid worsening of
condition).