# Situation: A 34-year-old woman with Graves disease is admitted for total thyroidectomy because a large goiter makes swallowing difficult. She has taken methimazole for 3 months, and potassium iodide solution was added 9 days ago. She has no known drug allergies. She asks why the iodine solution was added before the operation. The nurse's answer is based on which effect of the solution?

> source: MyMerci (mymerci.kr)  
> url: https://mymerci.kr/pages/nclex_q.php?qn_id=630304  
> language: ko  
> subject: Nursing Practice IV — Care of Clients with Problems in Nutrition and Gastrointestinal, Metabolism and Endocrine, Perception and Coordination

## 문제

Situation: A 34-year-old woman with Graves disease is admitted for total thyroidectomy because a large goiter makes swallowing difficult. She has taken methimazole for 3 months, and potassium iodide solution was added 9 days ago. She has no known drug allergies.

She asks why the iodine solution was added before the operation. The nurse's answer is based on which effect of the solution?

## 보기

1. It replaces the iodine lost during surgery
2. It reduces blood flow to the thyroid gland **✔ 정답**
3. It relieves the swelling behind her eyes
4. It prevents low calcium after the operation

**정답: 2**

## 해설

Iodine solutions such as potassium iodide are given for about 10 days before thyroidectomy to reduce the vascularity of the gland, which lowers blood loss during surgery. They have no role in calcium balance or in Graves eye disease.

## 심화 해설

Why iodine is given before thyroidectomy

The rationale for adding potassium iodide solution about 10 days before surgery is to make the operation safer by reducing bleeding. In Graves disease the thyroid gland is not only overactive but also markedly hypervascular. Iodine acutely suppresses thyroid hormone synthesis and release, but for the surgical team the most important effect is a reduction in gland blood flow and vascularity. A less engorged, firmer gland is easier to dissect, and intraoperative blood loss is lower. [1][3]

The preoperative iodine solution works primarily by decreasing thyroid vascularity, which reduces intraoperative bleeding and improves visualization of the surgical field. [1][3] This is why the correct answer is “It reduces blood flow to the thyroid gland.”

The other options do not reflect the mechanism of iodine in this setting. Iodine is not given to replace iodine lost during surgery, and it has no direct role in maintaining postoperative calcium balance. Calcium disturbances after total thyroidectomy are caused by injury, devascularization, or inadvertent removal of the parathyroid glands, not by iodine deficiency. [1] Graves eye disease, or thyroid-associated ophthalmopathy, is driven by autoimmune orbital inflammation and is not treated with preoperative potassium iodide.

Watch out! Do not confuse the antithyroid effect of iodine with a calcium-protective effect. Hypocalcemia after thyroidectomy is a parathyroid-related complication, and iodine does not prevent it. [1]

Key point! The preoperative iodine course is short, usually about 7–10 days. Prolonged use can cause the thyroid to escape from the inhibitory effect, a phenomenon called iodine escape, so the timing is intentional. [3]

| Option | Mechanism | Supported by iodine? |
| --- | --- | --- |
| Replaces iodine lost during surgery | Iodine is not consumed or depleted by thyroidectomy in a way that requires replacement | No |
| Reduces blood flow to the thyroid gland | Decreases gland vascularity and intraoperative bleeding | Yes [1][3] |
| Relieves swelling behind the eyes | Graves ophthalmopathy is autoimmune and not responsive to short-term iodine | No |
| Prevents low calcium after the operation | Postoperative hypocalcemia is related to parathyroid function, not iodine | No [1] |

The evidence base for this practice is still debated. A systematic review and meta-analysis found that preoperative iodine administration was associated with reduced intraoperative blood loss, but the overall quality of evidence was limited, and the effect on other complications such as recurrent laryngeal nerve injury or hypocalcemia was not clearly established.  A propensity score analysis similarly reported that potassium iodide did not significantly reduce postoperative complications, although it may improve the operative field through reduced vascularity.  A European high-volume center study also noted that potassium iodide affects thyroid vascularity and may improve intraoperative visualization, even though clear evidence for routine use remains lacking. [3]

From a nursing perspective, the key teaching point is that the patient is receiving iodine for a short, focused purpose: to make the gland less vascular and the surgery safer. The nurse should also recognize that this medication is not a treatment for the eye changes of Graves disease and does not substitute for postoperative calcium monitoring. [1]References (research sources)

- [1]Preoperative Lugol's solution and surgical outcomes in Graves' disease: a single-center retrospective study.Research articleÜnlü MT, Caliskan O, Çetinoğlu I, Şengül Z, Arikan H, Gerçelman D, Aygun N, Uludag M. (2026) · DOI: 10.3389/fsurg.2026.1755477

- [3]Preoperative Potassium Iodide Treatment in Patients Undergoing Thyroidectomy for Graves' Disease-Perspective of a European High-Volume Center.Research articleLindner K, Kußmann J, Fendrich V (2020) · DOI: 10.1007/s00268-020-05593-0

## 임상 시나리오

Preoperative Iodine in Graves DiseaseReducing Surgical Bleeding Risk
Potassium iodide is given for about 10 days before thyroidectomy to reduce thyroid vascularity. This decreases intraoperative blood loss and improves surgical field visualization.

A less engorged, firmer gland is easier to dissect. The effect is on blood flow, not on calcium balance or Graves eye disease.

CautionDo not confuse the antithyroid effect of iodine with a calcium-protective effect. Postoperative hypocalcemia is caused by parathyroid injury, not by iodine deficiency.

## 핵심 개념

- **Potassium iodide** — Iodine solution given preoperatively to reduce thyroid gland vascularity and intraoperative bleeding.
- **Thyroidectomy** — Surgical removal of the thyroid gland, indicated for large goiters causing compressive symptoms.
- **Graves disease** — Autoimmune hyperthyroidism characterized by a hypervascular, overactive thyroid gland.
- **Vascularity** — Degree of blood vessel density and blood flow within a tissue; high in Graves disease.
- **Hypocalcemia** — Low serum calcium after thyroidectomy, caused by parathyroid gland injury or devascularization.

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