Why can't we operate on a patient with uncontrolled thyroid disease, i.e. not in a euthyroid state?

Why Surgery is Avoided in Non-Euthyroid Patients

The traditional teaching that patients must be euthyroid before surgery is increasingly being challenged by recent evidence, though cardiovascular stabilization remains essential—particularly for hyperthyroid patients, where beta-blockade to control heart rate and prevent thyroid storm is more critical than achieving biochemical euthyroidism. 1, 2, 3

The Traditional Rationale (Historical Perspective)

The longstanding recommendation to achieve euthyroidism before surgery was based on several theoretical concerns:

• Thyroid storm risk: The feared complication of intraoperative or postoperative thyroid storm, characterized by hyperthermia, tachycardia, and hemodynamic instability 1, 4
• Cardiovascular complications: Hyperthyroidism causes increased cardiac output (up to 300% above normal), decreased systemic vascular resistance, and increased blood volume (up to 25%), creating significant perioperative cardiovascular stress 1
• Atrial fibrillation: Occurs in 5-15% of hyperthyroid patients, particularly those over 60 years, increasing thromboembolic and hemodynamic risks 5, 1
• Surgical field optimization: Achieving euthyroidism was thought to decrease thyroid vascularity and improve surgical planes 4

Current Evidence: The Paradigm is Shifting

For Hyperthyroidism

Recent high-quality studies demonstrate that thyroidectomy can be performed safely in actively thyrotoxic patients without precipitating thyroid storm, provided cardiovascular stability is achieved. 2, 3

• A 2023 retrospective cohort of 275 hyperthyroid patients found that 51.3% underwent surgery while uncontrolled (elevated T3/T4), with zero cases of thyroid storm in either the controlled or uncontrolled groups 3
• The uncontrolled group had only minor differences: slightly longer operative times and increased estimated blood loss (20 mL vs 15 mL median), with similar low complication rates except for temporary hypocalcemia (13.4% vs 4.7%) 3
• A 2020 study of 248 patients found no thyroid storm events or mortality in patients who could not tolerate antithyroid drugs and underwent surgery while hyperthyroid 6
• A 2013 series of 165 total thyroidectomies for Graves' disease showed that 42% remained hyperthyroid at surgery with no cases of thyroid storm, challenging the American Thyroid Association guidelines requiring euthyroidism 7

Critical Distinction: Biochemical vs Clinical Control

The key is cardiovascular stabilization with beta-blockers, not necessarily achieving normal thyroid hormone levels. 1, 2

• Beta-blockers should be initiated before surgery to control heart rate and improve cardiovascular symptoms, even if biochemical euthyroidism cannot be achieved 1
• The goal is to lower heart rate to nearly normal, which improves tachycardia-mediated ventricular dysfunction 1
• Preoperative treatment does not prevent thyroid storm whether the patient is euthyroid or hyperthyroid during surgery—the supporting evidence for mandatory euthyroidism is limited 2

For Hypothyroidism

Elective surgery should be delayed until euthyroidism is achieved in hypothyroid patients, as untreated hypothyroidism increases risk of heart failure, gastrointestinal complications, and prolonged ventilation requirements. 8, 9

• However, levothyroxine should be continued through the surgical period without interruption, including the morning of surgery 8
• Hypothyroid patients undergoing CABG have higher incidence of postoperative heart failure and gastrointestinal complications 9
• Even subclinical hypothyroidism (TSH ≥10 mIU/L) may increase risk of postoperative atrial fibrillation 9

When Surgery Cannot Be Delayed in Hyperthyroid Patients

When surgery is necessary without achieving euthyroidism, a multidisciplinary approach focusing on cardiovascular stability is essential. 2

Factors necessitating urgent surgery despite hyperthyroidism include:

• Medication allergies or intolerable side effects 3, 6
• Treatment-resistant disease 2
• Patient noncompliance 2
• History of thyroid storm requiring definitive treatment 3
• Compressive symptoms or malignancy concerns 2

Preoperative Optimization Protocol

Beta-blockade is the cornerstone of preoperative preparation, more important than achieving normal thyroid hormone levels. 1, 2

• Start beta-blockers (atenolol or propranolol) for symptomatic relief and cardiovascular stabilization 1
• Evaluate thyroid function tests (TSH, free T4, free T3) before the procedure 1
• Ensure adequate hydration and supportive care throughout the perioperative period 1
• Monitor for signs of thyroid storm during and after the procedure for 24-48 hours 1
• Avoid etomidate for induction when possible, as it suppresses cortisol production 8, 9

Special Populations at Higher Risk

• Elderly patients: Cardiovascular complications are the chief cause of death after treatment of hyperthyroidism in this population 1
• Patients with underlying cardiac disease: At higher risk for complications when hyperthyroidism is present 1
• Patients with pulmonary artery hypertension: Can occur in hyperthyroid patients, increasing right ventricular load 1

Common Pitfalls to Avoid

• Do not delay surgery indefinitely waiting for perfect biochemical control if the patient is cardiovascularly stable with beta-blockade 2, 3
• Do not hold levothyroxine perioperatively in hypothyroid patients, as interruption destabilizes thyroid status and worsens surgical outcomes 8
• Do not overlook subclinical hypothyroidism (TSH 4.5-10 mIU/L), as even these patients face increased perioperative cardiovascular risks 8
• Do not forget to rule out adrenal insufficiency before treating hypothyroidism, as thyroid hormone accelerates cortisol clearance and can precipitate adrenal crisis 9
• Do not assume potassium iodide is mandatory: Only 2% of patients in a large series received KI without adverse outcomes 7

The Bottom Line

The evidence increasingly supports that cardiovascular stability—not biochemical euthyroidism—is the critical factor for safe surgery in hyperthyroid patients, while hypothyroid patients should ideally achieve euthyroidism before elective procedures but can safely continue levothyroxine perioperatively. 8, 1, 2, 3