What are the preoperative management recommendations for a patient with hyperthyroidism (overactive thyroid) scheduled for surgery in the operating room (OR)?

Preoperative Management of Hyperthyroid Patients for Surgery

Patients with hyperthyroidism should ideally be rendered euthyroid before elective surgery using antithyroid medications (methimazole) combined with beta-blockers, though recent evidence demonstrates that thyroidectomy can be performed safely in the hyperthyroid state by experienced teams without precipitating thyroid storm. 1, 2, 3

Optimal Preoperative Preparation Strategy

First-Line Medical Management

• Initiate methimazole as the antithyroid drug of choice to block thyroid hormone synthesis, particularly for patients with Graves' disease or toxic multinodular goiter 1
• Add beta-blockers (propranolol or other beta-adrenergic blocking agents) to control cardiovascular manifestations including tachycardia and hypertension, which are the most prominent and dangerous aspects of hyperthyroidism 1, 4
• Consider combination therapy with thionamides, beta-blockers, iodine, and corticosteroids based on disease severity to prevent synthesis, secretion, and peripheral effects of thyroid hormones 2

Critical Preoperative Assessment

• Evaluate thyroid function tests (TSH, free T4, T3) to determine the degree of hyperthyroidism and guide treatment intensity 5
• Assess cardiovascular stability as the primary determinant of surgical readiness, focusing on heart rate control, blood pressure, and absence of heart failure 2, 4
• Review thyroid anatomy during pre-anesthetic evaluation to assess for potential difficult airway due to enlarged thyroid gland, goiter, or abnormal laryngeal structures 5
• Perform preoperative laryngoscopy for any patient with voice impairment, suspected extrathyroidal extension, prior neck surgery, or thyroid malignancy 6

When Euthyroid State Cannot Be Achieved

Evidence for Surgery in Hyperthyroid State

The 2016 American Thyroid Association recommendation to achieve euthyroidism before surgery is based on low-quality evidence and recent high-quality research challenges this dogma 3. A 2023 study of 275 hyperthyroid patients demonstrated that:

• No patient experienced thyroid storm in either controlled or uncontrolled groups undergoing thyroidectomy 3
• Uncontrolled patients (median free T4 of 3.1 ng/dL) had only slightly increased operative times and estimated blood loss compared to controlled patients 3
• Temporary hypocalcemia was the only significant difference (13.4% vs 4.7%) between uncontrolled and controlled groups 3

Indications to Proceed Without Euthyroidism

• Medication allergies or intolerance to antithyroid drugs 2, 3
• Treatment-resistant disease despite adequate medical therapy 2
• Patient noncompliance with medical management 2
• Urgency of definitive treatment (history of thyroid storm, severe symptoms) 3
• Cardiovascular stability achieved with beta-blockade even if biochemically hyperthyroid 2

Specific Perioperative Protocols

Anesthetic Considerations

• Ensure general anesthesia with endotracheal intubation for thyroidectomy procedures 5
• Have difficult airway equipment available including fiberoptic intubation capability if airway concerns exist 5
• Avoid long-acting neuromuscular blocking agents if intraoperative nerve monitoring is planned (absolutely contraindicated) 5
• Avoid etomidate for induction as it suppresses cortisol production 7

Medication Management on Day of Surgery

• Continue beta-blockers through the morning of surgery without interruption 1, 4
• Continue methimazole if the patient has been taking it preoperatively 1
• Administer stress-dose corticosteroids (hydrocortisone 100 mg IV at induction, followed by 200 mg/24h continuous infusion) if the patient has been on corticosteroids 5

Critical Preoperative Orders

• Rule out adrenal insufficiency before surgery, as hypothyroidism treatment is contraindicated until adrenal insufficiency is corrected (this principle applies to managing any thyroid disorder perioperatively) 7
• Monitor prothrombin time before surgery as methimazole may cause hypoprothrombinemia and increase bleeding risk 1
• Adjust doses of concurrent medications: digitalis glycosides, theophylline, and oral anticoagulants may require dose reduction as patients approach euthyroid state 1

Multidisciplinary Coordination

• Coordinate between endocrinologist, surgeon, and anesthesiologist to evaluate the patient's overall condition and comorbidities together, with particular attention to cardiovascular stability 2
• Use pre-procedural checklist to improve team communication and decrease patient errors 5
• Communicate need for nerve monitoring which affects choice of muscle relaxants 5

Postoperative Monitoring

• Monitor patients at least every hour for the first 6 hours postoperatively, as approximately half of hematomas occur within this timeframe 5
• Assess voice function immediately postoperatively and be prepared for possible airway compromise requiring re-intubation 5
• Watch for signs of thyroid storm including hyperpyrexia (>39°C), severe tachycardia (>140 bpm), agitation, and cardiovascular instability 8
• Monitor for hypocalcemia particularly in patients who underwent surgery in the hyperthyroid state 3

Common Pitfalls to Avoid

• Do not delay surgery indefinitely attempting to achieve perfect biochemical euthyroidism if cardiovascular stability is achieved with beta-blockade 2, 3
• Do not proceed without adequate beta-blockade even if antithyroid medications have failed, as cardiovascular manifestations pose the greatest perioperative risk 4
• Do not underestimate the risk of thyroid storm despite its rarity (incidence 0-14% across studies), as it remains a life-threatening complication requiring aggressive multidisciplinary management 9, 4
• Do not overlook medication side effects during preoperative preparation; patients should be cautioned to report sore throat, skin eruptions, fever, or general malaise suggesting agranulocytosis from methimazole 1
• Do not assume voice symptoms indicate vocal fold paralysis; up to 68% of vocal fold paralysis cases may be asymptomatic, making preoperative laryngoscopy essential in high-risk patients 6