What are the anesthesia considerations for a patient with hyperthyroidism?

Anesthesia Considerations for Patients with Hyperthyroidism

Patients with hyperthyroidism require careful preoperative optimization and specific anesthetic management to minimize perioperative complications and ensure optimal outcomes.

Preoperative Considerations

Thyroid Status Assessment

• Preoperatively, the anesthesiologist should review the patient's thyroid anatomy and physiology during the pre-anesthetic evaluation 1
• Evaluate thyroid function tests (TSH, FT4, T3) to determine the degree of hyperthyroidism 1
• Ideally, patients should be biochemically euthyroid before surgery, though mild to moderate hyperthyroidism may be acceptable with appropriate management 2, 3

Medication Management

• Continue antithyroid drugs (methimazole or propylthiouracil) until the day of surgery 2, 4
• Beta-blockers should be administered to control cardiovascular symptoms and continued perioperatively 2, 4
• For patients with severe hyperthyroidism, combination therapy may be needed, including iodine, corticosteroids, cholestyramine, or other agents 2

Airway Evaluation

• Assess for potential difficult airway due to:
  • Enlarged thyroid gland causing tracheal deviation or compression 1
  • Abnormal laryngeal structures 1
  • Presence of goiter that may impair swallowing or cause tracheomalacia 1
• Communicate any preoperative laryngeal examination findings to the anesthesiologist 1

Cardiovascular Assessment

• Evaluate for cardiac complications of hyperthyroidism (tachycardia, hypertension, arrhythmias, heart failure) 2, 5
• Ensure cardiovascular stability before proceeding with surgery 2

Intraoperative Management

Anesthetic Technique

• General anesthesia with endotracheal intubation is typically required for thyroidectomy 1
• Consider fiberoptic intubation or having a difficult airway cart available if airway concerns exist 1
• If nerve monitoring is planned, avoid long-acting neuromuscular blocking agents as they are absolutely contraindicated 1

Airway Management

• Select appropriate endotracheal tube size and type based on anatomy 1
• Consider laryngeal mask airway for some cases, which may provide a route for fiberoptic evaluation of recurrent laryngeal nerve integrity 1
• Be prepared for potential difficult intubation due to tracheal deviation or compression 1

Hemodynamic Management

• Monitor for signs of thyrotoxicosis: heart rate >100/min, systolic BP >180 or <60 mmHg, temperature >38°C 3
• Be prepared to administer beta-blockers intraoperatively (28.1% of hyperthyroid patients may require this vs. 8.5% of euthyroid patients) 3
• Maintain adequate hydration to prevent hypotension 2

Monitoring

• Standard ASA monitors plus consider invasive monitoring in severe cases 1
• Close temperature monitoring to detect early signs of thyroid storm or malignant hyperthermia 6
• Monitor end-tidal CO2 closely as increased levels may indicate thyroid storm or malignant hyperthermia 6

Potential Complications and Management

Thyroid Storm

• Characterized by hyperthermia, tachycardia, hypertension, and altered mental status 5
• Management includes:
  • Discontinue triggering agents (inhalational anesthetics) 6
  • Administer beta-blockers (propranolol) 6
  • Consider dantrolene if malignant hyperthermia is suspected 6
  • Administer corticosteroids (methylprednisolone) 6
  • Supportive care including cooling measures 5

Adrenal Insufficiency

• For patients on corticosteroids, provide stress-dose steroids:
  • Hydrocortisone 100 mg IV at induction, followed by continuous infusion of 200 mg/24h 1
  • Continue hydrocortisone 200 mg/24h by IV infusion while nil by mouth 1
  • Resume enteral steroid at double the pre-surgical dose for 48h after major surgery 1

Postoperative Complications

• Monitor for laryngeal edema, recurrent laryngeal nerve injury, tracheomalacia, and hypocalcemia 5
• Assess voice function immediately postoperatively 1
• Be prepared for possible airway compromise requiring re-intubation, especially in cases of large goiters with tracheomalacia 1

Special Considerations

Malignant Hyperthermia Risk

• Hyperthyroid patients may present with symptoms similar to malignant hyperthermia 6
• If a hypermetabolic state occurs during anesthesia (rising ETCO2, tachycardia, hyperthermia), consider both thyroid storm and malignant hyperthermia in the differential 6
• Dantrolene is effective for both conditions and should be administered promptly if either is suspected 6

Communication with Surgical Team

• Preoperative communication between surgeon and anesthesiologist is essential 1
• Discuss need for nerve monitoring, which affects choice of muscle relaxants 1
• Use a pre-procedural checklist to improve team communication and decrease patient errors 1