Anesthesia for Thyroidectomy

I.  Introduction

Thyroidectomy is surgical removal of all or part of the thyroid gland and is performed for:

• Benign nodular goiter
• Hyperthyroidism (Graves’ disease, toxic nodular goiter)
• Thyroid cancer
• Obstructive symptoms (dysphagia, stridor, dysphonia)

Types of Thyroidectomy:

• Total thyroidectomy – entire gland
• Hemithyroidectomy/lobectomy
• Subtotal/near-total thyroidectomy

II. Preoperative Considerations

A. History and Examination

🔹 Look for symptoms of:

• Hyperthyroidism: palpitations, tremors, heat intolerance, weight loss, anxiety
• Hypothyroidism: lethargy, bradycardia, cold intolerance, constipation
• Compressive symptoms: dysphagia, stridor, orthopnea
• Voice change: possible RLN palsy
• Past thyroid storm, antithyroid meds, radioiodine therapy
• SVC syndrome (facial swelling, venous engorgement)
• Duration of goiter (long-standing → ↑ tracheomalacia risk)

🔹 Airway exam:

• Tracheal deviation/compression (from large goiter or retrosternal extension)
• Fixed/swollen mass
• Assess for difficult intubation-Limited neck extension (due to mass or pain)

B. Investigations

C. Optimization

🔸 Hyperthyroid patients must be rendered euthyroid (ideally for 6–8 weeks).

🔸 Avoid surgery in thyroid storm/crisis. Ensure euthyroid status.

III. Intraoperative Management

A. Monitoring

• Standard ASA monitors
• Capnography: essential for ventilation, nerve monitoring
• Nerve integrity monitor (NIM) – RLN monitoring
• Arterial line if severe hyperthyroidism or large mass

B. Anesthetic Technique

C. Airway Management

• Difficult airway cart ready
• Anticipate tracheal deviation, compression
• Awake fiberoptic intubation if airway is compromised
• ETT should be cuffed and monitored for leak

D. Recurrent Laryngeal Nerve Monitoring

• Used in surgeries with malignancy, revision, or large goiter
• EMG tube or specialized ETT used (NIM tube)
• Avoid muscle relaxants after intubation (if MEP/EMG used)

E. Blood Loss and Fluid Management

• Usually minimal (<100 mL), but large goiters may bleed more
• Maintain euvolemia
• Crossmatch not routinely needed

IV.  Postoperative Management

A. Extubation

• Ensure full reversal and adequate spontaneous breathing
• Beware of airway edema, hematoma, bilateral RLN palsy
• Extubate only if confident of airway patency
• Consider delayed extubation or ICU observation for large masses or redo surgeries

B. Monitoring for Complications

V. 🔶 Special Situations

A. Retrosternal Goiter

• Difficult airway, tracheal compression
• May need sternotomy
• Plan awake fiberoptic or tracheostomy

B. Reoperative Thyroid Surgery

• Scarred anatomy, higher bleeding risk
• High risk of RLN injury and hypoparathyroidism
• Always use nerve monitoring

C. Thyroid Storm (Emergency)

• Rare, life-threatening thyrotoxicosis
• High fever, tachycardia, arrhythmias, agitation
• Emergency surgery contraindicated
• ICU management: cooling, beta-blockers, PTU, hydrocortisone

🔷 Special consideration for  Retrosternal Goiter and Tracheomalacia

A. Introduction

🟠 Retrosternal Goiter

• Definition: A goiter with ≥50% of its mass located below the thoracic inlet (mediastinum).
• Can cause tracheal deviation, compression, dysphagia, dyspnea, and SVC syndrome.
• May remain asymptomatic or present with signs of airway obstruction.

🟠 Tracheomalacia

• Definition: Weakening of the tracheal cartilage, leading to airway collapse, especially on expiration or after removal of chronic compressing masses (e.g., retrosternal goiter).
• Common in long-standing goiters due to pressure-induced tracheal atrophy.
• May not be obvious preoperatively, but becomes evident after mass removal when the trachea collapses.

B. Airway Management Plan

• CVP line avoided in SVC obstruction (unless femoral access)

C. Induction of Anesthesia

• Maintain spontaneous ventilation
• Use sevoflurane or TIVA with dexmedetomidine/remifentanil
• Avoid neuromuscular blockade till airway is secured |
  | Intubation | Smaller ETT may be needed due to narrowing
• Use reinforced tube
• AFOI or fiberoptic-guided intubation under sedation |
  | Muscle Relaxants | Only after securing airway and confirming ventilation |
  | Backup | Rigid bronchoscope, tracheostomy tray, CPB/ECMO if needed |

D. Management of Tracheomalacia

A. Intraoperative Diagnosis

• Difficulty maintaining airway patency after mass removal
• Tracheal collapse seen on bronchoscopy
• Sudden desaturation, difficulty ventilating, or loss of capnograph waveform

B. Management

VI. 🔶 Viva/MCQ Pearls

• Which nerve is most at risk in thyroidectomy?
  ➤ Recurrent laryngeal nerve
• Which electrolyte should be closely monitored post-op?
  ➤ Ionized calcium (hypocalcemia risk)
• Why is antithyroid preparation important before surgery?
  ➤ Prevent thyroid storm
• What is the ideal tube for RLN monitoring?
  ➤ EMG (NIM) tube
• Which surgical maneuver may cause vagal reflex bradycardia?
  ➤ Traction on thyroid gland