What are the anaesthetic complications and peri‑operative management strategies for patients with hyperthyroidism or hypothyroidism undergoing surgery?

Anaesthetic Complications of Thyroid Disease

Hyperthyroidism: Perioperative Risks and Management

For hyperthyroid patients undergoing surgery, achieving biochemical euthyroidism preoperatively is ideal but not mandatory—cardiovascularly stable hyperthyroid patients can safely undergo thyroidectomy without increased risk of thyroid storm when managed by experienced teams. 1

Cardiovascular Complications

• Intraoperative hypotension occurs more frequently in thyroid-dysfunctional patients, requiring vigilant hemodynamic monitoring and preemptive vasopressor preparation 2
• Heart failure complicates cardiac surgery significantly more often in thyroid disease patients (29% vs 6% in controls), necessitating careful fluid management and cardiac optimization 2
• The cardiovascular system bears the brunt of hyperthyroid complications due to T3's direct effects on nearly every tissue 1

Preoperative Preparation Strategy

Combination therapy targeting thyroid hormone synthesis, secretion, and peripheral effects should be employed:

• Thionamides (methimazole or propylthiouracil) to block hormone synthesis 1
• Beta-blockers to control cardiovascular manifestations and block peripheral T4-to-T3 conversion 1
• Iodine (Lugol's solution or potassium iodide) to inhibit hormone release, typically started 7-10 days preoperatively 1
• Corticosteroids to further block peripheral conversion and provide stress-dose coverage 1

Critical Decision Point: Surgery in Hyperthyroid State

Recent evidence challenges traditional dogma—thyroidectomy can be safely performed during the hyperthyroid phase without precipitating thyroid storm when:

• The patient is cardiovascularly stable 1
• Experienced anesthesiologists and surgeons are available 1
• Factors preventing euthyroidism exist (drug allergies, side effects, treatment resistance, noncompliance, or urgency) 1
• Multidisciplinary evaluation by anesthesiologist, surgeon, and endocrinologist confirms cardiovascular stability 1

Common pitfall: Delaying necessary surgery indefinitely while attempting to achieve perfect biochemical control—preoperative treatment does not definitively prevent thyroid storm regardless of thyroid status 1

Hypothyroidism: Perioperative Risks

Hypothyroid patients face increased risk of several minor perioperative complications that require anticipatory management rather than absolute surgical contraindication. 2

Specific Complications

• Intraoperative hypotension occurs in 61% of hypothyroid patients versus 30% of controls, requiring aggressive fluid resuscitation and vasopressor readiness 2
• Gastrointestinal complications are significantly more common (19% vs 1%), including ileus and delayed gastric emptying 2
• Neuropsychiatric complications affect 38% versus 18% of controls, manifesting as delayed emergence, confusion, or delirium 2
• Blunted fever response to infection (35% vs 79% manifest fever despite comparable infection rates of 38% vs 33%), making infection surveillance more challenging 2

Anesthetic Considerations for Hypothyroidism

• Avoid etomidate for induction as it suppresses cortisol production in already vulnerable hypothyroid patients 3
• Anticipate and monitor for intraoperative hypotension with invasive monitoring when appropriate 3
• Use short-acting muscle relaxants if recurrent laryngeal nerve monitoring is planned 3
• No differences exist in perioperative arrhythmia, hypothermia, hyponatremia, delayed anesthetic recovery, wound healing, pulmonary complications, or mortality 2

Important caveat: Preoperative clinical and chemical features of hypothyroidism do not reliably identify patients at special risk—all hypothyroid patients require heightened vigilance 2

Airway Management Challenges in Thyroid Surgery

Preoperative Airway Assessment

Comprehensive airway evaluation must focus on:

• Neck mobility and extension capability 3
• Mouth opening and thyromental distance 3
• Signs of tracheal deviation or compression from goiter or mass effect 3
• Direct communication with surgical team regarding anticipated airway anatomy and recurrent laryngeal nerve monitoring plans 3

Induction and Intubation Strategy

• Videolaryngoscopy should be first-line technique, especially with any difficult airway predictors 3
• Use short-acting muscle relaxants only to preserve nerve monitoring capability 3
• Consider smaller tracheal tubes (6.0 mm internal diameter) as thyroid pathology may reduce glottic aperture 4
• Limit intubation attempts—multiple attempts worsen laryngeal edema and outcomes 4

Intraoperative Positioning

• Position patient supine with neck extended for optimal surgical exposure 3
• Consider prophylactic dexamethasone (0.15-1.0 mg/kg, maximum 8-25 mg) to reduce postoperative laryngeal edema 3

Life-Threatening Postoperative Complication: Haematoma

Postoperative haematoma occurs in 0.45-4.2% of thyroid surgeries and causes acute airway compromise requiring emergency bedside evacuation in up to 1:400 cases. 4

Recognition: DESATS Criteria

Do not wait for stridor—it is a late sign. Early recognition using DESATS criteria is critical: 5

• Difficulty swallowing
• Increase in Early warning Score
• Anxiety or agitation
• Tachypnea
• Stridor (late sign)

Emergency Management: SCOOP Approach

If signs of airway compromise exist, immediately open the wound at bedside using systematic SCOOP technique: 4

• Skin exposure
• Cut sutures
• Open skin
• Open muscles (superficial and deep layers)
• Pack wound

Essential Equipment and Preparedness

• Post-thyroid surgery emergency box must be at bedside during entire postoperative period, including transfers 4
• Emergency front-of-neck airway equipment (scalpel with #10 blade, bougie, cuffed 6.0 mm tracheal tube) must be immediately available on wards 4
• Minimum 6-hour postoperative monitoring required even for day-case procedures 4

Airway Management if Evacuation Fails

• Attempt tracheal intubation only after wound opening and haematoma evacuation to optimize conditions and prevent worsening laryngeal edema 4
• Use videolaryngoscopy at first attempt with smaller tracheal tube and bougie 4
• Early progression to front-of-neck airway if cannot intubate, cannot oxygenate—prefer scalpel cricothyroidotomy or emergency tracheostomy over cannula cricothyroidotomy 4
• Ongoing bleeding is not a contraindication to emergency front-of-neck airway 4

Institutional Requirements

• All staff potentially interacting with thyroid surgery patients (ward staff, doctors of all grades) must be trained to recognize haematoma 4
• Simulation-based training every 3 years minimum, with frequency reflecting staff turnover 4
• Explicit handover protocols from operating room to recovery to ward regarding bleeding risk 4
• Immediate senior surgical review (registrar or consultant) must be arranged if haematoma suspected; if unavailable or airway compromise present, senior anaesthetist informed immediately 4

Postoperative Monitoring

• Wound inspection, early warning scores, pain scoring, plus awareness for subtle signs (agitation, anxiety, breathing difficulty, discomfort) 4
• Head-up positioning and avoidance of excessive fluid administration to reduce airway edema 5
• Transfer to level 2 or 3 care for close observation following emergency evacuation 5