Thyroidectomy

Indications - six Ms

• Malignancy/suspicion of
• Medical therapy failure
• Mechanical compression
• Menacing consequences of RAI
• Mediastinal extension
• Marred beauty (cosmesis with large goitre)

Extent of resection

• Total thyroidectomy
• Thyroid lobectomy/hemithyroidectomy - all tissue on one side, along with isthmus and pyramidal lobe if present
• Near-total thyroidectomy - <1g of tissue left near ligament of Berry
• Subtotal thyroidectomy - 3-5g tissue left - non-preferred
• Isthmusectomy

Pre-op:

• Cord check if:
  • Total thyroidectomy
  • Completion thyroidectomy
  • Pt symptomatic (voice)
  • Thyroidectomy for cancer
• Biochemical assessment of thyroid and parathyroid function
  • If hyperthyroidism is present, attempt to render euthyroid by time of operation
• Appropriate imaging studies +/- biopsy
• Nerve monitor
  • Electrical stimulator current delivered to RLN (intermittent monitoring - more common) or vagus (continuous monitoring), which leads to electromyographic signal at the vocal cord detected by contact electrodes embedded on the surface of the ETT
  • Multiple studies have failed to demonstrate a significant benefit in reducing RLN injury, including 2019 Cochrane review and 2022 meta-analysis
  • Technique (intermittent)
    • Place probes at start of case
    • Visual identification and direct stimulation of RLN
    • Final reconfirmation of intact RLN after completion
    • Can be useful to confirm normal function of RLN before proceeding to the other side in a total thyroidectomy

Technique

TT, GA (?with nerve monitoring ETT), shoulder roll and head ring with neck extended, supine with back raised 20 degree, arms tucked in, headlight/loupes

• Nerve monitoring - 2x external leads inserted to skin and taped down with tegaderm

Prep and drape, IV Abx (although there is no proof for thyroidectomy), TEDs

Mark anatomy - borders of SCM, manubrium, midline

Incision between medial edges of SCM, finger's breadth above sternum

Through platysma

Dissection to raise upper and lower sub-platysmal flaps

• Develop inferior flap to level of sternal notch, upper flap to thyroid notch
• Aware of anterior jugular veins - can be suture ligated if necessary

Joll's retractor

Lateralise strap muscles (can be divided transversely if large goitre)

Dissect larger side of thyroid first, with primary operator standing on contralateral side

• Use peanut to dissect loose areolar tissue between gland and strap muscle towards lateral edge
• Lateralise dissection but don't need to go too far

Upper pole

• Clear as much of upper pole as you easily can using blunt dissection, peanut, right angle
• Open up Reeve's avascular space (medial) with blunt dissection
• Ligate individual terminal branches of superior thyroid artery close to capsule
• Look for EBSLN and protect, but don't go chasing too much
• Complete upper pole and look for upper parathyroid

• If bleeding here, pack, sort out lights/assistant etc, usually the vessel doesn't retract too far, so just be careful and localise it. Danger is in damaging the parathyroids in a panicked hunt for the vessel.

Middle pole

• Roll thyroid medially with gentle traction - retracting in the axial plane, not rotating the upper pole, to avoid distorting RLN's path
• Follow dissection caudally, ligating middle thyroid vein branches as you go
• Be very aware of RLN and try to keep a bloodless field (can either identify it at the top or the bottom)
• Tubercle of Zuckerkandl

Finding RLN

• Should be in tracheoesophageal groove
• Runs near suspensory ligament of Berry (most common site of injury) - almost always posterolateral to the fibres
• Tubercle of Zuckerkandl

Lower pole

• Continue caudally
• Ligate ITA branches as you go - take close to thyroid capsule - RLN can be closely associated, and also don't want to devascularise parathyroid
• Look for lower parathyroid gland
  • Auto-transplant if it is intra-thyroid, appears dusky, or has no vascular pedicle

Ligament of Berry divided and enter avascular plane between thyroid isthmus and trachea

Change to other side - swap sides with assistant

Inspect anterior mediastinum

Haemostasis

Reapproximate strap muscles

LA - Erb's point - 2-3cm above the clavicle at the posterior border of SCM

Close platysma

Lost signal:

• False loss:
  • Monitoring equipment dysfunction - check electrodes, connections, monitor, stimulating probe (touch muscle)
  • ETT malposition - most common - check with video laryngoscope
  • Muscle relaxant
• True loss
  • Injury
• Differentiate by testing either contralateral vagus or ipsilateral RLN at entry point
• If true loss: map RLN; generally don't perform contralateral side; recheck at end of operation; open disclosure with patient on awakening; post-op FNE

Hemithyroidectomy

• May or may not need levothyroxine (overall only 20% need it). The following factors affect it.
  • Remnant thyroid volume
  • Pre-op TSH level
  • Thyroiditis
  • Cancer (73% of patients having lobectomy for cancer need supplementation, whereas 38% with benign pathology)

Post-op:

Thyroid supplementation

• • Benign disease
    • 1.6mcg/kg levothyroxine daily
      • If >65yo get lower dose
      • Round to nearest 25microg
    • Check TSH 6/52 post-op and adjust thyroxine to keep TSH in normal range
    • Then annual TSH levels
    • For hemithyroidectomy for benign disease, don't start anything, but check TSH  6/52 post-op. Might need some.
  • Malignant disease
    • Depends on stage of disease, aggressiveness of cancer, and need for RAI
    • If starting RAI within 2-3/52: discharge home without thyroxine
    • If not starting RAI, give liothyronine (T3) 10-25mcg BD, then discontinue that 1-2/52 prior to RAI
    • After RAI, maintain on levothyroxine at 1.6mcg/kg daily

Calcium/calcitriol (based on Monash Health guidelines)

• • Relevant medications
    • Calcium given as calcium carbonate (Caltrate, which comes in 600mg tablets)
      • If taking PPI or have had gastric bypass, could use calcium citrate instead, as it is absorbed better in low-acid environments, although the difference is probably not that much
      • Hypocalcaemia symptoms - paraesthesiae of fingertips and perioral, progressing to frank tetany and respiratory compromise
    • Calcitriol (vitamin D3)
      • Give if very low or undetectable PTH levels
      • Austin strategy seems to be to give it whenever you give calcium
      • However the textbook guidance seems to be that it is only necessary at higher doses of caltrate
  • Typical plan for an operation where all four glands may have been compromised
    • Commence Caltrate 1.2g BD immediately post-op
    • Measure PTH 1 hour post-op and calcium the next morning
      • PTH >1.6pmol/L and corrected calcium >2mmol/L: discharge
      • PTH 0.6-1.6pmol/L: monitor with BD serum calcium. Discharge day 2 if corrected calcium stays >2mmol/L; otherwise need to start Calcitriol 0.5microg BD and increase Caltrate to 1.2g TDS.
      • PTH <0.6pmol/L: Commence Caltrate 1.2g TDS and Calcitriol 0.5microg BD and monitor calcium BD. Discharge on day 2 if corrected calcium remains >2mmol/L.
      • If corrected calcium is <2mmol/L, either add more oral supplements or IV calcium gluconate.
    • Ongoing need for calcium:
      • If just on Caltrate:
        • Recheck calcium at one week. If >2mmol/L, reduce to Caltrate 600mg BD.
        • If calcium stays >2mmol/L at two weeks, reduce to 600mg Caltrate daily.
        • If calcium is normal the next week, cease Caltrate.
      • If on Caltrate and calcitriol:
        • Recheck calcium at one week. If calcium >2mmol/L, reduce to Caltrate 1.2g BD and calcitriol 0.25microg BD.
        • At two weeks, if calcium is >2mmol/L, reduce to Caltrate 600mg BD and calcitriol 0.25microg daily.
        • At three weeks, if calcium is >2mmol/L, reduce to Caltrate 600mg daily and cease calcitriol.
        • At four weeks, if calcium is >2mmol/L, cease Caltrate.

Complications

RLN injury

• Ipsilateral VC palsy (4-10% temporary, 0.5-2% permanent)
  • Normal voice in 20%

Haematoma (0.1-1.1%)

• Risk factors
  • Inflammatory thyroid conditions
  • Partial thyroidectomy
  • CKD
  • Bleeding disorders
  • Graves' disease
  • Benign pathology
  • Antiplatelet/anticoagulation medications
  • Use of a haemostatic agent
  • Use of a drain
• Presentation
  • Seen sometimes obviously as a large, tense, firm, immobile anterior or lateral cervical swelling under the incision
  • Subtle signs:
    • Discomfort
    • Agitation
    • Anxiety
    • Difficulty in breathing
• Management
  • If any sign of airway compromise: open neck at the bedside using the SCOOP approach
    • Skin exposure
    • Cut sutures
    • Open skin
    • Open muscles
    • Pack wound
  • If no concern for airway compromise: evacuate in the operating room.
    • Prep neck and open haematoma prior to intubation
    • Secure airway
    • Completely evacuate haematoma and establish haemostasis
    • Sometimes leave intubated overnight while swelling settles

Superior laryngeal nerve injury (about 2.5-28%)

• Paresis of ipsilateral cricothyroid muscle -> inability to tighten the ipsilateral cord
• Vocal fatigue, decreased high pitch range, decreased projection

Hypoparathyroidism (permanent in 3%, temporary in 5-15%)

• Occurs due to either direct injury or devascularisation of parathyroid glands

F/U:

• 2/52 post op
  • Wound
  • Voice changes, subtle hypocalcaemic sx
  • Dosages of supplements
  • Review pathology
  • Discuss future plans
  • Co-ordinate multi-disciplinary care
• 6/52
  • TSH