Thyroid Surgery - MU

Principles of Thyroidectomy

• Must achieve absolute haemostasis
• All vessels must be ligated individually
• Mass ligation should be avoided even if commonly practiced
• Vessels to be ligated include the middle thyroid vein, the superior thyroid artery and vein, and the inferior thyroid vessels
• Use bipolar cautery
• Minimize or avoid monopolar cautery in the main dissection
• Lateral heat from monopolar cautery may damage the recurrent laryngeal nerve (RLN) or parathyroid blood supply
• Identify recurrent laryngeal nerve (RLN) and external laryngeal nerve (ELN) during dissection
• Prevent injury to the RLN and ELN
• Preserve the parathyroid glands
• Ensure cosmesis
• Use meticulous technique

Types of Thyroidectomy

Hemithyroidectomy

• Involves removing the entire one lateral lobe and the entire isthmus
• Retains the other lobe
• Used for benign diseases or follicular neoplasm of one lobe, solitary nodule (toxic or non-toxic), or thyroid cyst

Subtotal Thyroidectomy

• Most of the gland is removed
• Leaves only about 8 grams, or a tissue the size of the pulp of a finger, on the lower pole, on both sides
• Used for toxic thyroid (commonly, either primary or secondary) and multinodular goiter (MNG), either non-toxic (often) or toxic

Partial Thyroidectomy

• The role is controversial
• The gland in front of the trachea is removed after mobilization
• Some tissue in the tracheoesophageal groove is retained
• Used for nontoxic multinodular goiter

Near Total Thyroidectomy

• Most of both lobes of the gland is removed
• The lower pole of one side or both sides (less than 2 grams) is retained to safeguard the recurrent laryngeal nerve and parathyroid gland, which are very close
• Used for papillary carcinoma of thyroid

Total Thyroidectomy

• The entire gland is removed
• Nothing is retained
• Used for follicular or medullary carcinoma of the thyroid

Hartley Dunhill Procedure

• One entire lateral lobe and the isthmus are removed, along with a partial/subtotal removal of the opposite lateral lobe
• 4 grams of tissue of the opposite lobe is left
• Used for nontoxic multinodular goiter

Isthmectomy

• Used for advanced carcinoma or occasionally in Riedel's thyroiditis to treat severe stridor due to tracheal narrowing
• The isthmus should be removed entirely in any type of thyroidectomy
• If partially retained, it may adhere to the wound, creating a cosmetically poor scar

Surgery for Thyrotoxicosis - Pre-operative Preparations

• Patient should be euthyroid at the operation
• Preparation is outpatient and rarely needs admission to a hospital

Antithyroid Drugs

• Carbimazole is the drug of choice for preparation
• Dose: Carbimazole 30-40 mg per day
• When the patient is euthyroid (after 8-12 weeks), the dose can be reduced to 5 mg every 8 hours
• The last dose of carbimazole may be given on the evening before surgery

Mechanism

• Antithyroid drugs act on the target organs and not on the gland itself
• Propranolol inhibits the peripheral conversion of T4 to T3

Beta-Adrenergic Blocking Drugs

• Propranolol at 40 mg three times a day is an appropriate dosage
• Clinical response to beta-blockade is rapid
• Beta-adrenergic blocking drugs do not interfere with the synthesis of thyroid hormones
• Hormone levels remain high during treatment, and for some days after thyroidectomy
• Continue the drug for 7 days postoperatively

Iodine

• May be given with carbimazole or a beta-adrenergic blocking drug for the 10 days before operation
• iodide alone produces a transient remission & may ↓ vascularity, thereby marginally improving safety

Pre-operative Investigations

• Thyroid function tests
• Laryngoscopy (whether it is routine depends on local protocols)
• Thyroid antibodies
• Serum calcium estimation
• An isotope scan before preoperative preparation is necessary in patients with toxic nodular goiter if total thyroidectomy is not planned

Operative Procedure

Position

• Under general anesthesia
• Patient is in supine position with neck hyperextended by placing a sandbag under the shoulder
• The table should be tilted to 15-degrees head up

Incision

• Kocher's thyroid incision involves a horizontal crease incision two finger breadths above the sternal notch, from one sternomastoid to the other

Procedure

• Skin and platysma are incised (subplatysmal plane)
• Upper flap raised up to thyroid cartilage, lower flap up to sternoclavicular joint
• Deep fascia is opened vertically in the midline
• Superior pedicle is dissected; artery and vein are individually ligated and divided (dissection is done in an avascular plane between cricothyroid and gland)
• In olden days, mass ligation close to the gland at the superior pole was the practice
• There Is a chance of injuring the external laryngeal nerve and AV fistula may happen in mass ligation
• It is always better to identify the external laryngeal nerve entering the cricothyroid

Parathyroids

• Parathyroids, both superior and inferior, are identified
• Size: 6 x 4 x 2 mm
• Weight: 50 mg
• Color: Yellowish brown / orange brown
• Blood Supply for both glands: Receive their blood supply from the inferior thyroid artery and through an anastomotic branch
• Superior Parathyroid: Is above and behind the junction of RLN
• Inferior Parathyroid: Is below and in front of the inferior thyroid artery
• Parathyroids and their blood supply should be retained

Recurrent Laryngeal Nerve (RLN)

• RLN should be identified with careful dissection through its entire course
• Do not use monopolar cautery here; only bipolar cautery should be used carefully
• The nerve usually crosses the inferior thyroid artery from a deeper aspect, but variations are common
• Posterior extension of lateral thyroid lobes close to berry's ligament is called the zuckerkandl tubercle, which is seen in 40% of cases
• The nerve runs upwards in a fissure between the zuckerkandl tubercle and the trachea or main thyroid gland
• The RLN is in close contact with the suspensory ligament of berry

Inferior Thyroid Artery

• This is a branch of the thyrocervical trunk that ascends upwards, reaching the gland at its lower pole after turning towards the midline behind the carotid artery
• Ligation is done at the capsular level by identifying every small branch entering the gland (capsular ligation of inferior thyroid artery) (MCQ)
• This retains the blood supply of parathyroids, which is very important
• In olden days, ligation of the inferior thyroid artery was done away from the gland often in continuation using absorbable suture material, is now no longer in practice

Present Technique

• Ligate the inferior thyroid artery after the origins of its branches to the superior and inferior parathyroid glands

Older Technique

• Ligate the inferior thyroid artery away from the gland immediately after coming behind the CCA (carotid artery)
• The inferior thyroid artery Is ligated in continuity with absorbable (catgut) suture

Mobilized Gland

• The mobilized gland Is removed

Critical Points of RLN Injury

• At the entry of the inferior thyroid artery and crossing the nerve
• At the suspensory ligament of Berry
• At the lower pole of the gland

Closure

• The sandbag is removed and hemostasis is confirmed
• Stretched neck prevents bleeding from small veins, but once the sandbag is removed, they may bleed, which should be controlled
• A suction drain istraditionally placed, brought out through a separate stab incision or one of the ends of the main wound
• The drain should pass under the strap muscles to reach the thyroid fossa
• Strap muscles are approximated using interrupted 3-zero vicryl sutures
• The platysma is sutured using interrupted 3-zero vicryl sutures
• A Subcuticular absorbable 3-zero monocryl suture is used for the skin
• A soft light dressing may be ideal

MIVAT (Minimally Invasive Video-Assisted Thyroidectomy)

• Minimally Invasive Video-Assisted Thyroidectomy is becoming popular for small nodules and glands without thyroiditis
• It's costly but requires a trained surgeon

Post-Operative Complications

• Hemorrhage
• Respiratory obstruction
• Recurrent laryngeal nerve paralysis and voice change
• Thyroid insufficiency
• Parathyroid insufficiency
• Thyrotoxic crisis (storm)
• Wound infection
• Hypertrophic or keloid scar
• Stitch granuloma

Hemorrhage

• Causes: May be due to slipping of ligatures of superior thyroid artery or other pedicles or small veins
• Presentation: Tachycardia, hypotension and Dyspnea and compression over trachea may cause severe stridor, respiratory obstruction due to tension hematoma obstruct
• Management: release of sutures is the first step, then transfer to operation under general anesthesia, identify and ligate the bleeders (blood transfusion if needed)

Respiratory Obstruction

• May be due to hematoma, laryngeal edema (commonest cause), tracheomalacia, or bilateral RLN palsy
• Emergency tracheostomy may be required as a life-saving procedure

Recurrent Laryngeal Nerve Palsy (Positions of Vocal Cord Types)

Paralysis Evaluation

• Determine if unilateral or bilateral
• Assess paralyzed laryngeal muscles
• All muscles affected except cricothyroid in unilateral
• Both side intrinsic muscles for bilateral
• Position of vocal cords: median or paramedian

Unilateral Clinical Features

• Asymptomatic in 33% of cases
• There may be some change in voice, which gradually becomes normal with speech therapy
• Aspiration never occurs
• Airway obstruction never occurs

Bilateral Clinical Features

• Change in voice
• Severe dyspnea and stridor (more during exertion) leading to airway block and respiratory arrest

Management of Nerve Palsy

Unilateral Recurrent Laryngeal Nerve Palsy

• No specific treatment is required, but a steroid, such as Prednisolone 20 mg tid for 10 days orally after food with gradual tapering, should be started

Bilateral Recurrent Laryngeal Nerve Palsy

• Emergency tracheostomy
• Lateralization of cord by arytenoidectomy (open surgery or endoscope), vocal cord lateralization (endoscope), excision of vocal cord (endoscope or laser cordectomy), implantation of sternohyoid, or thyroplasty

Combined Recurrent Laryngeal & Superior Laryngeal Nerve Palsy

Unilateral

• Hoarseness of voice
• Aspiration through ineffective glottis
• Ineffective cough

Bilateral Recurrent Laryngeal & Superior Laryngeal Nerve Palsy

• Aphonia (no voice)
• Aspiration due to severe glottis incompetence and laryngeal anaesthesia
• Absence of cough
• Retention of secretions in the chest
• Respiratory arrest

Management of Combined Nerve Palsy

• Consider speech therapy, injection of Teflon to the paralyzed cord, muscle or cartilage implant, or arthrodesis of cricoarytenoid joint
• Consider emergency tracheostomy, fixing epiglottis over the arytenoids, plication of vocal cords, or total laryngectomy

Hypoparathyroidism

• Rare (0.5% common) and mostly temporary (vascular spasm of parathyroid glands), occurring on the 2nd-5th postoperative day
• Presentation: weakness, positive Chvostek's sign, carpopedal spasm, and convulsions
• Management: serum calcium estimation, calcium gluconate intravenously every 8 hours, oral calcium carbonate every 8 hours; stop drug if serum levels repeated

Earliest sign

• Muscle weakness is the earliest sign of Hypoparathyroidism

Thyrotoxic Crisis (Thyroid Storm)

• Occurs in 2% of patients
• Occurs in a thyrotoxic patient inadequately prepared for thyroidectomy or presents in a crisis following an unrelated operation or stress
• Could be due to other causes like infection, trauma, preeclampsia, diabetic ketosis, or emergency surgery
• Presents in 12-24 hours after surgery
• Symptoms: Severe dehydration, circulatory collapse, hypotension/palpitation, hyperpyrexia, tachypnea/hyperventilation, restlessness/tremor/delirium, diarrhea/vomiting, and cardiac failure/later coma

Treatment for Thyrotoxic Crisis

• Includes injection of hydrocortisone
• Cooling of the whole body
• Oral antithyroid drugs
• Oral iodides
• Beta-blocker injection
• Oral iodides
• IV fluids for rehydration and digoxin
• Cardiac monitor and ventilator support, with close observation
• Has a high mortality rate with a critical period of 72 hours

Late complications

Hypothyroidism

• Revealed clinically after 6 months

Wound Infection

• Stitch granuloma formation

Keloid Formation

Recurrent Thyrotoxicosis

• 5% common with etiology of retaining more thyroid tissue during thyroidectomy for toxic thyroid and is difficult to manage.
• Treated with antithyroid drugs, radioiodine therapy, or re-excision

Injury to External Laryngeal Nerve

• Causes weakness of cricothyroid muscle leading to alteration in pitch of voice and voice fatigue

Post-Operative Care

• Observe the patient for signs and symptoms of RLN palsy and hypoparathyroidism
• Remove drain if serous and minimal 24 hours after surgery
• Discharge patient on the second postoperative day