Endocrine Surgery



Endocrine Surgery


Julia Park MD1

Dana T. Lin MD1

Ralph S. Greco MD1

Sara Nikravan MD2

Frederick G. Mihm MD2


1SURGEONS

2ANESTHESIOLOGISTS




EXCISION OF THYROGLOSSAL DUCT CYST


SURGICAL CONSIDERATIONS

Description: Thyroglossal duct cysts typically are located in the midline at or below the hyoid bone (Fig. 7.11-1). Differential diagnoses after initial physical exam include epidermoid cysts or lymph nodes. Cysts should be removed because of an associated high risk of infection with oral flora and a slight (< 1%) risk of either squamous-cell or papillary-thyroid cancer developing in the cyst itself. A transverse skin incision is made over the cyst, and if the cyst was previously infected and sinus tracts through the skin are present, the skin should be removed along with the cyst. The cyst is identified and followed cephalad to the hyoid bone (Fig. 7.11-2). Then, the midportion of the hyoid bone is resected to minimize recurrence. There may be many small tracts associated with the cyst that tend to attenuate beyond the hyoid bone. The base of the tract or tracts is resected up to the level of the floor of the mouth at the foramen cecum and ligated with absorbable suture (Sistrunk procedure). The wound is irrigated copiously and closed in layers. The wings of the hyoid bone are not reapproximated.

Usual preop diagnosis: Thyroglossal duct cyst






Figure 7.11-1. Location of thyroglossal duct cysts. (Reproduced with permission from Greenfield LJ, Mulholland MW, Oldham KT, et al, eds: Surgery: Scientific Principles and Practice, 3rd edition. Lippincott Williams & Wilkins, Philadelphia: 2001.)



▪ SUMMARY OF PROCEDURE






































Position

Supine, with neck in hyperextended position


Incision

Transverse skin incision


Unique considerations

Surgeon may request assistance, by placing finger at base of tongue to identify the cephalad extent of the needed dissection.


Antibiotics

Cefazolin 1-2 g iv


Surgical time

1-1.5 h


Closing considerations

Careful hemostasis. Coughing may be associated with venous congestion and hematoma formation.


EBL

5-10 mL


Mortality

< 0.1%


Morbidity

Bleeding: < 5%


Infection: < 5%


Pain score

3-4





▪ PATIENT POPULATION CHARACTERISTICS




















Age range

6 mo-30 yr (40% present at < 10 yr)


Male:Female

1:1


Incidence

˜ 1:3000


Etiology

Persistence of undifferentiated epithelial cells in area of hyoid bone that later become squamous-cell epithelium or glandular tissue







Figure 7.11-2. Thyroglossal duct cyst excision. A: Incision placed over presenting cyst; no skin excised. B: Cyst has been dissected from surrounding tissues, and hyoid is exposed after division of sternohyoid and thyrohyoid muscles at insertion. The bone is encircled with a short right-angle clamp 1 cm from its midpoint, where it is divided with a bone cutter or cautery. (Reproduced with permission from Baker RJ, Fischer JE: Mastery of Surgery, 4th edition. Lippincott Williams & Wilkins, Philadelphia: 2001.)



ANESTHETIC CONSIDERATIONS

See Anesthetic Considerations following Thyroidectomy, p. 674.



Suggested Readings

1. Gauger PG: Thyroid gland. In: Mulholland MW, Lillemore KD, Doherty GM et al, eds. Greenfield’s Surgery, Scientific Principles and Practice, 4th edition. Lippincott Williams & Wilkins, Philadelphia: 2006, 1289-309.

2. Organ GM, Organ CH: Thyroid gland and surgery of the thyroglossal duct: exercise in applied embryology. World J Surg 2000; 24(8):886-90.

3. Tracy TF Jr, Muratore CS: Management of common head and neck masses. Semin Pediatr Surg 2007; 16(1):3-13.


THYROIDECTOMY


SURGICAL CONSIDERATIONS

Description: Thyroidectomy is performed through a transverse neck incision (Fig. 7.11-3), usually 6-8 cm long. In the traditional approach, the platysma muscle is divided sharply and subplatysmal flaps are developed superiorly and inferiorly. The two large anterior jugular veins must be avoided and are occasionally a source of blood loss, although rarely of any hemodynamic significance. Once the flaps are adequately developed, a spring or self-retaining retractor may be placed to expose the midline prethyroid fascia (median raphe). This is divided in the midline to expose the strap muscles, which can then be separated from the thyroid gland.

After the thyroid gland is exposed, resection can proceed. Resection may be total, subtotal (lobe + isthmus ± partial remaining lobe), or lobar. Degree of resection depends on diagnosis and may be modified based on operative findings. During this portion of the operation, hemostasis is critical to maintain adequate visualization. Resection of a lobe usually begins with ligation and division of the middle thyroid vein along the midlateral aspect of the gland (Fig. 7.11-4).

The superior pole is mobilized by controlling and dividing the superior thyroid vessels close to the thyroid capsule to avoid injury to the external branch of the superior laryngeal nerve. As the dissection proceeds, care is taken to identify and preserve the superior and inferior parathyroid glands. The lobe is retracted medially to expose the
tracheoesophageal groove. The recurrent laryngeal nerve (RLN) is then visualized and traced along its entire course. Its function may be confirmed using a nerve monitor. The gland is gently dissected away from the nerve and then mobilized off the trachea to complete the resection. Any enlarged or suspicious lymph nodes are also excised and sent for pathologic examination. Before closing, hemostasis is ensured and can be tested with a Valsalva maneuver. The midline fascia and platysma are closed using absorbable suture and the skin with a running monofilament suture. The use of drains remains controversial and has not been shown to decrease the rate of hematoma formation.






Figure 7.11-3. Transverse incision at base of neck for thyroidectomy. (Reproduced with permission from Baker RJ, Fischer JE: Mastery of Surgery, 4th edition. Lippincott Williams & Wilkins, Philadelphia: 2001.)






Figure 7.11-4. Vascular relationships to the thyroid gland. (Reproduced with permission from Greenfield LJ, Mulholland MW, Oldham KT, et al, eds: Surgery: Scientific Principles and Practice. Lippincott Williams & Wilkins, Philadelphia: 2001.) Inset shows patient positioning with neck extended.

Minimally invasive techniques, such as video-assisted mini-incision or remote-access thyroidectomy via an endoscopic or robotic approach, have been described but have not gained widespread use. Video-assisted thyroidectomy has been shown to have similar rates of cure with superior voice preservation, improved cosmesis, shortened hospitalizations, and faster patient recovery when compared with conventional open surgery. Remote-access procedures have utilized various entry sites to reach the thyroid, namely, the anterior chest wall, breast, axilla, and post-auricular area through a facelift incision. Remote-access surgery avoids the presence of a cervical scar altogether while offering enhanced visualization and dexterity as well as comparable postoperative outcomes. Limitations that have prevented widespread adoption of these minimally invasive approaches include narrow patient selection criteria (based on the nature, size, and extent of thyroid pathology as well as body habitus), surgeon inexperience, lengthy operative time, and greater cost.

Intraoperative nerve monitoring (IONM) is increasingly being used as an adjunct to identify, dissect, and confirm the function of the recurrent laryngeal nerve. Specialized endotracheal tubes are inserted with surface electrodes contacting the luminal surface of the vocal cords on either side. The electrodes are connected to a monitoring device that continually senses EMG activity of the thyroarytenoid muscles. When the surgeon stimulates the RLN using a probe wired to the monitor, the device detects the electrical impulse from the vocal cords and sounds an audible alert, as well as a visual signal in some systems.

Usual preop diagnosis: FNA findings of definite/suspicious/inconclusive for malignancy; goiter; thyroid cancer (papillary, follicular, medullary, anaplastic); thyroid nodule; hyperthyroidism; Graves’ disease




▪ SUMMARY OF PROCEDURE









































Position

Supine with head elevated to 30° and neck extended (see Fig. 7.11-4, inset)


Incision

Transverse cervical


Unique considerations

Patients with uncontrolled hyperthyroidism are at ↑ risk for developing thyroid storm during surgery. Hyperthyroidism may be controlled preop with either ß-adrenergic blockade or propylthiouracil. Preop iatrogenic hypothyroidism may be associated with ↓ BP and circulatory collapse during induction of anesthesia.


Antibiotics

None routinely used


Surgical time

1-2 h


Closing considerations

Adequate hemostasis; minimize coughing


EBL

50-75 mL


Postop care

Observe for postop respiratory problems 2° recurrent laryngeal nerve injury (bilateral), hematoma, or ↓ Ca++. Admit ×24 h. [check mark] Ca++ the night of surgery and the following a.m. Same-day surgery remains controversial 2° delayed discovery of hematoma (16 h) and hypocalcemia.


Mortality

< 0.5%


Morbidity

Hypoparathyroidism (↓ Ca++): 3-5%


Hematoma: 1-2%


Thyroid storm (usually in association with Graves’ disease)


Wound infection: 0.2-0.5%


Recurrent laryngeal nerve damage


Unilateral (hoarseness): 0.77%


Bilateral (aphonia, respiratory obstruction): 0.39%


Pain score

3-4




▪ PATIENT POPULATION CHARACTERISTICS























Age range

15-80 yr


Male:Female

Overall: 1:8


Cancer: papillary (1:2); follicular (1:3); medullary; anaplastic; lymphoma (1:1)


Incidence

Cancer (uncommon) Benign (relatively common)


Etiology

Cancer (50%): papillary (80%); follicular (10%); medullary (5%); anaplastic (1%); lymphoma (1%) Benign lesions (50%): nontoxic goiter (20%); thyrotoxicosis (10%); thyroiditis (5%); benign nodules (5%); other (10%)


Associated conditions

Other endocrine disorders (e.g., pheochromocytoma in association with medullary thyroid carcinoma in patients with MEN 2A and 2B)



ANESTHETIC CONSIDERATIONS

(Procedures covered: excision of thyroglossal duct cyst; thyroidectomy)


PREOPERATIVE

Hyperthyroidism may be 2° Graves’ disease (common), toxic multinodular goiter, thyroid adenomas, TSH-secreting tumor (rare), or overdosage of thyroid hormone. Common Sx are fatigue, sweating, intolerance to heat, ↑ appetite, ↑ HR, ↑ BP, ↑ pulse pressure, ↑ T, weight loss or gain, thyroid goiter, and exophthalmos. Some older patients exhibit apathetic thyrotoxicosis, which is often mistaken for hypothyroidism. CHF and AF are common with these patients. Hypothyroidism may be iatrogenic or 2° autoimmune thyroiditis. Common Sx are intolerance to cold, anorexia, fatigue, weight gain or loss, constipation, ↓ HR, ↓ pulse pressure, ↓ DTR, ↓ T, ↓ mentation. An important aspect of
the preop visit is to ensure that the patient is in a physiologically euthyroid state (3 T, HR, pulse pressure, reflexes). Patients presenting for thyroidectomy usually are made euthyroid before surgery and may be taking one or more of the following medications: propylthiouracil, methimazole, potassium iodide, glucocorticoids, or ß-blockers.

General: Although cases have been reported describing total thyroidectomy for noneuthyroid patients with worsening cardiac function who have failed aggressive medical therapy (J Laryngol Otol 2012 July; 126(7):701-5).










































Respiratory

Beware of tracheal compression with large goiters, → tracheal deviation, stridor.


Tests: CXR; consider preop CT scan of neck to evaluate possible tracheal involvement, especially in patients with large goiters.


Endocrine


T4

T3ru

T3

TSH

Hyperthyroid

↑

↑

↑

Normal or ↓

1° hypothyroid

↓

↓

↓ or normal

↑

2° hypothyroid

↓

↓

↓

↓

Tests: Thyroid function; Ca++; Mg++; phosphate; alkaline phosphatase; glucose


Hyperthyroidism:



































Respiratory

↑ BMR → ↑ VO2 → rapid desaturation on induction.


Cardiovascular

↑ HR, AF (10-40% incidence), palpitations, CHF. A normal resting HR is helpful in determining whether the patient is ready for surgery. If the situation calls for it (e.g., emergency surgery), the patient can be treated with ß-blockers to blunt the sympathomimetic effects of the hyperthyroid state. ß-blocker therapy can be problematic in patients with CHF (titrate while monitoring filling pressures and CO).


Tests: ECG; consider preoperative ECHO for evaluation of LV function.


Neurological

Warm, moist skin, nervousness, anxiety (may require generous sedation), tremor, ↑ DTRs.


Musculoskeletal

Higher incidence of myasthenia gravis and skeletal muscle weakness (↑ sensitivity to muscle relaxants), clubbing of the fingers, weight loss, myopathy


Tests: CK, urine myoglobin, BMP


Hematologic

Mild anemia, thrombocytopenia


Tests: CBC


Gastrointestinal

Weight loss and diarrhea


Tests: BMP + others as indicated from H&P


Laboratory

Other tests as indicated from H&P


Premedication

Midazolam 1-2 mg iv. Continue antithyroid medications preop. Hyperthyroid patients must be made euthyroid before elective surgery and may be on the following drugs: propylthiouracil, methimazole, potassium iodide, ß-blockers, and glucocorticoids.


Thyroid storm

A life-threatening exacerbation of hyperthyroidism occurring during periods of stress, which is manifested by hyperthermia (> 40°C), tachycardia, widened pulse pressure, anxiety, altered mental state → psychosis → coma, and myopathy (rhabdomyolysis in 50%; severe in 4%). (Thyroid storm has been mistaken intraop for malignant hyperthermia, sepsis, anaphylaxis, and other hypermetabolic reactions, e.g., neuroleptic malignant syndrome.) Thyroid storm is most often associated with Graves’ disease that has been incompletely treated prior to surgery. General Rx: ↑ FiO2; fluid resuscitation; electrolyte replacement/ correction (↑ Ca++); cooling blankets; acetaminophen; maintain diuresis (maintain euvolemia) if rhabdomyolysis; treat precipitating event (infection, CHF, DKA, pregnancy).


Specific Rx: propylthiouracil (block synthesis) (200-250 mg po q 4 h); sodium iodide (block release; 1-2.5 g iv); steroids (mechanism unclear)—hydrocortisone (100 mg iv q 8 h), or dexamethasone (4 mg iv q 24 h); ß-blockers (use with caution in patients with reactive airway disease, AV block, or CHF)—propranolol (20-120 mg po q h or 0.25-1.0 mg iv q 5 min), and/or esmolol (50-300 mcg/kg/min). Note: Block synthesis BEFORE (1 h is adequate) giving iodides to block release, otherwise “iodine escape” will occur later.



Hypothyroidism:









































Respiratory

Beware of tracheal compression with large goiters → tracheal deviation, stridor. ↓ ventilatory response to ↑ CO2 and ↓ O2 (caution with opioids and sedatives).


Tests: CXR; consider preop CT scan of neck to evaluate possible tracheal involvement, especially in patients with large goiters.


Cardiovascular

Bradydysrhythmias, diastolic HTN, pericardial effusions, ECG → ↓ voltage, ST-T wave Δ’s, ↑ QT, occasional VT (torsades de pointe—pause-dependent). This type of VT is treated with MgSO4, cardioversion; then isoproterenol or pacing to shorten QT. Thyroid replacement must be weighed against the risk of precipitating myocardial ischemia in patients with known CAD. Diastolic dysfunction, ↓ LV compliance → cautious volume expansion.


Tests: ECG; consider preoperative ECHO for evaluation of LV systolic/diastolic function, pericardial effusion/tamponade.


Endocrine

Addison’s disease occurs in 5-10% of patients with severe hypothyroidism; some patients may receive a “stress dose” of steroids (hydrocortisone 100 mg iv q 8 h × 3) in the periop period.


Tests: Cortisol stimulation test


Neurological

↓ BMR → slow mentation and movement, cold intolerance, ↓ reflexes with “hangup” (delayed relaxation phase)


Musculoskeletal

Arthralgias and myalgias


Renal

Impaired renal function 2° amyloidosis, urinary retention, oliguria. (50% incidence of ↓ Na+)


Tests: Consider BUN; Cr; Na+


Hematologic

Coagulation abnormalities, anemia


Tests: CBC


Gastrointestinal

GI bleeding, constipation, ileus


Tests: As indicated from H&P


Laboratory

Other tests as indicated from H&P


Premedication

Midazolam 1-2 mg iv. (None in the patient who is clinically hypothyroid and requires emergent surgery.) Hypothyroid patients can safely undergo anesthesia/surgery if they have mild-to-moderate disease. Clinically hypothyroid patients (↓ HR, ↓ T, ↓ pulse pressure, ↓ DTRs) should be given thyroid replacement before elective surgery.


Myxedema comma

Severe hypothyroidism constituting a medical emergency, with mortality of > 50%. Manifestations include stupor or coma, hypothermia (which correlates inversely with mortality), hypoventilation with hypoxemia, bradycardia (HR 50-60), hypotension, apathy, hoarseness, and hyponatremia. Supportive measures: early intubation and mechanical ventilation; treat ↓ BP with cautious volume expansion (risk of pulmonary edema), inotropes (risk of arrhythmias), pacing (carefully, 60-70 b/min) and r/o pericardial effusion, passive rewarming only, especially if ↓ BP (active warming for T < 30°C); correct ↓ Na+ carefully (risk of Central Pontine Myelinolysis); correct ↓ glucose. Specific Rx: L-thyroxine (T4; 200-500 mcg iv loading dose, 100-300 mcg iv the next day); or tri-iodothyronine (T3; 20-50 mcg iv q 6-12 h); hydrocortisone (100-300 mg iv q d). T4 onset is slow (6 h after iv administration) and has to be converted peripherally (slowed in hypothyroid state) to biologically active T3. Also, T4 may be converted in some critically ill patients to biologically inactive rT3 (“reverse T3”). ↓ TSH level is the earliest sign of response.



INTRAOPERATIVE

Anesthetic technique: Normally, GETA; infrequently, under local anesthesia. If using IONM, insert the specialized endotracheal tube, preferably with the aid of a video laryngoscope, and ensure direct contact of the electrodes with the vocal cords on either side. A short-acting, nondepolarizing paralytic may be given to allow for full relaxation during intubation; however, long-acting neuromuscular blocking agents should be avoided. For inadequately treated hyperthyroid patients, it is important to establish an adequate depth of anesthesia to prevent an exaggerated sympathetic
response to surgical stimulation. Avoid agents that stimulate the sympathetic nervous system (e.g., ketamine, pancuronium, meperidine). Hypothyroidism may be associated with ↑ sensitivity to anesthetic agents and muscle relaxants.

































Induction

Standard induction for euthyroid patients (p. B-3). If the patient has airway compromise 2° a large thyroid goiter, consider an awake fiberoptic intubation (p. B-6). If using IONM, intubation via a video laryngoscope allows for both anesthesiologist and surgeon to visualize and confirm the position of the ETT electrodes in relation to the vocal cords.


Maintenance

Standard maintenance (p. B-3). Maintain muscle relaxation, except if using IONM (avoid paralytic agents). Use nerve stimulation to guide relaxant dosing.


Emergence

Airway obstruction 2° recurrent laryngeal nerve damage, tracheomalacia (especially in patients with large destructive goiters), or hematoma can occur. Consider visualizing vocal cord function before extubation.


Blood and fluid

Minimal blood loss


IV: 18 ga × 1


NS/LR @ 5-8 mL/kg/h


Head-up position

Slight head-up position can help make for a bloodless surgical field without substantially increasing the risk of VAE.


Monitoring

Standard monitors (p. B-1).

+ others as indicated by patient’s status (i.e., pulmonary artery catheter in the setting of emergent surgery in thyrotoxic patients with congestive heart failure). Maintain normothermia, especially in hypothyroid patients.


Positioning

[check mark] pad pressure points


[check mark] eyes

Supine, with head slightly hyperextended, allows for surgical exploration of the neck.


Complications

Cardiorespiratory depression

In hypothyroid patients, marked ↓ BP and ↓ RR may occur with minimal anesthetic doses.



POSTOPERATIVE


















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May 23, 2016 | Posted by in ANESTHESIA | Comments Off on Endocrine Surgery

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Complications

Recurrent laryngeal nerve damage

Bilateral: patient will be unable to speak and will require reintubation. CPAP may temporize situation and make reintubation less emergent. Unilateral: characterized by hoarseness.

Tracheomalacia or hematoma with airway compromise

Acute airway obstruction may occur immediately postop, and rapid reintubation may be lifesaving. If airway compromise is 2° hematoma, reopen incision and drain remaining blood; if patient still requires artificial airway, consider CPAP or awake reintubation.

Acute hypoparathyroid state (hypocalcemia)