Anesthesiology

Thyroidectomy - Procedures

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What the Anesthesiologist Should Know before the Operative Procedure

Disorders of the thyroid gland usually involve some swelling or increase in thyroidal tissue. Surgery is typically superficial and in some cases can be performed under regional or local anesthesia by experienced surgeons.

The thyroid gland can become massive and sternotomy may be required to extirpate the gland. Often considered a minor operation, many patients may go home the same day. There is increasing tendency to perform these surgeries with video or robotic assistance.

The basic indication for thyroidectomy is to remove thyroid cancer. Most patients present with a simple thyroid nodule and are euthyroid. Additional indications include removal of thyroid nodules, managing hyperthyroidism, and relieving obstructive goiter.

Operations include thyroid lobectomy, lobectomy plus isthmusectomy, total thyroidectomy, central or lateral lymph node dissection, and radical neck dissection. Surgery is also performed for toxic multinodular goiter and to remove a functioning thyroid adenoma. Partial thyroid lobectomy and subtotal thyroidectomy are no longer performed.

“Goiter” has been used to describe any swelling of the thyroid gland, and can be classified as toxic or non-toxic, depending on the hormonal output from the gland. Thyroid masses or goiters usually grow slowly and are painless unless a sudden hemorrhage or the rare fast growing carcinoma is involved. Typical neck symptoms include the presence of a lump or uncomfortable swallowing. More rare symptoms, usually indicative of a more advanced disease or carcinoma, include dyspnea, hoarseness, and dysphagia.

When thyroidectomy is performed to remove a large goiter producing tracheal compression or to relieve tracheal stenosis, serious postoperative complications, including bleeding or nerve damage, may occur with greater frequency. Either complication may cause complete upper airway obstruction and hypoxic death. Other complications specifically related to surgery on the thyroid include life threatening hypocalcemia, tetany, and permanent hypothyroidism and hypoparathyroidism.

It is important to know the anatomy of the thyroid gland, especially as it relates to the anatomical course of the recurrent laryngeal nerves. One or both of these nerves may be injured as they travel in the tracheoesophageal groove and run along the medial surface of each thyroid lobe.

The anesthesiologist must know how to interpret thyroid function tests and understand the normal feedback loop that inhibits thyrotropin-releasing hormone (TRH) and thyroid-stimulating hormone (TSH) secretion by the two thyroid hormones (T3 and T4). Thyroid hormone production is increased by TSH, and both T3 and T4 are highly protein bound, but only the unbound form is active.

The thyroid takes up iodine and incorporates it into T3 and T4. Both are secreted into the circulation, although large amounts of iodine can inhibit their release. Propylthiouracil and methimazole both inhibit T3 and T4 synthesis. The patient’s basal metabolic rate can be doubled or halved with an excess or insufficiency of thyroid function, respectively. In some cases the surgeon will require or desire intraoperative nerve monitoring.

1. What is the urgency of the surgery?

What is the risk of delay in order to obtain additional preoperative information?

Most thyroid operations are elective, and the patient should have appropriate medical evaluation and treatment of co-morbid conditions before surgery is performed. Management of underlying cardiovascular or respiratory disease is appropriate, and the optimal approach should identify patients at high risk for cardiopulmonary complications and proceed accordingly.

Emergent: Thyroid surgery is rarely an emergency. However, some patients with stridor due to thyroid disease may present for emergency thyroidectomy to improve a critically obstructed airway. Patients may require emergency intubation and/or tracheostomy in cases involving tracheomalacia. In cases of autoimmune hyperthyroidism, a patient may be desperately submitted for surgery.

Urgent: Patients who present with dyspnea and respiratory insufficiency on the basis of a mass lesion compromising the airway or affecting vocal cord function require urgent surgical attention.

Elective: Thyroid surgery may be performed in several ways. Minimally invasive video assisted thyroidectomy and minimally invasive open thyroidectomy are becoming more common. Compared with conventional open techniques, all have an excellent safety profile, similar operative time, are associated with few complications and short or same-day hospital stay. Purported advantages of minimally invasive technique include less pain, shorter hospital stay, and improved cosmesis.

2. Preoperative evaluation

The anesthesia care team must understand the current endocrine state of the patient. Patients may exhibit signs of thyroid hormone deficiency or excess. Symptoms or signs of hypothyroidism warrant further evaluation and these may be subclinical or overt. Lab testing may be indicated. Signs of hyperthyroidism may range from mild to thyrotoxicosis. A change in thyroid hormone level may take days to manifest, as the half-life of T4 is six days and also depends on peripheral conversion to the more active T3 form.

Patients who are hypothyroid typically receive levothyroxine p.o., and return to a normal physiological state may take days to weeks, especially in the elderly. For patients who have mild decrease in thyroid function, no particular intervention is required.

Patients who must have surgery while clinically hypothyroid are more prone to CHF. Lower doses of anesthetic agents may be indicated, and patients should be carefully observed postoperatively for hypotension, sleep apnea, and airway compromise.

Patients with large thyroid goiters may suffer from symptoms including dysphonia, dysphagia, dyspnea, and a non-contrast chest CT may be helpful in assessing the extent of anatomic involvement of the mass in the neck and thoracic inlet. This study will alert the care team to potential difficulties in airway management or the need to open the chest to remove a retrosternal thyroid.

It is reasonable to assess the function of both recurrent laryngeal nerves prior to surgery to detect the preoperative patient who has an unsuspected recurrent laryngeal nerve palsy. This is especially true for patients having re-operative thyroid surgery.

Blood transfusion is rarely required, and type and screen is all that is usually necessary.

Routine preoperative screening and medical review is indicated as thyroid surgery is almost always elective. Patients with cardiac issues may proceed to surgery based on the American Heart Association/American College of Cardiology (AHA/ACC) Guidelines. Patients with chronic stable angina, hypertension, compensated heart failure and other conditions under medical treatment rarely need further workup or intervention prior to thyroid surgery.

Patients at risk for ischemic neurologic or cardiovascular events who take antiplatelet therapy should be reviewed with their primary doctor and specialist regarding the continuation of anti-thrombotic therapy.

Medically unstable conditions warranting further evaluation include but are not limited to recent coronary intervention, unstable angina or myocardial infarction, poorly compensated or recent congestive heart failure, recent reversible ischemic neurological deficit or stroke, recent bronchitis or flare of asthma or COPD, and any other major organ dysfunction.

Delaying surgery may be indicated with any of the medically unstable conditions listed above. If the patient exhibits major signs of hypothyroidism or hyperthyroidism, surgical morbidity and mortality are increased. For example, a patient with significant hypothyroidism may exhibit myopathy and be especially sensitive to neuromuscular blockade, or have a pericardial effusion increasing risk of perioperative hypotension and cardiovascular instability.

Hypothyroid patients are more prone to hyponatremia, hypothermia, and postoperative stupor. Drug metabolism may be greatly impaired, increasing the likelihood of CNS and respiratory complications.

3. What are the implications of co-existing disease on perioperative care?

Perioperative evaluation: Appropriate and complete historical data should be obtained. Specific laboratory tests should be reviewed and may include thyroid function tests. Careful patient assessment will reveal whether there is suspicion for associated medical conditions, including endocrinopathies, or autoimmune processes, such as diabetes mellitus, lupus erythematosus, rheumatoid arthritis, or adrenal insufficiency. These patients may require cortisol supplementation, may be hypovolemic, exhibit metabolic disarray, or have local disease impinging on vocal cord function or compromising airway patency.

Perioperative risk reduction strategies: Patients with hyperthyroidism have an increased number and sensitivity of beta adrenergic receptors. Thus, autonomic responses to laryngoscopy, intubation and surgical stimulation may be increased. Continuation of preoperative medical therapy, especially beta-blockade, is appropriate.

Patients with hypothyroidism may present a challenging mask airway or increased difficulty in visualizing the glottis secondary to an enlarged tongue. Appropriate alternative methods to ventilate and secure the airway, including appropriate sized supraglottic airways, video-laryngoscopes, fiber-optic laryngoscopes and the emergency airway cart may be appropriate to have in the operating room at the time of induction.

Emergence may be prolonged and extubation may result in partial or complete airway obstruction. Preparation with appropriate resuscitative equipment and development of a plan to manage airway compromise should occur as a discussion with the surgeon prior to extubation of high-risk patients.

There have been reports of thyroid storm triggered by palpation of the gland during thyroid surgery. Thyroid storm may also occur postoperatively, and if it does occur in the PACU or later, the symptoms and signs can mimic malignant hyperthermia, neuroleptic malignant syndrome, sepsis, or transfusion reaction.

The parathyroid glands are at risk during total thyroidectomy, as they lie at each of the four poles of the thyroid gland. Inadvertent removal will cause an abrupt drop of parathyroid hormone and blood levels of calcium ion. Hypoparathyroidism may cause symptomatic or life threatening hypocalcemia.

b. Cardiovascular system

Patients scheduled for thyroid surgery who are medically unstable, have hypotension or significant dysrhythmias, hypovolemia, or circulatory compromise should be stabilized before surgery. Patients with stable angina or CHF may require thyroidectomy for cancer or other indications. Appropriate medical assessment may include electrocardiogram, cardiac biomarkers, echocardiogram or cardiac consultation.

Symptomatic bradycardia or high degree atrio-ventricular block may require pacemaker placement. Patients with implanted cardiac rhythm management devices require active investigation of device functionality and device history. Patients with coronary artery stents must be individually reviewed regarding maintenance or discontinuation of anti-platelet therapy.

In most cases a thorough clinical history will suffice to develop an appropriate preoperative risk reduction strategy. The care team must be alert to changes in functional status, exercise tolerance, fatigue, and review prior electrocardiographic and other cardiac tests. Consultation with a cardiologist may be necessary. Low and intermediate risk patients can usually undergo thyroid surgery without formal preoperative cardiac testing.

Perioperative risk reduction strategies: Patients with severe coronary artery disease, low ejection fraction, or severe aortic stenosis may benefit from invasive monitoring using an arterial line placed prior to induction. Hemodynamic goals for patients with severe coronary disease are not specific for patients undergoing thyroid surgery and include optimizing the myocardial oxygen supply and demand ratio, maintaining an acceptable hemoglobin to ensure appropriate oxygen carrying capacity, managing heart rate, and maintaining coronary perfusion pressure.

There are several case reports of patients undergoing general surgery with concomitant use of an intra-aortic balloon to unload the left ventricle and optimize coronary perfusion.

c. Pulmonary

COPD:

The presence of COPD increases the risk of perioperative pulmonary complications, including increased secretions, atelectasis, pneumonia, bronchospasm, and hypoxemia. Preoperative evaluation should include a thorough history regarding smoking, recent colds, URI, COPD flares, bronchospasm, use of oxygen, use of steroids, CPAP, or change in use of medications and inhalers.

Thyroid surgery does not generally affect respiratory mechanics or diaphragmatic function.

Risk reduction strategies include optimizing pulmonary status through consideration of the use of nebulizers, steroids, antibiotics, chest physical therapy, pulmonary consultation, and incentive spirometry.

Reactive airway disease (Asthma):

The presence of asthma increases the risk of perioperative pulmonary complications including, increased secretions, atelectasis, pneumonia, bronchospasm and hypoxemia. Preoperative evaluation should include a thorough history regarding environmental or viral triggers, assessment of medications used, peak flow rates, the presence of smoking, recent colds, the use of steroids, URI, COPD flares, bronchospasm, the use of oxygen, CPAP, or changes in use of medications and inhalers.

Risk reduction strategies include optimizing pulmonary status, especially if peak flows are reduced. Surgery may be delayed if an asthmatic flare, wheezing, or secretions are present. Use of nebulized bronchodilators and anticholinergics, steroids, antibiotics, chest physical therapy, and pulmonary consultation may be indicated.

d. Renal-GI

Renal -

Patients are usually euvolemic and the assessment of volume status is routine. Obtaining a history of oral intake and examining vital signs is usually sufficient. Laboratory testing may or may not be indicated on the basis of local custom and the presence of co-existing disease.

Perioperative risk reduction strategies: Avoid potential nephrotoxic drugs when possible.

GI -

Patients are usually NPO, but may have reflux disease and/or hiatus hernia. Consider rapid sequence induction.

Perioperative risk reduction strategies: Make preparations to reduce the risk of pulmonary aspiration: consider promotility, gastric acid reducing, gastric volume reducing, and antacid medications as appropriate prior to general anesthesia.

e. Neurologic:

N/A

f. Endocrine

Hyperthyroidism may result from autoimmune Graves Disease (most common). Other causes include subacute thyroiditis, toxic multinodular goiter, factitious (oral ingestion of thyroid hormone), excess TSH secretion, and amiodarone induced thyrotoxicosis. Symptoms and signs include weight loss, nervousness, anxiety, shortness of breath, atrial fibrillation, tachycardia, tremors, goiter, and hyperactive reflexes. Thyrotoxic crisis manifests as a severe hypermetabolic state with many of the above signs and may lead to heart failure, hypotension, coma, and death. Medical treatment includes inhibiting production of thyroid hormone, blocking its effects, and plasmapheresis.

Manifestations of hypothyroidism are protean and include bradycardia, enlarged tongue, decreased cerebral function, low cardiac output, increased vascular resistance, pericardial effusion, and congestive heart failure.

Generally, any type of elective surgery, including surgery on the thyroid, should be postponed until the patient is euthyroid, and consultation with an endocrinologist may be warranted.

g. Additional systems/conditions which may be of concern in a patient undergoing this procedure and are relevant for the anesthetic plan (e.g., musculoskeletal in orthopedic procedures, hematologic in a cancer patient)

Patients with advanced thyroid disease may exhibit exophthalmos, and careful attention to eye protection during surgery is indicated.

4. What are the patient's medications and how should they be managed in the perioperative period?

Beta-blockers may be useful in mitigating sympathomimetic effects of increased thyroid hormone activity while monitoring for signs of heart failure. Beta-blockers, calcium channel blockers, digoxin, and amiodarone may play a role in controlling tachycardia from thyroid induced atrial fibrillation.

Patients on amiodarone may have hyperthyroidism due to amiodarone-induced thyroiditis, and thyroid function should be ascertained prior to surgery.

Cardiac medications

1.a. Beta blockers: patients on beta blockers should be continued perioperatively, with a goal heart rate less than 70 beats per minute, while watching for bronchospasm and hypotension from reduced contractility.

1.b. Starting beta blockers in intermediate- and high-risk cardiac patients may reduce adverse cardiac events perioperatively. However, studies have not elucidated the ideal length of therapy, if a particular beta blocker is more effective, or how long postoperatively a patient should continue therapy. Additionally, starting beta blockers perioperatively may be associated with an increased risk of stroke (thought to be due to hypotension) and death.

II. Statins—patients on statins should be continued perioperatively. Discontinuation is associated with increased risk of adverse cardiac events and mortality.

a. Starting statins in high-risk cardiac patients may reduce adverse cardiac events. However, studies are still looking at the length of therapy needed, dosing, titration parameters, and how long to continue postoperatively.

III. Aspirin—restart as soon as appropriate postoperatively. If a coronary stent is the indication for aspirin, then discuss discontinuation with cardiologist and have increased vigilance for perioperative myocardial ischemia and infarction.

IV. Clopidogrel—patients may be on IIB/IIIA platelet inhibitors for coronary stents. If so, evaluate for drug eluting versus bare metal stent, as well implant date. Discussion with patient, surgeon, and cardiologist may be necessary to determine optimal management, balance of risk of thrombosis/restenosis versus increased bleeding, and when to restart anticoagulation.

h. Are there medications commonly seen in patients undergoing this procedure and for which should there be greater concern?

All levothyroxine preparations are not bioequivalent. The two main anti-thyroidal medications are propylthiouracil (PTU) and methimazole (Tapazole). Patients may also be on immunosuppressive medications for thyroid eye disease. There are various side effects, including hepatotoxicity and agranulocytosis.

i. What should be recommended with regard to continuation of medications taken chronically?

Cardiac:

It is appropriate to continue treatment for cardiovascular conditions, including hypertension, on the patient’s regular schedule. Many anesthesiologists omit angiotensin converting enzyme inhibitors and angiotensin receptor blockers on the morning of surgery in an attempt to limit the amount and degree of perioperative hypotension that may occur in conjunction with providing general anesthesia.

Pulmonary:

Recommend continuing control medications (inhaled beta agonists, leukotriene inhibitors, inhaled steroid, and oral therapy) perioperatively. If moderate or severe, may consider additional therapy (inhaled beta agonists as a nebulizer, steroid course).

Neurologic:

Patients may be on anti-platelet therapy for cerebrovascular disease, and discussion with primary/surgical team should take place to assess risk of thrombosis/restenosis versus increased bleeding. Anti-epileptic and Parkinson’s medications should be continued perioperatively.

Anti-platelet:

See above for aspirin and clopidogrel. Once again, risk of restenosis/thrombosis needs to be balanced with increased bleeding from surgical site.

Psychiatric:

Continue anti-depressants and anti-anxiety medications perioperatively.

Herbals:

Herbal products are under no requirement to show safety or efficacy. Adverse cardiovascular events, increased bleeding, and interference with prescription drugs may occur with ingestion. It is reasonable to discontinue these products several days before thyroid surgery.

j. How to modify care for patients with known allergies -

N/A

k. Latex allergy- If the patient has a sensitivity to latex (e.g., rash from gloves, underwear, etc.) versus anaphylactic reaction, prepare the operating room with latex-free products.

If the patient has anaphylaxis with latex, versus a skin sensitivity (rash from wearing gloves), then prepare the OR with latex-free products. [

l. Does the patient have any antibiotic allergies- - Common antibiotic allergies and alternative antibiotics]

N/A

m. Does the patient have a history of allergy to anesthesia?

Malignant hyperthermia:

Avoid all trigger agents such as succinylcholine and inhalational agents:

A reasonable general anesthetic plan might include an infusion of propofol to insure amnesia and hypnosis, a remifentanil infusion to mitigate responses to noxious stimuli, plus or minus inhaled nitrous oxide. The use of neuromuscular blockade may depend on whether the surgeon requires intraoperative neuromonitoring.

Insure MH cart and dantrolene are available.

5. What laboratory tests should be obtained and has everything been reviewed?

The surgeon will order and review diagnostic thyroid ultrasound or other imaging study if indicated. The surgeon will also check thyroid function and calcium levels.

a. Hemoglobin levels:

Check hemoglobin if indicated.

i. Indications for transfusion: The decision to transfuse is based upon comorbidities/end organ damage, signs or symptoms of inadequate oxygen carrying capacity, presence of anaerobic glucose metabolism, as seen by lactic acidosis, continued blood loss, and blood pressure unresponsive to vasopressors.

I. Patients with end organ disease (cerebral, cardiac, pulmonary, renal) are often transfused below euvolemic hemoglobins of 10 to optimize oxygen carrying capacity to the organs.

II. pRBC transfusion is otherwise indicated for inadequate oxygen carrying capacity. Clinical assessment of cerebral and cardiac organs includes mental status, drowsiness, angina, arrhythmias, EKG changes, and hypotension.

b. Electrolytes

i. Potassium: Patients on potassium wasting diuretics or hemodialysis may have abnormalities.

ii. Sodium: Dehydration.

iii. BUN/Creatinine: Check if indicated; ratio greater than 20:1 often suggests hypovolemia.

c. Coagulation panel:

Check if indicated

d. Imaging:

Check if indicated. Thyroid function tests discussed above.

Common laboratory normal values will be same for all procedures, with a difference by age and gender.

Intraoperative Management: What are the options for anesthetic management and how to determine the best technique?

Most patients undergoing thyroidectomy require only routine airway management and can be managed with a standard general anesthetic, with no technique proven to be superior to another. General, regional and local (MAC) anesthetics have all been successfully described for these patients.

When the airway is compromised by extrinsic compression, invasive carcinoma, tracheomalacia, or other abnormalities, several important concepts come into play.

The anesthetist should be able to answer these questions:

1) Is there a change in breathing pattern or forced airflow?

If so, one must understand the anatomy and assess the risk of losing the airway during induction of general anesthesia.

2) Will the patient be intubated awake, asleep with muscle relaxants, or asleep with spontaneous ventilation to ensure adequate gas exchange?

This judgment must be made prior to induction of anesthesia.

3) Will muscle relaxants be used during the surgical procedure?

If a standard induction sequence is chosen, the use of muscle relaxants should be discussed with the surgeon, as some surgeons will choose to monitor recurrent laryngeal nerve (RLN) function intraoperatively. Administration of succinylcholine to optimize intubating conditions is a reasonable choice, as this relaxant should wear off before the surgeon’s knife approaches the RLNs. Alternatively, or in a patient with known or suspected pseudocholinesterase deficiency, several other methods to facilitate endotracheal intubation may be used, including:

a) achieving an anesthetic state with inhaled vapor

b) using sufficient opioid (such as remifentanil or fentanyl) to blunt coughing and prevent laryngospasm that might accompany intubation attempts without muscle relaxant.

c) using topical anesthetic to provide local anesthesia to the airway.

4) Is a specialized or armored endotracheal tube (ETT) required?

Some thyroid masses are extensive and a specially chosen ETT is indicated. The considerations regarding which ETT to use have to do with how much intraoperative pulling, bending, or tugging of the trachea will occur. An armored ETT, or an extra long (to pass beyond the area of tracheal compression) but narrow ETT have all been described to fit special uses in patients undergoing thyroidectomy.

5) Will the airway be managed with a laryngeal mask?

Thyroidectomy is routinely performed with ETT or LMA. A distinct advantage of the LMA is that bilateral vocal fold function can be assessed via fiberoptic endoscope placed through the lumen of the LMA both pre- and postoperatively. The LMA can also be placed at the end of the procedure, even while the ETT is in situ; this allows extubation to the LMA, offering the same advantages.

Regional anesthesia -

There are several reports of successful regional anesthesia, including cervical plexus block described for patients undergoing thyroid surgery. Conversion to general anesthesia may be required. When combined with intravenous sedation, regional anesthesia patients may have less nausea and decreased operating room time.

The advantage of this approach is that it allows the patient to communicate and avoid general anesthesia and airway manipulation. Contraindications for regional anesthesia include patient or surgeon preference, language barrier, claustrophobia, unfavorable surgical anatomy, and invasive cancer.

When regional anesthesia is contemplated in a patient with known or suspected difficult airway, consideration should be given to the degree of anticipated difficulty with securing the airway in case the block fails. Complications from deep or superficial cervical plexus block may include local anesthetic toxicity, hematoma formation, blockade of the cervical sympathetic chain, and the recurrent laryngeal nerve. Blockade of the phrenic nerve will lead to paralysis of the ipsilateral diaphragm. Injection of small amounts of local anesthetic into the vertebral artery or subarachnoid space will cause serious complications.

General anesthesia

General anesthesia for thyroid surgery is safe, effective, and almost always the first choice among anesthesiologists, surgeons, and their patients. The major benefits include an unconscious patient and an essentially immobile field, with no swallowing, phonating, coughing, or movement that might be associated with regional or monitored anesthesia care.

The airway is protected, patent, and secure when an ETT is in proper position, and positive pressure and CPAP can be applied to produce a Valsalva maneuver when the surgeon wants to increase venous pressure to check for venous oozing. When an LMA is used, the airway is not protected, although small amounts of positive pressure can be applied.

The drawbacks of general anesthesia include changes in hemodynamics, laryngospasm, postoperative delirium, or cognitive dysfunction.

Patients are typically positioned supine with the neck extended and a pillow or adjustable inflated balloon under both shoulders and the upper back. The intraoperative head position should be checked while the patient is still awake to ensure that the position is well tolerated, especially in the elderly, where cervical arthritis is common. The surgeon may prefer a head up position to allow for better venous drainage, but this position may make intra-operative air embolism more likely. The surgeon may desire an orogastric tube to help define the esophagus in some cases.

Both arms are often tucked, and it is worthwhile to make sure the intravenous line is freely flowing after the patient is positioned and draped but before surgery begins. Often the surgical team will lean against the upper arms, and thereby interfere with the automatic non-invasive blood pressure measurement. Extra extension tubing placed on the intravenous line and vasopressor infusions may allow for faster response time if intra-operative phenylephrine infusion is indicated.

Monitored Anesthesia Care

Reports of patients undergoing thyroid surgery under local anesthesia and monitored anesthesia care demonstrate that this technique is safe and effective in an experienced surgeon's hands. Purported advantages include functional assessment of vocal cord function, less bleeding as a result of spontaneous ventilation, lower intrathoracic pressure, faster recovery, lower costs, shorter operating room utilization, and decreased hospital stay.

6. What is the author's preferred method of anesthesia technique and why?

Before administering anesthesia, the surgeon must confirm the planned operation. Some surgeons will use the intraoperative nerve monitoring with an endotracheal tube. Our preferred choice of anesthetic is to implement general anesthesia with either an LMA or an endotracheal tube. The surgery is most easily performed with an immobile field and general anesthesia, with or without muscle relaxants, most reliably produces excellent operating conditions and stable hemodynamics.

There is a huge amount of literature showing that patients do well perioperatively with this technique. General anesthesia optimizes patient comfort, reduces coughing, and eliminates swallowing and movement of the thyroid gland during surgery. A variety of techniques, including benzodiazepines, opioids, propofol, inhaled vapor, nitrous oxide, muscle relaxants or total intravenous anesthesia have proven efficacy and safety profiles. We also typically prepare a phenylephrine infusion and titrate in order to maintain blood pressure within an acceptable range.

Postoperatively, a small amount of longer acting opioid, such as 3 to 5 mg of morphine sulfate or 0.5 to 0.8 mg of dilaudid is sufficient to provide pain relief.

What prophylactic antibiotics should be administered?

Perioperative antibiotic prophylaxis is generally not required for thyroid surgery, as surgical site infections are rare in clean surgery about the face and neck. In certain cases, cefazolin is administered within the hour prior to incision.

What do I need to know about the surgical technique to optimize my anesthetic care?

Since use of muscle relaxants are precluded when Intraoperative neuromonitoring (IONM) is used, there may be a greater likelihood that the patient may cough or respond with movement, especially during tracheal manipulation or other particularly noxious stimulation. Surgeons who employ IONM generally ask the anesthetist to place the specially prepared endotracheal tube with surface electrodes in careful alignment with the vocal cords to achieve the best intraoperative signal.

Complications

Complications unique to thyroid and neck surgery are notable for the relative significance of postoperative hematoma and bleeding, which may impinge on airway diameter and cause acute relative or absolute obstruction with resultant hypercarbia, dyspnea, stridor, hypoxemia, and death. When reoperation for neck hematoma is required, overnight observation and endotracheal intubation is a reasonable approach.

Since normal recurrent laryngeal nerve function allows the vocal cords to open (abduct), injury to one nerve causes narrowing of the glottic opening, and injury to both nerves will result in bilateral adduction or near-closure of the laryngeal inlet. It is vitally important to recognize and treat this devastating complication immediately. Injury to the nerves may be temporary or complete, and may require a temporary or permanent tracheostomy to prevent aspiration and ensure a patent airway.

The most frequent complication specific to thyroid surgery is profound hypocalcemia from removal of all parathyroid tissue. The surgeon will usually attempt to reimplant parathyroid tissue if they for losing all parathyroid function.

Other important complications following thyroid surgery include simple wound hematoma, a wound seroma which may not require immediate return to the operating room. Additionally, unilateral or bilateral recurrent laryngeal nerve injury, superior laryngeal nerve injury, hypoparathyroidism, and stridor or hoarseness from laryngeal or vocal fold edema occur, but are less common when high volume surgeons perform thyroid surgery.

a. Neurologic

None unique to thyroid surgery.

b. If the patient is intubated, are there any special criteria for extubation?

The anesthetist should ensure the patient is awake and alert and responds to commands.

c. Postoperative management

What analgesic modalities can I implement?

Postoperative pain is generally not difficult to manage, and small doses of opioids are appropriate. Patients should be observed for the development of neck swelling, hoarseness, stridor, and signs and symptoms of hypocalcemia. Appropriate postoperative monitoring, including pulse oximetry, should be used.

What level bed acuity is appropriate?

The choice of floor, telemetry, step down, or ICU admission depends on the patient’s preoperative comorbidities and intraoperative course.

What's the Evidence?

Randolph, GW, Kamani, D. "The importance of preoperative laryngoscopy in patients undergoing thyroidectomy: voice, vocal cord function, and the preoperative detection of invasive thyroid malignancy". Surgery. vol. 139. 2006.

(Preoperative examination of the vocal cords may diagnose occult nerve paresis.)

Hopkins, B, Steward, D. "Outpatient thyroid surgery and the advances making it possible". Curr Opin Otolaryngol Head Neck Surg. vol. 17. 2009. pp. 95.

(Thyroid surgery may be safely performed with minimally invasive techniques.)

Bratzler, DW, Houck, PM. "Antimicrobial prophylaxis for surgery: an advisory statement from the National Surgical Infection Prevention Project". Clin Infect Dis. vol. 38. 2004. pp. 1706.

(Antibiotics are not generally needed prior to clean surgery unless the patient is immunocompromised or has other medical issues.)

Sturgeon, C, Sturgeon, T, Angelos, P. "Neuromonitoring in thyroid surgery: attitudes, usage patterns, and predictors of use among endocrine surgeons". World J Surg. vol. 33. 2009. pp. 417.

(Relevance of intraoperative recurrent laryngeal nerve monitoring.)

Snyder, SK, Roberson, CR, Cummings, CC, Rajab, MH. "Local anesthesia with monitored anesthesia care vs general anesthesia in thyroidectomy: A randomized study". Arch Surg. vol. 141. 2006. pp. 167.

(Local anesthesia can be safely used for thyroid surgery.)

Spanknebel, K, Chabot, JA, DiGiorgi, M. "Thyroidectomy using monitored local or conventional general anesthesia: an analysis of outpatient surgery, outcome and cost in 1,194 consecutive cases". World J Surg. vol. 30. 2006. pp. 813.

(Large study of anesthetic technique for thyroid surgery.)

Rosato, L, Avenia, N, Bernante, P. "Complications of thyroid surgery: analysis of a multicentric study on 14,934 patients operated on in Italy over 5 years". World J Surg. vol. 28. 2004. pp. 271.

(A review of complications following thyroid surgery.)
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