Anesthesia for patients with thyroid disease and for patients who undergo thyroid or parathyroid surgery

INTRODUCTION — Thyroid disease and thyroid surgery present specific challenges for anesthesiologists.

This topic reviews the perioperative anesthetic management of patients with thyroid disease and anesthetic management of patients who undergo thyroid or parathyroid surgery. Preoperative medical management of patients with thyroid disease, perioperative surgical management of patients undergoing thyroid surgery, and urgent management of severe and life-threatening overt thyroid storm are reviewed separately. (See "Nonthyroid surgery in the patient with thyroid disease" and "Surgical management of hyperthyroidism" and "Thyroidectomy" and "Thyroid storm".)

Perioperative risk as it relates to the degree of thyroid dysfunction is also discussed separately. (See "Nonthyroid surgery in the patient with thyroid disease", section on 'Surgical outcomes' and "Nonthyroid surgery in the patient with thyroid disease", section on 'Clinical manifestations that may impact perioperative outcome'.)

Parathyroidectomy may be performed for patients with primary or secondary hyperparathyroidism. Clinical manifestations of hyperparathyroidism and indications for surgery are discussed separately.

●(See "Primary hyperparathyroidism: Clinical manifestations".)

●(See "Primary hyperparathyroidism: Management".)

●(See "Refractory hyperparathyroidism and indications for parathyroidectomy in adult patients on dialysis".)

MULTIORGAN SYSTEM EFFECTS OF THYROID DISEASE — Patients with existing hyper- or hypothyroidism have associated physiologic changes that may affect anesthetic care and perioperative outcomes. Most such changes resolve with treatment as the patient becomes euthyroid.

Hyperthyroidism — Hyperthyroidism can be classified as subclinical (ie, low thyroid-stimulating hormone [TSH] with normal free T4 and T3), or overt (ie, suppressed TSH with elevated free T4 and/or T3). As the degree of hyperthyroidism increases, clinical manifestations are more prominent and have a greater potential impact on anesthetic care. In patients with overt hyperthyroidism surgery can, rarely, precipitate thyroid storm, a potentially life-threatening condition. (See "Overview of the clinical manifestations of hyperthyroidism in adults" and "Nonthyroid surgery in the patient with thyroid disease", section on 'Overt hyperthyroidism'.)

●Cardiovascular changes may lead to perioperative hemodynamic instability. Hyperthyroid patients have increased heart rate, circulating blood volume, cardiac contractility, and myocardial oxygen consumption, as well as enhanced diastolic relaxation and reduced systemic vascular resistance (table 1). Patients with hyperthyroidism are also prone to sinus tachycardia and atrial fibrillation, coronary spasm, and ischemia, and may develop cardiomyopathy over time [1-9]. (See "Cardiovascular effects of hyperthyroidism".)

●Hyperthyroidism does not increase minimum alveolar concentration (MAC) requirement [10,11]. However, induction of anesthesia may be slower and may require increased concentrations of inhaled anesthetics because of elevated cardiac output in patients with hyperthyroidism, and resultant effects on uptake and distribution of anesthetics. Patients with hyperthyroidism may have increased anesthetic requirements, primarily to control blood pressure and heart rate. There are no existing data supporting an increased MAC with contemporary inhaled anesthetics. Older animal studies demonstrated no clinically significant increase in halothane requirements [11]. (See "Inhalation anesthetic agents: Properties and delivery", section on 'Cardiovascular factors'.)

●Vasoactive medications should be chosen based on clinical and patient factors, independent of thyroid function (table 2 and table 3).

Patients with hyperthyroidism have been thought to exhibit increased sensitivity to catecholamines. Thus, the typical recommendation is that hypotension should be treated with direct acting vasoconstrictors (eg, phenylephrine) rather than with catecholamines or medications that release catecholamines (eg, ephedrine). However, evidence in support of this recommendation is indirect and conflicting. Some in vitro human studies have reported an increase in beta adrenergic receptor density in the heart in patients with hyperthyroidism [12-14]. However, there is also evidence that the increased receptor density may be counteracted to a degree by cellular changes that reduce adrenergic receptor responsiveness to catecholamines [15]. The net effect may be that cardiac adrenergic responsiveness is unaltered in patients with hyperthyroidism. (See "Cardiovascular effects of hyperthyroidism", section on 'Adrenergic effects'.)

●Respiratory muscle weakness occurs with hyperthyroidism, and in patients with severe hyperthyroidism, this may mandate postoperative mechanical ventilatory support after general anesthesia [16,17]. (See "Respiratory function in thyroid disease".)

Intraoperative thyroid storm — Thyroid storm is a rare, life-threatening condition characterized by severe clinical manifestations of thyrotoxicosis [18]. It has been reported during surgery and in the first 18 hours after thyroid and non-thyroid surgery in hyperthyroid patients, though the incidence is very low in patients who receive preoperative antithyroid treatment. (See "Nonthyroid surgery in the patient with thyroid disease", section on 'Thyroid storm'.)

The diagnosis of thyroid storm is based upon the presence of severe and life-threatening signs and symptoms (eg, hyperthermia, cardiac dysfunction, altered mentation) in a patient with biochemical evidence of hyperthyroidism. (See "Thyroid storm", section on 'Diagnosis'.)

During anesthesia, thyroid storm can be difficult to differentiate from malignant hyperthermia, which may share clinical characteristics.

●If clinical signs of thyroid storm develop during or shortly after surgery in a patient with known hyperthyroidism, therapeutic measures should be initiated immediately, including administration of a beta blocker unless contraindicated. An endocrinologist should be consulted urgently, and further treatment will likely include administration of a thionamide (eg, methimazole or propylthiouracil), though these drugs cannot readily be administered intravenously (see "Thyroid storm", section on 'Thionamides'). Other supportive measures include aggressive treatment of hyperpyrexia with cooling blankets and acetaminophen, administration of a glucocorticoid (eg, hydrocortisone), and treatment of metabolic abnormalities.

●In patients without known hyperthyroidism, and prior to laboratory confirmation of hyperthyroidism, it is reasonable to also manage the patient for malignant hyperthermia crisis (ie, administer dantrolene and discontinue potent inhaled anesthetics). (See "Malignant hyperthermia: Diagnosis and management of acute crisis", section on 'Acute management of suspected MH' and "Malignant hyperthermia: Diagnosis and management of acute crisis", section on 'Others'.)

Ongoing support and monitoring in the critical care setting is strongly recommended after surgery since the mortality rate is substantial in patients with thyroid storm [19]. (See "Thyroid storm", section on 'Initial management' and "Nonthyroid surgery in the patient with thyroid disease", section on 'Thyroid storm'.)

Hypothyroidism — Hypothyroidism may be classified as mild, moderate, or severe, as follows:

●Mild hypothyroidism – Subclinical, elevated TSH with normal serum free T4

●Moderate hypothyroidism – Elevated TSH, low free T4, without clinical features of severe hypothyroidism

●Severe hypothyroidism – Severe clinical symptoms such as altered mentation, pericardial effusion, or heart failure; myxedema coma; or very low levels of total T4 (eg, <1.0 mcg/dL) or free T4 (eg, <0.5 ng/dL). (See "Nonthyroid surgery in the patient with thyroid disease", section on 'Defining the severity of hypothyroidism'.)

Severe hypothyroidism has a greater impact on anesthetic care than mild or well-treated disease. Patients with moderate or severe hypothyroidism may exhibit exaggerated responses to anesthetic agents, sedatives and opioids, and appear to be at increased risk of perioperative complications. Case reports have described significant respiratory depression from opioids, vasopressor-resistant hypotension, and prolonged recovery from anesthetic agents in patients with severe hypothyroidism [20,21]. Studies of the pharmacokinetics and pharmacodynamics of sedatives and anesthetic medications in these patients are lacking, and it is unclear whether prolonged effects relate to reduced cardiac output and/or other physiologic effects, or are a direct result of thyroid dysfunction [22]. There is no evidence that these patients have a reduced MAC for contemporary inhaled anesthetics [23,24]. (See "Nonthyroid surgery in the patient with thyroid disease", section on 'Defining the severity of hypothyroidism' and "Nonthyroid surgery in the patient with thyroid disease", section on 'Surgical outcomes'.)

Physiologic effects of hypothyroidism that may affect anesthetic management include the following:

●Cardiovascular abnormalities may lead to perioperative hemodynamic instability or myocardial ischemia. Clinically hypothyroid patients may have bradycardia, diminished response to adrenergic agents, diastolic dysfunction, increased systemic vascular resistance, and impaired venous return (table 4) [1,2,25-27]. Patients with hypothyroidism, even subclinical disease, are at increased risk for ischemic heart disease [28,29]. (See "Clinical manifestations of hypothyroidism", section on 'Cardiovascular system'.)

●Hypothyroid patients may have a diminished response to alpha and beta adrenergic agents, and larger than usual doses of vasopressors may be required [30-32]. (See "Cardiovascular effects of hypothyroidism", section on 'Cardiac contractility'.)

●Obstructive sleep apnea is more common and should be suspected in patients with hypothyroidism (see "Respiratory function in thyroid disease", section on 'Obstructive sleep apnea').

Perioperative management of patients with obstructive sleep apnea is discussed separately.

•(See "Surgical risk and the preoperative evaluation and management of adults with obstructive sleep apnea".)

•(See "Intraoperative management of adults with obstructive sleep apnea".)

•(See "Postoperative management of adults with obstructive sleep apnea".)

●Respiratory effects of the hypothyroid state include impaired ventilatory drive and respiratory muscle weakness, which can lead to alveolar hypoventilation [33-35]. Also, hypothyroid patients are extremely sensitive to the effects of drugs that depress respiratory drive, such as opioids and sedatives [20,21,36].

●Patients with severe clinical hypothyroidism are at risk for delayed emergence and may require prolonged ventilatory support. (See "Respiratory function in thyroid disease".)

●Metabolic abnormalities may include hyponatremia due to a reduction in free water clearance, reversible increases in serum creatinine, and reduced clearance of hypnotic and opioid medications [37]. Other concerns include hypoglycemia, anemia, and hypothermia.

PREANESTHESIA EVALUATION — Preanesthesia evaluation always includes a medical history and anesthesia-focused physical examination, including airway examination. Testing should be determined by the patient's medical status and the surgical procedure. Preanesthesia evaluation is discussed in detail separately. (See "Preoperative evaluation for anesthesia for noncardiac surgery".)

Perioperative thyroid medication management is discussed separately. (See "Perioperative medication management", section on 'Drugs used for thyroid disease'.)

Euthyroid patients — For patients with known, treated thyroid disease, clinical euthyroid status should be confirmed during preanesthesia evaluation. Patients taking a stable dose of thyroid medication with documented euthyroid status within the past three to six months do not need additional testing prior to surgery. (See "Nonthyroid surgery in the patient with thyroid disease", section on 'Is preoperative measurement of TSH necessary?'.)

Patients with abnormal thyroid function — If history and physical examination suggest thyroid disease, it is reasonable to try to make a diagnosis, starting with laboratory thyroid function tests, since it can affect perioperative management. (See "Diagnosis of and screening for hypothyroidism in nonpregnant adults", section on 'Diagnosis' and "Diagnosis of hyperthyroidism", section on 'Diagnosis'.)

Elective surgery should be delayed in patients with recently diagnosed thyroid disease and in those who remain hyperthyroid or severely hypothyroid, until treatment results in a documented euthyroid state. If urgent or emergency surgery is required, patients with severe hypothyroidism or hyperthyroidism should receive treatment of their disease prior to surgery, as time allows, in order to minimize complications. (See "Nonthyroid surgery in the patient with thyroid disease", section on 'Hypothyroidism' and "Nonthyroid surgery in the patient with thyroid disease", section on 'Hyperthyroidism'.)

For emergency surgery in patients with moderately severe or severe hypothyroidism, advanced intraoperative monitoring (eg, continuous intraarterial blood pressure monitoring) may be indicated, and such patients may require intensive care postoperatively. Preoperative thyroid hormone replacement and postoperative concerns in such patients are discussed separately. (See "Nonthyroid surgery in the patient with thyroid disease", section on 'Management'.)

Airway evaluation — Preanesthesia evaluation always includes an airway assessment with the goal of predicting any potential difficulty with airway management (see "Airway management for induction of general anesthesia", section on 'Airway assessment'). While an enlarged thyroid (goiter) may cause airway compromise due to invasion of airway structures, extension into the mediastinum, and compression of the trachea, we do not routinely order imaging studies specifically to assess the airway in patients with thyroid disease or a goiter [38-40]. In two prospective studies of intubation in thyroidectomy patients, difficult endotracheal intubation was predicted most often by the usual anatomic predictive factors (table 5), rather than the size of the goiter or the presence of tracheal compression or deviation [38,41]. In a meta-analysis of 8 studies (5800 patients) of airway management in patients who had thyroid surgery, tracheal deviation was the only thyroid-specific factor associated with difficult intubation [42]. Other identified risk factors were a high Mallampati score, a short thyromental distance, a low interincisor gap, obesity, and male gender. In practice, the presence of a large benign goiter without symptoms of obstruction seldom changes airway management plans.

Surgical evaluation prior to thyroidectomy usually includes laryngoscopy to evaluate vocal cord function, as well as thyroid ultrasound (see "Thyroidectomy", section on 'Preoperative evaluation and preparation'). If respiratory symptoms are present or substernal goiter is suspected, computed tomography or magnetic resonance imaging is often obtained to assess the size of a goiter, its caudal extent, the extent of tracheal compression, and the location of the mass (eg, anterior or posterior mediastinum) [40,43]. Other studies may have been ordered to evaluate the full extent of the mass and its effects upon surrounding structures. (See "Clinical presentation and evaluation of goiter in adults", section on 'Goiter with obstructive symptoms or suspected substernal goiter'.)

All available studies should be reviewed by the anesthesiologist, with particular attention to the following clinical entities:

●Cancerous goiter – The presence of a cancerous goiter may be a risk factor for difficult intubation, possibly due to tissue infiltration with associated fibrosis, which may reduce the mobility of laryngeal structures and impede the view of the glottic opening during laryngoscopy [38]. The limited literature on this issue is conflicting. In one prospective review of 320 patients who underwent thyroidectomy, presence of a cancerous goiter was an independent risk factor for difficult intubation [38]. In contrast, in another prospective study of 324 thyroidectomy patients, thyroid malignancy was not associated with difficult intubation [41]. Neither study provided details on the severity of thyroid malignancy or related imaging.

●Obstructive or substernal goiter – Extension of the thyroid below the sternal notch (ie, substernal goiter) results in respiratory symptoms in 90 percent of patients and dysphagia in one-third [40]. Respiratory symptoms, including hoarseness, dyspnea, wheezing, obstructive sleep apnea, or cough, may be caused by tracheal compression or nerve involvement. (See "Clinical presentation and evaluation of goiter in adults", section on 'Obstructive symptoms'.)

Substernal mediastinal goiters can cause obstruction of airway and major cardiovascular structures with induction of anesthesia. (See 'Induction of anesthesia' below and "Anesthesia for patients with an anterior mediastinal mass", section on 'Anesthetic preparation and management'.)

ANESTHETIC MANAGEMENT FOR THYROID AND/OR PARATHYROID SURGERY — Anesthetic management is generally similar for thyroid and parathyroid surgery, except as noted in the following discussion.

Choice of anesthetic technique — Thyroid and parathyroid surgery (open or minimally invasive) can be performed with general anesthesia or with local/regional anesthesia, which usually includes a cervical plexus block. Excision of a single parathyroid gland can often be performed with local infiltration alone, without a nerve block. The choice of anesthetic technique should be based on patient factors and patient, surgeon, and anesthesiologist preference.

We prefer general anesthesia for thyroid or parathyroid surgery, unless local or regional anesthesia is requested by the patient and/or the surgeon. However, practice varies, and in some high volume endocrine surgery centers, local or regional anesthesia is used more commonly than general anesthesia [44,45]. General anesthesia provides a secure airway from the start of anesthesia and an immobile surgical field. Regional anesthesia allows intraoperative voice monitoring, avoidance of endotracheal intubation, and may have other benefits for patients with some comorbidities, such as avoidance of hemodynamic changes in patients with cardiac disease. (See 'Recurrent laryngeal nerve monitoring' below.)

Several studies that compared general with regional anesthesia for thyroid surgery have reported reduced length of stay and costs with regional anesthesia, and similar clinical outcomes [44,46,47].

Surgical contraindications to a local/regional anesthetic technique include a plan for sternotomy or lateral neck dissection. Patient factors that are contraindications for local/regional anesthesia include cervical lymphadenopathy, locally invasive cancer, local anesthetic allergy, and patient refusal. [45,48]. General anesthesia is usually preferred for prolonged surgical procedures, for patients who cannot communicate, cooperate, or lie still or with their neck extended for the length of the surgery, for patients with severe anxiety, and for patients who are claustrophobic. General anesthesia with secure airway control may also be preferred for patients with predicted difficulty with airway management, or expected airway difficulty during sedation (eg, patients with obstructive sleep apnea or morbid obesity). In large case series, 2 to 12 percent of patients undergoing thyroidectomy with local or regional anesthesia require conversion to general anesthesia because of anxiety, inadequate anesthesia, surgical difficulty, or airway problems [45,47-49].

Local/regional anesthesia can be used for minimally invasive thyroid surgery, unless alternative incision sites are used (eg, axillary or retroauricular). (See "Thyroidectomy", section on 'Minimally invasive thyroid surgery'.)

Local or regional anesthesia — Regional anesthesia for thyroid or parathyroid surgery usually involves the use of a cervical plexus block along with local infiltration by the surgeon, as well as monitored anesthesia care and sedation. Superficial cervical plexus block is the regional anesthetic technique of choice for thyroid and parathyroid surgery. Deep cervical plexus block is more difficult to perform, less effective, and associated with more anesthesia-related complications than superficial block. (See "Scalp block and cervical plexus block techniques", section on 'Cervical plexus blocks'.)

We do not typically perform superficial cervical plexus blocks solely for postoperative analgesia after routine thyroid surgery. Pain is usually modest after uncomplicated thyroidectomy and is typically well controlled with local anesthetic wound infiltration and multimodal nonopioid analgesics, with addition of opioids if necessary.

Some institutions have implemented enhanced recovery after surgery (ERAS) protocols that include superficial cervical plexus blocks. However, the available literature has not shown clear benefits of superficial cervical plexus block in this setting, and studies have not typically compared these blocks with multimodal analgesic regimens. A 2018 meta-analysis of 14 randomized trials (1150 patients) that compared superficial cervical plexus blocks with saline or no block for thyroid surgery found small improvements in pain scores with blocks, with a mean difference 0.5 to 0.7 on a 0 to 10 visual analog scale (VAS) over the course of 24 hours [50]. There was longer time until first request for analgesia with the use of superficial cervical plexus block (mean 143 versus 38 minutes), and reduced hospital length of stay (two trials, mean 2.1 versus 2.4 days). Several subsequently published studies have reported statistically significant but likely clinically irrelevant reductions in postoperative pain scores and analgesic consumption in patients who had superficial cervical plexus blocks [51-53].

Intraoperative anesthetic management

Monitoring — Standard physiologic monitoring (ie, electrocardiography, noninvasive blood pressure monitoring, pulse oximetry, and capnography) is sufficient for most patients who undergo thyroid or parathyroid surgery (table 6). Advanced monitoring (eg, intra-arterial continuous blood pressure monitoring) may be indicated based on patient comorbidities. Special monitoring that may be used during these procedures include the following:

Recurrent laryngeal nerve monitoring — If recurrent laryngeal nerve monitoring is to be used during the procedure, either a specialized endotracheal tube (ETT) may be used, or a conventional ETT with electrodes applied above the ETT cuff. The electrodes must be placed at the level of the vocal cords during intubation. Neuromuscular blockade should then be avoided during maintenance of anesthesia. Intraoperative nerve monitoring is discussed separately. (See "Thyroidectomy", section on 'Intraoperative nerve monitoring'.)

Parathyroid hormone monitoring — Intraoperative parathyroid hormone monitoring may be performed during parathyroidectomy for hyperparathyroidism, to indicate when hyperfunctioning parathyroid tissue has been excised. One or more blood samples can be drawn from a peripheral vein, an arterial catheter, or by the surgeon from the internal jugular vein. The decision to place an arterial catheter or a second intravenous (IV) catheter should be individualized; we usually draw the necessary sample from a vein in the foot or lower leg for these samples, since the patient's arms are tucked at the side and inaccessible. Another common approach is to place an IV catheter in an antecubital vein just below a blood pressure cuff (and use the cuff as a tourniquet prior to withdrawing a blood sample). Some surgeons simply prefer to draw a sample from the internal jugular vein in the operative field. (See "Parathyroid exploration for primary hyperparathyroidism", section on 'Intraoperative parathyroid hormone monitoring'.)

Induction of anesthesia — The choice of induction technique and medications depends on patient factors, and is discussed separately. (See "Induction of general anesthesia: Overview".)

If nerve monitoring is to be used during the procedure, neuromuscular blockade must be avoided during testing. Thus a short-acting neuromuscular blocking agent (NMBA), or no NMBA, should be used for endotracheal intubation. Options include succinylcholine, rocuronium or vecuronium reversed with sugammadex prior to testing, or a remifentanil intubation (eg, remifentanil 2.5 to 4 mcg/kg IV with propofol 2 mg/kg IV and ephedrine 10 to 15 mg IV, modified for patient factors). (See "Rapid sequence induction and intubation (RSII) for anesthesia", section on 'Alternatives to succinylcholine'.)

Substernal goiters are present in 2 to 19 percent of patients having thyroidectomy [54], and are located in the anterior mediastinum in 75 to 90 percent of cases [55]. Induction of anesthesia in patients with a very large or obstructing mediastinal mass may result in obstruction of major airways or major cardiovascular structures. Management of anesthesia for patients with mediastinal masses is discussed separately. (See "Anesthesia for patients with an anterior mediastinal mass".)

Airway management — We routinely perform endotracheal intubation for thyroid or parathyroid surgery, though supraglottic airways (SGAs) can be used for these procedures as well [56-58].

ETTs provide a secure airway throughout the procedure, and are mandatory if recurrent laryngeal nerve monitoring is used. SGAs are more likely to require adjustment after neck extension for surgical positioning or during tracheal manipulation during surgery, but may result in less coughing during emergence from anesthesia.

The airway may be managed with standard intubation techniques in most patients with thyroid disease. However, for patients with a goiter that is symptomatic, invasive, or substernal, the approach to induction and intubation may need to be altered. (See 'Airway evaluation' above and "Management of the difficult airway for general anesthesia in adults".)

Patients with stridor due to severe tracheal compression should be intubated awake to limit the risk of complete airway obstruction when spontaneous ventilation ceases. The surgical team should be prepared and ready to perform an emergent tracheotomy (which may be difficult in a patient with a goiter) or rigid bronchoscopy for patients with airway compromise [40] (see "Management of the difficult airway for general anesthesia in adults", section on 'Awake intubation').

Individual case reports have described the use of venovenous extracorporeal membrane oxygenation (ECMO) prior to induction of anesthesia [59] or for airway rescue [60] in patients with large thyroid masses.

Positioning for surgery — The patient is typically positioned on the operating table in a supine position with the head elevated, with the arms tucked at the sides. The neck is typically extended, with either a roll or an inflatable bag (ie, a "thyroid bag") under the patient's shoulders. The patient's ability to extend the neck should be assessed preoperatively, and patients with known cervical spine disease should be assessed by an orthopedic surgeon or neurosurgeon for the safety of neck extension. (See "Thyroidectomy", section on 'Patient position and skin preparation'.)

●After positioning, the patient's occiput should be resting on a head support (eg, foam donut or blanket), rather than floating or suspended.

●The airway device may require adjustment after positioning with neck extension. Neck extension may move the electrodes for nerve monitoring of the ETT out of correct position relative to the vocal cords and can unseat an SGA.

Maintenance of anesthesia — The choice of anesthetic agents for maintenance of anesthesia depends on patient factors, and is discussed separately. (See "Maintenance of general anesthesia: Overview".)

The effects of abnormal thyroid function on the choice of anesthetic agents and intraoperative management are discussed above. (See 'Multiorgan system effects of thyroid disease' above.)

Concerns specific to thyroid or parathyroid surgery include the following:

●When recurrent laryngeal nerve monitoring is used, NMBAs should be avoided during maintenance of anesthesia.

●Manipulation of the trachea during surgery is stimulating, and can cause cough or patient movement. Remifentanil infusion (eg, 0.03 to 0.3 mcg/kg per minute, modified for patient factors and other anesthetic agents) can be used to suppress these responses without unnecessary postoperative opioid effect. Low dose remifentanil infusion can also be administered during emergence and extubation to minimize cough. (See 'Emergence and extubation' below.)

●We use standard oxygen supplementation for patients who undergo thyroid or parathyroid surgery, with fraction of inspired oxygen typically approximately 30 percent, modified for patient factors (see "Mechanical ventilation during anesthesia in adults", section on 'Fraction of inspired oxygen'). Whereas one study suggested a beneficial effect of a high fraction of inspired oxygen (80 percent during and after surgery) on certain complication rates, these data are preliminary and require confirmation [61].

Prophylaxis for postoperative nausea and vomiting — We employ preventive measures for postoperative nausea and vomiting for all patients who undergo thyroid surgery to minimize the risk of wound hematoma due to retching or vomiting. We administer at least one prophylactic antiemetic during surgery (eg, ondansetron 4 mg IV), and use an opioid-sparing strategy for postoperative pain relief (eg, local anesthetic wound infiltration, postoperative acetaminophen and nonsteroidal antiinflammatory drugs). In high-risk patients, we also use total IV anesthesia. (See "Postoperative nausea and vomiting".)

Emergence and extubation — Severe hypertension or coughing during emergence and extubation may induce bleeding from the surgical site, with possible hematoma formation. Strategies to minimize coughing include, but are not limited to, extubation under deep anesthesia (which carries the risks of an unprotected airway in an anesthetized patient) or administration of remifentanil, dexmedetomidine, or lidocaine during emergence [62-65]. The choice of technique and drugs is determined by patient risk factors for coughing (eg, smoking status), as well as the preferences and the experience of the anesthesiologist. (See "Extubation following anesthesia", section on 'Minimizing physiologic response to extubation'.)

Postextubation airway complications — Immediately after extubation, airway compromise may develop due to recurrent laryngeal nerve injury, causing vocal cord dysfunction; tracheomalacia, causing tracheal collapse in patients with long-standing tracheal compression (extremely rare); or expansion of a cervical wound hematoma, causing new tracheal compression. Immediate reintubation may be necessary. (See "Thyroidectomy", section on 'Hematoma' and "Thyroidectomy", section on 'Nerve injury/vocal cord paresis or paralysis'.)

Recurrent laryngeal nerve injury — All patients who undergo thyroid or parathyroid surgery should be watched closely immediately after extubation for signs of recurrent laryngeal nerve (RLN) dysfunction, including stridor, weak vocalization, or airway obstruction, particularly after bilateral surgery. RLN injury may be suspected by the surgeon or suggested by nerve monitoring, but may be apparent only after extubation without intraoperative evidence of injury.

The RLN innervates most of the intrinsic laryngeal muscles. Injury to the nerve can be partial and result in weak vocal cord motion, or complete and result in paralysis of the affected vocal cord. The involved vocal cord assumes a median or paramedian position. Unilateral RLN injury causes hoarseness but no airway obstruction, whereas bilateral RLN paralysis can result in stridor, and possibly complete airway obstruction. Immediate reintubation, and occasionally tracheostomy, may be necessary. (See "Thyroidectomy", section on 'Nerve injury/vocal cord paresis or paralysis'.)

Injury to the superior laryngeal nerve (in contrast with the RLN) has no effect on postoperative airway status. Rather, it manifests as voice fatigue and changes in voice quality [66].

Neck hematoma — Postoperative neck hematoma requiring emergency surgical evacuation is a rare but potentially serious complication of thyroidectomy. Bleeding and hematoma formation may cause venous congestion of airway structures, and airway compromise may develop rapidly due to compression of the trachea or laryngeal edema as soft tissue swelling develops and as the hematoma expands. When surgical bleeding causes airway compromise, emergency re-operation may be required to evacuate the hematoma. Head-up position to lower venous pressures, nebulized epinephrine, and systemic steroids may be useful temporizing strategies; however, definitive treatment should not be delayed [67,68]. (See "Thyroidectomy", section on 'Hematoma'.)

If time permits, the patient should be returned to the operating room for re-exploration; however, rapidly developing airway compromise may require bedside evacuation of the hematoma as an immediate airway protection maneuver. Soft tissue swelling may be so severe that reopening the incision fails to fully normalize the airway anatomy. Since substantial distortion of the airway may persist after the hematoma has been evacuated, the safest method for intubation may be an awake intubation. No matter what approach is taken, intubation should not be delayed; it should be performed expeditiously by the most experienced member of the team (table 7).

Tracheomalacia — Longstanding tracheal compression by a goiter may lead to tracheomalacia [55]. Although extremely rare, prolonged compression may cause atrophy and erosion of cartilaginous tracheal rings. After thyroid resection, the tracheal wall may collapse in an anteroposterior direction, leading to airway obstruction. Incidence and management of tracheomalacia due to goiter are discussed separately. (See "Treatment of benign obstructive or substernal goiter", section on 'Tracheomalacia'.)

In patients with longstanding large goiters, we perform a cuff leak test to assess the adequacy of air flow around the endotracheal tube prior to extubation (see "Extubation following anesthesia", section on 'Cuff-leak test'). If there is no leak, we extubate over a tube exchanger to facilitate rapid reintubation if necessary.

Postoperative care — Most patients are transferred to the post-anesthesia care unit for recovery from anesthesia, with monitoring and discharge criteria similar to patients who have other types of surgery. These issues are discussed separately. (See "Overview of post-anesthetic care for adult patients".)

After thyroid surgery, patients may be admitted to the hospital for overnight observation and management, or in select cases, may be discharged home within a few hours of surgery. Inpatient versus outpatient surgery is discussed separately. (See "Thyroidectomy", section on 'Inpatient versus outpatient surgery'.)

SUMMARY AND RECOMMENDATIONS

●Preanesthesia evaluation

•Thyroid dysfunction causes physiologic changes that may affect anesthetic care and perioperative outcomes. Most of these changes resolve with treatment as the patient becomes euthyroid. (See 'Multiorgan system effects of thyroid disease' above.)

•For patients with known, treated thyroid disease, euthyroid status should be confirmed during preanesthesia evaluation. Patients taking a stable dose of thyroid medication, with documented euthyroid status within the past three to six months, do not need additional testing prior to surgery. (See 'Euthyroid patients' above.)

•For patients with recently diagnosed thyroid disease, elective surgery should be delayed until treatment results in a documented euthyroid state. Patients with severe hypothyroidism or hyperthyroidism who need urgent or emergency surgery should receive immediate treatment prior to surgery. (See 'Patients with abnormal thyroid function' above.)

●Choice of anesthetic technique – We prefer general anesthesia for thyroid or parathyroid surgery. Advantages of general anesthesia include secured control of the airway and an immobile surgical field, as well as avoidance of the need for urgent conversion from local/regional to general anesthesia. However, clinical outcomes do not differ in patients who receive local or regional versus general anesthesia. (See 'Choice of anesthetic technique' above.)

●Airway concerns

•An enlarged thyroid gland (goiter) can cause difficulty with airway management for anesthesia, particularly cancerous, substernal, or obstructing goiters. (See 'Airway evaluation' above.)

•A smaller than usual endotracheal tube (ETT) size may be required in patients with potential airway problems related to a goiter. Patients with stridor due to tracheal compression are intubated awake, with the surgical team standing by ready to perform emergent tracheotomy or rigid bronchoscopy. (See 'Induction of anesthesia' above.)

•After thyroid surgery, post-extubation airway compromise may develop, caused by vocal cord dysfunction due to recurrent laryngeal nerve injury, tracheal compression due to an expanding wound hematoma, or tracheomalacia due to long-standing tracheal compression. Immediate reintubation may be necessary, as well as emergency surgical decompression of any wound hematoma. (See 'Postextubation airway complications' above.)

●Recurrent laryngeal nerve monitoring – If recurrent laryngeal nerve monitoring is used during thyroid or parathyroid surgery, neuromuscular blockade should be avoided during testing. (See 'Recurrent laryngeal nerve monitoring' above.)

ACKNOWLEDGMENT — The editorial staff at UpToDate acknowledge William R Furman, MD, who contributed to an earlier version of this topic review.