Thyroid Surgery Indications and Preparation
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Questions and Answers

What is the primary goal of perioperative care for a patient undergoing thyroidectomy?

  • To induce thyroid storm
  • To minimize the risk of hypothyroidism
  • To prevent stimulation of the sympathetic nervous system (correct)
  • To promote hemodynamic instability

    • Which of the following is NOT an indication for thyroidectomy?

  • Idiopathic hypertrophy without increased thyroid hormone synthesis and release
  • Cancer suspected or present
  • Hypothyroidism with a small goiter (correct)
  • Hyperthyroidism

    • What is the primary reason for rendering patients euthyroid before surgery?

  • To prevent thyroid storm (correct)
  • To minimize the effect of sympathetic nervous system responses
  • To reduce the risk of hypothyroidism
  • To improve hemodynamic stability

    • What is the systemic manifestation of hyperthyroidism?

    <p>Exaggerated sympathetic nervous system responses</p> Signup and view all the answers

    What is the primary focus of hemodynamic management during thyroidectomy?

    <p>Maintaining hemodynamic stability</p> Signup and view all the answers

    What is the anatomical structure that connects the two lobes of the thyroid gland?

    <p>Isthmus</p> Signup and view all the answers

    Which nerves are at risk of damage during resection of the thyroid gland?

    <p>Recurrent laryngeal nerve and external superior laryngeal nerve</p> Signup and view all the answers

    What is the primary source of arterial blood supply to the thyroid gland?

    <p>Superior and inferior thyroid arteries</p> Signup and view all the answers

    What is the ratio of T3 to T4 produced by the thyroid gland?

    <p>1:10</p> Signup and view all the answers

    What is the effect of T3 and T4 on the hypothalamus and anterior pituitary gland when their concentrations are sufficient?

    <p>Inhibitory effect</p> Signup and view all the answers

    What is the potency of T3 compared to T4?

    <p>Four times more potent</p> Signup and view all the answers

    Which structure is responsible for secreting thyrotropin-releasing hormone (TRH)?

    <p>Hypothalamus</p> Signup and view all the answers

    What is the primary controller of thyroid hormone biosynthesis?

    <p>Thyroid-stimulating hormone (TSH)</p> Signup and view all the answers

    What is the primary mechanism by which antithyroid medications achieve euthyroidism in patients with hyperthyroidism?

    <p>Inhibition of thyroid hormone synthesis</p> Signup and view all the answers

    What is the cardiac manifestation associated with hypothyroidism?

    <p>Decreased cardiac output</p> Signup and view all the answers

    What is the primary reason for considering patients with severe hypothyroidism to be at high risk for perioperative complications?

    <p>Increased risk of myxedema coma</p> Signup and view all the answers

    What is the most common dysrhythmia associated with hyperthyroidism?

    <p>Atrial fibrillation</p> Signup and view all the answers

    What is the primary effect of hyperthyroidism on the body?

    <p>Increased metabolic rate</p> Signup and view all the answers

    What is the primary cause of muscle weakness in patients with hyperthyroidism?

    <p>Thyroid hormone-mediated muscle breakdown</p> Signup and view all the answers

    What is the role of beta-adrenergic antagonists in the management of hyperthyroidism?

    <p>Maintaining hemodynamic stability</p> Signup and view all the answers

    What is the primary difference between hyperthyroidism and hypothyroidism?

    <p>Metabolic rate</p> Signup and view all the answers

    What is the primary purpose of achieving hemostasis during thyroidectomy?

    <p>To minimize bleeding and reduce transfusion risks</p> Signup and view all the answers

    What determines the extent of thyroid tissue removal during thyroidectomy?

    <p>The severity of thyroid disease and intraoperative findings</p> Signup and view all the answers

    What is the primary method of closing the muscle and fascia layers during thyroidectomy?

    <p>Suturing with dissolvable material</p> Signup and view all the answers

    What is the purpose of approximating the wound edges during thyroidectomy?

    <p>To facilitate suturing or stapling</p> Signup and view all the answers

    What is the surgical approach used to access the thyroid gland during thyroidectomy?

    <p>Transverse neck incision</p> Signup and view all the answers

    What is the significance of evaluating signs and symptoms such as tachycardia, fever, dysrhythmias, or agitation preoperatively in a patient presenting for thyroidectomy?

    <p>To identify potential anesthesia-related complications</p> Signup and view all the answers

    What is the mechanism of action of thioamide medications in achieving a euthyroid state?

    <p>By inhibiting the formation of thyroid hormone</p> Signup and view all the answers

    What is the effect of iodides on the thyroid gland in patients with hyperplasia?

    <p>They inhibit the organification process and reduce the size and vascularity of the thyroid gland</p> Signup and view all the answers

    What is the significance of assessing the patient's voice quality preoperatively in a patient presenting for thyroidectomy?

    <p>To identify potential RLN palsy caused by compression from the enlarged thyroid gland</p> Signup and view all the answers

    Why is it important to evaluate the patient's ability to breathe in the supine position preoperatively in a patient presenting for thyroidectomy?

    <p>To determine if the patient has tracheal compression or occlusion caused by the enlarged thyroid gland</p> Signup and view all the answers

    What is the potency of methimazole compared to propylthiouracil?

    <p>Methimazole is 10 times more potent than propylthiouracil</p> Signup and view all the answers

    What is the primary reason for evaluating the patient's airway anatomy preoperatively in a patient presenting for thyroidectomy?

    <p>To assess the patient's airway anatomy and potential difficulties in intubation</p> Signup and view all the answers

    Why is it important to achieve a euthyroid state preoperatively in patients undergoing thyroidectomy?

    <p>To reduce the risk of anesthesia-related complications</p> Signup and view all the answers

    What is the primary mechanism by which the Wolff-Chaikoff effect inhibits thyroid activity?

    <p>By inhibiting the autoregulatory process of thyroid hormone biosynthesis</p> Signup and view all the answers

    What is the primary route of administration of radioactive iodine (I'31) for treating hyperthyroidism?

    <p>Orally</p> Signup and view all the answers

    What is the primary effect of beta-adrenergic blockade on the manifestations of hyperthyroidism?

    <p>Decreases the cardiac manifestations of hyperthyroidism</p> Signup and view all the answers

    What is the primary mechanism by which corticosteroids achieve a euthyroid state in patients with hyperthyroidism?

    <p>By reducing the production of TSH</p> Signup and view all the answers

    What is the primary outcome of administering radioactive iodine (I'31) for treating hyperthyroidism?

    <p>Patients achieve a euthyroid state within several weeks</p> Signup and view all the answers

    What is the mortality rate of untreated thyroid storm?

    <p>10%-75%</p> Signup and view all the answers

    What is the condition often mistaken for thyroid storm?

    <p>Malignant hyperthermia</p> Signup and view all the answers

    What is the primary goal of pharmacologic treatment in thyroid storm?

    <p>Decrease circulating thyroid hormone</p> Signup and view all the answers

    Why is methimazole preferred over propylthiouracil in thyroid storm?

    <p>It acts more rapidly</p> Signup and view all the answers

    What is the antipyretic of choice in thyroid storm?

    <p>Acetaminophen</p> Signup and view all the answers

    Why is beta-adrenergic antagonism used in thyroid storm?

    <p>To control cardiovascular effects</p> Signup and view all the answers

    What is the purpose of administering sodium iodide in thyroid storm?

    <p>To block release of hormone from the thyroid gland</p> Signup and view all the answers

    What is an additional treatment option to decrease circulating thyroid hormone?

    <p>All of the above</p> Signup and view all the answers

    What is the primary reason for maintaining hemodynamic stability during thyroidectomy?

    <p>To prevent an exaggerated sympathetic nervous system response</p> Signup and view all the answers

    What is the effect of hyperthyroidism on minimum alveolar concentration (MAC) requirements?

    <p>MAC requirements are increased in the presence of hyperthermia</p> Signup and view all the answers

    What is the indication for using a direct-acting vasopressor such as phenylephrine?

    <p>Hypotension that is unresponsive to fluid resuscitation</p> Signup and view all the answers

    What is the primary reason for not using ketamine as an induction agent in a patient undergoing thyroidectomy?

    <p>It can cause sympathetic nervous system stimulation</p> Signup and view all the answers

    What is the primary benefit of using a flexible intubating endoscope during intubation in a patient with a large thyroid goiter?

    <p>It allows for better visualization of the larynx</p> Signup and view all the answers

    What is the primary function of the NIM endotracheal tube during thyroidectomy?

    <p>To determine the real-time integrity of the recurrent laryngeal nerves (RLNs)</p> Signup and view all the answers

    What is the primary sign of thyroid storm?

    <p>Hyperthermia</p> Signup and view all the answers

    What is the primary concern regarding airway management in a patient with a large thyroid goiter?

    <p>Difficulty in locating the cricothyroid membrane</p> Signup and view all the answers

    What is the primary reason for avoiding the use of desflurane in patients with hyperthyroidism?

    <p>It can cause sympathetic nervous system activation</p> Signup and view all the answers

    What is the primary reason for taping the eyes carefully during thyroidectomy, especially in patients with exophthalmos?

    <p>To prevent corneal abrasions</p> Signup and view all the answers

    What is the primary benefit of using video laryngoscopy during intubation in a patient with a thyroid mass?

    <p>It allows for better visualization of the larynx</p> Signup and view all the answers

    What is the primary benefit of using sevoflurane in patients with hyperthyroidism?

    <p>It has low blood gas solubility and cardiovascular stability</p> Signup and view all the answers

    What is the primary reason for elevating the head of the bed to 30 degrees during thyroidectomy?

    <p>To improve surgical exposure</p> Signup and view all the answers

    What is the primary complication associated with the use of a NIM endotracheal tube?

    <p>Kinking and rupturing</p> Signup and view all the answers

    What is the primary concern regarding the use of a bougie stylet during video laryngoscopy in a patient with a thyroid mass?

    <p>It may cause difficulty in passing the endotracheal tube</p> Signup and view all the answers

    What is the primary reason for monitoring temperature continuously during thyroidectomy?

    <p>To prevent hyperthermia</p> Signup and view all the answers

    What is the primary benefit of using narcotics and dexmedetomidine in patients with hyperthyroidism?

    <p>They can attenuate the sympathetic nervous system response and provide postoperative analgesia</p> Signup and view all the answers

    What is the primary reason for locating the cricothyroid membrane before airway manipulation in a patient with a large thyroid goiter?

    <p>To prevent cricothyroidotomy</p> Signup and view all the answers

    What is the primary consequence of bilateral RLN damage?

    <p>Aphonia, stridor, or respiratory distress</p> Signup and view all the answers

    What is the incidence of temporary vocal cord paralysis after thyroidectomy?

    <p>2.6% to 5.9%</p> Signup and view all the answers

    What is the purpose of surgically identifying the location of the RLN intraoperatively?

    <p>To prevent RLN damage and subsequent vocal cord paralysis</p> Signup and view all the answers

    What is the common cause of hematoma formation after thyroidectomy?

    <p>All of the above</p> Signup and view all the answers

    What is the definitive treatment for hematoma formation after thyroidectomy?

    <p>Immediate evacuation of the hematoma and reexploration of the surgical site</p> Signup and view all the answers

    What is the rare complication associated with thyroidectomy due to the proximity of the apices of the lungs to the surgical site?

    <p>Pneumothorax</p> Signup and view all the answers

    What is the potential consequence of inadequate surgical hemostasis after thyroidectomy?

    <p>Hematoma formation</p> Signup and view all the answers

    How is vocal cord function assessed after thyroidectomy?

    <p>Via direct laryngoscopy after deep extubation</p> Signup and view all the answers

    Study Notes

    Thyroidectomy Indications

    • Hyperthyroidism (increased thyroid function)
    • Cancer or suspected cancer
    • Hypothyroidism (decreased thyroid function) with a goiter that causes respiratory difficulty
    • Idiopathic hypertrophy (enlargement of the thyroid gland) without increased thyroid hormone synthesis and release

    Preoperative Care

    • Patients should be rendered euthyroid before surgery
    • Focus on avoiding stimulation of the sympathetic nervous system
    • Prevent systemic effects of hyperthyroidism (exaggerated sympathetic nervous system responses)

    Perioperative Care

    • Maintain hemodynamic stability
    • Provide adequate fluid resuscitation
    • Administer antithyroid medications preoperatively
    • Avoid excessive sympathetic stimulation

    Postoperative Complications

    • Thyroid storm: a potentially fatal complication that can occur during intraoperative and postoperative periods

    Anatomy of the Thyroid Gland

    • The thyroid gland consists of two lobes connected by an isthmus.
    • The isthmus is located just below the cricoid cartilage, binding the thyroid gland to the anterior and lateral aspects of the trachea.
    • Two pairs of parathyroid glands are located on the posterior aspect of each lobe, regulating plasma calcium levels.

    Location and Relationships

    • The thyroid gland is positioned near the carotid sheath and the esophagus.
    • The recurrent laryngeal nerve (RLN) and the external superior laryngeal nerve (SLN) are branches of the vagus nerve, innervating the intrinsic muscles of the larynx.
    • The RLN and SLN are in proximity to the thyroid gland and can be damaged during resection.

    Blood Supply and Venous Drainage

    • Arterial blood is supplied by the superior and inferior thyroid arteries.
    • A venous plexus is formed by the superior, middle, and inferior thyroid veins.
    • The thyroid gland is adjacent to the common carotid artery and the anterior jugular vein, potential sources of rapid and massive blood loss.

    Thyroid Hormone Regulation

    • The hypothalamus secretes thyrotropin-releasing hormone (TRH), stimulating the anterior pituitary gland to create TSH.
    • TSH controls the biosynthesis of thyroid hormone.
    • The thyroid gland produces and secretes thyroid hormones T3 and T4 in a ratio of 1:10, respectively.

    Thyroid Hormone Function

    • T3 and T4 have an inhibitory effect on the hypothalamus and anterior pituitary gland, creating a negative-feedback loop.
    • T3 is approximately four times more potent than T4.
    • Thyroid hormones regulate the metabolic rate of numerous physiologic processes, including tissue growth, oxygen consumption, and energy utilization.

    Additional Functions

    • The thyroid gland produces calcitonin from parafollicular C cells, helping regulate serum calcium levels.
    • Thyroid hormones regulate the metabolic rate, influencing the symptomatology associated with thyroid dysfunction.

    Hyperthyroidism

    • Hyperthyroidism is a pathologic state characterized by excessive secretion of T3 and T4, leading to hypermetabolism.
    • Most cases are caused by Graves' disease, toxic multinodular goiter, or toxic adenoma.
    • Signs and symptoms include:
      • Weight loss
      • Exophthalmos
      • Heat intolerance
      • Tachycardia
      • Muscle weakness
      • Hyperglycemia
      • Increased deep tendon reflexes
      • Fatigue
    • Cardiac manifestations:
      • Tachycardia
      • Dysrhythmias (atrial fibrillation is most common)
      • Increased cardiac output due to adrenergic hyperactivity
    • Surgical intervention:
      • Ideally, surgery should be postponed until patient is euthyroid after taking antithyroid medications
      • If not possible, beta-adrenergic antagonists are used to maintain hemodynamic stability

    Hypothyroidism

    • Hypothyroidism occurs when T3 and T4 levels are low, often caused by autoimmune diseases (e.g., Hashimoto thyroiditis), radioactive iodine, antithyroid medications, or iodine deficiency.
    • Clinical presentation reflects a decrease in metabolic rate.
    • Decreased cardiac output is caused by a decrease in both heart rate and stroke volume.
    • Mild hypothyroidism is not a contraindication to surgery.
    • Severe hypothyroidism (myxedema coma) may increase risk for perioperative complications associated with physiologic stress of surgery and anesthesia.

    Surgical Procedure for Thyroid Gland Removal

    • The surgical procedure involves a transverse neck incision through the platysma and strap muscles to expose the thyroid gland and its blood supply.
    • Hemostasis is achieved before resection can begin.
    • The type of thyroidectomy performed depends on the pathologic condition, and can be either subtotal or lobectomy (removal of one lobe of the thyroid gland).
    • The amount of thyroid gland tissue removed depends on the severity of thyroid disease and intraoperative findings.
    • The muscle and fascia layers are closed using dissolvable material.
    • The wound edges are approximated and then sutured or stapled.

    Preoperative Period for Thyroidectomy

    • Elective cases should be postponed until antithyroid medications allow the patient to achieve a euthyroid state.
    • Key findings to evaluate preoperatively include signs and symptoms of hyperthyroidism such as tachycardia, fever, dysrhythmias, or agitation.
    • Airway assessment and management may be complicated in patients with an enlarged thyroid gland, which can displace the larynx and distort normal airway anatomy.
    • A potentially difficult intubation may occur due to the enlarged thyroid gland, and the anesthetist should be aware of this possibility.
    • The quality of the patient's voice and any changes should be noted, as hoarseness may indicate RLN palsy caused by compression from the enlarged thyroid gland.
    • Patients who experience difficulty breathing in the supine position may have tracheal compression and occlusion due to pressure from the thyroid gland.

    Medications for Achieving a Euthyroid State

    • Thioamides (propylthiouracil and methimazole) decrease the formation of thyroid hormone by inhibiting thyroid peroxidase and the organification process.
    • Methimazole is 10 times more potent than propylthiouracil.
    • Iodides (sodium iodide or potassium iodide) inhibit the organification process, production and release of thyroid hormone, and size and vascularity of the thyroid gland if hyperplasia exists.
    • The Wolff-Chaikoff effect is an autoregulatory process that inhibits thyroid activity for several days to weeks if excessive quantities of iodide are present.
    • Radioactive iodine (isotope I'31) is administered orally, collects within the follicle, and emits radiation that destroys the thyroid cells, allowing patients to achieve a euthyroid state within several weeks.
    • Beta-adrenergic blockade (beta-blocking medications) inhibits the peripheral conversion of T4 to T3 and decreases cardiac manifestations consistent with enhanced sympathetic nervous system activity.
    • Corticosteroids (steroids) have an inhibitory effect on TSH and can be used in conjunction with other medications to achieve a euthyroid state.

    Anesthetic Induction for Thyroidectomy

    • Propofol and etomidate are acceptable medications for anesthetic induction in patients undergoing thyroidectomy.
    • Ketamine is not recommended due to its potential to stimulate the sympathetic nervous system.

    Airway Management

    • Consider awake intubation using a flexible intubating endoscope (fiber-optic scope) if the thyroid mass or goiter causes significant displacement of normal laryngeal anatomy.
    • Standard induction and intubation using video laryngoscopy (VL) is adequate if there is minimal to no laryngeal displacement.
    • A bougie stylet may help with endotracheal tube delivery during VL.

    Patient Positioning

    • Patients are placed supine with the head elevated 30 degrees and the neck extended.
    • The eyes should be carefully taped, especially for patients with exophthalmos, to avoid corneal abrasions.
    • There is a possibility of endotracheal tube migration during neck extension and flexion.
    • The surgeon may request a shoulder roll and extension of the patient's head to achieve the ideal position for maximal surgical exposure.
    • Supporting the occiput is important to avoid postoperative neck discomfort or brachial plexus injury.

    Maintenance of Anesthetic Depth

    • Maintenance of anesthesia should focus on attenuating sympathetic nervous system stimulation.
    • Sevoflurane is an acceptable inhalational anesthetic due to its low blood gas solubility and cardiovascular stability.
    • Narcotics and dexmedetomidine can help attenuate the sympathetic nervous system response and provide postoperative analgesia.

    Hemodynamic Stability

    • Hemodynamic stability should be closely monitored and managed to maintain stability and prevent thyrotoxic crisis.
    • The ECG may reveal atrial fibrillation, a common tachydysrhythmia seen with hyperthyroidism.
    • The onset of tachycardia unresponsive to fluid replacement may indicate the need for additional beta-adrenergic receptor blockade.
    • Hypotension unresponsive to fluid resuscitation is best treated with a direct-acting vasopressor such as phenylephrine.

    Nerve Integrity Monitoring (NIM)

    • The NIM endotracheal tube uses electromyographic (EMG) information to determine the real-time integrity of the right and left RLNs.
    • The electrodes on the proximal end of the tube are inserted into a monitor that interprets the signals and allows the surgeon to determine if RLN function remains intact throughout surgery.
    • Neuromuscular blockade and laryngeal tracheal lidocaine should be avoided if the NIM endotracheal tube is used.

    Thyroid Storm

    • Early detection and prevention of thyrotoxic crisis are essential.
    • Signs and symptoms of thyroid storm include hyperthermia, tachycardia, and tachydysrhythmia, central nervous system symptoms, and rhabdomyolysis.
    • Treatment of thyroid storm involves pharmacologic treatment to decrease circulating thyroid hormone, as well as providing supportive interventions.
    • Treatment options include:
      • Increasing the fraction of inspired oxygen concentration
      • Fluid resuscitation with cooled intravenous fluids
      • Propylthiouracil or methimazole to inhibit thyroid hormone synthesis
      • Sodium iodide to block release of hormone from the thyroid gland
      • Acetaminophen as the antipyretic of choice
      • Beta-adrenergic antagonists to control cardiovascular effects
      • Steroid administration such as dexamethasone or hydrocortisone
      • Serial electrolyte and arterial blood gas analysis

    Postoperative Complications of Thyroidectomy

    • Recurrent Laryngeal Nerve (RLN) damage can be unilateral or bilateral, causing hoarseness, aphonia, stridor, or respiratory distress.
    • Incidence of permanent vocal cord paralysis is rare (0.5% to 2.4%), while temporary paralysis occurs in 2.6% to 5.9% of cases.
    • Identification of RLN intraoperatively can prevent RLN damage, but may be difficult in cases of extreme hypertrophy or cancer.
    • Vocal cord function can be assessed via direct laryngoscopy after deep extubation or by having the patient phonate "e" postoperatively.

    Hematoma Formation

    • Hematoma formation can cause compression or collapse of the airway secondary to tracheomalacia, with an incidence of approximately 1%.
    • Inadequate surgical hemostasis, coagulopathy, acute hypertension, and straining from postoperative nausea and vomiting can increase the potential for postoperative bleeding.

    Treatment of Hematoma Formation

    • Definitive treatment involves immediate evacuation of the hematoma and reexploration of the surgical site.

    Pneumothorax

    • Pneumothorax is a rare complication of thyroidectomy, occurring when air enters the thoracic cavity due to the proximity of the surgical site to the apices of the lungs.

    Acute Hypocalcemia

    • Acute hypocalcemia can occur due to inadvertent removal of the parathyroid glands, with an incidence of 10% to 50%.
    • Serum calcium and parathyroid hormone levels can be checked intraoperatively or immediately postoperatively to predict the potential for hypoparathyroidism.
    • Hypocalcemia typically occurs 24 to 48 hours after surgery and can be treated with oral calcium and vitamin D.
    • Parathyroid dysfunction is usually transient, but can be permanent if all four parathyroid glands are removed.

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    Description

    Learn about the reasons for thyroidectomy, including hyperthyroidism, cancer, and goiter, and how to prepare patients for surgery. Understand the systemic effects of hyperthyroidism and its symptoms.

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