Hypothyroidism/Hyperthyroidism

Question 1

How is peripheral vascular resistance affected by hypothyroidism?

Answer 1

Peripheral vascular resistance is increased and blood volume is reduced.

Question 2

What are the respiratory changes that occur with hypothyroidism?

Answer 2

The maximum breathing capacity, diffusion capacity, and ventilatory response to hypoxia and hypercarbia are all decreased.

Question 3

What are the ECG changes often seen with hypothyroidism?

Answer 3

The ECG may exhibit flattened or inverted T waves, low-voltage P waves and QRS complexes, and sinus bradycardia. They are also more prone to the development of ventricular dysrhythmias.

Question 4

Patients with hypothyroidism often have nonpitting edema. What is the cause of this?

Answer 4

Hydrophilic mucopolysaccharides accumulate in the dermis, resulting in thickened skin with immobile, nonpitting edema.

Question 5

How does hypothyroidism affect cardiac status?

Answer 5

There is a decrease in cardiac output due to reductions in both heart rate and stroke volume. Pericardial effusions are common. In advanced hypothyroidism, myocardial contractility is impaired due to both diastolic and systolic dysfunction and cardiomegaly may result.

Question 6

How does hypothyroidism affect mental status?

Answer 6

It produces mental sluggishness. Patients develop slow speech, apathy, and listlessness.

Question 7

What is the other name for hypothyroidism?

Answer 7

Myxedema

Question 8

What is the most common cause of primary hypothyroidism?

Answer 8

Ablation of the thyroid gland with radioactive iodine or surgical removal of the gland.

Question 9

What is the typical TSH level in a patient with hypothyroidism?

Answer 9

5-15 mU/L

Question 10

What is the normal thyroid stimulating hormone (TSH) level?

Answer 10

The normal range is 0.4-5.0 mU/L

Question 11

What is Hashimoto’s thyroiditis and what population does it affect?

Answer 11

Hashimoto’s thyroiditis is an autoimmune disease of the thyroid gland that results in enlargement of the gland. It affects middle- aged females.

Question 12

What electrolyte abnormality is associated with hypothyroidism?

Answer 12

Hyponatremia and impaired free water excretion are common findings in hypothyroidism.

Question 13

What is the best approach for treating hypotension following induction of a patient with hypothyroidism?

Answer 13

In patients with hypothyroidism, the administration of alpha agonists such as phenylephrine could substantially increase the systemic vascular resistance against a heart that has limited capacity to compensate by increasing its contractility. Epinephrine 50 mcg would increase both the SVR and contractility, but a 50 mcg dose may be enough to result in hypertension and arrhythmias. Atropine would serve to increase the heart rate but would not address the issue of blood pressure. The best option for these patients is to administer small (2.5 - 5mg) doses of ephedrine while monitoring filling pressures and the ECG closely.

Question 14

Is regional anesthesia contraindicated in patients with hypothyroidism?

Answer 14

Regional anesthesia is not contraindicated if there are no coagulation disorders present. In fact, if coagulation is not an issue, regional anesthesia is preferred over general anesthesia for these patients when the surgery permits.

Question 15

How does hypothyroidism affect temperature maintenance under anesthesia?

Answer 15

Patients with hypothyroidism are prone to hypothermia which occurs quickly and is difficult to correct once it does occur.

Question 16

What are the potential airway considerations for a patient with hypothyroidism?

Answer 16

They are more prone to airway compromise due to edema of the airway and vocal cords. The presence of a goiter may alter the airway anatomy, making intubation more difficult. They also exhibit a prolonged gastric transit time which makes them more susceptible to regurgitation and aspiration of gastric contents during laryngoscopy.

Question 17

How do patients with hypothyroidism respond to anesthetic drugs?

Answer 17

There are no studies on the anesthetic requirements of patients with hypothyroidism, but most anecdotal evidence in the literature points to an increased sensitivity to anesthesia drugs. This effects are presumed to be due to decreases in cardiac output, blood volume, hepatic metabolism, and renal excretion.

Question 18

Is the cardiomyopathy seen with hypothyroidism reversible?

Answer 18

Yes. Patients who take levothyroxine will exhibit improvement in myocardial function within 2-4 months.

Question 19

How is hypothyroidism diagnosed?

Answer 19

It is diagnosed by the presence of decreased levels of free T4, total T4, T3, R-T3U, free T4 index, and an elevated TSH level.

Question 20

What is myxedema coma?

Answer 20

Myxedema coma is an uncommon and severe form of hypothyroidism in which the patient exhibits altered mentation, unconsciousness, hypothermia, hypoventilation, bradycardia, hypotension, and dilutional hyponatremia.

Question 21

Is succinylcholine contraindicated in patients with hypothyroidism?

Answer 21

No. Patients with hypothyroidism are at increased risk for aspiration and succinylcholine is often indicated at induction.

Question 22

What is primary hypothyroidism?

Answer 22

Primary hypothyroidism is a decrease in the amount of thyroid hormone produced despite adequate levels of TSH.

Question 23

What is the most common treatment for hypothyroidism?

Answer 23

Levothyroxine sodium which restores T3 and T4 levels to normal.

Question 24

What is the cardinal feature of myxedema coma?

Answer 24

Despite the name, unconsciousness is relatively uncommon in myxedema coma. The cardinal symptom is hypothermia, which may be as low as 80 degrees Fahrenheit.

Question 25

What is the only indication for intravenous levothyroxine?

Answer 25

Myxedema coma is the only true indication for intravenous administration of levothyroxine. It is administered as a 300-500 mcg loading dose followed by 50-200 mcg/day.

Question 26

What is a goiter?

Answer 26

A goiter is the hypertrophy of the follicular epithelium of the thyroid gland that occurs in response to a reduction in thyroid gland function. The hypertrophy results in enlargement of the thyroid gland itself.

Question 27

What are the hematologic effects of hypothyroidism?

Answer 27

Patients with hypothyroidism exhibit an increased bleeding tendency.

Question 28

In what population of patients does myxedema most commonly occur?

Answer 28

Myxedema coma most commonly occurs in elderly females with a longstanding history of hypothyroidism.

Question 29

What is the incidence of hypothyroidism?

Answer 29

It occurs in about 0.5%-0.8% of the general adult population. 20% of women over the age of 60 have subclinical hypothyroidism.

Question 30

What is thyroid storm?

Answer 30

Thyroid storm is a life-threatening exacerbation of hyperthyroidism. It most commonly appears in patients who have undiagnosed or untreated hyperthyroidism and respond adversely to the stress of surgery or other stressful event.

Question 31

Is the onset of hypothyroidism in adults usually acute or insidious?

Answer 31

Hypothyroidism in adults usually has a slow, insidious progression.

Question 32

At what point during the perioperative period is a patient with hyperthyroidism most likely to experience thyrotoxicosis?

Answer 32

Patients can experience thyrotoxic crisis at any point during an anesthetic, but it is most likely to occur within 6 to 18 hours postoperatively.

Question 33

Is ketamine an appropriate induction drug for patients with hyperthyroidism?

Answer 33

No. Drugs that stimulate the sympathetic nervous system such as ketamine, pancuronium, ephedrine, etc., should be avoided whenever possible in patients with hyperthyroidism.

Question 34

What are the symptoms of thyroid storm?

Answer 34

Tachycardia, hyperthermia, dysrhythmias, myocardial ischemia, congestive heart failure, and altered mental status. It can closely resemble light anesthesia, pheochromocytoma, and even malignant hyperthermia.

Question 35

What drug regimen is typically used in thyrotoxic patients prior to surgery to gain control over their symptoms?

Answer 35

A combination of propranolol and potassium iodide are often used prior to surgery to reduce symptoms of circulating levels of T3 and T4.

Question 36

What is the most important goal in the anesthetic management of the thyrotoxic patient?

Answer 36

The most important goal is to render the patient euthyroid prior to surgery.

Question 37

How long prior to surgery does it normally take to render a patient euthyroid?

Answer 37

Thyrotoxic patients usually require medical management for 7- 14 days prior to surgery to create a euthyroid state.

Question 38

What population is most affected by hyperthyroidism?

Answer 38

Hyperthyroidism most commonly occurs in female patients between the ages of 20 and 40.

Question 39

What are the three most common causes of hyperthyroidism?

Answer 39

Graves’ disease, toxic multinodular goiter, and toxic adenoma.

Question 40

A patient exhibits symptoms of thyroid storm postoperatively. What interventions should you take?

Answer 40

Dehydration should be treated with administered glucose- containing intravenous fluids. Cooling measures should be instituted. Beta-blockers should be titrated to reduce the heart rate less than 90 beats per minute. Steroids and antithyroid medications can be administered to reduce circulating levels of thyroid hormones.

Question 41

What is hyperthyroidism?

Answer 41

Hyperthyroidism is defined as the hyperdynamic function of the thyroid gland, resulting in the excessive secretion of thyroid hormones.

Question 42

What are the general signs and symptoms of hyperthyroidism?

Answer 42

The symptoms of hyperthyroidism include anxiety, emotional lability, heat intolerance, insomnia, fatigue, tremors, exopthalmos, and weight loss.

Question 43

What is the leading cause of hyperthyroidism?

Answer 43

Graves’ disease, which appears to be an autoimmune syndrome in which thyroid-stimulating antibodies attach to TSH receptors and stimulate the hyperplasia of thyroid tissue.

Question 44

How is hyperthyroidism diagnosed?

Answer 44

The hyperdynamic clinical presentation often provides clues, but is confirmed by elevated T3, free T4, Free T4 index, and R- T3U, an increased radioactive iodine uptake, and a low TSH level.

Question 45

How does hyperthyroidism affect the hematocrit? The platelet count?

Answer 45

Hyperthyroidism produces anemia and thrombocytopenia.

Question 46

What are the cardiac effects of hyperthyroidism?

Answer 46

The effects of hyperthyroidism on the heart include tachycardia, atrial dysrhythmias, increased myocardial contractility, and cardiomegaly.

Question 47

What is toxic multinodular goiter?

Answer 47

This is an extreme form of thyroid enlargement that results from simple goiter in which the thyroid enlargement is severe enough to produce dysphagia and inspiratory stridor.

Question 48

What is the first line of treatment for hyperthyroidism?

Answer 48

The first treatment is the administration of propylthiouracil or methimazole. Both of these drugs disrupt the synthesis of thyroid hormone.

Question 49

How does subtotal thyroidectomy compare to radioactive iodine in efficacy in the treatment of hyperthyroidism?

Answer 49

Subtotal thyroidectomy promptly cures thyrotoxicosis in 95% of patients with less risk for hypothyroidism than the use of radioactive iodine. The mortality rate for thyroidectomy is less than 0.1%.

Question 50

What is the role of beta-blockers in the treatment of hyperthyroidism?

Answer 50

Beta-blockers relieve many of the symptoms of hyperthyroidism such as anxiety, sweating, heat intolerance, tremors, and tachycardia, but do not address the underlying thyroid disorder.