Hypothyroidism/Hyperthyroidism Flashcards
What is the other name for hypothyroidism?
Myxedema
Hines RL, Marschall KE. Anesthesia & Co-Existing Diseases.
6th ed. Philadelphia, PA: Elsevier-Saunders; 2012: 389.
What is primary hypothyroidism?
Primary hypothyroidism is a decrease in the amount of thyroid
hormone produced despite adequate levels of TSH.
Hines RL, Marschall KE. Anesthesia & Co-Existing Diseases.
6th ed. Philadelphia, PA: Elsevier-Saunders; 2012: 389.
What is the incidence of hypothyroidism?
It occurs in about 0.5%-0.8% of the general adult population.
20% of women over the age of 60 have subclinical
hypothyroidism.
Hines RL, Marschall KE. Anesthesia & Co-Existing Diseases.
6th ed. Philadelphia, PA: Elsevier-Saunders; 2012: 389
Is the onset of hypothyroidism in adults usually acute
or insidious?
Hypothyroidism in adults usually has a slow, insidious
progression.
Hines RL, Marschall KE. Anesthesia & Co-Existing Diseases.
6th ed. Philadelphia, PA: Elsevier-Saunders; 2012: 389
Patients with hypothyroidism often have nonpitting
edema. What is the cause of this?
Hydrophilic mucopolysaccharides accumulate in the dermis,
resulting in thickened skin with immobile, nonpitting edema.
Hines RL, Marschall KE. Anesthesia & Co-Existing Diseases.
6th ed. Philadelphia, PA: Elsevier-Saunders; 2012: 389.
What are the respiratory changes that occur with
hypothyroidism?
The maximum breathing capacity, diffusion capacity, and
ventilatory response to hypoxia and hypercarbia are all
decreased.
Hines RL, Marschall KE. Anesthesia & Co-Existing Diseases.
6th ed. Philadelphia, PA: Elsevier-Saunders; 2012: 389.
What electrolyte abnormality is associated with
hypothyroidism?
Hyponatremia and impaired free water excretion are common
findings in hypothyroidism.
Hines RL, Marschall KE. Anesthesia & Co-Existing Diseases.
6th ed. Philadelphia, PA: Elsevier-Saunders; 2012: 389
How is peripheral vascular resistance affected by
hypothyroidism?
Peripheral vascular resistance is increased and blood volume is
reduced.
Hines RL, Marschall KE. Anesthesia & Co-Existing Diseases.
6th ed. Philadelphia, PA: Elsevier-Saunders; 2012: 389.
How does hypothyroidism affect cardiac status?
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.
Hines RL, Marschall KE. Anesthesia & Co-Existing Diseases.
6th ed. Philadelphia, PA: Elsevier-Saunders; 2012: 389.
How does hypothyroidism affect mental status?
It produces mental sluggishness. Patients develop slow
speech, apathy, and listlessness.
Hines RL, Marschall KE. Anesthesia & Co-Existing Diseases.
6th ed. Philadelphia, PA: Elsevier-Saunders; 2012: 389.
What is Hashimoto’s thyroiditis and what population
does it affect?
Hashimoto’s thyroiditis is an autoimmune disease of the thyroid
gland that results in enlargement of the gland. It affects middleaged
females.
Hines RL, Marschall KE. Anesthesia & Co-Existing Diseases.
6th ed. Philadelphia, PA: Elsevier-Saunders; 2012: 389.
What is the most common cause of primary
hypothyroidism?
Ablation of the thyroid gland with radioactive iodine or surgical
removal of the gland.
Hines RL, Marschall KE. Anesthesia & Co-Existing Diseases.
6th ed. Philadelphia, PA: Elsevier-Saunders; 2012: 389.
What is the typical TSH level in a patient with
hypothyroidism?
5-15 mU/L
Fleisher LA. Anesthesia and Uncommon Diseases. 6th ed.
Philadelphia, PA: Elsevier Saunders; 2012: 413
What is the normal thyroid stimulating hormone
(TSH) level?
The normal range is 0.4-5.0 mU/L
Fleisher LA. Anesthesia and Uncommon Diseases. 6th ed.
Philadelphia, PA: Elsevier Saunders; 2012: 410.
What are the ECG changes often seen with
hypothyroidism?
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.
Hines RL, Marschall KE. Anesthesia & Co-Existing Diseases.
6th ed. Philadelphia, PA: Elsevier-Saunders; 2012: 389.
What is myxedema coma?
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.
Hines RL, Marschall KE. Anesthesia & Co-Existing Diseases.
6th ed. Philadelphia, PA: Elsevier-Saunders; 2012: 391.
How is hypothyroidism diagnosed?
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.
Hines RL, Marschall KE. Anesthesia & Co-Existing Diseases.
6th ed. Philadelphia, PA: Elsevier-Saunders; 2012: 390.
What is the most common treatment for
hypothyroidism?
Levothyroxine sodium which restores T3 and T4 levels to
normal.
Hines RL, Marschall KE. Anesthesia & Co-Existing Diseases.
6th ed. Philadelphia, PA: Elsevier-Saunders; 2012: 390.
Is the cardiomyopathy seen with hypothyroidism
reversible?
Yes. Patients who take levothyroxine will exhibit improvement
in myocardial function within 2-4 months.
Hines RL, Marschall KE. Anesthesia & Co-Existing Diseases.
6th ed. Philadelphia, PA: Elsevier-Saunders; 2012: 389-390
How do patients with hypothyroidism respond to
anesthetic drugs?
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.
Hines RL, Marschall KE. Anesthesia & Co-Existing Diseases.
6th ed. Philadelphia, PA: Elsevier-Saunders; 2012: 390
What are the potential airway considerations for a
patient with hypothyroidism?
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.
Hines RL, Marschall KE. Anesthesia & Co-Existing Diseases.
6th ed. Philadelphia, PA: Elsevier-Saunders; 2012: 390.
How does hypothyroidism affect temperature
maintenance under anesthesia?
Patients with hypothyroidism are prone to hypothermia which
occurs quickly and is difficult to correct once it does occur.
Hines RL, Marschall KE. Anesthesia & Co-Existing Diseases.
6th ed. Philadelphia, PA: Elsevier-Saunders; 2012: 390.
What are the hematologic effects of hypothyroidism?
Patients with hypothyroidism exhibit an increased bleeding
tendency.
Longnecker DE, Newman MF, Brown DL, Zapol WM.
Anesthesiology. 2nd ed. New York: McGraw-Hill; 2012: 152.
What is the best approach for treating hypotension
following induction of a patient with hypothyroidism?
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.
Hines RL, Marschall KE. Anesthesia & Co-Existing Diseases.
6th ed. Philadelphia, PA: Elsevier-Saunders; 2012: 390.
In what population of patients does myxedema most
commonly occur?
Myxedema coma most commonly occurs in elderly females with
a longstanding history of hypothyroidism.
Hines RL, Marschall KE. Anesthesia & Co-Existing Diseases.
6th ed. Philadelphia, PA: Elsevier-Saunders; 2012: 391.
What is the cardinal feature of myxedema coma?
Despite the name, unconsciousness is relatively uncommon in
myxedema coma. The cardinal symptom is hypothermia, which
may be as low as 80 degrees Fahrenheit.
Hines RL, Marschall KE. Anesthesia & Co-Existing Diseases.
6th ed. Philadelphia, PA: Elsevier-Saunders; 2012: 391.
What is the only indication for intravenous
levothyroxine?
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.
Hines RL, Marschall KE. Anesthesia & Co-Existing Diseases.
6th ed. Philadelphia, PA: Elsevier-Saunders; 2012: 391.
What is a goiter?
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.
Hines RL, Marschall KE. Anesthesia & Co-Existing Diseases.
6th ed. Philadelphia, PA: Elsevier-Saunders; 2012: 391.
Is regional anesthesia contraindicated in patients
with hypothyroidism?
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.
Hines RL, Marschall KE. Anesthesia & Co-Existing Diseases.
6th ed. Philadelphia, PA: Elsevier-Saunders; 2012: 390.
Is succinylcholine contraindicated in patients with
hypothyroidism?
No. Patients with hypothyroidism are at increased risk for
aspiration and succinylcholine is often indicated at induction.
Hines RL, Marschall KE. Anesthesia & Co-Existing Diseases.
6th ed. Philadelphia, PA: Elsevier-Saunders; 2012: 390
What is hyperthyroidism?
Hyperthyroidism is defined as the hyperdynamic function of the
thyroid gland, resulting in the excessive secretion of thyroid
hormones.
Hines RL, Marschall KE. Anesthesia & Co-Existing Diseases.
6th ed. Philadelphia, PA: Elsevier-Saunders; 2012: 387.
What are the general signs and symptoms of
hyperthyroidism?
The symptoms of hyperthyroidism include anxiety, emotional
lability, heat intolerance, insomnia, fatigue, tremors, and weight
loss.
Hines RL, Marschall KE. Anesthesia & Co-Existing Diseases.
6th ed. Philadelphia, PA: Elsevier-Saunders; 2012: 387.
What is the leading cause of hyperthyroidism?
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.
Hines RL, Marschall KE. Anesthesia & Co-Existing Diseases.
6th ed. Philadelphia, PA: Elsevier-Saunders; 2012: 387.
How is hyperthyroidism diagnosed?
The hyperdynamic clinical presentation often provides clues,
but is confirmed by elevated T3, free T4, Free T4 index, and RT3U,
an increased radioactive iodine uptake, and a low TSH
level.
Stoelting RK, Dierdorf SF. Anesthesia & Co-Existing Diseases.
5th ed. New York, NY: Churchill-Livingston; 2008: 382.
How does hyperthyroidism affect the hematocrit?
The platelet count?
Hyperthyroidism produces anemia and thrombocytopenia.
Barash PG, Cullen BF, Stoelting RK, Cahalan MK, Stock MC,
Ortega R. Clinical Anesthesia. 7th ed. Philadelphia, PA:
Lippincott Williams and Wilkins; 2013: 1329.
What are the cardiac effects of hyperthyroidism?
The effects of hyperthyroidism on the heart include tachycardia,
atrial dysrhythmias, increased myocardial contractility, and
cardiomegaly.
Hines RL, Marschall KE. Anesthesia & Co-Existing Diseases.
6th ed. Philadelphia, PA: Elsevier-Saunders; 2012: 387.
What is toxic multinodular goiter?
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.
Hines RL, Marschall KE. Anesthesia & Co-Existing Diseases.
6th ed. Philadelphia, PA: Elsevier-Saunders; 2012: 387-388.
What is the first line of treatment for hyperthyroidism?
The first treatment is the administration of propylthiouracil or
methimazole. Both of these drugs disrupt the synthesis of
thyroid hormone.
Hines RL, Marschall KE. Anesthesia & Co-Existing Diseases.
6th ed. Philadelphia, PA: Elsevier-Saunders; 2012: 388.
How does subtotal thyroidectomy compare to
radioactive iodine in efficacy in the treatment of
hyperthyroidism?
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%.
Hines RL, Marschall KE. Anesthesia & Co-Existing Diseases.
6th ed. Philadelphia, PA: Elsevier-Saunders; 2012: 388.
What is the role of beta-blockers in the treatment of
hyperthyroidism?
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.
Hines RL, Marschall KE. Anesthesia & Co-Existing Diseases.
6th ed. Philadelphia, PA: Elsevier-Saunders; 2012: 388.
What population is most affected by hyperthyroidism?
Hyperthyroidism most commonly occurs in female patients
between the ages of 20 and 40.
Barash PG, Cullen BF, Stoelting RK, Cahalan MK, Stock MC,
Ortega R. Clinical Anesthesia. 7th ed. Philadelphia, PA:
Lippincott Williams and Wilkins; 2013: 1328.
What are the three most common causes of
hyperthyroidism?
Graves’ disease, toxic multinodular goiter, and toxic adenoma.
Hines RL, Marschall KE. Anesthesia & Co-Existing Diseases.
6th ed. Philadelphia, PA: Elsevier-Saunders; 2012: 387.
What is the most important goal in the anesthetic
management of the thyrotoxic patient?
The most important goal is to render the patient euthyroid prior
to surgery.
Barash PG, Cullen BF, Stoelting RK, Cahalan MK, Stock MC,
Ortega R. Clinical Anesthesia. 7th ed. Philadelphia, PA:
Lippincott Williams and Wilkins; 2013: 1329.
What drug regimen is typically used in thyrotoxic
patients prior to surgery to gain control over their
symptoms?
A combination of propranolol and potassium iodide are often
used prior to surgery to reduce symptoms of circulating levels of
T3 and T4.
Barash PG, Cullen BF, Stoelting RK, Cahalan MK, Stock MC,
Ortega R. Clinical Anesthesia. 7th ed. Philadelphia, PA:
Lippincott Williams and Wilkins; 2013: 1329.
How long prior to surgery does it normally take to
render a patient euthyroid?
Thyrotoxic patients usually require medical management for 7-
14 days prior to surgery to create a euthyroid state.
Barash PG, Cullen BF, Stoelting RK, Cahalan MK, Stock MC,
Ortega R. Clinical Anesthesia. 7th ed. Philadelphia, PA:
Lippincott Williams and Wilkins; 2013: 1329.
What is thyroid storm?
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.
Barash PG, Cullen BF, Stoelting RK, Cahalan MK, Stock MC,
Ortega R. Clinical Anesthesia. 7th ed. Philadelphia, PA:
Lippincott Williams and Wilkins; 2013: 1329.
What are the symptoms of thyroid storm?
Tachycardia, hyperthermia, dysrhythmias, myocardial ischemia,
congestive heart failure, and altered mental status. It can
closely resemble light anesthesia, pheochromocytoma, and
even malignant hyperthermia.
Barash PG, Cullen BF, Stoelting RK, Cahalan MK, Stock MC,
Ortega R. Clinical Anesthesia. 7th ed. Philadelphia, PA:
Lippincott Williams and Wilkins; 2013: 1329-1330.
At what point during the perioperative period is a
patient with hyperthyroidism most likely to
experience thyrotoxicosis?
Patients can experience thyrotoxic crisis at any point during an
anesthetic, but it is most likely to occur within 6 to 18 hours
postoperatively.
Butterworth JF, Mackey DC, Wasnick JD. Morgan & Mikhail’s
Clinical Anesthesiology. 5th ed. New York, NY: McGraw-Hill;
2013: 734.
