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.