Exam 2: Endocrine

Question 1

the thyroid gland is innervated by the __________ and ___________ nervous systems

Answer 1

adrenergic and cholinergic

Question 2

TSH secretion is influenced by T3 and T4 levels via a ____________ feedback loop

Answer 2

negative

Question 3

half-life of T4 in circulation is:

Answer 3

6-7 days

Question 4

half-life of T3 in circulation is:

Answer 4

24-30 hours

Question 5

which thyroid hormone is the active, free form?

Answer 5

T3
unbound, more potent, and short half-life

T4 is converted to T3 in the target cell

Question 6

where is the concentration of T4 the highest?

Answer 6

the blood

Question 7

which is directly released from the thyroid gland: T3 or T4?

Answer 7

T4

T3 = mostly extrathyroid conversion of T4 to T3

Question 8

which undergoes more protein binding between T4 and T3?

Answer 8

T4

T3 = unbound, more potent, and short half-life

Question 9

how do hyper- and hypothyroidism affect MAC?

Answer 9

no effect on MAC requirements

elevated thyroid hormones increase O2 consumption in all tissues except CNS

therefore, MAC requirements remain the same

Question 10

how do elevated thyroid hormones affect induction?

Answer 10

slower induction

increased cardiac output increases the anesthetic uptake into the blood and decreases the rate of rise of FA/FI, creating a slower induction

Question 11

what are the effects of thyroid hormone on cardiac myocytes?

Answer 11

increases myocardial contractility directly
increases HR
increases systolic contractile function
increases diastolic relaxation

Question 12

what are the effects of thyroid hormone on vascular smooth muscle?

Answer 12

decreases systemic vascular resistance via direct vasodilation
increases intravascular fluid volume

Question 13

what are the general findings in hypothyroidism?

Answer 13

goiter
weight loss
muscle weakness (inc protein catabolism)
moist and warm skin
heat intolerance
fine hair
diarrhea (intestinal hypermotility)
tremor (increased sensitivity of neuronal synapses in spinal cord)
exophthalmos (increased retrobulbar fat)
hypercalcemia (inc bone turnover)

Question 14

what is the first line of treatment for hyperthyroidism?

Answer 14

antithyroid drug:
methimazole, propylthiouracil, iodide

Question 15

propylthiouracil (PTU)

Answer 15

prevents production of more T4 and T3 in the thyroid
blocks conversion of T4 to T3 outside the thyroid

Question 16

methimazole (tapazole)

Answer 16

prevents production of more thyroid hormone

Question 17

dexamethasone and hydrocortisone for hyperthyroidism

Answer 17

blocks conversion of T4 to T3

Question 18

beta blockers in hyperthyroid: propranolol and esmolol

Answer 18

reduces symptoms (tachycardia, tremor, restlessness) caused by a heightened response to catecholamines; blocks conversion of T4 to T3

Question 19

what can thyroid storm mimic under anesthesia?

Answer 19

malignant hyperthermia
pheochromocytoma
neuroleptic malignant syndrome
light anesthesia

Question 20

The most important preoperative goal for the patient with hyperthyroidism is to make the patient:

Answer 20

euthyroid

normal thyroid function tests, HR <85 bpm, and no hand tremor

Question 21

hyperthyroid patients undergoing emergency surgery should be given what 3 drugs:

Answer 21

b-blocker (usually (propranolol), thionamide (propylthiouracil), and a stress dose of glucocorticoid

Question 22

what is the range of serum calcium?

Answer 22

8.5 to 10.5 mg/dL

Question 23

in what three forms does calcium exist?

Answer 23

ionized (50%)
bound to serum proteins i.e. albumin (41%)
bound to diffusible anions i.e. citrate, bicarbonate, phosphate (9%)

Question 24

what two forms of calcium are diffusible across capillary membranes?

Answer 24

bound to anions and ionized

Question 25

normal level of ionized calcium in the blood

Answer 25

4.7 to 5.2 mg/dL

Question 26

the form of calcium that exerts physiologic effects and therefore measurement provides the most clinically relevant information

Answer 26

ionized calcium

Question 27

what is the function of PTH?

Answer 27

regulate calcium

Question 28

what is PTH secretion determined by?

Answer 28

the fraction of ionized calcium in the blood

Question 29

what two things increase PTH synthesis and release?

Answer 29

low ionized calcium and vitamin D

Question 30

maintenance of steady-state calcium balance is provided by:

Answer 30

GI absorption

Question 31

what are the three sources of Calcium resorption/absorption?

Answer 31

***bone: increases resorption (bones release = increased blood Ca)*** kidney: increases renal tubular absorption (decreases Ca levels) GI tract: increases absorption of vitamin D (increases Ca levels)

Question 32

what controls calcium homeostasis?

Answer 32

PTH calcium feedback loop

Question 33

again, what determines parameters of calcium hemostasis? (4)

Answer 33

PTH gland GI intestines Kidney Bone

Question 34

what is the significance of calcium on blood coagulation?

Answer 34

calcium is a clotting factor and affects platelet aggregation. low calcium levels can contribute to surgical bleeding

Question 35

besides platelet aggregation, what other physiologic functions does calcium have a role in?

Answer 35

muscle contraction (skeletal and cardiac) bone formation cell division

Question 36

how does alkalosis affect ionized calcium levels?

Answer 36

decreases serum calcium by increasing calcium protein-binding (bound = inactive)

Question 37

how does acidosis affect ionized calcium levels?

Answer 37

increases serum calcium by decreasing calcium protein binding (unbound = active)

Question 38

most common cause of hypercalcemia is:

Answer 38

excess PTH

Question 39

continuous exposure to elevated PTH (i.e. parathyroid adenoma or hyperplasia) can result in:

Answer 39

osteoclast-mediated bone resorption and hypercalcemia

Question 40

hypercalcemia is defined as total serum calcium above:

Answer 40

10.4 mg/dL (normal range 8.5 to 10.5 mg/dL)

Question 41

what is the most common cause of hyperparathyroidism?

Answer 41

solitary benign adenoma (80%)

Question 42

how often is hyperplasia and hyperfunctioning of all four parathyroid glands in hyperparathyroism?

Answer 42

15%

Question 43

what hereditary endocrine abnormalities can be associated with parathyroid adenoma and hyperparathyroidism?

Answer 43

MEN I and MEN IIA

Question 44

What other endocrine conditions are MEN I and MEN IIA associated with?

Answer 44

Medullary (solid) thyroid carcinomas and pheochromocytoma 50% of patients with MEN IIA develop pheochromocytomas and up to 30% develop hyperparathyroidism

Question 45

what are skeletal symptoms of hypercalcemia and hyperparathyroidism?

Answer 45

skeletal demineralization collapse of vertebral bodies pathologic fractures***

Question 46

what are gastrointestinal symptoms of hypercalcemia and hyperparathyroidism?

Answer 46

pancreatitis peptic ulcers abdominal pain vomiting

Question 47

what are renal symptoms of hypercalcemia and hyperparathyroidism?

Answer 47

nephrolithiasis (kidney stones) polyuria, polydipsia decreased GFR diabetes insipidus

Question 48

what are cardiac symptoms of hypercalcemia and hyperparathyroidism?

Answer 48

bradycardia/arrhythmia prolonged PR interval shortened QT interval systemic HTN

Question 49

What ECG change is seen in the hyperparathyroid patient? Why?

Answer 49

ECG may reveal a shortened QT interval. The hyperparathyroid patient may be hypercalcemic, and hypercalcemia shortens the QT interval.

Question 50

with severe and protracted hyperparathyroidism bones can become ____

Answer 50

painful and susceptible to fracture

Question 51

what are hematopoietic symptoms of hypercalcemia and hyperparathyroidism?

Answer 51

anemia

Question 52

what are nervous system symptoms of hypercalcemia and hyperparathyroidism?

Answer 52

somnolence decreased pain sensation psychosis

Question 53

what are ocular symptoms of hypercalcemia and hyperparathyroidism?

Answer 53

calcifications (keratopathy) and conjunctivitis

Question 54

management of mild hypercalcemia (12 mg/dL):

Answer 54

hydration

Question 55

management of moderate to severe hypercalcemia (13-15 mg/dL):

Answer 55

aggressive hydration (IV NS) and furosemide (or ethacrynic acid) to promote Na/Ca diuresis

Question 56

what is given to treat hypophosphatemia?

Answer 56

phosphate there is no compensatory mechanism for phosphate

Question 57

what anesthetic technique would be appropriate for a limited resection of a hypersecreting parathyroid gland?

Answer 57

GETA

Question 58

what anesthetic technique would be appropriate for a small adenoma excision?

Answer 58

cervical plexus block and MAC

Question 59

what preoperative treatment would be appropriate for mild hypercalemia (<12 mg/dL)?

Answer 59

NS 150 mL/hr (NO LR)

Question 60

what is the importance of hydration for the patient with hyperparathyroidism?

Answer 60

Hypercalcemic patient may be dehydrated Restoring fluid balance with non- calcium containing solutions aims to 1) dilute the serum calcium, 2) maintain adequate GFR, 3) calcium clearance and 4) maintain intravascular volume

Question 61

what anesthetic considerations should be taken with vigorous hydration of the patient with hyperparathyroidism?

Answer 61

bladder catheterization CVP monitoring frequent serum electrolyte checks

Question 62

what anesthetic considerations must be taken for the mental status of the patient with hyperparathyroidism?

Answer 62

hypercalcemia can cause somnolence and confusion in the hyperparathyroid patient avoid preoperative sedatives which can increase this MAC requirements may be decreased in patients with preoperative somnolence

Question 63

what is the half-life of PTH? how is this useful in surgery?

Answer 63

5 minutes marker to help determine when a hyperfunctioning gland has been removed (rapid PTH assay) - periodically measure ionized calcium levels to guide surgical resection

Question 64

what is imperative to monitor for after removal of parathyroid adenoma?

Answer 64

hypocalcemia

Question 65

what can cause transient postoperative hypocalcemia after surgical removal of parathyroid adenoma?

Answer 65

rapid bone uptake of calcium (AKA "hungry bone syndrome")

Question 66

_____ occurs when calcium falls below _____ mg/dL

Answer 66

Tetany; < 6 mg/dL

Question 67

what is a life-threatening sign of hypocalcemia? (*hint = respiratory)

Answer 67

stridor; sign of respiratory distress laryngeal muscles are susceptible to tetanic spasm from hypocalcemia

Question 68

what cardiac dysrhythmias are associated with hypocalcemia?

Answer 68

prolonged QT interval (torsades)

Question 69

Treatment of tetany in the hypoparathyroid patient consists of administering what?

Answer 69

Calcium gluconate IV. Hypocalcemia can cause tetany.

Question 70

what is the most common cause of acquired PTH deficiency and Hypoparathyroidism?

Answer 70

unintentional removal of the parathyroid glands during thyroid or parathyroid surgery

Question 71

what lab results indicate hypocalcemia and hypoparathyroidism?

Answer 71

total calcium <8.5mg/dL; ionized calcium < 4.5 mg/dL

Question 72

what will phosphate levels be in hypoparathyroidism?

Answer 72

elevated d/t decreased renal excretion of phosphate

Question 73

what is the recommended treatment of chronic hypoparathyroidism? (*hint = supplementation x3)

Answer 73

activated vitamin D calcium magnesium

Question 74

hypocalcemia produces _____ of nerve and muscle cells

Answer 74

hyperexcitability

Question 75

Laryngeal muscles are very sensitive to decreased calcium and hypocalcemia. what can this result in with hypoparathyroidism?

Answer 75

laryngospasm

Question 76

deep tendon reflexes in hypocalcemia are ____

Answer 76

hyperactive

Question 77

chvostek sign

Answer 77

abnormal reaction to the stimulation of the facial nerve, muscle twitching

Question 78

trousseau's sign

Answer 78

elicited by the inflation of a blood pressure cuff slightly above the systolic level for three minutes resultant ischemia enhances muscle irritability in hypocalcemic states Causes flexion of the wrist and thumb and extension of the fingers (carpopedal spasm)