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Special Populations > Exam 2: Endocrine > Flashcards

Exam 2: Endocrine Flashcards

1
Q

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

A

adrenergic and cholinergic

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2
Q

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

A

negative

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3
Q

half-life of T4 in circulation is:

A

6-7 days

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4
Q

half-life of T3 in circulation is:

A

24-30 hours

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5
Q

which thyroid hormone is the active, free form?

A

T3
unbound, more potent, and short half-life

T4 is converted to T3 in the target cell

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6
Q

where is the concentration of T4 the highest?

A

the blood

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7
Q

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

A

T4

T3 = mostly extrathyroid conversion of T4 to T3

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8
Q

which undergoes more protein binding between T4 and T3?

A

T4

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

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9
Q

how do hyper- and hypothyroidism affect MAC?

A

no effect on MAC requirements

elevated thyroid hormones increase O2 consumption in all tissues except CNS

therefore, MAC requirements remain the same

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10
Q

how do elevated thyroid hormones affect induction?

A

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

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11
Q

what are the effects of thyroid hormone on cardiac myocytes?

A

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

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12
Q

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

A

decreases systemic vascular resistance via direct vasodilation
increases intravascular fluid volume

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13
Q

what are the general findings in hypothyroidism?

A

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)

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14
Q

what is the first line of treatment for hyperthyroidism?

A

antithyroid drug:
methimazole, propylthiouracil, iodide

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15
Q

propylthiouracil (PTU)

A

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

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16
Q

methimazole (tapazole)

A

prevents production of more thyroid hormone

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17
Q

dexamethasone and hydrocortisone for hyperthyroidism

A

blocks conversion of T4 to T3

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18
Q

beta blockers in hyperthyroid: propranolol and esmolol

A

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

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19
Q

what can thyroid storm mimic under anesthesia?

A

malignant hyperthermia
pheochromocytoma
neuroleptic malignant syndrome
light anesthesia

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20
Q

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

A

euthyroid

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

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21
Q

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

A

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

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22
Q

what is the range of serum calcium?

A

8.5 to 10.5 mg/dL

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23
Q

in what three forms does calcium exist?

A

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

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24
Q

what two forms of calcium are diffusible across capillary membranes?

A

bound to anions and ionized

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25
Q

normal level of ionized calcium in the blood

A

4.7 to 5.2 mg/dL

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26
Q

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

A

ionized calcium

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27
Q

what is the function of PTH?

A

regulate calcium

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28
Q

what is PTH secretion determined by?

A

the fraction of ionized calcium in the blood

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29
Q

what two things increase PTH synthesis and release?

A

low ionized calcium and vitamin D

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30
Q

maintenance of steady-state calcium balance is provided by:

A

GI absorption

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31
Q

what are the three sources of Calcium resorption/absorption?

A

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)

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32
Q

what controls calcium homeostasis?

A

PTH calcium feedback loop

33
Q

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

A

PTH gland
GI intestines
Kidney
Bone

34
Q

what is the significance of calcium on blood coagulation?

A

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

35
Q

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

A

muscle contraction (skeletal and cardiac)
bone formation
cell division

36
Q

how does alkalosis affect ionized calcium levels?

A

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

37
Q

how does acidosis affect ionized calcium levels?

A

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

38
Q

most common cause of hypercalcemia is:

A

excess PTH

39
Q

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

A

osteoclast-mediated bone resorption and hypercalcemia

40
Q

hypercalcemia is defined as total serum calcium above:

A

10.4 mg/dL

(normal range 8.5 to 10.5 mg/dL)

41
Q

what is the most common cause of hyperparathyroidism?

A

solitary benign adenoma (80%)

42
Q

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

A

15%

43
Q

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

A

MEN I and MEN IIA

44
Q

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

A

Medullary (solid) thyroid carcinomas and pheochromocytoma

50% of patients with MEN IIA develop pheochromocytomas and up to 30% develop hyperparathyroidism

45
Q

what are skeletal symptoms of hypercalcemia and hyperparathyroidism?

A

skeletal demineralization
collapse of vertebral bodies
pathologic fractures***

46
Q

what are gastrointestinal symptoms of hypercalcemia and hyperparathyroidism?

A

pancreatitis
peptic ulcers
abdominal pain
vomiting

47
Q

what are renal symptoms of hypercalcemia and hyperparathyroidism?

A

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

48
Q

what are cardiac symptoms of hypercalcemia and hyperparathyroidism?

A

bradycardia/arrhythmia
prolonged PR interval
shortened QT interval
systemic HTN

49
Q

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

A

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

50
Q

with severe and protracted hyperparathyroidism bones can become ____

A

painful and susceptible to fracture

51
Q

what are hematopoietic symptoms of hypercalcemia and hyperparathyroidism?

A

anemia

52
Q

what are nervous system symptoms of hypercalcemia and hyperparathyroidism?

A

somnolence
decreased pain sensation
psychosis

53
Q

what are ocular symptoms of hypercalcemia and hyperparathyroidism?

A

calcifications (keratopathy) and conjunctivitis

54
Q

management of mild hypercalcemia (12 mg/dL):

A

hydration

55
Q

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

A

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

56
Q

what is given to treat hypophosphatemia?

A

phosphate

there is no compensatory mechanism for phosphate

57
Q

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

A

GETA

58
Q

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

A

cervical plexus block and MAC

59
Q

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

A

NS 150 mL/hr (NO LR)

60
Q

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

A

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

61
Q

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

A

bladder catheterization
CVP monitoring
frequent serum electrolyte checks

62
Q

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

A

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

63
Q

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

A

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

64
Q

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

A

hypocalcemia

65
Q

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

A

rapid bone uptake of calcium (AKA “hungry bone syndrome”)

66
Q

_____ occurs when calcium falls below _____ mg/dL

A

Tetany; < 6 mg/dL

67
Q

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

A

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

68
Q

what cardiac dysrhythmias are associated with hypocalcemia?

A

prolonged QT interval
(torsades)

69
Q

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

A

Calcium gluconate IV. Hypocalcemia can cause tetany.

70
Q

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

A

unintentional removal of the parathyroid glands during thyroid or parathyroid surgery

71
Q

what lab results indicate hypocalcemia and hypoparathyroidism?

A

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

72
Q

what will phosphate levels be in hypoparathyroidism?

A

elevated

d/t decreased renal excretion of phosphate

73
Q

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

A

activated vitamin D
calcium
magnesium

74
Q

hypocalcemia produces _____ of nerve and muscle cells

A

hyperexcitability

75
Q

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

A

laryngospasm

76
Q

deep tendon reflexes in hypocalcemia are ____

A

hyperactive

77
Q

chvostek sign

A

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

78
Q

trousseau’s sign

A

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)

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