Parathyroid Pathophysiology Flashcards
1
Q
how many parathyroid glands are there?
A
4
2
Q
PTH
A
- parathyroid hormone, parathormone
- released into the bloodstream by negative feedback mechanism
- depended on plasma calcium concentration
- half-life is 4 min
3
Q
avg PTH level
A
8-51 pg/mL
4
Q
hypocalcemia
A
release parathormone
5
Q
hypercalcemia
A
suppress synthesis and release of parathormone
6
Q
function of PTH
A
maintains normal plasma calcium concentration
7
Q
what three interfaces does calcium move across
A
- GI tract
- renal tubules
- bone
8
Q
resorption
A
- in context of physiology is absorption into the circulation
- osteoclasts break down the bone tissue and release minerals, resulting in transfer of calcium from bone tissue to the blood
9
Q
osteoclasts
A
- found on surface of bones and are multi-nucleated cells that contain numerous mitochondria and lysosomes
- break down bone tissue by digestion and degradation
10
Q
calcitonin
A
- opposes effects of PTH
- secreted by parafollicular cells in thyroid
- secretion stimulated by hypercalcemia
11
Q
PTH three ways of raising blood calcium
A
- bone resorption by osteoclasts
- increased calcium reabsorption by kidneys (and decreased phosphate reabsorption)
- increased calcium reabsoprtion by intestines
12
Q
3 ways calcitonin lowers blood calcium
A
- inhibits osteoclast activity in bones
- inhibits renal tubular cell reabsorption of Ca2+
- inhibits Ca2+ absorption in the intestines
13
Q
vitamin D
A
- fat soluble
- increases intestinal absorption of calcium, mag, and phos
- contributes to calcium homestasis and metabolism
- vitamin D receptors located in the intestines, kidneys, bone, and parathyroid gland
14
Q
vitamin D receptors functions
A
- helps transport proteins absorb calcium in intestine
- bone resorption
- reabsorption of calcium in distal nephron
15
Q
normal total calcium level
A
- includes bound and free
- 9.5-10.5 mg/dL
16
Q
normal iCal
A
4.75-5.7 mg/dL
free calcium
17
Q
calcium in the body
A
- 50% bound to albumin
- 40% ionized
- 10% bound to chelating agents
18
Q
acidosis and serum calcium
A
increases serum calcium
protein binding decreases as pH decreases
increased ionized fraction
19
Q
alkalosis and serum calcium
A
decreases serum calcium
decreased ionized fraction
20
Q
how much does calcium increase with each 0.1 decrease in pH?
A
0.05 mmol/L
21
Q
biological functions of calcium
A
- bone formation
- reservoir for ECF
- blood clotting
- excitability of nerve and muscle
- metabolic regulation for action of hormones and enzyme activation
22
Q
disorders r/t PTH
A
- reduced production of PTH - DiGeorge, CATCH 22, autoimmune
- impaired PTH due to peripheral resistance
- parathyroid gland adenomas
23
Q
hyperparathyroidism
A
- excess production of PTH
- most common cause of hypercalcemia defined as total serum calcium above 10.4
- classifications = primary, secondary, ectopic
24
Q
primary hyperparathyroidism causes
A
- benign adenoma (80-90%)
- hyperplasia
- carcinoma
25
s/s hyperparathyroid
- involve kidneys and skeletal system
- calcium deposits in renal parenchyma or recurrent nephrolithiasis
- skeletal pathology
- symptoms more common at calcium levels above 11.5-12
26
diagnosis of hyperparathyroid
- PTH assay
- calcium level
- vitamin D levels
- renal function
- CT scan
- has anything happened to neck?
- albumin?
27
medical management of hyperparathyroid
- used for mild, asymptomatic disease
- mild hypercalcemia (12) --> hydration
- moderate to severe hypercalcemia (13-15) --> IV saline hydration and furosemide to promote Na/Ca diuresis
28
surgical management of hyperparathyroid
- definitive treatment
| - intraop PTH assay measured before and at 5 min intervals after adenoma removal to confirm a rapid fall to normal
29
multiple gland hyperplasia treatment
- three removed with partial excision of fourth (leaving a good blood supply)
- total parathyroidectomy performed with immediate transplantation of a removed, minced parathyroid gland into the forearm muscles
30
hypoparathyroidsim
- absence or deficiency of PTH secretion
- resistance of peripheral tissue to effects of hormone
- iatrogenic (removed surgically with thyroidectomy)
- result = hypocalcemia
31
hypocalcemia s/s
- neuronal irritability
- skeletal muscle spasms
- tetany (reduced calcium lowers threshold for depolarization)
- seizures
- fatigue and mental status changes
- prolonged AT
- CHF (chronic)
- hypotension (acute)
- chvostek's sign
- trousseau's sign
32
what can acute hypocalcemia present with?
- stridor
- laryngospasm
- apnea
33
hypocalcemia treatment
- electrolyte replacement
- calcium and vitamin D
- hypomagnesemia managed with oral or IV replacement
- severe requires 10-20 mL of 10% calcium gluconate OR 3-5 mL of 10% calcium chloride followed by a continuous infusion of calcium (1-2 mg/kg/h)
34
anesthesia and hypocalcemia
-treat prior to elective surgery
35
major anesthetic risks of hypocalcemia
- decreased cardiac contractility
- dysrhythmias
- tetany
- altered response to muscle relaxants
- risk for laryngospasm
36
overactive parathyroid gland
- 1 in 100 people will develop parathyroid gland tumor
- treatment = surgical removal
- without treatment = fatigue, bad memory, kidney stones, osteoporosis
37
anesthetic management of parathyroidectomy
- concern for cardiac dysrhytmias secondary to elevated calcium
- NIMs ETT (assess RLN)
- effects of NMBDs unpredictable (consider qualitative NMB monitoring)
- careful positioning (risk for fractures)
- post op complications similar to thyroid
38
post op complications of parathyroidectomy
- RLN injury
- hematoma
- hypocalcemia
39
PTH sampling during surgery
- baseline PTH
- scheduled PTH samples in OR at time 0 (removal of parathyroid as alerted by surgeron) AND time 5, 10, and 15 min post parathyroid removal
