11 - Ca, PO4, Mg Flashcards Preview

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Flashcards in 11 - Ca, PO4, Mg Deck (43):
1

electrolyte rule of 3s

Ca, P, Mg
controlled by PTH, VitD, phosphatonins
affect bone, intestine, kidney

2

PTH - stimulated by, inhibited by

stim: low ionized Ca (inactivation of Ca Sensing Receptor)
inc serum phosphate, low serum Mg

inhib: inc ionized Ca levels
calcitriol

3

how are hypomagnesemia and hypocalcemia associated with each other?

hypomagnesemia affects cGMP signaling > PTH unable to work at bone / release Ca

4

how does PTH inc serum Ca?

inc resorption of bone > release Ca and PO4
inhibit PO4 reabs in kidney in PCT (less PO4 to bind Ca > more free Ca)
inc reabs of Ca in DCT and stimulates renal 25(OH)D-1-hydroxylase > activation of vit D > abs of Ca from GI tract

5

Ca sensing receptor - location

kidney, parathyroid gland, intestine

6

action of Ca sensing receptor (CaSR) in parathyroid gland

less PTH produced

7

action of CaSR in kidney

thick ascending loop
when activated, inhibits apical K channel
Ca absorption stops
end result is like furosemide > calciuresis

8

treating hyperPTH

cinacalcet - binds to CaSR

also can try calcitriol (form of vit D) for feedback inhibition, or surgical parathyroidectomy

9

activation of Vit D

first by 25-hydroxylase in liver
then 1-alpha hydroxylase in kidney

10

another name for activated vit d

calcitriol

11

what stimulates activation of vit d?

PTH (feedback)
low PO4, low Ca
estrogen, prolactin, calcitonin, growth hormone

12

actions of calcitriol

inc Ca, Mg, PO4 abs in intestine
inhibit PTH secretion

13

phosphatonins - example, where made, what is main message

FGF23
bone
tells kidneys to dump PO4

14

what hormone is high in CKD due to PO4 retention?

phosphatonins

15

calcitonin

minor role in Ca reg
opposite of PTH
lowers serum Ca

16

nl serum Ca

9-10.4 mg/dl

17

serum Ca distribution and how it is affected by change in acid base state

nl - 45% protein bound, 45% ionized, 10% complexed
acidosis - inc ionized Ca
alkalosis - dec ionized Ca

18

where in the nephron is Ca transport hormone regulated?

DCT

19

how to correct serum Ca for albumin

corrected = Ca + (4-albumin)*0.8

20

etiologies of hypocalcemia

absence of PTH gland/function
hypomagnesemia
ineffective PTH - vit D def, malabsorption of Ca
PTH overwhelmed - hyperphosphatemia causes Ca PO4 complexing

21

presentation of hypocalcemia

tetany, Trousseau and Chvostek signs
seizures, neuropsych changes
prolonged QT, arrhythmias, hypotension, HF
coarse scaly skin, cataracts

22

tx of hypocalcemia

correct underlying dz
give Ca and/or vit D

23

causes of hypercalcemia

hyperPTH
acidemia
immobilization (>breakdown of bone)
vit D and Ca abs in GI, lots of milk
thiazide diuretics
familial hypercalcemia
granulomatous production and calictriol

24

presentation of hypercalcemia

"bones stones groans abd moans"
vasoconstriction, HTN, short QT
ulcers, constipation, pancreatitis
lethargy, obtundation, psychosis, weakness
extraskeletal calcifications - dermal, ocular, vascular, visceral organs

25

how can hypercalcemia affect kidney?

AKI
nephrogenic DI
stones
calicifications

26

tx for hypercalcemia

optimize renal excretion by giving Na and water to lessen reabs in PCT, promote Ca loss at LoH w/ loop diuretics
inhibit bone resorption w/ calcitonin or bisphosphonates

** most important is aggressive volume replacement

27

MCC hypercalcemia (2)

primary hyperPTH and malignancy

28

how is GI abs of PO4 regulated?

inc by calcitriol
no way to reduce it though - kidneys must remove excess absorbed

29

how is PO4 reabs in the kidney handled?

most reabs in PCT
inhib by PTH and FGF23 via reducing transporter expression

30

causes of hypoPO4

severe alcoholism
gluc infusion after starvation
elevated PTH
Fanconi syndrome
PO4 binding antacids
vit D deficiency > dec GI abs
certain tumors / neoplastic syndrome

31

presentation of hypoPO4

acute:
inadequate ATP production
muscle weakness/necrosis
cardiac failure, neurologic dysfunction
hemolysis, tissue hypoxia
impaired platelet and macrophage function

chronic - inc bone resorption - demineralization and pain

32

tx of hypophosphatemia

milk, cheese, eggs, supplements
IV in emergencies, but can cause severe hypocalcemia by complexing w/ Ca

33

causes of hyperPO4

tumor lysis
rhabdomyolysis (also trauma/crush)
kidney dz

34

consequences of hyperPO4

complexes w/ Ca > deposits everywhere. Calciphylaxis has VERY high mortality

secondary hyperPTH:
hypocalcemia due to complexing > release of PTH
osteitis fibrosa cystica and metastatic califications

35

tx of hyperPO4

correct underlying problem
3 d's: diet, dietary binders (PO4 binders like Mg, Al, Ca, etc), dialysis

36

causes of Mg cell efflux and influx

efflux - beta stim
influx - insulin, calcitriol, vit B6

37

role of Mg in body

DNA/protein synth
neuronal activity, cardiac excitability, vasomotor tone / BP
cofactor for transport of K and Ca

38

where is most Mg reabs in kidney?

thick ascending limb

39

hypomagnesemia cause

malnutrition, alcoholism, malabsorption
renal wasting after nephrotoxic drugs

40

hypomagnesemia presentation

muscle weakness, tremors, fasciculations, arrhythmias
neuro/psych changes
hypocalcemia, hypokalemia

41

hypermagnesemia causes

iatrogenic (use as tocolytic)
Mg containing antacids

42

presentation of hypermagnesemia

thirst, nausea, vomiting
drowsiness, hypotension, depressed DTR
coma, resp paralysis, cardiac arrest

43

tx of hypermagnesemia

initial - IV Ca - stabilize heart
loop diuretics
dialysis