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Renal II Quizam 1 > Lecture 6: Fluid and Electrolyte Disturbance - Ca, Mg, PO > Flashcards

Lecture 6: Fluid and Electrolyte Disturbance - Ca, Mg, PO Flashcards

1
Q

Free Ca2+ is important for what part of tissue excitability/AP’s?

Effect of low and high Ca2+ levels?

A
  • Calcium controls the AP threshold
  • ↓ Ca2+ lowers threshold
  • ↑ Ca2+ raises threshold
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2
Q

What is the effect of hypoalbuminemia on serum Ca2+ levels?

A
  • Decreases TOTAL serum [Ca2+]
  • WITHOUT affecting ionized Ca2+ level

*Ionized Ca2+ is free and unbound!

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3
Q

If serum albumin is abnormal, clinical decisions should be based on which level of Ca2+?

A

IONIZED Ca2+ levels

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4
Q

Which 3 hormones regulate Ca2+ levels?

A
  1. Calcitriol (1,25 OH Vit D3) –> works to ↑Ca2+
  2. PTH –> works to ↑Ca2+
  3. Calcitonin –> ↓Ca2+
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5
Q

3 major sites of regulation for Ca2+?

A

1) Kidney
2) Bone
3) Intestine

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6
Q

What are the main effects of PTH on serum ion levels?

A

↑ plasma [Ca2+] and ↓ plasma [PO43-] —> increased ionized plasma Ca2+

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7
Q

What are the 3 main sites of action for PTH?

A
  • Distal nephron to increase Ca2+ reabsorption
  • Inhibits PO43- reabsorption in proximal tubule
  • Enhances bone release of Ca2+
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8
Q

Secretion of PTH is controlled chiefy by serum [Ca2+] acting where?

A

Calcium-sensing receptors on parathyroid cells

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9
Q

65% of filtered calcium is reabsorbed where?

Predominantly by which type of transport?

A
  • Proximal tubule
  • Predominantly paracellular (passive)
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10
Q

Where in the nephron is the major site of calcium regulation?

A

Distal tubule

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11
Q

How is calcium reabsorbed in the distal tubule, the major site of regulation?

Regulated by which hormone?

A
  • Renal epithelial Ca2+ channel (TRPV5) - along with calnindin
  • Regulated by 1,25 vitamin D3 (calcitriol)
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12
Q

What are major causes of Hypercalcemia?

A
  • Primary hyperparathyroidism
  • Thiazide diuretics
  • Milk-alkali syndrome (i.e., antacids)
  • Malignancy
  • Immobilization syndrome
  • Granulomatous Dz
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13
Q

Hypercalcemia is almost always causes by increased entry of calcium into the ECF due to what 2 factors?

A
  1. Bone resorption
  2. Intestinal absorption
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14
Q

Severe hypercalcemia is often associated with symptoms related to what 2 systems and what are they?

A
  1. GI sx’s = anorexia, N/V, and constipation
  2. Neuro = weakness, fatigue, confusion, stupor, and coma
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15
Q

How does polyuria, nausea and vomiting associated with hypercalcemia contribute to worseing sx’s?

A

Cause marked hypovolemia, resulting in impaired calcium excretion, thereby worsening the hypercalcemia

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16
Q

What are drugs/treatments that can be given for the management of hypercalcemia?

A
  • ECF volume replacement w/ 0.9% saline
  • Furosemide = Ca2+ losing diuretic
  • Calcitonin
  • Glucocorticoids
  • Hemodialysis
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17
Q

For hypercalcemia not responding to saline diuresis, and especially if secondary to malignancy, therapy with what is required?

A

Bisphosphonates

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18
Q

True hypocalcemia is present only when which level is reduced?

A

Ionized calcium

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19
Q

Common causes of hypocalcemia?

A
  • Hypoparathyroidism
  • Acute pancreatitis
  • Chronic kidney disease
  • Rhabdomyolysis = Ca2+ in injured ms.
  • Parathyroidectomy
  • Pseudohypoparathyroidism –> failure to respond to PTH
  • Familial hypocalcemia
  • Vit D deficiency
  • Septic shock
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20
Q

Major cardiovascular signs/sx’s of hypocalcemia?

A
  • Hypotension
  • CHF
  • Dysrhythmias
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21
Q

Major neuromuscular irritability signs/sx’s of hypocalcemia?

A
  • Paresthesias, numbness
  • Muscle twitching and cramping
  • Tetany
  • General fatigability and muscle weakness
  • Seizures
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22
Q

Trousseau’s sign and Chvostek’s sign will be (+) in which settings?

A
  • Hypocalcemia
  • Hypomagnesemia
  • Alkalosis (decreases ionized Ca2+)
23
Q

In an emergency situation in which hypocalcemia is suspected and seizures, tetany, hypotension, or cardiac arrhythmias are present what is the treatment?

A

IV calcium

24
Q

Pts w/ chronic, mild hypocalcemia or hypoparathyroidism can be managed how?

A

Calcium and vitamin D supplements

25
What % of body phosphorous is in the ECF?
1%
26
Effect on serum phosphate levels with CHO or glucose infusion?
**Decreased**
27
What are the 4 major regulatory hormones for Phosphate? Which decrease and which increase levels?
- **PTH** --\> ↓ serum PO43- and ↑ renal excretion - **FGF-23** --\> ↓ serum PO43- and ↑ renal excretion - **1,25(OH)D3** ---\> ↑ PO43- and ↑ intestinal phosphate absorption - **Insulin** ---\> ↓ serum PO43- and shifts phosphate into cells
28
Where is FGF-23 released from and what is its effect on serum PO43- levels?
**Promotes** PO43- excretion by the kidney = **decreased serum levels**
29
A major portion of phosphate is reabsorbed in the PCT by which transporter? What 2 hormones regulate this transpoter?
**NaPi2** = **highly regulated** by **PTH** and **FGF-23**
30
Why is a fall in GFR highly problematic for phosphate regulation?
Kidneys excrete 900 mg/day or about 65% of our intake!
31
What are 2 major causes of decreased renal excretion of phosphorous leading to hyperphosphatemia?
- CKD **stages 3-5** - Acute renal failure/AKI
32
Many of the signs and sx's of an acute rise in serum phosphate are the result of what?
Concomitant **hypo**calcemia due to **deposition of calcium in soft tissues** and a resultant **fall in ECF ionized Ca2+**
33
Severe hyperphosphatemia may result in what tissue manifestations?
Tissue ischemia or **calciphylaxis** (vascular calcification/necrosis)
34
Chronic hyperphosphatemia contributes to what disorder?
Renal osteodystrophy
35
How is acute hyperphosphatemia managed clinically?
Saline diuresis
36
How is hyperphosphatemia managed in end-stag kidney disease?
Reduce dietary intake/intestinal absorption (phosphate binders)
37
What is Renal Osteodystophy? How does CKD contribute to its development?
- **Bone demineralization** due to **CKD** - Due to **HYPER****parathyroidism**secondary to**HYPER****phosphatemia**... kidney unable to excrete phosphate - **Combined** w/ **HYPO****calcemia** --\> kidney unable to activate vit D to calcitriol needed for Ca2+ absorption from diet
38
What are the treatment options for Renal Osteodystrophy associated w/ CKD?
- Ca2+/Vit D supplementation - Restriction of dietary phosphate, use of **phosphate binders** - **Hemodialysis**/**renal transplantation** - **Cinacalet** (calcium sensitizer drug, lowers PTH)
39
What is often times a cause of death in starving people/anorexics when given a large bolus of food too quickly?
- Re-feeding **HYPOphosphatemia** - Too much phosphate will be taken up into cell as hexokinase phosphorylates glucose
40
What are some of the major causes of Hypophosphatemia?
- **re-feeding hypophosphatemia** - Alcohol-related - Diabetes mellitus --\> Tx w/ large dose of insulin - Urinary loss ---\> Fanconi syndrome - Oncogenic osteomalacia --\> tumor making FGF-23
41
Chronic hypophosphatemia causes what in children and adults?
- **Rickets** in children - **Osteomalacia** in adults
42
What are some of the muscular and CV abnormalities causes by hypophosphatemia?
- Weakness - Rhabdomyolysis - Impaired diaphragmatic function - Respiratory and Heart failure
43
What are 2 hemologic abnormalities caused by hypophosphatemia?
- Hemolysis - Platelet dysfunction
44
Hypophosphatemic patients frequently have low levels of what other ions that need to be corrected?
- **Hypokalemic** - **Hypomagnesemic**
45
What is the function of ionized magnesium found intracellularly?
Crucial role as **cofactor** in many biochemical and physiological processes such as ATPases, reg. of ion channels and translational processes
46
What is the major site of magnesium reabsorption in the nephron?
Thick ascending limb \*Hence why loop diuretics cause hypomagnesemia, although **thiazides cause more severe hypomagnesemia**
47
What is the site of magnesium fine-tuning in the nephron? Primary driver of cellular Mg2+ influx?
- DCT - Electrical potential is **primary driver**
48
Hypomagnesemia is most often seen in which patients?
ICU patients (60%)
49
Hypomagnesemia in ICU patients is primarily caused by what 5 factors? Which drugs can caused decreased reabsorption?
- Decreased nutrition - Diuretics - **Decreased reabsorption** due to **PPIs = IMPORTANT!!!** - Decreased albumin - Aminoglycosides
50
How common is hypermagnesemia?
**Rarely seen**, due to efficient elimination by kidneys!
51
Although rare, what are 3 causes of Hypermagnesemia?
- End-stage renal disease - Massive intake i.e., **Epsom salt** - **Magnesium infusion** i.e., in **pregnant** women w/ **pre-ecclampsia/ecclampsia** to limit neuromuscular excitability
52
If plasma magnesium is \>12 mg/dL what signs/sx's will occur?
**Muscle paralysis** --\> flaccid quadriplegia, apnea and respiratory failure, complete heart block, and cardiac arrest
53
Treatment of hypermagnesemia in pt w/ normal renal function vs. reduced renal function vs. end-stage renal disease?
- **Normal** = stop administration and wait and/or add loop or thiazide diuretic - **Reduced funtion** = same as above + **add saline infusion** - **End-stage** = dialysis

Renal II Quizam 1 (7 decks)

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