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calcium, magnesium, & phosphorus Flashcards

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1
Q

What are the major cations in the body?

A

calcium, magnesium & phosphorus are major cations in the body → positive ions

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2
Q

How are calcium, magnesium & phosphorus absorbed & eliminated in the body?

A
  • ingested through diet & absorbed from the intestines
  • filtered in the glomerulus & reabsorbed in renal tubles
  • excreted through the urine
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3
Q

Where are calcium, magnesium, & phosphorus found in the body?

A

In the bone:
- 99% of calcium
- 85% of phosphorus
- 55% of magnesium
The rest is found in the cells → only a small amount in the ECF ( in the blood); they are intracellular ions

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4
Q

What are Ca++, Mg+ & phosphorus regulated by?

A

-vitamin D
- parathyroid hormone
- calcitonin

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5
Q

What is the role of Vitamin D in Ca++ & phosphorus?

A

Even though vitamin functions as a hormone → fat-soluble vitamin
- maintains normal calcium & phosphorus levels by increasing absorption from the intestines → when we need more Ca++ or phosphorus; vitamin D works to produce more

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6
Q

What is the role of parathyroid hormone in Calcium & phosphorus regulation?

A
  • major regulator of calcium & phosphorus → secreted by parathyroid glands
  • main job is to maintain ECF & calcium levels
  • requires vitamin D & mag to work
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7
Q

How does parathyroid hormone (PTH) control calcium?

A

when calcium is high → PTH is inhibited
- PTH levels are low
When calcium is low → PTH is stimulated
- PTH levels are high

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8
Q

How does PTH control phosphorus?

A

when calcium & magnesium are reabsorbed, there is increased excretion of phosphorus
- Calcium & phosphorus have an inverse relationship to each other

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9
Q

What happens with PTH in hypocalcemia?

A
  • low concentration of calcium in the blood causes release of PTH
  • release of PTH causes an efflux (pull away) of Ca++ from the bone
  • When PTH is released, we decrease loss of Ca+ in the urine (kidneys kick in)
  • Vitamin D kicks in to enhance the absorption of calcium from the intestine
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10
Q

how is calcium taken in, absorbed, stored & excreted?

A

Ca++ enters the body through the GI tract & is absorbed by the effects of vitamin D.
It is stored in the bone (small amount in the blood) & excreted by the kidneys

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11
Q

What percent of calcium is protein bound (to albumin) & cannot pass through the capillary wall and what does this mean?

A

about 40%; this means → it is inactive & we can never use it (only hangs out with the protein)

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12
Q

What is 10% of calcium doing?

A

about 10% is known as complexed or chelated calcium & is combined with citrate, phosphate, etc.
- calcium citrate is used to prevent blood clotting in transfusions

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13
Q

What is 50% of calcium doing?

A

about 50% is ionized calcium which is able to leave the vascular compartment & participate in cellular function
- makes nerve cells less sensitive to stimuli

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14
Q

How much of the calcium in our body can we use?

A

About 50% of the calcium in our body can be used

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15
Q

What happens to Ca++ when albumin is low?

A

if a pt has low albumin, very often we see a falsley low calcium level because not enough calcium is there or the decreased albumin makes it so not enough calcium can bind
- by correcting it a lot of the times we see the issue was not with calcium levels but actually with albumin levels

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16
Q

What can you look at rather than correcting calcium for low albumin levels?

A

An ionized calcium level → another way to check the patient’s calcium & make sure it is normal (b/c the ionized calcium makes up about half of the calcium in the blood

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17
Q

What does calcium do?

A
  • Many enzyme reactions
  • bone development
  • action potential → as we see change in the threshold, we see sodium & calcium rush into the cell & then come back out so the potassium can go back in
  • neuron excitability
  • needed for skeletal, cardiac, & smooth muscle contraction
  • affects cardiac contractility & automaticity
  • essential for blood clotting (production of clotting factors) → all but the first 2 stops in the coagulation cascade; if we start to see problems with Ca++, we will start to see problems with bleeding
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18
Q

Where do we get calcium from?

A

dietary sources:
- milk
- dairy
- kale
- brocolli
- bony fish
- seeds & nuts (almonds)
- beans
- peas
- meat
- fortified foods like OH & non-dairy milks

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19
Q

How much calcium is absorbed?

A

About 50% is absorbed & the rest is eliminated in the stool
- about 150mg/day is absorbed
- only about half of what we take in a day is actually absorbed → this is why it is crucial to make sure we are increasing that dietary intake of calcium
- older adults (peri/post menopausal women → taking Ca++ supplements could be dangerous; recommendation is to replace & fortify with dietary intake
-If intake is less than what is secreted into the bowel, → the patient will become hypocalcemic

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20
Q

What is the calcium level for hypocalcemia?

A

less than 8.5mg/dL

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21
Q

What percentage of critical care pts csan hypocalcemia affect?

A

70%

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22
Q

What can cause hypocalemia?

A
  • changes in acid-base balance
  • pancreatitis
  • hypoparathyroidism
  • deficit from diet affects the bones rather than blood levels
  • unable to make vitamin D (such as CKD or in some medications like seizure meds)
  • loop diuretics (furosemide(lasix)) can cause hypokalemia & hypocalemia, INH (used for tb), corticosteroids, aminoglycosides
  • massive amounts of blood transfusions ( citrate binds & takes away ionized calcium) → puts calcium citrate into blood to prevent clotting; this takes away ionized calcium, which can be bad b/c the ionized calcium is the type that we need to take care of things
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23
Q

What are the clinical manifestations of hypocalcemia?

A

can be acute or chronic
- acute hypocalcemia → increased neuromuscular excitability hypocalcemia revs things up
- causes overstimulation, repetitive response to single stimulus or even continuous activity

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24
Q

What are the S/S of hypocalcemia?

A
  • parathesia
  • tetany → spasms of muscles of face, hands, & feet
  • chvostek’s sign → tapping facial nerve right below temple (NOT always seen; absent in 30% of pt with hypocalcemia & seen in 10% of pt w/ normal calcium levels)
  • Trousseau’s sign → spasm after inflating BP cuff about 20mm above systolic pressure & wait 2-3 min will see spasms of fingers ( present in 94% of pts with hypocalcemia; only present in 1% of pts with normal calcium levels)
  • seizures
  • hypotension
  • dysrhythmias
  • poor response to medication
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25
How do you treat hypocalcemia?
acute hypocalcemia → treated with IV calcium gluconate - needs to be given slowly in D5W only → not NSS will cause increased renal loss - must watch carfully for extravasation → when meds leak into the tissue when IV goes bad & causes sloughing of the skin (in an ideal world → infused through central line) - place pt on seizure precautions (like w/ hyponatremia) - can cause postural hypotension so must stay in bed while recieving infusion
26
What value would be considered hypercalcemia?
greater than 10.5 mg/dL
27
What are the causes of hypercalcemia?
- elevated protein levels can increase total calcium levels but NOT the ionized levels: when albumin is high → calcium can be falsely elevated (think about the same corrected Ca formula) - occurs when calcium leveks move into the blood (ECF) faster than regulatory hormones or kidney excretion can control - **very common in malignancy ( about 10-20% of people w/ malignancy)** → either the tumor causes osteoclastic activity or humoral immune factors stimulate osteoclastic activity or prevent bone formation - hyperparathyroidism → if we have TOO much parathyroid we will have TOO much calcium
28
What are the less frequent causes of hypercalcemia?
- immobilization & decreased weight bearing → natural breakdown of bone density will cause a release of calcium in the blood - excessive vitamin D ingestion - excessive calcium or dairy intake (milk-alkali syndrome) → too much calcium carbonate antacids (ie. tums) - lithium & thiazide diuretics → increases PTH activity
29
What are the clinical manifestations of hypercalcemia?
- decreases in neuromuscular activity → lethargy, weakness, flaccid muscles - heart becomes irritable & ventricular arrhythmias occur → can be life-threatening - constipation & N/V - inhibits ADH so the person is always thirsty → when we feel we are low volume we usually produce ADH; so if ADH is not working properly the Pt will always feel thirsty - kidney stones (renal calculi) -pancreatitis → cause both hyper & hypo - osteoporosis ** bones,stones, groans, & psychic moans**
30
When do hypercalcemia sx or crisis usually start?
sx usually begin after level rise above 12 mg/dL & become more severe as levels rise but can be severe at any level Hypercalcemia crisis → results in acute increase in calcium with the mentioned sx; can result in death from arrhythmias (usually levels above 17mg/dL) → seen in malignancies
31
What is the tx for hypercalcemia?
**rehydration:** - urinary excretion of calcium → if Na+ is excreted Ca++ will go with it - loop diuretics - NSS fluid replacement - can use dialysis if renal failure or other Tx do NOT work - bisphosphonates (aldronate) work for hyperparathyroid disease → these help maintain & build bone; decrease osteoclastic activity & increase osteoblastic activity (help bring Ca++ levels down) - tx for malignancy
32
What are nursing interventions for hypercalcemia?
- double check PTH blood test → it will be elevated in hyperparathyroidism & be normal in malignancy - keep person mobile if able - increase fluid intake - fall precautions if confused → b/c they will be confused & lethargic - assess for cardiac abnormalities - Support the patient/family that the symptoms will resolve when the calcium is lower
33
What is the normal range for phosphorus?
2.4 to 4.5mg/dL (higher levels in babies & children)
34
How much of phosphorus is in the bone?
about 85% is in the bone & 1% in the blood
35
What is the role of phosphorus in the body?
- major in bone formation - needed to make ATP → why we need phosphorus; when we are low on phosphorus & cannot make enough to do its job we see probelms - metabolism of glucose, fats, & proteins - helps excrete hydrogen ions in acid-base balance
36
How is phosphorus taken in & excreted?
- get it from the diet & excrete it in the urine - body controls balance through absorption & excretion loop
37
What can a low protein diet lead to in relation to phosphorus?
low phosphorus; malnourishment or calorie restriction
38
What is inorganic phosphorus?
phosphate is in blood & is what is measured ** this is what we look at when we are looking at the phosphorus levels**
39
What is organic phosphorus?
phosphorus form is in the cells
40
What is the range for hypophosphatemia?
levels less than 2.5mg/dL → considered severe when less than 1.0mg/dL
41
What does hypophosphatemia come from?
comes from fluid shifts & losses through the kidneys
42
What causes phosphatemia?
- prolonged antacid use (calcium carbonate = tums, aluminum) → bind with phosphorus & increase excretion through stool - corticosteroids - loop diuretics - increased Mg+ intake - excessive alcohol intake - DKA - can occur w/ **increased glucose intake** → forces the insulin & phosphorus out of the blood & into the cell - TPN does NOT have enough phosphorus & can cause the phosphorus to go into the muscle → causes drop in blood levels - respiratory alkalosis - low vit D levels - People who are malnourished or critically ill → we usually see hypophosphatemia!!
43
What are the sx of hypophosphatemia?
** decreased ATP production** - altered neural function - altered musculoskeletal function → muscles will get weak; pt on ventilator and need to be weaned; will not be able to wean because they are not making that ATP if they have low phosphorus; Patient will not be able to inspire/ expire on their own - blood disorder - hypoxia to tissues - mental fogginess; irritability
44
What is the tx for hypophosphatemia?
- Can be treated with oral supplements → such as Potassium phosphate/ sodium phosphate (Neutra Phos) - Dose is typically 250-500 mg several times a day but is weight based - Levels checked 2-12 hours after given - Can be given IV if severe (usually under 1 mg/dL) → very irritating to the veins, must be given slowly, reserved for severe cases
45
What is the range for hyperphosphatemia?
levels exceeding 4.5mg/dL
46
What causes hyperphosphatemia?
- kidneys CANNOT excrete the phosphorus or extreme intake **most common cause is renal dysfunction** - Can also come from tissue injury such as → burns, heat stroke, low K+ (hypokalemic) - Excess intake of phosphorus containing antacids & laxatives - Lots of laxatives that are phosphorus-based based b/c it will help loosen stools
47
What are the clinical manifestations of hyperphosphatemia?
**Almost ALWAYS has an accompanying → HYPOcalcemia** - Common to see hyperphosphatemia & hypocalcemia in patients with renal disease/ dysfunction - Sx usually related to low calcium → Chvostek’s, Trousseau’s, cardiac irritability, neuromuscular irritability - Can lead to bone disease, hyperparathyroidism & calcifications in tissues
48
What is the tx for hyperphosphatemia?
- treat the cause! - can use dialysis if needed - AVOID phosphorus high foods → hard cheese, cream, nuts, meats, whole-grain cereals, dried fruits, dried vegetables, kidney beans/ meat, sardines, sweetbreads (banana/ zucchini bread), and foods made with milk
49
What foods are high in phosphorus
hard cheese, cream, nuts, meats, whole-grain cereals, dried fruits, dried vegetables, kidney beans/ meat, sardines, sweetbreads (banana/ zucchini bread), and foods made with milk
50
What is the 2nd most abundant ICF cation?
magnesium; 1st is k+
51
what is the normal range for magnesium?
1.8- 3mg/dL
52
What can abnormal calcium cause?
can cause other electrolyte imbalances
53
How much of mg+ is in the blood?
1% is in the blood
54
What is Mg+ needed for?
- needed for every step in DNA replication & transcription and RNA transcription - needed to created ATP (Na/K ATPase pump) action potential → w/o Mg+ start to see cardiac arrhythmias & muscular dysfunction - nerve conduction - potasium & calcium acticity → esp cardiac cells - smooth muscle relaxamnt - can tx seizures (cerebreal vasodilation) - causes peripheral vasodilation & affects peripheral resistance → can bring BP down
55
Where does Mg+ come in the diet?
- grains - nuts - meats - seafoods - green vegtables
56
Where is mg+ taken in and excreted out?
- Absorbed in small intestine & excreted by the kidneys - If everything is going okay → we usually won’t have much of a problem with our magnesium levels (if we have a healthy diet & the kidneys function properly)
57
what is the value for hypomagnesemia?
less than 1.8mg/dL
58
What are the possible causes of hypomagnesemia?
- comes from low intake or loss → Changes in movement in ICF/ECF (glucose, insulin, & acid base imbalances) - alcoholism - poor nutrition; calorie restriction - NG suction - hypokalemia/hypocalcemia - metabolic acidosis - diuretic use → b/c it washes everything out - usually related to low K+ & Ca++ → so think cardiac and neuro ** Hypomagnesemia → increases HYPOkalemia and the hypokalemia will NOT respond to K+ replacement ; The K+ will not rise until magnesium is corrected!!**
59
What are sx of hypomagnesemia?
** all sx of hypocalcemia** - neuro irritability/ cardiac irritability - parathesia - Chvostek's/Trousseau's - arrhythmias - long term can lead to osteoporosis
60
What is the tx for hypomagnesemia?
- mild can be corrected w/ diet or oral supplement - more severe deficiency needs IV replacement **Magnesium sulfate (IV form) must be given SLOWLY– no more than 1-2 gm per hours** - Can result in life threatening arrhythmias if given TOO fast - Can also cause diarrhea
61
What is the nursing care for hypomagnesemia?
- Assess cardiac stability → heart rhythm, pulses, perfusion - Look at other electrolytes → potassium & calcium - Assess for difficulty swallowing (dysphagia) → can increase risk of aspiration - Seizure precautions **Test question might be → Which of the following electrolyte abnormalities does the nurse need to assess for / put the patient on seizure precautions?** Sodium; Calcium; & Magnesium**
62
What is the value for hypermagnesemia?
above 3.0mg/dL
63
What are the causes of hypermagnesemia?
- Rare because kidneys usually are able to handle the excretion - Renal insufficiency is the most common – usually more in older adults - Too much magnesium containing laxatives or antacids - Over-treatment in Pre-eclampsia
64
What are the sx of hypermagnesemia?
**Slows down everything!** → decreased reflexes, muscle contraction, bradycardia - Causes irritability → depressed nerve function & muscle contractions; decreased DTRs - N/V - muscle weakness - hypotension - bradycardia - respiratory depression
65
what is the tx for hypermagnesemia?
- Can be treated with diuretics and NSS if kidneys are working - In those with severe renal disease → treated with IV calcium gluconate ; Would also need dialysis for the kidney disease - Avoid ALL magnesium-containing medications and IV solutions (i.e., Lactated Ringer’s)
66
What is the nursing care for hypermagnesemia?
- Assess for cardiac instability – hypotension (due to vasodilation) ; If we have too much they become critically hypotensive → getting them out of bed can be very dangerous b/c of increased risk of falls - Assess DTRs → will be decreased or absent; Patients with preeclampsia → need to have neuro status & DTRs monitored frequently **Possible on test → What electrolyte imbalances can cause postural hypotension/ hypotension? Hypermagnesemia & hypocalcemia!!**

medsurg 2 (3 decks)

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