Renal-Electolytes Flashcards
What is the role and effect of increased TRPV5
TRPV5 increases the amount of calcium that is reabsorbed in the distal convoluted tubule
Where is calcium reabsorbed and what is the mechanism
- 65 in the proximal tubule via paracellular manner
- 20 in the thick ascending loop via positive voltage paracellular manner
- 8 in distal tubule, but is active transport and very regulated
The Chvostek’s sign and Trousseau’s sign are seen in which conditions
- Hypocalcemia (main one)
- hypomagnesemia and alkalosis (decreased ionized calcium)
What are the general causes of extracellular edema
- Increased capillary hydrostatic pressure
- loss of plasma proteins
- Increased capillary permeability
- Blockage of lymph return
What is the main location and the main mechanism of phosphate reabsorption in the kidneys
55-85% in the proximal convoluted tubule vie NaPi2
Where is the majority of calcium in the body stored
Bone
What is the mechanism that chronic renal disease cause bone demineralization (aka renal osteodystrophy)
- Kidneys start to fail and unable to excrete the Needed phosphate, causing hyperphosphatemia
- Hyperphosphatemia causes secondary hyperPTHism (causes bone demineralization)
- Kidney is unable to activate Vitamin D to calcitriol, which results in inability to absorb Calcium from the diet
What is the treatment of hypermagnesemia in patients with reduced renal function
Add saline and diuretic
What is the treatment for hypocalcemia
- Intravenous calcium (emergency situations0
- Oral calcium, can be with vitamin D (chronic, mild hypocalcemia)
- Calcium and Vitamin D (hypoPTH)
What are the main causes of hyperphosphatemia
- Chronic kidney diseases stage 3-5
- Acute renal failure/injury
RBC cell lysis can cause which pseudosyndrome
Pseudohyperkalemia
Hypokalemia leads to changes in which metabolic serum level
Causes hyperglycemia because the glucose can not be brought into the cell since potassium is needed
What is the merchandise of fibroblast growth factor 23 (FGF) on phosphate levels
-Released by bones that promote phosphate excretion by the kidneys
What is usually the result of renal failure on phosphate levels
Because the kidneys are the main excretion route, a decreased GFR results in inability to clear the necessary 900mg/day
What is the treatment for level 1 hyponatremia
Very minimal symptoms, so fluid restrictions
What is the conductance of calcium across TRPV5 regulated by
PTH and locally synthesis of kallikrein
Which drugs will cause ECF potassium to be excreted
Aldosterone
What is the effect of aldosterone ad where is it working
Works in the principal cells in the collecting duct, and serves to increased the amount of sodium reabsorption, which causes potassium to leak out into the lumen and urine
What are the sites or calcium regulation
Kidney, bone, intestine
What is the treatment for hyperphosphatemia
- Calcium and vitamin D supplementation
- Restriction of phosphate in diet and phosphate binders
- Hemodualysis and renal transplant
- Cinacalcet (lowers PTH)
What is the correction amount for hypernatremia
Over 48 hours as
What is the effect of increased calcium levels on the threshold
Increases the threshold
What is the function of angiotensin 2 on maintaining GFR
Maintains the resistance in efferent arterioles, so as a result, the GFR is maintained
Plasma ADH levels are most sensitive to which plasma level content
The plasma osmolality is the largest determiner
How is the level of PTH controlled
-Serum calcium sensor receptors on parathyroid cells that is activated with low [Ca] levels
What are the most common causes of hypercalcemia
- Bone resorption
- Intestine absorption
- Usually in conjunction with decreased renal calcium clearance
What are the causes of intracellular edema
- Depression of the metabolic systems of tissues
- Lack of adequate nutrition into the cell (Sodium potassium pump stops working, so sodium builds up in the cell, and water follows
What are the the clinical features of hypercalcemia
- GI symptoms: anorexia, nausea, vomiting, and constipation
- Neuro symptoms: weakness, fatigue, confusion
- Vomiting causes a volume contraction, furthering the issue of hypercalcemia
What are the treatments for hyperphosphatemia
- Saline diuresis (acute condition)
- Reduced dietary intake (end stage kidney disease)
With regards to serum phosphate levels, what is the result of increased PTH
Decreased due to increased renal excretion with increased calcium reabsorption
What is a common cause of hypophosphatemia and what is the mechanism
Refeeding hypophophosphatemia (feeding a starving person) *Because feeding a once starving person, the increased glucose causes phosphate to be pulled into the cell, lowering the ECF levels
What are the 3 ways that calcitonin lowers blood [Calcium]
- Inhibits Calcium from the intestine
- Inhibits osteoclast activity in bones
- Inhibits renal tubular cell reabsorption of Calcium (increases calcium)
How is calcitriol created
Stimulated by PTH
With regards to serum phosphate levels, what is the result of increased vitamin D
Increased due to increased intestinal absorption
What are the symptoms of hypocalcemia seen in the CNS
- Irritabilty, depression
- coma
- Tonic clonic seizures
- papilledema
What are the clinical signs of hypophosphatemia
- only appears when there is total body phosphate depletion
- Muscular abnormalities with respiratory failure and failing diaphragmatic function
- Hemolysis and platelet dysfunction
- Chronic hypophosphatemia leading to rickets and osteomalacia
What are the general treatments for patients with hypophosphatemia
Administration of phosphates (whether oral or IV depending on the severity)
What regulates the levels of phosphate reabsorption via NaPi2
PTH and FGF23
What is the result of increased amounts of Klotho
An enzyme that breaks down complex carbs, and serves to stimulate and active the TRPV5 to increase calcium reabsorption
What is the role of calcium levels in the activity of nerves, smooth, cardiac, and skeletal muscle
The threshold is determined by the level of free calcium
What are the general targets of treatment for acute hypercalcemia
- Increasing calcium excretion
- decreasing resorption of calcium from bone
- Decreasing absorption of intestinal calcium
What is the method of regulation and reabsorption of calcium in the distal tubule
- Active transport
- Renal epithelial Ca channel (TRPV5)
- Calbindin, regulated by calcitriol
What is the treatment for acute hypercalcemia
- ECF volume replacement with .9% saline
- Furosemide
- bisphosphonates if not responding to diuretics or is a malignancy
Which conditions commonly are present in patients with hypophosphatemia
-Hypokalemic and hypomagnesemic
What calcium values should be used if the albumin levels are abnormal in a patient
Should be based on the ionized calcium levels
What is the result on GFR in the cause of using an ACE inhibator
Decreased angiotensin 2 release, resulting in the loss of resistance in the efferent arterioles, resulting in vasodilation and the decrease in GFR and increased creatinine levels
What are the common patients seen to have hypomagnesium and what are the common causes
60% of ICU patients
- Decreased nutrition
- Diuretics
- Decreased albumin
- Aminoglucosides
- Decreased reabsoprtion (due to PPI)
Where is the majority of magnesium reabsorbed and its mechanism
Thick ascending limp via transepithelial gradient from the potassium/sodium/chloride transporter there
*This is nice that PCT is not the major site
What are the clinical features of hyperphosphatemia
- Usually seen as the result on concurrent hypocalcemia
- Tissue ischemia or calciphylaxis (vascular calcification)
- Chronic hyperphosphatemia cause lead to renal osteodystrophy
What are the common things reabsorbed in the early proximal tubule
- Sodium
- Glucose
- Amino Acids
What is the effect of hypoalbuminemia on calcium levels
Decreases the total serum calcium levels, but does not affect the level of ionized calcium levels
Which malignancy is classically a cause of SIADH
-Small cell lung cancer (OAT cell) that produces mass amounts of ADH
Which drugs will cause ECF potassium to be places in tissue stores
Insulin
Epinephrine
Aldosterone
What is the effect of changes to albumin with regards to calcium
Changes in albumin will result in a change in the total calcium, but not the ionized calcium levels
Of the 49% of the magnesium in the ICF, what percentage is ionized and what is its main function
-10% is ionized and used as a cofactor in biochemical processes such as ATPases and ion channels
What is the classical EKG finding with hyperkalemia
High T wave
What is the result of carbohydrate of glucose infusion on the phosphate serum level
Decreases it
What is the only hormone regulator of magnesium
EGF
What are the symptoms of hypocalcemia seen in the dermatological and ocular system
- Dry skin, course har, brittle nails
- Cataracts
What is the effect of increased levels of calcitriol
- Promotes absorption of calcium in GI tract
- Increased renal tubular reabsorption (reuptake)
- Stimulates release of calcium from bone
- Overall, causes the increased [Ca] plasma
What are the general factors that could cause hypercalcemia
- Primary hyperPTH
- Malignancy
- immobilization Syndrome
- Vitamin D intoxication
- thiazides
What is the effect of decreased calcium levels on the threshold
Decreases the threshold
With regards to serum phosphate levels, what is the result of increased FGF-23
Decreased due to increased renal excretion
What is the mechanism of GFR changes seen during increased sodium increase
Increased sodium leads to increased ECF resulting in:
- Decreased sympathetics —> dilation of afferent arterioles and increased GFR
- Increased ANP —> Increased GFR
- Decreased renin —> Increased GFR
- Decreased angiotensin and ADH—> increased excretion of Na and H2O
With the production of PTH, what are the serum level values and their mechanisms
- Increased plasma [Ca] (increased calcium reabsorption in the distal nephron
- Decreased plasma [PO4] (inhibits PO4 reabsorption in the proximal tubule)
- Increased ionized [Ca] (enhanced bone release of calcium)
Of the 1% if the magnesium that is in the ECF, what percent is ionized
60%
What is the treatment of hypermagnesemia in patients with end stage renal disease
Dialysis
What are the symptoms of hypocalcemia seen in the Neuromuscular system
- Tetany, carpopedal spasms
- Chvostek’s sign
- peresthesias, numbness
- Muscle twitching or cramping
What is the role of vitamins D in the kidneys with regards to calcium regulation in the distal convoluted tubule
Regulates the levels of calbindin-D28K and TRPV5 expression
What is the treatment of hypermagnesemia in patients with normal renal function
Stop administering of Mg and let normal renal function do the job, or add a loop diuretic
What are the effects of calcitonin on the levels of blood [Calcium]
Lowers the amount of blood [Calcium]
What is the mechanism of reabsorption of magnesium in the PCT
Paracellular
What are the effects of calcitriol and PTH on calcium levels
Increase the amount of blood [Calcium]
What is the treatment for level 3 hyponatremia
Hypertonic NaCl and vaptans with Fluid Restriction
What is the treatment for level 2 hyponatremia
Moderate symptoms, given a vaptan or hypertonic NaCl
With regards to serum phosphate levels, what is the result of increased insulin
Decreased due to phosphate pulled into cells
What is the classically EKG finding in hypokalemia
High U wave, low T wave
What is the physiological responses to hypercalcemia
- Decreased PTH —> decreased resorption (breakdown) from bone
- Decreased vitamin D—> Increased calcium excretion, Decreased intestinal calcium absorption
What are the symptoms of hypocalcemia seen in the CCV
- lengthened QT
- Hyoptension
- CHF
- Dysrhythmias
How is the majority of excess phosphate excreted
In the urine (910 mg/day)
When is hypermagnesia usually seen
- very rarely
- End stage renal disease
- Large epsom salt intake
- Magnesium infusion (usually in preeclampsia women)
What is the mechanism of action in the kidneys when increased RBF and GFR are detected
- Increased RBF and GFR
- increased delivery to JG apparatus and macula densa
- Increased resistance to the afferent arteriole
- Leads to decrease in the RBF and GFR
What portion of the calcium is regulated
Only the free, ionized calcium in the ECF is regulated
What are the clinical signs of hypomagnesium
Usually follow the symptoms of hypocalcemia
*Because usually associated with hypocalcemia and hypokalemia
Where are the locations of magnesium storage
- 50 in the bone
- 49 in the cell (ICF)
