Fluids and Electrolytes

Question 1

which equation tells you how the serum sodium concentration derives from total body sodium

Answer 1

use the equation [Na+] = (Exchangeable Na+ + Exchangeable K+)/TBW

Question 2

what is the relationship between the serum concentration of sodium and total body water?

Answer 2

• inversely proportional
• The serum sodium concentration tells you much more about water balance or osmolar balance and very little about sodium in the body per se

Question 3

what is the significance between sodium and chloride serum concentration?

Answer 3

they should increase or decrease proportionally. If it does not, then there is an acid-base disturbance

• high chloride disproportionate to sodium means that the patient either has respiratory alkalosis or metabolic acidosis.
• if the chloride is low disproportionate then respiratory acidosis and metabolic alkalosis.

Question 4

the way potassium is excreted is thru the kidneys. Which external balances depends on renal excretion?

Answer 4

• GFR
• distal delivery of sodium ( if sodium is not delivered to the distal tubule potassium will not escape
• aldosterone

Question 5

what are the internal balances of potassium?

Answer 5

ICF vs ECF

• insulin drives potassium into the cell
• adrenergic stimulation by catecholamines drive potassium into the cell
• a high tonicity in ECF will drive potassium out of the cell
• pH (inorganic acidosis i.e chloride) drives potassium out of the cell (inverse relationship with change in pH)

Question 6

what are the clinical manifestations of hypokalemia?

Answer 6

arrythmia, muscle weakness, u wave on EKG

Question 7

what do you see with potassium in lower GI losses

Answer 7

you get metabolic acidosis

Question 8

how much potassium is in GI fluids? and how does that contribute to renal wasting

Answer 8

there is not a lot in GI fluids but the loss can cause metabolic alkalosis which will lead to high excretion of potassium due to mineralcorticoids excess

Question 9

transtubullar potassium gradient

Answer 9

is useful because it eliminates dilution errors

it takes into account urine osmolality

Question 10

what is the best method of giving potassium in emergent situations?

Answer 10

oral preferred if IV you need to monitor the EKG of the patient

Question 11

what can lead to hyperkalemia?

Answer 11

• first it is always related to failure of the renal system

- abonormal internal distribution

Question 12

what can be used to put potassium into the cell?

Answer 12

• elevating the pH (puts potassium into the cell)
• insulin and glucose
• beta agonists by nasal

Question 13

what are the treatments (he doesn’t talk about it) for hyperkalemia?

Answer 13

-remove from the body
-redistribute to cell
-antagonize electrical toxicity(calcium)
talks about this tho
-IV dextrose and insulin(to lower K quickly)
-kayexalate by enema and mouth
-B agonist by nasal spray

Question 14

what is used as a treatment to antagonize electrical toxicity?

Answer 14

-IV calcium

Question 15

what is the significance of vitamin D and renal function

Answer 15

with renal dysfunction patients cannot synthesize the active form, 1-25 dihydrochoecalciferol

*also we give vitamin D to lower PTH

Question 16

in the hospital setting vs overall which are the common causes of hypercalcemia?

Answer 16

• primary hyperparathyroidism (overall)

- cancer (hospital setting)

Question 17

what are the causes of hypercalcemia?

Answer 17

• primary hyperparathyroidism
• vit A and D excess
• Sarcoid and other granulomatosis diseases (stimulate the conversion to the active form of vitamin D, calcitriol)
• milk alkali syndrome

Question 18

what are some endocrine causes of hypercalcemia?

Answer 18

• addisons disease
• immobilization
• throtoxicosis
• pheochromocytoma
• acromegaly
• multiple endocrine neoplasia
• pagets disease with immobilization
• familial hypocalciuria hypercalcemia
• lithium and thiazides

Question 19

what can you develop with hypocalcemia?

Answer 19

tetany- carpopedal spasm (trousseau sign)

• chvostek sign
• related to low ionized calcium

*can fracture you spine

Question 20

what are the factors surroundign ionized calcium vs protein bound calcium?

Answer 20

• it is pH dependent
• alkalosis drives the protein bound calcium and can precipitate alkalosis
• acidosis can drive the ionized form of calcium

Question 21

what are the consequences of low phosphate levels

Answer 21

cardiac failure
respiratory failure
hemolysis

Question 22

what are the therapeutics in chronic renal failure to preserve the electrolytes? phosphate

Answer 22

low phosphorus diet
phosphate binders
vitamin d
parathyroid surgery
calcimimetic agents

Question 23

what are the causes of hypomagnesemia?

Answer 23

• alcoholism
• starvation
• GI losses
• Renal tubular defects
  1) fanconi syndrome
  2) aminoglycosides
  3) diuretics cisplatinum

Question 24

what are the consequences of hypomagnesemia?

Answer 24

• if you do not fix the low magnesium then you can’t fix the tetany associated with hypocalcemia
• cannot repair hypokalemia or hypophospatemia without fixing magnesium

Question 25

what are the differential diagnosis with patients with hyperphosphatemia?

Answer 25

• renal failure
• hypoparathyroidism
• tumor lysis syndrome
• rhabdomyeolysis

Question 26

consequences of hypermagnesemia?

Answer 26

• usually occurs in presence of renal failure
• loss of deep tendon reflexes
• hypotension cardiac failure
• respiratory failure
• death

Question 27

what is the treatment of hypermagnesemia?

Answer 27

IV calcium