Fluids and Electrolytes Flashcards
which equation tells you how the serum sodium concentration derives from total body sodium
use the equation [Na+] = (Exchangeable Na+ + Exchangeable K+)/TBW
what is the relationship between the serum concentration of sodium and total body water?
- 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
what is the significance between sodium and chloride serum concentration?
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.
the way potassium is excreted is thru the kidneys. Which external balances depends on renal excretion?
- GFR
- distal delivery of sodium ( if sodium is not delivered to the distal tubule potassium will not escape
- aldosterone
what are the internal balances of potassium?
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)
what are the clinical manifestations of hypokalemia?
arrythmia, muscle weakness, u wave on EKG
what do you see with potassium in lower GI losses
you get metabolic acidosis
how much potassium is in GI fluids? and how does that contribute to renal wasting
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
transtubullar potassium gradient
is useful because it eliminates dilution errors
it takes into account urine osmolality
what is the best method of giving potassium in emergent situations?
oral preferred if IV you need to monitor the EKG of the patient
what can lead to hyperkalemia?
- first it is always related to failure of the renal system
- abonormal internal distribution
what can be used to put potassium into the cell?
- elevating the pH (puts potassium into the cell)
- insulin and glucose
- beta agonists by nasal
what are the treatments (he doesn’t talk about it) for hyperkalemia?
-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
what is used as a treatment to antagonize electrical toxicity?
-IV calcium
what is the significance of vitamin D and renal function
with renal dysfunction patients cannot synthesize the active form, 1-25 dihydrochoecalciferol
*also we give vitamin D to lower PTH
in the hospital setting vs overall which are the common causes of hypercalcemia?
- primary hyperparathyroidism (overall)
- cancer (hospital setting)
what are the causes of hypercalcemia?
- 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
what are some endocrine causes of hypercalcemia?
- addisons disease
- immobilization
- throtoxicosis
- pheochromocytoma
- acromegaly
- multiple endocrine neoplasia
- pagets disease with immobilization
- familial hypocalciuria hypercalcemia
- lithium and thiazides
what can you develop with hypocalcemia?
tetany- carpopedal spasm (trousseau sign)
- chvostek sign
- related to low ionized calcium
*can fracture you spine
what are the factors surroundign ionized calcium vs protein bound calcium?
- it is pH dependent
- alkalosis drives the protein bound calcium and can precipitate alkalosis
- acidosis can drive the ionized form of calcium
what are the consequences of low phosphate levels
cardiac failure
respiratory failure
hemolysis
what are the therapeutics in chronic renal failure to preserve the electrolytes? phosphate
low phosphorus diet phosphate binders vitamin d parathyroid surgery calcimimetic agents
what are the causes of hypomagnesemia?
- alcoholism
- starvation
- GI losses
- Renal tubular defects
1) fanconi syndrome
2) aminoglycosides
3) diuretics cisplatinum
what are the consequences of hypomagnesemia?
- 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
