K+ diseases Flashcards
normal urine K+
45-112 mEq
K+ moves out of ICF to ECF
in presence of acidemia and hyperosmolarity
Factors affect Internal K+ balance
Plasma K+ highest –> lowest
non-anion gap metabolic acidosis
anion gap metab acidosis
alkalemia
effect of alkalosis on K+ secretion
1) incr K+ entry into cells from ECF
2) incr apical membrane K+ permeability due to less H+ blocking K+ channels
–> hypokalemia
Effect of aldosterone in cells
1) activ of apical Na channels (incr Na channel synthesis)
2) incr expression of basolateral Na/K
3) equal affinitiy betwen aldosterone and glucocorticods (cortisol)
Normal distal tubule function
1) normal tubular epith function
2) aldosterone
3) urine or tubular flow rate
4) urinary excretion of anions = drags along K+ charge
in absence of aldosterone, effect on total body K+ and plasma K+
with high plasma K+ effect on aldosterone
incr both
incr aldosterone for K+ secretion
GI potassium excretion vs. skin K+ excretion
GI = diarrhea incr fecal K+ loss (laxative esp)
Skin = with large sweat, high K+ loss, sweat under control fo aldsterone
K+ adaptation compared to sodium adaptation in timing
K+ adaptation is slow to turn on or off
in chronic renal failure with same dietary K+ intake, effect on kidney
each nephron has to incr K+ excretion to maintain external K+ balance
hyperkalemia problem in acute renal failure and severely low
Approach to hypokalemia
1) is there transcellular shift?
- alkalemia, excess insulin, excess beta agonist (isoproteronol), thyrotoxicosis
2) is there low K+ intake
3) is there GI loss of K+ (diarrhea, vomiting)
4) is there XS renal loss (diuretics)
treatment of hypokalmeia
1) acute = cardiac arrhythmia or paralysis = IV K+
2) K+ sparing diuretics (spiro, triamterene, amiloride)
metabolic effects of hypokalemia
1) decr insulin, high glucose
2) poor growth
3) intracellular acidosis
4) decr renal NH3= cirrhosis or encpahlopahty
cardiovascular effect of hypokalemia
U waves and flattened T waves
neuromuscular effect of hypokalemia
muscle weakness, paralysis, rhabomyolysis
renal effect of hypokalemia
1) incr thirst
2) polyuria
3) proteinuria
4) decr GFR
cardiac effect of hyperkalemia
1) peaked T waves
2) prolonged QRS and PR interval
3) ventricular fibrillation, cardiac arrest
EKG CHANGE WITH HYPERKALEMIA = EMERGENCY
Neuromuscular effect of hyperkalemia
due to depolarization
weakness
paralysis
Approach to hyperkalemia
1) if K+ > 6.0 an EKG should be performed immediately
2) is there transcellular shift
- acidemia, massive digitalis, adrenergic block, hyperosmolar state
3) is there decr renal K+ excretion
- GFR 40
- dietary intake > 300
KCL or XS dietary K+ intake
treatment of hyperkalemia
reversible depolarization
calcium infusion
treatment of hyperkalemia
shift K+ into cells
insulin
beta agonist
bicarb infusion
remove K+ from body
Kayexelate
diuretics
hemodialysis
45 y/o woman with 3 day history of n/v/anorexia
stopped insulin
on beta blocker for angina
normal vitals K+ = 6.0 WBC = 40,000 positive ketones pH = 7.10
what factors producing hyperkalemia
1) insulin deficiency
2) acidosis
3) beta blockers
45 y/o woman with 3 day history of n/v/anorexia
stopped insulin
on beta blocker for angina
normal vitals K+ = 6.0 WBC = 40,000 positive ketones pH = 7.10
what does she have?
diabetic with renal insufficiency = type IV RTA
possibly pseudohyperkalemia (WBC = 40k)
