Valley Renal/Electrolytes/Acid-Base Flashcards
What region of the kidney is most vulnerable to ischemia?
The inner stripe of the outer medulla.
When glucose is filtered into the renal tubule, what location is it normally reabsorbed from?
proximal tubule
Where is vasopressin (ADH) synthesized and what stimulates its release?
vasopressin is synthesized in the hypothalamus (paraventricular and supraoptic nuclei)
increased osmolality of extracellular fluid stimulates the posterior pituitary (where ADH is stored) to release ADH
What is urine volume and osmolality when antidiuretic hormone release is inhibited?
When ADH release is inhibited, the urine osmolality is low, and the volume excreted is large.
How does aldosterone affect sodium and potassium excretion?
aldosterone secretion causes a decrease in sodium excretion and an increase in potassium excretion
What hormone controls extracellular fluid volume, and what hormone controls extracellular sodium concentration?
ADH controls the extracellular fluid volume.
Aldosterone controls the extracellular sodium concentration.
What diuretic works by inhibiting the Na+ – K+ – Cl- symporter?
The sodium-potassium-chloride symporter, a channel in the loop of Henle, is inhibited by a loop diuretic.
Furosemide is a loop diuretic.
Spironolactone acts primarily on what segment of renal tubule?
Spironolactone - a potassium-sparing diuretic works at the collecting duct.
What test helps distinguish prerenal from renal failure?
Fractional excretion of filtered sodium. (FEna) - the amount of sodium that is filtered through glomerulus and then secreted/excreted in the urine.
A LOW FEna is indicative of pre-renal failure. Because there is low flow through the tubule, there is adequate time for a high amount of sodium to be reabsorbed.
A HIGH FEna is indicative of renal failure. In acute renal failure, the renal tubule reabsorbs sodium poorly, therefore a large amount of sodium appears in the urine.
The chronic renal failure patient has a tendency for increased bleeding, in part because of defective…?
defective von Willebrand’s factor.
What electrolyte disturbance is not seen in the chronic kidney disease patient -
A. Hyperkalemia
B. Hypercalcemia
C. Hypermagnesemia
D. Hyperphosphatemia
Hypercalcemia is NOT seen in kidney disease.
Hypocalcemia is seen as a reciprocal reaction d/t hyperphosphatemia. Also, because of the decreased renal production of the active form of vitamin D, there is diminished intestinal absorption of calcium.
Blood pressure in the individual at rest is controlled primarily by?
Renin
Which combination of acute electrolyte abnormalities will most stabilize nerve, skeletal muscle, and cardiac ventricular muscles?
Hypokalemia and Hypercalcemia
Hypokalemia hyper polarizes the resting membrane potential.
Hypercalcemia depolarizes (makes less negative) the threshold potential.
When threshold potential is further away from the resting membrane potential, it takes a larger stimulus in order to produce an action potential.
A clinically appropriate K+ concentration for cardioplegia solution is?
Cardioplegic solution has a K+ range from 15-40 mEq/L.
Cardioplegia solution, the resting membrane potential moves past the threshold potential, the sodium gates snap open (one action potential is elicited), then snap shut in the inactive state. No more action potentials can be elicited, so the heart remains electrically arrested until a normal K+ concentration is restored.
Each of the following interventions drive K+ into the cells EXCEPT:
A. administering sodium bicarbonate
B. administering calcium gluconate
C. hyperventilating the lungs
D. administering insulin-glucose Administering calcium gluconate.
Calcium is the fastest INTERVENTION that will help prevent fatal arrhythmias by increasing the threshold potential. It does NOT fix the hyperkalemia.
Hyperventilation can produce signs and symptoms of what electrolyte disturbance?
Hypocalcemia.
When the body is alkalotic (respiratory in this case), the H+ that is combined with protein detaches in order to buffer the alkalosis. This leaves the protein free to bind with the calcium. The total amount of calcium in the body is not decreased, but the amount of free calcium is decreased –> a functional hypocalcemia that can lead to tetany and numbness of the fingertips and lips.
The patient with a pH of 7.30, PaCO2 of 25 mm-Hg, and HCO3- of 12 has what single acid-base disturbance?
Partially compensated metabolic acidosis
The kidney’s role in maintaining acid-base balance includes…?
Reabsorption of bicarbonate ions
Excretion of hydrogen ions
Remember: with every H+ excreted, there is one Na+ and one HCO2- reabsorbed.
(H+) + (HCO3-) –> H2CO3 –> H2O + CO2
the H2O + CO2 moves from tubular lumen into tubular cell, and then
with the catalyst carbonic anhydrase:
H2O + CO2 –> H2CO3 –> H + HCO3-
HCO3- is reabsorbed, and the H+ is excreted back into the lumen to be available for another HCO3- reabsorption cycle (or combine with ammonia to be excreted)
NH3 (ammonia) + H –> NH4+ (ammonium)
The threshold potential of cell membrane excitability is most directly controlled by what ion?
calcium
Which of the following is an important stimulus for aldosterone release from the adrenal cortex?
High potassium levels
Can signs and symptoms of hypocalcemia be elicited when the patient hyperventilates?
Yes. Hyperventilation causes a respiratory alkalosis. Ionized calcium decreases, thus eliciting signs and symptoms of hypocalcemia.
This is why lips and fingertips can tingle when one hyperventilates.
Signs and symptoms of what two electrolyte abnormalities may be manifested in the hyperventilating patient?
Signs and symptoms of hypokalemia and hypocalcemia may be manifested in the patient who is hyperventilating. Remember, however, that with hyperventilation there may develop a true hypokalemia but a true hypocalcemia does not develop (total calcium, ionized plus non-ionized, does not change). Signs and symptoms of hypocalcemia may develop during hyperventilation because of the decrease in free ionized calcium.
What equation is used to determine the pH?
Henderson-Hasselbalch equation
What is the normal range of pH? HCO3-? PaCO2?
pH: 7.35-7.45
PaCO2: 35-45 mm-Hg
HCO3-: 22-27 mEq/L
Can a respiratory acid/base disturbance be completely compensated? A metabolic acid/base disturbance?
A respiratory acid/base disturbance CAN be completely compensated. IF an acid-base disturbance is COMPENSATED, it MUST be a respiratory disturbance.
A metabolic acid/base disturbance CANNOT be completely compensated.
