Renal Control of Acid-Base Balance Flashcards
How does an increase in aldosterone affect acid-base balance?
A decrease?
increase in aldosterone –> increase in H+ secretion in the collecting duct
decrease in aldosterone –> decrease in H+ secretion
What can happen in severe metabolic alkalosis?
increased binding of Ca to albumin –> hypocalcemia –> get symptoms of hypocalcemia
What are causes of acute respiratory acidosis?
CANS
CNS depression
airway obstruction
neuromuscular disorders
severe pneumonia, embolism, edema
Where is bicarbonate reabsorbed in the nephron?
85% PCT
10% TAL
4.9% CD
What are the major symptoms letting you know there is renal tubular acidosis?
Acidemia + normal anion gap + normal serum creatinine + NO diarrhea
What are the causes of High anion gap metabolic acidosis?
MUDPILERS
methanol
uremia
DKA/Alcoholic KA
Paraldehyde
Isoniazid
lactic acidosis
EtOH/Ethylene glycol
Rhabdo/Renal failure
Salicylates
What is normal HCO3-?
22-26 mEq/L
What are the causes of metabolic alkalosis?
CLEVER PD
Contraction
Licorice
Endocrine
Vomiting
Excess Alkali
refeeding alkalosis
Post-hypercapnia
Diuretics
How do you know if a pH disturbance is respiratory?
CO2 and pH will change in opposite directions
What is normal pCO2?
35-45 mm Hg
What constitutes Chloride responsive metabolic alkalosis?
if you see metabolic alkalosis and urine chloride is <20 mEq/L
if > 20 mEq/L = chloride unresponsive
What do alpha-intercalated cells do?
Secrete H+ into urine
Regenerate and reabsorb HCO3-
What occurs to K+ levels if alkalemia occurs?
ICF donates H+ and takes in K+ –> K+ goes into cells
plasma K+ levels decrease
K is lo
What is the henderson-hasselbach equation for blood?
pH = 6.1 + log([HCO3-]/[H2CO3])
Why is the body’s buffer system “open”?
bc HCO3- (base) is controlled by kidneys = slow with large capacity
CO2 (acid) is controlled by lungs = fast, with limited capacity
What do Beta intercalated cells do?
reabsorb H+ into the blood
secrete HCO3- into urine
What is type 4 RTA?
deficiency of aldosterone –> get hyperkalemia –> decreased NH3 synthesis by PT
What are causes of respiratory alkalosis?
CHAMPS
CNS disease
Hypoxia
Anxiety
Mechanical Ventilators
Progesterone
Salicylates/Sepsis
What is type 1 RTA?
H+ secretion by alpha-intercalated cells is somehow impaired
can’t make new HCO3- to reabsorb
How does an increase in angiotensin II affect acid-base balance?
A decrease?
increase in Angiotensin II –> increased Na-H exchange –> causes increased H+ secretion in PT and increased HCO3- resorption
Decrease –> decreased H+ secretion
What are fixed acids?
those that don’t turn into HCO3-
lactate
cysteine –> sulfate
phosphoprotein –> phosphate
What is normal blood pH?
7.35-7.45
What is ammonia synthesized from?
What is its function?
made from glutamine
acts as a buffer and is easily made = 2/3 of net acid excretion
How does hypokalemia affect acid-base balance in the nephron?
Hyperkalemia?
hypokalemia –> increased H+ secretion in PCT
hyperkalemia –> decreased H+ secretion in PCT
How do you know if a pH disturbance is metabolic?
If HCO3- and pH change in same direction
What is the major titratable acid used by the kidneys?
Phosphate
What is the path of ammonia in the nephron?
made from glutamine in the PCT –> secreted into lumen –> in TAL, transported by NKCC in place of K+ into the IF –> diffuses into CD lumen = ion trapped and used as a buffer for H+, excreted in urine
What are the 2 major goals of renal acid-base regulation?
- reabsorb/generate bicarb
- excrete H+
What are volatile acids?
those that contain CO2 –> HCO3-
from anaerobic metabolism of glucose and fat
Why must extracellular pH remain at 7.4?
pH changes alter protein structure/function
need stable pH for them to work properly
What does your [HCO3-]/[H2CO3] value need to be to make HH equation = normal pH?
20
(bc 6.1 + log(20) = 7.4)
What occurs to K levels if acidemia occurs?
ICF takes H+ –> K+ transported out of the cell
Plasma K levels increase
What are causes of chronic respiratory acidosis?
COPD
anything chronic that leads to impaired ventilation
What are the causes of non-anion gap acidosis?
HARDUPS
Hyperalimentation
Acetazolamide
Renal Tubular Acidosis
Diarrhea
Uretero-Pelvic Shunt
Post-Hypocapnia
Spironolactone
What is type 2 RTA?
HCO3- reabsorption is impaired in PT
see hypokalemia
What does the pKa of a buffer represent conceptually?
pH at which the buffer has absorbed half of the H+ it can hold
