Renal Control of Acid-Base Balance Flashcards by Sophia Barber

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

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What can happen in severe metabolic alkalosis?

increased binding of Ca to albumin –> hypocalcemia –> get symptoms of hypocalcemia

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What are causes of acute respiratory acidosis?

CANS

CNS depression

airway obstruction

neuromuscular disorders

severe pneumonia, embolism, edema

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Where is bicarbonate reabsorbed in the nephron?

85% PCT

10% TAL

4.9% CD

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What are the major symptoms letting you know there is renal tubular acidosis?

Acidemia + normal anion gap + normal serum creatinine + NO diarrhea

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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

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What is normal HCO3-?

22-26 mEq/L

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What are the causes of metabolic alkalosis?

CLEVER PD

Contraction

Licorice

Endocrine

Vomiting

Excess Alkali

refeeding alkalosis

Post-hypercapnia

Diuretics

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How do you know if a pH disturbance is respiratory?

CO2 and pH will change in opposite directions

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What is normal pCO2?

35-45 mm Hg

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What constitutes Chloride responsive metabolic alkalosis?

if you see metabolic alkalosis and urine chloride is <20 mEq/L

if > 20 mEq/L = chloride unresponsive

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What do alpha-intercalated cells do?

Secrete H+ into urine

Regenerate and reabsorb HCO3-

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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

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What is the henderson-hasselbach equation for blood?

pH = 6.1 + log([HCO3-]/[H2CO3])

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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

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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?

1. reabsorb/generate bicarb 2. 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