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Acid-base Metabolism

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What does low Cl- value mean? High Cl- value? Why?
metabolic alkalosis; HCO3- is increased. metabolic acidosis.
What are the 4 questions one must ask in evaluating acid-base disorders?
What are the pH and pCO2? Is an anion gap present? What is the Cl? Is an osmolar gap present?
What reacts with the H+ ions secreted into the tubular lumen?
Titratable acid and ammonia.
How much of the filtered HCO3- is reabsorbed in the PCT? DCT? Which area secretes H+ ions which react w/ titratable acid & ammonia? What enhances this?
80%. 15-20%. DCT.
Aldosterone secretion.
What is the relationship b/t volatile (CO2) and non-volatile acid (H2CO3)?
CO2 + H2O -- H2CO3 - H+ + HCO3
How does the kidney prevent bicarbonaturia as seen with RTA?
it reclaims bicarb from the glomerular filtrate
Why does the kidney excrete daily acid load?
To synthesis new bicarb to replace that consumed during metabolism
What is the fxn of luminal carbonic anhydrase?
It catalyzes the formation of H20 and CO2 from H2CO3 formed by secreted H+ by the PCT and filtered bicarb.
What happens to the CO2 and H20?
Diffuses into the luminal cells. H20 gets excreted in the urine.
What happens to the CO2 in the lumen?
It reforms H2CO3 with water which then dissociates into H+ and HCO3-.
What happens to the H+ ions and HCO3- created in the intracellular lumenal cells?
H+ diffuses into the tubular lumen while HCO3- is returned to the circulation.
What are the minimal data needed by the clinician for analysis?
serum electrolytes, ABG's, BUN and Cr, glucose, and measured serum osmoles
What test immediately tells you if the pt has acidemia or alkalemia?
the ABG pH.
What should be calculated with a set of electrolytes? What is the eqn?
Anion gap. AG = Na+ - (HCO3 + Cl-)
What accounts for a normal anion gap?
What would lead to a lower HCO-3? What is the result?
Negatively charged serum albumin. More acid in the serum. An increased anion gap.
What does an elevated anion gap signify?
Metabolic Acidosis.
How do you calculate serum osmoles?
(2xNa)+ (glucose/18) + (BUN/2.8)
What is the normal value for serum osmoles? A difference of more than 15mosm/L b/t calc and measured serum osmoles indicates what?
285-290. An osmolar gap (the presence of an unmeasured osmotically active substance)
What electrolyte may give hints as to other acid-base disturbances?
Cl-.
What 2 things control pH of bodily fluids
underlying disease states, and compensatory mechanisms
These 2 things pH?
HCO3- (metabolic) and pCO2 (respiratory)
Define "emia"
refers to the pH of the blood
Define "osis"
disease process generating high amt's of acid or alkali
What is the Henderson-Hasselbach eqn?
What does it define?
pH - 6.1 + log [(HCO2-)/(H2CO3)]
The relationship b/t pH, bicarb and carbonic acid.
What are the normal ABG values?
pH = 7.36-7.44, pCO2 = 38-42mmHg,
pO2 = 90-95 mmHg
What are the normal values for Na+, Cl-, K+, and HCO3-?
140, 100, 4.5, and 24
What are the body's 3 buffer systems?
chemical, respiratory (ventilation), and renal mechanisms (excretion)

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