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?
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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-)
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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
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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?
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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)