Flashcards in Acid-base balance II: Whole body acid-base balance Deck (40)
what is the first priority if normal acid-base balance is disrupted?
restore pH to 7.4 as soon as possible- compensation
what is compensation?
the restoration of pH irrespective of what happens to [HCO3-]p and PCO2
what is correction?
restoration of pH and [HCO3-]p and PCO2 to normal
what are the 2 classification of disturbances or respiratory origin?
-respiartory acidosis (plasma pH falls)
(plasma pH rises)
what are the 2 classification of disturbances or non-respiratory origin?
(plasma pH falls)
(plasma pH rises)
what is immediate buffering of a pH change?
Immediate dilution of the acid or base in ECF
Blood buffers (i.e. Hb, HCO3-. Acidosis would reduce [HCO3-]p)
Buffers in the ECF (particularly HCO3-)
what happens once buffer stores are quickly depleted?
kidney has to rectify stores
what can measure pH and Pco2?
what is pH proportional to?
what diagram can we plott variables on?
what are the normal values in the davenport diagram?
plasma pH- 7.4
[HCO3-]p - 25mmol/l
what is respiratory acidosis?
retention of CO2 by the body e.g. chronic bronchitis
how do respiratory disorders generate acidosis?
Co2 retention drives equilibrium to the right
what happens during respiratory acidosis?
-Both [H+]p and [HCO3-]p rise
-The increased [H+]p results in acidosis
(remember that pH is only a measure of free [H+])
how is uncompensated respiratory acidosis indicated?
pH < 7.35 and PCO2 > 45 mmHg
where does respiratory acidosis sit on the davenport diagram?
what system compensates for respiratory acidosis?
since respiratory system is the cause- renal system must compensate
how does the renal system compensate for respiratory acidosis?
-H+ secretion is stimulated
-All filtered HCO3- is reabsorbed (i.e. no HCO3- excretion)
-H+ continues to be secreted and generates titratable acid (TA) and NH4+
-Acid is excreted and “new” HCO3- is added to the blood
why does the [HCO3-] rise in respiratory acidosis?
(a) as a result of the disorder (b) as a result of the renal compensation
what does correction of respiratory acidosis require?
requires lowering PCO2 by restoration of normal ventilation
what is respiratory alkalosis?
Excessive removal of CO2 by the body e.g. hyperventilation
How do these disruptions to ventilation cause respiratory alkalosis?
-Excessive CO2 removal drives equilibrium to the left and so Both [H+]p and [HCO3-]p fall
where does respiratory alkalosis sit on the davenport diagram?
How does the renal system compensate for respiratory alkalosis?
-The H+ secretion is insufficient to reabsorb the filtered HCO3-, even though the load is lower than normal
- HCO3- is excreted and urine is alkaline
-No titratable acid (TA) and NH4+ is formed, so no “new” HCO3- is generated
what is the overall compensation and correction by the renal system for respiratory alkalosis?
-Renal compensation further lowers [HCO3-]p
-Correction requires the restoration of normal ventilation
what is metabolic acidosis?
Excess H+ from any source other than CO2 e.g. ingestion of acids
how is Uncompensated respiratory alkalosis is indicated?
pH > 7.45 and PCO2 < 35 mmHg
how does metabolic acidosis effect [HCO3-] p?
[HCO3-]p is depleted as a result of buffering excess H+ or loss of HCO3- from the body
how is uncompensated metabolic acidosis indicated?
pH < 7.35, [HCO3-]p is low