Chemical Pathology - Acid Base Flashcards
how are H+ ions excreted?
H+ is buffered by HCO3-
maintain normal homeostasis, kidney needs to excrete H+ ions and regenerate bicarbonate
how is bicarbonate regenerated?
through production of carbonic acid
HCO3- then reabsorbed back into blood
how do H+ ions get across the membrane?
Na+/H+ exchange
what controls respiration?
chemoreceptors in hypothalamic respiratory centre
inc. in CO2 stimulates respiration
what is the buffer in RBCs?
Hb
CO2 taken up by RBCs, buffered by Hb
so controls concentration of H+ ions
what is the primary abnormality in metabolic acidosis?
increased H+
decreased pH
decreased bicarbonate
what are the 3 broad causes of metabolic acidosis?
- increased H+ production e.g. DKA
- decreased H+ excretion e.g. renal tubular acidosis
- bicarbonate loss e.g. intestinal fistula
what is the primary abnormality in respiratory acidosis?
increased CO2 production
this causes increased H+
slight increased in HCO3
What are the 3 broad causes of respiratory acidosis?
- dec ventilation
- poor lung perfusion
- impaired gas exchange
what is the compensation mechanism of respiratory acidosis? time frame?
increased renal excretion of H+ and generation of HCO3-
H+ may return to near normal
CO2 and bicarbonate remain elevated
FEW DAYS
what is the primary abnormality in metabolic alkalosis?
decreased H+
increased pH
increased HCO3
what are the 3 broad causes of metabolic alkalosis?
- H+ loss (e.g. pyloric stenosis)
- hypokalaemia (cannot excrete H+)
- ingestion of bicarbonate
what is the compensation of metabolic alkalosis?
- inhibit respiratory centre (get a rise in pCO2)
- H+ may then return to normal
what is the cause of respiratory alkalosis?
hyperventilation
- voluntary
- artificial ventilation
- stimulation of respiratory centre
what happens biochemically in chronic respiratory alkalosis?
- decreased renal excretion of H+
- less bicarbonate generation
- H+ may return to normal
- pCO2 and bicarbonate will remain low
