acid base 1 Flashcards
what defines acidemia
pH < 7.35
what defines alkalemia
pH > 7.45
difference between acidemia and acidosis
acidemia = state of blood pH acidosis = pathological processes that change pH
define a buffer
Minimises pH changes due to addition or removal of H+ (temporarily)
what is Henderson-hasselbach equation
pH = 6.74 + log (HCO3- / pCO2)
is determined by ratio between HCO3- and pCO2 as pKa is constant
describe respiratory disturbances
respiratory acidosis
- CO2 retention
- e.g. pCO2 = 9
respiratory alkalosis
- hyperventilation
- e.g. pCO2 = 3
describe metabolic disturbances
metabolic acidosis = low bicarbonate
metabolic alkalosis = high bicarbonate
name urinary buffers
phosphoric acid
ammonium ions
causes of metabolic acidosis
- lactic acidosis
- diabetic ketoacidosis
- renal failure
- renal tubular acidosis
- severe diarrhoea, ilieostomy
what is the role of the kidneys in acid-base balance
- bicarbonate reabsorption
- ‘new’ bicarbonate generation
- H+ secretion in distal nephron (distal tubule & CD)
- via ammonia and phosphate
describe the role of acetazolamide
- is a carbonic anhydrase inhibitor
- causes metabolic acidosis
- used to counteract alkalosis due to hyperventilation
- inhibits reabsorption and regeneration of HCO3-
what plays a key role in urinary generation (not reabsorption)
urinary buffers
describe the role of ammonium in the nephron
- ammonium generated from glutamine in PT cells and secreted into the lumen (produces 2x HCO3-)
- most reabsorbed in TAL
- CD = diffusion trapping
describe the response of the kidneys to acidosis
- increased HCO3- & H+ transport along the nephron
- increased ammoniagenesis
- increased availability of urinary buffers
(=more acid excretion)
