acid base control Flashcards
what buffers control acid base balance
haemoglobin
bicarbonate
carbonic acid
proteins
what is normal pH
7.35-7.45
what is normal O2 pp
12-13 kPa
what is normal pCO2
4.5 – 5.6 kPa
what is normal bicarbonate concentration
22 – 26 mmol/l
what is standard bicarbonate
used to indicate metabolic acid base balance
assumes standard temperature and CO2 pp
what is the first step of assessment of ABG
assess PO2 and oxygenation
what is a healthy P/F ratio
> 50
what P/F ratio indicates acute lung injury
> 40
what P/F ratio indicates ARDS
26.6
if the pH and pCO2 are changing in different directions what does that indicate
respiratory problem
if the pH and pCO2 are changing in the same direction what does that indicate
metabolic problem
if pCO2 and bicarb are moving in the same direction what does that indicate
compensation is occuring
what is the anion gap
the sum of routinely measured cations in
venous blood minus routinely measured
anions
([Na+] + [K+])- ([Cl-] +[HCO3-])
what is normal pH
7.35-7.45
what is normal O2 pp
12-13 kPa
what is normal pCO2
4.5 – 5.6 kPa
what conditions will cause lactic acidosis
hypoperfusion of the whole body or a part
increased anaerobic metabolism producing increased lactic acid
Severe acute hypoxia Severe convulsions (resp arrest) Strenuous exercise (dehydration)
what is standard bicarbonate
used to indicate metabolic acid base balance
assumes standard temperature and CO2 pp
what is the first step of assessment of ABG
assess PO2 and oxygenation
if the pH and pCO2 are changing in different directions what does that indicate
respiratory problem
if the pH and pCO2 are changing in the same direction what does that indicate
metabolic problem
if pCO2 and bicarb are moving in the same direction what does that indicate
compensation is occuring
if pCO2 and bicarb are moving in the different directions what does that indicate
mixed problem
what anions are measured
protein, phosphate, Cl, sulphate bicarbonate
what cations are measured
Ca, Mg, K, Na
what does an increased anion gap indicate
metabolic acidosis -
what is the normal anion gap
16
what conditions will cause lactic acidosis
hypoperfusion of the whole body or a part
how is lactic acid broken down
in the liver using oxygen
how will anions change in lactic acidosis
same cations
increase in unmeasured anions
decrease in bicarb
what conditions can cause ketoacidosis
decreased insulin
diatbetes
alcoholic ketoacidosis
starvation
what substances might be ingested which increase the anion gap
methanol
ethylene glycol
what is Renal tubular acidosis
accumulation of acid due to failure of kidneys to acidify the urine
normal anion gap
how does the anion gap change in renal failure
increase
what conditions involve acidosis but no anion gap
diarrhoea
renal tubular acidosis
how is the ionogram changed with metabolic acidosis but an unchanged anion gap
decreased bicarbonate only due to it being combined with H+
how does the kidney correct metabolic acidosis
secretes more acid into the urine
makes new bicarbonate
what is Kussmaul respiration
laboured, deep rapid pattern of breathing
what is the most common cause of metabolic alkalosis
loss of H+ ions from the stomach or kidney
e.g. pyloric stenosis
what diuretics can cause loss of H+ ions
furosemide
thiazide
what can cause loss of H+ ions in babies
pyloric stenosis
what to situations lead to metabolic alkalosis
an initiating process and a maintaining process
how is alkalosis maintained
kidneys ability to excrete excess bicarb is impaired
what is chloride depletion
if chloride is low in the kidneys then bicarb must be reabsorbed leading to alkalosis
