ABGs Flashcards
ABGs measure arterial (5 things)
pH
pO2
pCO2
bicarb
O2 sat
primary buffer system of the body
carbonic acid/bicarbonate system
in the carbonic acid/bicarbonate system, CO2 is regulated by the
lungs
in the carbonic acid/bicarbonate system, bicarb is regulated by the
kidneys
equation of life
HCO3 + H+ → ← H2CO3 →← CO2 + H2O
lungs release CO2 → increased blood CO2 =
respiratory acidosis
decreased blood CO2 levels =
respiratory alkalosis
kidneys increase blood bicarb =
metabolic alkalosis
kidneys decrease blood bicarb =
metabolic acidosis
ABGs are ordered for
critically ill pt
ventilate pt
normal pH
7.36-7.44
normal pCO2
35-45 mmHg
pCO2 gives you information about
lung function → CO2 excretion
elevated pCO2 implies
inadequate ventilation
normal blood carriage of pCO2 in plasma
10%
what % of pCO2 is in RBC
90%
where does the equation of life occur
kidneys
RBC
lungs
mainly kidneys and RBC
which has higher pCO2 - arteries or veins
veins
venous blood takes the CO2 to the periphery
normal pO2 range
80-100 mmHg
levels < __ suggest significant reduction in hgb sat and impaired O2 delivery
60
is pO2 lower in veinous or arterial blood
lower in venous blood
arteries carry it to periphery
normal bicarb levels
22-26 mEq/L
what is CO2 on an electrolyte panel measuring
venous bicarb
on a lyte panel, __ and
__ mirror one another
venous CO2 and bicarb
negative base excess =
metabolic acidosis
positive base excess =
metabolic alkalosis or compensation to respiratory acidosis
respiratory alkalosis can occur with
hyperventilation
anxiety
overventilation of patients on ventilators
pH in respiratory alkalosis will be
high
pCO2 in respiratory alkalosis will be
low
respiratory acidosis occurs with what conditions
COPD
asthma
drug overdose
PNA
hypoventilation
pH in respiratory acidosis
low
pCO2 in respiratory acidosis
high
what conditions cause metabolic alkalosis
loss of gastric acid → vomiting
diuretic usage
pH in metabolic alkalosis
high
bicarb in metabolic alkalosis
high
metabolic acidosis occurs with
DKA
starvation
alcoholics
lactic acidosis
pH in metabolic acidosis
low
HCO3 in metabolic acidosis
low
MUDPILES
causes of metabolic acidosis
methanol poisoning
uremia
DKA
propylene glycol
INH or Iron
lactic acid
ethanol
salicylates
electrolyte panel includes
Na
K
Cl
CO2
Na+ nl
135-145 meq/l
K+ normal
3.5-4.5 meq/l
Cl nl
98-106 meq/l
CO2 nl
23-30 meq/l
mirrors bicarb on lytes panel
metabolic alkalosis and acidosis will cause _ changes
bc water and sodium are regulated by the __
electrolyte
kidney
anion gap is the
difference btw cations and anions in extracellular space
nl ion gap
3-11 mEq/L
anion gap evaluates
metabolic acidosis
anion gap equation
Na-(Cl+CO2)
increased anion gap indicates
increased negatively charged weak acids
steps to interpreting ABGs
- look at pH → acidosis or alkalosis?
- check the CO2 → respiratory indicator
- check the HCO3 → metabolic indicator
- what is primary disorder → resp or metabolic
CO2 <35 =
respiratory alkalosis
CO2 > 45 =
respiratory acidosis
HCO3 < 22 =
metabolic acidosis
HCO3 > 26 =
metabolic alkalosis
if pH is low then look to see if CO2 or HCO3 is acidosis →
high CO2 → respiratory acidosis
low bicarb → metabolic acidosis
if pH is high then look to see if CO2 or HCO3 is alkalosis →
low CO2 → respiratory alkalosis
high bicarb → metabolic alkalosis
Interpreting ABGs
the value that matches the pH indicates
the primary disorder
compensation refers to when
the respiratory and renal systems compensate for one another
kidneys compensate __ than the lungs
slower
in compensation, if the nonprimary system is in the normal range that means that
compensation is NOT happening
most common places to obtain ABGs
brachial and radial arteries
the Allen test is used for
evaluation of collateral circulation of radial artery BEFORE you do a radial stick for ABG
pt breathing in respiratory alkalosis
fast breathing
in order for true compensation to occur, the __ has to be normal
pH
is this compensation:
acidodic: pH
alkalotic: CO2
bicarb: acidodic
this is metabolic acidosis, but w.o compensation bc the pH is not normal
this is attempted compensation
iSAT uses __ blood instead of arterial blood
capillary