Acid base disorders

• pH: 7.35 – 7.45

• PaCO2: 4.7 – 6.0 kPa || 35.2 – 45 mmHg

• PaO2: 11 – 13 kPa || 82.5 – 97.5 mmHg

• HCO3–: 22 – 26 mEq/L

• Base excess (BE): -2 to +2 mmol/L




Importance of context Pts clinical condition
A normal Pa 02 in a pt on
high flow 02 Abnormal As
would expect kPa to be max 10 less than the t 02
you
I e Pt on 407 02 minium PaOz should be 3011Pa
A normal Pa coz in a hypoxic asthmatic pt A
sign the
is should be Id due to
pt tiring and may need Icu it

hyperventilation
A low Pao in a well looking pt with normal 02
very
Sats
likely a venous sample

Steps of approach
1 Is the
pt hypoxic
PaOz 110 Hypoxic
Pa 02 8 Severelyhypoxic

2 Is it TI RF or TERF
TI RF Hypoxia t Normocapnia
T2 RF
Hypoxia typerapnia

, A TIRE occurs as a result of ventilation perfusion
mismatch The of air flowing
volume in and out of
the
lungs does not match flow of blood to the lung
tissue Either due to
Reduced ventilation and normal perfusion
Palm oedema or broncho constriction
Reduced perfusion and normal ventilation
Palm emboli

B T2 RF occurs due to alveolar hypo ventilation Pt
eliminate CO2 from blood
adequately oxygenate and
COPD
Pneumonia Rib obesity
Gullian Barre MND
Drugs e.g Opiates

3 Is the
pt pH normal acidotic or alkalotic
Acidotic C 7.35
Alka lotic 7 45


4 Is it respiratory or metabolic
Respiratory 1 9 CO2
Metabolic I T H cos