acid base balance (5 steps in diagnosis)

Dr. Zahoor Ahmad

1. Is the pH normal? 2. Is the CO2 normal? 3. Is the HCO3 normal? 4. Match the CO2 or the HCO3 with

pH5. Does the CO2 or the HCO3 go the

opposite direction of the pH?

Normal pH 7.36-7.44pH< 7.36 AcidosispH > 7.44 Alkalosis

Normal CO2 36‐45mmHgCO2 > 44mmHg Acidotic level CO2 < 36mmHg alkalotic level

Normal HCO3 22 ‐26mmHgHCO3 < 22mmHg Acidotic level HCO3 > 26mmHg alkalotic level

If pH and CO2 match each other, then primary acid-base abnormality is respiratory.

If pH and HCO3 match each other, then primary acid-base abnormality is Metabolic.

(a)CO2 acidoticpH acidotic

Then primary acid-base balance???

(b)CO2 alkaloticpH alkaline


(a)Respiratory acidosis

(b)Respiratory alkalosis

(a)HCO3 acidoticpH acidotic


(b)HCO3 alkaloticpH alkaline


(a)Metabolic acidosis

(b)Metabolic alkalosis

Does either the CO2 or HCO3 go in opposite direction of pH? If so, there is compensation by the system.

pH acidoticCO2 acidoticHCO3 alkalotic

What is acid-base balance?????????

Respiratory acidosis with

metabolic compensation

(Respiratory acidosis with metabolic compensation)

pH alkaloticCO2 alkaloticHCO3 acidotic


Respiratory alkalosis with

metabolic compensation

(Respiratory alkalosis with metabolic compensation)

HCO3 alkaloticpH alkaloticCO2 acidotic


Metabolic alkalosis with

Respiratory compensation

(Metabolic alkalosis with Respiratory acidosis)

HCO3 acidosispH acidosisCO2 alkalosis


Metabolic acidosis with

Respiratory compensation

(Metabolic acidosis with Respiratory compensation)

Test Normal ↓ Value ↑ Value pH 7.35-7.45 Acidosis Alkalosis pCO 2 35-45 Alkalosis Acidosis HCO 3 22-26 Acidosis Alkalosis

pH 7.52CO2 29HCO3 23

pH 7.18CO2 44HCO3 23

pH 7.60CO2 37HCO3 35

pH 7.30CO2 30HCO3 14

Complete compensation returns the pH normal.

Thank You

acid base balance (5 steps in diagnosis)

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