Summary Interpreting blood gas values

Interpreting blood gas values




Assessing acid–base disorders
Assessing acid–base disorders involves examining the pH, PaCO 2 and
HCO3:

● pH – a low pH (7.4) indicates a tendency towards acidosis, a high pH
(7.4) indicates a tendency towards alkalosis.
● PaCO2 – an increase in PaCO2 leads to acidosis, a decrease to alkalosis.
● HCO3 – an increase in HCO3 leads to alkalosis, a decrease to acidosis.


Assessment
1. Establish whether the patient’s pH is acidotic, alkalotic or normal.
2. If the pH is acidotic establish whether this is due to:
– increased PaCO2 – indicating respiratory acidosis
– decreased HCO3 – indicating metabolic acidosis.
3. If the pH is alkalotic establish whether this is due to:
– decreased PaCO2 – indicating respiratory alkalosis
– increased HCO3– indicating metabolic alkalosis.
4. If the pH is within normal range the original abnormality can be
identified by comparing the pH to the PaCO2 and the HCO3.