PH = 7.14, that is severe acidaemia
pCO2 = 53 mmHg, So we have respiratory acidosis. Next we will calculate the compensation.
From the story the condition is most likely acute (Cardiac arrest). For acute respiratory acidosis we expect HCO3 to increase by 1 for every 10 pCO2 above 40 mmHg.
Accordingly, expected HCO3 should be 25.3 (24 + 13 x 0.1). This patient’s HCO3 is 22 mmol/L. So, we have additional metabolic acidosis.
Next, we need to calculate the anion gap to find out what type of metabolic acidosis we have.
Anion gap is calculated as (Na – (Cl + HCO3) = 138 – (100 + 22) = 16. So, we have HAGMA.
Since we have HAGMA, we need to calculate the delta ratio. This is calculated as (AG -12) / (24 – HCO3) = 2. So we have pure HAGMA.
Other abnormal results:
Glucose = 12.5, hyperglycemia (Could be part of stress response).
Lactate = 4.6 mmol/L. This is hyperlactataemia, expected with cardia arrest.
Combined respiratory acidosis and HAGMA with moderate hyperlactataemia secondary to cardiac arrest.
HAGMA is most probably is due to high lactate level.
First consider patients factors:
- Premorbid medical state, advanced cancer, advanced dementia, etc
- Does the patient have advanced health directive
Then Consider the current situation of the arrest:
The most reliable indicator is exhaled (In intubated patient) CO2 less than 10 mmHg after 20 minutes from commencement of CPR (this has zero survival).
Low PH and high lactate are not reliable indicators, there are reported cases of ROSC with PH of 6.6 and with lactate more than 15 mmol/L.
Also there are reported cases of ROSC in patients with cardiac ECHO that didn’t show any cardiac activities.
Other important factor to consider are
- Number of shocks delivered
- Is the patient intubated or not
- Drugs given according to ACLS guidelines
- Any R=rhythm changes
- The presence of reversible causes.