Blood Gas 018

An 83 year old female is brought to resus with dyspnoea clinically concerning for acute pulmonary oedema. A venous gas is done...

For a basic approach to blood gas interpretation see here

1. What is the Acid-Base distrubance?

pH = 7.341 ∴ slight acidosis

Cause of acidosis?

• CO2 = 30.0 ∴ Primary Metabolic Acidosis

Is there appropriate respiratory compensation or a concomitant process?

• Expected CO2 = 1.5 x HCO3 + 8 = 33.65
• Actual CO2 = 27.6 ∴ concomitant mild respiratory alkalosis

What is the cause of the metabolic acidosis?

• Anion Gap = 133 - 17.1 - 107 = 8.9 = NAGMA (Normal = 12 +/- 4)

Overall: NAGMA with mild respiratory alkalosis

2. Are there any electrolyte issues?

Na (for glc)

• Since Glc is normal, we don't really need to check - we know its as read
• Actual Na - mNa + (Glc - 5)/3 = 133 + (6.3 - 5)/3 = 133.4
• ∴ Normonatraemic

K (for pH)

• Expected K = 5(7.4 - pH) +5 = 5(7.4 - 7.341) + 5 = 5.1
• Actual K = 6.7 ∴ Hyperkalaemic

Ca (for alb)

• Ca = 1.11 corrected on gas

3. Are there any oxygenation issues?

​This is a venous sample ​∴ unable to calculate

4. Are there any other abnormalities?

​COHb & MetHb normal

5. What is your overall impression?

NAGMA with a raised K raises the suspicion that this is likely due to Type 4 renal failure (non-specific renal failure causes a HAGMA normally). Other ddx in the mind map below.

The patient had a crea 350 secondary to obstructive uropathy.