Question 1:

-This is a real case

PH = 7.253 that is acidaemia (mild)

PCO2 = 61.5. So, we have respiratory acidosis –  Can be acute or chronic (Not that clear from the clinical presentation).

Compensation for acute respiratory acidosis ( HCO3 should increase by 1 for every 10 mmHg of CO2 above 40). Accordingly expected HCO3 should be 26.1. That is very close to the value that we have here (26.2). However, if we have full compensation we should expect PH to be close to normal, (Not as low as 7.25).

The other possibility is chronic respiratory acidosis. In this case the compensation ( HCO3 should increase by 4 for every 10 mmHg of CO2 above 40). Accordingly expected HCO3 should be around 32. Because HCO3 is less than that, then the chronic respiratory acidosis should be associated with other acidosis process (Can be acute metabolic acidosis or acute respiratory acidosis).

The presence of chronic respiratory acidosis with acute metabolic acidosis explains the Low PH = 7.25, also explains the severe lactataemia.

To make things more confusing

• Anion gap is (141 – (102+26)) = 13 (very close to normal).
• Calculated PH level to PCO2 level, 21.5 x 0.008 + 7.25 = 7.42

 Question 2:

This patient was in septic shock due to bilateral pneumonia and although the blood gas results fit well with well compensated acute respiratory acidosis clinically that didn’t fit.

Remember, always trust your clinical assessment.

Management of this case:

•  Early recognition and intervention
•  Appropriate broad spectrum antibiotics (within 30 minutes)
•  Aggressive haemodynamic resuscitation (with fluids and vasopressors – begin with crystalloids – minimum of 30 ml/kg. Vasopressor of choice is Noradrenaline).
• Monitoring of  Blood pressure (MAP>65), Lactate clearance, Urine output> 0.5 ml/kg/hr, CVP 8-12 without pitting oedema, Central venous O2 of 70.
• Source control
• Blood transfusion is only indicated if Hb is < 7 g/dl