9th February 2024

Mixed respiratory and metabolic derangement

It is possible to have derangement in both respiratory and metabolic acid-base mechanisms simultaneously. In these cases, CO2 and HCO3- will move in opposite directions on blood gases.

Mixed respiratory and metabolic acidosis:

• pH low
• CO2 high
• Bicarbonate low

Causes include cardiac arrest and multi-organ failure

Mixed respiratory and metabolic alkalosis:

• pH high
• CO2 low
• Bicarbonate high

Causes include hyperemesis gravidarum, excessive ventilation in COPD and diuretic use in liver cirrhosis.