A 19-year-old patient has received multiple stab wounds.

The patient is in hypoperfusion (shock) from blood loss. In shock states, tissues are deprived of oxygen, leading to anaerobic metabolism, which produces lactic acid as a byproduct. This causes metabolic acidosis, which is a critical sign of systemic oxygen debt.

Carbon dioxide rises with respiratory failure, but lactic acid is a more specific indicator of cellular hypoxia.