Grave acidosis after severe anaphylactic bronchospasm: friend or foe?

In a 20-year-old woman with known asthma, anaphylactic bronchospasm induced a grave combined respiratory and metabolic acidosis (pH(a) 6.66) with marked hypoxaemia (S(a)O(2) 45%). The beneficial effects of the rightward shift of the oxyhaemoglobin dissociation curve on tissue O(2) unloading at such pH was more than offset by the negative effect on S(a)O(2) at the reduced P(a)O(2) (7.0 kPa) found in this patient. This case illustrates the detrimental effect of grave acidosis on arterial blood oxygen content at subnormal P(a)O(2) values, the beneficial effect of a supranormal P(a)O(2) on the S(a)O(2) in such patients, and the rapid remission rate of life-threatening acidosis and blood lactate after adequate ventilation and tissue oxygenation were secured. The initial treatment of the patient and clinically relevant considerations are discussed.