Respiratory acidosis : when and how to correct it

The correction of acidemia due to respiratory insufficiency (respiratory acidosis form CO2 retention) is still an open problem. A logical approach to the problem implies a triple “W” questions: “Why, when and how to correct respiratory acidosis?” In this brief review we will concentrate on how to correct acidemia, as other papers, in this supplement, will discuss the other issues. Although discussed, the use of bicarbonate infusion to correct acidemia is a current practice in Intensive Care Unit, not only in metabolic, but also in respiratory acidosis. A paradigmatic example of this attitude is the protocol of NIH ARDS network (), that suggested in the low tidal volume group the correction with bicarbonate of the acidosis caused by the permissive hypercapnia. Before discussing the possible effects of bicarbonate infusion in this setting, it is worth to describe: 1. the behaviour of the whole blood (in a closed system as in venous compartment) when challenged with an acute increase of CO2; 2. the cross-talking between lung and kidney in vivo, when the hypercapnia persists over several day; 3. the effects of HCO3- administration in vitro and in vivo during respiratory acidosis.