A method of reducing the concentration of carbon dioxide in blood plasma includes removing blood from a patient and treating or processing at least blood plasma of the blood by flowing the blood plasma on one side of at least one semi-permeable membrane and flowing a dialysate on the other side of the at least one semi-permeable membrane. The dialysate has a concentration of bicarbonate less than the concentration of bicarbonate in the blood plasma before treating the blood plasma and has a composition such that the blood plasma strong ion difference that results from treating the blood plasma in conjunction with an achieved reduction in blood plasma CO2 concentration results in a blood plasma pH that does not change by more than +/−0.5 during treatment.