A method previously established in the experimental animal for predicting the acute response to either metabolic stress (bicarbonate administration) or respiratory stress(manipulation of oxygenator gas during cardiopulmonary bypass) has been extended to man. The method is based on a single nomogram. The accuracy of the nomogram is demonstrated using data from 13 patients on cardiopulmonary bypass. Similar agreement obtains between the nomogram and data reported by others. The nomogram can be used to estimate the therapeutically required dose of bicarbonate.