Acid-Base Equilibrium and Salt and Water Exchange

PHYSIOLOGICAL AND CHEMICAL CONSIDERATIONS Definitions: Van Slyke72 has defined acidosis as a condition in which the bicarbonate of the blood or serum, or, more exactly, the base available for combination with bicarbonate, is diminished. Alkalosis is a condition in which there is in the blood or serum an abnormal excess of bicarbonate, or base available for combination with bicarbonate. These definitions are quite restricted: they say nothing of the true reaction or hydrogen-ion concentration of the blood, nothing of abnormal accumulations of acid. Nevertheless they have come to be accepted because they are expressed in terms of that function of acid-base equilibrium which is most frequently disturbed and which can be most easily and accurately measured. The function of bicarbonate: Bicarbonates are salts of carbonic acid which is nothing more than the gas, carbon dioxide, in solution. Carbonic acid plays a peculiar role among acids in biology because of a special combination of properties: i. it is a weak acid and an excellent buffer at physiological reactions; 2. it is produced in large quantities in the normal metabolic processes and is, therefore, always available from endogenous sources; 3. it is volatile and can, therefore, be excreted by the lungs. The reactions involved in the formation of bicarbonate by combination of C02 and base, and the liberation of C02 from bicarbonate are: produced in metabolism of tissue.