The hydrogen-ion concentrations of joint exudates in acute arthritis

Abstract

The hydrogen-ion concentrations of exudates aspirated from joints of patients ill with acute rheumatic fever and other forms of arthritis were determined. This was done: (1) to compare the reactions of the exudates of the various forms of arthritis; (2) to determine if an acidity existed in inflamed joints of acute rheumatic fever patients sufficient to permit the liberation of free salicylic acid following salicylate therapy.

Salicylic acid can not exist as such in alkaline solutions; and its salts have not been shown to have bactericidal power in low concentrations. Although the acid can not exist in normal blood and tissues, their reactions being slightly alkaline, it has been suggested for a number of years that its liberation might occur in the inflamed tissues of patients with acute rheumatic fever; these tissues were supposed to have been under considerably increased CO₂ tension. The bactericidal action of this liberated salicylic acid could explain the seemingly specific action of the salicylates on the arthritis of acute rheumatic fever.

Hanzlik 1 examined exudates from inflamed joints of acute rheumatic fever patients directly for the presence of salicylic acid. The results showed none to be present; but the author offers the criticism that no precaution was taken to prevent the escape of CO₂.

In our work, the hydrogen-ion concentrations of all of the exudates were determined colorimetricaily at room temperature and corrected to 38° C. by a method recently described by Cullen. 2 If sufficient fluid was obtained from a joint, the determination was also made electrometrically. With both methods, in order to prevent the escape of Co₂, the fluid was not allowed to come into contact with the air.

Results.-The reactions of 16 joint exudates from patients with acute rheumatic fever were all slightly alkaline; their hydrogenion concentration varied from P_H 7.2 to 7.38. Seven exudates from patients with chronic arthritis varied in P_H from 7.27 to 7.4.