The acid-base balance in pneumonia.

Abstract

As a part of the study being made of the respiratory and metabolic disturbances occurring in pneumonia, the acid-base balance and the arterial oxygen unsaturation of pneumonia patients have been determined. Thirty observations have been made on 16 patients. The pH was determined directly by Cullen's colorimetric method and checked in 12 instances by electrometric measurements. The CO₂ content, O₂ content and O₂ capacity were determined on the Van Slyke constant volume blood gas apparatus. The analyses to be reported were performed on arterial blood drawn at least once from each patient during the height of the disease and in some instances in the post-febrile period.

The results when plotted on the Van Slyke acid-base diagram, so modified as to include iso-CO₂ tension lines, indicated that almost all of the points were well within the normal acid-base area. No instance of uncompensated acidosis was encountered. In three cases the points fell just outside the normal acid-base area in the compensated acidosis region. One of these patients was afebrile at the time and the other two were suffering from renal disorders. In no instance was there an acidosis of sufficient severity to indicate the advisability of bicarbonate therapy. It has been concluded from the observations thus far that the acid-base condition of patients suffering from pneumonia is usually within normal pH, CO₂ content and CO₂ tension limits.

In eight instances in which we have made repeated observations of the acid-base condition of the same patients we have found evidence that during the febrile period, the CO₂ tension has a tendency to be lower and the pH higher than after the temperature has returned to normal. These results indicate that during the febrile period there is over-stimulation of the respiratory mechanism which leads to a lower CO₂ tension and a slightly higher pH but that this disturbance does not usually remove the patient from a normal acid-base condition.