Concentration of Congo-Red in the Blood after Absorption from the Pneumonic Lung

Abstract

The pulmonary circulation undergoes marked alterations in pneumonia, (1) to a condition of hyperemia and (2) to that of ischemia. Upon the state of efficiency of the circulation in the infected tissues must depend largely the rate of absorption of the toxic products of the infection, and upon the latter must depend the severity of the toxic symptoms. These experiments represent the initial phase in a study of the absorption rate as a basis for a better understanding of the symptomatology of pneumonia. Congo red was the substance injected into the lung for testing the absorption of soluble products, because it is identifiable and measurable in the blood, and, in the normal individual at least, is eliminated from the blood (by the liver) at a slow and uniform rate as compared with other non-toxic dyes. The only diseases known 1 to alter appreciably the rate of elimination of congo red are amaloidosis, which retards it, and nephrosis and cirrhosis, which sometimes accelerate it, but these are not found in dogs.

Pneumonia was produced in 24 dogs by the method of Terrell, Robertson and Coggeshall, 2 with the modifications that the pneumococci (type 1) were suspended in saline rather than in the more viscid medium, to allow them to reach the peripheral airways more easily, and that the inoculation was made bronchoscopically. Morphine, atropine and ether were given previously, and 3 cc. of a thin inoculum was injected into one bronchial branch of the right lower lobe. After an interval of 2, 4, 24, or 48 hours, the animals were anesthetized again, a sample of blood was obtained, congo red (1 cc. of 1.25% solution per kg. body weight) was injected very slowly into the same bronchus as was used for the inoculation, and samples of blood wrere collected at 10-minute intervals thereafter for nearly 2 hours.