Artificial Hyperæmia.—When such direct means as the above are impracticable, much can be done to aid the tissues in their struggle by improving the condition of the circulation in the inflamed area, so as to ensure that a plentiful supply of fresh arterial blood reaches it. The beneficial effects of hot fomentations and poultices depend on their causing a dilatation of the vessels, and so inducing a hyperæmia in the affected area. It has been shown experimentally that repeated, short applications of moist heat (not exceeding 106° F.) are more efficacious than continuous application. It is now believed that the so-called counter-irritants—mustard, iodine, cantharides, actual cautery—act in the same way; and the method of treating erysipelas by applying a strong solution of iodine around the affected area is based on the same principle.
Fig. 6.—Passive Hyperæmia of Hand and Forearm induced by Bier's Bandage.
While these and similar methods have long been employed in the treatment of inflammatory conditions, it is only within comparatively recent years that their mode of action has been properly understood, and to August Bier belongs the credit of having put the treatment of inflammation on a scientific and rational basis. Recognising the “beneficent intention” of the inflammatory reaction, and the protective action of the leucocytosis which accompanies the hyperæmic stages of the process, Bier was led to study the effects of increasing the hyperæmia by artificial means. As a result of his observations, he has formulated a method of treatment which consists in inducing an artificial hyperæmia in the inflamed area, either by obstructing the venous return from the part (passive hyperæmia), or by stimulating the arterial flow through it (active hyperæmia).
Bier's Constricting Bandage.—To induce a passive hyperæmia in a limb, an elastic bandage is applied some distance above the inflamed area sufficiently tightly to obstruct the venous return from the distal parts without arresting in any way the inflow of arterial blood ([Fig. 6]). If the constricting band is correctly applied, the parts beyond become swollen and œdematous, and assume a bluish-red hue, but they retain their normal temperature, the pulse is unchanged, and there is no pain. If the part becomes blue, cold, or painful, or if any existing pain is increased, the band has been applied too tightly. The hyperæmia is kept up from twenty to twenty-two hours out of the twenty-four, and in the intervals the limb is elevated to get rid of the œdema and to empty it of impure blood, and so make room for a fresh supply of healthy blood when the bandage is re-applied. As the inflammation subsides, the period during which the band is kept on each day is diminished; but the treatment should be continued for some days after all signs of inflammation have subsided.
This method of treating acute inflammatory conditions necessitates close supervision until the correct degree of tightness of the band has been determined.
Fig. 7.—Passive Hyperæmia of Finger induced by Klapp's Suction Bell.