MICROCIRCULATION DURING HYPOTHERMIA; HIGH SPEED CINEMATOGRAPH STUDIES.

Intravascular aggregation of red blood cells has been described in a number of infectious conditions and injuries. Knisely 1 has recently published an excellent review. Bigelow and associates 2 demonstrated intravascular aggregation occurring in surface cooled animals. They observed this phenomenon to occur at about 32 C becoming severe at 25 C to 20 C. Recently, it has been suggested that the aggregation these workers observed was due to the decrease in arterial pressure, which accompanies surface cooled animals, rather than the hypothermia per se. 3 This report describes the microcirculation before and during profound hypothermia in which the blood pressure and perfusion rate were maintained relatively constant. Methods Observation and recording of the behavior of the red blood cell in the microcirculation were made possible through the use of high-speed cinephotography. The mesenteries of dogs, anesthetized with pentobarbitol, were mounted vertically on a movable stage. A 1,500 watt General