[Systemic and regional hemodynamics in alert rats with increasing hyperthermia]

The changes in the parameters of systemic and regional hemodynamics during thermal stress were followed up in awake male Wistar rats. The cardiac output (CO) and blood flow in 16 zones of the body were measured by means of 15 microns microspheres labeled by 4 different isotopes. The blood flow increased in the skin of the tail, the liver, heart, adrenals, and skeletal muscles and reduced in the organs of the splanchnic region and kidneys. When body temperature reached 42 degrees C the CO decreased. The shifts in the regional blood flow maintained their direction, with the exception of a sharp increase of blood flow in the small intestine which preceded or coincided with the beginning of a fall in arterial pressure. The rate of increase of left ventricular pressure remained at a high level. It is assumed that the disruption of celiac vasoconstriction is among the earlier developing links of hemodynamic disorders in thermal affections and is caused by the vasodilative effect of the factors of local control of the vascular functions.