Infusion of E. Coli Lipopolysaccharides Toxin in Rats Produces an Early and Severe Impairment of Baroreflex Function in Absence of Blood Pressure Changes

ABSTRACT: The assessment of baroreflex function since the first appearance of endotoxemia is important because the arterial baroreflex should exert a protective role during sepsis. Nevertheless contrasting results were previously reported. This could be due to the hemodynamic instability characterizing this condition that may per se interfere with reflex cardiovascular adjustments. Aim of our study was therefore to study the baroreflex function 1) since the very beginning of infusion of E. coli lipopolysaccharides toxin (LPS) and 2) in absence of the unloading effect produced by a decrease in blood pressure. LPS was infused in 10 rats for 20 minutes at the infusion rate of 0.05 mg/kg/min. Blood pressure was continuously measured before, during and after infusion and the baroreflex function was evaluated analysing spontaneous fluctuations of systolic blood pressure and pulse interval by the sequence and transfer-function techniques. Plasma concentrations of inflammatory (IL-6, TNF-alpha) and anti-inflammatory (IL-10) cytokines were measured in other 8 rats, similarly instrumented, 4 of which receiving the same LPS infusion. We found that blood pressure levels did not change with the infusion of LPS while inflammatory cytokines increased significantly. The baroreflex sensitivity was significantly reduced 10 minutes after the beginning of LPS infusion, reached values about half those at baseline within 15 minutes after the start of infusion, and remained significantly low after the end of infusion. In conclusion, we documented that septic-shock inducing LPS infusion is responsible for a very rapid impairment of the baroreflex function, independent from the level of blood pressure.