Effects Of Arterial Baroreflex Function On Septic Shock In Rats

Arterial baroreflex (ABR) play an important role in the regulation of cardiovascular activities, maintenance stability of blood pressure in a given extent is its main physiological function. It is demonstrated that baroreflex dysfunction was associated with a poor prognosis in many cardiovascular diseases. The present work was designed to study the relationship between ABR and survival time in septic shock.Removal of the carotid sinus and aortic arch baroreceptors results in the inability to buffer moment-to-moment changes in pressure bringing about arterial pressure lability. Despite the marked variability of arterial pressure, 24-h mean pressure level is unchanged or only slightly increased in animals without baroreceptor reflexes. According to this method, the rats were divided into sham-operated group and SAD group.Each rat received an equivalent dose of intravenous lipopolysaccharide (LPS) (50 mg/kg). It was found that the sinoaortic denervated (SAD) rats were alive a shorter time than the sham-operated rats. LPS injection resulted in an immediate decrease in blood pressure, followed by a rebound increase and a secondary decrease.After cecal ligation and puncture (CLP), it was found that the survival time was significantly reduced in SAD rats than in sham-operated rats (12.7±2.92 h vs 15.0±4.01 h, P＜0.05). Significantly differences were seen when the results were expressed by Kaplan-Meier survival curves. We found the baseline of noradrenaline was significantly elevated in SAD rats. Compared with the baseline values, both noradrenaline and adrenaline significantly increased in either SAD or Sham group after CLP. In addition, the TNF-α, noradrenaline and adrenaline levels of the SAD group were significantly higher than those of the Sham group at 5 hours post-CLP.Multiple linear regression analysis showed that the survival time correlated closely with BRS, but did not with systolic blood pressure and diastolic blood pressure.For the first time we draw a complete blood pressure profile during CLP-induced lethal sepsis in sham-operated rats. Typical tracings of post-CLP blood pressure showed a time related slow decrease.Summarizing all experimental results, the present work demonstrated that ABR function was related to the survival time in lethal septic rat model. The loss of inhibition in the sympathetic activity and in the release of some inflammatory cytokines during septic shock related to baroreflex and/or chemoreflex dysfunction may be the mechanisms involve in the poorer prognosis in sepsis.