Hemodynamic Cardiovascular Indices to Predict the Response to Angiotensin-II in Septic Shock

Septic shock is known to severely impair cardiovascular function, leading to altered pulse wave transmission and blood pressure (BP) control. Current therapies for septic shock have still poor outcomes. Recently, the effectiveness of angiotensin-II (ang-II) in catecholamine-resistant vasodilatory shock has been established. However, excessive dosage of ang-II may have pro-inflammatory and pro-oxidative effects, worsening the cardiovascular condition of septic shock patients. Currently there are no clinical guidelines to optimally guide ang-II administration, and the therapy targets consist mainly in static indices, like mean arterial pressure, which often mask different cardiovascular responses. The main objective of this study is to characterize the cardiovascular response to ang-II in a polymicrobial septic shock animal population, in terms of arterial vascular properties, blood pressure propagation, and blood pressure regulation. Eight pigs underwent a protocol of polymicrobial septic shock and resuscitation with fluids and ang-II, and they were subdivided into low-angII (n = 5) and high-angII (n = 3) according to the total ang-II dosage. Continuous cardiac output (CO), BP in aorta and femoral artery were recorded. The 2-element Windkessel model was used to estimate arterial compliance (AC), total peripheral resistance (TPR), and arterial time constant τ; pulse pressure (PP) amplification was computed as the ratio between femoral and aortic PP; autonomic activity was studied by cardiac baroreflex sensitivity (BRS). The results highlighted a more compromised cardiovascular condition in high-angII pigs, as resulted from the reduced AC, TPR, τ, BRS and PP amplification compared to low-angII. If this behavior was related to shock severity has still to be investigated.