Reducing tachycardia in septic shock patients: do esmolol and ivabradine have a chronotropic effect only?

An elevated heart rate (HR) often persists in resuscitated septic shock patients, increasing the risk of mortality. Several drugs for HR control, such as esmolol and ivabradine, have been tested in the recent years, but their benefit on the overall cardiovascular system is still under investigation. The aim of this study is to investigate the hemodynamic effects of the two drugs in a protocol of polymicrobial septic shock and resuscitation, mainly focusing on the vascular function. Twelve pigs were divided into three experimental groups: the esmolol-treated group (n=4), the ivabradine-treated group (n=5) and the control group (n=3). The characteristic arterial time constant τ was computed on aortic arterial pressure (AoP), together with estimates of total arterial compliance and peripheral resistance. Power spectral analysis of aortic and radial diastolic BP oscillations was performed to estimate the sympathetic autonomic control of vascular tone. Septic shock induced a severe cardiac and vascular disarray, only partially resolved by resuscitation. The administration of esmolol, but not ivabradine, was beneficial both for cardiac and vascular function, thereby its adjunction to standard therapies could help to improve patient's condition and optimize the resuscitation strategies.