Cardiovascular Effects of Norepinephrine

Previous studies of our team reported the improvement of myocardial contractility both on hemodynamic parameters (by transpulmonary thermodilution) and morphological (by transthoracic echocardiography: TTE), during the early phase of septic shock (during the first 4 hours management of septic shock). However, one can wonder about the effect of NAD on myocardial cardiac ouput and contractility beyond the early phase of septic shock, more precisely beyond the first 24 hours. Indeed, while it continues to act on the "stressed" blood volume and the diastolic left ventricular perfusion by increasing the diastolic arterial pressure (DAP), it has been reported in old studies that beyond the early phase, the sensitivity of the β1-adrenergic receptors is altered due to the phenomenon of internalization of these receptors, leading to a reduction of the myocardial response to catecholamines. The investigators can then wonder whether norepinephrine still exerts a positive effect on myocardial contractility via the increase in DAP, despite an alteration of the β1-adrenergic pathway. To answer this question, the investigators proposed to evaluate the effects of norepinephrine by TTE on cardiac contractility after the initial phase.