The sudy objective is to evaluate the cerebral haemodynamic status in different ranges of systemic arterial pressure in patients with septic shock by noninvasive tools, transcranial doppler and intracranial compliance by mechanical sensor (B4C).

Patients participating in the study will be submitted to different levels of arterial pressure, titrated with vasopressor and them their cerebral hemodynamic variables will be evaluated,

Sepsis is the most prevalent cause of admissions to the intensive care unit (ICU) and many of these patients develop septic shock (SC) (need for vasoactive drug, after adequate fluid administration, plus hyperlactatemia). The SC involvement is systemic, so the investigators started to monitor organ dysfunctions and their perfusion windows, including neurological disorders, when is affected, in addition to indicating severity, are also a predictor of worse prognosis.

The principle of cerebral autoregulation (CA) is the basic defense mechanism against pressure oscillations in the most diverse contexts. The SC is a state of vasodilation and consequent drop in mean arterial pressure (MAP), that under normal physiological conditions would be compensated by CA. But it is not known exactly how CA performance at this profile of patients.

The investigators will assess cerebral hemodynamics in SC patients at different MAP targets, in order to identify whether this regulatory variable would be able to generate better parameters of cerebral hemodynamics.

Some smaller studies have shown that liver and heart dysfunction correlate with worsening autoregulation. Another clinical trial showed an inverse relationship between CA and the Sequential Organ Failure Assessment, in addition to the loss of CA in patients with circulatory shock in general. Post-mortem data found generalized ischemic lesions in the brain of septic patients, which translates into a state of reduction at vascular flow. This patient profile has more blood-brain barrier dysfunction, but further studies are needed to correlate CA and CS.

The study will be carried out in the ICU of Hospital São Rafael (HSR), located in the city of Salvador-Ba, Brazil. For the evaluation of cerebral hemodynamics Transcranial Doppler and a Mechanical sensor (B4C) will be used.

Data collection on admission will include the following: demographic characteristics, comorbidities, source of infection, Sequential Organ Failure Assessment (SOFA) at ICU admission, temperature, Glasgow Coma scale (GCE) or Richmond Agitation Sedation Scale (RASS), mechanical ventilation, arterial blood gasses before and after the protocol.

All patients will be monitored with an arterial line, cardioscopy, pulse oximetry and capnography (if unavailable at the time of collection, this will be described). Before starting the monitoring, the proper functioning of the arterial circuit will be confirmed and a blood gas analysis will be collected, as well as at the end.

The investigators will collet data with the patient's baseline pressure for 5 minutes (T0), then through the titration of vasopressors, for another 5 minutes each mean arterial pressure target at 65mmHg (T1), 75 mmHg (T2) and 85 mmHg (T3). After collection, the baseline mean arterial pressure will be restored

Inclusion Criteria:

• < 48 hours in the intensive care unit
• Septic shock (sepsis 3.0)

Exclusion Criteria:

• No window for DTC
• Hepatic or uremic encephalopathy
• Pregnancy
• Acute or prior structural neurological insult
• Exogenous intoxication
• Dementia
• Chronic Obstructive Pulmonary Disease
• Instability for acute arrhythmia
• Extracorporeal support by modifying the pulse wave form (intra aortic balloon pump and Extracorporeal membrane oxygenation
• Extreme severity, with imminent risk of death

Patients with septic shock with less than 48 hours of ICU stay

We don't have that plan, but if the data is useful for larger research, no problem.