The optimal levels of mean arterial pressure that must be achieved in septic shock are subject of debate. Studies tried to correlate blood pressure increase in patients with septic shock with microcirculation. However, there are few studies that specifically assessed septic shock patients with previous arterial hypertension. The main objective of this study is to evaluate the effect of increased blood pressure level in the microcirculation of these patients and compare them with patients without arterial hypertension.

Hypothesis: After a rise in mean arterial pressure, microcirculation improvement will occur only in the previously hypertensive patients.

Study design: Prospective clinical trial Setting: Intensive care units of the Anesthesiology Department at the Federal University of Sao Paulo and the intensive care unit of Kidney Hospital.

Studied population: Forty patients will be included, being 20 without known history of systemic arterial hypertension and 20 with this diagnosis for at least 2 years and already with clinical or subclinical organ damage.

Inclusion criteria: age over than 18 years old, norepinephrine drug use for at least 12 hours and for less than 72 hours, sedation level equal or deeper than Ramsay 4, blood pressure stable for the last 30 minutes prior to inclusion, central venous catheter in place and signed informed consent.

Exclusion criteria: pregnancy, cirrhosis, systemic sclerosis, and need to maintain mean arterial pressure above 65mmHg for others conditions.

Intervention: noradrenaline dose will be risen to obtain a mean arterial pressure of 85-90 mmHg.

Assessments and outcome: Systemic hemodynamic (central venous oxygen saturation, cardiac output, heart rate, central venous pressure) and sublingual microcirculation variables (microcirculatory flow index, total vascular density, proportion of perfused vessels, perfused vascular density) will be measured before and after the rise in mean arterial pressure. Sidestream darkfield will be used to assess microcirculation. The variation between those variables before and after the intervention will be compared.

Inclusion Criteria:

• age over than 18 years old,
• norepinephrine drug use for at least 12 hours and for less than 72 hours,
• sedation level equal or deeper than Ramsay 4,
• blood pressure stable for the last 30 minutes prior to inclusion,
• central venous catheter in place and
• signed informed consent.

Exclusion Criteria:

• pregnancy,
• cirrhosis,
• systemic sclerosis, and
• need to maintain mean arterial pressure above 65mmHg for others conditions

undecided