The purpose of this study is to evaluate renal effects of 3 different levels of mean arterial pressure in early case of septic shock. In 8 patients diagnosed with early septic shock, we will adjust mean arterial pressure (MAP) to three different levels, using norepinephrine. At each level of MAP, central and renal hemodynamics and oxygenation states will be measured. Analysis will be made to describe the pathophysiology at MAP 75 mmHg, and then to evaluate at which MAP renal function and oxygenation is least affected negatively.

It is under debate what level of mean arterial pressure is the most appropriate for organ perfusion in septic shock. The kidneys are usually used for end-organ evaluation of appropriate perfusion and appropriate blood pressure level. What "adequate blood pressure" means is today unclear.

The purpose of this study is to chart the renal perfusion, oxygenation and function, and moreover to evaluate renal effects of 3 different levels of mean arterial pressure, in early phase of septic shock.

Patients will be included within the first 24 hrs after admission to the ICU diagnosed with septic shock. The patients will be sedated, mechanically ventilated and in need for norepinephrine for adequate blood pressure levels.

After 60 mins of steady state at MAP 75 mmHg, norepinephrine will be adjusted achieve MAP of 60 and 90 mmHg respectively, MAP being held at each level for 30 mins. At the end of each 30 mins period, central and renal hemodynamics will be measured, blood and urine samples will be collected.

Central hemodynamics will be measured by, and blood samples collected via a pulmonary catheter and an arterial line.

Renal hemodynamics will be measured using a renal vein catheter for retrograde thermodilution giving at hand renal blood flow (RBF), renal vein blood samples and urine collection provides extraction of Cr-EDTA for filtration fraction (FF) and glomerular filtration rate (GFR), renal oxygen consumption, and renal oxygen extraction as a measure of balance between renal oxygen delivery and consumption.

Via renal vein catheterisation and retrograde thermodilution, the study group have the unique possibility to actually evaluate renal blood flow, renal oxygenation and renal function in humans in vivo.

After finishing the data collection, analysis will be made to answer the question: which MAP is the most optimal concerning RBF, GFR and renal oxygenation in patients with septic shock?

Inclusion Criteria:

• stable septic shock
• normovolemic
• norepinephrine
• intubated/ventilated
• normal s-creatinine according to local laboratory regards.