The study aims at clarification of venous collapsibility measures with real venous flow measurements during dynamic maneuver testing fluid responsiveness in septic shock patients.

Sedated and mechanically ventilated patients in septic shock will be enrolled in the study. A fine catheter with ultrasound doppler probe will be introduced into the central venous catheter already in place in superior vena cava. Doppler signal will be evaluated by console prototype (NILUS Medical) and continuous analysis of blood flow velocity respiratory variation will be performed. These values will be compared to standard hemodynamic monitoring parameters (central venous and arterial pressures) and to parameters acquired by transoesophageal (TOE) and transthoracic echocardiography.

Inclusion Criteria:

• patients in severe sepsis or septic shock
• intubation and mechanical ventilation
• sedated patient without spontaneous respiratory efforts
• central venous catheter in place inserted via right internal jugular vein
• signed informed consent by family members

Exclusion Criteria:

• superior vena cava vascular anomaly
• irradiation of neck or mediastinum in medical history
• thrombosis of superior vena cava in medical history
• atrial fibrillation or other irregular rhythm
• permanent or external pacemaker
• aggressive mechanical ventilation (PEEP above 10 cm H2O, Pmax above 30 cm H2O)
• TOE contraindication (oesophageal varices, stricture, tumour, upper gastrointestinal bleeding)
• Pericardial effusion, constrictive pericarditis
• Moderate or severe valvular lesion
• Severe systolic dysfunction of the left (EF less than 30%) or right ventricle (FAC less than 25%)
• Intraabdominal pressure above 20 mmHg
• Open chest
• Obvious severe hypovolemia ( LVEDA<5.5cm2/m2BSA)

18 Years and older, mechanically ventilated ICU patients in septic shock