The goal of this prospective observational study is to analyse change in VO2 and VCO2 measured via a dedicated ventilator after hemodynamic optimization maneuvers in adult patients admitted to the ICU with any sign of shock.

The main questions it aims to answer are:

1. Do common maneuvers for hemodynamic optimization (fluid bolus and/or vasopressor administration) have any impact on tissue perfusion in terms of oxygen consumption (VO2) and carbon dioxide production (VCO2) measured by a dedicated ventilator?
2. Are the values measured by exhaled gas comparable to those calculated by the measurement of dissolved veno-arterial gas?

Participants enrolled in the study will receive advanced hemodynamic monitoring with MostCare Up (Vygon ®) and their hemodynamic instability will be managed according to most recent guidelines and based on clinical decision of treating physicians.

Inclusion Criteria:

Hypotension (MAP< 65mmHg or sudden drop in MAP > 15 mmHg) and one of the following conditions:

• Heart rate > 120 bpm
• Urinary output < 0.5 ml/kg/h for at least two hours
• Lactate > 2 mmol/L

Exclusion Criteria:

• Urgent need for surgery
• Urgent need for veno-arterial ECMO or severe hemodynamic instability
• Consistent risk of imminent death
• Severe ARDS or severe respiratory failure (p/F < 100 mmHg) and/or FiO2>0.8
• Severe heart failure (NYHA 4 and/or EF<25%)
• Need for intermittent or continuous renal replacement therapy (IRRT or CRRT)
• Anemia defined as Hb<8 g/dL
• VO2 variability < 5% throughout ten minutes of stabilization before procedure start
• Intraabdominal hypertension, defined as intraabdominal pressure > 18 mmHg
• Pregnancy
• Withdrawal or refuse of informed consent
• Terminal disease
• Do-not-resuscitate order.

Patients admitted to the ICU with signs of hemodynamic instability