The purpose of this study is to evaluate PPI as a surrogate for clinical signs of peripheral perfusion in patients in septic shock and after cardiac surgery.

The aim of this study is to validate PPI as a continuous, objective measurement of peripheral perfusion indicated by clinical sings of tissue perfusion in patients with septic shock. Furthermore, PPI shall be compared to the perfusion of solid organs evaluated by ultrasound of liver, kidney and gut. In a group of healthy volunteers the investigators will determine normal values in ambient temperature and after cooling of an extremity. Another group of patients after cardiac surgery, where usually a poor tissue perfusion without metabolic failure is present will serve as another "control" population in their post-surgery stabilization period. The values from healthy volunteers and cardiac surgery patients will be compared to those of patients in septic shock.

Septic patient:

Inclusion criteria:

• ICU admission with septic shock defined as:
• documented infection (suspected or confirmed) AND
• systemic mean blood pressure <65mmHg requiring any dose of vasopressor despite adequate fluid resuscitation (min. 20ml/kg crystalloids) AND
• lactate >2mmol/l
• Deferred consent by a relative with following informed consent by patient as documented by signatures (Appendix Informed Consent Form)

Exclusion criteria:

• Age <18 or >80 years
• present or suspected myocardial ischemia
• acute pulmonary embolism
• known liver disease - Child-Pugh -Class B or C
• known chronic renal failure
• known peripheral artery disease

Patient after cardiac surgery:

Inclusion criteria:

• ICU admission after coronary artery bypass grafting or valve surgery with cardiopulmonary bypass
• General consent with admission at the University hospital

Exclusion criteria:

• Age <18 or >80 years
• known peripheral artery disease
• no or only low dose of vasopressors (<300µg/h) at ICU admission
• present or suspected myocardial ischemia
• acute pulmonary embolism
• known liver disease - Child-Pugh -Class B or C
• known chronic renal failure

Healthy volunteers:

Inclusion criteria:

- Informed consent as documented by signature (Appendix Informed Consent Form)

Exclusion criteria:

• Age <18 or >80 years
• known peripheral artery disease

Female and male septic shock patients with ICU admission Female and male patients after cardiac surgery with ICU admission healthy volunteers