The investigators will define procoagulant properties of packed red blood cells and investigate whether packed red blood cells from certain donor populations are prone to induce procoagulant states.

Inclusion Criteria:

• group 1: healthy female volunteers 18-35 y.o.
• group 2: healthy male volunteers 18-35 y.o.
• group 3: healthy female volunteers 36-60 y.o.
• group 4: healthy male volunteers 36-60 y.o.
• group 5: female volunteers 36-60 y.o., BMI 26-45
• group 6: male volunteers 36-60 y.o., BMI 26-45

Exclusion Criteria:

• age below 18 years
• age above 60 years

volunteers who will donate one unit of packed red blood cells