This study evaluates the impact of active thermoregulation on free flap microcirculation following free flap transfer. Thermoregulation is performed by passive warming, active warming (water circulation based device) and active cooling. Changes in microcirculation are assessed using combined laser Doppler flowmetry and remission spectroscopy.

Measurements are conducted at the day of the operation as well as the first three days following the operation. Tissue temperature is assessed by a temperature measurement probe that is placed 8 mm underneath the skin. The microcirculation parameters of free perforator flaps are assessed using combined laser Doppler flowmetry and remission spectroscopy (O2C®). This allows non-invasive measurement of blood flow, capillary venous oxygen saturation and relative postcapillary filling pressure using a fiber optic probe that is placed on the flap surface. Controlled Thermoregulation (between 10 and 38°C) is enabled using a water circulation based system (Hilotherm Clinic®).

Inclusion Criteria:

Patients receiving free perforator flaps with a skin island not less than 4x4 cm

Exclusion Criteria:

• non-compliance,
• non-consent,
• history of cardiac disease,
• arterial hypo- or hypertension,
• intake of vasoactive drugs,
• peripheral arterial occlusive disease,
• chronic kidney and liver disease,
• vasculitis