Goal-directed Fluid Therapy During Deep Inferior Epigastric Perforator (DIEP) Free Flap Breast Reconstruction

For adequate free flap perfusion during Deep Inferior Epigastric Perforator (DIEP) flap breast reconstruction surgery, blood pressure must remain sufficiently high. General anaesthesia often induces systemic hypotension. To counteract this hypotension, the anaesthetist administers intravenous fluids (crystalloid fluids). However, fluid overload can lead to an increased risk of flap oedema and decreased flap perfusion and in exceptional cases to flap failure. To maintain blood pressure above 100 mmHg and to avoid excessive fluid administration, a vasopressor (norepinephrine) can be administered. This reduces the amount of fluids administered, thereby reducing the risk of flap oedema. This study aims to determine whether the use of a measurement of preload dependency (Pulse Pressure Variation = PPV), can guide fluid therapy and if it decreases the risk of flap oedema. To this end, two fluid management strategies will be compared: * Static intraoperative fluid management: Administration of crystalloid fluids is limited to 5ml/kg/h * Dynamic intraoperative fluid management: Crystalloid fluids are only administered if PPV exceeds 12% The purpose of this study is to compare the static and dynamic (= targeted) fluid strategy and to evaluate the effect on flap oedema and flap perfusion. All included patients are randomized in a 1:1 ratio to the static (n = 41) or dynamic group (n = 41). To treat hypotension in patients randomized to the 'static' group, fluid administration is limited to 5 ml/kg/h. When the maximum fluid volume is administered but blood pressure remains below 100 mmHg, norepinephrine is administered. Treatment of hypotension in patients randomized to the 'dynamic' (= targeted fluid therapy) group, is guided by PPV. PPV is measured continuously during the surgery and if the blood pressure is below 100 mmHg, fluids are only administered if PPV is \> 12%. If blood pressure is below 100 mmHg but PPV is \< 12% (indicating no fluid is needed), norepinephrine is administered. At the end of the procedure, 2 sensors are applied, these sensors provide information about the perfusion of the free flap during patient's stay in Intensive Care or the recovery room.