The risk of bleeding is important during transsphenoidal surgery. This study aims to find if the ventilation mode, controlled pressure and controlled volume, modifies the risk of bleeding.~group Volume controlled ventilation: tidal volume of 7 mL/kg ideal body weight, frequency of 12 cycles/minute, I/E ratio of 1:2, no positive end expiratory pressure. Ventilatory frequency is changed if necessary to maintain end-expiratory pressure of CO2 between 35 and 40 mmHg.~group Pressure-controlled ventilation: initial pressure of 15 cm H2O, frequency of 12 cycles/minute, I/E ratio of 1:2, no positive end expiratory pressure. Pressure is modified to maintain a tidal volume of 7 mL/kg of ideal body weight and frequency ventilation is modified to maintain end-expiratory pressure of CO2 between 35 and 40 mmHg.~In both groups, the fraction of inspired oxygen is 50%. A recruitment maneuver is performed if the blood oxygen saturation became less than 92%.
The risk of bleeding is important during transsphenoidal surgery. This study aims to find if the ventilation mode, controlled pressure and controlled volume, modifies the risk of bleeding.