Anesthetic protocol and measurements. Spinal anaesthesia is introduced with a single intrathecal injection of 0.75% plain ropivacaine using a 22 or 25-gauge needle with the patient in the lateral or sitting position. The dose range is 12mg to 18mg, depending on age and height. Perioperative hemodynamic monitoring is carried out with an indwelling radial artery catheter. Patients with intraoperative mean blood pressure (MBP) ≤65 mmHg, or <25% of its baseline preoperative value were considered hypotensive. Arterial hypotension related to bone cement application, tourniquet deflation, overt intraoperative/postoperative bleeding (blood loss>150cc) or patients receiving blood transfusion for any reason were not considered.