This is a single-center prospective randomized control trial (RCT) to determine whether the continuous monitoring of the plethysmographic variability index (PVI) during low-risk surgeries, can be used to optimize the intraoperative fluid administration. Low-risk patients that attend our day surgery unit, and who will be operated under general anesthesia, will be randomized to either a liberal fluid group, a restrictive fluid group or a dynamic monitoring group (PVI-directed). The amount of fluid infused together with the time to discharge, will be assessed in each participant during the postoperative period along with additional secondary outcomes.

Inclusion Criteria:

• participants attending the unit for a day surgery procedure
• participants whose surgeries will be performed under general anesthesia
• aged between 18-65 years
• no abnormal findings on chest x-ray or electrocardiogram on preoperative evaluation
• patients undergoing procedures which do not require opening of the abdominal or thoracic cavities

Exclusion Criteria:

• ASA score III or higher
• patients undergoing surgeries which require additional pain management procedures (e.g. selective nerve blockade, epidural anesthesia, etc.)
• known pregnant women
• known kidney disease (or serum creatinine >1.8 mg/dl)
• known liver disease (or AST/ALT >60 U/l)
• known chronic heart failure (determined by a LVEF <55%)
• participants who develop hypotension intraoperatively and do not respond to 4 fluid challenges (1000 ml), requiring aggressive fluid resuscitation OR vasopressors
• estimated blood loss during surgery >250 ml
• development of an adverse reaction to any of the drugs administered during surgery (requiring additional medical management)

Participants will be under general anesthesia during the interventions. Outcome assessors (nurses) will be blinded to the treatment provided in the operating rooms