Potential Benefits of the Study The results of this study will allow us to determine which clinical or US-measurement can yield better performance so as a preoperative prediction of spinal-induced hypotension can be achieved; that way these measurements can permit and guide a targeted preoperative fluid challenges prior to the implementation of spinal anesthesia Potential Side Effects of the Study Participation in this protocol will not put patients at higher risk for complications since we do not perform any intervention (either pharmacological or surgical) There will be no occupational risks to researchers or assistants. Proposed Timetable According to the exclusion criteria and taking into account the number of cases performed in our department per monthly basis, it should take us approximately 6 months to recruit 60 patients.