The goal of this randomized controlled trial is to compare for non inferiority for fetal wellbeing Hypotension Prediction Index - Guided Therapy and Continuous Norepinephrine Infusion in in the Prevention of Spinal Anesthesia-Induced Hypotension for Cesarean Delivery.

The main question it aims to answer are:

• are fetal arterial base excess comparable with the two treatments?

Participants will undergo continuous noninvasive hemodynamic monitoring with advanced Hypotension Prediction Index Researchers will compare with patients receiving continuous norepinephrine infusion and standard blood pressure monitoring with arm cuff.

In the Hypotension Prediction Index group, patients will be monitored continuously with a noninvasive hemodynamic device. The Hypotension Prediction Index is a number based on al algorithm that predicts impeding hypotension if it is greater than 85. In the treatment group, patients will be treated with norepinephrine boluses if the Hypotension Prediction Index is >85. In the control group patients will be treated with preventive continuous infusion of norepinephrine and blood pressure will be measured noninvasively every minute. Data about blood pressure and the vasopressive treatment will start concomitantly to the administration of spinal anesthesia and will stop after delivery. blood gas samples will be then collected from the placental umbilical artery to compare fetal arterial base excess as primary outcome for non-inferiority.

Inclusion Criteria:

• Pregnant women between the 36th and the 40th week of gestation undergoing spinal anesthesia for elective caesarian delivery.

Exclusion Criteria:

• preeclampsia;
• eclampsia;
• atrial fibrillation and sinus tachycardia;
• cardiovascular diseases;
• neuromuscular disease;
• emergent or urgent cesarean delivery;
• coagulopathies;
• contraindications to spinal anesthesia.

pregnant women at term