Hypotension in patients who are taken to surgery, is a very frequent complication, when the spinal anesthetical technique is used, associating this with significant adverse effects that can lead to morbidity specially in the obstetric patient. The objective of the study is determine if the phenylephrine used of prophylactic form, achieved to prevent the appearance of hypotension in obstetric patients led to Caesarea under spinal anesthesia.

Worldwide, the caesarean section is one of the surgical procedures most frequently performed, representing a challenge to the anesthesiologist, who must administer anesthesia to the mother with minimal effects in the newborn. For this reason, spinal anesthesia emerges as an important option in the management of the obstetrical patient who is going to be taken to Caesarea. The hypotension, is one of the most frequent events adverse associated to this technical anesthetic, represented a risk of complications both, in the mother as in the fetus, by this reason the anesthesiologist must implement different strategies to treat it when this be present. From there arises the necessity of establishing if the phenylephrine, a drug used to treat hypotension, when is administed prophylactically, allows to avoid this effect. We designed a randomized clinical trial in elderly patients over 18 years who are taken to Caesarea, where they formed two groups of patients, one that will administer a prophylactic infusion of phenylephrine compared with placebo, assessing the incidence of hypotension in the two groups and the adverse events most commonly associated with this.

Inclusion Criteria:

• pregnant subjects who are to be delivered to cesarean section under subarachnoid anesthesia
• Gestational age >37 weeks

Exclusion Criteria:

Pregnant subjects with:

• Hipertensive disorders in pregnancy
• Acute fetal distress
• Evidence of placental dysfunction
• History of cardiovascular or cerebrovascular diseases
• hypersensitivity to phenylephrine
• Rejection of the patient