Epidural analgesia is established as the gold standard in the management of post-surgical pain in multiple modalities, including the pediatric patient. It is a technique that is not without risks, but with multiple benefits such as less response to stress, less incidence of chronic pain after surgery, less incidence of nausea and vomiting and other adverse effects derived from opioids, faster recovery and increased patient and family satisfaction.

However, as it has been mentioned, the epidural carries risks both in the technique itself (wet or intravascular puncture) and subsequently after the injection of medication that generates a sympathetic blockade with arterial hypotension and an increase in compensatory heart rate. Unlike in adult patients, in pediatric patients epidural and subarachnoid anesthesia are better tolerated hemodynamically due to less vagal and sympathetic activity and almost no systemic venodilation. This lower activity of the autonomic nervous system is due to its immaturity, which is why, with the growth of the infant, this anesthetic technique increasingly affects its hemodynamics, being similar to the adult at the age of 8-12 years.

The study hypothesis does not differ from that stated in physiology books and studies, but the investigators seek to identify the direct correlation of age with the different hemodynamic parameters available with current technology (cardiac output, systemic vascular resistance, blood pressure ) in pediatric patients after epidural anesthesia.

The study will be carried out in pediatric patients undergoing major surgery that requires the placement of an epidural catheter and invasive blood pressure, without modifying in any way the usual practice of the responsible anesthesiologist. The patient's hemodynamic data will be collected at time 0 (prior to catheter placement), one minute, 5 and 10 minutes after the bolus of local anesthetic administered to measure the child's hemodynamic response and relate it to their age and development. .

Through this work the investigators seek to establish statistically and numerically a hypothesis affirmed in physiology books. In this way, if it is found a positive correlation with age and hypotension, the responsible physician can be alerted to the need for possible vasoconstrictor requirements or more advanced monitoring in order to reduce intraoperative risks.

Inclusion Criteria:

• Patients under 12 years of age undergoing major surgery with epidural catheter placement and invasive blood pressure.

Exclusion Criteria:

• Allergy to local anesthetics (LA).
• Congenital diseases which affect the central nervous system.
• Inability to place an invasive arterial catheter.

Patients under 12 years of age undergoing major surgery in the University Hospital La Fe, in Valencia