Lower esophageal contractility: a technique for measuring depth of anesthesia.

Until recently, there has been no simple, accurate, reliable technique for monitoring depth of anesthesia during surgery. A system that measures lower esophageal contractility (LEC) has been designed for this purpose. The system consists of a monitor and a disposable esophageal probe equipped with provoking and measuring balloons. Since the motor control of the esophagus is directly controlled by the brain stem, LEC was postulated to be a reflection of the anesthetic state of the patient. Multiple-center clinical studies have shown that LEC correlates significantly (p less than 0.005) with concentrations of volatile anesthetic agents and patient responses to surgical stimulation. Closed-loop anesthetic techniques have been developed at several institutions based on LEC and hemodynamic parameters. Lower esophageal contractility has been shown to be an accurate monitor of anesthetic depth for a variety of surgical procedures and anesthetic techniques.