Evaluation of the Changes of Pleth Variability Index During Preoxygenation for Predicting Hypotension During Induction of Anesthesia in Surgical Patients; Prospective Observational Study

In patients with hypovolemia or dehydration, pulse pressure variation can be increased by spontaneous forced inspiratory breathing. PVI is a noninvasive method of indicator of fluid responsiveness like purse pressure variation. We expected that the amount of change in PVI between at the time of entering operating room and after preoxygenation with forced inspiration method could be different depending on the patient's volume status.

After entering operating room, monitoring devices, anesthesia depth sensor, and Radical-7® Pulse CO-Oximeter® are attached. Patients rest for 5 minutes, and then baseline systolic blood pressure, diastolic blood pressure, mean blood pressure, and heart rate are collected every 1-minute. Pleth variability index (PVI), perfusion index (PI) are also measured continuously. For pre-oxygenation of anesthesia, take 8 deep breaths at flow 10 l/min of 100% oxygen for 1 minute with maximally forced inspiration. After that, for 2 minutes, patients breathe as usual while maintaining oxygen supply. until tracheal intubation or laryngeal mask insertion. Anesthesia is induced with target concentration infusion of 4.0 ng/ml of remifentanil and 4.0 ug/ml of propofol. When the patient loses consciousness, rocuronium 1.0 mg/kg is administrated and endotracheal tube or laryngeal mask is inserted 2 minutes after. PVI, PI, blood pressure, and heart rate are measured until tracheal intubation or laryngeal mask insertion. Anesthesia induction-related hypotension is defined as a decrease in mean arterial pressure below 60 mmHg at any timepoint from baseline parameter collection to until airway device insertion. The parameters are analyzed by comparing between groups with and without anesthesia induction-related hypotension.