Can the ideal dosage scheme be developed when performing anesthesia induction with target controlled infusion devices?

Aim: In this study, it was aimed to develop a clinically based dose formula for anesthesia induction and endotracheal intubation without using depth of anesthesia monitoring. Materials and Methods: The study included 128 patients with ASA (American Society of Anesthesiologists) I-II, 18-65 years of age, without known cognitive impairment, patients that undergone elective surgery under general anesthesia, and whose informed consent was obtained. Beside the standard monitoring (electrocardiogram, pulse oximetry, non-invasive blood pressure), Bispectral index (BIS) and Train of Four (TOF) monitoring were used. After premedication with 1 mcg/kg fentanyl, effect-site concentration (Ce) of propofol (Schnider model) and remifentanil (Minto model) were used during TCI adjustment for anesthesia induction. remifentanil Ce target was set at 2ng/ml and kept constant throughout induction. Propofol Ce value was started at a basal dose of 2mcg/ml and 1 mg/kg rocuronium was administered after the dose was recorded by increasing the dose of 0.2 mcg/ml every 20 seconds and the loss of eye-opening response to the sound stimulus (LOC; loss of consciousness) was determined and recorded. The dose increase was continued as indicated, and the dose at which the BIS value was 50 for 30 seconds was recorded as the intubation dose (INT-P). Patients with TOFc=0 were intubated, patients with TOFc>0 were excluded from the study. Hemodynamic parameters were recorded as mean arterial pressure (MAP) and heart rate (HR); basal value, LOC, before and after intubation, at 0,1,3,5,10 minutes. Hemodynamic deterioration was defined as a >20% increase in MAP and or HR after intubation compared to before. Results: In our study, a statistically significant correlation was found between LOC-P and INT-P (p<0.001). In order to estimate the depth of anesthesia based on clinical findings and to perform intubation, a formula such as INT-P = 0.67 + 0.974 x (LOC-P) was developed using statistical methods. Hemodynamic deterioration identified during intubation was observed in 53.9% and additional interventions were needed to manage them. Conclusions: It was concluded that LOC, which is a clinical finding, can be used as an alternative guide for estimating the depth of anesthesia in cases when inducing anesthesia with HKI systems. KeyWords: Target controlled infusion, Intravenous anesthesia, Bispectral index