The median effective intubation concentration of sevoflurane in patients undergoing ultrasound-guided internal branch of superior laryngeal nerve block combined with airway topical anesthesia

Abstract

Objective To compare the median effective intubation concentration of sevoflurane in patients undergoing ultrasound-guided internal branch of superior laryngeal nerve(iSLN) block combined with or without airway topical anesthesia. Methods Ninety-six patients, ASA Ⅰ or Ⅱ, BMI 18.5-24.9 kg/m2, scheduled for selective surgery under general anesthesia with tracheal intubation. Patients were randomly assigned into 2 groups in which received ultrasound-guided iSLN block combined with or without airway topical anesthesia. Thereafter, patients were randomly assigned into 4 subgroups in which received tracheal intubation by Airtraq under 0.7, 1.0, 1.4, or 2.0 MAC sevoflurane by block randomization respectively. SBP, DBP, and HR before intubation to 5 min were recorded. An increase of more than 30% baseline of SBP and/or HR during the period was considered as clinical significant. The non-line fit model was performed to build the dose-effect curve. Based on the dose-effect curve, intubation EC50 and their 95%CI in 2 groups were calculated. Results Intubation 50% effective concentration(EC50) and 95% effective concentration(EC95) of sevoflurane in ultrasound-guided iSLN block group were 1.330 MAC (95%CI: 1.197-1.478) and 1.999 MAC respectively. The numbers in ultrasound-guided iSLN block combined with airway topical anesthesia group were 1.214 MAC (95%CI: 0.997-1.479) and 1.545 MAC. Conclusions Both ultrasound-guided iSLN block combined with and without airway topical anesthesia performed well in stress control in tracheal intuation. But the combination method has best effect. Key words: Internal branch of superior laryngeal nerve; Nerve block; Sevoflurance; Tracheal intubation; 50% effective concentration