Inhibition of Stress and Spontaneous Respiration: Efficacy and Safety of Monitored Anaesthesia Care by Remifentanil in Fibreoptic Bronchoscopy for Patients with Severe Tracheal Stenosis
Authors: Zhou Yi , Wu Wei , Zhu Yuanjie , Shi Lingli , Lv Xin , Liu Jianming 
Published: August 2021

Abstract
Objective To determine the effective concentration of target-controlled infusion (TCI) of remifentanil used to inhibit stress during the treatment of severe tracheal stenosis with fibreoptic bronchoscopy and to evaluate the safety of the monitored anaesthesia care (MAC) by remifentanil.Methods A study of 60 patients with severe tracheal stenosis who underwent diagnostic and therapeutic fibreoptic bronchoscopy at Shanghai Pulmonary Hospital affiliated with Tongji University was performed. Dexmedetomidine was initially administered at a bolus dose (0.8 mcg/kg), followed by a 0.5 mcg/(kg·h) continuous infusion. Remifentanil was administered by TCI. When the target concentration was reached, the nasopharyngeal airway was inserted, and then oxygen was supplied by a connected anaesthesia machine. The effective concentration of remifentanil was titrated by the improved sequential method, and 30 patients were included. The EC95 of remifentanil was set as the plasma target concentration to evaluate the safety of the MAC, and another 30 patients were included. Remedy measures: Propofol (10-20 mg) was injected intravenously. The primary outcome measures were the cough score and the incidence and severity of hypoxemia. The tolerance score for nasopharyngeal airway placement, Ramsay sedation score, haemodynamic changes, satisfaction score, patients’ 24 h recall score, patients’ willingness to re-receive the procedure, and related adverse events were recorded.Results On the basis of sedation with dexmedetomidine, the EC95 of remifentanil for inhibiting the stress response in fibreoptic bronchoscopy performed on patients with severe tracheal stenosis was 2.710 ng/ml (95% CI, 2.471-4.473 ng/ml), and the EC50 was 2.243 ng/ml (95% CI, 2.061-2.446 ng/ml). Among the 30 patients who received an EC95 of remifentanil as the target concentration, 1 patient was remedied by injecting propofol; the tolerance score for insertion of the nasopharyngeal airway was 2, the score of Ramsay sedation was 3, and the cough score was 1. The incidence of respiratory depression was 50%, the incidence of hypoxemia was 20%, and 86.7% of patients with respiratory depression returned to normal by awakening. One patient returned to normal by mask-assisted ventilation, and another returned to normal by laryngeal mask mechanical ventilation. The satisfaction score of the operator was 9, the satisfaction score of the anaesthesiologist was 8, the satisfaction score of the patients was 10, the score of the patients' 24 h operative recall was 1, the rate of patient willingness to re-accept the procedure was 93.3%, the incidence of throat pain at 30 min after the end of the operation was 16.7%, and the circulation was stable during the operation. No pruritus, nausea, vomiting or other related adverse reactions were reported.Conclusion MAC using TCI of remifentanil can effectively inhibit the stress response to fibreoptic bronchoscopy in patients with severe tracheal stenosis while maintaining spontaneous breathing. The patients are safe and comfortable and express high satisfaction, making this method worthy of clinical application.Trial registration Registration date : 12/02/2021, Registration number: ChiCTR2100043380.