Effects of small-dose remifentanil combined with index of consciousness monitoring on gastroscopic polypectomy: a prospective, randomized, single-blinded trial

BACKGROUND: With the development of painless diagnosis and treatment, remifentanil, a synthetic opioid agonist, is increasingly used in gastroscopy for its rapid, short-term, and potent analgesic effect. However, the dosage of remifentanil used in endoscopy is unclear. Index of consciousness (IOC) is a new anesthesia depth-monitoring indicator that can be divided into index of consciousness 1 (IOC(1)) and index of consciousness 2 (IOC(2)); IOC(1) is used for estimating a patient’s sedation state, whereas IOC(2) reflects analgesic depth. We hypothesized that combining with IOC(1) and IOC(2) monitoring may be helpful to identify an optimal remifentanil dosage in gastroscopic polypectomy. METHODS: One hundred twenty patients scheduled for gastroscopic polypectomy were enrolled and were randomly assigned to remifentanil 2 ng/mL (group R2), 4 ng/mL (group R4), or 6 ng/mL (group R6), and 40 cases were in each group. During the anesthesia period, remifentanil was kept at the initial given concentration but propofol was adjusted according to IOC(1). The primary outcomes were the dosage of propofol and remifentanil. The secondary outcomes were the variety of IOC(1) and IOC(2), patients’ awakening time, and peri-operative adverse reactions such as hypotension, hypertension, bradycardia, tachycardia, body movements, hypoxemia, therapy interruption, nausea, vomiting, aspiration, and intra-operative awareness. RESULTS: With the increasing dosage of remifentanil, the propofol dosage and patients’ awakening time decreased significantly, the morbidity of hypertension and body movements also declined, but the incidence of hypotension, bradycardia, and hypoxemia rose. In group R2, the value of IOC(2) remained above 50 during the treatment. However, IOC(2) dropped to below 30 at the beginning of the gastroscopy in group R6, and there was statistical difference in hypoxemia between groups R2 and R6 (P <0.05). CONCLUSIONS: With the help of IOC monitoring, we found that a target concentration of remifentanil 4 ng/mL is comparatively ideal in patients under gastroscopic polypectomy. TRIAL REGISTRATION: Chinese Clinical Trial Register: ChiCTR-OOD-16009489, on October 19, 2016.