Determining the optimum dose of remifentanil in combination with propofol for total intravenous anaesthesia in hysteroscopy under Narcotrend and SPI monitoring.

BACKGROUND

Outpatient hysteroscopic surgery requires patients to be anaesthetised and recover quickly, and the drugs used must be safe and effective. Remifentanil is typically co-administered with propofol as total intravenous anaesthesia (TIVA) for hysteroscopy because of its favourable pharmacokinetic and pharmacodynamic properties. However, the optimal dose of remifentanil when co-administered with propofol without neuromuscular blocking agents (NMBAs) has not been established.

OBJECTIVES

In this sequential dose-finding study, the 90% effective dose (ED90) of remifentanil effect-site concentration (Ce) combined with propofol without NMBAs during outpatient hysteroscopy was calculated to minimise the side effects of using higher doses.

DESIGN

This sequential dose-finding study was conducted in August 2022.

METHODS

Forty patients who underwent outpatient hysteroscopy under TIVA were included in the study. With a biased coin up-and-down design, the initial remifentanil Ce was established at 2 ng/mL, and the subsequent remifentanil dosage was determined based on the reaction of the previous patient. The primary outcome was a remifentanil Ce that resulted in successful TIVA by maintaining a Narcotrend index < 60, surgical pleth index (SPI) < 50, and without patient movement throughout hysteroscopy. Secondary outcomes included rates of hypotension-related symptoms and interventions, drug consumption, post-anaesthesia care unit (PACU)-estimated visual analogue scale (VAS) and Ramsay sedation scores, modified Aldrete scores, and other adverse effects of anaesthesia. The ED90 and 95% confidence intervals (CI) were estimated using isotonic regression methods and bootstrapping.

RESULTS

For TIVA without NMBAs during outpatient hysteroscopy, the ED90 Ce of remifentanil combined with propofol was determined to be 2.75 ng/mL (95% CI, 2.50-3.00 ng/mL). The incidence of peri-operative adverse effects of anaesthesia was relatively low. All the patients had satisfactory VAS, Ramsay sedation, and modified Aldrete scores in the PACU.

CONCLUSION

Remifentanil at a Ce of 2.75 ng/mL is recommended for TIVA combined with propofol in outpatient hysteroscopic surgery.

TRIAL REGISTRATION: http://www.chictr.org.cn (ChiCTR2200062284; 31/7/2022).