Predicted EC₅₀ and EC₉₅ of Remifentanil for Smooth Removal of a Laryngeal Mask Airway Under Propofol Anesthesia

Effect of sex differences in remifentanil requirements for inhibiting the response to a CO2 pneumoperitoneum during propofol anesthesia: an up-and-down sequential allocation trial

Background

A CO₂ pneumoperitoneum during a laparoscopic procedure causes violent hemodynamic changes. However, the remifentanil required to inhibit the cardiovascular response to a CO₂ pneumoperitoneum combined with propofol remains unknown. Moreover, the sex of the patient may influence the response to opioids, which can affect this requirement. The main objective of this study was to compare the required median effective concentration (EC₅₀) of remifentanil for inhibiting the cardiovascular response to a CO₂ pneumoperitoneum between female and male patients during propofol anesthesia.

Methods

The current study is an up-and-down sequential allocation trial. Forty-six patients with American Society of Anesthesiologists physical status I or II, a body mass index 18 to 30 kg/m², aged 20 to 60 years, and scheduled for laparoscopic surgery were enrolled. Induction of anesthesia was performed by target-controlled infusion. The effective effect-site concentration (Ce) of propofol was 4 μg/ml. The Ce of remifentanil was initially 4 ng/ml and then adjusted to a predetermined level after I-gel laryngeal mask airway insertion. The Ce of remifentanil for each patient was determined by the response of the previous patient using the modified Dixon “up-and-down” method. The first patient received remifentanil at 5.0 ng/ml Ce, and the step size between patients was 0.5 ng/ml.

Results

Patients characteristics including age, body mass index, American Society of Anesthesiologists physical status, type of surgery and surgery duration, were comparable between male and female patients. The EC₅₀ of remifentanil required to inhibit the response to a CO₂ pneumoperitoneum based on the Dixon “up-and-down” method in women (4.17 ± 0.38 ng/ml) was significantly lower than that in men (5.00 ± 0.52 ng/ml) during propofol anesthesia (P = 0.01).

Conclusions

The EC₅₀ of remifentanil required to inhibit the response to a CO₂ pneumoperitoneum was lower in women than in men during propofol anesthesia.

Trial registration

The study was registered at http://www.chictr.org.cn (ChiCTR-IOR-17011906, 8th, July, 2017).

Removal of Laryngeal Mask Airway in Adults Under Target-Controlled, Propofol-Fentanyl Infusion Anesthesia: Awake or Deep Anesthesia?

After emergence from anesthesia, the incidence and severity of adverse airway effects caused by the laryngeal mask airway (LMA) can vary, depending on when the device was removed; nonetheless, reports differ regarding the exact optimal timing of LMA removal. The purpose of this study was to compare the rate of adverse events between 2 groups: those whose LMA was removed under general anesthesia ("deep" group) or under target-controlled infusion (TCI) of propofol ("awake" group).Institutional Review Board approval and written informed consent were obtained; 124 patients were then randomly allocated into either the "awake" group or the "deep" group. Anesthesia was induced and maintained using TCI of propofol, as well as intravenous fentanyl. In the "deep" group, the LMA was removed after surgery while the patients were deeply anesthetized using a target effect-site propofol concentration of 2 μg/mL, whereas in the "awake" group, the device was removed while the patients followed verbal instructions. The incidence of the following adverse events was recorded: coughing, straining, bronchospasm, laryngospasm, clenching, breath holding, gross purposeful movement, airway obstruction, retching, vomiting, and oxygen desaturation. If any such event occurred, the LMA removal was considered a failure. Airway hyperreactivity was recorded and graded - based on the severity of cough, breath holding, and oxygen desaturation.The failure rate was higher in the "awake" group (15/61; 24.6%) than in the "deep" group (5/60; 8.3%). Airway hyperreactivity was mild (score, <3) in both groups.Removal of the LMA under deep anesthesia using a target-controlled, effect-site propofol concentration of 2 μg/mL may be safer and more successful than removal when patients are fully awake after surgery.