Effect-site concentration of remifentanil for nasotracheal versus orotracheal intubation during target-controlled infusion of propofol

The effect-site concentration of remifentanil blunting endotracheal intubation responses during anesthesia induction with etomidate: a dose-finding study

BACKGROUND

Remifentanil can inhibit the hemodynamic responses caused by endotracheal intubation, but the effect-site concentration of it required to control intubation responses when combined with etomidate has not been demonstrated. The purpose of this study was to determine the effect-site concentration of remifentanil blunting tracheal intubation responses in 50% and 95% of patients (EC₅₀ and EC₉₅) during etomidate anesthesia.

METHODS

American Society of Anesthesiologists physical status (ASA) I-II elective surgical patients receiving target-controlled infusion (TCI) of remifentanil, followed by etomidate and rocuronium for anesthesia were enrolled. The Belive Drive A2 monitor was used to calculate the MGRSSI (Maygreen Sedative state index) of hypnotic effect and the MGRNOX (Maygreen Nociception index) of nociception. The MGRSSI and the MGRNOX value were generated every 1 s. Mean arterial pressure (MAP) and heart rate (HR) were measured every minute, noninvasively. Using the modified Dixon's up-and-down method, the concentration of remifentanil was determined based on the intubation response of the previous patient. The cardiovascular response during endotracheal intubation was defined as positive when MAP or HR is 20% higher than the pre-intubation value. A probit analysis was used for calculating EC₅₀, EC₉₅ and 95% confidence interval (CI).

RESULTS

The EC₅₀ and EC₉₅ of remifentanil blunting tracheal intubation responses were found to be 7.731 ng/ml (95%CI: 7.212-8.278 ng/ml) and 8.701 ng/ml (95%CI: 8.199-11.834 ng/ml). There were statistically significant increases in HR, MGRSSI and MGRNOX value to tracheal intubation in the positive responses group compared to the negative group. The most common adverse event was postoperative nausea and vomiting, which occurred in 3 patients.

CONCLUSION

Remifentanil effect-site concentration of 7.731 ng/ml is effective in blunting sympathetic responses to tracheal intubation in 50% of patients when combined with etomidate anesthesia.

TRIAL REGISTRATION

The trial was registered at the Chinese Clinical Trials Registry ( www.chictr.org.cn , registration number: ChiCTR2100054565, date of registration: 20/12/2021).

Optimal effect-site concentration of remifentanil to prevent hemodynamic changes during nasotracheal intubation using a video laryngoscope

Background

Nasotracheal intubation is the most commonly used method to secure the field of view when performing surgery on the oral cavity or neck. Like orotracheal intubation, nasotracheal intubation uses a laryngoscope. Hemodynamic change occurs due to the stimulation of the sympathetic nervous system. Recently, video laryngoscope with a camera attached to the end of the direct laryngoscope blade has been used to minimize this change. In this study, we investigated the optimal effect-site concentration (Ce) of remifentanil for minimizing hemodynamic responses during nasotracheal intubation with a video laryngoscope.

Methods

Twenty-one patients, aged between 19 and 60 years old, scheduled for elective surgery were included in this study. Anesthesia was induced by slowly injecting propofol. At the same time, remifentanil infusion was initiated at 3.0 ng/ml via target-controlled infusion (TCI). When remifentanil attained the preset Ce, nasotracheal intubation was performed using a video laryngoscope. The patient's blood pressure and heart rate were checked pre-induction, right before and after intubation, and 1 min after intubation. Hemodynamic stability was defined as an increase in systolic blood pressure and heart rate by 20% before and after nasotracheal intubation. The response of each patient determined the Ce of remifentanil for the next patient at an interval of 0.3 ng/ml.

Results

The Ce of remifentanil administered ranged from 2.4 to 3.6 ng/ml for the patients evaluated. The estimated optimal effective effect-site concentrations of remifentanil were 3.22 and 4.25 ng/ml, that were associated with a 50% and 95% probability of maintaining hemodynamic stability, respectively.

Conclusion

Nasotracheal intubation using a video laryngoscope can be successfully performed in a hemodynamically stable state by using the optimal remifentanil effect-site concentration (Ce₅₀, 3.22 ng/ml; Ce₉₅, 4.25 ng/ml).

Effect-site concentrations of remifentanil causing bradycardia in hypnotic and non-hypnotic patients

Although the induction of anaesthesia with remifentanil often causes bradycardia, the relationship between the effect-site concentration (Ce) of remifentanil and instantaneous heart rate (HR) has remained unclear. The present study examined the relationship between instantaneous HR and remifentanil Ce at the induction of anaesthesia with and without propofol hypnosis, to facilitate safe management of anaesthesia induction with remifentanil. Instantaneous HR was calculated every 5 s using an electrocardiographic real-time analysis system (MemCalc/Makin2; GMS, Tokyo, Japan). At the beginning of anaesthesia induction, continuous infusion of remifentanil (1 μg min^-1 kg^-1) preceded hypnosis with propofol in 13 patients [non-hypnosis group; mean age, 67.8 (17.5) years], while propofol bolus (30-50 mg) was injected together with continuous remifentanil medication in 18 patients [hypnosis group; mean age, 62.9 (16.5) years]. Remifentanil Ce was estimated every 5 s using the three-compartment model proposed by Minto et al. and the relationship between estimated remifentanil Ce and instantaneous HR was examined. In the hypnosis group, HR was significantly lower than basal HR when remifentanil Ce was increased to 3.5 ng ml^-1 (p < 0.05), whereas no significant HR reduction was found in the non-hypnosis group until remifentanil Ce reached >5 ng ml^-1 (p < 0.05). The induction of anaesthesia using remifentanil with propofol hypnotics significantly reduces HR even in a low remifentanil Ce insufficient to suppress the cardiovascular response at tracheal intubation. Preparations to treat bradycardia are recommended for the safe management of anaesthesia induction when remifentanil is combined with hypnotics.

Are muscle relaxants needed for nasal intubation in propofol and remifentanil anesthesia?

PURPOSE

The authors hypothesized that a muscle relaxant would have no meaningful difference in intubation conditions during nasal intubation under remifentanil and propofol anesthesia.

MATERIALS AND METHODS

This parallel-group, double-blinded, randomized controlled trial included 44 patients who received saline (S group; n = 22) or rocuronium (R group; n = 22). In addition to remifentanil 0.5 μg/kg per minute and propofol 5 mg/kg per hour, propofol 0.5 mg/kg was administered until loss of consciousness. Nasal intubation was performed 10 minutes after administration of R or S 0.6 mg/kg. Significant differences in intubation conditions and salivary amylase levels before and after intubation were tested (P < .05).

RESULTS

Vocal cord status (P = .003) and response to intubation or cuff filling (P = .008) were significantly different, but intubation conditions were not. Salivary amylase level was significantly lower with R administration (P = .022). No patient complained of postoperative throat pain and hoarseness.

CONCLUSION

Muscle relaxants during nasal intubation performed after bolus administration of propofol 0.9 mg/kg in addition to 10 minutes of remifentanil 0.5 μg/kg per minute plus propofol 5 mg/kg per hour are unnecessary.

Hemodynamic effects of topical lidocaine on the laryngoscope blade and trachea during endotracheal intubation: a prospective, double-blind, randomized study

PURPOSE

Minimizing hemodynamic changes during the peri-intubation period is a concern for anesthesiologists. We investigated the effect of lidocaine sprayed on the laryngoscope blade and trachea on hemodynamics during direct laryngoscopic intubation.

METHODS

Seventy-two patients were randomly allocated to one of four groups: 10% lidocaine was sprayed either on the laryngoscope blade (group L), on the trachea (group V), or on the laryngoscope blade and the trachea (group LV). No lidocaine was used in group C. Anesthesia was induced in all patients with remifentanil (effect site concentration: 4.0 ng/ml) and propofol (effect site concentration 4.0 μg/ml) continuous infusion using a target control infusion (TCI) device. Mean arterial pressure (MAP) and heart rate (HR) were recorded during the peri-intubation period.

RESULTS

Changes in MAP and HR over time were markedly different among the four groups (P < 0.05). MAP at 1 min post-intubation was significantly lower in groups L, V, and LV than in group C (86.1 ± 12.7, 85.3 ± 12.6, and 83.7 ± 13.1 vs. 106.3 ± 22.9 mmHg, P < 0.01). Maximum MAP values were lower in groups L and LV than in group C (P < 0.05). HRs at 1, 2, and 3 min post-intubation were lower in group LV than in group C (70.4 ± 9.0 vs. 84.2 ± 15.3; 64.0 ± 8.1 vs. 79.2 ± 15.4; 61.6 ± 8.3 vs. 77.2 ± 14.5 beats/min, P < 0.01, respectively).

CONCLUSIONS

Lidocaine sprayed on the laryngoscope blade and/or trachea reduced the hemodynamic response to laryngoscopic intubation during the post-intubation period following anesthetic induction with remifentanil and propofol using a TCI device.