The effect of remifentanil on propofol requirements to achieve loss of response to command vs. loss of response to pain

Electroencephalographic Indices for Clinical Endpoints during Propofol Anesthesia in Infants: An Early-phase Propofol Biomarker-finding Study

BACKGROUND

Unlike expired sevoflurane concentration, propofol lacks a biomarker for its brain effect site concentration, leading to dosing imprecision particularly in infants. Electroencephalography monitoring can serve as a biomarker for propofol effect site concentration, yet proprietary electroencephalography indices are not validated in infants. The authors evaluated spectral edge frequency (SEF95) as a propofol anesthesia biomarker in infants. It was hypothesized that the SEF95 targets will vary for different clinical stimuli and an inverse relationship existed between SEF95 and propofol plasma concentration.

METHODS

This prospective study enrolled infants (3 to 12 months) to determine the SEF95 ranges for three clinical endpoints of anesthesia (consciousness-pacifier placement, pain-electrical nerve stimulation, and intubation-laryngoscopy) and correlation between SEF95 and propofol plasma concentration at steady state. Dixon's up-down method was used to determine target SEF95 for each clinical endpoint. Centered isotonic regression determined the dose-response function of SEF95 where 50% and 90% of infants (ED50 and ED90) did not respond to the clinical endpoint. Linear mixed-effect model determined the association of propofol plasma concentration and SEF95.

RESULTS

Of 49 enrolled infants, 44 evaluable (90%) showed distinct SEF95 for endpoints: pacifier (ED50, 21.4 Hz; ED90, 19.3 Hz), electrical stimulation (ED50, 12.6 Hz; ED90, 10.4 Hz), and laryngoscopy (ED50, 8.5 Hz; ED90, 5.2 Hz). From propofol 0.5 to 6 μg/ml, a 1-Hz SEF95 increase was linearly correlated to a 0.24 (95% CI, 0.19 to 0.29; P < 0.001) μg/ml decrease in plasma propofol concentration (marginal R2 = 0.55).

CONCLUSIONS

SEF95 can be a biomarker for propofol anesthesia depth in infants, potentially improving dosing accuracy and utilization of propofol anesthesia in this population.

EDITOR’S PERSPECTIVE

Effect of remifentanil on three effect-site concentrations of propofol and their relationship during electroencephalography at loss of response, at maximum alpha power, and at onset of burst suppression: a prospective randomized trial

PURPOSE

The effect-site concentration (Ce) at loss of response (Ce-LOR) to propofol closely correlates both with Ce as electroencephalographic alpha power becomes highest (Ce-alpha) and with Ce at onset of burst suppression (BS) (Ce-OBS), when no opioids are administered. Co-administration of opioids dose-dependently decreases Ce-LOR. We investigated the influence of remifentanil on the relationship between these three Ces.

METHODS

After receiving approval from our local ethical committee, with written informed consent, we enrolled 90 participants (ASA-PS I or II) who were scheduled for elective surgery. Participants were randomly assigned to three groups: constant remifentanil Ce 0 ng/ml (Remi_0); 1 ng/mL (Remi_1); and 2 ng/mL (Remi_2). We recorded both raw EEG and EEG-derived parameters on a computer. After reaching remifentanil equilibrium, we administered propofol using a target-controlled infusion pump such that propofol Ce increased to about 0.3 μg/mL/min. After determining Ce-LOR, we administered 0.6 mg/kg of rocuronium and started mask ventilation. The study protocol ended after observation of BS.

RESULTS

Three participants were excluded. Ce-LOR in each group (Remi_0, Remi_1, Remi_2) was 2.00 ± 0.58 μg/mL, 1.43 ± 0.49 μg/mL, and 1.37 ± 0.42 μg/mL. Ce-alpha was 2.91 ± 0.63 μg/mL, 2.30 ± 0.41 μg/mL, and 2.12 ± 0.39 μg/mL. Ce-OBS was 3.80 ± 0.69 μg/mL, 3.25 ± 0.68 μg/mL, and 2.90 ± 0.57 μg/mL. In three other instances, Ce was decreased by remifentanil. Generalized linear model analysis revealed that remifentanil had no influence on the relationship between the three Ces.

CONCLUSION

During propofol anesthesia, even low concentrations of remifentanil shifted concentration-related electroencephalographic changes.

Haemodynamic effects of remifentanil during induction of general anaesthesia with propofol. A randomised trial

BACKGROUND

Remifentanil may have a dose-dependent haemodynamic effect during the induction of general anaesthesia combined with propofol. Our objective was to investigate whether systolic arterial blood pressure (SAP) was reduced to a greater extent when the remifentanil dose was increased.

METHODS

This randomised, double-blind, dose-controlled study was conducted at the Day Surgery Unit of Haugesund Hospital, Norway. Ninety-nine healthy women scheduled for gynaecological surgery were randomly allocated in a 1:1:1 ratio to receive remifentanil induction with a low, medium or high dose corresponding to maximum effect-site concentrations (Ce) of 2, 4 and 8 ng/mL. The induction dose of propofol was 1.8 mg/kg, with a Ce of 2.9 μg/mL. Anaesthesia was induced using target-controlled infusion. After 150 s of sedation, a bolus of remifentanil and propofol was administered. Baseline was defined as 55-5 s before the bolus dose, and the total observation time was 450 s. We used beat-to-beat haemodynamic monitoring with LiDCOplus. The primary outcome variable was the maximum decrease in SAP within 5 min after bolus administration of remifentanil and propofol. Absolute and relative changes from baseline to minimal values and the area under the curve (AUC) were used as effect measures. Comparisons of groups were performed using analysis of variance (ANOVA).

RESULTS

Median remifentanil doses were 0.75, 1.5 and 3.0 μg/kg in the low-, medium- and high-dose groups, respectively. The absolute changes (mean ± standard deviation) in SAP in the low-, medium- and high-dose groups of remifentanil were -39 ± 9.6 versus -43 ± 9.1, and -41 ± 10 mmHg, respectively. No difference (95% confidence interval) in the absolute change in SAP was observed between the groups (ANOVA, p = .29); medium versus low dose 3.7 (-2.0, 9.4) mmHg, and high versus medium dose -2.2 (-8.0; 3.5) mmHg. The relative changes from baseline to minimum SAP values were -30% versus -32% versus -32% (p = .52). The between-group differences in the AUC were not statistically significant. Relative changes in heart rate (-20% vs. -21% vs. -21%), stroke volume (-19% vs. -16% vs. -16%), cardiac output (-32% vs. -32% vs. -32%), systemic vascular resistance (-24% vs. -27% vs. -28%), and AUC were not statistically significant.

CONCLUSION

This trial demonstrated major haemodynamic changes during the induction of anaesthesia with remifentanil and propofol. However, we did not observe any statistically significant differences between low, medium or high doses of remifentanil when using continuous invasive high-accuracy beat-to-beat monitoring.

Effective dose of remimazolam co-administered with remifentanil to facilitate I-gel insertion without neuromuscular blocking agents: an up-and-down sequential allocation trial

BACKGROUND

Remimazolam is a new anesthetic drug developed and is an ultra-short-acting agent with rapid onset and offset. The pharmacology of this drug seems to be ideal for short surgeries eligible for I-gel insertion. Therefore, this study aimed to determine the optimal bolus dose of remimazolam for I-gel insertion when co-administered with remifentanil without neuromuscular blocking agents (NMBAs).

METHODS

Patients aged 19-65 years with American Society of Anesthesiologists physical status I or II scheduled for general anesthesia were enrolled. The first dose of remimazolam was 0.15 mg/kg and remifentanil was co-administered at an effect-site concentration (Ce) of 3.0 ng/mL. The dose of remimazolam for the following patient was decreased or increased by 0.05 mg/kg depending on the success or failure of I-gel insertion in the previous patient.

RESULTS

The remimazolam bolus dose required for successful I-gel insertion in 50% of adult patients using modified Dixon's up-and-down method with remifentanil Ce 3.0 ng/mL and no NMBAs was 0.280 ± 0.048 mg/kg. Isotonic regression analysis showed that the 50% and 95% effective doses were 0.244 (83% confidence interval [CI] 0.213-0.313) mg/kg and 0.444 (95% CI 0.436-0.448) mg/kg, respectively. The mean time to loss of consciousness (Modified Observer's Assessment of Alertness/Sedation score < 2) was 52.2 s. Three patients (12.0%) showed a reduction in systolic blood pressure of more than 30% from baseline.

CONCLUSIONS

Selecting the appropriate dose of remimazolam/remifentanil without NMBAs makes it feasible to insert the I-gel.

TRIAL REGISTRATION

This study protocol was registered at http://cris.nih.go.kr (KCT0007801, 12th, October, 2022).

Alternatives to remifentanil for the analgesic component of total intravenous anaesthesia: a narrative review

Propfol-remifentanil-based total intravenous anaesthesia has dominated recent clinical practice due to its favourable pharmacokinetic profile. Interruption in remifentanil supply has presented an opportunity to diversify or even avoid the use of opioids and consider adjuncts to propofol-based total intravenous anaesthesia. Propofol, while a potent hypnotic, is not an effective analgesic. The administration of opioids, along with other adjuncts such as α-2 adrenoceptor agonists, magnesium, lidocaine, ketamine and nitrous oxide provide surgical anaesthesia and avoids large doses of propofol being required. We provide an overview of both target-control and manual infusion regimes for the alternative opioids: alfentanil, sufentanil and fentanyl. The optimal combination of hypnotic-opioid dose, titration sequence and anticipated additional postoperative analgesia required depend on the chosen combination. In addition, we include a brief discussion on the role of non-opioid adjuncts in total intravenous anaesthesia, suggested doses and expected reduction in propofol dose.

A comparative study on the efficacy and safety of propofol combined with different doses of alfentanil in gastroscopy: a randomized controlled trial

PURPOSE

Propofol can be used alone or in combination with opioids during gastroscopy. This study aimed to assess the efficacy and safety of intravenous propofol and different doses of alfentanil in patients undergoing gastroscopy.

METHODS

A total of 300 patients undergoing sedative gastroscopy were randomly divided into four groups, and 0.9% saline (group A), 2 μg/kg alfentanil (group B), 3 μg/kg alfentanil (group C) or 4 μg/kg alfentanil (group D) were injected intravenously 1 min before the intravenous injection of 1.5 mg/kg propofol. If body movement and coughing occurred during the procedure, 0.5 mg/kg propofol would be administered intravenously. The primary outcome (awakening time) and secondary outcomes were recorded and analyzed, including hemodynamic changes, the incidences of body movement, coughing, hypoxemia, hypotension, hypertension, bradycardia, tachycardia, nausea and vomiting, drowsiness and dizziness.

RESULTS

Patients in group C (7.0 [5.0 to 8.0] min) and group D (6.0 [5.0 to 7.0] min) woke up significantly earlier than those in group A (8.0 [6.0 to 10.0] min) (P < 0.001). Patients in group A experienced more body movement (P = 0.001) and coughing (P < 0.001) than the other groups. With the increasing dose of alfentanil, the morbidity of hypotension and bradycardia increased significantly (P = 0.001), while the incidence of dizziness decreased significantly (P = 0.037). The incidences of hypoxemia, tachycardia, drowsiness, nausea and vomiting were similar among the four groups (P > 0.05).

CONCLUSIONS

Intravenous 1.5 mg/kg propofol combined with 3 μg/kg alfentanil is more suitable for patients undergoing gastroscopy, and the dose of alfentanil can be reduced according to the patient's actual physical condition.

Carbon footprint of inhalational and total intravenous anaesthesia for paediatric anaesthesia: a modelling study

BACKGROUND

Tackling the climate emergency is now a key target for the healthcare sector. Avoiding inhalational anaesthesia is often cited as an important element of reducing anaesthesia-related emissions. However, evidence supporting this is based on adult practice. The aim of this study was to identify the difference in carbon footprint of inhalational and i.v. anaesthesia when used in children.

METHODS

We used mathematical simulation models to compare general anaesthetic techniques in children weighing 5-50 kg for TIVA, i.v. induction then inhalational maintenance, inhalational induction then i.v. maintenance, and inhalational induction and maintenance. We simulated inhalational induction with sevoflurane alone, and co-induction with sevoflurane and nitrous oxide, and both remifentanil-propofol and propofol-only i.v. anaesthesia. For each technique, we drew on previously published life-cycle data to calculate carbon dioxide equivalents for anaesthetic durations up to 480 min.

RESULTS

TIVA with propofol and remifentanil had a smaller carbon footprint over a typical anaesthetic duration of 60 min (1.26 kg carbon dioxide equivalents [CO₂e] for a 20 kg child) than i.v. induction followed by inhalational maintenance (2.58 kg CO₂e) or inhalational induction and maintenance (2.98 kg CO₂e). Inhalational induction followed by i.v. maintenance only had a lower carbon footprint than inhalational induction and maintenance when used in longer procedures (>77 min for children 5-20 kg; >105 min for children 30-50 kg).

CONCLUSIONS

In a simulation study, i.v. anaesthesia had climate benefits in paediatric anaesthesia. However, when used after inhalational induction, benefits were only achieved in longer procedures. These findings provide evidence-based guidance for reducing the environmental impact of paediatric anaesthesia, but these will require confirmation using real-world data.

Effect of dexamethasone on intraoperative remifentanil dose in total knee arthroplasty surgery under general anaesthesia

Background

The effects of glucocorticoids may include both genomic and rapid nongenomic effects. The potential rapid analgesic effect during surgery has not previously been investigated. We aimed to explore the effect of dexamethasone on intraoperative infusion rate of remifentanil in patients undergoing total knee arthroplasty (TKA) surgery under general anaesthesia.

Methods

In this post hoc subgroup analysis, we included patients randomised in the DEX‐2‐TKA trial, who were operated under total intravenous anaesthesia with remifentanil and propofol. Trial medication, intravenous dexamethasone 24 mg or placebo, was administered immediately after anaesthesia onset. The primary outcome was the median weight‐corrected infusion rate of remifentanil during surgery. Secondary outcomes included median weight‐corrected infusion rate of propofol, median intraoperative bispectral index and time spent in the post‐anaesthesia care unit.

Results

Eighty‐seven patients were included in the analysis of the primary outcome. A significantly higher remifentanil infusion rate was observed in the dexamethasone group compared with the placebo group, p = .02. None of the secondary outcomes resulted in statistically significant differences between groups.

Conclusion

This explorative post hoc analysis of the randomised DEX‐2‐TKA trail showed that patients undergoing TKA surgery under general anaesthesia and who received dexamethasone seemed to have a higher remifentanil infusion rate compared with patients who received placebo. The clinical implications of the potentially increased remifentanil infusion rate need to be validated and explored further.

Clinical trial registration

ClinicalTrials.gov Identifier: NCT05002361 (12 August 2021).

Changes of Entropy Index and Cerebral Oxygen Metabolism in the Maintenance of Remifentanil Anesthesia and Their Predictive Value for Postoperative Hyperalgesia

Objective

To explore the changes of entropy index and cerebral oxygen metabolism in the maintenance of remifentanil anesthesia and the predictive value of postoperative hyperalgesia.

Methods

A total of 266 patients undergoing general anesthesia in our hospital from January 2020 to October 2021 were selected, and remifentanil was used to maintain anesthesia. The state entropy, reaction entropy, and cerebral oxygen metabolism indexes (cerebral oxygen uptake rate (CERO₂), arterial-venous blood oxygen difference (Da-jvO₂)) of patients before induction of anesthesia, 15 minutes during the operation, and at the end of the operation were compared. The influencing factors of postoperative hyperalgesia were analyzed. The logistic regression model of postoperative hyperalgesia was established, and the value of entropy index and cerebral oxygen metabolism in predicting postoperative hyperalgesia was evaluated by drawing the receiver operating characteristic curve (ROC).

Results

The state entropy, response entropy, and CERO₂ at 30 min during the operation and at the end of the operation were lower than those before the induction of anesthesia, and Da-jvO₂ was higher than that before the induction of anesthesia (P < 0.001). At the end of the operation, the state entropy, reaction entropy, and CERO₂ were higher than 30 minutes during the operation, and Da-jvO₂ was lower than 30 minutes during the operation (P < 0.001). The dosage of remifentanil, reaction entropy, and CERO₂ at the end of the operation entered the logistic model. The AUC value of the reaction entropy and CERO₂ combined to predict postoperative hyperalgesia at the end of the operation was 0.851 greater than the reaction entropy at the end of the operation (χ² = 3.847, P = 0.036), CERO₂ (χ² = 2.589, P = 0.010) single index predictive value.

Conclusion

The entropy index and cerebral oxygen metabolism in general anesthesia patients change with the progress and discontinuation of remifentanil maintenance anesthesia, and the combination of the two has a high predictive power in postoperative hyperalgesia risk assessment. When the reaction entropy > 54.23, CERO₂ > 34.14%, or the total dosage of remifentanil ≥ 30 μg/kg at the end of the operation, we should be highly vigilant of the occurrence of postoperative hyperalgesia and postoperative analgesia management should be strengthened.

Different perspectives for monitoring nociception during general anesthesia

Safe anesthesia is achieved using objective methods that estimate the patient’s state during different phases of surgery. A patient’s state under anesthesia is characterized by three major aspects, which are linked to the main effects produced by each of the families of anesthetic agents administered: hypnosis, analgesia, and muscular relaxation.

While quantification techniques designed to assess muscular relaxation under neuromuscular blocking agents have a relatively long history with a high degree of standardization and understanding (e.g., the train-of-four), the knowledge and techniques used to the depth of hypnosis assessment suffer from a lesser degree in both standardization and interpretation due to brain complexity.

The problem of standardization and interpretation in the analgesia and nociception assessment increases since it involves more systems, the central nervous system, and the autonomic nervous system.

This helps to explain why there are multiple a priori valid approaches to develop nociception monitoring from different interpretations and physiological bases of noxious stimuli processing. Thus, in this review, the current monitoring technologies clinically available for estimating a patient’s nociception under general anesthesia are described.

Clinical efficacy of intravenous anesthesia on breast segmental surgery and its effects on oxidative stress response and hemodynamics of patients

This study was designed to investigate the clinical efficacy of intravenous anesthesia on breast segmental surgery and the effects on hemodynamics of patients. A total of 267 patients were collected as research subjects. These patients underwent breast segmental surgery in Chun'an First People's Hospital from March 2015 to September 2018. Among them, 137 patients undergoing intravenous anesthesia were the research group, and 130 patients undergoing inhalation anesthesia were the control group. The following parameters were recorded: Clinical efficacy, postoperative adverse conditions, hemodynamic indicators including systolic blood pressure (SBP), diastolic blood pressure (DBP) and heart rate (HR). Visual analogue scale (VAS) was used to observe the analgesic effect of the two groups, the mental state of patients in the two groups was observed by mini-mental state examination (MMSE) scoring method, and systemic evaluation was made by oxidative stress (OS) reaction indicators. The MMSE scores of the two groups decreased one day after surgery, but the score in the research group was higher than that in the control group (P<0.05). The levels of SBP and DBP at T1 and T2 in the control group were significantly higher than those in the research group (P<0.05). HR of research group at T1 and T2 was lower than that at T0 and that at corresponding time of control group (P<0.05). The incidence rate of postoperative adverse reactions in the research group was significantly lower than that in the control group (P<0.05). In conclusion, intravenous anesthesia for breast segmental surgery can reduce the occurrence of adverse reactions after surgery, with complete sedation and analgesia. Patients were able to wake up quickly and stably after surgery, and their cognitive function and OS recovered rapidly. However, due to the great impact on hemodynamics during surgery, attention should be paid to maintain hemodynamic stability during surgery to avoid hypotension and bradycardia.

Impact of concurrent remifentanil on the sedative effects of remimazolam, midazolam and propofol in cynomolgus monkeys

Drug-drug interactions can substantially change pharmacological effects of the individual substances involved. For the use of sedatives or anaesthetics, having knowledge of the extent and characteristics of such interactions is crucial for ensuring the proper protection of patients undergoing any kind of sedation. Remimazolam is a new ultra-short acting benzodiazepine that is currently under development for intravenous use in procedural sedation and general anaesthesia. It exhibits a fast onset and fast offset which enables a more rapid recovery than currently available drugs in that class, such as midazolam. The purpose of this study was to more closely investigate the sedative properties and pharmacodynamic drug-drug interaction potential of remimazolam with the opioid analgesic remifentanil and compare it with other commonly used sedatives - midazolam and propofol. For this purpose, six Cynomolgus monkeys received escalating doses of remimazolam, propofol, and midazolam intravenously without or with concurrent remifentanil. Sedation was evaluated using a general sedation scale that included monitoring exploratory and avoidance behaviour, responses to sensory stimuli, posture and gait, and eyelid position as endpoints. Based on the results, sedative doses were calculated to allow evaluation of pharmacological drug-drug interaction with remifentanil. Remimazolam induced dose-dependent and consistent sedative effects in each endpoint tested and showed a high degree of synergism with remifentanil. Midazolam showed a comparable synergism while the interaction between propofol and remifentanil was less pronounced.

Volatiles or TIVA: Which is the standard of care for pediatric airway procedures? A pro-con discussion

Anesthesia for pediatric airway procedures constitutes a true art form that requires training and experience. Communication between anesthetist and surgeon to establish procedure goals is essential in determining the most appropriate anesthetic management. But does the mode of anesthesia have an impact? Traditionally, inhalational anesthesia was the most common anesthesia technique used during airway surgery. Introduction of agents used for total intravenous anesthesia (TIVA) such as propofol, short-acting opioids, midazolam, and dexmedetomidine has driven change in practice. Ongoing debates abound as to the advantages and disadvantages of volatile-based anesthesia versus TIVA. This pro-con discussion examines both volatiles and TIVA, from the perspective of effectiveness, safety, cost, and environmental impact, in an endeavor to justify which technique is the best specifically for pediatric airway procedures.

Influence of propofol-based total intravenous anaesthesia on peri-operative outcome measures: a narrative review

Propofol-based total intravenous anaesthesia is well known for its smooth, clear-headed recovery and anti-emetic properties, but there are also many lesser known beneficial properties that can potentially influence surgical outcome. We will discuss the anti-oxidant, anti-inflammatory and immunomodulatory effects of propofol and their roles in pain, organ protection and immunity. We will also discuss the use of propofol in cancer surgery, neurosurgery and older patients.

Remifentanil does not inhibit sugammadex reversal after rocuronium-induced neuromuscular block in the isolated hemidiaphragm of the rat: an ex vivo study

PURPOSE

Sugammadex is used to reverse neuromuscular block induced by rocuronium or vecuronium by forming a stable complex. If the binding capacity of any substance to sugammadex is large enough, this molecule will displace rocuronium or vecuronium from the complex. For drugs used in anesthesia, the binding affinity of remifentanil for sugammadex was highest. The aim of the current study was to investigate the decrease in the reversal of neuromuscular blockade with sugammadex by complex formation between remifentanil and sugammadex in the model using isolated hemidiaphragm of the rat.

METHODS

Phrenic nerve-hemidiaphragms from 34 male Sprague-Dawley rats were allocated randomly to four groups: 0 or 100 ng/ml remifentanil with equimolar amounts of sugammadex and 0 or 100 ng/ml remifentanil with three-quarter dose of sugammadex. Muscle contraction responses were recorded during the stimulation of the phrenic nerve by train-of-four (TOF) stimulation. Rocuronium was added to the organ bath with or without 100 ng/ml remifentanil until the first height response (T1) of TOF disappeared completely. Then, equimolar amounts or three-quarter dose of sugammadex was added.

RESULTS

Remifentanil has no significant effects on the concentration-response curves of rocuronium. No significant differences were observed in the recoveries of T1 and TOF ratio with time after administration of equimolar amounts or three-quarter dose of sugammadex regardless of the presence of 100 ng/ml remifentanil.

CONCLUSION

Clinical concentration of remifentanil does not inhibit sugammadex reversal after rocuronium-induced neuromuscular block. Sugammadex can be used safely without worrying about the interaction with remifentanil.

Application of remifentanil combined with propofol in the diagnosis of colon cancer with awakening painless digestive endoscopy

Anesthetic effect of remifentanil combined with propofol in awakening painless endoscopy was analyzed. Retrospective analysis of 120 cases of colon cancer were treated in Dongying People's Hospital from June 2015 to December 2017. All of them were treated by awakening painless digestive endoscopy, divided into 60 cases in observation group (combined with remifentanil and propofol anesthesia), and 60 cases in control group (combined intravenous anesthesia of finanib and propofol). The data were respectively recorded at time-points of oxygen inhalation, intubation for 10 min, awakening time, waking time, and the time-points for each represented as the time-points of T1, T2, T3, T4, T5 and recorded the diastolic blood pressure (DBP), respiratory rate (RR) and heart rate (HR), and compared the awakening effect and the occurrence of adverse reaction. There was no significant difference in the DBP index between the two groups at time-point T1 (P>0.05). The time-points of T2, T3, T4 and T5 were significantly different from the observation group (P<0.05). There was no significant difference in RR index between the two groups and between the same groups (P>0.05). Compared with the control group, the awakening time and consciousness recovering of the observation group is lower (P<0.05). The incidence of adverse reactions after awakening operation between the two groups was statistically significant (P<0.05). The local pain rate in the observation group after the awakening operation was lower than the control group. The combined use of trace remifentanil and small dose propofol in the awakening painless digestive endoscopy can make the patients with colon cancer more stable when they are in the awakening state, so as to improve the safety of awakening painless digestive endoscopy. It is worth promoting in clinical practice.

An International Survey Evaluating Factors Influencing the Use of Total Intravenous Anaesthesia

The purpose of this study was to evaluate factors influencing the use of propofol-based total intravenous anaesthesia (TIVA) since despite TIVA being a well-established technique, it is used far less frequently than volatile anaesthesia. Questions were formulated after reviewing the literature for perceived disadvantages of TIVA and meeting with a focus group consisting of both senior and junior anaesthestists from our department. Once the survey had been formulated, specialist anaesthetists from professional colleges and societies from several countries were invited to complete the survey on an electronic web-based platform to allow evaluation of the respondent's rating of the importance of a range of factors in their decision not to use TIVA for a particular case. Basic descriptive statistics were determined using SPSS statistical software, while graphical depictions of data were handled using R for statistical analysis. A total of 763 survey responses were included in the final analysis and stratified according to the frequency of TIVA use. Among the infrequent users, issues such as additional effort, institutional preference, lack of real-time monitoring of propofol concentration, risk of missing drug delivery failure and increased turnaround time were among the top reasons mentioned. Interestingly, these issues were considered far less important among the frequent users when not choosing TIVA. We concluded that frequent and infrequent users respond quite differently to similar technical TIVA-related factors. Non-technical factors may play an important role in the infrequent user's decision not to use TIVA for a particular case.

Effect of sufentanil on bispectral index in the elderly

We examined the impact of adding sufentanil during anaesthesia induction with propofol on bispectral index values in elderly patients (≥ 65 years). Patients were randomly assigned to receive a target-controlled sufentanil infusion (effect-site concentration of 0.3 ng.ml^-1 ) or matching placebo, followed by a target-controlled propofol induction (initial effect-site concentration of 0.5 μg.ml^-1 ; step-wise increase of 0.5 μg.ml^-1 ) until loss of consciousness defined as an Observer's Assessment of Alertness/Sedation score < 2. Seventy-one patients (sufentanil 35, placebo 36) completed the study. Mean (SD) age was 72.3 (5.8) years; 41% were women. At loss of consciousness, mean (SD) bispectral index value was 75.0 (8.6) with sufentanil and 70.0 (8.0) with placebo; mean difference -5.0 (95% confidence interval -8.9 to -1.1), p = 0.013. Post-hoc analyses suggest that the difference was significant in men only (mean difference -7.3 (-11.8 to -2.6), p = 0.003). Sufentanil co-induction with propofol results in higher bispectral index values at loss of consciousness in elderly patients.

A case series of vital signs-controlled, patient-assisted intravenous analgesia (VPIA) using remifentanil for labour and delivery

Intravenous remifentanil patient-controlled analgesia can be used during labour as an alternative to epidural analgesia. Adverse effects of opioids, including hypoxia and bradycardia, may lead to maternal morbidity and mortality. We devised an interactive feedback system based on a clinical proportional algorithm, to continuously monitor for adverse effects to enhance safety and better titrate analgesia. This vital signs-controlled, patient-assisted intravenous analgesia with remifentanil used a prototype delivery system linked to a pulse oximeter that evaluated maternal oxygen saturation and heart rate continuously. With this system, we detected oxygen saturation < 95% for more than 60 s in 15 of 29 subjects (52%); and heart rate < 60 min^-1 for more than 60 s in 7 of 29 subjects (24%) during use. The system automatically responded appropriately by reducing the dosages and temporarily halting remifentanil administration, thus averting further hypoxia and bradycardia.

Monosialoganglioside 1 may alleviate neurotoxicity induced by propofol combined with remifentanil in neural stem cells

Monosialoganglioside 1 (GM1) is the main ganglioside subtype and has neuroprotective properties in the central nervous system. In this study, we aimed to determine whether GM1 alleviates neurotoxicity induced by moderate and high concentrations of propofol combined with remifentanil in the immature central nervous system. Hippocampal neural stem cells were isolated from newborn Sprague-Dawley rats and treated with remifentanil (5, 10, 20 ng/mL) and propofol (1.0, 2.5, 5.0 μg/mL), and/or GM1 (12.5, 25, 50 μg/mL). GM1 reversed combined propofol and remifentanil-induced decreases in the percentage of 5-bromodeoxyuridine(+) cells and also reversed the increase in apoptotic cell percentage during neural stem cell proliferation and differentiation. However, GM1 with combined propofol and remifentanil did not affect β-tubulin(+) or glial fibrillary acidic protein(+) cell percentage during neural stem cell differentiation. In conclusion, we show that GM1 alleviates the damaging effects of propofol combined with remifentanil at moderate and high exposure concentrations in neural stem cells in vitro, and exerts protective effects on the immature central nervous system.