Why do women wake up faster than men from propofol anaesthesia?

Comparison of recovery profiles between total intravenous anaesthesia with propofol or remimazolam reversed with flumazenil in patients undergoing breast surgery: A randomised controlled trial

BACKGROUND

Remimazolam, a short acting benzodiazepine, is being used for general anaesthesia. The results of studies comparing recovery after propofol with that of remimazolam are inconsistent. Given that flumazenil reverses the sedative effects of remimazolam, we hypothesised that it would speed up recovery from remimazolam general anaesthesia.

OBJECTIVES

The aim of this trial was to compare the speed of recovery from general anaesthesia between propofol and remimazolam reversed with flumazenil in patients undergoing minimally invasive breast surgery.

DESIGN

Randomised, single-centre, double-blind controlled trial.

SETTING

A tertiary teaching hospital in South Korea from August 2022 to December 2022.

PATIENTS

Adult patients (≥19 years of age) about to undergo general anaesthesia for scheduled breast cancer surgery.

INTERVENTIONS

Patients were randomly allocated to either the propofol or the remimazolam/flumazenil group. The emergence process was monitored by only one anaesthesiologist.

MAIN OUTCOME MEASURES

The primary outcome was the time to eye opening to command during recovery from the general anaesthesia. Time to removal of the supraglottic airway (SGA) time to discharge, and the Riker sedation agitation scale (SAS) score (1 to 4) during emergence were compared as secondary outcomes.

RESULTS

The remimazolam group had a significantly shorter mean time to eye opening than the propofol group [127 ± 51 vs. 314 ± 140 s; mean difference 187 s (95% confidence interval (CI), 133 to 241 s; P  < 0.001]. The remimazolam group also had shorter times to SGA removal [169 ± 51 vs. 366 ± 149 s; mean difference 198 s (95% CI, 140 to 255 s); P  < 0.001] and time to discharge from the operating room [243 ± 55 vs. 449 ± 159 s; mean difference 206 s (95% CI, 145 to 267 s); P  < 0.001]. The SAS scores during emergence also differed significantly, with 1 patient in the propofol group and 25 in the remimazolam group attaining scores of 4 ( P  < 0.001).

CONCLUSION

Administration of remimazolam with flumazenil may be a promising option for patients undergoing breast cancer surgery, providing faster recovery and better SAS scores than propofol during emergence from general anaesthesia.

TRIAL REGISTRATION

ClinicalTrials.gov (NCT05435911).

Impact of female sex on anaesthetic awareness, depth, and emergence: a systematic review and meta-analysis

BACKGROUND

Suggested anaesthetic dose ranges do not differ by sex, likely because of limited studies comparing sexes. Our objective was to systematically synthesise studies with outcomes of unintended anaesthesia awareness under anaesthesia, intraoperative connected consciousness, time to emergence from anaesthesia, and dosing to achieve adequate depth of anaesthesia, and to compare between females and males.

METHODS

Studies were identified from MEDLINE, Embase, and the Cochrane library databases until August 2, 2022. Controlled clinical trials (randomised/non-randomised) and prospective cohort studies that reported outcomes by sex were included. Results were synthesised by random effects meta-analysis where possible, or narrative form.

RESULTS

Of the 19 749 studies identified, 64 (98 243 participants; 53 143 females and 45 100 males) were eligible for inclusion, and 44 citations contributed to meta-analysis. Females had a higher incidence of awareness with postoperative recall (33 studies, odds ratio 1.38, 95% confidence interval [CI] 1.09-1.75) and connected consciousness during anaesthesia (three studies, OR 2.09, 95% CI 1.04-4.23) than males. Time to emergence was faster in females, including time to eye-opening (10 studies, mean difference -2.28 min, 95% CI -3.58 to -0.98), and time to response to command (six studies, mean difference -2.84 min, 95% CI -4.07 to -1.62). Data on depth of anaesthesia were heterogenous, limiting synthesis to a qualitative review which did not identify sex differences.

CONCLUSIONS

Female sex was associated with a greater incidence of awareness under general anaesthesia, and faster emergence from anaesthesia. These data suggest reappraisal of anaesthetic care, including whether similar drug dosing for females and males represents best care.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42022336087.

Oestrous cycle affects emergence from anaesthesia with dexmedetomidine, but not propofol, isoflurane, or sevoflurane, in female rats

BACKGROUND

Although sex differences in anaesthetic sensitivity have been reported, what underlies these differences is unknown. In rodents, one source of variability in females is the oestrous cycle. Here we test the hypothesis that the oestrous cycle impacts emergence from general anaesthesia.

METHODS

Time to emergence was measured after isoflurane (2 vol% for 1 h), sevoflurane (3 vol% for 20 min), dexmedetomidine (50 μg kg-1 i.v., infused over 10 min), or propofol (10 mg kg-1 i.v. bolus) during proestrus, oestrus, early dioestrus, and late dioestrus in female Sprague-Dawley rats (n=24). EEG recordings were taken during each test for power spectral analysis. Serum was analysed for 17β-oestradiol and progesterone concentrations. The effect of oestrous cycle stage on return of righting latency was assessed using a mixed model. The association between righting latency and serum hormone concentration was tested by linear regression. Mean arterial blood pressure and arterial blood gases were assessed in a subset of rats after dexmedetomidine and compared in a mixed model.

RESULTS

Oestrous cycle did not affect righting latency after isoflurane, sevoflurane, or propofol. When in the early dioestrus stage, rats emerged more rapidly from dexmedetomidine than in the proestrus (P=0.0042) or late dioestrus (P=0.0230) stage and showed reduced overall power in frontal EEG spectra 30 min after dexmedetomidine (P=0.0049). 17β-Oestradiol and progesterone serum concentrations did not correlate with righting latency. Oestrous cycle did not affect mean arterial blood pressure or blood gases during dexmedetomidine.

CONCLUSIONS

In female rats, the oestrous cycle significantly impacts emergence from dexmedetomidine-induced unconsciousness. However, 17β-oestradiol and progesterone serum concentrations do not correlate with the observed changes.

The requirement of propofol for induction of anesthesia in patients with traumatic brain injury determined using bilateral bispectral index and target controlled infusion - An observational cohort study

Background and Aims

Patients with traumatic brain injury (TBI) frequently require emergency surgery. There is a paucity of literature with regard to anesthetic requirements in these patients. The aim of the study was to compare the dose of propofol required for induction of anesthesia in patients with different grades of TBI.

Material and Methods

This prospective, observational study included patients with mild, moderate, and severe grades of TBI undergoing emergency surgery within 48 h of injury. Bispectral Index (BIS) values were recorded using a bilateral BIS sensor. Anesthesia was induced with a target controlled infusion (TCI) pump. Once BIS reached 40, plasma (Cp) and effect-site (Ce) concentration and total dose of propofol required were noted from the TCI pump.

Results

Of the 96 patients recruited, 27, 36, and 33 patients belonged to mild, moderate, and severe TBI (sTBI) groups, respectively. The Ce of propofol in mild, moderate, and sTBI groups was 6 ± 0.9, 5.82 ± 0.98, and 4.48 ± 1.5 μg/mL (P < 0.001), and the dose of propofol required was 1.9 ± 0.2, 1.8 ± 0.4, 1.41 ± 0.5 mg/kg, respectively (P < 0.001). Baseline BIS on the injured side was 80 ± 7.8, 71 ± 9.4, 55 ± 11.6, and on the uninjured side was 89 ± 5.5, 81 ± 8.4, and 65 ± 12 in mild, moderate, and sTBI groups, respectively.

Conclusions

The requirement of propofol was reduced in patients with sTBI. The dose of propofol required for induction of anesthesia as determined using Ce was significantly lower only between sTBI and mild TBI and not between patients with sTBI and moderate TBI or between mild and moderate head injury. BIS values were significantly different between the groups (highest in mild TBI and lowest in sTBI) and between normal and injured sides within each group.

Considerations for Satisfactory Sedation during Dental Implant Surgery

Implant surgery is a lengthy dental procedure, and sedation is often used to reduce discomfort. The effectiveness of sedation has traditionally been evaluated in terms of patient and surgeon satisfaction, but the most important goal is not to induce a deep sleep in the patient, but rather to ensure that the surgery is performed safely and as planned. Additionally, adequate pain control is a necessary requirement for patient and surgeon satisfaction. Most patients undergoing implant surgery are middle-aged or older, and a relatively large number of them have cardiovascular disease. Infiltration anesthesia using articaine or lidocaine in combination with adrenaline is widely used, but its use in patients with cardiovascular disease is limited because of adrenaline’s effects on the cardiovascular system. The use of long-acting local anesthetics and the potential efficacy of ultrasound-guided jaw nerve block have been investigated to enhance analgesia without resorting to adrenaline. Midazolam and propofol are usually used for sedation, but dexmedetomidine, which causes less respiratory depression, and the ultrashort-acting benzodiazepine remimazolam are emerging as potential alternatives. Monitoring of anesthetic depth using electroencephalography is effective in maintaining a constant level of sedation. In addition, sedation promotes the stabilization of heart rate and blood pressure, reducing the risks associated with adrenaline and allowing for safer management.

The effect of anesthesia type on the outcomes of percutaneous nephrolithotomy in elderly males

Objective: To compare the anaesthesia methods in percutaneous nephrolithotomy in terms of safety and effectiveness in elderly men.Methods: Elderly male patients who had undergone percutaneous nephrolithotomy were screened retrospectively and divided into 2 groups: percutaneous nephrolithotomy under combined spino-epidural anaesthesia (Group CSEA, n = 70) and percutaneous nephrolithotomy under general anaesthesia (Group GA, n = 114). Preoperative, perioperative and postoperative outcome measures were examined.Results: Between the two groups, there was no statistically significant difference in terms of stone burden, stone location, presence of the previous operation in the same kidney, presence of staghorn stones, mean American Society of Anesthesiologists scores and presence of abnormal kidney (p > 0.05). The mean duration time in the operation room and post-anaesthesia care unit (PACU) was statistically shorter in the Group CSEA (p < 0.01). There was no significant difference between the two groups in terms of Clavien Grade 1 and above complications (p > 0.05). Stone-free rates and success rates were similar in both groups (p = 0.133 and p = 0.273, respectively).Conclusion: The type of anaesthesia does not affect the success rate and complication rate of percutaneous nephrolithotomy in elderly male patients. Patients who underwent percutaneous nephrolithotomy under CSEA needed less analgesic injection during the postoperative period. CSEA can shorten the time a patient spends in the operating room and PACU, which provides more effective use of operation room working hours.

Estrogen Receptor-A in Medial Preoptic Area Contributes to Sex Difference of Mice in Response to Sevoflurane Anesthesia

A growing number of studies have identified sex differences in response to general anesthesia; however, the underlying neural mechanisms are unclear. The medial preoptic area (MPA), an important sexually dimorphic structure and a critical hub for regulating consciousness transition, is enriched with estrogen receptor alpha (ERα), particularly in neuronal clusters that participate in regulating sleep. We found that male mice were more sensitive to sevoflurane. Pharmacological inhibition of ERα in the MPA abolished the sex differences in sevoflurane anesthesia, in particular by extending the induction time and facilitating emergence in males but not in females. Suppression of ERα in vitro inhibited GABAergic and glutamatergic neurons of the MPA in males but not in females. Furthermore, ERα knockdown in GABAergic neurons of the male MPA was sufficient to eliminate sex differences during sevoflurane anesthesia. Collectively, MPA ERα positively regulates the activity of MPA GABAergic neurons in males but not in females, which contributes to the sex difference of mice in sevoflurane anesthesia.

Differential effects of the novel neurosteroid hypnotic (3β,5β,17β)-3-hydroxyandrostane-17-carbonitrile on electroencephalogram activity in male and female rats

BACKGROUND

We recently showed that a neurosteroid analogue, (3β,5β,17β)-3-hydroxyandrostane-17-carbonitrile (3β-OH), induced hypnosis in rats. The aim of the present study was to evaluate the hypnotic and anaesthetic potential of 3β-OH further using electroencephalography.

METHODS

We used behavioural assessment and cortical electroencephalogram (EEG) spectral power analysis to examine hypnotic and anaesthetic effects of 3β-OH (30 and 60 mg kg-1) administered intraperitoneally or intravenously to young adult male and female rats.

RESULTS

We found dose-dependent sex differences in 3β-OH-induced hypnosis and EEG changes. Both male and female rats responded similarly to i.p. 3β-OH 30 mg kg-1. However, at the higher dose (60 mg kg-1, i.p.), female rats had two-fold longer duration of spontaneous immobility than male rats (203.4 [61.6] min vs 101.3 [32.1] min), and their EEG was suppressed in the low-frequency range (2-6 Hz), in contrast to male rats. Although a sex-dependent hypnotic effect was not confirmed after 30 mg kg-1 i.v., female rats appeared more sensitive to 3β-OH with relatively small changes within delta (1-4 Hz) and alpha (8-13 Hz) bands. Finally, 3β-OH had a rapid onset of action and potent hypnotic/anaesthetic effect after 60 mg kg-1 i.v. in rats of both sexes; however, all female rats and only half of the male rats reached burst suppression, an EEG pattern usually associated with profound inhibition of thalamocortical networks.

CONCLUSIONS

Based on its behavioural effects and EEG signature, 3β-OH is a potent hypnotic in rats, with female rats being more sensitive than male rats.

Sex, drugs, and anaesthesia research

In this issue of the British Journal of Anaesthesia, Joksimovic and colleagues report significant sex differences in sensitivity to the behavioural and neurophysiological effects of 3β-OH, a novel neurosteroid anesthetic. Female rats were more sensitive to the effects of 3β-OH than male rats, although the mechanims remain unclear. Sex differences have been understudied in anaesthesia research, and this article by Joksimovic and colleagues emphasizes the need to devote more effort to understanding these differences.

Methadone and a Clinical Pathway in Adolescent Idiopathic Scoliosis Surgery: A Historically Controlled Study

STUDY DESIGN

Historically controlled clinical trial.

OBJECTIVES

Patients presenting for correction of adolescent idiopathic scoliosis (AIS) by posterior spinal fusion may benefit from structured clinical pathways. We studied the effects of implementing a published clinical pathway for the perioperative care of patients with AIS that required intraoperative use of methadone at our institution.

METHODS

We performed a historically controlled clinical trial of patients undergoing posterior spinal fusion for AIS by comparing a retrospectively collected control group of 25 patients with a prospective experimental group of 14 patients receiving methadone, gabapentin, propofol, and remifentanil as part of a new clinical pathway.

RESULTS

Use of the pathway decreased average pain scores evaluated by the Numeric Rating Scale in the 24 hours following surgery (4.8 [4-6] to 3.4 [2-4], P = .03 [-2.6 to -0.2; t = -2.3]) and postoperative opioid consumption by 76% (41 [29-51] mg to 10 [4-17] mg, P < .001 [-45 to -15; Welch's t = 4.9]) during the same period. Improved analgesia and reduced reliance on opioids facilitated other postoperative elements of the clinical pathway and shortened the average hospital length of stay by 1 day (4 [3-6] days to 3 [3-5] days, P = .001 [-2 to -1; U = 67, Z = -3.3]).

CONCLUSIONS

Multimodal analgesia and a clinical pathway add value in the perioperative care of patients undergoing posterior spinal fusion for AIS by improving analgesia and shortening hospitalization. The prospective arm of the trial was registered at clinicaltrials.gov under NCT02481570.

Large-scale analysis of human gene expression variability associates highly variable drug targets with lower drug effectiveness and safety

Motivation

The effectiveness of drugs tends to vary between patients. One of the well-known reasons for this phenomenon is genetic polymorphisms in drug target genes among patients. Here, we propose that differences in expression levels of drug target genes across individuals can also contribute to this phenomenon.

Results

To explore this hypothesis, we analyzed the expression variability of protein-coding genes, and particularly drug target genes, across individuals. For this, we developed a novel variability measure, termed local coefficient of variation (LCV), which ranks the expression variability of each gene relative to genes with similar expression levels. Unlike commonly used methods, LCV neutralizes expression levels biases without imposing any distribution over the variation and is robust to data incompleteness. Application of LCV to RNA-sequencing profiles of 19 human tissues and to target genes of 1076 approved drugs revealed that drug target genes were significantly more variable than protein-coding genes. Analysis of 113 drugs with available effectiveness scores showed that drugs targeting highly variable genes tended to be less effective in the population. Furthermore, comparison of approved drugs to drugs that were withdrawn from the market showed that withdrawn drugs targeted significantly more variable genes than approved drugs. Last, upon analyzing gender differences we found that the variability of drug target genes was similar between men and women. Altogether, our results suggest that expression variability of drug target genes could contribute to the variable responsiveness and effectiveness of drugs, and is worth considering during drug treatment and development.

Availability and implementation

LCV is available as a python script in GitHub (https://github.com/eyalsim/LCV).

Supplementary information

Supplementary data are available at Bioinformatics online.

Sex effects on behavioral markers of emergence from propofol and isoflurane anesthesia in rats

Clinical studies have demonstrated sex-related differences in recovery from surgical anesthesia. This study aimed to characterize the emergence pattern following two anesthesia regimens in both sexes of rats. We considered six different markers of emergence from anesthesia: sigh, eye blinking, forelimb movement, mastication, neck extension, and recovery of the righting reflex (RORR). Spontaneous motor activity 24 h after the anesthesia induction was also examined. Our results showed that the rank order of the emergence latency after intraperitoneal propofol, PRO, exposure was forelimb movement < sigh < blink < mastication < neck extension < RORR, while after inhaled isoflurane, ISO, anesthesia the sequence was changed as sigh < blink < mastication < forelimb movement < neck extension < RORR in both male and female rats. Moreover, the latency to emergence after PRO in female rats was significantly higher than male rats, although following ISO there was no difference between the sexes (P < 0.001; P > 0.05, respectively). Open-field testing revealed no difference in PRO and ISO spontaneous locomotor activity due to drug administration (P > 0.05). These two anesthetics presented different emergence sequences. Although clinical data suggests that females arouse faster than males from anesthesia with propofol, our intraperitoneal technique in a rodent model had the opposite effect. Pharmacokinetic analysis demonstrated increased absorption of injected propofol for the female rats in our study, emphasizing the role of sexual dimorphism in drug distribution in rodents. Despite these pharmacokinetic differences, the pharmacodynamic effects of the drugs were remarkably consistent among both sexes through emergence.

Women awaken faster than men after electroencephalogram-monitored propofol sedation for colonoscopy: A prospective observational study

BACKGROUND

Sedation for colonoscopy using intravenous propofol has become standard in many Western countries.

OBJECTIVE

Gender-specific differences have been shown for general anaesthesia in dentistry, but no such data existed for gastrointestinal endoscopy.

DESIGN

A prospective observational study.

SETTING

An academic teaching hospital of Hannover Medical School.

PATIENTS

A total of 219 patients (108 women and 111 men) scheduled for colonoscopy.

INTERVENTION

Propofol sedation using electroencephalogram monitoring during a constant level of sedation depth (D0 to D2) performed by trained nurses or physicians after a body-weight-adjusted loading dose.

MAIN OUTCOME MEASURES

The primary end-point was the presence of gender-specific differences in awakening time (time from end of sedation to eye-opening and complete orientation); secondary outcome parameters analysed were total dose of propofol, sedation-associated complications (bradycardia, hypotension, hypoxaemia and apnoea), patient cooperation and patient satisfaction. Multivariate analysis was performed to correct confounding factors such as age and BMI.

RESULTS

Women awakened significantly faster than men, with a time to eye-opening of 7.3 ± 3.7 versus 8.4 ± 3.4 min (P = 0.005) and time until complete orientation of 9.1 ± 3.9 versus 10.4 ± 13.7 min (P = 0.008). The propofol dosage was not significantly different, with some trend towards more propofol per kg body weight in women (3.98 ± 1.81 mg versus 3.72 ± 1.75 mg, P = 0.232).

CONCLUSION

The effect of gender aspects should be considered when propofol is used as sedation for gastrointestinal endoscopy. That includes adequate dosing for women as well as caution regarding potential overdosing of male patients.

TRIAL REGISTRATION

ClinicalTrials.gov (Identifier: NCT02687568).

Effect of sex and polymorphisms of CYP2B6 and UGT1A9 on the difference between the target-controlled infusion predicted and measured plasma propofol concentration

Introduction

To examine whether sex and polymorphisms of cytochrome P450 (CYP) 2B6 and UDP-glucuronosyltransferase (UGT) 1A9 affect the difference between predicted and measured plasma propofol concentration during continuous infusion by target-controlled infusion.

Results

Blood samples of 69 patients (48 men and 21 women) were obtained at 4 h after initial propofol infusion. Percentage performance error (PE) was calculated to assess the difference between measured and predicted propofol concentration. Regression coefficients (β) and 95% confidence intervals (CI) of sex and the polymorphisms of CYP2B6 and UGT1A9 for PE were, separately and mutually, estimated with linear regression. Covariates included age and body mass index in the minimal adjusted model, and additionally included clinical factors (mean blood pressure, heart rate, volume of intravenous fluid, surgical site, surgical position, and pneumoperitoneum) in the full adjusted model. PE was higher in men than in women (28.7% versus 10.5%, p = 0.015). Female sex was inversely associated with PE: the minimal adjusted β = − 8.84 (95% CI, − 16.26 to − 1.43); however, the fully adjusted β with clinical factors became not significant. The average of PE did not differ between polymorphisms of CYP2B6 and UGT1A9, and β of CYP2B6 516G>T polymorphisms mutually adjusted with female sex was not significant. Mean blood pressure, heart rate, and volume of intravenous fluid were independently associated with PE in the full adjusted model.

Conclusions

Under 4 h anesthesia with propofol target-controlled infusion in our population, sex differences appeared to exist in the propofol concentration, which might be largely mediated by clinical factors, such as hemodynamic status.

Trial registration

UMIN-CTR UMIN000009015, Registered 1 October 2012

Electronic supplementary material

The online version of this article (10.1186/s40981-018-0196-8) contains supplementary material, which is available to authorized users.

Impact of clinical factors and UGT1A9 and CYP2B6 genotype on inter-individual differences in propofol pharmacokinetics

PURPOSE

Propofol is one of the most widely used fast-acting intravenously administered anesthetics. However, although large inter-individual differences in dose requirements and recovery time have been observed, there are few previous studies in which the association between several potential covariates, including genetic factors such as the UGT1A9 and CYP2B6 genotypes, and propofol pharmacokinetics was simultaneously examined. This study aimed to identify factors determining propofol pharmacokinetics.

METHODS

Eighty-three patients were enrolled, and their blood samples were collected 1, 5, 10, and 15 min after administering a single intravenous bolus of propofol at a dose of 2.0 ml/kg to measure propofol plasma concentration. Area under the time-plasma concentration curve from zero up to the last measurable time point (AUC_15min) was determined from the concentration data. The inter-individual variability of the propofol pharmacokinetics was evaluated by investigating relationships between AUC_15min and genotype of UGT1A9 and CYP2B6; clinical factors, such as age, sex, body mass index (BMI), and preoperative hematological examination; and hemodynamic variables measured by a pulse dye densitogram analyzer. The Spearman rank correlation coefficient and the Mann-Whitney U test were used for the statistical analysis of continuous and categorical values, respectively. Subsequently, clinical factors that had p values of < 0.05 in the univariate analysis were examined in a multivariate analysis using multiple linear regression analysis.

RESULTS

Age, BMI, indocyanine green disappearance ratio (K-ICG), hepatic blood flow (HBF), preoperative hemoglobin level, and sex were correlated with AUC_15min (p < 0.05) in univariate analysis. Multivariate analysis performed to adjust for age, BMI, K-ICG, HBF, preoperative hemoglobin level, and sex revealed only BMI as an independent factor associated with AUC_15min.

CONCLUSIONS

This study demonstrated that BMI influences propofol pharmacokinetics after its administration as a single intravenous injection, while UGT1A9 and CYP2B6 SNPs, other clinical factors, and hemodynamic variables do not. These results suggest that BMI is an independent factor associated with propofol pharmacokinetics in several potential covariates.

CLINICAL TRIALS REGISTRATION NUMBER

University Hospital Medical Information Network (UMIN000022948).

Male requires a higher median target effect-site concentration of propofol for I-gel placement when combined with dexmedetomidine

OBJECTIVE

The supraglottic airway device (SAD) can be used for airway management of spontaneous breathing patients, and propofol is commonly applied for the SAD placement. This study was designed to assess the effect of gender on median target effect-site concentration (Ce₅₀) of propofol for I-gel placement when combined with dexmedetomidine.

MATERIAL AND METHOD

19 males and 18 females, aged 18 to 59 and undergoing elective surgery, were enrolled. After intravenous infusion of dexmedetomidine 1.0μg/kg over 10min followed by continuous infusion of 0.4μg/kg/h, target-controlled infusion of propofol under Marsh model was started and the initial Ce of propofol was set at 4.79μg/mL and 4.35μg/mL in the male and female patients, respectively. The I-gel was inserted when the Ce of propofol reached the pre-set concentration and bispectral index value was less than 60. The Ce of propofol required for I-gel placement was determined by the Dixon up-and-down method.

RESULTS

The Ce₅₀ (95% confidence interval) of propofol required for I-gel placement were 4.082μg/mL (3.798-4.332μg/mL) and 3.509μg/mL (3.266-3.749μg/mL) in male and female patients, respectively, with a significantly higher Ce₅₀ in males.

CONCLUSION

When combined with dexmedetomidine, males require a higher Ce₅₀ of propofol for I-gel placement compared to females.

Sex as a Biological Variable in Emergency Medicine Research and Clinical Practice: A Brief Narrative Review

The National Institutes of Health recently highlighted the significant role of sex as a biological variable (SABV) in research design, outcome and reproducibility, mandating that this variable be accounted for in all its funded research studies. This move has resulted in a rapidly increasing body of literature on SABV with important implications for changing the clinical practice of emergency medicine (EM). Translation of this new knowledge to the bedside requires an understanding of how sex-based research will ultimately impact patient care. We use three case-based scenarios in acute myocardial infarction, acute ischemic stroke and important considerations in pharmacologic therapy administration to highlight available data on SABV in evidence-based research to provide the EM community with an important foundation for future integration of patient sex in the delivery of emergency care as gaps in research are filled.

Effects of different methods of general anesthesia on intraoperative awareness in surgical patients

The purpose of the study was to investigate the effects of total intravenous anesthesia (TIVA) and combined of intravenous and inhaled anesthesia (CIIA) on intraoperative awareness in surgical patients.A total of 678 patients were recruited in the CIIA group, while TIVA group included 566 patients. The clinical characteristics and the occurrence of intraoperative awareness were compared between the groups. Mini-Mental State Examination, Generalized Anxiety Disorder 7, and Patient Health Questionnaire 9 tests were performed to estimate cognitive and psychological functions of the patients. In addition, logistic regression analysis was applied to identify the risk factors for intraoperative awareness in surgical patients.In CIIA group, 3 patients (0.44%) were confirmed with intraoperative awareness, while 11 patients (1.94%) in TIVA group underwent intraoperative awareness. The occurrence rate of intraoperative awareness was significantly higher in VITA group than that in the CIIA group (P = .029). Awareness classification demonstrated that intraoperative awareness mainly included auditory, tactile, and pain perceptions. Moreover, 4 patients showed distress after operation. Patients with intraoperative awareness exhibited poor performance in cognitive and psychological tests (P < .001 for all). Logistic regression analysis demonstrated that CIIA (odds ratio [OR] = 0.198, 95% confidence interval [CI] = 0.047-0.827), age (OR = 0.951, 95% CI = 0.908-0.997), midazolam application (OR = 0.158, 95% CI = 0.034-0.736), awareness history (OR = 10.131, 95% CI = 2.206-45.517), and duration of surgery (OR = 1.016, 95% CI = 1.001-1.032) were significantly associated with intraoperative awareness.Intraoperative awareness can significantly influence the cognitive and psychological functions of surgical patients. CIIA and midazolam application may lower the risk of intraoperative awareness.

Location of the Mesopontine Neurons Responsible for Maintenance of Anesthetic Loss of Consciousness

The transition from wakefulness to general anesthesia is widely attributed to suppressive actions of anesthetic molecules distributed by the systemic circulation to the cerebral cortex (for amnesia and loss of consciousness) and to the spinal cord (for atonia and antinociception). An alternative hypothesis proposes that anesthetics act on one or more brainstem or diencephalic nuclei, with suppression of cortex and spinal cord mediated by dedicated axonal pathways. Previously, we documented induction of an anesthesia-like state in rats by microinjection of small amounts of GABA_A-receptor agonists into an upper brainstem region named the mesopontine tegmental anesthesia area (MPTA). Correspondingly, lesioning this area rendered animals resistant to systemically delivered anesthetics. Here, using rats of both sexes, we applied a modified microinjection method that permitted localization of the anesthetic-sensitive neurons with much improved spatial resolution. Microinjected at the MPTA hotspot identified, exposure of 1900 or fewer neurons to muscimol was sufficient to sustain whole-body general anesthesia; microinjection as little as 0.5 mm off-target did not. The GABAergic anesthetics pentobarbital and propofol were also effective. The GABA-sensitive cell cluster is centered on a tegmental (reticular) field traversed by fibers of the superior cerebellar peduncle. It has no specific nuclear designation and has not previously been implicated in brain-state transitions.SIGNIFICANCE STATEMENT General anesthesia permits pain-free surgery. Furthermore, because anesthetic agents have the unique ability to reversibly switch the brain from wakefulness to a state of unconsciousness, knowing how and where they work is a potential route to unraveling the neural mechanisms that underlie awareness itself. Using a novel method, we have located a small, and apparently one of a kind, cluster of neurons in the mesopontine tegmentum that are capable of effecting brain-state switching when exposed to GABA_A-receptor agonists. This action appears to be mediated by a network of dedicated axonal pathways that project directly and/or indirectly to nearby arousal nuclei of the brainstem and to more distant targets in the forebrain and spinal cord.

Driving Impairment Due to Propofol at Effect-Site Concentrations Relevant after Short Propofol-Only Sedation

Australian guidelines state “Following brief surgery or procedures with short acting anaesthetic drugs, the patient may be fit to drive after a normal night's sleep. After long surgery or procedures requiring longer lasting anaesthesia, it may not be safe to drive for 24 hours or more”. The increasing use of the short-acting anaesthetic drug propofol as a solitary sedative medication for simple endoscopy procedures suggests a need to review this blanket policy. Thirty patients presenting for elective day surgery were recruited as volunteers for a pre-procedure driving simulation study and randomised to propofol or placebo arms. Driving ability was assessed at baseline and then, in the propofol group, at three effect-site concentrations. Driving impairment at these concentrations of propofol was compared to that of a third group of volunteers with a blood alcohol concentration of 0.05% (g/100 ml). Driving impairment at 0.2 μg/ml propofol effect-site concentration was not statistically different to placebo. Impairment increased with propofol effect-site concentration ( P=0.002) and at 0.4 μg/ml it was similar to that found with a blood alcohol concentration of 50 mg/100 ml (0.05%). Plasma propofol concentrations of 0.2 μg/ml, as might be found approximately an hour after short (<1 hour duration) propofol-only sedation for endoscopy, were not associated with driving impairment in our young cohort of volunteers.

Anaesthetic interventions for prevention of awareness during surgery

BACKGROUND

General anaesthesia is usually associated with unconsciousness. 'Awareness' is when patients have postoperative recall of events or experiences during surgery. 'Wakefulness' is when patients become conscious during surgery, but have no postoperative recollection of the period of consciousness.

OBJECTIVES

To evaluate the efficacy of two types of anaesthetic interventions in reducing clinically significant awareness:- anaesthetic drug regimens; and- intraoperative anaesthetic depth monitors.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL, ISSUE 4 2016); PubMed from 1950 to April 2016; MEDLINE from 1950 to April 2016; and Embase from 1980 to April 2016. We contacted experts to identify additional studies. We performed a handsearch of the citations in the review. We did not search trial registries.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) of either anaesthetic regimens or anaesthetic depth monitors. We excluded volunteer studies, studies of patients prior to skin incision, intensive care unit studies, and studies that only randomized different word presentations for memory tests (not anaesthetic interventions).Anaesthetic drug regimens included studies of induction or maintenance, or both. Anaesthetic depth monitors included the Bispectral Index monitor, M-Entropy, Narcotrend monitor, cerebral function monitor, cerebral state monitor, patient state index, and lower oesophageal contractility monitor. The use of anaesthetic depth monitors allows the titration of anaesthetic drugs to maintain unconsciousness.

DATA COLLECTION AND ANALYSIS

At least two authors independently scanned abstracts, extracted data from the studies, and evaluated studies for risk of bias. We made attempts to contact all authors for additional clarification. We performed meta-analysis statistics in packages of the R language.

MAIN RESULTS

We included 160 studies with 54,109 enrolled participants; 53,713 participants started the studies and 50,034 completed the studies or data analysis (or both). We could not use 115 RCTs in meta-analytic comparisons because they had zero awareness events. We did not merge 27 of the remaining 45 studies because they had excessive clinical and methodological heterogeneity. We pooled the remaining 18 eligible RCTs in meta-analysis. There are 10 studies awaiting classification which we will process when we update the review.The meta-analyses included 18 trials with 36,034 participants. In the analysis of anaesthetic depth monitoring (either Bispectral Index or M-entropy) versus standard clinical and electronic monitoring, there were nine trials with 34,744 participants. The overall event rate was 0.5%. The effect favoured neither anaesthetic depth monitoring nor standard clinical and electronic monitoring, with little precision in the odds ratio (OR) estimate (OR 0.98, 95% confidence interval (CI) 0.59 to 1.62).In a five-study subset of Bispectral Index monitoring versus standard clinical and electronic monitoring, with 34,181 participants, 503 participants gave awareness reports to a blinded, expert panel who adjudicated or judged the outcome for each patient after reviewing the questionnaires: no awareness, possible awareness, or definite awareness. Experts judged 351 patient awareness reports to have no awareness, 87 to have possible awareness, and 65 to have definite awareness. The effect size favoured neither Bispectral Index monitoring nor standard clinical and electronic monitoring, with little precision in the OR estimate for the combination of definite and possible awareness (OR 0.96, 95% CI 0.35 to 2.65). The effect size favoured Bispectral Index monitoring for definite awareness, but with little precision in the OR estimate (OR 0.60, 95% CI 0.13 to 2.75).We performed three smaller meta-analyses of anaesthetic drugs. There were nine studies with 1290 participants. Wakefulness was reduced by ketamine and etomidate compared to thiopental. Wakefulness was more frequent than awareness. Benzodiazepines reduces awareness compared to thiopental, ketamine, and placebo., Also, higher doses of inhaled anaesthetics versus lower doses reduced the risk of awareness.We graded the quality of the evidence as low or very low in the 'Summary of findings' tables for the five comparisons.Most of the secondary outcomes in this review were not reported in the included RCTs.

AUTHORS' CONCLUSIONS

Anaesthetic depth monitors may have similar effects to standard clinical and electrical monitoring on the risk of awareness during surgery. In older studies comparing anaesthetics in a smaller portion of the patient sample, wakefulness occurred more frequently than awareness. Use of etomidate and ketamine lowered the risk of wakefulness compared to thiopental. Benzodiazepines compared to thiopental and ketamine, or higher doses of inhaled anaesthetics versus lower doses, reduced the risk of awareness.

Effect of sex differences in remifentanil requirements for the insertion of a laryngeal mask airway during propofol anesthesia: A prospective randomized trial

BACKGROUND

Remifentanil can improve insertion of a laryngeal mask airway (LMA) during induction with propofol. Recently, it has been suggested that there is a sex difference in opioid requirements for this procedure. The purposes of this study were to determine the effective effect-site concentration (Ce) of remifentanil for the facilitation of LMA insertion in male and female patients during propofol anesthesia without neuromuscular blockade and to evaluate whether there are sex differences in the Ce of remifentanil required for successful LMA insertion.

METHODS

Forty-eight patients (24 male, 24 female) with American Society of Anesthesiologists physical status 1 or 2, aged 20 to 60 years, scheduled for minor orthopedic surgery under general anesthesia were enrolled. Anesthesia was induced by target-controlled infusion (TCI) of propofol and remifentanil. The target Ce of propofol was 5 μg/mL initially and was reduced to 3.5 μg/mL after loss of consciousness. The Ce of remifentanil given to each patient was determined by the response of the previously tested patient using 0.5 ng/mL as a step size. The 1st patient was tested at a Ce of 3.0 ng/mL of remifentanil. Successful LMA insertion was defined as smooth insertion without patient movement or significant resistance to mouth opening.

RESULTS

The effective Ce of remifentanil required for successful LMA insertion on 50% of occasions (effective effect-site concentration for 50% [EC50]) as estimated by Dixon method was significantly lower in women (2.18 ± 0.35 ng/mL) than in men (2.82 ± 0.53 ng/mL) (P = 0.02). Using the isotonic regression method, the effective Ce of remifentanil required for successful LMA insertion on 95% of occasions (EC95) (95% confidence interval [CI]) was significantly lower in women (3.38 [3.0-3.48] ng/mL) than in men (3.94 [3.80-3.98] ng/mL).

CONCLUSION

The Ce of remifentanil required to facilitate successful LMA insertion is higher during propofol induction by TCI in men than in women. When using remifentanil for LMA insertion, patient sex should be taken into account for appropriate dosing.

Alterations in the coupling functions between cortical and cardio-respiratory oscillations due to anaesthesia with propofol and sevoflurane

The precise mechanisms underlying general anaesthesia pose important and still open questions. To address them, we have studied anaesthesia induced by the widely used (intravenous) propofol and (inhalational) sevoflurane anaesthetics, computing cross-frequency coupling functions between neuronal, cardiac and respiratory oscillations in order to determine their mutual interactions. The phase domain coupling function reveals the form of the function defining the mechanism of an interaction, as well as its coupling strength. Using a method based on dynamical Bayesian inference, we have thus identified and analysed the coupling functions for six relationships. By quantitative assessment of the forms and strengths of the couplings, we have revealed how these relationships are altered by anaesthesia, also showing that some of them are differently affected by propofol and sevoflurane. These findings, together with the novel coupling function analysis, offer a new direction in the assessment of general anaesthesia and neurophysiological interactions, in general.

Male patients require higher optimal effect-site concentrations of propofol during i-gel insertion with dexmedetomidine 0.5 μg/kg

BACKGROUND

The pharmacokinetics and pharmacodynamics of an anesthetic drug may be influenced by gender. The purpose of this study was to compare effect-site half maximal effective concentrations (EC50) of propofol in male and female patients during i-gel insertion with dexmedetomidine 0.5 μg/kg without muscle relaxants.

METHODS

Forty patients, aged 20-46 years of ASA physical status I or II, were allocated to one of two groups by gender (20 patients per group). After the infusion of dexmedetomidine 0.5 μg/kg over 2 min, anesthesia was induced with a pre-determined effect-site concentration of propofol by target controlled infusion. Effect-site EC50 values of propofol for successful i-gel insertion were determined using the modified Dixon's up-and-down method.

RESULTS

Mean effect-site EC50 ± SD of propofol for successful i-gel insertion was significantly higher for men than women (5.46 ± 0.26 μg/ml vs. 3.82 ± 0.34 μg/ml, p < 0.01). The EC50 of propofol in men was approximately 40% higher than in women. Using isotonic regression with a bootstrapping approach, the estimated EC50 (95% confidence interval) of propofol was also higher in men [5.32 (4.45-6.20) μg/ml vs. 3.75 (3.05-4.43) μg/ml]. The estimated EC95 (95% confidence interval) of propofol in men and women were 5.93 (4.72-6.88) μg/ml and 4.52 (3.02-5.70) μg/ml, respectively.

CONCLUSIONS

During i-gel insertion with dexmedetomidine 0.5 μg/kg without muscle relaxant, male patients had higher effect-site EC50 for propofol using Schnider's model. Based on the results of this study, patient gender should be considered when determining the optimal dose of propofol during supraglottic airway insertion.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT02268656. Registered August 26, 2014.

Alfentanil during rapid sequence induction with thiopental 4 mg/kg and rocuronium 0.6 mg/kg: tracheal intubation conditions

BACKGROUND

Opioids have become an integral part of anaesthesia induction. We aimed to determine the dose of alfentanil needed to obtain perfect tracheal intubation conditions during rapid sequence induction with standard doses of thiopental and rocuronium, where laryngoscopy was initiated 55 s after commencement of drug administration. The influence of covariates (sex, body weight, age, alfentanil plasma concentration at laryngoscopy) was tested.

METHODS

Eighty-four healthy individuals were randomly assigned to receive one of the seven assessor-blinded alfentanil doses (0, 10, 20, 30, 40, 50 and 60 μg/kg) in conjunction with thiopental 4 mg/kg and rocuronium 0.6 mg/kg. For drug administration, 15 s was allowed. Laryngoscopy was initiated 40 s after rocuronium and tracheal intubation concluded within 70 s after commencement of drug administration. Alfentanil doses associated with 50%, 90% and 95% probability of perfect intubation conditions were determined with logistic regression. Multiple logistic regressions were used to test the influence of covariates. The relationship between alfentanil dose and concentration at laryngoscopy was analysed with linear regression. The effects of covariates on plasma concentrations of alfentanil were tested with multiple linear regressions.

RESULTS

Perfect intubation conditions of 95% probability was obtained with 56 μg/kg (confidence intervals 44-68). None of the covariates were significant predictors of perfect intubation conditions. Alfentanil plasma concentration correlated with dose and increased with increasing body weight (1.7 ng/ml/kg).

CONCLUSION

Perfect intubation conditions during rapid sequence induction can be obtained with clinically relevant doses of alfentanil in most healthy patients anaesthetized with thiopental 4 mg/kg and rocuronium 0.6 mg/kg.

Propofol detection and quantification in human blood: the promise of feedback controlled, closed-loop anesthesia

The performance of a membrane-coated voltammetric sensor for propofol (2,6-diisopropylphenol) has been characterized in long term monitoring experiments using an automated flow analytical system (AFAS) and by analyzing human serum and whole blood samples by standard addition. It is shown that the signal of the membrane-coated electrochemical sensor for propofol is not influenced by the components of the pharmaceutical formulation of propofol (propofol injectable emulsion). The current values recorded with the electrochemical propofol sensor in buffer solutions and human serum samples spiked with propofol injectable emulsion showed excellent correlation with the peak heights recorded with an UV-Vis detector during the HPLC analysis of these samples (R(2) = 0.997 in PBS and R(2) = 0.975 in human serum). However, the determination of propofol using the electrochemical method is simpler, faster and has a better detection limit (0.08 ± 0.05 μM) than the HPLC method (0.4 ± 0.2 μM). As a first step towards feedback controlled closed-loop anesthesia, the membrane-coated electrochemical sensor has been implemented onto surface of an intravenous catheter. The response characteristics of the membrane-coated carbon fiber electrode on the catheter surface were very similar to those seen using a macroelectrode.

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

PURPOSE

The purpose of this study was to determine the effect-site concentration (Ce) of remifentanil in 50% of patients (EC₅₀) and 95% of patients (EC₉₅) for smooth laryngeal mask airway (LMA) removal in adults under propofol and remifentanil anesthesia.

MATERIALS AND METHODS

Twenty-five patients of ASA physical status I-II and ages 18-60 years who were to undergo minor gynecological or orthopedic surgery were assessed in this study. Anesthesia was induced and maintained with propofol and remifentanil target-controlled infusion (TCI). Remifentanil was maintained at a predetermined Ce during the emergence period. The modified Dixon's up-and-down method was used to determine the remifentanil concentration, starting from 1.0 ng/mL (step size of 0.2 ng/mL). Successful removal of the LMA was regarded as absence of coughing/gagging, clenched teeth, gross purposeful movements, breath holding, laryngospasm, or desaturation to SpO₂<90%.

RESULTS

The mean±SD Ce of remifentanil for smooth LMA removal after propofol anesthesia was 0.83±0.16 ng/mL. Using isotonic regression with a bootstrapping approach, the estimated EC₅₀ and EC₉₅ of remifentanil Ce were 0.91 ng/mL [95% confidence interval (CI), 0.77-1.07 ng/mL] and 1.35 ng/mL (95% CI, 1.16-1.38 ng/mL), respectively.

CONCLUSION

Our results showed that remifentanil TCI at an established Ce is a reliable technique for achieving safe and smooth emergence without coughing, laryngospasm, or other airway reflexes.

Confounding factors to predict the awakening effect-site concentration of propofol in target-controlled infusion based on propofol and fentanyl anesthesia

We conducted a large retrospective study to investigate the confounding factors that predict Ce ROC under propofol-based TIVA with TCI. We recorded sex, age, height, weight, Ce LOC, Ce ROC, total propofol and fentanyl consumption dose, and anesthetic time. Simple linear regression models were used to identify potential predictors of Ce ROC, and multiple linear regression models were used to identify the confounding predictors of Ce ROC. We found that Ce ROC correlated with age, sex, Ce LOC, and both total fentanyl and propofol consumption dose. The prediction formula was: Ce ROC = 0.87 - 0.06 × age + 0.18 × Ce LOC + 0.04 (if fentanyl consumption > 150 μg; if not, ignore this value) + 0.07 × (1 or 2, according to the total propofol consumption dose, 1 for a propofol amount 1000-2000 mg and 2 for a propofol amount > 2000 mg). We simplified the formula further as Ce ROC = 0.87 - 0.06 × age + 0.18 × Ce LOC. In conclusion, Ce ROC can be predicted under TCI with propofol- and fentanyl-based TIVA. The confounding factors that predicted propofol Ce ROC are age, sex, Ce LOC, and total consumption dose of propofol and fentanyl.

A study of psycho-behavioral patterns in patients emerging from general anesthesia using sevoflurane, propofol and their combination in early, intermediate and late post-operative period: A randomized controlled trial

Background:

It has been contended the general anesthetic agents also may affect the psycho-social behavior of the patients, especially during the emergence from GA. This assumes much significance in day cases where, patients have to be roadworthy and mentally stable before discharge.

Aims:

We compared the psycho-behavioral effects of propofol, sevoflurane and their combination, while emerging from anesthesia.

Settings and Design:

The patients coming for short duration day care anesthesia were studied in a prospective randomized controlled comparison.

Materials and Methods:

The psycho-behavioral changes in early, intermediate and late recovery period were studied in 60 consenting patients undergoing Total Intra Venous Anesthesia (TIVA) using Propofol, Volatile Induction and Maintenance Anesthesia (VIMA) using Sevoflurane and the combination of these two agents.

Statistical Analysis:

Statistical Analysis of the data and application of various statistical tests was carried out with help of Statistical Package for Social Services (SPSS version 18). Data were compiled, analyzed and presented as frequency, proportions, mean and standard deviation. The tests of significance, like Chi-square test, percentages, independent sample t test, paired t test, and P value were used in the study.

Results and Conclusions:

Both the modalities of GA, viz; TIVA and VIMA, do produce significant psycho-behavioral changes in the patients after GA, though transiently. So it is imperative for the Clinicians to anticipate the entire aspect of Psycho-behavioral patterns before discharging the day cases from the Post anesthesia Care Unit (PACU).

Electroencephalographic variation during end maintenance and emergence from surgical anesthesia

The re-establishment of conscious awareness after discontinuing general anesthesia has often been assumed to be the inverse of loss of consciousness. This is despite the obvious asymmetry in the initiation and termination of natural sleep. In order to characterize the restoration of consciousness after surgery, we recorded frontal electroencephalograph (EEG) from 100 patients in the operating room during maintenance and emergence from general anesthesia. We have defined, for the first time, 4 steady-state patterns of anesthetic maintenance based on the relative EEG power in the slow-wave (<14 Hz) frequency bands that dominate sleep and anesthesia. Unlike single-drug experiments performed in healthy volunteers, we found that surgical patients exhibited greater electroencephalographic heterogeneity while re-establishing conscious awareness after drug discontinuation. Moreover, these emergence patterns could be broadly grouped according to the duration and rapidity of transitions amongst these slow-wave dominated brain states that precede awakening. Most patients progressed gradually from a pattern characterized by strong peaks of delta (0.5-4 Hz) and alpha/spindle (8-14 Hz) power ('Slow-Wave Anesthesia') to a state marked by low delta-spindle power ('Non Slow-Wave Anesthesia') before awakening. However, 31% of patients transitioned abruptly from Slow-Wave Anesthesia to waking; they were also more likely to express pain in the post-operative period. Our results, based on sleep-staging classification, provide the first systematized nomenclature for tracking brain states under general anesthesia from maintenance to emergence, and suggest that these transitions may correlate with post-operative outcomes such as pain.

The effect of patient sex on the incidence of early adverse effects in a population of elderly patients

Patient sex is known to influence the response to general and regional anaesthesia and recovery after surgery. However, most studies come from analyses carried out on middle-aged patients. As most of the patients admitted to the post-anaesthesia recovery room in our institution are elderly, we took the opportunity to investigate the association between sex and incidence of early adverse events in this older population of patients after major surgery. Consecutive patients undergoing general, orthopaedic, urological and gynaecological surgery, admitted to the recovery room of our institution over a 15-month period, were retrospectively studied. The following adverse events were considered in the analysis: shivering, postoperative nausea and vomiting, hypotension and hypertensive responses, new arrhythmias requiring treatment, acute respiratory failure and desaturation. A total of 1347 patients (mean age 73.3±15.1 years, 61.4% women) were included. Women showed a higher incidence of shivering (relative difference +48%, P=0.0003), postoperative nausea and vomiting (+91%, P<0.0001), hypotension (+32%, P=0.044) and desaturation (+60%, P=0.0030) than men. The incidence of hypertensive response, arrhythmias and acute respiratory failure were not statistically significantly different. The findings of this exploratory study suggest that women have a higher risk of early postoperative adverse events even in a more elderly population.

Awareness and recall during general anesthesia

Anesthesia awareness is defined as both consciousness and recall of surgical events. New research has been conducted out to test this phenomenon. However, testing methods have not proven reliable, including those using devices based on electroencephalographic techniques to detect and prevent intraoperative awareness. The limitations of a standard intraoperative brain monitor reflect our insufficient understanding of consciousness. Moreover, patients who experience an intraoperative awareness can develop serious post-traumatic stress disorders that should not be overlooked. In this review, we introduce the incidence of intraoperative awareness during general anesthesia and discuss the mechanisms of consciousness, as well as risk factors, various monitoring methods, outcome and prevention of intraoperative awareness.

A waking nightmare: how can we avoid accidental awareness during general anaesthesia?

Anaesthesia awareness is a terrifying prospect for any patient undergoing a surgical procedure and can cause considerable physical and psychological distress. Recommendations to reduce the risk of anaesthesia awareness include: undertaking a thorough preoperative assessment, ensuring that equipment has been checked, reducing drug error, consistent monitoring, and investment in safer technology. By implementing these recommendations it is hoped that patient safety and care can be improved during clinical anaesthesia.

Influence of a modified propofol equilibration rate constant (k(e0)) on the effect-site concentration at loss and recovery of consciousness with the Marsh model

This study compared the predicted effect-site concentration of propofol at loss and recovery of consciousness when using target-controlled infusion devices with the same pharmacokinetic model (Marsh) but a different plasma effect-site equilibration rate constant (ke0 ), the Diprifusor(TM) (ke0 0.26 min(-1) ) and Base Primea™ (ke0 1.21 min(-1) ). We studied 60 female patients undergoing minor gynaecological surgery under general anaesthesia. Although the total dose of propofol and time until loss of consciousness were comparable, the effect-site concentration at loss of consciousness was significantly lower with the Diprifusor than with the Base Primea (1.2 (0.3) μg.ml(-1) vs 4.5 (0.9) μg.ml(-1) , respectively, p < 0.001). The effect-site concentration at recovery of consciousness was significantly higher with the Diprifusor than with the Base Primea (1.8 (0.4) μg.ml(-1) vs 1.5 (0.2) μg.ml(-1) , respectively, p = 0.01). In conclusion, the effect-site concentration of propofol differs depending on the ke0 , despite the use of the same pharmacokinetic model. Therefore, the ke0 should be considered when predicting loss and recovery of consciousness based on the effect-site concentration of propofol.

Sex and gender aspects in anesthetics and pain medication

The influence of sex and gender on anesthesia and analgesic therapy remains poorly understood, nevertheless the numerous physiological and pharmacological differences present between men and women. Although in anesthesiology sex-gender aspects have attracted little attention, it has been reported that women have a greater sensitivity to the non-depolarizing neuroblocking agents, whereas males are more sensitive than females to propofol. It has been suggested that men wake slower than women after general anesthesia and have less postoperative nausea and vomiting. Sexual hormones seem to be of importance in the onset of differences. Nevertheless, in the last years, sex-gender influences on pain and analgesia have become a hot topic and data regarding sex-gender differences in response to pharmacologic and non-pharmacologic pain treatments are still scanty, inconsistent, and non-univocal. In particular, females seem to be more sensitive than males to opioid receptor agonists. Women may experience respiratory depression and other adverse effects more easily if they are given the same doses as males. Evidently, there is an obvious need for more research, which should include psychological and social factors in experimental preclinical and clinical paradigms in view of their importance on pain mechanism, in order to individualize analgesia to optimize pain relief.

Risk factor for intraoperative awareness

BACKGROUND AND OBJECTIVES

The intraoperative awareness is an adverse event in the general anesthesia, and may occur in approximately 20,000 cases per year, which justifies the study of the risk factors for this event. The objective of this study was to review this subject in order to reduce the incidence of intraoperative awareness and psychological sequelae incurring from this incident, which may result in post-traumatic stress disorder with negative repercussions on the surgical patient social, psychic and functional development.

CONTENT

It was conducted a review of the intraoperative awareness assessing its different phases during general anesthesia such as dreaming, wakefulness, explicit and implicit memory, as well as the analysis, consequences and prevention of its main related factors.

CONCLUSIONS

The reduction of awareness incidence during anesthesia is related to the anesthesiologist improved scientific and technical performance, involving issues such as monitoring, comprehension of the anesthesia activity components, hypnotic and analgesic drugs, neuromuscular blocking agents, autonomic and motor reflex control, in addition to the risk factors involved in this event.

The influence of initial target effect-site concentrations of propofol on the similarity of effect-sites concentrations at loss and return of consciousness in elderly female patients with the Diprifusor system

Background:

Whether effect-site concentrations of propofol (Cep) at loss of consciousness and return of consciousness (LOC and ROC, respectively) in elderly women using Diprifusor are similar is unclear. We investigated whether differences in initial target Cep (Ctarget) alter similarities between Cep values at LOC and ROC.

Materials and Methods:

In this study, female patients (n = 58, age = 72.5 ± 1.1 years) undergoing knee arthroplasty were administered propofol with Diprifusor. Cep at LOC and ROC were estimated for different Ctarget values (3.0–4.5 μg/ml). Pearson's correlation coefficient analysis and simple regression were performed to assess the relationship between Cep at LOC and ROC for each Ctarget. Differences in correlation coefficients of regression lines obtained from each Ctarget group were determined using the t-test.

Results:

The different Ctarget groups did not show significant differences in total propofol levels and in Cep values at LOC or ROC. However, Cep at ROC was significantly higher than Cep at LOC when Ctarget was 4.0 and 4.5 μg/ml, whereas these Cep values were not significantly different in low Ctarget groups.

Strong positive correlations were observed between Cep at LOC and ROC for all Ctarget groups. Regression coefficients for the different Ctarget groups were not significantly different. Compared to low (≤3.5 μg/ml) Ctarget groups, high Ctarget groups showed significantly shorter time until LOC. Induction quality was not significantly different among the groups.

Conclusions:

In elderly women, Cep values at LOC are strong predictors of Cep at ROC when Ctarget is 3.0–4.5 μg/ml. High Ctarget groups (≥4.0 μg/ml) exhibited shorter induction times with normal cardiovascular stability.

Sex-gender research sensitivity and healthcare disparities

Authors Nieuwenhoven and Klinge (Journal of Women's Health 2010;19:1-6) argue that despite advances, sex and gender are not well treated in the biomedical literature. Many studies in which males and females are represented do not address the similarities or differences between sexes, sometimes adjusting for (thereby obscuring) sex differences and sometimes ignoring sex altogether. Women continue to be underrepresented in randomized drug trials, excluded from some by potential reproductive effects, and perhaps frightened from others by IRB-required warnings. Although recognized, sex disparities in treatment, for example, for acute cardiac syndrome, persist. As electronic abstracts become a prime means of communicating research results, they must adequately and accurately represent a study's findings.