Optimization of desflurane administration in morbidly obese patients: a comparison with sevoflurane using an ‘inhalation bolus’ technique

Implementation of a Bayesian based advisory tool for target-controlled infusion of propofol using qCON as control variable

This single blinded randomized controlled trial aims to assess whether the application of a Bayesian-adjusted CePROP (effect-site of propofol) advisory tool leads towards a more stringent control of the cerebral drug effect during anaesthesia, using qCON as control variable. 100 patients scheduled for elective surgery were included and randomized into a control or intervention group (1:1 ratio). In the intervention group the advisory screen was made available to the clinician, whereas it was blinded in the control group. The settings of the target-controlled infusion pumps could be adjusted at any time by the clinician. Cerebral drug effect was quantified using processed EEG (CONOX monitor, Fresenius Kabi, Bad Homburg, Germany). The time of qCON between the desired range (35-55) during anaesthesia maintenance was defined as our primary end point. Induction parameters and recovery times were considered secondary end points and coefficient of variance of qCON and CePROP was calculated in order to survey the extent of control towards the mean of the population. The desired range of qCON between 35 and 55 was maintained in 84% vs. 90% (p = 0.15) of the case time in the control versus intervention group, respectively. Secondary endpoints showed similar results in both groups. The coefficient of variation for CePROP was higher in the intervention group. The application of the Bayesian-based CePROP advisory system in this trial did not result in a different time of qCON between 35 and 55 (84 [21] vs. 90 [18] percent of the case time). Significant differences between groups were hard to establish, most likely due to a very high performance level in the control group. More extensive control efforts were found in the intervention group. We believe that this advisory tool could be a useful educational tool for novices to titrate propofol effect-site concentrations.

Similarity and dissimilarity in alterations of the gene expression profile associated with inhalational anesthesia between sevoflurane and desflurane

Although sevoflurane is one of the most commonly used inhalational anesthetic agents, the popularity of desflurane is increasing to a level similar to that of sevoflurane. Inhalational anesthesia generally activates and represses the expression of genes related to xenobiotic metabolism and immune response, respectively. However, there has been no comprehensive comparison of the effects of sevoflurane and desflurane on the expression of these genes. Thus, we used a next-generation sequencing method to compare alterations in the global gene expression profiles in the livers of rats subjected to inhalational anesthesia by sevoflurane or desflurane. Our bioinformatics analyses revealed that sevoflurane and, to a greater extent, desflurane significantly activated genes related to xenobiotic metabolism. Our analyses also revealed that both anesthetic agents, especially sevoflurane, downregulated many genes related to immune response.

Systematic review with meta-analysis of relative risk of prolonged times to tracheal extubation with desflurane versus sevoflurane or isoflurane

The objective of this systematic review was to estimate the relative risk of prolonged times to tracheal extubation with desflurane versus sevoflurane or isoflurane. Prolonged times are defined as ≥15 min from end of surgery (or anesthetic discontinuation) to extubation in the operating room. They are associated with reintubations, naloxone and flumazenil administration, longer times from procedure end to operating room exit, greater differences between actual and scheduled operating room times, longer times from operating room exit to next case start, longer durations of the workday, and more operating room personnel idle while waiting for extubation. Published randomized clinical trials of humans were included. Generalized pivotal methods were used to estimate the relative risk of prolonged extubation for each study from reported means and standard deviations of extubation times. The relative risks were combined using DerSimonian-Laird random effects meta-analysis with Knapp-Hartung adjustment. From 67 papers, there were 78 two-drug comparisons, including 5167 patients. Studies were of high quality (23/78) or moderate quality (55/78), the latter due to lack of blinding of observers to group assignment and/or patient attrition because patients were extubated after operating room exit. Desflurane resulted in a 65% relative reduction in the incidence of prolonged extubation compared with sevoflurane (95% confidence interval 49% to 76%, P < .0001) and in a 78% relative reduction compared with isoflurane (58% to 89%, P = .0001). There were no significant associations between studies' relative risks and quality, industry funding, or year of publication (all six meta-regressions P ≥ .35). In conclusion, when emergence from general anesthesia with different drugs are compared with sevoflurane or isoflurane, suitable benchmarks quantifying rapidity of emergence are reductions in the incidence of prolonged extubation achieved by desflurane, approximately 65% and 78%, respectively. These estimates give realistic context for interpretation of results of future studies that compare new anesthetic agents to current anesthetics.

The science behind banning desflurane: A narrative review

Potent inhaled anaesthetics are halogenated hydrocarbons with a large global warming effect. The use of fluorinated hydrocarbons (most are not anaesthetics) are being restricted but volatile anaesthetics have been exempted from legislation, until now: the EU has formulated a proposal to ban or at least severely restrict the use of desflurane starting January 2026. This narrative review addresses the implications of a politics-driven decision - without prior consultation with major stakeholders, such as the European Society of Anaesthesiology and Intensive Care (ESAIC) - on daily anaesthesia practice and reviews the potential scientific arguments that would support stopping the routine use of desflurane in anaesthetic practice. Of note, banning or severely restricting the use of one anaesthetic agent should not distract the user from sensible interventions like reducing fresh gas flows and developing technology to capture and recycle or destroy the wasted potent inhaled anaesthetics that we will continue to use. We call to join efforts to minimise our professional environmental footprint.

Postoperative Recovery Outcomes for Obese Patients Undergoing General Anesthesia: A Meta-Analysis of Randomized Controlled Trials

Purpose

This study was performed to assess the postoperative recovery outcomes in obese patients undergoing general anesthesia.

Methods

The eligible studies were identified from PubMed, EmBase, and the Cochrane library until December 2020. The standard mean differences (SMDs) with 95% confidence intervals (CIs) were used to calculate the role of desflurane, sevoflurane, and propofol on recovery outcomes, and the analyses using the random-effects model.

Results

Eleven randomized controlled trials involving 713 obese patients undergoing general anesthesia were selected for final meta-analysis. We noted desflurane was associated with a shorter time to eye-opening than sevoflurane (SMD: −0.86; 95% CI, −1.43 to −0.28; P = 0.003). The use of desflurane with shorter time to extubation as compared with propofol (SMD: −1.13; 95% CI, −1.52 to −0.73; P < 0.001) or sevoflurane (SMD: −1.19; 95% CI, −2.15 to −0.22; P = 0.016), while sevoflurane was associated with longer time to extubation as compared with propofol (SMD: 1.47; 95% CI, 1.03 to 1.91; P < 0.001). Desflurane were associated with shorter time to stating name as compared with propofol (SMD: −1.40; 95% CI, −2.32 to −0.48; P = 0.003) or sevoflurane (SMD: −2.09; 95% CI, −3.33 to −0.85; P = 0.001). In addition, desflurane was associated with a longer time for orientation to place as compared with propofol (SMD: 0.65; 95% CI, 0.22 to 1.07; P = 0.003), while desflurane with shorter time for orientation to place as compared with sevoflurane (SMD: −0.88; 95% CI, −1.46 to −0.30; P = 0.003).

Conclusions

The use of desflurane could provide better recovery outcomes in obese patients undergoing general anesthesia. Further large-scale trials should be comparison the long-term effectiveness of various anesthetics.

A review on the anesthetic management of obese patients undergoing surgery

There has been an observed increase in theprevalence of obesity over the past few decades. The prevalence of anesthesiology related complications is also observed more frequently in obese patients as compared to patients that are not obese. Due to the increased complications that accompany obesity, obese patients are now more often requiring surgical interventions. Therefore, it is important that anesthesiologists be aware of this development and is equipped to manage these patients effectively and appropriately. As a result, this review highlights the effective management of obese patients undergoing surgery focusing on the preoperative, perioperative and postoperative care of these patients.

Recovery Profiles of Sevoflurane and Desflurane with or without M-Entropy Guidance in Obese Patients: A Randomized Controlled Trial

Obesity increases the risk of prolonged emergence from general anesthesia due to the delayed release of anesthetic agents from body fat. This trial aimed to evaluate the effects of sevoflurane and desflurane along with anesthetic depth monitoring on emergence time from anesthesia in obese patients. Adults with a body mass index ≥ 30 kg·m⁻² undergoing laparoscopic sleeve gastrectomy at a medical center were randomized into four groups: sevoflurane or desflurane anesthesia with or without M-Entropy guidance on anesthetic depth in a ratio of 1:1:1:1. In the M-Entropy guidance groups, the dosage of sevoflurane and desflurane was adjusted to achieve response and state entropy values between 40 and 60 during surgery. In the non-M-Entropy guidance groups, the dosage of anesthetics was titrated according to clinical signs. Primary outcome was time to spontaneous eye opening. A total of 80 participants were randomized. Compared to sevoflurane, desflurane anesthesia significantly reduced the time to spontaneous eye opening [mean difference (MD): −129 s; 95% confidence interval (CI): −211, −46], obeying commands (−160; −243, −77), tracheal extubation (−172; −266, −78), and leaving operating room (−148; −243, −54). M-Entropy guidance further reduced time to eye opening (MD: −142 s; 99.2% CI: −276, −8), tracheal extubation (−199; −379, −19), and leaving operating room (−190; −358, −23) in the desflurane but not the sevoflurane group. M-Entropy guidance significantly reduced the risk of agitation during emergence, i.e., risk difference: −0.275 (95% CI: −0.464, −0.086); and number needed to treat: 4. Compared to sevoflurane, using desflurane to maintain general anesthesia accelerated the return of consciousness in obese patients. M-Entropy guidance further hastened awakening in patients using desflurane and prevented emergence agitation.

A comparative study of desflurane versus sevoflurane in obese patients: Effect on recovery profile

Background and Aims:

Anesthesia in obese patients is difficult due to associated comorbidities and altered physiology. Desflurane and sevoflurane have a low fat-blood solubility coefficient and are better suited in these patients to achieve a rapid emergence. We studied BIS guided drug titration to compare the postoperative recovery characteristics and cognitive function of desflurane versus sevoflurane in obese patients undergoing laparoscopic abdominal surgeries.

Material and Methods:

After institutional ethics committee approval and written informed consent, sixty obese patients (BMI ≥30 kg/m²) were randomized to receive either BIS guided desflurane or sevoflurane. Recovery was assessed by time taken for eye opening on verbal command, sustained head lift for 5 s, and extubation and orientation to time, place, and person after discontinuation of volatile anesthetic agent. For cognitive function, time taken to complete Mini mental state examination (MMSE) score to baseline was compared in both study groups.

Results:

Difference of time taken for eye opening on verbal command, sustained head lift for 5 s, and extubation and orientation to time, place, and person was not significant between both anesthetic groups. Patients in sevoflurane group took significantly (P-value = 0.001) less time (40.07 ± 13 min) to achieve preoperative MMSE score than desflurane group (51.2 ± 11.7 min).

Conclusion:

Both desflurane and sevoflurane have similar recovery profile in obese patients when anesthetic concentration is carefully titrated. Reversal of cognitive function is significantly earlier in obese patients anesthetized with sevoflurane.

Titration of sevoflurane anesthesia to optimize the time to regain airway reflexes in patients undergoing elective surgery: A randomized clinical trial comparing desflurane and sevoflurane anesthesia

BACKGROUND

Desflurane has adverse environmental effects, but has clinical advantages to speed emergence and return of protective airway reflexes compared with sevoflurane. We hypothesized that weaning of the inspired sevoflurane during the final 15 minutes of surgery would eliminate differences in airway reflex recovery between these agents.

METHODS

After obtaining IRB approval and informed consent, 40 patients undergoing elective surgery (≥1-hour) randomly received desflurane or sevoflurane. Patients swallowed 20 mL of water without drooling or coughing, and then received sedation and PONV pre-medication. Anesthesia was induced using propofol and fentanyl and maintained with desflurane or sevoflurane through a laryngeal mask airway maintaining a bispectral index of 45-50 and 50-60 during the final 15 minutes before surgery end. Cardiorespiratory variables and age-adjusted minimal alveolar concentration were recorded. The duration between anesthetic discontinuation and first appropriate response to command was measured; the laryngeal mask airway was removed. Two minutes after responding to command, patients were positioned semi-upright and attempted to swallow water. If successful swallowing was not achieved, the test was repeated every 4 minutes after each failure until successful swallowing was achieved.

RESULTS

Average anesthetic concentration and bispectral index was similar in patients receiving desflurane vs sevoflurane. Response times after discontinuation of anesthetics were similar. There were no differences in the recovery of swallowing ability between desflurane and sevoflurane groups.

CONCLUSION

Weaning of sevoflurane during the final 15 minutes of surgery eliminates clinical advantages of the more rapid return of airway reflexes with desflurane.

Society of Anesthesia and Sleep Medicine Guideline on Intraoperative Management of Adult Patients With Obstructive Sleep Apnea

The purpose of the Society of Anesthesia and Sleep Medicine Guideline on Intraoperative Management of Adult Patients With Obstructive Sleep Apnea (OSA) is to present recommendations based on current scientific evidence. This guideline seeks to address questions regarding the intraoperative care of patients with OSA, including airway management, anesthetic drug and agent effects, and choice of anesthesia type. Given the paucity of high-quality studies with regard to study design and execution in this perioperative field, recommendations were to a large part developed by subject-matter experts through consensus processes, taking into account the current scientific knowledge base and quality of evidence. This guideline may not be suitable for all clinical settings and patients and is not intended to define standards of care or absolute requirements for patient care; thus, assessment of appropriateness should be made on an individualized basis. Adherence to this guideline cannot guarantee successful outcomes, but recommendations should rather aid health care professionals and institutions to formulate plans and develop protocols for the improvement of the perioperative care of patients with OSA, considering patient-related factors, interventions, and resource availability. Given the groundwork of a comprehensive systematic literature review, these recommendations reflect the current state of knowledge and its interpretation by a group of experts at the time of publication. While periodic reevaluations of literature are needed, novel scientific evidence between updates should be taken into account. Deviations in practice from the guideline may be justifiable and should not be interpreted as a basis for claims of negligence.

Comparison of Haemodynamic Response to Inhalational Bolus with Desflurane in Normotensive and Hypertensive Patients Undergoing Laparoscopic Cholecystectomy

Objective

Desflurane causes sympathetic stimulation at high end-tidal concentrations. We conducted this study to compare the haemodynamic response to inhalational bolus with desflurane in normotensive and hypertensive patients undergoing laparoscopic cholecystectomy.

Methods

In this prospective, clinical trial, 40 patients aged 18-60 years and undergoing laparoscopic cholecystectomy were divided into normotensives (Group N; n=20) and hypertensives (Group H; n=20). Heart rate (HR), mean arterial pressure (MAP) and bispectral index (BIS) were measured at baseline and every 60 s for 5 min after induction, intubation, initiation and inhalational bolus of desflurane. The primary objective was to compare haemodynamic response, and the secondary objective was to assess the need for inhalational boluses and to compare the number of overcorrections and undercorrections in BIS value after each inhalational bolus. An independent t-test was used to compare the means of the study parameters between the groups, and a dependent t-test was used to compare the percentage change in the means of the study parameters within the same group. Statistical significance was defined as p<0.05.

Results

No statistically significant difference in the percentage of patients responding with a decrease, increase or no change of HR or MAP were seen between the two groups after inhalational bolus of desflurane. An overcorrection of BIS (value <45) was seen in 60% of the patients in Group H and 15% of the patients in Group N (p=0.003). None of the patients in either group had an undercorrection (BIS>55).

Conclusion

BIS-guided desflurane administration and BIS-triggered inhalational boluses of desflurane is safe, feasible and does not cause sympathetic stimulation in either normotensive or hypertensive patients.

Influence of Bayesian optimization on the performance of propofol target-controlled infusion

Background

Target controlled infusion (TCI) systems use population-based pharmacokinetic (PK) models that do not take into account inter-individual residual variation. This study compares the bias and inaccuracy of a population-based vs a personalized TCI propofol titration using Bayesian adaptation. Haemodynamic and hypnotic stability, and the prediction probability of alternative PK models, was studied.

Methods

A double-blinded, prospective randomized controlled trial of 120 subjects undergoing cardiac surgery was conducted. Blood samples were obtained at 10, 35, 50, 65, 75 and 120 min and analysed using a point-of-care propofol blood analyser. Bayesian adaptation of the PK model was applied at 60 min in the intervention group. Median (Absolute) Performance Error (Md(A)PE) was used to evaluate the difference between bias and inaccuracy of the models. Haemodynamic (mean arterial pressure [MAP], heart rate) and hypnotic (bispectral index [BIS]) stability was studied. The predictive performance of four alternative propofol PK models was studied.

Results

MdPE and MdAPE did not differ between groups during the pre-adjustment period (control group: 6.3% and 16%; intervention group: 5.4% and 18%). MdPE differed in the post-adjustment period (12% vs. -0.3%), but MdAPE did not (18% vs. 15%). No difference in heart rate, MAP or BIS was found. Compared with the other models, the Eleveld propofol PK model (patients) showed the best prediction performance.

Conclusions

When an accurate population-based PK model was used for propofol TCI, Bayesian adaption of the model improved bias but not precision.

Clinical trial registration

Dutch Trial Registry NTR4518.

A comparison of propofol-to-BIS post-operative intensive care sedation by means of target controlled infusion, Bayesian-based and predictive control methods: an observational, open-label pilot study

Purpose

We evaluated the feasibility and robustness of three methods for propofol-to-bispectral index (BIS) post-operative intensive care sedation, a manually-adapted target controlled infusion protocol (HUMAN), a computer-controlled predictive control strategy (EPSAC) and a computer-controlled Bayesian rule-based optimized control strategy (BAYES).

Methods

Thirty-six patients undergoing short lasting sedation following cardiac surgery were included to receive propofol to maintain a BIS between 40 and 60. Robustness of control for all groups was analysed using prediction error and spectrographic analysis.

Results

Although similar time courses of measured BIS were obtained in all groups, a higher median propofol effect-site concentration (CePROP) was required in the HUMAN group compared to the BAYES and EPSAC groups. The time course analysis of the remifentanil effect-site concentration (CeREMI) revealed a significant increase in CeREMI in the EPSAC group compared to BAYES and HUMAN during the case. Although similar bias and divergence in control was found in all groups, larger control inaccuracy was observed in HUMAN versus EPSAC and BAYES. Spectrographic analysis of the system behavior shows that BAYES covers the largest spectrum of frequencies, followed by EPSAC and HUMAN.

Conclusions

Both computer-based control systems are feasible to be used during ICU sedation with overall tighter control than HUMAN and even with lower required CePROP. EPSAC control required higher CeREMI than BAYES or HUMAN to maintain stable control.

Clinical trial number: NCT00735631.

Electronic supplementary material

The online version of this article (10.1007/s10877-018-0208-2) contains supplementary material, which is available to authorized users.

Bispectral index-guided general anaesthesia in combination with interscalene block reduces desflurane consumption in arthroscopic shoulder surgery: a clinical comparison of bupivacaine versus levobupivacaine

BACKGROUND

The goal of this study was to compare the influence of an interscalene brachial plexus block (ISB) performed with either bupivacaine or levobupivacaine in conjunction with general anaesthesia (GA) on desflurane consumption, which was titrated to maintain the recovery profiles and postoperative analgesia while also keeping the bispectral index score (BIS) between 40 and 60 in patients undergoing arthroscopic shoulder surgery.

METHODS

Sixty patients undergoing arthroscopic shoulder surgery were prospectively randomized to receive GA with desflurane alone (group C) or in combination with a preoperative ISB by either bupivacaine 0.25 % (group B) 40 ml or levobupivacaine 0.25 % (group L) 40 ml. BIS scores or respiratory and hemodynamic parameters during the operation, recovery characteristics, consumed doses of desflurane and pain intensities were evaluated.

RESULTS

The eye opening time was 4.0 ± 2.5 minutes for group B, 4.6 ± 2.4 minutes for group L, and 6.2 ± 2.1 minutes for group C (p < 0.05). Group B and group L saved 36 % and 25 % desflurane per unit time respectively when compared with group C (p < 0.001and p < 0.05) while the mean pain scores and analgesic requirements the first day after surgery were higher in group C (p < 0.05).

CONCLUSIONS

Because of lower desflurane consumption, a superior recovery profile, and a high degree of patient acceptance, general anaesthesia in combination with interscalene block may be preferred in arthroscopic shoulder surgery.

TRIAL REGISTRATION

The trial registration number is ACTRN12613000381785.

Postoperative recovery after anesthesia in morbidly obese patients: a systematic review and meta-analysis of randomized controlled trials

PURPOSE

Obese patients present a challenge to safe general anesthesia because of impaired cardiopulmonary physiology and increased risks of aspiration and acute upper airway obstruction. Since studies are lacking regarding the postoperative effects on recovery from general anesthesia in morbidly obese patients, we conducted a systematic review and meta-analysis of recovery outcomes in morbidly obese patients who had undergone general anesthesia.

SOURCE

We systematically searched the PubMed, EMBASE™, Cochrane, and Scopus™ databases for randomized controlled trials that evaluated the outcome of anesthesia with desflurane, sevoflurane, isoflurane, or propofol in morbidly obese patients. Using a random effects model, we conducted meta-analyses to assess recovery times (eye opening, hand squeezing, tracheal extubation, and stating name or birth date), time to discharge from the postanesthesia care unit (PACU), and the incidence and severity of postoperative nausea and vomiting (PONV).

PRINCIPAL FINDINGS

We reviewed results for 11 trials and found that patients given desflurane took less time: to respond to commands to open their eyes (weighted mean difference [WMD] -3.10 min; 95% confidence interval (CI): -5.13 to -1.08), to squeeze the investigator's hand (WMD -7.83 min; 95% CI: -8.81 to -6.84), to be prepared for tracheal extubation (WMD -3.88 min; 95% CI: -7.42 to -0.34), and to state their name (WMD -7.15 min; 95% CI: -11.00 to -3.30). We did not find significant differences in PACU discharge times, PONV, or the PACU analgesic requirement.

CONCLUSION

Postoperative recovery was significantly faster after desflurane than after sevoflurane, isoflurane, or propofol anesthesia in obese patients. No clinically relevant differences were observed regarding PACU discharge time, incidence of PONV, or postoperative pain scores. The systematic review was registered with PROSPERO (CRD42014009480).

Turkish Anaesthesiologist's Experiences of Anaesthetic Management of Patients with Obstructive Sleep Apnea (OSA)

OBJECTIVE

Obstructive sleep apnea (OSA) is an important health problem that is increasing with the increase in the incidence of obesity. For patients with OSA, it is reported that preoperative OSA diagnosis is made in only 10%-20% of the patients. Therefore, it gains importance that these patients are diagnosed in the preoperative period. The aim of this study is to analyze with a survey the experiences of anaesthesia experts working in Turkey about the diagnosis of patients with OSA, anaesthetic methods and postoperative care.

METHODS

The study was completed with an online survey form distributed via email. Survey participants were sent an email, and those experts who wished to participate clicked on the link, answered the questions and returned the survey via email.

RESULTS

A total of 134 anaesthesia experts participated in this study. While 97% of the participating anaesthetists considered diagnosis of patients with OSA to be important, only 53% trusted themselves to recognize this patient group. Of the total number of participants. 43% did not know the STOP-BANG test used in the preoperative period to diagnose patients with OSA. The percentage who thought that patients with OSA would increase the incidence of difficult intubation was 84%. In the intraoperative period, the percentage who chose inhalation anaesthetics was 35%, whereas the rate of those who chose total intravenous anesthesia (TIVA) was 48%.

CONCLUSION

This study indicates that the medical knowledge of Turkish anaesthetists on the topic of OSA requires updating. In addition, we believe a practical guide to standardize the diagnosis and preoperative/perioperative management of patients with OSA should be prepared for Turkish anaesthetists.

Hemodynamics and early recovery characteristics of desflurane versus sevoflurane in bariatric surgery

Context:

Morbidly obese patients are prone for intraoperative hemodynamic disturbances and postoperative airway complications.

Aim:

Comparison of intraoperative hemodynamics and postoperative recovery characteristics of desflurane versus sevoflurane in morbidly obese patients undergoing laparoscopic bariatric surgery.

Settings and Design:

Randomized controlled trial

Materials and Methods:

After institutional ethics committee approval and written informed consent, 40 morbidly obese patients (BMI > 35 kg/m²) were randomized to receive desflurane or sevoflurane as part of a standardized general anesthesia technique. Volatile anesthetic concentration was titrated to maintain electroencephalographic bispectral index score (BIS) in the range of 40-60. Mean arterial pressure (MAP) and heart rate (HR) were recorded preoperatively, at induction and intubation, then at regular intervals. After extubation, early recovery was recorded by time to emergence and orientation to time and place. In post anesthesia care unit, intermediate recovery was assessed by modified Aldrete Score and Digit Symbol Substitution Test (DSST).

Results:

Intraoperative MAP and HR did not differ between the two groups (P > 0.05). The time to response to painful stimuli, obeying verbal commands and spontaneous eye opening was shorter (P = 0.001) and modified Aldrete Score was higher after desflurane anesthesia than after sevoflurane anesthesia (P = 0.049). DSST also returned towards normal faster after desflurane (28.50 ± 6.30 min vs. 35.0 ± 5.62 min, P = 0.03).

Conclusions:

Both desflurane and sevoflurane produce similar hemodynamic changes but the immediate and intermediate recovery was significantly faster after desflurane thus contributing to fast tracking and early discharge of patients.

Anesthetic Pharmacology and the Morbidly Obese Patient

Anesthesiologists are increasingly being faced with treating obese patients. Physiologic and anthropometric associated with obesity-most notably increases in cardiac output, changes in tissue perfusion and increases in total body weight (TBW), lean body weight (LBW), and fat mass affect the pharmacokinetics (PK) of anesthetic agents. In addition, redundancy of airway tissue, obstructive and central sleep apnea and CO2 retention affect the pharmacodynamics (PD) of anesthetics and narrow the therapeutic window of numerous anesthetic drugs. Safe and effective pharmacologic management of the obese patient requires a thorough understanding of how obesity affects the PK and PD of anesthetics.

Brief review: theory and practice of minimal fresh gas flow anesthesia

PURPOSE

The aim of this brief review is to provide an update on the theory regarding minimal fresh gas flow techniques for inhaled general anesthesia. The article also includes an update and discussion of the practical aspects associated with minimal-flow anesthesia, including the advantages, potential limitations, and safety considerations of this important anesthetic technique.

PRINCIPAL FINDINGS

Reducing the fresh gas flow to < 1 L·min(-1) during maintenance of anesthesia is associated with several benefits. Enhanced preservation of temperature and humidity, cost savings through more efficient utilization of inhaled anesthetics, and environmental considerations are three key reasons to implement minimal-flow and closed-circuit anesthesia, although potential risks are hypoxic gas mixtures and inadequate depth of anesthesia. The basic elements of the related pharmacology need to be considered, especially pharmacokinetics of the inhaled anesthetics. The third-generation inhaled anesthetics, sevoflurane and desflurane, have low blood and low tissue solubility, which facilitates rapid equilibration between the alveolar and effect site (brain) concentrations and makes them ideally suited for low-flow techniques. The use of modern anesthetic machines designed for minimal-flow techniques, leak-free circle systems, highly efficient CO(2) absorbers, and the common practice of utilizing on-line real-time multi-gas monitor, including essential alarm systems, allow for safe and cost-effective minimal-flow techniques during maintenance of anesthesia. The introduction of new anesthetic machines with built-in closed-loop algorithms for the automatic control of inspired oxygen and end-tidal anesthetic concentration will further enhance the feasibility of minimal-flow techniques.

CONCLUSIONS

With our modern anesthesia machines, reducing the fresh gas flow of oxygen to 0.3-0.5 L·min(-1) and using third-generation inhaled anesthetics provide a reassuringly safe anesthetic technique. This environmentally friendly practice can easily be implemented for elective anesthesia; furthermore, it will facilitate cost savings and improve temperature homeostasis.

Desflurane - revisited

The search for an ideal inhalational general anesthetic agent continues. Desflurane, which was recently introduced in the Indian market, possesses favorable pharmacokinetic and pharmacodynamic properties and is closer to the definition of an ideal agent. It offers the advantage of precise control over depth of anesthesia along with a rapid, predictable, and clear-headed recovery with minimal postoperative sequelae, making it a valuable anesthetic agent for maintenance in adults and pediatric patients in surgeries of all durations. The agent has advantages when used in extremes of age and in the obese. Its use may increase the direct costs of providing anesthetic care. Methods or techniques, such as low-flow anesthesia, to reduce the overall cost and along with minimal environmental implications must be followed.

[Anesthesia and bariatric surgery]

Today obesity is accepted as an independent disease. The WHO describes obesity as an epidemic disease occurring worldwide and associated comorbidities affect all organ systems. Bariatric operations lead to an improvement or even complete remission of obesity-correlated comorbidities. Bariatric operations are conducted as restrictive, malabsorptive, or mixed procedures. The preoperative anesthetic evaluation of comorbidities is carried out with a special focus on preexisting impairments of cardiac and lung function (e.g. cardiomyopathy, obstructive respiratory dysfunctions). Extremely obese patients are at risk of aspiration. Airway management at anesthesia induction includes normal intubation or, if additional risk factors are present, either fiber optic awake intubation or rapid sequence induction. The pharmacokinetics of all applicable drugs are altered in extremely obese patients and they are at risk for developing postoperative thromboembolic complications with a high mortality rate. Therefore early and sufficient thrombotic prophylaxis is important.

Control of the haemodynamic response to surgical stimuli in semi-closed circuit or closed circuit anaesthesia using a multifunctional anaesthesia system

This study compared the ability of the Zeus multifunctional anaesthesia system to control haemodynamic response to surgical stimulation in semi-closed (SCA) or closed circuit anaesthesia (CCA) modes. Fifty patients undergoing gynaecological surgery were randomly assigned to SCA or CCA. Anaesthesia was induced with 2 mg propofol and 0.9 mg/kg rocuronium, intravenously, and maintained using sevoflurane (minimum alveolar concentration [MAC], 1.0) using 2 l/min oxygen plus 2 l/min nitrous oxide (SCA 4 l/min group) or 50% oxygen plus 50% nitrous oxide (CCA group). An increase in mean arterial pressure (MAP) > 20% above baseline in response to surgical stimulation provoked a stepwise increase in sevoflurane (1.3 MAC and then 1.6 MAC), followed by fentanyl 1 pg/kg intravenously (rescue drug). The time required for MAP to return to within 10% of baseline was significantly shorter in the CCA group (6.4 +/- 3.6 min) compared with the SCA 4 l/min group (10.2 +/- 6.0 min). The percentage of patients requiring fentanyl was significantly greater in the SCA 4 l/min group than in the CCA group. In conclusion, CCA controlled acute haemodynamic responses to surgical stimuli more successfully and rapidly than SCA 4 l/min, using a multifunctional anaesthesia machine.

A Comparison of Consumption and Recovery Profiles According to Anaesthetic Circuit Mode using a New Multifunctional Closed-Circuit Anaesthesia System during Desflurane Anaesthesia: A Clinical Study

This clinical study compared induction time, consumed anaesthetic dose, and haemodynamic and recovery profiles when using a new type of multifunctional anaesthesia machine (Zeus®) in semi-closed or closed circuit modes. Sixty female patients undergoing gynaecological surgery were randomly assigned to three groups and received desflurane anaesthesia through a semi-closed circuit (SCC) at fresh gas flow rates of 4 l/min (SCC 4 l/min) or 2 l/min (SCC 2 l/min), or through a closed circuit (CC). Anaesthesia was maintained at the minimum alveolar concentration for blocking the adrenergic response to painful stimulus (MACBAR) (4.6% end-tidal desflurane) during each operation. The time required to reach MACBAR was significantly shorter and the dose of desflurane was significantly smaller in the CC group compared with the other groups. There were no differences in haemodynamic and recovery profiles between the groups. It is concluded that the CC mode allowed a faster and more reliable induction, lower anaesthetic consumption and stable haemodynamic and recovery profiles.

Faster wash-out and recovery for desflurane vs sevoflurane in morbidly obese patients when no premedication is used

BACKGROUND

The aim of this study was to compare desflurane vs sevoflurane kinetics and dynamics in morbidly obese patients and their recovery profile when no premedication had been used.

METHODS

Twenty-eight unpremedicated obese patients were randomly allocated to receive either sevoflurane (n = 14) or desflurane (n = 14) as the main anaesthetic agent. After induction of anaesthesia, either sevoflurane 2% or desflurane 6% was administered for 30 min via a non-rebreathing circuit. The kinetics of sevoflurane and desflurane were determined by measuring and recording end-tidal samples during this time. The bispectral index was used to indicate the level of hypnosis. At the end of the procedure, the end-tidal concentrations of sevoflurane and desflurane were recorded during the first 5 min after stopping their administration. Time from discontinuation of the anaesthetic drugs to eye opening on verbal command, squeezing the observer's hand on command, extubation, stating their name, giving their correct date of birth, discharge from the recovery room, and duration of the surgery and anaesthesia were also recorded.

RESULTS

The F(A)/F(I) ratio was significantly higher in the desflurane group from the 15th to the 30th min. The wash-out phase was faster for desflurane during the total observation period. When desflurane was used, recovery was also faster.

CONCLUSIONS

Desflurane provides faster wash-in and wash-out than sevoflurane in morbidly obese patients, and recovery is much faster after desflurane administration when no premedication has been used.

Influence of intraoperative opioid on postoperative pain and pulmonary function after laparoscopic gastric banding: remifentanil TCI vs sufentanil TCI in morbid obesity

BACKGROUND

Choice of opioid may influence postoperative pain, recovery, and respiratory homeostasis in morbid obesity. The aim of this study was to compare the effects of target-controlled infusions (TCIs) of remifentanil or sufentanil on postoperative analgesia, recovery, and pulmonary function after laparoscopic gastric banding.

METHODS

Forty morbidly obese patients undergoing laparoscopic gastric banding received BIS-guided desflurane anaesthesia combined with remifentanil TCI (Group R) or sufentanil TCI (Group S). Intraoperative haemodynamic stability, BIS controllability, and immediate recovery in the operating room were measured. Pulmonary function, modified Aldrete score, modified Observers Assessment of Alertness and Sedation score, blood gas analysis, and visual analogue score for pain and postoperative nausea and vomiting were measured on admission to the post-anaesthesia care unit and 30, 60, 120 min afterwards. After operation, patients received patient-controlled analgesia with morphine.

RESULTS

During the first two postoperative hours, cumulative morphine consumption was higher in the remifentanil group compared with the sufentanil group, but was equal values after that time. Recovery profiles and spirometry showed no significant differences. During maintenance, remifentanil gave a better haemodynamic stability.

CONCLUSIONS

As few differences occurred in the postoperative period, the theoretical advantage of remifentanil over the longer acting sufentanil can be questioned when using TCI technology.

Anesthetic complications of gross obesity

PURPOSE OF REVIEW

The number of obese patients undergoing anesthesia and surgery is increasing. This article aims to present recent achievements in the management of gross and morbidly obese patients in order to improve safety.

RECENT FINDINGS

Current investigations have demonstrated that the type of anesthesia (total intravenous anesthesia or volatile) and the anesthetics used have an important influence on the perioperative period, especially on postanesthesia recovery and respiratory failure during the postoperative period. These findings were compared with previous publications. Practical advice is also presented for performing successful intubation and mechanical ventilation in the morbidly obese patient, as well as describing drug dosage and administration.

SUMMARY

The progress in anesthesia techniques and modern drugs allows for safe management of obese patients, with mortality decreasing in this group of patients.

Desflurane versus sevoflurane for laparoscopic gastroplasty in morbidly obese patients

STUDY OBJECTIVE

To determine if desflurane results in a faster emergence as measured by time to eye opening compared to sevoflurane in morbidly obese patients undergoing laparoscopic gastroplasty.

STUDY DESIGN

Prospective, randomized, double-blinded study.

SETTING

Tertiary care hospital.

PATIENTS

70 patients with a body mass index of 35 or higher undergoing laparoscopic gastroplasty.

INTERVENTIONS

Patients were randomized into two groups to receive either desflurane or sevoflurane for maintenance of general anesthesia.

MEASUREMENTS

Intraoperative measured variables included the time from when the inhalation agent was turned off (no agent delivered) to eye opening and the time from when the inhalation agent was turned off to extubation. Postanesthesia care unit (PACU)-measured variables on admission and at 15 minute intervals until discharge included oxygen saturation (Spo2), blood pressure, heart rate, pain and nausea Visual Analog Scale (VAS) scores, emesis, modified Aldrete score, and Mini-Mental Status (MMS) examination score.

MAIN RESULTS

No differences were noted in demographic data, total surgical operative time, times from turning inhalation agent off to eye opening and extubation, or average length of stay in PACU. No differences were noted with respect to pain VAS, treatment for pain, modified Aldrete scores, emesis, or treatment for postoperative nausea or emesis. Differences were noted in PACU nausea VAS at 15 minutes, PACU nausea VAS at discharge, and PACU-MMS score at 45 minutes; however, multivariate analysis of variance revealed no differences between groups over the repeated PACU measured time periods in nausea VAS (P=0.17) or in MMS (P=0.34). Higher heart rates in the desflurane group were observed during PACU admission (82.3+/-9.8 vs 74.4+/-13.4 bpm, P<0.01) and 15 minutes post PACU admission (79.4+/-12.1 vs 71.3+/-13.2 bpm, P=0.01).

CONCLUSIONS

In morbidly obese patients undergoing laparoscopic gastroplasty, emergence, as measured by time to eye opening, did not differ between desflurane and sevoflurane, with similar recovery characteristics.

Perianesthesia respiratory care of the bariatric patient

Our nation's obesity problem has reached epidemic proportions and is only projected to worsen. The morbidly obese patient is at risk for experiencing a multitude of health-related conditions. Morbidly obese patients are presenting for surgery at an increasing rate, especially with the growing popularity of weight-loss surgery. Therefore the perianesthesia nurse has to remain informed of optimal care strategies for this sometimes challenging population. The obese patient presents with distinct respiratory care considerations of which the perianesthesia nurse must be knowledgeable. This review article will specifically focus on the respiratory care of the bariatric patient presenting for surgery.

Choice of volatile anesthetic for the morbidly obese patient: sevoflurane or desflurane

STUDY OBJECTIVE

Morbid obesity is associated with significant comorbidities. Desflurane has a low fat-blood solubility coefficient and may be better suited in this population to achieve a rapid emergence; however, sevoflurane has favorable cardiorespiratory properties that might also prove advantageous in the morbidly obese (MO) patient. This study used careful drug titration to determine if emergence differences between sevoflurane and desflurane could be minimized in MO patients.

DESIGN

A randomized, prospective blinded study to determine the emergence profiles of desflurane and sevoflurane in MO patients when anesthetic drug titration is used.

SETTING

Operating room of the VA Medical Center, Milwaukee, Wis.

PATIENTS

Forty American Society of Anesthesiologists II and III, MO patients (body mass index > or = 35 kg/m2), who were scheduled for elective surgery predicted to last for more than 2 hours, were studied.

INTERVENTIONS

Patients were induced with fentanyl, midazolam, and propofol and maintained with desflurane or sevoflurane, mixed in air and oxygen. Intraoperative bispectral index (BIS) was targeted to 45 to 50 and to 60 in the last 15 minutes of surgery.

MEASUREMENTS

Intraoperative anesthetic concentration, BIS, and hemodynamics were recorded. During emergence, time to follow command and extubation were noted, with assessments of cognitive function via the Mini-Mental Status Test and psychomotor performance via the Digit Symbol Substitution Test. A blinded observer recorded key recovery events.

MAIN RESULTS

Demographic data (age, 61 [36-83] years; body mass index, 38 [35-47] kg/m2), surgical procedures, length of anesthesia (approximately 3.5 hours), adjuvant drugs, and intraoperative BIS, heart rate, and mean arterial pressure were not significantly different. Hemodynamics, time to follow commands and to extubation, and results of Digit Symbol Substitution Test and Mini-Mental Status Test did not differ between anesthetic groups during recovery.

CONCLUSIONS

There were no differences in emergence and recovery profiles in MO patients receiving desflurane or sevoflurane when anesthetic concentration was carefully titrated.

Illustrations of Inhaled Anesthetic Uptake, Including Intertissue Diffusion to and from Fat

Although several mathematical and computer simulations of inhaled anesthetic pharmacokinetics have been devised, their complexity sometimes limits an intuitive appreciation of the interactions produced by the determinants of kinetics. In this essay, we illustrate the factors that govern inhaled anesthetic pharmacokinetics with drawings that consider delivery of anesthetic by ventilation to the lungs and dispersion of the anesthetic to tissue depots by the circulation. The illustrations incorporate the effects of both blood flow and blood solubility as determinants of the extent of dispersion. They incorporate tissue volume and solubility as determinants of the capacity of the tissue depots. Capacity to hold (take up) anesthetic is depicted by areas representing specific tissues, and the extent of anesthetic movement is depicted by the length and breadth of arrows to and from the areas depicting capacity. The illustrations incorporate increasingly important elements to kinetics, such as obesity. Obesity increases the depots available for storage of anesthetic, including anesthetic that reaches fat by intertissue diffusion. Such anesthetic returns to the circulation to delay recovery in healthy and obese patients, particularly with more soluble anesthetics. However, the increased anesthetic in fat occurs at a lower partial pressure and thus might not influence emergence materially. We hope that these illustrations will allow anesthesia practitioners to appreciate the interactions of the factors that govern inhaled anesthetic pharmacokinetics.

Airway Reflexes Return More Rapidly After Desflurane Anesthesia Than After Sevoflurane Anesthesia

Patients given a more soluble inhaled anesthetic usually take longer to awaken from anesthesia than do patients given a less soluble anesthetic. In the present study, we tested whether such a delay in awakening was also associated with a delay in restoration of protective airway reflexes. Patients were randomly assigned to receive desflurane (n = 31) or sevoflurane (n = 33) via a laryngeal mask airway. Demographics did not differ between groups. The average minimum alveolar anesthetic concentration fraction for both groups was 0.62, and the mean (+/-sd) minimum alveolar anesthetic concentration hours was 1.00 +/- 0.68 for desflurane versus 0.95 +/- 0.57 for sevoflurane, although more patients given sevoflurane also received regional anesthesia (17 for sevoflurane and 8 for desflurane). The time from stopping anesthetic administration to appropriate response to command was longer after sevoflurane (5.5 +/- 3.1 versus 3.4 +/- 1.9 min; P < 0.01). In addition, the time from first response to command to ability to swallow 20 mL of water without coughing or drooling was longer after sevoflurane. At 2 min after responding to command, all patients given desflurane were able to swallow without coughing or drooling, whereas 55% of patients given sevoflurane coughed and/or drooled (P < 0.001). At 6 min after responding to command, 18% of patients given sevoflurane still could not swallow without coughing or drooling (P < 0.05). We conclude that desflurane allows an earlier return of protective airway reflexes.

Time course of inhaled anaesthetic drug delivery using a new multifunctional closed-circuit anaesthesia ventilator. In vitro comparison with a classical anaesthesia machine †

BACKGROUND

The aim of this study was to detail the time-course, defined as the changes in end-tidal drug concentration with time, and consumption of inhaled anaesthetics when using a multifunctional closed-circuit anaesthesia machine in various drug delivery modes, and to compare it with a classical anaesthesia machine using an out-of-circle vaporizer under high and low fresh gas flow conditions.

METHODS

Using an artificial test lung, sevoflurane and desflurane time-course and consumption were compared when using the Zeus apparatus (Dräger, Lubeck, Germany) with direct injection of inhaled anaesthetics or the Primus apparatus (Dräger, Lubeck, Germany) using a classical out-of-circle vaporizer. Anaesthetics were targeted at 1 and 2 MAC end-tidal during 15 min. For both apparatus, out-of-circle high and low fresh gas control (FGC) and for Zeus, auto-control (AC) modes (fixed fresh gas flow at 6 and 1 litre min(-1) and uptake mode) were compared. Time to reach target, initial overshoot and stability at target, and wash-out times were compared.

RESULTS

In FGC, an initial overshoot in end-tidal drug concentration is seen when using 6 litre min(-1) fresh gas flow and a slower time course is observed when using only 1 litre min(-1) in both apparatus. In auto-control mode, the time course of both sevoflurane and desflurane was very fast and not influenced by the changes in fresh gas flow. No overshoot at target was seen. At all settings, the wash-out times were faster when using Zeus than Primus. Inhaled anaesthetic consumption was lowest with the Zeus ventilator in uptake AC mode.

CONCLUSION

A combination of the fastest time course and lowest consumption of sevoflurane and desflurane was found when using the Zeus apparatus in AC uptake mode.