Context-sensitive half-time in multicompartment pharmacokinetic models for intravenous anesthetic drugs

Successful Second Awake Craniotomy Reoperation With Dexmedetomidine After an Initial Abandonment Case Due to Restlessness

Awake craniotomy (AC) is sometimes aborted due to poor arousal and restlessness. Dexmedetomidine (DEX), an α2-adrenoreceptor agonist, has sedative, analgesic, and anesthetic-sparing effects, with a low risk of respiratory depression, making it effective for intraoperative pain and agitation during the awake phase. We report a case in which AC was successfully performed in combination with low-dose continuous administration of DEX during reoperation in a patient who experienced poor arousal and restlessness during their first surgery, leading to the abandonment of AC. The patient is a 48-year-old male who is scheduled for AC reoperation. Two years ago, the first AC was scheduled and performed under anesthesia with propofol and remifentanil. However, AC was abandoned due to poor intraoperative arousal and restlessness. At reoperation, general anesthesia was induced with propofol and continuous administration of remifentanil (0.1 µg/kg/min); following anesthesia induction (continuous infusion of propofol, remifentanil, and a bolus infusion of fentanyl), DEX was also administered (0.2 µg/kg/hour). We performed a scalp nerve block. Before the awake phase, the propofol dose was decreased as was DEX to 0.1 µg/kg/hour, and propofol and remifentanil were discontinued. The patient gradually awoke without any agitation and restlessness 24 min after stopping propofol and remifentanil and could perform language tasks without any complications. In this case, AC was successfully performed in combination with continuous low-dose administration of DEX at the time of reoperation in a patient who experienced poor arousal and restlessness during their first operation and had to discontinue AC.

Effect of converting from propofol to remimazolam with flumazenil reversal on recovery from anesthesia in outpatients with mental disabilities: a randomized controlled trial

BACKGROUND

General anesthesia is often necessary for dental treatment of outpatients with mental disabilities. Rapid recovery and effective management of postoperative nausea and vomiting (PONV) are critical for outpatients. This study aimed to investigate the effect of transitioning from propofol to remimazolam with flumazenil reversal administered toward the end of surgery during propofol-based total intravenous anesthesia (TIVA) on recovery.

METHODS

Adults with mental disabilities scheduled to undergo dental treatment were randomly assigned to receive either propofol-based TIVA (Group P) or propofol-remimazolam-based TIVA with flumazenil reversal (Group PR). Propofol was replaced with remimazolam 1 h before the end of surgery in Group PR; moreover, 0.5 mg of flumazenil was administered after the neuromuscular blockade reversal agent. The primary outcome was the duration of stay in the post-anesthesia care unit (PACU). The secondary outcomes included time to eye-opening, time to extubation, occurrence of PONV, and quality of recovery.

RESULTS

Fifty-four patients were included in this study. The duration of stay in the PACU in Group PR was significantly shorter than that in Group P (mean difference, 8.7 min; confidence interval [95% CI], 3.3-14.2; P = 0.002). Group PR exhibited a shorter time to eye opening (mean difference, 5.4 min; 95% CI, 3.3-8.1; P < 0.001) and time to extubation (mean difference, 5.5 min; 95% CI, 3.6-7.9; P < 0.001) than Group P. Neither group required the administration of rescue analgesics, and the incidence of PONV was not reported.

CONCLUSIONS

Transitioning from propofol to remimazolam 1 h before the end of surgery followed by flumazenil reversal reduced the duration of stay in the PACU and the time to eye opening and extubation without affecting the incidence of PONV and quality of recovery.

TRIAL REGISTRATION NUMBER

Clinical Research Information Service (KCT0007794), Clinical trial first registration date: 12/10/2022.

Intraoperative Opioid Waste and Association of Intraoperative Opioid Dose with Postoperative Adverse Outcomes: A Hospital Registry Study

INTRODUCTION

Perioperative opioid use has been associated with adverse clinical outcomes. Additionally, opioid disposal carries significant costs, due to the waste of pharmaceutical products and the time needed by skilled labor to report the waste. In this study, we aimed to estimate costs and predict factors of opioid-associated intraoperative product waste, as well as to evaluate whether higher intraoperative opioid doses are associated with increased risk of adverse postoperative outcomes.

METHODS

We included 170,607 patients undergoing general anesthesia and receiving intraoperative fentanyl, hydromorphone, or morphine at Beth Israel Deaconess Medical Center, Boston, MA, USA, between January 2010 and June 2020. We estimated product waste-associated costs based on various opioid syringe sizes and determined predictors of opioid waste. Further, we evaluated whether higher opioid doses were associated with postoperative adverse events according to the severity-indexed, incident report-based medication error-reporting program classification. The primary outcome included post-extubation desaturation, postoperative nausea or vomiting, or postoperative somnolence or sedation.

RESULTS

The use of the smallest syringe sizes (50 mcg for fentanyl, 0.2 mg for hydromorphone, and 2 mg for morphine) resulted in the lowest product waste-associated costs. The main predictor of opioid waste was the administration of more than one intraoperative opioid (adjusted odds ratio [aOR] = 7.64, 95% CI 7.40-7.89, P < 0.001). Intraoperative doses of fentanyl > 50-100 mcg (aOR = 1.17 [1.10-1.25], P < 0.001, adjusted risk difference [ARD] 2%) and > 100 mcg (aOR = 1.24 [1.16-1.33], P < 0.001, ARD 3%), hydromorphone > 1 mg (aOR = 1.13 [1.06-1.20], P < 0.001, ARD 2%), and morphine > 2-4 mg (aOR = 1.26 [1.02-1.56], P = 0.04, ARD 3%) and > 4 mg (aOR = 1.45 [1.18-1.77], P < 0.001, ARD 5%) were associated with higher risk of the primary outcome.

CONCLUSION

Smaller syringe sizes of intraoperative opioids may help to reduce product waste and associated costs, as well postoperative adverse events through utilization of lower intraoperative opioid doses.

Paving the way to environment-friendly greener anesthesia

Health-care settings have an important responsibility toward environmental health and safety. The operating room is a major source of environmental pollution within a hospital. Inhalational agents and nitrous oxide are the commonly used gases during general anesthesia for surgeries, especially in the developing world. These greenhouse gases contribute adversely to the environmental health both inside the operating room and in the outside atmosphere. Impact of these anesthetic agents depends on the total consumption, characteristics of individual agents, and gas flows, with higher levels increasing the environmental adverse effects. The inimical impact of nitrous oxide is higher due to its longer atmospheric half-life and potential for destruction of the ozone layer. Anesthesiologist of today has a choice in the selection of anesthetic agents. Prudent decisions will help in mitigating environmental pollution and contributing positively to a greener planet. Therefore, a shift from inhalational to intravenous-based technique will reduce the carbon footprint of anesthetic agents and their impact on global climate. Propofol forms the mainstay of intravenous anesthesia technique and is a proven drug for anesthetic induction and maintenance. Anesthesiologists should appreciate growing concerns about the role of inhalational anesthetics on the environment and join the cause of environmental responsibility. In this narrative review, we revisit the pharmacological and pharmacokinetic considerations, clinical uses, and discuss the merits of propofol-based intravenous anesthesia over inhalational anesthesia in terms of environmental effects. Increased awareness about the environmental impact and adoption of newer, versatile, and user-friendly modalities of intravenous anesthesia administration will pave the way for greener anesthesia practice.

Postanesthesia Care Unit Recovery Time According to Volatile Anesthetic Used in Clinical Practice

BACKGROUND

Whether volatile anesthetic solubility affects postanesthesia recovery time in clinical practice is unclear. We investigated the association among 3 volatile agents and 2 clinically relevant outcomes-postanesthesia care unit (PACU) recovery time (time from PACU admission to fulfillment of discharge criteria) and oversedation (Richmond Agitation-Sedation Scale score ≤-3)-as a potential contributor to delaying PACU discharge. The volatile agents studied were isoflurane, desflurane, and sevoflurane. We hypothesized that increased solubility of the volatile agent (isoflurane versus desflurane or sevoflurane) would be associated with longer PACU recovery time and higher rates of oversedation.

METHODS

This retrospective observational study included adults (≥18 years) who underwent surgical procedures under general anesthesia with a volatile agent and were admitted to the PACU from May 5, 2018, to December 31, 2020. The primary outcome was PACU recovery time, and the secondary outcome was oversedation. PACU recovery time was log-transformed and analyzed with linear regression. Oversedation was analyzed by using logistic regression. To account for potential confounding, inverse probability of treatment weighting (IPTW) was used. Pairwise comparisons of the 3 agents were performed, with P < .017 (Bonferroni-adjusted) considered significant.

RESULTS

Of 47,847 patients included, 11,817 (24.7%) received isoflurane, 11,286 (23.6%) received desflurane, and 24,744 (51.7%) received sevoflurane. Sevoflurane had an estimated 4% shorter PACU recovery time (IPTW-adjusted median [interquartile range {IQR}], 61 [42-89] minutes) than isoflurane (64 [44-92] minutes) (ratio of geometric means [98.3% confidence interval {CI}], 0.96 [0.95-0.98]; P < .001). Differences in PACU recovery time between desflurane and the other agents were not significant. The IPTW-adjusted frequency of oversedation was 8.8% for desflurane, 12.2% for sevoflurane, and 16.7% for isoflurane; all pairwise comparisons were observed to be significant (odds ratio [98.3% CI], 0.70 [0.62-0.79] for desflurane versus sevoflurane, 0.48 [0.42-0.55] for desflurane vs isoflurane, and 0.69 [0.63-0.76] for sevoflurane versus isoflurane; all P < .001). Although oversedated patients had longer PACU recovery time, differences in the oversedation rate across agents did not result in meaningful differences in time to PACU recovery.

CONCLUSIONS

In clinical practice, only small, clinically unimportant differences in PACU recovery time were observed between the volatile anesthetics. Although oversedation was associated with increased PACU recovery time, differences in the rate of oversedation among agents were insufficient to produce meaningful differences in overall PACU recovery time across the 3 volatile agents. Practical attempts to decrease PACU recovery time should address factors other than volatile agent selection.

Pharmacokinetics of remimazolam after intravenous infusion in anaesthetised children

BACKGROUND

The pharmacokinetic properties of the new benzodiazepine remimazolam have been studied only in adults. We investigated the pharmacokinetics of remimazolam after i.v. infusion in anaesthetised paediatric patients.

METHODS

Twenty-four children (2-6 yr, ASA physical status 1-2, BMI 15-18 kg m-2) undergoing general anaesthesia with sevoflurane were enrolled. During surgery, remimazolam was administered as an i.v. infusion over 1 h at 5 mg kg-1 h-1 for 5 min, followed by 1.5 mg kg-1 h-1 for 55 min. Plasma concentrations of remimazolam and its metabolite CNS7054 were determined from arterial blood samples using ultra-high performance liquid chromatography-mass spectrometry. Pharmacokinetic modelling was performed by population analysis.

RESULTS

Pharmacokinetics were best described by a three-compartment model for remimazolam and a two-compartment model for CNS7054 linked by a transit compartment. Remimazolam showed a high clearance of 15.9 (12.9, 18.2) ml kg-1 min-1 (median, Q25, Q75), a small central volume of distribution of 0.11 (0.08, 0.14) L kg-1 and a short terminal half-life of 67 (49, 85) min. The context-sensitive half-time after an infusion of 4 h was 17 (12, 21) min. The metabolite CNS7054 showed a low clearance of 0.89 (0.33, 1.40) ml kg-1 min-1, a small central volume of distribution of 0.011 (0.005, 0.016) L kg-1, and a long terminal half-life of 321 (230, 770) min.

CONCLUSIONS

Remimazolam in children was characterised by a high clearance and short context-sensitive half-time. When normalised to weight, pharmacokinetic properties were similar to those reported for adults.

CLINICAL TRIAL REGISTRATION

ChiCTR2200057629.

Initial loading of dexmedetomidine and continuous propofol sedation for prevention of delayed recovery: A randomized controlled trial

BACKGROUND

Sedation with continuous dexmedetomidine and bolus midazolam administration provides a lower incidence of unacceptable patient movement during procedures but requires a longer recovery time. The authors aimed to compare recovery time and unacceptable patient movement during sedation with initial loading of dexmedetomidine followed by continuous propofol infusion with those during sedation with continuous dexmedetomidine and bolus midazolam administration.

METHODS

In this prospective randomized controlled trial, 54 patients undergoing dental surgery and requiring intravenous sedation were assigned to either the dexmedetomidine and propofol group (n = 27, dexmedetomidine administered at 6 μg/kg/h for 5 minutes, followed by continuous propofol infusion using a target-controlled infusion) or the dexmedetomidine and midazolam group (n = 27, dexmedetomidine administered at 0.2-0.7 μg/kg/h continuously after the same initial loading dose with bolus midazolam). A bispectral index of 70 through 80 was maintained during the procedure. Patient movement that interfered with the procedure and time from the end of sedation to achieving a negative Romberg sign were assessed.

RESULTS

Times from the end of sedation to achieving a negative Romberg sign in the dexmedetomidine and propofol group (median, 14 minutes [interquartile range, 12-15 minutes]) were significantly shorter (P < .001) than in the dexmedetomidine and midazolam group (median, 22 minutes [interquartile range, 17.5-30.5 minutes]). The incidence of unacceptable patient movement was comparable between groups (n = 3 in the dexmedetomidine and propofol group, n = 4 in the dexmedetomidine and midazolam group; P = .999).

CONCLUSIONS

Sedation with a single loading dose of dexmedetomidine followed by continuous propofol infusion can prevent delayed recovery without increasing unacceptable patient movement.

PRACTICAL IMPLICATIONS

The combination of dexmedetomidine and propofol may provide high-quality sedation for ambulatory dental practice. This clinical trial was registered in the University Hospital Medical Information Network Clinical Trials Registry. The registration number is UMIN000039668.

Effects of epileptiform activity on discharge outcome in critically ill patients in the USA: a retrospective cross-sectional study

BACKGROUND

Epileptiform activity is associated with worse patient outcomes, including increased risk of disability and death. However, the effect of epileptiform activity on neurological outcome is confounded by the feedback between treatment with antiseizure medications and epileptiform activity burden. We aimed to quantify the heterogeneous effects of epileptiform activity with an interpretability-centred approach.

METHODS

We did a retrospective, cross-sectional study of patients in the intensive care unit who were admitted to Massachusetts General Hospital (Boston, MA, USA). Participants were aged 18 years or older and had electrographic epileptiform activity identified by a clinical neurophysiologist or epileptologist. The outcome was the dichotomised modified Rankin Scale (mRS) at discharge and the exposure was epileptiform activity burden defined as mean or maximum proportion of time spent with epileptiform activity in 6 h windows in the first 24 h of electroencephalography. We estimated the change in discharge mRS if everyone in the dataset had experienced a specific epileptiform activity burden and were untreated. We combined pharmacological modelling with an interpretable matching method to account for confounding and epileptiform activity-antiseizure medication feedback. The quality of the matched groups was validated by the neurologists.

FINDINGS

Between Dec 1, 2011, and Oct 14, 2017, 1514 patients were admitted to Massachusetts General Hospital intensive care unit, 995 (66%) of whom were included in the analysis. Compared with patients with a maximum epileptiform activity of 0 to less than 25%, patients with a maximum epileptiform activity burden of 75% or more when untreated had a mean 22·27% (SD 0·92) increased chance of a poor outcome (severe disability or death). Moderate but long-lasting epileptiform activity (mean epileptiform activity burden 2% to <10%) increased the risk of a poor outcome by mean 13·52% (SD 1·93). The effect sizes were heterogeneous depending on preadmission profile-eg, patients with hypoxic-ischaemic encephalopathy or acquired brain injury were more adversely affected compared with patients without these conditions.

INTERPRETATION

Our results suggest that interventions should put a higher priority on patients with an average epileptiform activity burden 10% or greater, and treatment should be more conservative when maximum epileptiform activity burden is low. Treatment should also be tailored to individual preadmission profiles because the potential for epileptiform activity to cause harm depends on age, medical history, and reason for admission.

FUNDING

National Institutes of Health and National Science Foundation.

Reduced suicidality after electroconvulsive therapy is linked to increased frontal brain activity in depressed patients: a resting-state fMRI study

Objective

Suicidality is commonly observed in patients with depressive episodes, and electroconvulsive therapy (ECT) has been found to be effective in treating these patients. However, the role of ECT in suicidality remains unclear. This study used resting-state functional magnetic resonance imaging (rs-fMRI) to explore the changes in brain function before and after ECT in depressed patients with suicidality.

Methods

In total, 26 depressed patients with suicidality underwent rs-fMRI at baseline and after 8-12 sessions of ECT. In addition, 32 healthy controls (HCs) matched for age, gender, and educational level underwent rs-fMRI once. The amplitude of low-frequency fluctuations (ALFF), the fractional amplitude of low-frequency fluctuations (fALFF), and regional homogeneity (ReHo) were measured to evaluate whole brain function. Differences between the groups and time points (before and after ECT) were compared. Clinical symptoms were assessed using the 17-item Hamilton Depression Scale (HAMD-17) and Beck Scale for Suicide Ideation (BSSI).

Results

At baseline, patients exhibited decreased ALFF in the right postcentral and precentral gyrus and decreased fALFF in the right supramarginal and postcentral gyrus, left superior frontal gyrus (SFG), as well as the superior and middle temporal gyrus compared to HCs. Patients also had lower ReHo in the left amygdala, anterior cingulate, and postcentral gyrus, and in the right thalamus, insula, and postcentral gyrus. They also exhibited higher ALFF in the bilateral temporal gyrus and insula as well as higher fALFF in the cerebellum. Following ECT, fALFF in the left SFG and orbital frontal cortex (OFC) significantly increased and was inversely correlated with the reduction of BSSI scores (r = -0.416, p = 0.048), whereas no correlation was found with changes in HAMD-17scores.

Conclusion

Our findings suggest that the left SFG and OFC may play a key role in the mechanism of ECT for suicidality. The decrease of fALFF in the left SFG and OFC may represent a potential mechanism through which ECT effectively treats suicidality in depressed patients.

Ketamine-propofol (ketofol) in procedural sedation: a narrative review

Sedation methods for dental treatment are increasingly explored. Recently, ketofol, which is a combination of ketamine and propofol, has been increasingly used because the advantages and disadvantages of propofol and ketamine complement each other and increase their effectiveness. In this review, we discuss the pharmacology of ketamine and propofol, use of ketofol in various clinical situations, and differences in efficacy between ketofol and other sedatives.

Perioperative opioids: a narrative review contextualising new avenues to improve prescribing

Opioids have dominated the management of perioperative pain in recent decades with higher doses than ever before used in some circumstances. Through the expanding use of opioids, growing research has highlighted their associated side-effects and the intertwined phenomena of acute withdrawal syndrome, opioid tolerance, and opioid-induced hyperalgesia. With multiple clinical guidelines now endorsing multimodal analgesia, a diverse array of opioid-sparing agents emerges and has been studied to variable degrees, including techniques of opioid-free anaesthesia. It remains unclear to what extent such methods should be adopted, yet current evidence does suggest dependence on opioids as the primary perioperative analgesic might not meet the principles of 'rational prescribing' as described by Maxwell. In this narrative review we describe how, using current evidence, a patient-centred rational-prescribing approach can be applied to opioids in the perioperative period. To contextualise this approach, we discuss the historical adoption of opioids in anaesthesia, our growing understanding of associated side-effects and emerging strategies of opioid-sparing and opioid-free anaesthesia. We discuss avenues and challenges for improving opioid prescribing to limit persistent postoperative opioid use and how these may be incorporated into a rational-prescribing approach.

Mechanical Ventilation in Patients with Traumatic Brain Injury: Is it so Different?

Patients with traumatic brain injury (TBI) frequently require invasive mechanical ventilation and admission to an intensive care unit. Ventilation of patients with TBI poses unique clinical challenges, and careful attention is required to ensure that the ventilatory strategy (including selection of appropriate tidal volume, plateau pressure, and positive end-expiratory pressure) does not cause significant additional injury to the brain and lungs. Selection of ventilatory targets may be guided by principles of lung protection but with careful attention to relevant intracranial effects. In patients with TBI and concomitant acute respiratory distress syndrome (ARDS), adjunctive strategies include sedation optimization, neuromuscular blockade, recruitment maneuvers, prone positioning, and extracorporeal life support. However, these approaches have been largely extrapolated from studies in patients with ARDS and without brain injury, with limited data in patients with TBI. This narrative review will summarize the existing evidence for mechanical ventilation in patients with TBI. Relevant literature in patients with ARDS will be summarized, and where available, direct data in the TBI population will be reviewed. Next, practical strategies to optimize the delivery of mechanical ventilation and determine readiness for extubation will be reviewed. Finally, future directions for research in this evolving clinical domain will be presented, with considerations for the design of studies to address relevant knowledge gaps.

Association Between Anesthesia Provider Education and Carbon Footprint Related to the Use of Inhaled Halogenated Anesthetics

BACKGROUND

Inhaled halogenated anesthetics are responsible for half of operating room total greenhouse gas emissions. Sustainable anesthesia groups were set up in 4 Lyon, France, university hospitals (Hospices Civils de Lyon) in January 2018 and have supported a specific information campaign about the carbon footprint related to the use of inhaled halogenated anesthetics in June 2019. We aimed to assess whether implementing such information campaigns was associated with a decrease in the carbon footprint related to inhaled halogenated anesthetics.

METHODS

This retrospective cohort study was conducted from January 1, 2015, to February 29, 2020, in 4 hospitals of the Hospices Civils de Lyon in France. Information meetings on sustainable anesthesia practices were organized by sustainable anesthesia groups that were set up in January 2018. In addition, a specific information campaign about the carbon footprint related to inhaled halogenated anesthetics was conducted in June 2019; it was followed by a questionnaire to be completed online. The monthly purchase of sevoflurane, desflurane, and propofol was recorded, and the estimated monthly carbon footprint from desflurane- and sevoflurane-related perioperative emissions was calculated. The interrupted time-series data from January 2015 to February 2020 were analyzed by segmented regression, considering both interventions (setting up of the sustainable anesthesia groups and specific information campaign) in the analysis and adjusting for 2 confounding factors (seasonality of the data and number of general anesthesia uses).

RESULTS

Among the 641 anesthesia providers from the study hospitals, 121 (19%) attended the information meetings about the carbon footprint of inhaled halogenated anesthetics, and 180 (28%) completed the questionnaire. The anesthetic activity from all 641 providers was considered in the analysis. After the sustainable anesthesia groups were set up, the carbon footprint of sevoflurane and desflurane started decreasing: the slope significantly changed ( P < .01) and became significantly negative, from -0.27 (95% confidence interval [CI], -1.08 to 0.54) tons.month -1 to -14.16 (95% CI, -16.67 to -11.65) tons.month -1 . After the specific information campaign, the carbon footprint kept decreasing, with a slope of -7.58 (95% CI, -13.74 to -1.41) tons.month -1 ( P = .02), which was not significantly different from the previous period ( P = .07).

CONCLUSIONS

The setup of the sustainable anesthesia groups was associated with a dramatic reduction in the carbon footprint related to halogenated anesthetics. These results should encourage health care institutions to undertake information campaigns toward anesthesia providers so that they also take into account the environmental impact in the choice of anesthetic drugs, in addition to the benefits for the patient and economic concerns.

Interactions of the protease inhibitor, ritonavir, with common anesthesia drugs

The protease inhibitor, ritonavir, is a strong inhibitor of CYP 3A. The drug is used for management of the human immunovirus and is currently part of an oral antiviral drug combination (nirmatrelvir-ritonavir) for the early treatment of SARS-2 COVID-19-positive patients aged 12 years and over who have recognized comorbidities. The CYP 3A enzyme system is responsible for clearance of numerous drugs used in anesthesia (e.g., alfentanil, fentanyl, methadone, rocuronium, bupivacaine, midazolam, ketamine). Ritonavir will have an impact on drug clearances that are dependent on ritonavir concentration, anesthesia drug intrinsic hepatic clearance, metabolic pathways, concentration-response relationship, and route of administration. Drugs with a steep concentration-response relationship (ketamine, midazolam, rocuronium) are mostly affected because small changes in concentration have major changes in effect response. An increase in midazolam concentration is observed after oral administration because CYP 3A in the gastrointestinal wall is inhibited, causing a large increase in relative bioavailability. Fentanyl infusion may be associated with a modest increase in plasma concentration and effect, but the large between subject variability of pharmacokinetic and pharmacodynamic concentration changes suggests it will have little impact on an individual patient, especially when used with adverse effect monitoring. It has been proposed that drugs that have no or only a small metabolic pathway involving the CYP 3A enzyme be used during anesthesia, for example, propofol, atracurium, remifentanil, and the volatile agents. That anesthesia approach denies children of drugs with considerable value. It is better that the inhibitory changes in clearance of these drugs are understood so that rational drug choices can be made to tailor drug use to the individual patient. Altered drug dose, anticipation of duration of effect, timing of administration, use of reversal agents and perioperative monitoring would better behoove children undergoing anesthesia.

Efficacy and safety of remifentanil for endoscopic ultrasound-guided tissue acquisition: a single center retrospective study

BACKGROUND

Remifentanil is a rapid onset and rapid recovery opioid. The combination of remifentanil and propofol for deep sedation decreases the incidents of movement, cough, and hiccup. We evaluated the efficacy and safety of remifentanil during endoscopic ultrasound-guided tissue acquisition.

METHODS

We retrospectively reviewed patients in whom endoscopic ultrasound-guided tissue acquisition was performed for solid mass lesions of the upper gastrointestinal tract and adjacent organs. All patients were premedicated with midazolam (2 mg), and target-controlled infusion of propofol, opioid, and Bispectral Index (BIS) monitoring were administered as necessary to maintain moderate-to-deep sedation. The opioids used were a bolus of alfentanil or remifentanil infusion. The discharge time, consumption of propofol and opioid, adverse events, diagnostic accuracy, and sensitivity and specificity for malignancy, were compared.

RESULTS

Tissue acquisition was achieved in 123 patients (alfentanil group, n = 64; remifentanil group, n = 59). The discharge time of the remifentanil group (16.5 ± 3.2 min) was significantly shorter than that of the alfentanil group (19.0 ± 4.9 min, P = 0.001). The consumption of propofol, adverse events, diagnostic accuracy, sensitivity, and specificity for malignancy in the alfentanil group were not significantly different from those in the remifentanil group.

CONCLUSIONS

Use of alfentanil or remifentanil for target-controlled infusion of propofol-BIS monitoring can provide good sedative and diagnostic quality for endoscopic ultrasound-guided tissue acquisition. However, remifentanil resulted in faster recovery than alfentanil.

A Case of Decreased Amplitude in Motor Evoked Potentials Under Remimazolam Anesthesia

Remimazolam is a newly developed benzodiazepine derivative. Although one case report on the use of remimazolam for motor evoked potential (MEP) monitoring has been reported, there has been no report of changes in the MEP response under remimazolam anesthesia, which is associated with impairment of the corticospinal motor track. This is a case of a 54-year-old woman who was diagnosed with an extradural extramedullary tumor. The patient reported being allergic to chicken eggs. We used remimazolam instead of propofol for anesthesia management. During tumor resection, the amplitudes of MEP responses at the left quadriceps femoris, left tibialis anterior, and left abductor hallucis muscle decreased. The surgery was scaled down and the tumor was removed in a reduced size. The patient had muscle weakness immediately after surgery but eventually recovered. In this case, we could detect changes in MEP response under remimazolam anesthesia, which suggested impairment of the motor tracts during surgery.

A population pharmacokinetic model of remimazolam for general anesthesia and consideration of remimazolam dose in clinical practice

BACKGROUND

Remimazolam besylate is a novel short-acting benzodiazepine. An appropriate pharmacokinetic model of remimazolam is desirable in anesthesia practice. The aim of the study was to develop a pharmacokinetic model using plasma samples from patients anesthetized with remimazolam. Influence of patient characteristics, context-sensitive decrement-times, and dose regimens were also examined.

METHODS

Data were obtained from four trials on patients, and seven trials on healthy volunteers. The characteristics of 416 male and 246 female subjects were as follows: age, 18-93 years; body weight, 34-149 kg; and American Society of Anesthesiologists physical status (ASA-PS), I-IV. 2231 arterial and 3200 venous samples were used for the final model. The equilibration rate constant between arterial plasma and effect-site was estimated using the concept of time to peak effect. The final model was used to generate context-sensitive decrement times and dose regimens for general anesthesia.

RESULTS

A three-compartment model plus virtual venous compartment with allometric scaling of adjusted body weight (ABW), age, sex, and ASA-PS as covariates were selected as the final model. Elimination clearance was lower in males, and in subjects with higher ABW and ASA-PS scores. Approximately 10% or 20% higher dose rate was necessary in females than in males or ASA-PS I/II than III/IV patient. The context-sensitive half-time for effect-site concentration in a 55-year-old, 70-kg, 170-cm male or female ASA-PS I/II patient after > 6-h infusion was 16.7 or 15.9 min.

CONCLUSION

Remimazolam pharmacokinetic model for general anesthesia was successfully developed. ABW, ASA-PS, and sex has a considerable impact on the remimazolam concentration.

Effectiveness of Patient-Controlled Intravenous Analgesia (PCIA) with Sufentanil Background Infusion for Post-Cesarean Analgesia: A Randomized Controlled Trial

Purpose

To investigate the effectiveness of sufentanil patient-controlled intravenous analgesia pump (PCIA) and background infusion in patients of post-cesarean analgesia.

Patients and Methods

This trial compared two groups of women undergoing cesarean section and receiving PCIA: no background infusion group (n=30), 6-min lockout time, and background infusion group (n=30), 2 mL/h infusion, 10-min lockout time. Both groups with 2 μg/kg sufentanil was diluted to 100 mL with normal saline. VAS scores at rest at 36 h was the primary endpoint. The secondary endpoints were the VAS scores at rest at 6, 12, and 24 h, the total amount of sufentanil consumed, the Ramsay sedation score (RSS) assessed at the same time points, postpartum bleeding within 24 h, the injection/attempt (I/A) ratio, BP and HR, PONV, side effects of sufentanil.

Results

Compared with the no background infusion group, the background infusion group showed lower VAS pain scores at 6, 12, and 24 h (P<0.01), but no differences at 36 h (95% CI = -0.5-0.8. P>0.05). Attempts, injections, and total sufentanil consumption were significantly different between the two groups (P<0.001), but without difference in I/A. Bleeding was less in the background infusion group at 1 h (P=0.03). The minimal respiration rates were not significantly different between groups.

Conclusion

Background infusion increased the total consumption of sufentanil within 36 h after cesarean section. Although it did not reduce uterine contraction pain and wound pain at 36 h, it significantly reduced the pain at 6, 12, and 24 h after cesarean section. It improved patient satisfaction and reduced the amount of bleeding after 1 h. Importantly, it did not increase the incidence of hypertension, PONV and respiratory depression.

Effect of high‐flow nasal oxygen on postoperative oxygenation in obese patients: A randomized controlled trial

Background and Aim

Postoperative hypoxemia is common after general anesthesia in obese patients. We investigated if early application of high‐flow nasal oxygen (HFNO) improved postoperative oxygenation in obese patients compared with standard oxygen therapy following general anesthesia for laparoscopic bariatric surgery.

Methods

This was an open labeled randomized controlled trial conducted at a university hospital in Sweden between October 23, 2018 and February 11, 2020. The study was performed as a substudy within a previously published trial. After ethics committee approval and written informed consent, 40 obese patients (body mass index [BMI] ≥ 35 kg m⁻²) scheduled for laparoscopic bariatric surgery were randomized to receive oxygen using a standard low‐flow nasal cannula (NC group) or HFNO at 40 L min⁻¹ (HF group) immediately upon arrival to the post‐anesthesia care unit. Flow rate (NC group) or FiO₂ (HF group) was titrated to reach an initial SpO₂ of 95%–98% after which settings were left unchanged. The primary outcome was PaO₂ at 60 min following postoperative baseline values. Secondary outcomes included PaCO₂, SpO₂, hemodynamic variables, and patient self‐assessed discomfort.

Results

Thirty‐four patients were available for analysis. PaO₂ was similar between groups at postoperative baseline. After 60 min, PaO₂ had increased to 12.6 ± 2.8 kPa in the NC group (n = 15) and 14.0 ± 2.7 kPa in the HF group (n = 19); (mean difference 1.4 kPa, 95% confidence interval −0.6 to 3.3; p = 0.16). There were no differences in PaCO₂, hemodynamic variables, or self‐assessed discomfort between groups after 60 min.

Conclusion

In obese patients, HFNO did not improve postoperative short‐term oxygenation compared with standard low‐flow oxygen following general anesthesia for laparoscopic bariatric surgery.

Propofol context-sensitive decrement times in children

Plasma drug concentration is the variable linking dose to effect. The decrement time required for plasma concentration of anesthetic agents to decrease by 50% (context-sensitive half-time) correlates with the time taken to regain consciousness. However, the decrement time to consciousness may not be 50%. An effect compartment concentration is associated more closely with return of consciousness than plasma concentration. An alternative decrement time, the time required for propofol to decrease to a predetermined effect compartment concentration associated with movement (eg, 2 µg.ml^-1 ), was used to simulate time for the concentration to decrease from steady state at a typical targeted effect compartment concentration 3.5 µg.ml^-1 in children. These times were short and reflected a decrement time to consciousness (CST_AWAKE ) increase that was small with longer infusion time. CST_AWAKE ranged from 7.5 min in 1-year-old infant given propofol for 15 min to 13.5 min in a 15-year-old adolescent given a 2-hour infusion. Changes in decrement time with age reflect maturation of drug clearance. Neonates had prolonged increment times, 10 min after 15 min infusion and 18 min after 120 min infusion using a target concentration of 3.5 µg.ml^-1 . Decrement times to a targeted arousal concentration are context-sensitive. Use of a higher target concentration of 6 µg.ml^-1 doubled decrement times. Decrement times are associated with variability: delayed recovery beyond these simulated times is likely more attributable to the use of adjuvant drugs or the child's clinical status. An understanding of propofol decrement times can be used to guide recovery after anesthesia.

Differential Effects of Gamma-Aminobutyric Acidergic Sedatives on Risk of Post-Extubation Delirium in the ICU: A Retrospective Cohort Study From a New England Health Care Network

OBJECTIVES

To evaluate whether different gamma-aminobutyric acidergic (GABAergic) sedatives such as propofol and benzodiazepines carry differential risks of post-extubation delirium in the ICU.

DESIGN

Retrospective cohort study.

SETTING

Seven ICUs in an academic hospital network, Beth Israel Deaconess Medical Center (Boston, MA).

PATIENTS

Ten thousand five hundred and one adult patients mechanically ventilated for over 24 hours.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

We tested the hypothesis that benzodiazepine versus propofol-based sedation is associated with fewer delirium-free days within 14 days after extubation. Further, we hypothesized that the measured sedation level evoked by GABAergic drugs is a better predictor of delirium than the drug dose administered. The proportion of GABAergic drug-induced deep sedation was defined as the ratio of days with a mean Richmond Agitation-Sedation Scale of less than or equal to -3 during mechanical ventilation. Multivariable regression and effect modification analyses were used. Delirium-free days were lower in patients who received a high proportion of deep sedation using benzodiazepine compared with propofol-based sedation (adjusted absolute difference, -1.17 d; 95% CI, -0.64 to -1.69; p < 0.001). This differential effect was magnified in elderly patients (age > 65) and in patients with liver or kidney failure (p-for-interaction < 0.001) but not observed in patients who received a low proportion of deep sedation (p = 0.95). GABAergic-induced deep sedation days during mechanical ventilation was a better predictor of post-extubation delirium than the GABAergic daily average effective dose (area under the curve 0.76 vs 0.69; p < 0.001).

CONCLUSIONS

Deep sedation during mechanical ventilation with benzodiazepines compared with propofol is associated with increased risk of post-extubation delirium. Our data do not support the view that benzodiazepine-based compared with propofol-based sedation in the ICU is an independent risk factor of delirium, as long as deep sedation can be avoided in these patients.

A Phase II Cluster-Crossover Randomized Trial of Fentanyl versus Morphine for Analgosedation in Mechanically Ventilated Patients

Rationale: The continuous infusion of fentanyl or morphine is often prescribed to assist with analgesia and sedation (analgosedation) during mechanical ventilation. Objectives: To compare the effect of fentanyl versus morphine on patient-centered outcomes in ventilated patients. Methods: We conducted a cluster-randomized, cluster-crossover trial between July 2019 and August 2020 in two adult ICUs. We compared two continuous infusion regimens (fentanyl versus morphine). One ICU was randomized to the fentanyl-morphine sequence and the other to the morphine-fentanyl sequence. The primary outcome was the number of ventilator-free days at Day 28. Secondary outcomes included, among others, duration of mechanical ventilation in survivors and ICU-free days at Day 28. Measurements and Main Results: Via cluster allocation, we randomized 737 patients. Of these, 56 were excluded because of the opt-out consent process, leaving 681 (344 to fentanyl and 337 to morphine) for primary analysis (median [interquartile range] age, 59 [44-69] years). Median ventilator-free days at Day 28 were 26.1 (20.7-27.3) in the fentanyl versus 25.3 (19.1-27.2) in the morphine group (median difference, 0.79 [95% confidence interval, 0.31 to 1.28], P = 0.001). ICU-free days were greater (P < 0.001) and length of stay in the ICU for survivors shorter (P < 0.001) in the fentanyl group. All other secondary outcomes were not statistically different by treatment group. Conclusions: Among adult patients requiring mechanical ventilation, compared with morphine, fentanyl infusion significantly increased the median number of ventilator-free days at Day 28. The choice of opioid infusion agent may affect clinical outcomes and requires further investigation.

Pharmacokinetic concepts for dexmedetomidine target-controlled infusion pumps in children

Pharmacokinetic parameter estimates are used in mathematical equations (pharmacokinetic models) to describe concentration changes with time in a population and are specific to that population. Simulation using these models and their parameter estimates can enrich understanding of drug behavior and serve as a basis for study design. Pharmacokinetic concepts are presented pertaining to future designs of dexmedetomidine target-controlled infusion pumps in children. This manuscript provides the pediatric anesthesiologist with an understanding of the nuances that should be considered when using target-controlled infusion pumps; how the central volume may differ between populations, how clearance changes with age, and the impact of adverse effects on dose. In addition, the ideal loading dose and rate of delivery to achieve target concentration without adverse cardiovascular effects are reviewed, and finally, dose considerations for obese children, based on contact-sensitive half-time, are introduced. An understanding of context-sensitive half-time changes with age enables anesthetic practitioners to better estimate duration of effect after cessation of dexmedetomidine infusion. Use of these known pharmacokinetic parameters and covariate information for the pediatric patient could readily be incorporated into commercial target-controlled infusion pumps to allow effective and safe open-loop administration of dexmedetomidine in children.

Influence of doxapram and intermittent 10% carbon dioxide inspiration on cardiovascular and laryngeal functions in anesthetized dogs

OBJECTIVE

To compare the effects of two doses of doxapram intravenous injection and carbon dioxide inhalation on the cardiovascular and laryngeal functions of anesthetized hounds.

STUDY DESIGN

Experimental study.

ANIMALS

Six healthy adult dogs.

METHODS

In a Latin-square design, the mean arterial blood pressure (MABP) and heart rate (HR) were recorded continuously. The inspiratory normalized glottic gap areas (iNGGA) were measured before and after each stimulation with 0.55 mg/kg of doxapram (L-DOX), 2.2 mg/kg of doxapram (H-DOX), or 90 s of inhalation of 10% carbon dioxide in oxygen (I-CO₂ ). The stimulations were tested in duplicate or triplicate. Video clips of the laryngeal movement were scored by board-certified surgeons masked to the treatment.

RESULTS

The MABP increased with L-DOX and H-DOX up to 81% (both p < .001 compared to I-CO₂ ), and persisted during the other stimulations (both p < .001). An intermittent tachycardic effect of up to 79% increase in HR was observed with doxapram. The HR following H-DOX was higher than L-DOX and I-CO₂ (both p < .016). Neither hypertension nor tachycardia was observed with I-CO₂ . The iNGGA increased with all treatments (p < .001). The iNGGA was greater with H-DOX than L-DOX and I-CO₂ (both p < .007). All treatments received higher scores (all p < .001) with acceptable inter- and intra-observers Krippendorff's alphas.

CONCLUSION

All treatments were effective respiratory stimulants in anesthetized dogs; however, doxapram caused hypertension and tachycardia.

CLINICAL SIGNIFICANCE

Carbon dioxide inhalation might improve arytenoid motion without cardiovascular effects in dogs during clinical airway examinations.

Fentanyl versus Remifentanil for Cough Suppression and Recovery after Video-Assisted Thoracic Surgery

Background

Various methods have been used to reduce postoperative pain after thoracic surgery. However, these methods may affect the patient's respiratory response and delay recovery from anesthesia. We aimed to evaluate the effects of fentanyl and remifentanil during extubation after video-assisted thoracic surgery (VATS).

Methods

This study included 45 randomly-selected male patients who underwent VATS for pneumothorax between July 2011 and August 2012. We divided the participants into 3 groups: the F group, which received a bolus injection of 1.0 μg/kg of fentanyl; the R1 group, which received a 0.04 μg/kg/min remifentanil infusion; and the R2 group, which received a 0.08 μg/kg/min remifentanil infusion. Hemodynamics, pain, cough, consciousness level, and nausea were assessed for each group.

Results

The number and severity of coughs were lower in the R1 and R2 groups than in the F group, and there were no differences between the R1 and R2 groups. Respiratory depression and loss of consciousness were not observed in any of the patients, and there were no differences in hemodynamics.

Conclusion

In comparison with fentanyl, remifentanil did not result in a wide fluctuation of blood pressure and heart rate upon emergence from general anesthesia. Moreover, remifentanil contributed to cough suppression and postoperative pain control. Remifentanil seems to be a safe and effective analgesic after VATS.

Association of Sedation, Coma, and In-Hospital Mortality in Mechanically Ventilated Patients With Coronavirus Disease 2019-Related Acute Respiratory Distress Syndrome: A Retrospective Cohort Study

OBJECTIVES

In patients with coronavirus disease 2019-associated acute respiratory distress syndrome, sedatives and opioids are commonly administered which may lead to increased vulnerability to neurologic dysfunction. We tested the hypothesis that patients with coronavirus disease 2019-associated acute respiratory distress syndrome are at higher risk of in-hospital mortality due to prolonged coma compared with other patients with acute respiratory distress syndrome matched for disease severity.

DESIGN

Propensity-matched cohort study.

SETTING

Seven ICUs in an academic hospital network, Beth Israel Deaconess Medical Center (Boston, MA).

PATIENTS

All mechanically ventilated coronavirus disease 2019 patients between March and May 2020 were identified and matched with patients with acute respiratory distress syndrome of other etiology.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Using clinical data obtained from a hospital registry, we matched 114 coronavirus disease 2019 patients to 228 noncoronavirus disease 2019-related acute respiratory distress syndrome patients based on baseline disease severity. Coma was identified using the Richmond Agitation Sedation Scale less than or equal to -3. Multivariable logistic regression and mediation analyses were used to assess the percentage of comatose days, sedative medications used, and the association between coronavirus disease 2019 and in-hospital mortality. In-hospital mortality (48.3% vs 31.6%, adjusted odds ratio, 2.15; 95% CI, 1.34-3.44; p = 0.002), the percentage of comatose days (66.0% ± 31.3% vs 36.0% ± 36.9%, adjusted difference, 29.35; 95% CI, 21.45-37.24; p < 0.001), and the hypnotic agent dose (51.3% vs 17.1% of maximum hypnotic agent dose given in the cohort; p < 0.001) were higher among patients with coronavirus disease 2019. Brain imaging did not show a higher frequency of structural brain lesions in patients with coronavirus disease 2019 (6.1% vs 7.0%; p = 0.76). Hypnotic agent dose was associated with coma (adjusted coefficient, 0.61; 95% CI, 0.45-0.78; p < 0.001) and mediated (p = 0.001) coma. Coma was associated with in-hospital mortality (adjusted odds ratio, 5.84; 95% CI, 3.58-9.58; p < 0.001) and mediated 59% of in-hospital mortality (p < 0.001).

CONCLUSIONS

Compared with matched patients with acute respiratory distress syndrome of other etiology, patients with coronavirus disease 2019 received higher doses of hypnotics, which was associated with prolonged coma and higher mortality.

Challenges in Sedation Management in Critically Ill Patients with COVID-19: a Brief Review

Purpose of Review

To highlight the challenges associated with providing sedation and analgesia to critically ill patients with coronavirus disease 2019 (COVID-19) and also understand the pathophysiological alterations induced by the disease process as well as the logistical difficulties encountered by providers caring for these patients. We also discuss the rationale and risks associated with the use of common sedative agents specifically within the context of COVID-19 and provide evidence-based management strategies to help manage sedation and analgesia in such patients.

Recent Findings

A significant proportion of patients with COVID-19 require intensive care and mechanical ventilation, thus requiring sedation and analgesia. These patients tend to require higher doses of sedative medications and often for long periods of time. Most of the commonly used sedative and analgesic agents carry unique risks that should be considered within the context of the unique pathophysiology of COVID-19, the logistical issues the disease poses, and the ongoing drug shortages.

Summary

With little attention being paid to sedation practices specific to patients with COVID-19 in critical care literature and minimal mention in national guidelines, there is a significant gap in knowledge. We review the existing literature to discuss the unique challenges that providers face while providing sedation and analgesia to critically ill patients with COVID-19 and propose evidence-based management strategies.

JM-1232(-) and propofol, a new combination of hypnotics with short-acting and non-cumulative preferable properties

Drug interactions are significant in anesthesiology because drug combinations can potentially possess novel properties. The pharmacological advantages of a new combination of the benzodiazepine receptor agonist JM-1232(-) and propofol were investigated in mice. Male adult mice were administered JM-1232(-) or propofol or combinations of the two drugs intravenously. Loss of the righting reflex was evaluated as achieving hypnosis, and the time until recovery of the reflex was measured as hypnosis time. After determining the ED50, doses double and triple the ED50 of propofol were injected with JM-1232(-) to compare hypnosis time. The injections were repeated four times, and the hypnosis times were compared. Flumazenil was administered separately immediately after the last dose was injected. The ED50 values ([95% confidence interval]) for hypnosis were 3.76 [3.36-4.10] for JM-1232(-) and 9.88 [8.03-11.58] mg kg-1 for propofol. Co-administration of 0.5 and 1 mg kg-1 JM-1232(-) reduced the ED50 values of propofol to 1.76 [1.21-2.51] and 1.00 [0.46-1.86] mg kg-1, respectively. The drug combination for hypnosis produced a supra-additive interaction. Hypnosis time was significantly shorter in the groups given the mixtures compared to each hypnotic administered alone. After repeated injections, hypnosis time with the mixtures showed smaller prolongation than that with the hypnotic alone. Flumazenil completely restored the recovery time after anesthesia. The combination of JM-1232(-) and propofol showed a supra-additive interaction, and the reduced hypnotic dose contributed to a faster recovery even after multiple injections.

Pharmacokinetics of Morphine and Morphine-6-Glucuronide During Postoperative Pain Therapy in Cardiac Surgery Patients

BACKGROUND AND OBJECTIVE

Morphine is a standard analgesic drug for postoperative pain therapy. This study aimed to evaluate the pharmacokinetics of morphine and its active metabolite morphine-6-glucuronide (M6G) in cardiac surgery  patients during postoperative analgesia.

METHODS

Twenty-five adult patients undergoing cardiac surgery received postoperative pain therapy by patient-controlled analgesia with intravenous bolus doses of morphine. Plasma concentrations of morphine and M6G were determined from arterial samples. Population pharmacokinetic parameters were estimated using nonlinear mixed-effects modeling.

RESULTS

Data from twenty-one patients (aged 44-79 years) were analyzed. Pharmacokinetics were best described by a three-compartment model for morphine and a two-compartment model for M6G, linked by a transit compartment. Mean (±SD) population estimates for morphine were: clearance (CL) = 1.35±0.40 L/min, central volume of distribution (V₁) = 8.1±2.2 L, steady-state volume of distribution (V_ss) = 207±83 L, terminal elimination half-life (T_1/2γ) = 177±50 min. Clearance of morphine was proportional to cardiac output. Mean (±SD) population estimates for M6G were: CL = 0.098±0.037 L/min, V₁ = 5.5±0.8 L, V_ss = 15.8±0.8 L, T_1/2β = 227±74 min. The time to peak concentration of M6G after a bolus dose of morphine was 53±20 min. Clearance of M6G was proportional to estimated glomerular filtration rate.

CONCLUSIONS

The pharmacokinetics of morphine and M6G in pain therapy of cardiac surgery  patients could be well described by standard compartmental models. Cardiac output was identified as a significant covariate for morphine clearance, whereas renal function was identified as the most significant covariate for clearance of M6G. These effects should be particularly considered if morphine is administered as a continuous infusion. The developed pharmacokinetic model also enables patient-controlled target-controlled infusion for pain therapy with morphine.

TRIAL REGISTRATION

Clinical Trials NCT02483221 (June 26, 2015).

The influence of cardiac output on propofol and fentanyl pharmacokinetics and pharmacodynamics in patients undergoing abdominal aortic surgery

Cardiac output (CO) is expected to affect elimination and distribution of highly extracted and perfusion rate-limited drugs. This work was undertaken to quantify the effect of CO measured by the pulse pressure method on pharmacokinetics and pharmacodynamics of propofol and fentanyl administrated during total intravenous anesthesia (TIVA). The data were obtained from 22 ASA III patients undergoing abdominal aortic surgery. Propofol was administered via target-controlled infusion system (Diprifusor) and fentanyl was administered at a dose of 2-3 µg/kg each time analgesia appeared to be inadequate. Hemodynamic measurements as well as bispectral index were monitored and recorded throughout the surgery. Data analysis was performed by using a non-linear mixed-effect population modeling (NONMEM 7.4 software). Three compartment models that incorporated blood flows as parameters were used to describe propofol and fentanyl pharmacokinetics. The delay of the anesthetic effect, with respect to plasma concentrations, was described using a biophase (effect) compartment. The bispectral index was linked to the propofol and fentanyl effect site concentrations through a synergistic Emax model. An empirical linear model was used to describe CO changes observed during the surgery. Cardiac output was identified as an important predictor of propofol and fentanyl pharmacokinetics. Consequently, it affected the depth of anesthesia and the recovery time after propofol-fentanyl TIVA infusion cessation. The model predicted (not observed) CO values correlated best with measured responses. Patients' age was identified as a covariate affecting the rate of CO changes during the anesthesia leading to age-related difference in individual patient's responses to both drugs.

Explaining anaesthetic hysteresis with effect-site equilibration

BACKGROUND

Anaesthetic induction occurs at higher plasma drug concentrations than emergence in animal studies. Some studies find evidence for such anaesthetic hysteresis in humans, whereas others do not. Traditional thinking attributes hysteresis to drug equilibration between plasma and the effect site. Indeed, a key difference between human studies showing anaesthetic hysteresis and those that do not is in how effect-site equilibration was modelled. However, the effect-site is a theoretical compartment in which drug concentration cannot be measured experimentally. Thus, it is not clear whether drug equilibration models with experimentally intractable compartments are sufficiently constrained to unequivocally establish evidence for the presence or absence of anaesthetic hysteresis.

METHODS

We constructed several models. One lacked hysteresis beyond effect-site equilibration. In another, neuronal dynamics contributed to hysteresis. We attempted to distinguish between these two systems using drug equilibration models.

RESULTS

Our modelling studies showed that one can always construct an effect-site equilibration model such that hysteresis collapses. So long as the concentration in the effect-site cannot be measured directly, the correct effect-site equilibration model and the one that erroneously collapses hysteresis are experimentally indistinguishable. We also found that hysteresis can naturally arise even in a simple network of neurones independently of drug equilibration.

CONCLUSIONS

Effect-site equilibration models can readily collapse hysteresis. However, this does not imply that hysteresis is solely attributable to the kinetics of drug equilibration.

Sublingual Sufentanil Tablet System Versus Continuous Morphine Infusion for Postoperative Analgesia in Cardiac Surgery Patients

OBJECTIVE(S)

To assess the effectiveness and side effects of a patient-controlled sublingual sufentanil tablet system for postoperative analgesia after cardiac surgery and to compare it to a nurse-controlled continuous morphine infusion.

DESIGN

Prospective, open-label, randomized controlled trial.

SETTING

Single university academic center.

PARTICIPANTS

Adult patients undergoing cardiac surgery, which included a sternotomy.

INTERVENTIONS

Sublingual sufentanil tablet system versus nurse-controlled continuous morphine infusion.

MEASUREMENTS AND MAIN RESULTS

A total of 483 cardiac surgery patients were screened for eligibility, of whom 64 patients completed the study. No statistically significant differences were found for baseline characteristics between both groups. All mean numeric rating scale (NRS) pain scores from after extubation until intensive care unit discharge were ≤3 in both groups. The cumulative mean NRS pain score from 24 hours after extubation (primary outcome) (t = hours after extubation) was significantly different in favor of the morphine group: (t = 0-24) (0.8 [0.7] v 1.3 [0.8]; p = 0.006). Later cumulative mean pain scores were also in favor of the morphine group: (t = 24-48) (0.2 [0.3] v 0.6 [0.5]; p = 0.001) and (t = 48-63) (0.0 [0.0] v 0.1 [0.2]; p = 0.013). The cumulative opioid dose (in milligrams intravenous morphine equivalents) was significantly higher in the morphine group compared with the sublingual sufentanil group (241.94 [218.73] v 39.84 [21.96]; p = 0.0001). No differences were found for the incidences of postoperative nausea and vomiting, sedation, hypoventilation, bradycardia, or hypotension between both groups (secondary outcomes).

CONCLUSIONS

Despite resulting in statistically significantly higher pain scores, a patient-controlled sublingual sufentanil tablet system offers adequate analgesia after cardiac surgery and reduces opioid consumption when compared with continuous morphine infusion.

Estimation of Attainment of Steady-State Conditions for Compounds With a Long Half-Life

Half-life is a standard result reported with analysis of pharmacokinetic data. Different definitions such as noncompartmental half-life, terminal half-life, effective half-life, and context-sensitive half-life can yield substantially different estimates of the quantity "half-life." Time to attainment of steady-state conditions is generally derived from (terminal) half-life and therefore sensitive toward the definition of half-life. Thus, estimates of the time to attain steady state must be provided with a precise definition of steady state and the method used for estimation, particularly for drugs with long (terminal) half-life. For clinical purposes, terminal half-life can have limited relevance if drug concentrations in the terminal elimination phase are low. A general rule for which half-life to use is infeasible. While limited accumulation can be negligible if a plateau in pharmacokinetics/pharmacodynamics is reached or with a wide therapeutic window (ie, exposure range), small additional drug accumulation can be highly relevant for drugs with a narrow therapeutic window. Beyond the average, estimation of individual time to attainment of steady state can add highly relevant information about the variability between subjects. Simulations from population models and the use of different definitions of steady state provide an assessment of robustness of the results. The relevance of accurate estimation of time to attainment of steady state is illustrated with cenerimod, an sphingosine-1-phosphate 1 receptor modulator with long half-life currently in clinical development for which estimates of time to steady state ranged from 35 to 110 days with different calculations.

Pharmacokinetics and Pharmacodynamics of Remimazolam (CNS 7056) after Continuous Infusion in Healthy Male Volunteers: Part I. Pharmacokinetics and Clinical Pharmacodynamics

BACKGROUND

Remimazolam (CNS 7056) is a new ultra-short-acting benzodiazepine for intravenous sedation and anesthesia. Its pharmacokinetics and pharmacodynamics have been reported for bolus administration. This study aimed to investigate the pharmacokinetics and pharmacodynamics of remimazolam after continuous infusion.

METHODS

Twenty healthy male volunteers (20 to 38 yr, 64 to 99 kg) received remimazolam as continuous intravenous infusion of 5 mg/min for 5 min, 3 mg/min for the next 15 min, and 1 mg/min for further 15 min. Pharmacokinetics of remimazolam and its metabolite were determined from arterial plasma concentrations. Sedation was assessed using the Modified Observer's Assessment of Alertness and Sedation scale. Pharmacokinetic-pharmacodynamic modeling was performed by population analysis. Hemodynamics and the electrocardiogram were also investigated.

RESULTS

Pharmacokinetics was best described by a three-compartment model for remimazolam and a two-compartment model with transit compartment for the metabolite. Remimazolam showed a high clearance (1.15 ± 0.12 l/min, mean ± SD), a small steady-state volume of distribution (35.4 ± 4.2 l) and a short terminal half-life (70 ± 10 min). The simulated context-sensitive halftime after an infusion of 4 h was 6.8 ± 2.4 min. Loss of consciousness was observed 5 ± 1 min after start, and full alertness was regained 19 ± 7 min after stop of infusion. Pharmacodynamics of Modified Observer's Assessment of Alertness and Sedation score was best described by a sigmoid probability model with effect site compartment. The half-maximum effect site concentration for a Modified Observer's Assessment of Alertness and Sedation score less than or equal to 1 was 695 ± 239 ng/ml. The equilibration half-time between central and effect compartment was 2.7 ± 0.6 min. Mean arterial blood pressure decreased by 24 ± 6%, and heart rate increased by 28 ± 15%. Spontaneous breathing was maintained throughout the study. There was no significant prolongation of the QT interval of the electrocardiogram observed.

CONCLUSIONS

Remimazolam was characterized by a pharmacokinetic-pharmacodynamic profile with fast onset, fast recovery, and moderate hemodynamic side effects.

Pharmacokinetics and Pharmacodynamics of Remimazolam (CNS 7056) after Continuous Infusion in Healthy Male Volunteers: Part II. Pharmacodynamics of Electroencephalogram Effects

BACKGROUND

Remimazolam (CNS 7056) is a new ultra-short acting benzodiazepine for IV sedation. This study aimed to investigate the electroencephalogram (EEG) pharmacodynamics of remimazolam infusion.

METHODS

Twenty healthy male volunteers received remimazolam as continuous IV infusion of 5 mg/min for 5 min, 3 mg/min for the next 15 min, and 1 mg/min for further 15 min. Continuous EEG monitoring was performed by a neurophysiologic system with electrodes placed at F3, F4, C3, C4, O1, O2, Cz, and Fp1 (10/20 system) and using the Narcotrend Index. Sedation was assessed clinically by using the Modified Observer's Assessment of Alertness and Sedation scale. Pharmacodynamic models were developed for selected EEG variables and Narcotrend Index.

RESULTS

EEG changes during remimazolam infusion were characterized by an initial increase in beta frequency band and a late increase in delta frequency band. The EEG beta ratio showed a prediction probability of Modified Observer's Assessment of Alertness and Sedation score of 0.79, and could be modeled successfully using a standard sigmoid Emax model. Narcotrend Index showed a prediction probability of Modified Observer's Assessment of Alertness and Sedation score of 0.74. The time course of Narcotrend Index was described by an extended sigmoid Emax model with two sigmoid terms and different plasma-effect equilibration times.

CONCLUSIONS

Beta ratio was identified as a suitable EEG variable for monitoring remimazolam sedation. Narcotrend Index appeared less suitable than the beta ratio for monitoring the sedative effect if remimazolam is administered alone.

Propofol Modulates Early Memory Consolidation in Humans

Maintenance of memory across time is crucial for adaptive behavior. Current theories posit that the underlying consolidation process depends on stabilization of synapses and reorganization of interactions between hippocampus and neocortex. However, the temporal properties of hippocampal-neocortical network reconfiguration during consolidation are still a matter of debate. Translational research on this issue is challenged by the paucity of techniques to transiently interfere with memory in the healthy human brain. Here, we report a neuro-pharmacological approach with the GABA_Aergic anesthetic propofol and a memory task sensitive to hippocampal dysfunction. Patients undergoing minor surgery learned word lists before injection of an anesthetic dose of propofol. Results show that administration of the drug shortly after learning (∼13 min) impairs recall after awakening but spares recognition. By contrast, later administration (∼105 min) has no effect. These findings suggest significant changes in memory networks very early after learning that are decisive for later recall. Propofol general anesthesia provides an experimental tool to modulate the first steps of hippocampus-mediated memory consolidation in humans.

Pharmacokinetics, Pharmacodynamics, and Safety of the Dual Orexin Receptor Antagonist Lemborexant: Findings From Single-Dose and Multiple-Ascending-Dose Phase 1 Studies in Healthy Adults

Lemborexant, a dual orexin receptor antagonist, is approved for the treatment of insomnia and is under investigation for treating other sleep disorders. Here we summarize pharmacokinetic, pharmacodynamic, and safety data from 3 randomized, double‐blind, placebo‐controlled phase 1 studies: single ascending doses in healthy adults (Study 001; 1‐200 mg; N = 64), multiple ascending doses in healthy and elderly adults (Study 002; 2.5‐75 mg; N = 55), and multiple doses in healthy white and Japanese adults (Study 003; 2.5‐25 mg; N = 32). Lemborexant exposure increased with increasing dose. The time to maximum concentration ranged from approximately 1 to 3 hours for the 5‐ and 10‐mg doses. The mean effective half‐life was 17 hours for lemborexant 5 mg and 19 hours for lemborexant 10 mg. The plasma concentration at 9 hours postdose was 27% of the maximum concentration following multiple dosing with lemborexant 10 mg. There were no clinically relevant effects on next‐morning residual sleepiness (Karolinska Sleepiness Scale, Digital Symbol Substitution Test, Psychomotor Vigilance Test) for doses through 10 mg/day, indicating no effect of residual plasma concentrations on next‐day residual effects. Lemborexant was well tolerated across the doses tested. There were no clinically relevant effects of age, sex, or race on lemborexant pharmacokinetics, pharmacodynamics, or safety. These results suggest that lemborexant at doses through 25 mg provides an overall pharmacokinetic, pharmacodynamic, and safety profile suitable for obtaining the target pharmacologic effect supporting treatment of insomnia while minimizing residual effects during wake time.

Iatrogenic Opioid Withdrawal Syndrome in Critically Ill Patients: a Retrospective Cohort Study

BACKGROUND

Opioid withdrawal syndrome (OWS) may occur following the reduction or discontinuation of opioid analgesics. In critically ill pediatric patients, OWS is a common and clinically significant condition. However, OWS in adult patients has not been assessed in detail. Therefore, we aimed to investigate the incidence, risk factors, and clinical features of OWS in mechanically ventilated patients treated in an adult intensive care unit (ICU).

METHODS

This study was a retrospective evaluation of data from patients treated in the medical ICU for > 3 days and who received only one type of opioid analgesic. OWS was assessed over a 24 hours period from discontinuation or reduction (by > 50%) of continuous opioid infusion. OWS was defined as the presence of ≥ 3 central nervous system or autonomic nervous system symptoms.

RESULTS

In 126 patients treated with remifentanil (n = 58), fentanyl (n = 47), or morphine (n = 21), OWS was seen in 31.0%, 36.2%, and 9.5% of patients, respectively (P = 0.078). The most common symptom was a change in respiratory rate (remifentanil, 94.4%; fentanyl, 76.5%; morphine, 100%). Multivariate Cox-proportional hazards model showed that OWS was negatively associated with morphine treatment (hazard ratio [HR], 0.17; 95% confidence interval [CI], 0.037-0.743) and duration of opioid infusion (HR, 0.566; 95% CI, 0.451-0.712).

CONCLUSION

OWS is not uncommon in mechanically ventilated adult patients who received continuous infusion of opioids for > 3 days. The use of morphine may be associated with a decreased risk of OWS.

Non-traditional administration of remifentanil in an experimental setting

Remifentanil is ultrashort-acting opioid with a unique pharmacokinetic profile. It is used exclusively intravenously. While considering its rapid onset of action and other pharmacokinetic properties, we decided to assess its effects following administration via non-traditional routes. Rabbits (n=10 per each group) were randomized into six groups: remifentanil 1 microg/kg and 3 microg/kg IM, 5.0 and 10.0 microg/kg conjunctivally, and 10 microg/kg and 25.0 microg/kg intranasally. Sedating effects were assessed via a loss of the righting reflex. Secondary, mean arterial blood pressure, arterial oxygen saturation of hemoglobin, and pulse rate was monitored in all rabbits. Non-traditional routes of administration were shown to provide a rapid onset of action as well as fast recovery. Importantly, the administration of remifentanil did not result in any deterioration of cardiovascular functions.

Comparison of the Analgesic Effect of Sufentanil versus Fentanyl in Intravenous Patient-Controlled Analgesia after Total Laparoscopic Hysterectomy: A Randomized, Double-blind, Prospective Study

Background: Fentanyl is one of the most widely used opioids for intravenous patient-controlled analgesia (IV-PCA). Sufentanil, a fentanyl analog, is suitable for postoperative pain control because it has no active metabolites and shows a higher therapeutic index and lower frequency of respiratory suppression than fentanyl. This study aimed to compare the two opioids for postoperative pain relief on the basis of analgesic efficacy, adverse effects, and patient satisfaction. Methods: Sixty-four patients undergoing total laparoscopic hysterectomy were randomly allocated into a fentanyl group (n = 31) or a sufentanil group (n = 33). The patients received 50-μg fentanyl or 10-μg sufentanil before induction of anesthesia and 5 minutes after uterine incision during surgery in the fentanyl and sufentanil group, respectively. After arriving at the post-anesthesia care unit (PACU), verbal pain score (VPS) and sedation score were assessed. IV-PCA (fentanyl 1250 μg or sufentanil 250 μg with ondansetron 8 mg; total volume, 60 ml) was connected and continued for 48 h postoperatively. Postoperative pain was evaluated by using the numeric rating scale (NRS; at rest/during cough) at 6, 12, 24, 36, and 48 hours after surgery. The cumulative PCA consumption, patient satisfaction scores, and adverse effects were measured. Results: In the PACU, VPS was significantly higher and rescue fentanyl consumption was higher in the fentanyl group than in the sufentanil group, while the sedation score and adverse effects were comparable between the groups. No significant differences were observed in the NRS scores for pain (at rest/during cough) in the ward over 48 hours postoperatively, but the cumulative PCA consumption was significantly higher in the fentanyl group (47.4 ± 9.9 ml vs. 36.2 ± 14.6 ml, P = 0.01). There were no significant intergroup differences in patient satisfaction score and the incidence of adverse effects in the ward, except for a higher incidence of dry mouth in the fentanyl group. Conclusions: In comparison with fentanyl, sufentanil showed comparable analgesic efficacy and safety with less analgesic consumption (under a potency ratio of 1:5) in IV-PCA after total laparoscopic hysterectomy. Therefore, we suggest that sufentanil can be a useful alternative to fentanyl for IV-PCA.

Monitored Anesthesia Care for Cardiovascular Interventions

The interventional cardiology is growing and evolving. Many complex procedures are now performed outside the operating room to manage cardiovascular pathologies which had been traditionally treated with cardiac surgery. Appropriate sedation strategy is crucial for improved patient comfort and successful procedure while ensuring safety. Sedation for cardiovascular intervention is frequently challenging, especially in critically-ill, high-risk patients. This review addresses pre-procedure evaluation and preparation of patients, proper monitoring, commonly used sedatives and analgesics, and considerations for specific procedures. Appropriate depth of sedation and analgesia should be balanced with patient, procedural and institutional factors. Understanding of the pharmacology of sedatives/analgesics, vigilant monitoring, ability and proper preparation for management of potential complications may improve outcomes in patients undergoing sedation for cardiovascular procedures.

[Sufentanil during anesthetic induction of remifentanil-based total intravenous anesthesia: a randomized controlled trial]

BACKGROUND

Postoperative pain represents an important concern when remifentanil is used for total intravenous anesthesia because of its ultrashort half-life. Longer acting opioids, such as sufentanil, have been used during induction of remifentanil-based total intravenous anesthesia as a means to overcome this shortcoming. However, the effectiveness and safety of such strategy still lacks evidence from randomized clinical trials. Hence, we aimed to assess the postoperative analgesic efficacy and safety of a single dose of sufentanil administered during the induction of remifentanil-based total intravenous anesthesia.

METHODS

Forty patients, scheduled for elective open abdominal surgery, were randomized to receive remifentanil-based total intravenous anesthesia with or without a single dose of sufentanil upon induction. We assessed the postoperative morphine consumption administered through a patient-controlled analgesia pump. Self-reported pain scores and the occurrence of nausea, vomiting, pruritus, agitation, somnolence and respiratory depression were also assessed up to 2 days after surgery.

RESULTS

The mean difference between the sufentanil and control groups regarding morphine consumption in the post-anesthetic care unit and at 12, 24 and 48h after surgery were -7.2mg (95%CI: -12.5 to -2.1, p<0.001), -3.9mg (95%CI: -11.9 to 4.7, p=0.26), -0.6mg (95%CI: (-12.7 to 12.7, p=0.80), and -1.8mg (95%CI: (-11.6 to 15.6, p=0.94), respectively. Neither self-reported pain nor the incidence of adverse events were significantly different between groups at any time point.

CONCLUSION

Our findings suggest that the administration of sufentanil during induction of remifentanil-based total intravenous anesthesia is associated with decreased early postoperative opioid consumption.