Prospective clinical validation of the Eleveld propofol pharmacokinetic-pharmacodynamic model in general anaesthesia

The drug titration paradox: a control engineering perspective

PURPOSE OF REVIEW

The drug titration paradox describes that, from a population standpoint, drug doses appear to have a negative correlation with its clinical effect. This paradox is a relatively modern discovery in anesthetic pharmacology derived from large clinical data sets. This review will interpret the paradox using a control engineering perspective.

RECENT FINDINGS

Drug titration is a challenging endeavor, and the medication delivery systems used in everyday clinical practice, including infusion pumps and vaporizers, typically do not allow for rapid or robust titration of medication being delivered. In addition, clinicians may be reluctant to deviate from a predetermined plan or may be content to manage patients within fixed goal boundaries.

SUMMARY

This drug titration paradox describes the constraints of how the average clinician will dose a patient with an unknown clinical response. While our understanding of the paradox is still in its infancy, it remains unclear how alternative dosing schemes, such as through automation, may exceed the boundaries of the paradox and potentially affect its conclusions.

Pharmacokinetics of propofol in severely obese surgical patients

BACKGROUND

Existing PK models of propofol include sparse data from very obese patients. The aim of this study was to develop a PK model based on standardised surgical conditions and spanning from normal-weight up to, and including, a high number of very obese patients.

METHODS

Adult patients scheduled for laparoscopic cholecystectomy or bariatric surgery were studied. Anaesthesia was induced with propofol 2 mg/kg adjusted body weight over 2 min followed by 6 mg/kg/h adjusted body weight over 30 min. For the remainder of the operation anaesthesia was maintained with sevoflurane. Remifentanil was dosed according to clinical need. Eight arterial samples were drawn in a randomised block sampling regimen over a span of 24 h. Time-concentration data were analysed by population PK modelling using non-linear mixed-effects modelling.

RESULTS

Four hundred and seventy four serum propofol concentrations were collected from 69 patients aged 19-60 years with a BMI 21.6-67.3 kg/m2. Twenty one patients had a BMI above 50 kg/m2. A 3-compartment PK model was produced wherein three different body weight descriptors and sex were included as covariates in the final model. Total body weight was found to be a covariate for clearance and Q3; lean body weight for V1, V2 and Q2; predicted normal weight for V3 and sex for V1. The fixed allometric exponent of 0.75 applied to all clearance parameters improved the performance of the model. Accuracy and precision were 1.4% and 21.7% respectively in post-hoc performance evaluation.

CONCLUSION

We have developed a new PK model of propofol that is suitable for all adult weight classes. Specifically, it is based on data from an unprecedented number of individuals with very high BMI.

Effect of Remimazolam on Induction and Maintenance of General Anesthesia in Kidney Transplant Patients

Purpose

This study aims to evaluate the effect of remimazolam on induction and maintenance of general anesthesia in kidney transplant patients.

Methods

120 patients undergoing kidney transplant were divided into two groups: Propofol group (Group P) and Remimazolam group (Group R). Anesthesia induction: remimazolam had injected IV at a dose of 0.15-0.35 mg/kg in Group R, while propofol had injected IV at a dose of 2.0-2.5 mg/kg in Group P. Anesthesia maintenance: remimazolam was injected IV at a dose of 0.3-1.0 mg·kg-1·h-1 and propofol was injected IV at a dose of 1-12 mg·kg-1·h-1 in Group R, propofol was injected IV at a dose of 3-12 mg·kg-1·h-1 in Group P. All patients have the same remaining anesthesia durgs.

Results

Compared with Group P, in Group R the time of disappearance of the eyelash reflex and the time to drop to 60 in BIS was longer (P < 0.05), the time of awakening was shorted (P < 0.05), the MAP of T6 was fluctuated less (P < 0.05), the incidence of hypotension and injection pain during induction was reduced (P < 0.001), the incidence of intraoperative bradycardia during operation was reduced (P < 0.05), the dosages of sedatives drug during maintenance was reduced (P < 0.05). There was no statistically significant difference in postoperative renal function between the two groups of patients (P > 0.05).

Conclusion

Remimazolam can be safely and effectively used for the induction and maintenance of general anesthesia in kidney transplant patients.

Ciprofol as compared to propofol for sedation and general anesthesia: a systematic review of randomized controlled trials

BACKGROUND

Propofol is the most commonly used hypnotic agent used during sedation and general anesthesia (GA) practice, offering faster recovery compared to benzodiazepines. However, cardiovascular impact of propofol and pain at injection are commonly encountered side effects. Ciprofol is a novel disubstituted phenol derivative, and there is growing evidence regarding its clinical use.

METHODS

We conducted a systematic literature search (updated on 23 July 2023) to evaluate safety and efficacy of ciprofol in comparison to propofol in patients undergoing procedures under sedation or GA. We focused on randomized controlled trials (RCTs) only, extrapolating data on onset and offset, and on the side effects and the pain at injection.

RESULTS

The search revealed 14 RCTs, all conducted in China. Eight RCTs studied patients undergoing sedation, and six focused on GA. Bolus of ciprofol for sedation or induction of GA varied from 0.2 to 0.5 mg/kg. In four studies using ciprofol for maintenance of GA, it was 0.8-2.4 mg/kg/h. Ciprofol pharmacokinetics seemed characterized by slower onset and offset as compared to propofol. Pain during injection was less frequent in the ciprofol group in all the 13 studies reporting it. Eight studies reported "adverse events" as a pooled outcome, and in five cases, the incidence was higher in the propofol group, not different in the remaining ones. Occurrence of hypotension was the most commonly investigated side effects, and it seemed less frequent with ciprofol.

CONCLUSION

Ciprofol for sedation or GA may be safer than propofol, though its pharmacokinetics may be less advantageous.

General purpose propofol target-controlled infusion using the marsh model with adjusted weight input

We report a simple method for adjusting the weight input of the Marsh target-controlled infusion (TCI) model such that the resulting infusion regime closely mimics the behaviour of the Eleveld model, thereby making the Marsh model more precise for patients at the extremes of age and body mass index. To assess the performance of our method, we simulated 2768 subjects with diverse combinations of age, weight, height and sex undergoing a hypothetical four-hour propofol TCI using both the Marsh model with our weight adjustment and the Eleveld model. The weight adjusted Marsh model produced infusion regimes and corresponding effect site concentrations closely mimicking that of the Eleveld model at all time points, with median and maximum absolute performance errors less than 8.1% and 20.3%, respectively, across the entire cohort. Our weight adjustment method is a simple and robust way of improving the precision of the Marsh model in patients at extremes of age and body mass index, until general purpose TCI models for propofol, such as the Eleveld model, become more widely available in commercial infusion pumps.

Evaluating inter-individual variability captured by the Eleveld pharmacokinetics model

Inter-individual variability in Pharmacokinetic (PK) and Pharmacodynamic (PD) models significantly affects the accuracy of Target Controlled Infusion and closed-loop control of anesthesia. We hypothesize that the novel Eleveld PK model captures more inter-individual variability relevant to both open-loop and closed-loop control design, resulting in reduced variability in PD models identified using the Eleveld PK model's plasma prediction compared to the Schuttler or Schnider PK model. We used a dataset of propofol infusion rates and Depth of Hypnosis measurements across three demographic groups: elderly, obese, and adult. PD models are identified based on plasma concentration prediction using three PK models (Schuttler, Schnider, and Eleveld). Validation methods are presented to confirm acceptable predictive performance and comparable PK-PD model variability within each demographic group. To test our hypothesis, we compared coefficient variations in step responses for open-loop control and multiplicative uncertainty of PD model sets for closed-loop control. Validated PKPD models using the Schuttler and Schnider PK model showed no significant differences in predictive response and multiplicative uncertainty compared to the Eleveld PK model. The coefficient variations in step responses of PD model sets and the frequency ranges, corresponding to uncertainty below one, were comparable for all three PK models. The comparison of the accumulated coefficient of variation in the step-response and the uncertainty of the PD model sets indicated that the Eleveld PK model does not offer any advantage for the design of open-loop or closed-loop control of anesthesia.

Drug Titration Paradox: An Emerging Concept in Clinical Pharmacology

When anesthesiologists titrate doses to achieve desired effects, a titration paradox emerges resulting in increased drug doses which correlate with decreased effect. This challenges traditional pharmacologic understanding and requires careful analysis of potential confounding factors.

Schnider and Eleveld Models for Propofol Target-Controlled Infusion Anesthesia: A Clinical Comparison

BACKGROUND

Various pharmacokinetic/pharmacodynamic (PK/PD) models have been developed to accurately dose propofol administration during total intravenous anesthesia with target-controlled infusion (TIVA-TCI). We aim to clinically compare the performance of the Schnider model and the new and general-purpose Eleveld PK/PD model during TIVA-TCI.

METHODS

We conducted a prospective observational study at a single center, enrolling 78 female patients, including 37 adults (aged < 65 years) and 41 elderly patients (aged ≥ 65 years). These patients underwent breast surgery with propofol-remifentanil TIVA-TCI guided by the bispectral index (BIS) for depth of anesthesia monitoring (target value 40-60) and the surgical plethysmographic index (SPI) for antinociception monitoring (target value 20-50) without neuromuscular blockade. The concentration at the effect site of propofol (CeP) at loss of responsiveness (LoR) during anesthesia maintenance (MA) and at return of responsiveness (RoR), the duration of surgery and anesthesia (min), the time to RoR (min), the propofol total dose (mg), the deepening of anesthesia events (DAEs), burst suppression events (BSEs), light anesthesia events (LAEs) and unwanted spontaneous responsiveness events (USREs) were considered to compare the two PK/PD models.

RESULTS

Patients undergoing BIS-SPI-guided TIVA-TCI with the Eleveld PK/PD model showed a lower CeP at LoR (1.7 (1.36-2.25) vs. 3.60 (3.00-4.18) μg/mL, p < 0.001), higher CePMA (2.80 (2.55-3.40) vs. 2.30 (1.80-2.50) μg/mL, p < 0.001) and at RoR (1.48 (1.08-1.80) vs. 0.64 (0.55-0.81) μg/mL, p < 0.001) than with the Schnider PK/PD model. Anesthetic hysteresis was observed only in the Schnider PK/PD model group (p < 0.001). DAEs (69.2% vs. 30.8%, p = 0.001) and BSEs (28.2% vs. 5.1%, p = 0.013) were more frequent with the Eleveld PK/PD model than with the Schnider PK/PD model in the general patient population. DAEs (63.2% vs. 27.3%, p = 0.030) and BSEs (31.6% vs. 4.5%, p = 0.036) were more frequent with the Eleveld PK/PD model than with the Schnider PK/PD model in the elderly.

CONCLUSIONS

The Schnider and Eleveld PK/PD models impact CePs differently. A greater incidence of DAEs and BSEs in the elderly suggests more attention is necessary in this group of patients undergoing BIS-SPI-guided TIVA-TCI with the Eleveld PK/PD than with the Schnider model.

The art of chasing numbers in titration of anaesthetic dose

There is no difference in between-patient variability of concentrations when comparing propofol and sevoflurane titrated to a bispectral index of 40-60. There is about a 300% variation in hypnotic concentration between the bottom 5% and top 5% of the population. Anaesthesia titration cannot be based solely on measured or estimated drug concentrations.

Clinical validation of an adapted Eleveld Model for high-dose propofol treatments for depression

Repeated administration of high doses of propofol to patients with treatment-resistant depression (TRD) has been shown to produce antidepressant effects in small clinical trials. These effects can be elicited when the patient's EEG burst-suppression ratio (BSR) is maintained at 70-90% for 15 min in repeated treatments. This deep anesthesia domain lies beyond the range of current propofol pharmacokinetic/pharmacodynamic (PK/PD) models. In this study, we adapt the Eleveld model for use at deep anesthesia levels with a BSR endpoint, with the goal of aiding the estimation of the dosage of propofol needed to achieve 70-90% BSR for 15 min. We test the ability of the adapted model to predict BSR for these treatments. Twenty participants underwent 6-9 treatments of high doses of propofol (5-9 of which were included in this analysis) for a total of 115 treatments. To adapt the Eleveld model for this endpoint, we optimized the model parameters Ke0, γ and Ce50. These parameters were then used in the adapted model to estimate second-by-second BSR for each treatment. Estimated BSR was compared with observed BSR for each treatment of each participant. Median absolute performance error (MdAPE) between the estimated and observed BSR (25th-75th percentile) was 6.63 (3.79-12.96) % points and 8.51 (4.32-16.74) % between the estimated and observed treatment duration. This predictive performance is statistically significantly better at predicting BSR compared with the standard Eleveld model at deep anesthesia levels. Our adapted Eleveld model provides a useful tool to aid dosing propofol for high-dose anesthetic treatments for depression.

General purpose models for intravenous anesthetics, the next generation for target-controlled infusion and total intravenous anesthesia?

PURPOSE OF REVIEW

There are various pharmacokinetic-dynamic models available, which describe the time course of drug concentration and effect and which can be incorporated into target-controlled infusion (TCI) systems. For anesthesia and sedation, most of these models are derived from narrow patient populations, which restricts applicability for the overall population, including (small) children, elderly, and obese patients. This forces clinicians to select specific models for specific populations.

RECENT FINDINGS

Recently, general purpose models have been developed for propofol and remifentanil using data from multiple studies and broad, diverse patient groups. General-purpose models might reduce the risks associated with extrapolation, incorrect usage, and unfamiliarity with a specific TCI-model, as they offer less restrictive boundaries (i.e., the patient "doesn't fit in the selected model") compared with the earlier, simpler models. Extrapolation of a model can lead to delayed recovery or inadequate anesthesia. If multiple models for the same drug are implemented in the pump, it is possible to select the wrong model for that specific case; this can be overcome with one general purpose model implemented in the pump.

SUMMARY

This article examines the usability of these general-purpose models in relation to the more traditional models.

Pharmacokinetic pharmacodynamic modeling of analgesics and sedatives in children

Pharmacokinetic pharmacodynamic modeling is an important tool which uses statistical methodology to provide a better understanding of the relationship between concentration and effect of drugs such as analgesics and sedatives. Pharmacokinetic pharmacodynamic models also describe between-subject variability that allows identification of subgroups and dose adjustment for optimal pain management in individual patients. This approach is particularly useful in the pediatric population, where most drugs have received limited evaluation and dosing is extrapolated from adult practice. In children, the covariates of weight and age are used to describe size- and maturation-related changes in pharmacokinetics. It is important to consider both size and maturation in order to develop an accurate model and determine the optimal dose for different age groups. An adequate assessment of analgesic and sedative effect using pain scales or brain activity measures is essential to build reliable pharmacokinetic pharmacodynamic models. This is often challenging in children due to the multidimensional nature of pain and the limited sensitivity and specificity of some measurement tools. This review provides a summary of the pharmacokinetic and pharmacodynamic methodology used to describe the dose-concentration-effect relationship of analgesics and sedation in children, with a focus on the different pharmacodynamic endpoints and the challenges of pharmacodynamic modeling.

Remimazolam vs Etomidate: Haemodynamic Effects in Hypertensive Elderly Patients Undergoing Non-Cardiac Surgery

Background

Remimazolam tosilate (RT) is a novel ultrashort-acting γ-aminobutyric acid subtype A (GABAA) agonist, with several advantages including rapid induction and recovery, stable haemodynamics, and mild respiratory inhibition. However, studies have not been conducted to explore the haemodynamic effects of RT in elderly hypertensive subjects undergoing non-cardiac surgery. Therefore, we sought to compare the effects of anaesthesia induction using different doses of RT and etomidate on the haemodynamics of this group of patients.

Methods

Patients were recruited into this single-center, prospective, randomized, double-blind trial from October 2022 to June 2023. A total of 150 hypertensive elderly undergoing non-cardiac surgery were randomly assigned into 0.2 mg/kg RT group (Group RL), 0.3 mg/kg RT group (Group RH) and 0.3 mg/kg etomidate group (Group E). The primary outcome of the study was haemodynamic changes (mean arterial pressure fluctuation value -∆MAP and heart rate fluctuation value -∆HR) observed during anaesthesia induction. Secondary outcomes included incidence of adverse cardiovascular events and adverse drug reactions (injection pain and myoclonus), cumulative doses of vasoactive drugs and vital signs at different time points.

Results

Patients in Group E and Group RL had significantly lower haemodynamic fluctuations (∆MAP), lower incidence of hypotension and cumulative dose of ephedrine than subjects in Group RH. Patients in groups RL and RH had significantly lower incidence of injection pain and myoclonus compared with patients in group E. The results showed no statistically significant differences in ∆HR, hypertension, bradycardia, tachycardia, and time to loss of eye-opening reflex and start of intubation, and vital signs at different time points among the three groups.

Conclusion

Use of low-dose RT (0.2 mg/kg) for induction of non-cardiac surgical anaesthesia in elderly hypertensive patients is more effective in maintaining haemodynamic stability and has fewer adverse effects compared with etomidate.

Pharmacokinetic and Pharmacodynamic Changes in the Elderly: Impact on Anesthetics

Anesthesiologists are increasingly required to care for frail elderly patients. A detailed knowledge of the influence of age on the pharmacokinetics and dynamics of the anesthetic drugs is essential for optimal safety and care. For most of the anesthetic drugs, the elderly need lower doses to achieve the same plasma concentrations, and at any given plasma and effect-site concentration, they will have more profound clinical effects than younger patients. Caution is required, with close monitoring of clinical effects and active titration of dose administration to achieve the desired level of effect, ideally following the "start low, go slow" principle.

How obesity affects the disposition of intravenous anesthetics

PURPOSE OF REVIEW

Understanding the changes in drug disposition of intravenous anesthetics in patients with obesity and administering appropriate doses are critical to avoid intraoperative awareness with recall because of underdosing and over-sedation and delayed emergence due to overdosing. Pharmacokinetic simulation or target-controlled infusion (TCI) using models that have been adapted to patients with obesity are necessary to select appropriate dosing regimens. This review aimed to describe the pharmacokinetic concepts underpinning the use of intravenous anesthetics, including propofol, remifentanil, and remimazolam, in patients with obesity.

RECENT FINDINGS

In the last 5 years, a series of pharmacokinetic models for propofol, remifentanil, and remimazolam that were estimated from populations that included obese patients have been published. These new pharmacokinetic models can be considered 'second generation' compared with earlier models in that they expand the range of covariate effects (e.g. the extremes of body weight and age) accounted for by the models. The predictive performances of each pharmacokinetic model have been shown in the literature to be within clinically acceptable limits. Among them, the propofol model by Eleveld et al. has been externally validated and has shown reasonable predictive accuracy.

SUMMARY

Pharmacokinetic simulations or TCI using pharmacokinetic models that account for the influence of obesity on a drug's disposition are essential to predict plasma/effect-site concentrations of intravenous anesthetics and understand the temporal profile of drug concentrations and effect in patients with obesity, particularly severe obesity.

Effect of propofol combined with different anesthetic drugs on respiratory circulation function and erythrocyte immunity in patients undergoing intestinal endoscopic submucosal dissection

BACKGROUND

Endoscopic submucosal dissection (ESD) is a difficult procedure with disadvantages of long operating time, intraoperative stimulation of sympathetic nerve excitation and postoperative pain, and suppression of immune function.

AIM

To investigate the effect of propofol combined with different anesthesia drugs in patients undergoing intestinal ESD.

METHODS

One hundred and fifty patients who planned to undergo intestinal ESD at our hospital from January 2019 to August 2022 were selected and randomly divided into three groups: A, B, and C, with 50 patients in each group. Group A was given propofol + sufentanil + nalbuphine, group B was given propofol + sufentanil, and group C was given propofol. Mean arterial pressure (MAP) and respiratory and circulatory function (pressure airway, Paw), partial pressure of end-expiratory carbon dioxide (P_ETCO₂), bispectral index (BIS), red blood cell immunity [RBC immunocomplex rosette rate (RBC-ICR), erythrocyte cell membrane C3b receptor rosette rate (RBC-C3bR), and cooperative tumor erythrocyte rosette rate (ATER)], intraoperative and post-operative conditions, and adverse reactions were compared among the groups.

RESULTS

Paw and P_ETCO₂ in group A were significantly lower than those in group B and group C from T1 to T3 (P < 0.05). There was no statistically significant difference in BIS values among the three groups from T0 to T3 (P < 0.05). The amount of propofol used, the number of analgesic pump compressions within 48 h after surgery, and the consumption of analgesic pump drugs were significantly lower in group A than in group B and group C (P < 0.05). There was no significant difference in the incidence of adverse reactions among the three groups (P > 0.05).

CONCLUSION

Propofol combined with sufentanil and nalbuphine can better alleviate respiratory and circulatory function inhibition, improve red cell immunity, and reduce the dosage of analgesic drugs in patients with intestinal ESD, with high safety.

Diversity of electroencephalographic patterns during propofol-induced burst suppression

Burst suppression is a brain state consisting of high-amplitude electrical activity alternating with periods of quieter suppression that can be brought about by disease or by certain anesthetics. Although burst suppression has been studied for decades, few studies have investigated the diverse manifestations of this state within and between human subjects. As part of a clinical trial examining the antidepressant effects of propofol, we gathered burst suppression electroencephalographic (EEG) data from 114 propofol infusions across 21 human subjects with treatment-resistant depression. This data was examined with the objective of describing and quantifying electrical signal diversity. We observed three types of EEG burst activity: canonical broadband bursts (as frequently described in the literature), spindles (narrow-band oscillations reminiscent of sleep spindles), and a new feature that we call low-frequency bursts (LFBs), which are brief deflections of mainly sub-3-Hz power. These three features were distinct in both the time and frequency domains and their occurrence differed significantly across subjects, with some subjects showing many LFBs or spindles and others showing very few. Spectral-power makeup of each feature was also significantly different across subjects. In a subset of nine participants with high-density EEG recordings, we noted that each feature had a unique spatial pattern of amplitude and polarity when measured across the scalp. Finally, we observed that the Bispectral Index Monitor, a commonly used clinical EEG monitor, does not account for the diversity of EEG features when processing the burst suppression state. Overall, this study describes and quantifies variation in the burst suppression EEG state across subjects and repeated infusions of propofol. These findings have implications for the understanding of brain activity under anesthesia and for individualized dosing of anesthetic drugs.

Humidity and measurement of volatile propofol using MCC-IMS (EDMON)

The bedside Exhaled Drug MONitor - EDMON measures exhaled propofol in ppbv every minute based on multi-capillary column - ion mobility spectrometry (MCC-IMS). The MCC pre-separates gas samples, thereby reducing the influence of the high humidity in human breath. However, preliminary analyses identified substantial measurement deviations between dry and humid calibration standards. We therefore performed an analytical validation of the EDMON to evaluate the influence of humidity on measurement performance. A calibration gas generator was used to generate gaseous propofol standards measured by an EDMON device to assess linearity, precision, carry-over, resolution, and the influence of different levels of humidity at 100% and 1.7% (without additional) relative humidity (reference temperature: 37°C). EDMON measurements were roughly half the actual concentration without additional humidity and roughly halved again at 100% relative humidity. Standard concentrations and EDMON values correlated linearly at 100% relative humidity (R²=0.97). The measured values were stable over 100min with a variance ≤ 10% in over 96% of the measurements. Carry-over effects were low with 5% at 100% relative humidity after 5min of equilibration. EDMON measurement resolution at 100% relative humidity was 0.4 and 0.6 ppbv for standard concentrations of 3 ppbv and 41 ppbv. The influence of humidity on measurement performance was best described by a second-order polynomial function (R²≥0.99) with influence reaching a maximum at about 70% relative humidity. We conclude that EDMON measurements are strongly influenced by humidity and should therefore be corrected for sample humidity to obtain accurate estimates of exhaled propofol concentrations.

Population pharmacokinetic and pharmacodynamic model of propofol externally validated in Korean elderly subjects

The Eleveld propofol pharmacokinetic (PK) model, which was developed based on a broad range of populations, showed greater bias (- 27%) in elderly subjects in a previous validation study conducted by Vellinga and colleagues. We aimed to develop and externally validate a new PK-pharmacodynamic (PK-PD) model of propofol for elderly subjects. A population PK-PD model was constructed using propofol plasma concentrations and bispectral index (BIS) values that were obtained from 31 subjects aged 65 years older in previously published phase I studies. The predictive performance of the newly-developed PK-PD model (Choi model) was assessed in a separate Korean elderly population and compared with that of the Eleveld model. A three-compartment mammillary model using an allometric expression and a sigmoid E_max model well-described the time courses of propofol concentrations and BIS values. The V₁, V₂, V₃, Cl, Q₁, Q₂, E₀, E_max, Ce₅₀, γ, and k_e0 of a 60-kg subject were 8.36, 58.0, 650 L, 1.26, 0.917, 0.669 L/min, 92.1, 18.7, 2.21 μg/mL, 2.89, and 0.138 /min, respectively. In the Choi model and Eleveld model, pooled biases (95% CI) of the propofol concentration were 7.78 ( 3.09-12.49) and 16.70 (9.46-23.93) and pooled inaccuracies were 22.84 (18.87-26.81) and 24.85 (18.07-31.63), respectively. The Choi PK model was less biased than the Eleveld PK model in Korean elderly subjects (age range: 65.0-79.0 yr; weight range: 45.0-75.3 kg). Our results suggest that the Choi PK model, particularly, is applicable to target-controlled infusion in non-obese Korean elderly subjects.

Model enhanced reinforcement learning to enable precision dosing: A theoretical case study with dosing of propofol

Extending the potential of precision dosing requires evaluating methodologies offering more flexibility and higher degree of personalization. Reinforcement learning (RL) holds promise in its ability to integrate multidimensional data in an adaptive process built toward efficient decision making centered on sustainable value creation. For general anesthesia in intensive care units, RL is applied and automatically adjusts dosing through monitoring of patient's consciousness. We further explore the problem of optimal control of anesthesia with propofol by combining RL with state-of-the-art tools used to inform dosing in drug development. In particular, we used pharmacokinetic-pharmacodynamic (PK-PD) modeling as a simulation engine to generate experience from dosing scenarios, which cannot be tested experimentally. Through simulations, we show that, when learning from retrospective trial data, more than 100 patients are needed to reach an accuracy within the range of what is achieved with a standard dosing solution. However, embedding a model of drug effect within the RL algorithm improves accuracy by reducing errors to target by 90% through learning to take dosing actions maximizing long-term benefit. Data residual variability impacts accuracy while the algorithm efficiently coped with up to 50% interindividual variability in the PK and 25% in the PD model's parameters. We illustrate how extending the state definition of the RL agent with meaningful variables is key to achieve high accuracy of optimal dosing policy. These results suggest that RL constitutes an attractive approach for precision dosing when rich data are available or when complemented with synthetic data from model-based tools used in model-informed drug development.

What's New in Intravenous Anaesthesia? New Hypnotics, New Models and New Applications

New anaesthetic drugs and new methods to administer anaesthetic drugs are continually becoming available, and the development of new PK-PD models furthers the possibilities of using arget controlled infusion (TCI) for anaesthesia. Additionally, new applications of existing anaesthetic drugs are being investigated. This review describes the current situation of anaesthetic drug development and methods of administration, and what can be expected in the near future.

Response surface model comparison and combinations for remifentanil and propofol in describing response to esophageal instrumentation and adverse respiratory events

BACKGROUND

The primary aim of this essay was to explore the best fitting model in remifentanil-propofol combined administrations during esophageal instrumentation (EI) from five distinct response surface models. The secondary aim was to combine the models to give appropriate effect-site drug concentrations (Ces) range with maximal comfort and safety.

METHODS

The Greco, reduced Greco, Minto, Scaled C50 Hierarchy and Fixed C50 Hierarchy models were constructed to fit four drug effects: loss of response to esophageal instrumentation (LREI), loss of response to esophageal instrumentation revised (LREIR), intolerable ventilatory depression (IVD) and respiratory compromise (RC). Models were tested by chi-square statistical test and evaluated with Akaike Information Criterion (AIC). Model prediction performance were measured by successful prediction rate (SPR) and three prediction errors.

RESULTS

The reduced Greco model was the best fitting model for LREI and RC, and the Minto model was the best fitting model for LREIR and IVD. The SPRs of reduced Greco model for LREI and RC were 81.76% and 79.81%. The SPRs of Minto model for LREIR and IVD were 80.32% and 80.12%. Overlay of the reduced Greco model for LREI and Minto model for IVD offered visual aid for guidance in drug administration.

CONCLUSIONS

Using proper response surface model to fit different drug effects will describe the interactions between anesthetic drugs better. Combining response surface models to select the more reliable effect-site drug concentrations range can be used to guide clinical drug administration with greater safety and provide an improvement of anesthesia precision.

Online exhaled propofol monitoring in normal-weight and obese surgical patients

Background

Ion mobility spectrometry (IMS) allows for online quantification of exhaled propofol concentrations. We aimed to validate a bedside online IMS device, the Edmon^®, for predicting plasma concentrations of propofol in normal‐weight and obese patients.

Methods

Patients with body mass index (BMI) >20 kg/m² scheduled for laparoscopic cholecystectomy or bariatric surgery were recruited. Exhaled propofol concentrations (C_A), arterial plasma propofol concentrations (C_P) and bispectral index (BIS) values were collected during target‐controlled infusion (TCI) anaesthesia. Generalised estimation equation (GEE) was applied to all samples and stable‐phase samples at different delays for best fit between C_P and C_A. BMI was evaluated as covariate. BIS and exhaled propofol correlations were also assessed with GEE.

Results

A total of 29 patients (BMI 20.3–53.7) were included. A maximal R² of 0.58 was found during stable concentrations with 5 min delay of C_A to C_P; the intercept a = −0.69 (95% CI −1.7, 0.3) and slope b = 0.87 (95% CI 0.7, 1.1). BMI was found to be a non‐significant covariate. The median absolute performance error predicting plasma propofol concentrations was 13.4%. At a C_A of 5 ppb, the model predicts a C_P of 3.6 μg/ml (95% CI ±1.4). There was a maximal negative correlation of R² = 0.44 at 2‐min delay from C_A to BIS.

Conclusions

Online monitoring of exhaled propofol concentrations is clinically feasible in normal‐weight and obese patients. With a 5‐min delay, our model outperforms the Marsh plasma TCI model in a post hoc analysis. Modest correlation with plasma concentrations makes the clinical usefulness questionable.

General Purpose Pharmacokinetic-Pharmacodynamic Models for Target-Controlled Infusion of Anaesthetic Drugs: A Narrative Review

Target controlled infusion (TCI) is a clinically-available and widely-used computer-controlled method of drug administration, adjusting the drug titration towards user selected plasma- or effect-site concentrations, calculated according to pharmacokinetic-pharmacodynamic (PKPD) models. Although this technology is clinically available for several anaesthetic drugs, the contemporary commercialised PKPD models suffer from multiple limitations. First, PKPD models for anaesthetic drugs are developed using deliberately selected patient populations, often excluding the more challenging populations, such as children, obese or elderly patients, of whom the body composition or elimination mechanisms may be structurally different compared to the lean adult patient population. Separate PKPD models have been developed for some of these subcategories, but the availability of multiple PKPD models for a single drug increases the risk for invalid model selection by the user. Second, some models are restricted to the prediction of plasma-concentration without enabling effect-site controlled TCI or they identify the effect-site equilibration rate constant using methods other than PKPD modelling. Advances in computing and the emergence of globally collected databases has allowed the development of new “general purpose” PKPD models. These take on the challenging task of identifying the relationships between patient covariates (age, weight, sex, etc) and the volumes and clearances of multi-compartmental pharmacokinetic models applicable across broad populations from neonates to the elderly, from the underweight to the obese. These models address the issues of allometric scaling of body weight and size, body composition, sex differences, changes with advanced age, and for young children, changes with maturation and growth. General purpose models for propofol, remifentanil and dexmedetomidine have appeared and these greatly reduce the risk of invalid model selection. In this narrative review, we discuss the development, characteristics and validation of several described general purpose PKPD models for anaesthetic drugs.

Bayesian statistics in anesthesia practice: a tutorial for anesthesiologists

This narrative review intends to provide the anesthesiologist with the basic knowledge of the Bayesian concepts and should be considered as a tutorial for anesthesiologists in the concept of Bayesian statistics. The Bayesian approach represents the mathematical formulation of the idea that we can update our initial belief about data with the evidence obtained from any kind of acquired data. It provides a theoretical framework and a statistical method to use pre-existing information within the context of new evidence. Several authors have described the Bayesian approach as capable of dealing with uncertainty in medical decision-making. This review describes the Bayes theorem and how it is used in clinical studies in anesthesia and critical care. It starts with a general introduction to the theorem and its related concepts of prior and posterior probabilities. Second, there is an explanation of the basic concepts of the Bayesian statistical inference. Last, a summary of the applicability of some of the Bayesian statistics in current literature is provided, such as Bayesian analysis of clinical trials and PKPD modeling.

Propofol Suppresses Cell Progression by Inhibiting CCL18 Expression in Hepatoblastoma

Background

Propofol is an anesthetic commonly used clinically and has been found to have antitumor activity in various cancers. The purpose of this study was to investigate the role of propofol in hepatoblastoma (HB).

Methods

CCK-8 and transwell were used to measure cell proliferation, migration, and invasion in HB cells. Cell apoptosis rate was measured by FCM. The expression of CCL18 in HB tissues and cells was detected by RT-qPCR. Western blotting was used to explore the protein expression of CCK18- and PI3K/AKT-related proteins.

Results

The expression of CCL18 in HB tissues and cells was overexpressed compared with control groups. CCL18 knockdown was found to notably block cell proliferation and progression, while enhancing cell apoptosis in HuH-6 and HepT1 cells. Furthermore, propofol suppressed the proliferation of HB cells in a dose-dependent manner. According to the results, we chose 5 μg/mL of propofol-treated cells for 48 hours as the subsequent experimental conditions. We found that propofol (5 μg/mL, 48 h) significantly blocked cell migration and invasion, but induced cell apoptosis in HuH-6 and HepT1 cells. In addition, CCK18 overexpression facilitated cell progression in HB cells, while propofol dramatically suppressed the effect of CCK18. Besides that, propofol suppressed the PI3K/AKT pathway.

Conclusion

Propofol suppressed the development of HB cells by inhibiting CCK18 expression and the PI3K/AKT pathway. Therefore, we infer that propofol plays a role in the treatment of HB.