Changes in apparent systemic clearance of propofol during transplantation of living related donor liver

Benefits of remimazolam as an anesthetic sedative for older patients: A review

Owing to the decreased levels of receptors in the peripheral and central nervous systems, the functions of various organ systems decline in older patients. When administering anesthesia to older patients, it is necessary to consider the effects of medication on the homeostatic balance. Remimazolam, a new benzodiazepine, was recently developed as an anesthetic drug that has shown promise in clinical anesthesia application owing to its molecular structure, targets, pharmacodynamics, and pharmacokinetic characteristics. Remimazolam exhibits a rapid onset and metabolism, with minor effects on liver and kidney functions. Moreover, the drug has a specific antagonist, flumazenil. It is safer to use in older patients than other anesthetic sedatives and has been widely used since its introduction. Comparisons of the pharmacokinetics, metabolic pathways, effects on target organs, and hemodynamics of different drugs with those of commonly used anesthetic sedative drugs are useful to inform clinical practice. This article elaborates on the benefits of remimazolam compared with those of other anesthetic sedatives for sedation in older patients to demonstrate how it offers a new option for anesthetics in older patients. In cases involving older patients with increased clinical complexities or very old patients requiring anesthesia, remimazolam can be selected as the preferred anesthetic sedative, as outlined in this review.

Considerations for Satisfactory Sedation during Dental Implant Surgery

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

Influence of anesthesia type on post-reperfusion syndrome during liver transplantation: a single-center retrospective study

Background

Post-reperfusion syndrome (PRS) results in sudden hemodynamic instability following graft reperfusion. Although PRS is known to influence outcomes following liver transplantation, little is known regarding the effects of anesthetics on PRS. This study investigated the association between the type of anesthetic agent and PRS in liver transplantation.

Methods

This single-center retrospective cohort study included patients who underwent liver transplantation between June 2016 and December 2019. Patients were divided into sevoflurane and propofol groups according to the anesthetic agent used. Stabilized inverse probability of treatment weighting (IPTW) analysis was performed to investigate the association between PRS identified based on blood pressure recordings and the type of anesthesia. Associations between the anesthetic agent and the duration of hypotension as well as early postoperative outcomes were also investigated.

Results

Data were analyzed for 398 patients, 304 (76.4%) and 94 (23.6%) of whom were anesthetized with propofol and sevoflurane, respectively. PRS developed in 40.7% of the 398 patients. Following stabilized IPTW analysis, the association with PRS was lower in the sevoflurane group than in the propofol group (odds ratio, 0.47; P = 0.018). However, there was no association between the type of anesthetic used and early postoperative outcomes.

Conclusions

The association of PRS was lower in the sevoflurane group than in the propofol group. However, there was no association between the type of anesthetic and the early postoperative outcomes. Further studies are required to determine the optimal anesthetic for liver transplantation.

Clinical Importance of Potential Genetic Determinants Affecting Propofol Pharmacokinetics and Pharmacodynamics

Interindividual variability in response to drugs used in anesthesia has long been considered the rule, not the exception. It is important to mention that in anesthesiology, the variability in response to drugs is multifactorial, i.e., genetic and environmental factors interact with each other and thus affect the metabolism, efficacy, and side effects of drugs. Propofol (2,6-diisopropylphenol) is the most common intravenous anesthetic used in modern medicine. Individual differences in genetic factors [single nucleotide polymorphisms (SNPs)] in the genes encoding metabolic enzymes, molecular transporters, and molecular binding sites of propofol can be responsible for susceptibility to propofol effects. The objective of this review (through the analysis of published research) was to systematize the influence of gene polymorphisms on the pharmacokinetics and pharmacodynamics of propofol, to explain whether and to what extent the gene profile has an impact on variations observed in the clinical response to propofol, and to estimate the benefit of genotyping in anesthesiology. Despite the fact that there has been a considerable advance in this type of research in recent years, which has been largely limited to one or a group of genes, interindividual differences in propofol pharmacokinetics and pharmacodynamics may be best explained by the contribution of multiple pathways and need to be further investigated.

Exhaled Propofol Concentrations Correlate With Plasma and Brain Tissue Concentrations in Rats

BACKGROUND

Propofol can be measured in exhaled gas. Exhaled and plasma propofol concentrations correlate well, but the relationship with tissue concentrations remains unknown. We thus evaluated the relationship between exhaled, plasma, and various tissue propofol concentrations. Because the drug acts in the brain, we focused on the relationship between exhaled and brain tissue propofol concentrations.

METHODS

Thirty-six male Sprague-Dawley rats were anesthetized with propofol, ketamine, and rocuronium for 6 hours. Animals were randomly assigned to propofol infusions at 20, 40, or 60 mg·kg·h (n = 12 per group). Exhaled propofol concentrations were measured at 15-minute intervals by multicapillary column-ion mobility spectrometry. Arterial blood samples, 110 µL each, were collected 15, 30, and 45 minutes, and 1, 2, 4, and 6 hours after the propofol infusion started. Propofol concentrations were measured in brain, lung, liver, kidney, muscle, and fat tissue after 6 hours. The last exhaled and plasma concentrations were used for linear regression analyses with tissue concentrations.

RESULTS

The correlation of exhaled versus plasma concentrations (R = 0.71) was comparable to the correlation of exhaled versus brain tissue concentrations (R = 0.75) at the end of the study. In contrast, correlations between plasma and lung and between lung and exhaled propofol concentrations were poor. Less than a part-per-thousand of propofol was exhaled over 6 hours.

CONCLUSIONS

Exhaled propofol concentrations correlate reasonably well with brain tissue and plasma concentrations in rats, and may thus be useful to estimate anesthetic drug effect. The equilibration between plasma propofol and exhaled gas is apparently independent of lung tissue concentration. Only a tiny fraction of administered propofol is eliminated via the lungs, and exhaled quantities thus have negligible influence on plasma concentrations.

Clinical Pharmacokinetics and Pharmacodynamics of Propofol

Propofol is an intravenous hypnotic drug that is used for induction and maintenance of sedation and general anaesthesia. It exerts its effects through potentiation of the inhibitory neurotransmitter γ-aminobutyric acid (GABA) at the GABAA receptor, and has gained widespread use due to its favourable drug effect profile. The main adverse effects are disturbances in cardiopulmonary physiology. Due to its narrow therapeutic margin, propofol should only be administered by practitioners trained and experienced in providing general anaesthesia. Many pharmacokinetic (PK) and pharmacodynamic (PD) models for propofol exist. Some are used to inform drug dosing guidelines, and some are also implemented in so-called target-controlled infusion devices, to calculate the infusion rates required for user-defined target plasma or effect-site concentrations. Most of the models were designed for use in a specific and well-defined patient category. However, models applicable in a more general population have recently been developed and published. The most recent example is the general purpose propofol model developed by Eleveld and colleagues. Retrospective predictive performance evaluations show that this model performs as well as, or even better than, PK models developed for specific populations, such as adults, children or the obese; however, prospective evaluation of the model is still required. Propofol undergoes extensive PK and PD interactions with both other hypnotic drugs and opioids. PD interactions are the most clinically significant, and, with other hypnotics, tend to be additive, whereas interactions with opioids tend to be highly synergistic. Response surface modelling provides a tool to gain understanding and explore these complex interactions. Visual displays illustrating the effect of these interactions in real time can aid clinicians in optimal drug dosing while minimizing adverse effects. In this review, we provide an overview of the PK and PD of propofol in order to refresh readers' knowledge of its clinical applications, while discussing the main avenues of research where significant recent advances have been made.

Effects of neoadjuvant chemotherapy on the depth of total intravenous anesthesia in patients with breast cancer undergoing unilateral modified radical mastectomy: A prospective observational study

Toxic effects of neoadjuvant chemotherapy (NC) on nervous, hepatorenal, and pulmonary systems might affect general anesthesia depth. This study aimed to evaluate the effects of NC on depth of total intravenous anesthesia.This prospective observational study enrolled 60 patients undergoing elective unilateral modified radical mastectomy during total intravenous anesthesia with propofol and remifentanil (January-June 2015; Liaocheng People's Hospital, China): the NC group (n = 30) received NC, while the control group (n = 30) did not. Propofol and remifentanil dosages were adjusted according to indexes of consciousness (IoC1: sedation; IoC2: analgesia) to control fluctuations of blood pressure and heart rate within 20% of baseline values. Parameters reflecting propofol/remifentanil dosages, intraoperative adverse events, and quality of anesthetic recovery were recorded.The duration of propofol infusion (1.3 ± 0.4 vs 1.8 ± 0.5 hours, P < .05), mean propofol dosage (8.0 ± 1.0 vs 9.3 ± 1.5 mg kg h, P < .05), and adjustment frequency of target-controlled remifentanil infusion (2.9 ± 1.8 vs 4.4 ± 2.6 times/surgery, P < .05) were significantly lower in the NC group than in the control group; adjustment frequency of target-controlled propofol infusion was also numerically lower (2.0 ± 1.1 vs 2.7 ± 1.5 times/surgery, P = .053). Duration of remifentanil infusion, mean remifentanil dosage, voluntary eye opening, extubation time, and recovery score were not significantly different between groups. The incidence of tachycardia was lower in the NC group than in the control group (7.1% vs 37.0%, P < .05), but there was no significant difference in the incidence of total adverse events between groups.NC can enhance the sensitivity of breast cancer patients to the anesthetic effect of propofol.

Pilot study of closed-loop anaesthesia for liver transplantation

BACKGROUND

Automated titration of propofol and remifentanil guided by the bispectral index (BIS) has been used for numerous surgical procedures. Orthotopic liver transplantation (OLT) uniquely combines major changes in circulating volume, an anhepatic phase, and ischaemia-reperfusion syndrome. We assessed the behaviour of this automated controller during OLT.

METHODS

Adult patients undergoing OLT were included in this pilot study. Consumption of propofol and remifentanil was calculated for each surgery period (dissection, anhepatic, and liver reperfusion phases). Arterial blood samples were collected at several time points to allow comparison of actual with calculated propofol and remifentanil concentrations. Data are presented as median [25th and 75th percentiles] or percentage (95% confidence interval).

RESULTS

Thirteen patients were studied. System performance, defined as the percentage of time with BIS in the range 40-60, was 88% (86-94) of the total duration of anaesthesia. Propofol requirement was decreased during the anhepatic phase compared with the dissection phase (2.9 [1.9-5.0] mg kg(-1) h(-1) and 4.6 [3.5-8.1] mg kg(-1) h(-1); P<0.03) while remifentanil consumption was unchanged (0.11 [0.09-0.19] µg kg- (1) min(-1)). Bland-Altman analysis showed a weak concordance for propofol (bias of 0.7 µg ml(-1) and limits of agreement of -2.2 to +3.7 µg ml(-1)) and remifentanil (bias of 1.3 ng ml(-1) and limits of agreement -4.3 to +6.8 ng ml(-1)). No adverse events were reported during anaesthesia.

CONCLUSIONS

This pilot study indicates that automated titration of propofol and remifentanil guided by the BIS is feasible during OLT.

Pharmacokinetics of drugs in adult living donor liver transplant patients: regulatory factors and observations based on studies in animals and humans

INTRODUCTION

Limited information is available on the pharmacokinetics of drugs in the donors and recipients following adult living donor liver transplantation (LDLT). Given that both the donors and recipients receive multiple drug therapies, it is important to assess the pharmacokinetics of drugs used in these patients.

AREAS COVERED

Pathophysiological changes that occur post-surgery and regulatory factors that may influence pharmacokinetics of drugs, especially hepatic drug metabolism and transport in both LDLT donors and the recipients are discussed. Pharmacokinetic data in animals with partial hepatectomy are presented. Clinical pharmacokinetic data of certain drugs in LDLT recipients are further reviewed.

EXPERT OPINION

It takes up to six months for the liver volume to return to normal after LDLT surgery. In the LDLT recipients, drug exposure generally is higher with lower clearance during early period post-transplant; lower initial dosages of immunosuppressants are used than deceased donor liver transplant recipients during the first six months post-transplantation. In animals, the activities of hepatic drug metabolizing enzymes and transporters are known to be altered differentially during liver regeneration. Future studies on the actual hepatic function with reference to drug metabolism, drug transport, and biliary secretion in both LDLT donors and recipients are required.

Hemodynamic and biochemical changes in liver transplantation: A retrospective comparison of desflurane and total intravenous anesthesia by target-controlled infusion under auditory evoked potential guide

OBJECTIVES

Propofol-based total intravenous anesthesia (TIVA) has been used successfully for liver transplantation (LT) in recent years. However, there are few discourses in the literature which focus on the merits and weakness in perioperative management, biochemical changes, and postoperative recovery between TIVA and desflurane anesthesia (DES).

METHODS

We retrospectively compared the circumstances of liver transplantation recipients who had the surgery carried out under propofol-based TIVA or DES in the period from September 2007 to August 2010. Preoperative characteristics, date of intraoperative management, hemodynamic profiles, concentration of anesthetics, biochemical changes, and circumstances of postoperative recovery were retrieved from the hospital database for analysis.

RESULTS

We included 111 patients who received the surgery under either TIVA (n = 66) or DES (n = 45). Patient demographics, baseline laboratory data, operation time, and fluid management did not differ between the two groups. In comparison with the DES group, fewer patients had to be administered norepinephrine (21.2% vs. 42.2%; p = 0.020) in the TIVA group; moreover, the total dosage of norepinephrine was lower (0.003 ± 0.005 mg vs. 0.006 ± 0.008 mg; p = 0.012) in the TIVA group during liver reperfusion phase. Blood lactate level was higher in the DES group than in the TIVA group after the anhepatic phase. TIVA patients woke up faster than those in the DES group (54.0 ± 33.4 minutes vs. 95.0 ± 78.3 minutes; p = 0.034).

CONCLUSION

Our results suggest that propofol-based TIVA may provide better hemodynamics and microcirculation during the anhepatic phase in liver transplantation.

Anesthetic management of an 8-month-old infant with osteogenesis imperfecta undergoing liver transplantation: a case report

Anesthetic management of pediatric liver transplantation in a patient with osteogenesis imperfecta (OI) requires tough decisions and comprehensive considerations of the cascade of effects that may arise and the required monitoring. Total intravenous anesthesia (TIVA) with propofol and remifentanil was chosen as the main anesthetic strategy. Malignant hyperthermia (MH), skeletal fragility, anhepatic phase during liver transplantation, uncertainties of TIVA in children, and propofol infusion syndrome were considered and monitored. There were no adverse events during the operation. Despite meticulous precautions with regard to the risk of MH, there was an episode of high fever (40℃) in the ICU a few hours after the operation, which was initially feared as MH. Fortunately, MH was ruled out as the fever subsided soon after hydration and antipyretics were given. Although the delivery of supportive care and the administration of dantrolene are the core principles in the management of MH, perioperative fever does not always mean a MH in patients at risk for MH, and other common causes of fever should also be considered.

Propofol Protects against Ischemia/Reperfusion Injury Associated with Reduced Apoptosis in Rat Liver

Propofol is an intravenous anesthetic, reported to have a protective effect against ischemia/reperfusion (I/R) injury in heart and brain, but no definite data are available concerning its effect in hepatic I/R. This work investigated the effect of propofol anesthesia on hepatic I/R injury using in vivo rat model. Four groups of rats were included: sham operated, I/R (30 min ischemia and 2 h reperfusion), I/R treated with propofol (10 mg/kg/h), and I/R treated with propofol (20 mg/kg/h). Liver enzyme leakage, TNF-α and caspase-3 levels, and antiapoptotic Bcl-xL/apoptotic Bax gene expression, together with histopathological changes, were used to evaluate the extent of hepatic I/R injury. Compared with sham-operated group, I/R group showed significant increase in serum levels of liver enzymes (ALT, AST), TNF-α, and caspase-3 and significant decrease in the Bcl-xL/Bax ratio, associated with histopathologic damage in liver. Propofol infusion significantly attenuated these changes with reduced hepatic histopathologic lesions compared with nonpreconditioned I/R group. However, no significant differences were found between two groups treated with different doses of propofol. In conclusion, propofol infusion reduced hepatic I/R injury with decreased markers of cellular apoptosis. Therefore, propofol anesthesia may provide a useful hepatic protection during liver surgery.

Role of glycogen synthase kinase 3β in protective effect of propofol against hepatic ischemia-reperfusion injury

BACKGROUND

It was previously reported that propofol, an intravenously administered hypnotic and anesthetic agent, protects organs from ischemia-reperfusion (I/R) injury. However, the underlying mechanisms are largely unknown. Glycogen synthase kinase 3β (GSK-3β) is known to play an important role in the oxidative stress-induced apoptosis. In this study, we investigated the role of GSK-3β and mitochondrial permeability transition pore (MPTP) in the protective effects of propofol against hepatic I/R injury.

MATERIALS AND METHODS

The left and median hepatic artery and the portal vein branches were blocked by no-damage artery clips to create the model of partial ischemia (70%), and liver lobes were subjected to warm ischemia for 30, 60, 90 min, respectively. Reperfusion of 120 min was then initiated by the removal of clamp. The MPTP opening was assessed by measuring mitochondrial large amplitude swelling and mitochondrial membrane potential.

RESULTS

Pretreatment with propofol in conditions of hepatic I/R inhibits the apoptosis of hepatocytes as evidenced by decreased terminal deoxynucleotidyl transferase dUTP nick end labeling-positive cells. Importantly, propofol suppressed the mitochondrial GSK-3β by promoting or preserving its phosphorylation at Ser9, thus restraining the opening of MPTP and preventing the mitochondrial swell and mitochondrial membrane potential collapse.

CONCLUSIONS

Propofol protects liver from I/R injury by sustaining the mitochondrial function, which is possibly involved with the modulation of MPTP and GSK-3β.

Application of a physiologically based pharmacokinetic model to assess propofol hepatic and renal glucuronidation in isolation: utility of in vitro and in vivo data

A physiologically based pharmacokinetic (PBPK) modeling approach was used to assess the prediction accuracy of propofol hepatic and extrahepatic metabolic clearance and to address previously reported underprediction of in vivo clearance based on static in vitro-in vivo extrapolation methods. The predictive capacity of propofol intrinsic clearance data (CLint) obtained in human hepatocytes and liver and kidney microsomes was assessed using the PBPK model developed in MATLAB software. Microsomal data obtained by both substrate depletion and metabolite formation methods and in the presence of 2% bovine serum albumin were considered in the analysis. Incorporation of hepatic and renal in vitro metabolic clearance in the PBPK model resulted in underprediction of propofol clearance regardless of the source of in vitro data; the predicted value did not exceed 35% of the observed clearance. Subsequently, propofol clinical data from three dose levels in intact patients and anhepatic subjects were used for the optimization of hepatic and renal CLint in a simultaneous fitting routine. Optimization process highlighted that renal glucuronidation clearance was underpredicted to a greater extent than liver clearance, requiring empirical scaling factors of 17 and 9, respectively. The use of optimized clearance parameters predicted hepatic and renal extraction ratios within 20% of the observed values, reported in an additional independent clinical study. This study highlights the complexity involved in assessing the contribution of extrahepatic clearance mechanisms and illustrates the application of PBPK modeling, in conjunction with clinical data, to assess prediction of clearance from in vitro data for each tissue individually.

The influence of the severity of chronic virus-related liver disease on propofol requirements during propofol-remifentanil anesthesia

PURPOSE

The purpose of this study was to investigate the influence of chronic virus- related liver disease severity on propofol requirements.

MATERIALS AND METHODS

In this study, 48 male patients with chronic hepatitis B infection were divided into three groups according to Child-Turcotte-Pugh classification of liver function (groups A, B, and C with mild, moderate and severe liver disease, respectively). After intubation, propofol concentration was adjusted by ± 0.3 μg/mL increments to maintain bispectral index in the range of 40-60. Target propofol concentrations at anesthesia initiation, pre-intubation and pre-incision were recorded.

RESULTS

The initial concentration used in group C was significantly lower than that used in group A or B (p<0.05), whereas no difference was observed between groups A and B. At pre-intubation, the actual required concentration of propofol increased significantly (3.2 μg/mL) in group A (p<0.05), which lead to significant differences between the groups (p<0.05). At pre-incision, the requirements for propofol decreased significantly in both groups A and B (3.0 μg/mL and 2.7 μg/mL, respectively) compared with those at pre-intubation (p<0.05), and were significantly different for all three groups (p<0.05), with group C demonstrating the lowest requirement (2.2 μg/mL). The required concentrations of propofol at pre-incision were similar to those at induction.

CONCLUSION

In this study, propofol requirements administered by target-controlled infusion to maintain similar depths of hypnosis were shown to depend on the severity of chronic virus-related liver dysfunction. In other words, patients with the most severe liver dysfunction required the least amount of propofol.

The population pharmacokinetics of fentanyl in patients undergoing living-donor liver transplantation

Fentanyl, an opioid analgesic with a high hepatic extraction ratio, is frequently used to supplement general anesthesia during liver transplantation and is also continuously infused to provide postoperative analgesia. However, because fentanyl is metabolized mainly in the liver, the pharmacokinetics of fentanyl may vary widely during the different phases of the surgery, potentially leading to adverse events. Using nonlinear mixed-effects modeling, we characterized the pharmacokinetics of fentanyl in 15 patients (American Society of Anesthesiologists Physical Status Classification 2 or 3) undergoing living-donor liver transplantation (LDLT). Fentanyl was continuously infused at the rate of 200-400 µg/h throughout the operation. The time course of the fentanyl plasma concentration levels was best described in terms of a two-compartment model. Estimates were made of the pharmacokinetic parameters during the preanhepatic, anhepatic, and neohepatic phases: central volume of distribution (V(1)) (l): 59.0 + hourly volume infused by rapid infusion system (RIS) × 42.5, 113.0, and 189.0, respectively, × (body weight/69)(1.3); peripheral volume of distribution (V(2)) (l): 94.3, 412.0, and 427.0, respectively; intercompartmental clearance (Q) (l/h): 96.4 × (cardiac output (CO)/6.7)(2.5), 22.6, and 28.2, respectively; metabolic clearance (Cl) (l/h): 21.7 during the preanhepatic and neohepatic phases, and 0 during the anhepatic phase. The preanhepatic central volume of distribution was found to be markedly influenced by the massive infusion of fluids and blood products. The more hyperdynamic the circulation was during the preanhepatic phase, the higher the distributional clearance.

[Perioperative anaesthetic practices in liver transplantation in France: Evolution between 2004 and 2008]

OBJECTIVES

To determine the evolution of French perioperative anaesthetic practices in liver transplantation between 2004 and 2008.

STUDY DESIGN

Phone survey.

METHODS

In 2004 and 2008, a similar questionnaire has been administered by phone to a senior anaesthesiologist from each French centre performing adult liver transplantation (n = 21). Results were compared using Fisher test and p < 0.05 was considered significant.

RESULTS

Between 2004 and 2008, there was a trend towards an increase of centres performing transplantation for more than 40% of Child C patients (p = 0.1). Simultaneously, work force dedicated to liver transplantation cases has been reduced since in 2008, one anaesthesiologist was in charge in 90% of the centres (p = 0.06 vs 2004). Perioperative practices remained largely heterogeneous between centres with regard to hemodynamic monitoring, fluid and blood products management, antifibrinolytics use or postoperative analgesia.

CONCLUSIONS

This French survey has shown a reduction of work force dedicated to a liver transplantation from 2004 to 2008 simultaneously with a trend towards a greater severity of liver recipients. Practices heterogeneity reflect at least in part, unresolved questions about the best perioperative management for liver transplantation and the need for guidelines. Working for standardization of our practices and multicentric trials could allow gaining a better understanding of what should be the good practices in perioperative management of liver transplantation.

Influence of obesity on propofol pharmacokinetics: derivation of a pharmacokinetic model

BACKGROUND

The objective of this study was to develop a pharmacokinetic (PK) model to characterize the influence of obesity on propofol PK parameters.

METHODS

Nineteen obese ASA II patients undergoing bariatric surgery were studied. Patients received propofol 2 mg kg(-1) bolus dose followed by a 5-20-40-120 min, 10-8-6-5 mg kg(-1) h(-1) infusion. Arterial blood samples were withdrawn at 1, 3, 5 min after induction, every 10-20 min during propofol infusion, and every 10-30 min for 2 h after stopping the propofol infusion. Arterial samples were processed by high-performance liquid chromatography. Time-concentration data profiles from this study were pooled with data from two other propofol PK studies available at http://www.opentci.org. Population PK modelling was performed using non-linear mixed effects model.

RESULTS

The study involved 19 obese adults who contributed 163 observations. The pooled analysis involved 51 patients (weight 93 sd 24 kg, range 44-160 kg; age 46 sd 16 yr, range 25-81 yr; BMI 33 sd 9 kg m(-2), range 16-52 kg m(-2)). A three-compartment model was used to investigate propofol PK. An allometric size model using total body weight (TBW) was superior to all other models investigated (linear TBW, free fat mass, lean body weight, normal fat mass) for all clearance parameters. Variability in V2 and Q2 was reduced by a function showing a decrease in both parameters with age.

CONCLUSIONS

We have derived a population PK model using obese and non-obese data to characterize propofol PK over a wide range of body weights. An allometric model using TBW as the size descriptor of volumes and clearances was superior to other size descriptors to characterize propofol PK in obese patients.

Comparison of the effects of propofol and pentobarbital on hydrogen peroxide-stimulated hepatic SNU761 cells

BACKGROUND

Propofol and barbiturates are both known to protect cells of several organs against ischemia/reperfusion injury, but there are few reports on any possible protective effects on human hepatocytes. We investigated the activities of both agents on human hepatic SNU761 cells under hydrogen peroxide (H(2)O(2))-induced oxidative stress.

METHODS

To determine whether propofol and pentobarbital protect hepatocytes from H(2)O(2)-induced toxicity, we used SNU761 cells, a human hepatocellular carcinoma (HCC) cell line. Cells were pretreated with different dosages (1, 10, 50 microM) of propofol or pentobarbital (1, 10, 50, 100, 400 microM) 30 min before H(2)O(2) application. Lactate dehydrogenase (LDH) was measured to assess and quantify cell death. To determine the nature of cell death, treated hepatocytes were doubly stained with fluorescein isothiocyanate (FITC)-labeled Annexin V and propidium iodide (PI), and analyzed by flow cytometry.

RESULTS

Pretreatment with propofol, but not pentobarbital, suppressed H(2)O(2)-induced LDH release. In Annexin V-FITC/PI binding analysis, propofol decreased the number of necrotic and late apoptotic cells, but no significant decreases in such cell numbers were seen when pentobarbital was used.

CONCLUSIONS

Unlike pentobarbital, propofol, at clinical concentrations, protected SNU-761 HCC cells against oxidative stress.

Interest of BIS monitoring to guide propofol infusion during the anhepatic phase of orthotopic liver transplantation

OBJECTIVE

The anhepatic phase of orthotopic liver transplantation (OLT) is associated with significant changes in pharmacokinetics. The aim of this study was to compare the influence of this phase on propofol target concentrations during BIS guided target controlled infusion (TCI).

STUDY DESIGN

Prospective study.

PATIENTS AND METHODS

Eight patients aged 25 to 65 years, Child-Pugh status A-B scheduled for OLT were prospectively included. Anesthesia was performed using TCI of propofol (Diprifusor, Marsh pharmacokinetic model), sufentanil and cisatracurium. Propofol target concentration was adjusted to maintain BIS values between 40 and 50.

RESULTS

To maintain stable BIS values, propofol target concentrations should be decreased during the anhepatic phase versus the dissection one (2.0 microg/ml+/-0.8 versus 3.0 microg/ml+/-0.9, p<0.0001).

CONCLUSION

BIS could be useful to titrate propofol infusion during the anhepatic phase of OLT.

Intestinal UGTs as potential modifiers of pharmacokinetics and biological responses to drugs and xenobiotics

Uridine 5'-diphosphate-glucuronosyltransferases (UGTs) are the biological catalysts of glucuronidation, a major pathway of conjugative metabolism of drugs and xenobiotics. In addition to the liver and kidney, UGTs are highly expressed in the gastrointestinal tract, where they have the potential to influence the pharmacokinetics and biological effects of ingested drugs and xenobiotics. This paper reviews the current evidence for the contributions of intestinal UGTs to presystemic 'first-pass' metabolism and drug bioavailability, the extent of enterohepatic cycling and the clearance of drugs from plasma, as well as their influence on biological responses to drugs, including drug toxicity. The prediction of the effects of intestinal glucuronidation on these processes depends on knowledge of the types and amounts of UGTs expressed in the small intestine and their specific glucuronidating activities. Whereas the types of UGTs expressed in human gastrointestinal tract are well characterized, further research is needed to understand the absolute amounts of UGTs in the small intestine and the causes of observed high-interindividual variability in the intestinal expression of UGTs.

Total body propofol clearance (TBPC) after living-donor liver transplantation (LDLT) surgery is decreased in patients with a long warm ischemic time

Metabolic capacity after liver transplant surgery may be affected by the graft size and by hepatic injury during the surgery. This study was carried out to investigate the postoperative total body propofol clearance (TBPC) in living-donor liver transplantation (LDLT) patients and to investigate the major factors that contribute to decreased postoperative TBPC in LDLT patients. Fourteen patients scheduled for LDLT were included in this study. Propofol was administered at a rate of 2.0 mg.kg(-1).h(-1) as a sedative in the intensive care unit (ICU) setting. To calculate TBPC, propofol arterial blood concentration was measured by HPLC. Five variables were selected as factors affecting postoperative TBPC; bleeding volume (BLD), warm ischemic time (WIT), cold ischemic time (CIT), graft weight/standard liver volume ratio (GW/SLV), and portal blood flow after surgery (PBF). After factor analysis of six variables, including TBPC, varimax rotation was carried out, and this yielded three interpretable factors that accounted for 75.5% of the total variance in the data set. TBPC, WIT, CIT, and BLD were loaded on the first factor, PBF on the second factor, and GW/SLV on the third factor. The adjusted correlation coefficient between TBPC and WIT showed the highest value (r = -0.61) in the first factor. The LDLT patients were divided into two groups according to WIT; group A (WIT > 100 min) and group B (WIT < 100 min). Mean TBPC values in group A and group B were 14.6 +/- 2.1 and 28.5 +/- 4.1 ml.kg(-1).min(-1), respectively (P < 0.0001). These data suggest that LDLT patients with a long WIT have a risk of deteriorated drug metabolism.

Influence of Atropine on the Dose Requirements of Propofol in Humans

OBJECTIVE

The purpose of this study was to evaluate the effect of atropine on the dose requirement of propofol for induction of anesthesia and propofol concentrations during continuous infusion.

METHODS

Study 1: Forty patients were randomly allocated to the control or atropine groups. Induction of anesthesia commenced 3 min following the administration of 0.9% saline or atropine (0.01 mg kg(-1)), using a Diprifuser set to achieve propofol concentration of 6.0 microg mL(-1). The primary end point was the propofol dose per kg at the moment of loss of response to a command. Study 2: Fifteen patients undergoing elective surgery were enrolled. Propofol was administered to all subjects via target-controlled infusion to achieve a propofol concentration at 2.0 microg mL(-1) after intubation. Before and after administration of atropine (0.01 mg kg(-1)), cardiac output (CO) was measured using indocyanine green as an indicator and blood propofol concentration was determined using high-performance liquid chromatography.

RESULTS

Study 1: The propofol dose for each group was 2.22+/-0.21 mg kg(-1) for control group and 2.45+/-0.28 mg kg(-1) for atropine, respectively (p=0.014). Study 2: After the administration of atropine, CO was significantly increased from 4.28+/-0.83 to 5.76+/-1.55 l min(-1) (p<0.0001). Propofol concentration was significantly decreased from 2.12+/-0.28 to 1.69+/-0.27 microg mL(-1) (p<0.0001).

CONCLUSIONS

Following the administration of atropine, the propofol requirements for the induction of anesthesia were increased and propofol concentrations were decreased during continuous infusion by the administration of atropine.