Target-controlled Infusion Anesthesia Research Articles

Effect of target-controlled infusion of remifentanil in combination with propofol on anesthesia and endotracheal intubation response in patients undergoing surgical aneurysm clipping

Purpose: To investigate the effect of target-controlled infusion of remifentanil in combination with propofol on anesthesia and endotracheal intubation response in patients undergoing surgical aneurysm clipping. 
 Methods: The clinical data of 106 patients undergoing surgical aneurysm clipping at the Central Hospital of Wuhan, Wuhan City, China from September 2020 to December 2022 were retrospectively analyzed. Subjects in control group were given fentanyl intravenous infusion anesthesia while study group was treated with target-controlled infusion anesthesia of remifentanil combined with propofol. Hemodynamics and blood-gas indices were evaluated before anesthesia (T1), immediately after endotracheal intubation (T2) and at extubation (T3). The incidence of anesthesia-related complications was determined. 
 Results: In study group, the agitation score was decreased compared to that of control group, while the Ramsay sedation score was increased (p < 0.05). The incidence of cough during endotracheal catheter indwelling and extubation was 7. 27 % in study group, which was less than 21. 57 % in control group (p < 0.05). The cough score of study group was also reduced (p < 0.05). There were no significant differences in the SpO2 and PetCO2 values between the two groups at different times (p > 0.05). Furthermore, the mean arterial pressure at T2 and T3 was upregulated and heart rate (HR) was downregulated in study group (p < 0.05). Recovery time of spontaneous respiration, time of eye-opening and extubation in study group were decreased compared to control group (p < 0.05). 
 Conclusion: Target-controlled infusion of remifentanil in combination with propofol improves anesthetic effect in patients undergoing surgical aneurysm clipping, reduces tracheal intubation reaction, maintains hemodynamic stability and improves recovery quality of patients. Future study will be required to evaluate the efficacy and optimal effective concentration in a diverse population.

Electroencephalographic guided propofol-remifentanil TCI anesthesia with and without dexmedetomidine in a geriatric population: electroencephalographic signatures and clinical evaluation.

Elderly and multimorbid patients are at high risk for developing unfavorable postoperative neurocognitive outcomes; however, well-adjusted and EEG-guided anesthesia may help titrate anesthesia and improve postoperative outcomes. Over the last decade, dexmedetomidine has been increasingly used as an adjunct in the perioperative setting. Its synergistic effect with propofol decreases the dose of propofol needed to induce and maintain general anesthesia. In this pilot study, we evaluate two highly standardized anesthetic regimens for their potential to prevent burst suppression and postoperative neurocognitive dysfunction in a high-risk population. Prospective, randomized clinical trial with non-blinded intervention. Operating room and post anesthesia care unit at Hospital Base San José, Osorno/Universidad Austral, Valdivia, Chile. 23 patients with scheduled non-neurologic, non-cardiac surgeries with age > 69years and a planned intervention time > 60min. Patients were randomly assigned to receive either a propofol-remifentanil based anesthesia or an anesthetic regimen with dexmedetomidine-propofol-remifentanil. All patients underwent a slow titrated induction, followed by a target controlled infusion (TCI) of propofol and remifentanil (n = 10) or propofol, remifentanil and continuous dexmedetomidine infusion (n = 13). We compared the perioperative EEG signatures, drug-induced changes, and neurocognitive outcomes between two anesthetic regimens in geriatric patients. We conducted a pre- and postoperative Montreal Cognitive Assessment (MoCa) test and measured the level of alertness postoperatively using a sedation agitation scale to assess neurocognitive status. During slow induction, maintenance, and emergence, burst suppression was not observed in either group; however, EEG signatures differed significantly between the two groups. In general, EEG activity in the propofol group was dominated by faster rhythms than in the dexmedetomidine group. Time to responsiveness was not significantly different between the two groups (p = 0.352). Finally, no significant differences were found in postoperative cognitive outcomes evaluated by the MoCa test nor sedation agitation scale up to one hour after extubation. This pilot study demonstrates that the two proposed anesthetic regimens can be safely used to slowly induce anesthesia and avoid EEG burst suppression patterns. Despite the patients being elderly and at high risk, we did not observe postoperative neurocognitive deficits. The reduced alpha power in the dexmedetomidine-treated group was not associated with adverse neurocognitive outcomes.

External validation of the modified Marsh and Schnider models for medium-chain triglyceride propofol in target-controlled infusion anesthesia

BackgroundPropofol formulated with medium- and long-chain triglycerides (MCT/LCT propofol) has rapidly replaced propofol formulated with long-chain triglycerides (LCT propofol). Despite this shift, the modified Marsh and Schnider pharmacokinetic models developed using LCT propofol are still widely used for target-controlled infusion (TCI) of propofol. This study aimed to validate the external applicability of these models by evaluating their predictive performance during TCI of MCT/LCT propofol in general anesthesia.MethodsAdult patients (n = 48) undergoing elective surgery received MCT/LCT propofol via a TCI system using either the modified Marsh or Schnider models. Blood samples were collected at various target propofol concentrations and at specific time points, including the loss of consciousness and the recovery of consciousness (13 samples per patient). The actual plasma concentration of propofol was determined using high-performance liquid chromatography. The predictive performance of each pharmacokinetic model was assessed by calculating four parameters: inaccuracy, bias, divergence, and wobble.ResultsBoth the modified Marsh and Schnider models demonstrated predictive performances within clinically acceptable ranges for MCT/LCT propofol. The inaccuracy values were 24.4% for the modified Marsh model and 26.9% for the Schnider model. Both models showed an overall positive bias, 16.4% for the modified Marsh model and 16.6% for the Schnider model. The predictive performance of MCT/LCT propofol was comparable to that of LCT propofol, suggesting formulation changes might exert only a minor impact on the reliability of the TCI system during general anesthesia. Additionally, both models exhibited higher bias and inaccuracy at target concentrations ranging from 3.5 ~ 5 ug/ml than at concentrations between 2 ~ 3 ug/ml.ConclusionsThe modified Marsh and Schnider models, initially developed for LCT propofol, remain clinically acceptable for TCI with MCT/LCT propofol.Trial registrationThis study was registered at the Clinical Research Information Service of the Korean National Institute of Health (https://cris.nih.go.kr; registration number: KCT0002191; 06/01/2017).

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

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. 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. 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. 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.

Pro-Con Debate: Should All General Anesthesia Be Done Using Target-Controlled Propofol Infusion Guided by Objective Monitoring of Depth of Anesthesia?

In this Pro-Con commentary article, we discuss whether all general anesthesia should be done using target-controlled propofol anesthesia guided by monitoring of depth of anesthesia. This is an ongoing debate since more than 25 years, representing a scientific, cultural as well as geographical divide in the anesthesia community. The Pro side argues that total intravenous anesthesia causes less postoperative nausea and higher patient satisfaction than anesthesia using volatile anesthetics. Target-controlled infusion (TCI) of anesthetic agents allows for better titration of intravenous anesthesia using pharmacokinetic models. Processed EEG monitors, such as bispectral index monitoring, allows for better assessing the effect of TCI anesthesia than solely assessment of clinical parameters, such as ECG or blood pressure. The combination of TCI propofol and objective depth of anesthesia monitoring allows creating a pharmacokinetic-pharmacodynamic profile for each patient. Finally, anesthesia using volatile anesthetics poses health risks for healthcare professionals and contributes to greenhouse effect. The Con side argues that for procedures accompanied with ischemia and reperfusion injury of an organ or tissue and for patients suffering from a severe inflammation' the use of volatile anesthetics might well have its advantages above propofol. In times of sudden shortage of drugs, volatile anesthetics can overcome the restriction in the operating theater or even on the intensive care unit, which is another advantage. Volatile anesthetics can be used for induction of anesthesia when IV access is impossible, end-tidal measurements of volatile anesthetic concentration allows confirmation that patients receive anesthetics. Taking environmental considerations into account, both propofol and volatile anesthetics bear certain harm to the environment, be it as waste product or as greenhouse gases. The authors therefore suggest to carefully considering advantages and disadvantages for each patient in its according environment. A well-balanced choice based on the available literature is recommended. The authors recommend careful consideration of advantages and disadvantages of each technique when tailoring an anesthetic to meet patient needs. Where appropriate, anesthesia providers are encouraged to account for unique features of anesthetic drug behavior, patient-reported and observed postoperative outcomes, and economic and environmental considerations when choosing any of the 2 described techniques.

SEDATION IN COLONOSCOPY: WHATTHE EFFECT-SITE CONCENTRATION OF PROPOFOL IN TARGET-CONTROLLED INFUSION FOR WHICH THE ACTBECAMECOMFORTABLE AT THE INTRODUCTION OF COLONOSCOPE?

Method: Prospective observational study carried out over 5 months, with the objective of determining the effect-site concentration of propofol in target-controlled infusion anesthesia which allows the introduction of a colonoscope under the best conditions.84 patients aged 18 to 71 are included: 38% were male and 46% female, with 57% classified as ASA I and 43% as ASA II. Results: Among the 84 patients: 47.6% had no history, 11.9% hypertensive, 14.3% diabetic, 21.4% dyslipidemic, 4.8% followed for stable heart failure. Reflex loss concentrations averaged 3.78 ug/mL with a minimum of 2.6 ug/mL and maximum of 4.8 ug/mL.While the target concentrations of the introduction of colonoscope which allows comfort for the gastroenterologist and the patient were on average 5.24 ug/mL with a minimum of 3.4 ug/mL and maximum of 6.8 ug/mL.

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

BackgroundIon 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.MethodsPatients with body mass index (BMI) >20 kg/m2 scheduled for laparoscopic cholecystectomy or bariatric surgery were recruited. Exhaled propofol concentrations (CA), arterial plasma propofol concentrations (CP) 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 CP and CA. BMI was evaluated as covariate. BIS and exhaled propofol correlations were also assessed with GEE.ResultsA total of 29 patients (BMI 20.3–53.7) were included. A maximal R 2 of 0.58 was found during stable concentrations with 5 min delay of CA to CP; 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 CA of 5 ppb, the model predicts a CP of 3.6 μg/ml (95% CI ±1.4). There was a maximal negative correlation of R 2 = 0.44 at 2‐min delay from CA to BIS.ConclusionsOnline 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.

Evaluating the role of Smartpilot® view assisted target-controlled infusion anesthesia during intracranial mass surgery: A comparative retrospective study with bispectral index-guided standard anesthesia

Background/Aim: Neuroanesthesia necessitates the control of both systemic and cerebral hemodynamics, the prevention of intracranial pressure increase, knowledge of anesthetics’ cerebral effects, and early neurological recovery. The titration of anesthetics becomes crucial to optimize the appropriate level of anesthesia required for surgery while reducing postoperative neurological consequences. Smartpilot® View (SPV) is a new decision support system that uses pharmacologic models to optimize anesthetic depth and improve patient outcomes. The goal of this study was to compare the effectiveness of SPV with standard BIS-guided anesthesia administration in terms of intraoperative hemodynamic stabilization, anesthetic consumption, and postoperative recovery times during intracranial mass surgery. Methods: Following ethics committee approval, the records of the patients who underwent elective supratentorial craniotomy between November 15, 2017 and March 15, 2018 were reviewed retrospectively. The demographics of the patients, anesthesia and surgery times, eye opening and extubation times, time to reach an Aldrete score of 9 and anesthetic consumptions were compared between those who were monitored with SPV in addition to BIS (SPV Group) and those who were monitored with solely BIS for standard anesthetic follow-up (BIS Group). Results: A total of 139 subjects were analyzed (SPV (n=71), BIS (n=68)). Hemodynamic responses to induction and intubation were more pronounced in the BIS group (P<0.05). Time until eye opening and extubation were 3.6 (2.4) versus 6.06 (1.63) minutes and 5.76 (1.3) versus 9.16 (1.0) minutes in the SPV and BIS groups (P<0.001). In the SPV Group, it took much less time to achieve an Aldrete score of 9 or above (P<0.001). Total consumed amount of both propofol and remifentanil were significantly lower in the SPV group (P<0.001). Conclusion: Use of SPV compared to BIS-guided routine anesthesia follow-up improved titration and consumption of anesthetic drugs, thereby facilitating the early recovery process in patients who underwent intracranial mass surgery.

Effect of dexmedetomidine on Nociception Level Index-guided remifentanil antinociception: A randomised controlled trial.

The effect of dexmedetomidine on Nociception Level Index-guided (Medasense, Israel) antinociception to reduce intra-operative opioid requirements has not been previously investigated. We aimed to determine if low-dose dexmedetomidine would reduce remifentanil requirements during Nociception Level Index-guided antinociception without increasing complications associated with dexmedetomidine. Double-blind randomised controlled trial. Two university teaching hospitals in Brussels, Belgium. American Society of Anesthesiologists 1 and 2 patients (n = 58) undergoing maxillofacial or cervicofacial surgery under propofol--remifentanil target-controlled infusion anaesthesia. A 30 min infusion of dexmedetomidine, or equal volume of 0.9% NaCl, was infused at 1.2 μg kg-1 h-1 immediately preceding induction and then decreased to 0.6 μg kg-1 h-1 until 30 min before ending surgery. Nociception Level Index and frontal electroencephalogram guided the remifentanil and propofol infusions, respectively. The primary outcome was the remifentanil requirement. Other outcomes included the propofol requirement, cardiovascular status and postoperative outcome. Mean ± SD remifentanil (3.96 ± 1.95 vs. 4.42 ± 2.04 ng ml-1; P = 0.0024) and propofol (2.78 ± 1.36 vs. 3.06 ± 1.29 μg ml-1; P = 0.0046) TCI effect site concentrations were lower in the dexmedetomidine group at 30 min postincision and remained lower throughout surgery. When remifentanil (0.133 ± 0.085 vs. 0.198 ± 0.086 μg kg-1 min-1; P = 0.0074) and propofol (5.7 ± 2.72 vs. 7.4 ± 2.80 mg kg-1 h-1; P = 0.0228) requirements are represented as infusion rates, this effect became statistically significant at 2 h postincision. In ASA 1 and 2 patients receiving Nociception Level Index-guided antinociception, dexmedetomidine decreases intra-operative remifentanil requirements. Combined frontal electroencephalogram and Nociception Level Index monitoring can measure dexmedetomidine's hypnotic and opioid-sparing effects during remifentanil-propofol target-controlled infusion anaesthesia. Clinicaltrials.gov: NCT03912740, EudraCT: 2018-004512-22.

Tuning consciousness: Anesthetic-sparing effect of varying sound on sedative anesthesia

This study aimed to identify the anesthetic-sparing effect of different intraoperative sound on sedated patients under propofol target controlled infusion anesthesia (TCI). 90 patients scheduled for transvaginal oocyte retrieval surgery (TVOR) were available and randomized into three groups: patients isolated from background noise(S), patients listened to a voice calling their names (CN), or patients listened to the classical music (CM). The main outcome was the value of total propofol consumption/surgical time. In the result, the value of total propofol consumption/surgical time for the CM group was 22.48% lower than CN group. The value of ΔEntropy and ΔCE for the CM group were also lower than that for the CN group (-2.17±4.13 vs. 1.33±3.43, P-value<0.001) (-0.17±0.28 vs. 0.07±0.25, P-value<0.001). We concluded that participants under propofol TCI who were listening to classical music had lower CE value, Entropy level and reduced 22.48% total propofol consumption/surgical time compared to those called by their names.

Effect of Hemodynamic Changes in Plasma Propofol Concentrations Associated with Knee-Chest Position in Spinal Surgery: A Prospective Study.

BackgroundAnesthesia induction and maintenance with propofol can be guided by target-controlled infusion (TCI) systems using pharmacokinetic (Pk) models. Physiological variables, such as changes in cardiac output (CO), can influence propofol pharmacokinetics. Knee-chest (KC) surgical positioning can result in CO changes.ObjectivesThis study aimed to evaluate the relationship between propofol plasma concentration prediction and CO changes after induction and KC positioning.MethodsThis two-phase prospective cohort study included 20 patients scheduled for spinal surgery. Two different TCI anesthesia protocols were administered after induction. In phase I (n = 9), the loss of consciousness (LOC) concentration was set as the propofol target concentration and CO changes following induction and KC positioning were quantified. In phase II (n = 11), based on data from phase I, two reductions in the propofol target concentration on the pump were applied after LOC and before KC positioning. Propofol plasma concentrations were measured at different moments in both phases: after induction and after KC positioning.ResultsSchnider Pk model showed a good performance in predicting propofol concentration after induction; however, after KC positioning, when a significant drop in CO occurred, the measured propofol concentrations were markedly underestimated. Intended reductions in the propofol target concentration did not attenuate HD changes. In the KC position, there was no correlation between the propofol concentration estimated by the Pk model and the measured concentration in plasma, as the latter was much higher (P = 0.013) while CO and BIS decreased significantly (P < 0.001 and P = 0.004, respectively).ConclusionsOur study showed that the measured propofol plasma concentrations during the KC position were significantly underestimated by the Schnider Pk model and were associated with significant CO decrease. When placing patients in the KC position, anesthesiologists must be aware of pharmacokinetic changes and, in addition to standard monitoring, the use of depth of anesthesia and cardiac output monitors may be considered in high-risk patients.

Practicalities of Total Intravenous Anesthesia and Target-controlled Infusion in Children.

Propofol administered in conjunction with an opioid such as remifentanil is used to provide total intravenous anesthesia for children. Drugs can be given as infusion controlled manually by the physician or as automated target-controlled infusion that targets plasma or effect site. Smart pumps programmed with pharmacokinetic parameter estimates administer drugs to a preset plasma concentration. A linking rate constant parameter (keo) allows estimation of effect site concentration. There are two parameter sets, named after the first author describing them, that are commonly used in pediatric target-controlled infusion for propofol (Absalom and Kataria) and one for remifentanil (Minto). Propofol validation studies suggest that these parameter estimates are satisfactory for the majority of children. Recommended target concentrations for both propofol and remifentanil depend on the type of surgery, the degree of surgical stimulation, the use of local anesthetic blocks, and the ventilatory status of the patient. The use of processed electroencephalographic monitoring is helpful in pediatric total intravenous anesthesia and target-controlled infusion anesthesia, particularly in the presence of neuromuscular blockade.

Comparison of Propofol Target-Controlled Infusion Anesthesia and Bolus Injection in Electroconvulsive Therapy

Comparison of Propofol Target-Controlled Infusion Anesthesia and Bolus Injection in Electroconvulsive Therapy

Comparison of the Effects of Dexmedetomidine on the Induction of Anaesthesia Using Marsh and Schnider Pharmacokinetic Models of Propofol Target-Controlled Infusion.

The study aimed to determine the effects of dexmedetomidine on the induction of anaesthesia using different models (Marsh and Schnider) of propofol target-controlled infusion (TCI). Sixty-four patients aged 18-60 years, American Society of Anaesthesiologists (ASA) class I-II who underwent elective surgery were randomised to a Marsh group (n = 32) or Schnider group (n = 32). All the patients received a 1 μg/kg loading dose of dexmedetomidine, followed by TCI anaesthesia with remifentanil at 2 ng/mL. After the effect-site concentration (Ce) of remifentanil reached 2 ng/mL, propofol TCI induction was started. Anaesthesia induction commenced in the Marsh group at a target plasma concentration (Cpt) of 2 μg/mL, whereas it started in the Schnider group at a target effect-site concentration (Cet) of 2 μg/mL. If induction was delayed after 3 min, the target concentration (Ct) was gradually increased to 0.5 μg/mL every 30 sec until successful induction. The Ct at successful induction, induction time, Ce at successful induction and haemodynamic parameters were recorded. The Ct for successful induction in the Schnider group was significantly lower than in the Marsh group (3.48 [0.90] versus 4.02 [0.67] μg/mL; P = 0.01). The induction time was also shorter in the Schnider group as compared with the Marsh group (134.96 [50.91] versus 161.59 [39.64]) sec; P = 0.02). There were no significant differences in haemodynamic parameters and Ce at successful induction. In the between-group comparison, dexmedetomidine reduced the Ct requirement for induction and shortened the induction time in the Schnider group. The inclusion of baseline groups without dexmedetomidine in a four-arm comparison of the two models would enhance the validity of the findings.

Significant decreases in blood propofol concentrations during adrenalectomy for phaeochromocytoma.

The kinetics of propofol are influenced by cardiac output. The aim of this study was to examine changes in blood propofol concentrations during phaeochromocytoma surgery using target-controlled infusion (TCI) anaesthesia with propofol. This is a prospective observational study. Ten patients with phaeochromocytoma who underwent unilateral adrenalectomy were included. Cardiac output was measured using an arterial pressure-based cardiac output analysis method. The target blood propofol concentrations were adjusted to maintain an approximate bispectral index (BIS) value of 40 before initiating surgery. The settings remained constant during surgery. Blood samples for propofol concentrations were collected from the radial artery at seven time points: two before tumour manipulation (T1, 2), two during tumour manipulation (T3, 4), and three after tumour vein ligation (T4-7). BIS values, the arterial pressure cardiac index (APCI) and haemodynamic parameters were measured at the same time points as the blood samples. The prop-ratio was calculated by dividing blood propofol concentrations by target concentrations of TCI. APCI increased during tumour manipulation and after tumour vein ligation. The prop-ratio was reduced significantly by approximately 40% and showed a significant negative correlation with APCI. BIS values increased significantly and showed a significant negative correlation with the prop-ratio. The increased APCI during tumour manipulation and after tumour vein ligation was associated with markedly reduced blood propofol concentrations. These results reveal that significant decreases in the anaesthetic effect may be observed in patients undergoing phaeochromocytoma surgery even if TCI anaesthesia is used with propofol.

The effect of sevoflurane on propofol with closed-loop target controlled infusion anesthesia system

Objective The primary goal was to determine the influence of sevoflurane on propofol with closed-loop target controlled infusion(TCI) delivery system in combined intravenous-inhalation anesthesia. Methods Sixty patients with ASA Ⅰ or Ⅱ were enrolled in this double-blinded study and randomly devided into three groups using the random number table method: group A, in which patients were only administrated propofol, group B and C, in which patients were given propofol for 20 min, followed with 0.6 MAC or 0.8 MAC sevoflurane for 40 min, respectively and the inhalation concentration was adjusted according to MAC. Serum propofol concentration was monitored continuouslyin. Results There was no difference in BIS among three groups (P>0.05). Serum concentration of propofol in group B and group C decreased constantly after the inhalation of sevoflurane but increased slowly when the inhalation was terminated(P<0.05), while it remained unchanged in group A. Compared with group A[(2.53±0.55), (2.54±0.61) mg/L], the decline of serum concentration was more evident in group C[(1.81±0.63), (1.24±0.4) mg/L] than group B[(1.92±0.58), (1.67±0.64) mg/L] at 30 min and 40 min during the surgery. The changing rate in group C was higher than that of group B and became stable 40 min after the stop point of propofol. Conclusions The administration of propofol with closed-loop anesthesia delivery system could adjust the anesthesia depth automatically and effectively, when the sevoflurane was inhaled with the MAC under 0.8. Key words: Sevoflurane; Propofol; Blood drug level; Closed-loop anesthesia delivery system

Propofol protects against opioid-induced hyperresponsiveness of airway smooth muscle in a horse model of target-controlled infusion anaesthesia

General anaesthesia in horses is associated with elevated mortality rate in subjects suffering of heaves. Target-controlled infusion (TCI) of sedative–hypnotic medications and opioids represents a total intravenous anaesthesia (TIVA) method validated in veterinary medicine. Since there are no data concerning the impact of these classes of drugs in inducing bronchial hyperresponsiveness (BHR) in horses, the aim of this study was to investigate the effect propofol and remifentanil on the contractile response of equine airway smooth muscle.The influence of propofol and remifentanil on the contractile response of equine isolated bronchi to electrical field stimulation (EFS) was assessed. The role of capsaicin-sensitive sensory nerves, inducible nitric oxide synthase (iNOS) and neurokinin 2 (NK2) receptor was also assessed. The interaction analysis was performed by Bliss Independence theory. Experiments were repeated in desensitized and passively sensitized airways.Remifentanil induced BHR in both non-sensitized and passively sensitized bronchi, (+56.33±8.01% and +99.10±14.52%, respectively; P<0.01 vs. control) and propofol significantly prevented this effect (P>0.05 vs. remifentanil). The inactivation of capsaicin-sensitive sensory nerves via desensitization and blocking NK2 receptor inhibited the BHR remifentanil-induced (P>0.05 vs. controls). The inhibition of iNOS reverted the protective effect of propofol on the BHR induced by remifentanil (non-sensitized: +47.11±7.70%; passively sensitized: +70.51±11.39%; P<0.05 vs. control). Propofol synergistically interacted (overall ≈40%) in preventing the remifentanil-induced BHR.Remifentanil induces BHR via stimulating capsaicin-sensitive sensory nerves that facilitate the cholinergic neurotransmission through the activation of NK2 receptor. The propofol/remifentanil combination may be safely administered in course of TCI–TIVA procedures also in heaves affected horses.

An Effective and Safe Sedation Technique Combining Target-Controlled Infusion Pump with Propofol, Intravenous Pentazocine, and Bispectral Index Monitoring for Peroral Double-Balloon Endoscopy

Background/Aims: Because peroral double-balloon endoscopy (DBE) is a time-consuming, painful procedure, sedation with analgesics, and/or anesthetics is generally required. The aim of this prospective study was to investigate the safety and efficacy of our sedation protocol for peroral DBE, which consisted of target-controlled infusion (TCI) anesthesia with propofol, an intravenous bolus of pentazocine, and bispectral index (BIS) monitoring. Methods: A total of 34 consecutive patients who underwent DBE by the oral approach were enrolled. Patients were primarily sedated with a continuous infusion of propofol and adjusted in accordance with the BIS levels. The bolus infusion of pentazocine was performed when the propofol infusion was insufficient. The primary outcome measure of this study was to ensure the safety and efficacy of this sedation technique. The secondary purpose was to identify the characteristics of the patient who required the bolus infusion of pentazocine. Results: Five patients (14.7%) required a reduction in the dose of propofol. However, no patient experienced any serious adverse events. All patients (100%) and 80.6% (25/31) of endoscopists answered that the sedation protocol was ‘excellent' or ‘enough' for peroral DBE. Eleven patients (32.3%) required a bolus injection of pentazocine. Age <60 years and a total procedure time of >70 min were significant risk-factors for pentazocine use. Conclusions: A combination of propofol via TCI pump, bolus injection of pentazocine as needed, and BIS monitoring was a safe and effective procedure for peroral DBE. Reasonable satisfaction indices were obtained from both patients and endoscopists. Pentazocine was required for young patients and in cases with longer procedure times.

Optimal effect-site concentration of remifentanil for minimizing cardiovascular changes caused by fiberoptic nasotracheal intubation.

BackgroundEndotracheal intubation induces clinically adverse cardiovascular changes. Various pharmacological strategies for controlling these responses have been suggested with opioids being widely administered. In this study, the optimal effect-site concentration (Ce) of remifentanil for minimizing hemodynamic responses to fiberoptic nasotracheal intubation was evaluated.MethodsThirty patients, aged 18-63 years, scheduled for elective surgery were included. Anesthesia was induced with a propofol and remifentanil infusion via target-controlled infusion (TCI). Remifentanil infusion was initiated at 3.0 ng/mL, and the response of each patient determined the Ce of remifentanil for the next patient by the Dixon up-and-down method at an interval of 0.5 ng/mL. Rocuronium was administered after propofol and remifentanil reached their preset Ce; 90 seconds later fiberoptic nasotracheal intubation was initiated. Non-invasive blood pressure and heart rate (HR) were measured at pre-induction, the time Ce was reached, immediately before and after intubation, and at 1 and 3 minutes after intubation. The up-and-down criteria comprised a 20% change in mean blood pressure and HR between just prior to intubation and 1 minute after intubation.ResultsThe median effective effect-site concentration (EC50) of remifentanil was 3.11 ± 0.38 ng/mL by the Dixon's up-and-down method. From the probit analysis, the EC50 of remifentanil was 3.43 ng/mL (95% confidence interval, 2.90-4.06 ng/mL). In PAVA, the EC50 and EC95 of remifentanil were 3.57 ng/mL (95% CI, 2.95-3.89) and 4.35 ng/mL (95% CI, 3.93-4.45). No remifentanil-related complications were observed.ConclusionsThe EC50 of remifentanil for minimizing the cardiovascular changes and side effects associated with fiberoptic nasotracheal intubation was 3.11-3.43 ng/mL during propofol TCI anesthesia with a Ce of 4 ug/mL.

Bispectral index for monitoring anesthetic depth in patients with severe burns receiving target-controlled infusion of remifentanil and propofol.

This study evaluated the feasibility and effectiveness of using the bispectral index (BIS) to monitor anesthetic depth in patients with severe burns receiving intravenous target-controlled infusion (TCI) of remifentanil and propofol. We randomly assigned 80 patients undergoing elective escharectomy (<1 week) to BIS (A) and control (B) groups. All patients received remifentanil and propofol as intravenous TCI anesthesia. Clinical data were recorded at different time points. The time from drug withdrawal to eye opening upon the patient hearing his/her name called and upon reaching an Aldrete score of 9 points was also recorded. During anesthesia maintenance, the target concentrations of remifentanil and propofol in group A were significantly lower than that in group B (2.12 ± 0.35 vs 2.50 ± 0.21 ng/mL and 2.54 ± 0.22 vs 2.86 ± 0.31 μg/mL, respectively; P < 0.01). The time from drug withdrawal to eye opening upon the patient hearing his/her name called and reaching an Aldrete score of 9 points in group A was considerably shorter than that in group B (7.90 ± 0.58 vs 8.35 ± 0.66 min and 9.15 ± 0.69 vs 11.13 ± 0.96 min, respectively; P < 0.01). In both groups, mean arterial pressure and heart rate values at each time point after loss of consciousness were significantly lower than the baseline values (P < 0.05), with the exception of 2 min after intubation. The use of BIS to monitor anesthetic depth in patients with severe burns receiving TCI of remifentanil and propofol during the perioperative period reduces propofol consumption and shortens the consciousness recovery time in patients.