Safety and Efficacy of the Baska Mask Versus Endotracheal Intubation in 64 Women Undergoing Elective Laparoscopic Gynecological Surgery Under General Anesthesia: A Prospective Single-Center Study.

BACKGROUND The Baska mask is a supraglottic airway device that has a continuous non-inflatable flexible cuff that mimics an airway, reducing the risk of overinflation and aspiration of gastric contents. This prospective study from a single center aimed to compare the safety and efficacy of the Baska mask vs endotracheal intubation (ET) in 64 women undergoing elective laparoscopic gynecological surgery in Trendelenburg position under general anesthesia. MATERIAL AND METHODS This was a prospective randomized study conducted on 64 adult female patients, 32 in each group, undergoing gynecologic surgery under general anesthesia. The study population was divided into 2 groups: the Baska group and the ET group. The respiratory and haemodynamic variables, the degree of gastric distension, and postoperative pharyngolaryngeal symptoms were compared between groups. RESULTS After 2 patients dropped out of the study, data from 62 patients were analyzed. The Baska group showed significantly shorter device insertion time (28.4±10.7 vs 46.6±19.8, P=0.001), a significantly lower oropharyngeal leak pressure at all studied time points, and a higher leak fraction at 1 min after the completion of pneumoperitoneum (5.6% vs 2.1%, P=0.031) compared to the ET group. Respiratory and haemodynamic variables, the gastric antrum size, and postoperative pharyngolaryngeal symptoms showed no significant difference. CONCLUSIONS This study supports the findings from previous studies in patients undergoing general surgery. The Baska mask was as effective as ET in ventilation during general anesthesia in women undergoing elective laparoscopic gynecological surgery. Respiratory and hemodynamic responses were similar to ET, and no complications were associated with the Baska mask in this study.

Effects of ramosetron orally disintegrating tablets on the prophylaxis of post-discharge nausea and/or vomiting in female patients undergoing day surgery under general anesthesia: a randomized controlled trial.

BACKGROUND: This study was performed to evaluate the effectiveness of ramosetron orally disintegrating tablets (ODTs) in preventing post-discharge nausea and/or vomiting (PDNV) in female patients following outpatient surgery under general anesthesia. METHODS: This multicenter randomized study included three South Korean tertiary hospitals. Before surgery, 138 patients were randomly allocated into two groups. In the ramosetron group, ramosetron ODT 0.1 mg was administered after discharge in the morning of postoperative days 1 and 2. Metoclopramide 10 mg was administered as a rescue antiemetic (capped at 30 mg per day). In the control group, patients were administered only metoclopramide 10 mg when nausea and/or vomiting occurred. The primary outcome was the incidence of nausea during 24 h after discharge. RESULTS: We found significant differences in the incidence (13% vs. 33%, P = 0.008) and severity (P = 0.011) of nausea between the ramosetron and the control groups during 24 h after discharge. In addition, the rate of rescue antiemetic (metoclopramide) administration during 24 h after discharge was lower in the ramosetron group (6%) than in the control group (18%) (P = 0.033). Patient satisfaction score was higher in the ramosetron group than in the control group (P < 0.001). CONCLUSION: Ramosetron ODT reduces the incidence and severity of postoperative nausea after discharge during the first 24 h and may be a valuable option for the prevention of PDNV in female patients after day surgery under general anesthesia. TRIAL REGISTRATION: ClinicalTrials.gov, NCT04297293 . Registered on 05 March 2020.

Core-Multishell-Structured Digital-Gradient Cathode Materials with Enhanced Mechanical and Electrochemical Durability.

Ni-rich cathode materials provide high energy density, but their structural and surface instability limits their cyclability and thermal stability. As one of the approaches to mitigate this problem, cathode materials comprising Ni-rich high-capacity core wrapped in Mn-rich multiple shells are produced successfully. In contrast to the conventional batch-type process for concentration-gradient materials, a digital-gradient cascade coprecipitation process described here achieves the improvements in productivity and quality consistency needed to move toward large-scale manufacturing. The core-multishell cathode materials produced in this manner not only have longer cycle life and improved rate performance compared to homogeneous Ni-rich cathode materials having the same overall composition, but also show remarkably enhanced thermal stability and low impedance growth characteristics. In a novel attempt to determine the correlation between the mechanical properties of the core-multishell cathode particles and their electrochemical cyclabilities, their breaking force and elasticity were successfully measured using a statistical approach, which indicates that a cathode particle with stable surface composition as well as high breaking force has improved capacity retention and durability. These results guide the realization of long life and high thermal stability in Ni-rich cathode materials through heterogeneous particle engineering.

Incidence of hemi-diaphragmatic paresis after ultrasound-guided intermediate cervical plexus block: a prospective observational study.

PURPOSE: An intermediate cervical plexus block (CPB) targets the posterior cervical space between the sternocleidomastoid muscle and the prevertebral fascia. The phrenic nerve descends obliquely on the surface of the anterior scalene muscle beneath the prevertebral fascia after originating from the C3-C5 ventral rami. Therefore, the phrenic nerve can be affected by a local anesthetic during an intermediate CPB, depending on the permeability characteristics of the prevertebral fascia. This study investigated whether an intermediate CPB affects the phrenic nerve, inducing hemidiaphragmatic paresis. METHODS: In this prospective observational study, 20 patients undergoing single-incision transaxillary robot-assisted right thyroidectomy were enrolled. The intermediate CPB (0.25% ropivacaine 0.2 ml/kg) was performed at the C4-5 intervertebral level carefully, without penetrating the prevertebral fascia, before the patient emerged from general anesthesia. Diaphragmatic motions of the block side were measured by M-mode ultrasonography at three time points: before anesthesia (baseline) and at 30 and 60 min after the intermediate CPB. Hemidiaphragmatic paresis was divided into three grades, depending on the percentage of diaphragm movement compared to the baseline: none (> 75%), partial paresis (25-75%), and complete paresis (< 25%). RESULTS: No patient showed any partial or complete ipsilateral hemidiaphragmatic paresis within 60 min after the intermediate CPB. CONCLUSION: Intermediate CPB using 0.2 ml/kg of 0.25% ropivacaine at the C4-5 intervertebral level did not cause ipsilateral hemidiaphragmatic paresis. This may imply that the effect of the intermediate CPB on the phrenic nerve is not significant.

Influence of electrocautery-induced electromagnetic interference on quantitative electroencephalographic monitoring of hypnosis during general anesthesia: comparison between the ADMS® and the BIS VISTATM.

BACKGROUND: Hypnosis monitors analyze small-amplitude electrical signals transmitted from the brain that could be exposed to the electromagnetic field that occurs around the body during electrocautery (ECT). We investigated the influence of ECT on hypnosis monitoring during anesthesia. METHODS: We simultaneously monitored BIS and uCON during 50 gynecologic oncology surgeries. During the episodes of ECT, we compared the absolute difference (a-Diff) between the baseline index and the most deviated index after ECT over either 30-60 s (ECT30-60) or more than 60 s (ECT > 60) between the monitors. We also investigated the bias and the limits of agreement between the monitors. RESULTS: Between the two monitors, the a-Diff of ECT30-60 was 1.4 ± 1.1 for the BIS, which was significantly greater than 0.6 ± 0.9 for the uCON (P = 0.003), and the a-Diff of ECT > 60 was 16.5 ± 8.2 for the BIS, which was also significantly greater than 1.4 ± 1.3 for uCON (P < 0.001). The intra-monitor index differences showed that the BIS during ECT > 60 was significantly greater than that during ECT30-60 (P < 0.001), but the uCON showed no significant difference between ECT30-60 and ECT > 60 (P = 0.056). The estimated bias between the monitors was 6.3 ± 9.8 and 95% limits agreement was -12.3 to 25.0. CONCLUSIONS: Prolonged ECT intervention might lead to spurious estimations of quantitative EEG indexes. Therefore, hypnosis should be clinically assessed in combination with scrutinized judgment of relevant clinical symptoms and signs for hypnosis.

CAD/CAM for scalable nanomanufacturing: A network-based system for hybrid 3D printing.

Micro- and nano-structuring have been highlighted over several decades in both science and engineering fields. In addition to continuous efforts in fabrication techniques, investigations in scalable nanomanufacturing have been pursued to achieve reduced feature size, fewer constraints in terms of materials and dimensional complexity, as well as improved process throughput. In this study, based on recent micro-/nanoscale fabrication processes, characteristics and key requirements for computer-aided design and manufacturing (CAD/CAM) systems for scalable nanomanufacturing were investigated. Requirements include a process knowledge database, standardized processing, active communication, adaptive interpolation, a consistent coordinate system, and management of peripheral devices. For scalable nanomanufacturing, it is important to consider the flexibility and expandability of each process, because hybrid and bridging processes represent effective ways to expand process capabilities. As an example, we describe a novel CAD/CAM system for hybrid three-dimensional (3D) printing at the nanoscale. This novel hybrid process was developed by bridging aerodynamically focused nanoparticle printing, focused ion beam milling, micromachining, and spin-coating processes. The system developed can print a full 3D structure using various inorganic materials, with a minimum process scale of 50 nm. The most obvious difference versus CAD/CAM at 'conventional' scales is that our system was developed based on a network to promote communication between users and process operators. With the network-based system, it is also possible to narrow the gap among different processes/resources. We anticipate that this approach can contribute to the development of CAD/CAM for scalable nanomanufacturing and a wide range of hybrid processes.

Correction of target-controlled infusion following wrong selection of emulsion concentrations of propofol.

BACKGROUND: We investigated the correction methods following wrong-settings of emulsion concentrations of propofol as a countermeasure against erroneous target-controlled infusions (TCI). METHODS: TCIs were started with targeting 4.0 µg/ml of effect-site concentration (Ceff) of propofol, and the emulsion concentrations were selected for 2.0% instead of 1.0% (FALSE1-2, n = 24), or 1.0% instead of 2.0% (FALSE2-1, n = 24). These wrong TCIs were corrected at 3 min after infusion start. During FALSE1-2, the deficit was filled up while injecting after equilibrium (n = 12), or while overriding (n = 12). During FALSE2-1, the overdose was evacuated while targeting Ceff (n = 12) or targeting plasma concentration (Cp) (n = 12). The gravimetrical measurements of TCI reproduced the Cp and Ceff using simulations. The reproduced Ceff at 3 min (Ceff-3min) and the time to be normalized within ± 5% of target Ceff (T±5%), were compared between the correction methods. RESULTS: During the wrong TCI, Ceff-3min was 1.98 ± 0.01 µg/ml in FALSE1-2, and 7.99 ± 0.05 µg/ml in FALSE2-1. In FALSE1-2, T±5% was significantly shorter when corrected while overriding (3.9 ± 0.25 min), than corrected after equilibrium (6.9 ± 0.05 min) (P < 0.001). In FALSE2-1, T±5% was significantly shorter during targeting Cp (3.6 ± 0.04 min) than targeting Ceff (6.7 ± 0.15 min) (P < 0.001). CONCLUSIONS: The correction methods, based on the pharmacokinetic and pharmacodynamic characteristics, could effectively and rapidly normalize the wrong TCI following erroneously selections of the emulsion concentration of propofol.

Arrangements of the intravenous parallel infusions with anti-reflux valves decreasing occlusion alarm delay.

BACKGROUND: The methods of arrangement of combined intravenous parallel infusions using anti-reflux valve (ARV), with and without anti-syphon valve (ASV) that could decrease occlusion alarm delay were investigated. METHODS: Occlusion challenge tests were mainly performed as bench experiments of four kinds of multiple parallel infusions (10 ml/h and 50 ml/h infusions), which were connected at the proximal or distal portion of ARV, with or without ASV. Alarm threshold was set to 1000 mmHg. Occlusion alarm delays and the compliances of the infusion systems were compared among groups. RESULTS: Without ASV, compared to 10 ml/h infusion alone distal to anti-reflux valve, 50 ml/h infusion distal to anti-reflux valve reduced the mean alarm delay from 416 ± 7 s to 81 ± 3 s (P < 0.001). Compared to 50 ml/h infusion alone, combined 10 ml/h and 50 ml/h infusion distal to ARV prolonged the alarm delay from 81 ± 3 s to 133 ± 6 s (P < 0.001). However, combined infusions distal to ARV with ASV significantly reduced the alarm delay from 133 ± 6 s to 74 ± 5 s (P < 0.001), and also reduced the compliance of the infusion system from 2.31 ± 0.12 to 1.20 ± 0.08 µl/mmHg (P < 0.001). CONCLUSIONS: The infusion setup of faster infusion rate, lower compliant system using ASV could effectively decrease occlusion alarm delay during multiple intravenous parallel infusions using ARV.

Impact of priming the infusion system on the performance of target-controlled infusion of remifentanil.

BACKGROUND: The start-up behavior of syringe and syringe pump is known to be one of the causes of inaccurate intravenous infusion. This study evaluated the method of priming the infusion system (PRIMING), and its impact on the target-controlled infusion (TCI) of two remifentanil diluents. METHODS: PRIMING was performed using an evacuation of 2.0 ml to the atmosphere prior to TCI. Forty-eight TCI, using 50 µg/ml (Remi50) or 20 µg/ml (Remi20) of diluents, were performed targeting 4.0 ng/ml of effect-site concentration (Ceff), with PRIMING or not. The gravimetrical measurements of the delivered infusates reproduced actual Ceff. The bolus amount and time to reach 95% target were compared. RESULTS: Without PRIMING, Remi50 infused less bolus (43 ± 23 %) than Remi20 (19 ± 9 %) (P = 0.003), and showed more delayed increase of Ceff (11.2 ± 4.0 min) than Remi20 (7.4 ± 0.4 min) (P = 0.028). However, PRIMING significantly decreased the deficit of the bolus (2 ± 1%), as well as the delay of the increase of Ceff in Remi50 (1.2 ± 0.2 min) (both P < 0.001). In addition, with PRIMING, the start-up bolus showed minimal difference to the nominal bolus (1 and 2%), and Ceff were increased to 4.0 ± 0.1 ng/ml at the expected time of peak effect, irrespective of the diluents. CONCLUSIONS: Proper operation of the syringe pump used in the priming of the syringe may be helpful in reduction of the inaccuracy of TCI, particularly during the early phase of infusion, or the infusion of a more concentrated diluent.

False selection of syringe-brand compatibility and the method of correction during target-controlled infusion of propofol.

BACKGROUND: We evaluated volumetric differences of syringe brand compatibilities, and investigated the impact of false brand settings on target-controlled infusion (TCI) and their methods of correction. METHODS: Gravimetric measurement of 10 ml bolus infusions was performed using BD Plastipak (BDP) and Terumo compatible syringes, while setting to 7 different kinds of brand compatibilities (BDP, Sherwood Monoject, BD Perfusion, Braun Perfusor, Braun Omnifix, Fresenius Injectomat, and Terumo). To investigate the performance of TCI using BDP with a false setting to Terumo (BDPTERUMO) and Terumo to BDP (TERUMOBDP), 24 TCI targeting 4.0 µg/ml of effect-site concentration (Ceff) of propofol were performed. Subsequently, another 24 TCI were evaluated for simple corrections of false settings at 30 min. We also investigated 24 TCI using active corrections (fill-up for BDPTERUMO, evacuation for TERUMOBDP) based on the pharmacokinetics of propofol. The Ceff at 30 min of TCI and time to normalize to ± 5% of target concentration (T±5%target) were compared. RESULTS: The Ceff of BDPTERUMO showed negative bias and 17.2% inaccuracy, and the Ceff of TERUMOBDP showed positive bias and 19.5% inaccuracy. The Ceff at 30 min showed no difference between the methods of correction in BDPTERUMO or TERUMOBDP. The T±5%target in both the active corrections was significantly shorter than that of each simple corrections (P < 0.001). CONCLUSIONS: False brand setting of syringe proportionally maintained different predicted concentrations as much as the volumetric differences of syringe brand. Based on the results, it is proposed that correction methods based on pharmacokinetics could effectively normalize the differences, without giving up the wrong TCI.

The efficacy of the time-scheduled decremental continuous infusion of fentanyl for postoperative patient-controlled analgesia after total intravenous anesthesia.

BACKGROUND: Intravenous fentanyl has been used for acute postoperative pain management, but has not always provided reliable adequate analgesia, including patient-controlled analgesia (PCA). The purpose of this study was to investigate the efficacy of time-scheduled decremental infusion of fentanyl for postoperative analgesia. METHODS: Ninety-nine patients, aged 20-65 years, undergoing laparoscopic-assisted hysterectomy using total intravenous anesthesia (TIVA) were randomly assigned into one of the three groups. Their background infusions of fentanyl diluent (2 ml/hr of diluent was equivalent with 0.5 µg/kg/hr of fentanyl) with PCA were maintained at the fixed-rate of 2 ml/hr until the postoperative 24 hr (FX2-2-2), or at the decremental rates of 6.0, 4.0, 2.0 ml/hr (D6-4-2) and 8.0, 4.0, 2.0 ml/hr (D8-4-2). The visual analogue score (VAS), incidence of inadequate analgesia, frequency of PCA intervention, and side effects were evaluated. RESULTS: VAS was significantly higher in FX2-2-2 than in D6-4-2 and D8-4-2 until postoperative 3 hr (P < 0.05). After postoperative 4 hr, VAS was significantly higher in FX2-2-2 than D8-4-2 (P < 0.05). The incidence of inadequate analgesia of FX2-2-2 was significantly greater than D6-4-2 (P = 0.038) and D8-4-2 (P < 0.001) until postoperative 1 hr. None of the patients had ventilatory depression, and postoperative nausea and vomiting were not significant among the groups. CONCLUSIONS: The time-scheduled decremental background infusion regimens of fentanyl, based on the pharmacokinetic model, could provide more effective postoperative pain management after TIVA, and the side effects and the risk for morbidity were not different from the fixed-rate infusion regimen.

A target-controlled infusion regimen for reducing remifentanil-induced coughs.

BACKGROUND: This study evaluates the effectiveness of the target-controlled infusion (TCI) of remifentanil through stepwise increases in the effect-site concentration (C(eff)) in preventing coughs. METHODS: In a preliminary study, we randomly selected 140 patients to receive remifentanil through two-step increases in C(eff) (1.0 ng/ml to 4.0 ng/ml: Group R(1-4); 2.0 ng/ml to 4.0 ng/ml: Group R(2-4)). Based on the results of the preliminary study, we employed another sample of 140 patients and implemented a three-step increase in TCI (1.0 ng/ml to 2.0 ng/ml to 4.0 ng/ml: Group R(1-2-4)). We then compared this treatment with direct targeting based on 4.0 ng/ml TCI (Group R(4)). We recorded the episodes of coughs, rating them as mild (1-2), moderate (3-4), or severe (5 or more). RESULTS: In Group R(1-4), one patient (1.5%) coughed during the first step, and five (7.3%) coughed during the second step. In Group R(2-4), nine (13.2%) coughed during the first step, but none coughed during the next step. Only one patient had a mild cough during the three-step increase in TCI, that is, patients in Group R(1-2-4) were significantly less likely to cough than those in Group R(4) (P < 0.001). CONCLUSIONS: Stepwise increases in the TCI of remifentanil reduced the incidence of remifentanil-induced coughing, and the three-step increase in TCI nearly eliminated remifentanil-induced coughing.

Cross-simulation between two pharmacokinetic models for the target-controlled infusion of propofol.

BACKGROUND: We investigated how one pharmacokinetic (PK) model differed in prediction of plasma (C(p)) and effect-site concentration (C(eff)) using a reproducing simulation of target-controlled infusion (TCI) with another PK model of propofol. METHODS: Sixty female patients were randomly assigned to TCI using Marsh PK (Group M) and TCI using Schnider PK (Group S) targeting 6.0 µg/ml of C(p) of propofol for induction of anesthesia, and loss of responsiveness (LOR) was evaluated. Total and separate cross-simulation were investigated using the 2 hr TCI data (Marsh TCI and Schnider TCI), and we investigated the reproduced predicted concentrations (MARSH(SCH) and SCHNIDER(MAR)) using the other model. The correlation of the difference with covariates, and the influence of the PK parameters on the difference of prediction were investigated. RESULTS: Group M had a shorter time to LOR compared to Group S (P < 0.001), but C(eff) at LOR was not different between groups. Reproduced simulations showed different time courses of C(p). MARSH(SCH) predicted a higher concentration during the early phase, whereas SCHNIDER(MAR) was maintained at a higher concentration. Volume and clearance of the central compartment were relevant to the difference of prediction, respectively. Body weight correlated well with differences in prediction between models (R(sqr) = 0.9821, P < 0.001). CONCLUSIONS: We compared two PK models to determine the different infusion behaviors during TCI, which resulted from the different parameter sets for each PK model.

Comparison of the effects of sevoflurane and propofol on core body temperature during laparoscopic abdominal surgery.

BACKGROUND: A decrease in core body temperature caused by heat distribution depends on the anesthetic agent used. The purpose of this study is to investigate the effects of sevoflurane and propofol on core temperature during laparoscopic major abdominal surgery requiring pneumoperitoneum of more than 90 min. METHODS: Fifty adult patients undergoing laparoscopic major abdominal surgery were randomly assigned to either a sevoflurane group (n = 25) or a propofol group (n = 25). In the sevoflurane group, anesthesia was induced with propofol 2 mg/kg, remifentanil 1.0 µg/kg, and maintained with 0.8-2.0 vol% sevoflurane and 0.1-0.2 µg/kg/min remifentanil. In the propofol group, anesthesia was induced with the effect-site concentration of propofol of 5.0 µg/ml and remifentanil 4 ng/ml, and maintained with the effect-site concentration of propofol of 2-3.5 µg/ml and remifentanil 3-5 ng/ml. Core body temperature was measured with an esophageal stethoscope with a temperature sensor after the start of the pneumoperitoneum (baseline) and at 15-min intervals until completion of surgery. RESULTS: During the study period, core temperature was comparable between the two groups. When compared with baseline values, core temperatures in both groups were significantly decreased 45 min after pneumoperitoneum. CONCLUSIONS: This study demonstrated that in patients undergoing prolonged laparoscopic surgery, a decrease in core body temperature during sevoflurane-remifentanil anesthesia was not different than propofol-remifentanil anesthesia, and the incidence of hypothermia of the two groups did not differ.

Comparison of effect-site concentration of remifentanil for tracheal intubation with the lightwand and laryngoscopy during propofol target-controlled infusion.

BACKGROUND: Target-controlled infusion (TCI) of propofol and remifentanil can provide satisfactory intubating conditions without a neuromuscular blocking agent. We compared the effect-site concentration of remifentanil required for intubation with the lightwand and the Macintosh laryngoscope during propofol TCI without a neuromuscular blocking agent in adult patients. METHODS: Forty-nine patients were randomly assigned to the lightwand group (n = 25) or the direct laryngoscope group (n = 24). Anesthesia was induced by propofol TCI with an effect-site concentration of 5.4 µg/ml. Two minutes after start of propofol TCI, remifentanil was administered at the predetermined effect-site concentration. The effect-site concentration of remifentanil was determined using Dixon's up-and-down method (0.5 ng/ml as a step size). The first patient in each group was tested at 4.5 ng/ml of remifentanil. Tracheal intubation was performed 2 min after the start of remifentanil TCI. Acceptable intubation was defined as an excellent or good intubating conditions. RESULTS: Using a modified Dixon's up and down method, the EC50 ± SD of remifentanil in the lightwand and laryngoscope groups was 4.75 ± 0.71 ng/ml and 5.08 ± 0.52 ng/ml, respectively; there was no statistically significant difference between the groups (P = 0.373). CONCLUSIONS: The effect-site concentration of remifentanil for acceptable intubation with the lightwand and Macintosh laryngoscope in 50% of adults did not differ during propofol TCI without a neuromuscular blocking agent.

Prevalence of human papillomavirus infection and genotype distribution among high-risk Korean women for prospecting the strategy of vaccine development.

We investigated the prevalence of human papillomavirus (HPV) infection and the distribution of high-risk HPV genotypes among 2,308 high-risk Korean women to predict how much the current prophylactic HPV vaccines might affect the prevention of cervical cancer in Korea. HPV DNA was detected in 939 women (40.7%) but only one-third of women were positive for HPV-16 and/or HPV-18, the genotypes used for developing the HPV vaccines. Thus, the development of area-specific HPV vaccines based on dominant HPV genotypes in our country is needed for preventing HPV infection and the development of premalignant lesions in the cervix of Korean women.

Titration of the plasma effect site equilibrium rate constant of propofol; a link method of 'Concentration-Probability-Time'.

BACKGROUND: The plasma effect-site equilibrium rate constant (k(e0)) of propofol has been reported in various pharmacodynamic studies; however, it is not desirable to apply k(e0) for the link with pharmacokinetic models that were separately investigated. Thus, we titrated k(e0) for the pharmacokinetic model, which is known as the multiple covariates adjusted model of propofol. METHODS: Ninety female patients scheduled for gynecologic surgery were randomly assigned to three groups targeting different plasma concentrations of 5.4, 8.1, and 10.8 microg/ml. Target-controlled infusions (TCI) were provided by a computer-assisted continuous infusion system. Time to loss of responsiveness (LOR) was measured by a blind investigator; effect-site concentrations (C(e)) for LOR were then calculated with simulation of TCI using different k(e0)s. We determined the k(e0) minimizing total discrepancy (TD) between the inputted and calculated k(e0) from the t(1/2)k(e0)s for a given probability of LOR of the C(e), and also obtained the k(e0) for the minimal TD between the median C(e), which were compared to the known k(e0). RESULTS: K(e0)s from these two methods were 0.3692 and 0.3788/min. C(e)s for LOR with these k(e0)s were significantly different from those with Schnider's k(e0). CONCLUSIONS: We proposed a method for titration of the k(e0) of propofol. The k(e0)s of propofol was lower than Schnider's k(e0). An adequate k(e0) for the specific pharmacokinetic model and a certain population would be useful for prediction of an accurate C(e), and could be used for calculation of accurate dosing during targeting of the effect site.