Effect of remifentanil on three effect-site concentrations of propofol and their relationship during electroencephalography at loss of response, at maximum alpha power, and at onset of burst suppression: a prospective randomized trial.

PURPOSE: The effect-site concentration (Ce) at loss of response (Ce-LOR) to propofol closely correlates both with Ce as electroencephalographic alpha power becomes highest (Ce-alpha) and with Ce at onset of burst suppression (BS) (Ce-OBS), when no opioids are administered. Co-administration of opioids dose-dependently decreases Ce-LOR. We investigated the influence of remifentanil on the relationship between these three Ces. METHODS: After receiving approval from our local ethical committee, with written informed consent, we enrolled 90 participants (ASA-PS I or II) who were scheduled for elective surgery. Participants were randomly assigned to three groups: constant remifentanil Ce 0 ng/ml (Remi_0); 1 ng/mL (Remi_1); and 2 ng/mL (Remi_2). We recorded both raw EEG and EEG-derived parameters on a computer. After reaching remifentanil equilibrium, we administered propofol using a target-controlled infusion pump such that propofol Ce increased to about 0.3 µg/mL/min. After determining Ce-LOR, we administered 0.6 mg/kg of rocuronium and started mask ventilation. The study protocol ended after observation of BS. RESULTS: Three participants were excluded. Ce-LOR in each group (Remi_0, Remi_1, Remi_2) was 2.00 ± 0.58 µg/mL, 1.43 ± 0.49 µg/mL, and 1.37 ± 0.42 µg/mL. Ce-alpha was 2.91 ± 0.63 µg/mL, 2.30 ± 0.41 µg/mL, and 2.12 ± 0.39 µg/mL. Ce-OBS was 3.80 ± 0.69 µg/mL, 3.25 ± 0.68 µg/mL, and 2.90 ± 0.57 µg/mL. In three other instances, Ce was decreased by remifentanil. Generalized linear model analysis revealed that remifentanil had no influence on the relationship between the three Ces. CONCLUSION: During propofol anesthesia, even low concentrations of remifentanil shifted concentration-related electroencephalographic changes.

An Ultrasound-Guided Lateral Approach for Proximal Sciatic Nerve Block: A Randomized Comparison With the Anterior Approach and a Cadaveric Evaluation.

BACKGROUND AND OBJECTIVES: The lateral and anterior approaches for proximal sciatic nerve (SN) block can be used in patients lying supine. We assume that the posterior femoral cutaneous nerve (PFCN) is simultaneously blocked more often via the lateral approach than via the anterior approach, given the proximity of these 2 nerves at the injection level. However, locating the SN is difficult when using the original landmark-based lateral approach. We have introduced ultrasound guidance to alleviate the technical difficulty of the lateral approach and tested the hypothesis that an ultrasound-guided lateral approach would achieve PFCN block more often than the ultrasound-guided anterior approach for SN block. METHODS: Forty consecutive patients undergoing knee surgery were randomly allocated to receive an SN block using an ultrasound-guided lateral or anterior approach. The primary outcome was the frequency of PFCN block 30 minutes after SN block. Secondary outcomes included the frequency of SN block, nerve depth, needle depth, and time taken to perform the block. We also assessed the spread of injectate by the lateral approach in 4 cadaveric legs. RESULTS: The frequency of PFCN block 30 minutes after SN block was higher with the lateral approach than with the anterior approach (60% vs 15%, P = 0.008). The frequency of SN block was comparable between the groups. Dye reached the PFCN in all cadaveric specimens. CONCLUSIONS: The ultrasound-guided lateral approach for proximal SN block can be performed as successfully as the anterior approach and provides PFCN block more often than the anterior approach. CLINICAL TRIAL REGISTRATION: This study was registered at UMIN Clinical Trials Registry, identifier UMIN000026748.

Bayesian estimation-based pedestrian tracking in microcells.

We consider a pedestrian tracking system where sensor nodes are placed only at specific points so that the monitoring region is divided into multiple smaller regions referred to as microcells. In the proposed pedestrian tracking system, sensor nodes composed of pairs of binary sensors can detect pedestrian arrival and departure events. In this paper, we focus on pedestrian tracking in microcells. First, we investigate actual pedestrian trajectories in a microcell on the basis of observations using video sequences, after which we prepare a pedestrian mobility model. Next, we propose a method for pedestrian tracking in microcells based on the developed pedestrian mobility model. In the proposed method, we extend the Bayesian estimation to account for time-series information to estimate the correspondence between pedestrian arrival and departure events. Through simulations, we show that the tracking success ratio of the proposed method is increased by 35.8% compared to a combinatorial optimization-based tracking method.