Lower-extremity peripheral nerve blockade: essentials of our current understanding.
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Humans↗
Biomedical subjects
Vincent Chan
Publications and source records attributed to Vincent Chan.
Ultrasound imaging of peripheral nerves: a need for a new trend.
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Humans↗
Objective assessment of manual skills and proficiency in performing epidural anesthesia--video-assisted validation.
BACKGROUND AND OBJECTIVES: Demand is growing for objective assessment of manual skills and competencies of invasive procedures. The aim of this study was to validate an objective tool for assessing residents' skill in performing epidural anesthesia by use of a global assessment scale and a 3-scale, 27-stage checklist. We wish to demonstrate that this tool can differentiate operators with different levels of training. METHODS: Second-year anesthesia residents were recruited. Their previous experience was assessed by questionnaire. They were repeatedly videotaped performing epidural anesthesia over a 6-month period. Videotaping was done in a blinded manner that masked the identity and level of training of the residents. Three blinded, independent examiners evaluated each session by use of a specifically devised assessment tool that consisted of a global rating scale and a 3-scale, 27-stage checklist to judge the skill level and grade the videotaped sessions. RESULTS: Twenty-one sessions by 6 residents were videotaped over 6 months. Interrater reliability for the different checklist and global-rating form items shows moderate to high degree of agreement for most stages. Total scores demonstrate almost perfect agreement (kappa/ICC +/- SE = 0.90 +/- 0.03 and 0.83 +/- 0.13, respectively; P < .0001) between examiners. To test whether higher total scores are associated with greater experience, a series of repeated-measures ANCOVAs were performed. In both the global-rating form and the checklist, a significant relation between total scores and epidurals done was found to exist (checklist: P < .0001; global rating: P < .0001). CONCLUSIONS: The results of our study show that scores on a system that consists of a global-rating form and a task-specific checklist had a significant relation to the number of epidural insertions performed (i.e., experience). The interrater reliability of these assessment tools was very strong. Evaluation of technical skills by an objective tool under direct observation, as opposed to laboratory setting, may create a more reliable standard of assessment. Furthermore, residency programs could use these evaluations to identify deficiencies in teaching programs and trainees who require extra instruction.
Analysis of Variance↗
The sensitivity of motor response to nerve stimulation and paresthesia for nerve localization as evaluated by ultrasound.
BACKGROUND AND OBJECTIVE: Seeking paresthesia and obtaining a motor response to an electrical stimulus are the two most common methods of nerve localization for the performance of peripheral-nerve blocks. However, these two endpoints do not always correlate, and the actual sensitivity and specificity of either method remains unknown. The objective of this study is to determine the sensitivity of paresthesia and motor response to electrical nerve stimulation as tools for nerve localization when a 22-gauge insulated needle is used for the performance of axillary-nerve block. METHODS: After IRB approval and informed consent, 103 patients were enrolled. Real-time ultrasonography was used as the reference test. After needle-to-nerve contact was confirmed by ultrasonography, the patient was requested to report the presence of paresthesia, and a nerve stimulator was used to seek a motor response, with a stimulating current of 0.5 mA or less. RESULTS: One patient was excluded from analysis because of protocol violation. Paresthesia was found to be 38.2% sensitive and motor response was 74.5% sensitive for detection of needle-to-nerve contact. CONCLUSION: The very different and relatively low sensitivity of either technique may explain, in part, the lack of correlation previously reported between the 2 endpoints.
Adult↗
Interaction of liposome with immobilized chitosan during main phase transition.
It has been recently demonstrated that chitosan in aqueous solution alters the phase behavior and structure of a phospholipid bilayer (Fang, N.; et al. Biomacromolecules 2001, 2, 1161-1168). Until now, the physical driving forces between chitosan and the phospholipid bilayer upon their initial encounter remains unknown. In this study, confocal reflectance interference contrast microscopy (C-RICM), phase contrast microscopy and bioadhesion modeling are concurrently applied to probe the interaction of phospholipid vesicle with immobilized chitosan at various temperatures, pH, and osmotic stress. First, the successful immobilization of chitosan on amino-silanized glass is indicated by the increases in both the degree of vesicle deformation and adhesion energy of vesicles adhering on chitosan modified substrate in comparison with those on amino-silanized glass. Second, the phase transition of a phospholipid bilayer does not modulate the adhesion strength at the chitosan-biomembrane interface at pH 7.4. With increase of the degree of protonation on the chitsoan backbone at pH 4, the adhesion energy is increased by 5-fold for vesicles of all sizes compared to that in pH 7.4. Furthermore, pH reduction amplifies the thermal-induced response of larger vesicles on the immobilized chitosan layer. Interestingly, a moderate increase of osmotic stress maximizes the degree of vesicle deformation and adhesion energy at 23 degrees C and dampens the effect of phase transition on vesicle adhesion. Overall, this study demonstrates the quantitation of chitosan-biomembrane interactions that will be critical for future applications of chitosan in biological systems.
Chitin↗
Chitosan-induced restructuration of a mica-supported phospholipid bilayer: an atomic force microscopy study.
Chitosan has emerged as a promising material for biomedical applications. However, the effect of chitosan adsorption on the structure of model biomembrane is not known. In this study, atomic force microscopy (AFM) is employed to investigate the interaction between chitosan and mica-supported dipalmitoylphosphocholine (DPPC) bilayer. First, in situ AFM measurement indicates that nucleation of chitosan occurs around the membrane defects at the initial stage of chitosan incubation. Eventually, DPPC-chitosan binding and chitosan intermolecular association lead to chitosan aggregation on the membrane surface which is quantified by average height measurement and RMS roughness analysis. Lateral force microscopy (LFM) confirms that the adsorbed chitosan has distinct material properties. Furthermore, the trend of surface pressure-area isotherms supports the condensation of DPPC monolayer induced by chitosan in the aqueous subphase. Surface coverage and surface roughness analysis show that the extent of chitosan aggregation on the supported membrane is affected by the incubation time during long-term chitosan incubation.
1,2-Dipalmitoylphosphatidylcholine↗