Woo Hyung Lee

Crystallization of Local Anesthetics When Mixed With Corticosteroid Solutions

Objective To evaluate at which pH level various local anesthetics precipitate, and to confirm which combination of corticosteroid and local anesthetic crystallizes. Methods Each of ropivacaine-HCl, bupivacaine-HCl, and lidocaine-HCl was mixed with 4 different concentrations of NaOH solutions. Also, each of the three local anesthetics was mixed with the same volume of 3 corticosteroid solutions (triamcinolone acetonide, dexamethasone sodium phosphate, and betamethasone sodium phosphate). Precipitation of the local anesthetics (or not) was observed, by the naked eye and by microscope. The pH of each solution and the size of the precipitated crystal were measured. Results Alkalinized with NaOH to a certain value of pH, local anesthetics precipitated (ropivacaine pH 6.9, bupivacaine pH 7.7, and lidocaine pH 12.9). Precipitation was observed as a cloudy appearance by the naked eye and as the aggregation of small particles (<10 µm) by microscope. The amount of particles and aggregation increased with increased pH. Mixed with betamethasone sodium phosphate, ropivacaine was precipitated in the form of numerous large crystals (>300 µm, pH 7.5). Ropivacaine with dexamethasone sodium phosphate also precipitated, but it was only observable by microscope (a few crystals of 10–100 µm, pH 7.0). Bupivacaine with betamethasone sodium phosphate formed precipitates of non-aggregated smaller particles (<10 µm, pH 7.7). Lidocaine mixed with corticosteroids did not precipitate. Conclusion Ropivacaine and bupivacaine can precipitate by alkalinization at a physiological pH, and therefore also produce crystals at a physiological pH when they are mixed with betamethasone sodium phosphate. Thus, the potential risk should be noted for their use in interventions, such as epidural steroid injections.

Robotic-assisted gait training combined with transcranial direct current stimulation in chronic stroke patients: A pilot double-blind, randomized controlled trial

BACKGROUND Although robotic-assisted gait training (RAGT) is becoming a standard method in stroke rehabilitation, its effect on chronic stroke patients is uncertain. OBJECTIVE This study aimed to investigate whether anodal transcranial direct current stimulation (tDCS) enhances the effect of RAGT on functional ambulation in chronic stroke patients. METHODS Chronic hemiplegic stroke patients with a Functional Ambulatory Category (FAC) score≤4 were randomly assigned to either the RAGT with anodal tDCS (Anodal) group the sham tDCS (Sham) group. The patients were provided with RAGT for 45 min after allocated tDCS on the leg motor cortex in the impaired hemisphere for 20 min every weekday for 2 weeks. The primary outcome measure was the FAC, and the secondary outcome measures included 10-m walking test, 6-min walking test, Berg Balance Scale, Fugl-Meyer assessment of the lower extremity, Medical Research Council Scale, and motor-evoked potential (MEP) parameters. They were evaluated before treatment (T0), immediately after treatment (T1), and 4 weeks after the end of treatment (T2). RESULTS Twenty-one patients were finally included. The percentage of participants who achieved improvement in the FAC score was greater in the Anodal group than in the Sham group, and the difference was significant at T2 (66.7% vs. 12.5%, p = 0.024). In secondary outcome measures, the Anodal group showed greater improvement in the 6-min walking test than the Sham group at T2 (56.49±38.87 vs. 23.59±17.00, p = 0.038). The changes in the MEP parameters were not significantly different between the two groups. CONCLUSION This pilot study suggested that anodal tDCS on the leg motor cortex in the impaired hemisphere may facilitate the effect of RAGT on functional ambulation in chronic stroke patients. Larger clinical trials will be needed to confirm the effect of RAGT combined with tDCS in chronic stroke patients based on the present study.

Computer-assisted detection of swallowing difficulty

To evaluate classification performance of a support vector machine (SVM) classifier for diagnosing swallowing difficulty based on the hyoid movement data attained from videofluoroscopic swallowing study, the hyoid kinematics during the swallowing of 2 mL of liquid barium solution were analyzed for 90 healthy volunteers and 116 dysphagic stroke patients. SVM was used to classify the kinematic results as normal or dysfunctional swallowing. Various kernel functions and kernel parameters were used for optimization. Features were selected to find an optimal feature subset and to minimize redundancy. Accuracy, sensitivity, specificity, and area under a receiving operating characteristic curve (AUC) were used to assess the discrimination performance. In 19 out of 26 features, mean comparison revealed a significant difference between healthy subjects and dysphagic patients. By reducing the number of features to 10, an AUC of 0.9269 could be reached. Common features showing the best classification in both kernel functions included forward maximum excursion time, upward maximum excursion time, maximum excursion length, upward maximum velocity time, upward maximum acceleration time, maximum acceleration, maximum acceleration time, and mean acceleration. SVM-based classification method with the use of kernel functions showed an outstanding (AUC of 0.9269) discrimination performance for either healthy or dysphagic hyoid movement during swallowing. We expect that this classification method will be useful as an adjunct diagnostic tool by providing automatic detection of swallowing dysfunction as well as a research tool providing deeper understanding of pathophysiology.

Characteristics of Early Oropharyngeal Dysphagia in Patients with Multiple System Atrophy

Background/Aims: Dysphagia, a symptom of multiple system atrophy (MSA), is a major clinical concern. In this study, we investigate the characteristics of early oropharyngeal dysphagia (OD) in patients with MSA, and the differences between MSA subtypes. Methods: Patients enrolled in the study had previously been diagnosed with MSA at the clinic of the Department of Neurology, and had been referred for a videofluoroscopic swallowing study (VFSS), between 2005 and 2014, to check for dysphagia. The clinical characteristics and VFSS findings were analyzed and compared between the MSA subtypes. Results: This study enrolled 59 patients with MSA (24 men; 31 with MSA-P, 21 with MSA-C, and 7 with MSA-PC). Dysphagia symptoms were mostly limited to aspiration symptoms (90.48%) in patients with MSA-C, while difficulty in swallowing, increased mealtime, and drooling were frequent in those with MSA-P. The most common VFSS finding amongst patients was vallecular residue (n = 53, 89.8%), followed by penetration/aspiration (n = 40, 67.8%), and coating of the pharyngeal wall (n = 39, 66.1%). Comparison analysis between subtypes showed that apraxia and vallecular residue were more frequent and severe in MSA-P than in MSA-C (p = 0.033 and p = 0.010, respectively). Conclusion: Understanding early OD characteristics in patients with MSA and the differences between MSA subtypes could be helpful in managing dysphagia in patients with MSA. Several dysphagia symptoms similar to those of Parkinson disease were frequently observed in MSA-P, but not in MSA-C. A follow-up study is needed to elucidate the natural course of OD in MSA patients and the difference between MSA subtypes.

Changes in Hyolaryngeal Movement During Swallowing in the Lateral Decubitus Posture

Objective To investigate the differences in hyolaryngeal kinematics at rest and during swallowing in the upright sitting (UP) and the lateral decubitus (LD) postures in healthy adults, and delineating any potential advantages of swallowing while in the LD posture. Methods Swallowing was videofluoroscopically evaluated in 20 healthy volunteers in UP and LD postures, based on the movements of hyoid bone, vocal folds, and the bolus head. Parameters included the Penetration-Aspiration Scale (PAS), horizontal and vertical displacement, horizontal and vertical initial position, horizontal and vertical peak position, time to peak position of the hyoid bone and vocal folds, and pharyngeal transit time (PTT). Results Nine participants were rated PAS 2 in the UP and 1 was rated PAS 2 in the LD (p=0.003) at least 1 out of 3 swallows each posture. The hyoid and vocal folds showed more anterior and superior peak and initial positions in the LD. In addition, swallowing resulted in greater vertical and smaller horizontal displacement of the hyoid in LD posture compared with UP. Time to peak position of the hyoid was shorter in LD. The maximal vertical and horizontal displacement of the vocal folds, and PTT were comparable between postures. Conclusion The results showed that the peak and initial positions of the hyoid and larynx and the pattern of hyoid movement varied significantly depending on the body postures. This study suggests that the LD posture was one of the safe feeding postures without any increased risk compared with UP posture.