Dynamic Detection of Spinal Cord Position During Postural Changes Using Near-Infrared Reflectometry.

INTRODUCTION: Motion of the spinal cord relative to a spinal cord stimulator epidural electrode array can cause suboptimal stimulation: either noxious, inefficient, or insufficient. Adaptive stimulation attempts to mitigate these effects by modulating stimulation parameters in a position-dependent fashion. Near-infrared (NIR) reflectometry is demonstrated to provide real-time direct measurement of spinal cord position at the site of stimulation, which can facilitate closed-loop adaptive stimulation during static and dynamic motion states. METHODS: A miniature sensor array consisting of an NIR light emitting diode flanked by phototransistors potted in epoxy was placed in the dorsal epidural space of a human cadaver at the T8 level via laminotomy. Turgor of the subarachnoid space was maintained by intrathecal infusion of saline. NIR reflectance was measured as the cadaver was rotated about its longitudinal axis on a gantry. NIR reflectance was correlated with gantry position and velocity. RESULTS: NIR reflectometry suggests gravitational force is the primary determinant of cord position in static, ordinal positions. Under dynamic motion conditions, there was statistically significant cross-correlation between reflectometry data and the tangential velocity squared, suggesting that centripetal force was the primary determinant of cord position as the gantry was rotated. Reflectometry data strongly correlated with a simple geometric model of anticipated spinal cord precession within the spinal canal. CONCLUSIONS: Spinal cord position during dynamic motion has been shown to differ from static predictions due to additional influences such as centripetal force. These findings underscore limitations in extrapolating spinal cord position from surrogates such as body position or body acceleration at sites remote from the stimulating electrodes. NIR reflectometry offers a real-time direct measure of spinal cord position in both static and dynamic motion states, which may facilitate closed-loop adaptive stimulation applications.

Exit-site care in Austrian peritoneal dialysis centers -- a nationwide survey.

BACKGROUND: Catheter-associated infections markedly contribute to treatment failure in peritoneal dialysis (PD) patients. There is much controversy surrounding prophylactic strategies to prevent these infections. METHODS: In this nationwide multicenter study we analyzed strategies to prevent catheter-associated infections as performed in Austrian PD centers in 2006. A questionnaire was sent to all 23 PD centers in Austria. RESULTS: Ten different catheter models were used in the 332 patients being treated in the 23 Austrian PD centers. Systemic antibiotics prior to catheter placement were given by 17 of the 23 PD centers (glycopeptides, n = 7; cephalosporins, n = 10). Nasal swabs were taken preoperatively by 17 PD centers; nasal Staphylococcus aureus carriers were treated prophylactically with mupirocin cream in 15 of these centers. Dressing change was routinely performed in 318 of 332 chronic PD patients (nonocclusive film dressing, n = 58; gauze dressing, n = 260). Disinfectants for chronic exit-site care included povidone iodine (n = 155), sodium hypochlorite (n = 31), povidone iodine + sodium hypochlorite together (n = 102), and octenidine dihydrochloride/phenoxyethanol (n = 17). Water + non-disinfectant soap or 0.9% sodium chloride was administered as a cleansing agent to the exit site by 27 patients. Routine S. aureus screening (nasal and/or exit-site swabs) in chronic PD patients was performed in 12 PD centers; carriers were treated with mupirocin cream in 11 of these centers. Dialysis staff members were screened for S. aureus in 8 PD centers and spouses were screened for S. aureus in 5 PD centers. The overall exit-site infection rate was 1 episode/43.9 patient-months, tunnel infection rate was 1 episode/88.9 patient-months, and peritonitis rate was 1 episode/51.0 patient-months. Patients of centers that have installed a prophylaxis protocol for treating S. aureus carriers had lower mean infection rates compared with those not using such a protocol. CONCLUSION: Various individual prophylactic strategies are used to prevent catheter-associated infections in Austrian PD centers. Infection rates are within the range reported in the literature. There is still scope for improvement in some centers (e.g., by establishing a prophylaxis protocol).

Role of basic fibroblast growth factor in the course of cerebral vasospasm in an experimental model of subarachnoid hemorrhage.

The goal of this study was to investigate the relationship between basic fibroblast growth factor (bFGF) and the course of cerebral vasospasm after subarachnoid hemorrhage (SAH), using an immunohistochemical method. Female Sprague-Dawley rats were sacrificed by perfusion fixation 10 min, 6 h, 1, 2, 3, 4, 7 or 14 days after a single intracisternal injection of fresh autologous arterial blood. Morphometric analysis of lumen cross-sectional areas of blood vessels were determined by computerized image analysis. Results were expressed as percent lumen patency, defined as the ratio of the area of vessel patency in SAH rats to the area of patency in control rats. An immunohistochemical analysis against bFGF was performed using the avidin-biotin-peroxidase technique. The immuno-reactivity of bFGF was observed with the aid of a light microscope and semiquantitatively graded. Basilar arterial spasm was greatest 10 min after SAH (mean decrease: 67.1% of the control values; p < 0.001). Subsequently, there was a significant degree of spasm of the artery for three days after SAH, followed by full recovery at day 4. A slight increase in immunoreactivity was observed in the intima only at 10 min and one day after SAH. In the media, immunoreactivity showed a biphasic pattern; a significant increase in immunoreactivity was observed at 10 min that persisted for two days after SAH. At three days after SAH, immunoreactivity in the media returned to the control level, but then gradually increased significantly to reach a maximum at 14 days after SAH while the vascular dimensions were normal. Immunohistochemical analysis failed to show a direct relationship between bFGF and the course of cerebral vasospasm in this rat single-hemorrhage model. However, the late phase upregulation of bFGF might lead to the vascular angiopathy, fibrosis or hyperplasia during the chronic stage of SAH.

Diode laser wavelength modulated spectroscopy of I(2) at 675 nm.

A free-running diode laser has been used to examine the spectrum of 127I(2) near 675 nm using wavelength modulation spectroscopy. Twelve transitions have been observed in the region between 14818.0 and 14819.3 cm(-1), all of which are accounted for by previously published constants. Changes in quadrupole coupling constants, DeltaeQq, have been determined for all lines. Pressure broadening and shift coefficients have been determined for two unblended lines for broadening by air, argon, and water vapor.

A New Method for Collecting Ultrafiltrate Samples from Sheep, Using Microdialysis Catheters.

A system is described that facilitates collection of ultrafiltrate samples from implanted catheters. Sheep are particularly tolerant of this system, and sample recovery rates approaching 84% may be achieved.

Oropharyngeal pH monitoring for the detection of liquid and aerosolized supraesophageal gastric reflux.

The association between gastroesophageal reflux disease (GERD) and extraesophageal symptoms is poorly understood and difficult to document. pH monitoring in this group of patients has resulted in conflicting data due to lack of diagnostic sensitivity. Recently, a new sensitive pH device for detection of liquid and aerosolized droplets in the oropharynx (The Dx-pH Measurement System [Dx-pH]) has become available. Our hypothesis is that we will be able to improve our ability to identify and understand this group of patients with this device. The aim of this preliminary observation study was to compare the results of this new device to the standard esophageal and pharyngeal pH probes in a small group of patients with extraesophageal symptoms. Patients with suspected extraesophageal GER symptoms underwent traditional 24-hour esophago-pharyngeal pH monitoring (24pH) simultaneous with Dx-pH monitoring in the oropharynx. Tracings were reviewed for comparison and correlation between the two probes, with an event in the Dx-pH Probe being defined as a rapid drop >3 standard deviation from baseline. Fifteen patients (10 females, 5 males) with mean age of 57.5 years (range, 25-75) were studied. The predominant chief complaint included 12/15 chronic cough, 2/15 asthma; and 1/15 throat clearing. All Dx-pH events were preceded and associated with distal esophageal pH drops in a progressive ante grade manner. Ten patients had 1-13 abnormal oropharyngeal pH events as measured by Dx-pH monitoring with a total of 48 events. The median pH of reflux events had a statistically significant increase from 3.1 at the distal esophageal probe to 5.2 at the pharynx and 5.6 at the oropharynx, the latter being 80% higher than the distal esophageal probe (P<0.001). The percentage of acid events decreased in a cephalad manner from 66.7% at distal esophagus to 25% at the pharynx and only 6.25% at the oropharyngeal Dx-pH Probe, with the remaining events being weakly acidic. Dx-pH Probe is a new sensitive oropharyngeal pH device whose values correlate well with the gold-standard 24-hour pH device, and appears to accurately detect pH events that begin at the distal esophagus and travel upward to the oropharynx. This device suggests that supraesophageal events manifest themselves as rapid pH drops (>10%), which are likely not to be identified using the standard criteria of pH <4 due to the gradient of increasing pH from the lower esophagus to the oropharynx.