Validation of haemodialysis recirculation and access blood flow measured by thermodilution.
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BACKGROUND: Recirculation (R) and access blood flow (Qac) measurements are considered useful indicators of adequate delivery of haemodialysis. It was the purpose of this study to compare measurements of R and Qac obtained by two different techniques which are based on the same principle of indicator dilution, but which differ because of the characteristics of the injection and detection of the different indicators used. METHODS: Recirculation measured by a thermal dilution technique using temperature sensors (BTM, Fresenius Medical Care) was compared with recirculation measured by a validated saline dilution technique using ultrasonic transducers placed on arterial and venous segments of the extracorporeal circulation (HDM, Transonic Systems, Inc.). Calculated access flows were compared by Bland Altman analysis. Data are given as mean +/- SD. RESULTS: A total of 104 measurements obtained in 52 treatments (17 patients, 18 accesses) were compared. Recirculation measured with correct placement of blood lines and corrected for the effect of cardiopulmonary recirculation using the 'double recirculation technique' was -0.02 +/- 0.14% by the BTM technique and not different from the 0% measured by the HDM technique. Recirculation measured with reversed placement of blood lines and corrected for the effect of cardiopulmonary recirculation was 19.66 +/- 10.77% measured by the BTM technique compared with 20.87 +/- 11.64% measured by the HDM technique. The difference between techniques was small (-1.21 +/- 2.44%) albeit significant. Access flow calculated from BTM recirculation was 1328 +/- 627 ml/min compared with 1390 +/- 657 ml/min calculated by the HDM technique. There was no bias between techniques. CONCLUSION: BTM thermodilution yields results which are consistent with the HDM ultrasound dilution technique with regard to both recirculation and access flow measurement. (+info)
Lens extraction with ultrasound. Experiments in rabbits.
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The extraction of the rabbit lens is described using a 25 G irrigating needle and a 22 G aspirating needle; at the latter's bevelled tip lens fragmentation occurs due to the longitudinal ultrasonic vibrations generated there--an 'acoustic horn' causes the tip to vibrate with large amplitudes. The use of small needles allows considerable manoeuvrability in the anterior chamber and usually eliminates the need for corneal suturing. Push-pull coupled syringes equate the volume of irrigation with that of aspiration. This procedure makes possible lens extraction through an aperture in the anterior capsule of the rabbit's lens and a similar machine is being constructed for trial on human cataract. (+info)
Stoichiometry of dipalmitoylphosphatidylcholine-DNA interaction in the presence of Ca2+: a temperature-scanning ultrasonic study.
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DNA-DPPC complexes can be prepared by means of a single step procedure of mixing DNA solution and aqueous lipid dispersion in the presence of calcium ions. Interaction between DPPC and DNA brings about a biphasic shape of melting curves corresponding to the free lipid and the strongly bound one. The amount of the strongly bound lipid is 5 molecules per nucleotide which is close to the size of the first lipid monolayer around DNA molecule. (+info)
Ultrasonography as an aid in the diagnosis and management of surgical diseases of the pelvis: special emphasis on the genitourinary system.
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Technological advances, particularly the advent of the gray scale technique, has greatly extended the application and usefulness of this modality to clinical diagnoses and surgery. The ultrasonic beam uniquely provides anatomical profiles in the transverse (cross-sectional) and sagittal (longitudinal) planes of the body. Intra-rectal and intra-vaginal ultrasonic probes have provided unique definition of both the normal and pathologic anatomy of the pelvic organs. The present report is drawn from a continuing experience with ultrasonography of the genitourinary system with an update of current technological advances. Ultrasonography has proven especially valuable in the following clinical applications: 1) Early diagnosis of cancer (especially of the prostate); 2) Accurate staging of cancer of the bladder and prostate; 3) Monitoring of the response of the pathologic process to therapy. (+info)
Airway hyperresponsiveness to ultrasonically nebulized distilled water in subjects with tetraplegia.
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The majority of otherwise healthy subjects with chronic cervical spinal cord injury (SCI) demonstrate airway hyperresponsiveness to aerosolized methacholine or histamine. The present study was performed to determine whether ultrasonically nebulized distilled water (UNDW) induces airway hyperresponsiveness and to further elucidate potential mechanisms in this population. Fifteen subjects with SCI, nine with tetraplegia (C4-7) and six with paraplegia (T9-L1), were initially exposed to UNDW for 30 s; spirometry was performed immediately and again 2 min after exposure. The challenge continued by progressively increasing exposure time until the forced expiratory volume in 1 s decreased 20% or more from baseline (PD20) or the maximal exposure time was reached. Five subjects responding to UNDW returned for a second challenge 30 min after inhalation of aerosolized ipratropium bromide (2.5 ml of a 0.6% solution). Eight of nine subjects with tetraplegia had significant bronchoconstrictor responses to UNDW (geometric mean PD20 = 7.76 +/- 7.67 ml), whereas none with paraplegia demonstrated a response (geometric mean PD20 = 24 ml). Five of the subjects with tetraplegia who initially responded to distilled water (geometric mean PD20 = 5.99 +/- 4.47 ml) were not responsive after pretreatment with ipratropium bromide (geometric mean PD20 = 24 ml). Findings that subjects with tetraplegia are hyperreactive to UNDW, a physicochemical agent, combined with previous observations of hyperreactivity to methacholine and histamine, suggest that overall airway hyperresponsiveness in these individuals is a nonspecific phenomenon similar to that observed in patients with asthma. The ability of ipratropium bromide to completely block UNDW-induced bronchoconstriction suggests that, in part, airway hyperresponsiveness in subjects with tetraplegia represents unopposed parasympathetic activity. (+info)
Stabilizing effect of an S-layer on liposomes towards thermal or mechanical stress.
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Isolated subunits of the crystalline cell surface layer (S-layer) protein of Bacillus stearothermophilus PV72/p2 were recrystallized on positively charged unilamellar liposomes. Liposomes were composed of dipalmitoylphosphatidylcholine (DPPC), cholesterol and hexadecylamine (HDA) in a molar ratio of 10:5:4 and they were prepared by the dehydration-rehydration method followed by an extrusion procedure. The S-layer protein to DPPC ratio was 5.7 nmol/micromol which approximately corresponds to the theoretical value estimated by using the areas occupied by the S-layer lattice and the lipid membrane. Coating of the positively charged liposomes with S-layer protein resulted in inversion of the zeta-potential from +29.1 mV to -27.1 mV. Covalent crosslinking of the recrystallized S-layer protein was achieved with glutaraldehyde. Chemical analysis revealed that almost all amino groups (>95%) from HDA in the liposomal membrane were involved in the reaction. To study the influence of an S-layer lattice on the stability of the liposomes, the hydrophilic marker carboxyfluoresceine (CF) was encapsulated and its release was determined for plain and S-layer-coated liposomes in the course of mechanical and thermal challenges. In comparison to plain liposomes, S-layer-coated liposomes released only half the amount of enclosed CF upon exposure to shear forces or ultrasonication as mechanical stress factors. Furthermore, temperature shifts from 25 degrees C to 55 degrees C and vice versa induced considerably less CF release from S-layer-coated than from plain liposomes. A similar stabilizing effect of the S-layer lattice was observed after glutaraldehyde treatment of plain and S-layer-coated liposomes. (+info)
Ultrasonic enhancement of antibiotic action on Escherichia coli biofilms: an in vivo model.
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Biofilm infections are a common complication of prosthetic devices in humans. Previous in vitro research has determined that low-frequency ultrasound combined with aminoglycoside antibiotics is an effective method of killing biofilms. We report the development of an in vivo model to determine if ultrasound enhances antibiotic action. Two 24-h-old Escherichia coli (ATCC 10798) biofilms grown on polyethylene disks were implanted subcutaneously on the backs of New Zealand White female rabbits, one on each side of the spine. Low-frequency (28.48-kHz) and low-power-density (100- and 300-mW/cm2) continuous ultrasound treatment was applied for 24 h with and without systemic administration of gentamicin. The disks were then removed, and the number of viable bacteria on each disk was determined. At the low ultrasonic power used in this study, exposure to ultrasound only (no gentamicin) caused no significant difference in bacterial viability. In the presence of antibiotic, there was a significant reduction due to 300-mW/cm2 ultrasound (P = 0.0485) but no significant reduction due to 100-mW/cm2 ultrasound. Tissue damage to the skin was noted at the 300-mW/cm2 treatment level. Further development of this technique has promise in treatment of clinical implant infections. (+info)
Effect of ultrasonically nebulized distilled water on airway epithelial cell swelling in guinea pigs.
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To investigate the pathogenesis of ultrasonically nebulized distilled water-induced airway narrowing, we studied the role of airway epithelial cells during a distilled water-inhalation challenge in an animal model of airway inflammation. Guinea pigs were divided into four groups: 1) a sham/saline (S/S) group: sham ozone followed by saline inhalation; 2) a sham/water (S/W) group: sham ozone followed by water inhalation; 3) an ozone/saline (O/S) group: ozone followed by saline inhalation; and 4) an ozone/water (O/W) group: ozone followed by water inhalation. After exposure to either 3.0 parts/million ozone or air at the same flow rate for 2 h, guinea pigs were anesthetized and tracheostomized, and then lung resistance (RL) was measured. For morphometric assessment, tissues were fixed with formaldehyde, stained with hematoxylin and eosin, and cut into transverse sections. Airway dimensions were either measured directly or calculated from the internal perimeter, the external perimeter, and airway wall area. There were no statistical differences in the values of RL before distilled water inhalation between the sham groups and the ozone groups. RL increased significantly after 10 min of distilled water inhalation in both the S/W group and the O/W group. In the S/W group, epithelial cells were swollen, and intercellular spaces were wider, resulting in significant increase in epithelial wall thickness, but there was no significant infiltration by inflammatory cells. In the O/S group, the epithelium showed infiltration by inflammatory cells without change in cell volume. In the O/W group, the epithelium showed both infiltration and a greater increase in epithelial wall thickness compared with the S/W group. These results suggest that airway epithelial cell swelling, induced by inhaled distilled water, increases with RL in guinea pigs and that this reaction may be accelerated by airway inflammation. (+info)