Improvements in high resolution ultrasound for postoperative investigation of capillary microperfusion after free tissue transfer.

INTRODUCTION: High resolution ultrasound (US) techniques as implemented in the latest generation of US machines provide imminently better resolution compared to previous high resolution models. This improvement is based on advanced transducer technologies as well as updated post-processing procedures. Furthermore, matrix linear transducers providing frequencies from 6 to 15 MHz are now available. The aim of the study was the evaluation of these new techniques for the immediate postoperative investigation of microcirculation after free tissue transfer by supplemental use of Contrast-Enhanced Ultrasound Imaging (CEUS). PATIENTS AND METHODS: To this end, we investigated 12 patients who underwent free tissue transfer in order to cover tissue defects in various body regions. We utilized the new GE Logiq E9 equipped with a linear 6-9 MHz and a matrix 6-15 MHz probe as well as the GE Logiq 9 with the previous version of the linear 6-9 MHz probe. Both machines provide the modalities of SRI, Cross Beam and THI. The perfusion curves were quantitatively analyzed using digital cine sequences (Qontrast, Bracco, Italy). Furthermore, two independent investigators evaluated the digitally recorded images with respect to the resolution of details based on a scale ranging from 0 to 5, and after application of 2.4 ml SonoVue (Bracco, Italy), evaluated the image quality regarding the representation of tissue perfusion. RESULTS: None of the free flaps showed clinical or laboratory signs of flap failure during the hospital stay. Several flaps showed typical perfusion patterns relating to the flap type. The combination of SRI, Cross Beam and THI allows, in most cases, a more exact differentiation of tissue graft outlines and tissue composition, in particular the tissue texture, compared to the use of B-scan only. In addition, the high resolution matrix technology combined with the broader spectrum of 6-15 MHz considerably improves the representation of image details compared to multifrequency probes with 6-9 MHz. The use of updated post-processing procedures as well as new transducer technologies in CEUS also results in improved resolution and thus achieves a higher score compared to previous models. CONCLUSION: At present, these new US technologies combined with the updated 6-9 MHz probe provide the optimal assessment of perfusion in cutaneous, subcutaneous and deeper tissue layers. The additional use of new multifrequency 6-15 MHz matrix probes improves the resolution in the B-mode to an even higher degree.

Teaching antiarrhythmic therapy and ECG in simulator-based interdisciplinary undergraduate medical education.

BACKGROUND: Third-year students in the Dresden Medical School Programme undergo a 6 week course 'Basics of Drug Therapy' in a problem-based learning curriculum. As part of this course a practical seminar about antiarrhythmic drugs and ECG was set up. This study was conducted to evaluate the use of a simulator in this course. METHODS: A total of 234 students were randomly allocated to receive instructions with (Group S) or without (Group C [control]) the use of a simulator. After a lecture on antiarrhythmic drugs, arrhythmias were presented to Group S using an advanced life support (ALS) manikin. The students were asked to administer a drug or to defibrillate, and the outcome was shown on the monitor. The students in Group C were presented with ECG charts without a simulator. The course was evaluated by a questionnaire and multiple-choice questions (MCQ) about arrhythmias. RESULTS: We received 222 questionnaires. The content-time ratio was rated almost perfect in both groups, but the students in Group S rated the course better suited to link theory and practice. Students in Group S considered the simulator helpful and a good tool for teaching, and the extra effort to be worthwhile. A significantly higher number of students in Group S preferred electric cardioversion as therapy for ventricular tachycardia. CONCLUSIONS: An ALS manikin can be an effective tool in teaching clinical pharmacology.

Reduction in patient timing errors using a breath-activated metered dose inhaler.

Delivery of aerosol medication to the lower respiratory tract by metered dose inhaler (MDI) is often limited by the patient's inability to properly coordinate activation of the device with inspiration. This study evaluated a new breath-activated MDI device, designed to minimize patient timing errors by sensing inspiratory flow and automatically activating to deliver aerosol medication. Twenty novice adult volunteers, previously naive to the technique of MDI use, and 20 patients currently using MDIs were tested in their ability to coordinate MDI usage. Simultaneous recording of respiratory events and device activation allowed analysis of timing errors. With a conventional MDI, a 31.0 percent incidence of errors was seen in the novice group and a 21.5 percent incidence of errors was seen in the experienced group. These compared with error rates using the breath-activated MDI of 6.5 percent and 5.0 percent in the two groups respectively (p = 0.009, p = 0.04). The breath-activated inhaler was preferred by 35 of 40 subjects. In conclusion, MDI technique timing errors were significantly less with this breath-activated MDI device in both novice and experienced subjects, and it was also preferred by both groups.

Endoscopic surgery training: application of an in vitro trainer and in vivo swine model.

The development of endoscopic surgical procedures is changing general surgery, with many operations such as cholecystectomy, appendectomy, and hernia repair being performed using laparoscopic surgical techniques. Training and credentialing of surgeons are key issues for the safe and ethical introduction of these new procedures. This article reviews techniques employed at our institution for laparoscopic surgical training and certification including didactic instruction, an in-vitro model for learning instrumentation and hand-eye coordination, and in-vivo training using the porcine animal model.

MR imaging of Ho:YAG laser diskectomy with histologic correlation.

Twelve cadaveric vertebral specimens were imaged after holmium yttrium aluminum garnet (Ho:YAG) laser diskectomy to determine the usefulness of magnetic resonance (MR) imaging in evaluating treatment outcome. The Ho:YAG laser was operated at 1.0-2.0 J per pulse, 5 Hz, and 250-microseconds pulse width. The total energy varied between 600 and 2,700 J. Two distinct patterns emerged on MR images. Tissue ablation at higher power (1.5 and 2.0 J per pulse) produced discrete signal voids that correlated with areas of laser-induced ablation identified at gross inspection. More subtle changes, characterized by a high-signal-intensity ring, were seen in the specimens lased at 1.0 J per pulse. The latter appearance corresponded to incomplete vaporization of diskal tissue, a broader zone of minimal thermal injury, and sparing of adjacent vertebral endplates. Total mass loss did not appear to be affected by the choice of power setting (1.0 vs 1.5 J per pulse), with total laser energy held constant.

Argon laser-welded bovine heterograft anastomoses.

UNLABELLED: This study evaluated the strength of laser-welded arteriovenous shunts established using St. Jude BioPolyMeric vascular grafts. The arterial anastomoses of the biological graft were laser welded with and without the addition of soluble collagen or fibrin sealant. In four dogs, 16 arteriovenous grafts were implanted between the femoral artery and vein or the carotid artery and jugular vein using a 6 cm long, 4 mm internal diameter prosthesis. The 16 arterial anastomoses were evenly divided into four groups: sutured control, laser welded (LW), LW with soluble collagen applied immediately before and during welding, and LW with fibrin sealant applied after welding. All arterial control and venous anastomoses were sutured using continuous 6-0 polypropylene suture. All LW anastomoses were initially divided into six 5 mm long segments using six evenly spaced 6-0 polypropylene stay sutures. Each segment was laser welded using 15 to 18 5-sec pulses of the 0.5 W (7.5 W/cm 2) argon laser energy delivered via a 300 mum fiber while cooling the tissue with slow-drip saline irrigation. Blood flow was established and maintained through each anastomosis for 1 h. The vessels were then controlled, and anastomotic bursting pressure was determined with infusion of heparinized blood. RESULTS: An additional hemostatic suture was required in 3 LW anastomoses (2 LW, 1 LW with collagen). Mean bursting pressures (mm Hg) of the arterial anastomoses were as follows: sutured controls 165 +/- 159, LW 144 +/- 58, LW and collagen 93 +/- 47, LW and fibrin sealant 181 +/- 45.(ABSTRACT TRUNCATED AT 250 WORDS)

Three-dimensional transrectal ultrasound: preliminary patient evaluation.

Transrectal ultrasound is uniquely useful in diagnosing and localizing the extent of lower colon and rectal disease. This paper reports the preliminary evaluation of three-dimensional intraluminal ultrasound imaging of normal and diseased rectal segments. The three-dimensional reconstructions were produced using a computerized PC based image analysis system which aligns ultrasound images to produce the three-dimensional images. A unique perspective for displaying both normal and pathologic anatomy is achieved using this new technology and the method has promising diagnostic and therapeutic potentials.

Three-dimensional intravascular ultrasound imaging of normal and diseased canine and human arteries.

This study reports three-dimensional reconstruction of two-dimensional intravascular ultrasound images obtained along 5 cm vessel segments. Each three-dimensional image was produced by computerized "stacking" of a set of consecutive two-dimensional images (mode 90 images per set; range 32 to 256). Three-dimensional images (n = 26) were obtained from 11 human normal and atherosclerotic arteries (three in vitro and eight in vivo) and five in vivo canine studies. In vivo human examinations included three iliac, one deep, and three superficial femoral arteries and one aortic dissection. Five in vivo canine vessels (three iliac stenoses and two aortic dissections) were imaged before and after intraluminal stent deployment. Images were displayed on a gray-scale monitor, allowing examination of vessel images as complete cylinders or longitudinal hemisections in any user-defined plane. This enabled global examination of vascular segments and identified luminal shape, wall thickness, and distribution and morphology of plaques. Reconstructions of aortic dissections illustrated the extent of the dissection and produced an anatomic picture of the false lumen. Three-dimensional imaging enhanced stent deployment by identifying the site for deployment, dimensions of the vessel lumen, and changes in morphology after stent insertion. There was good correlation in vessel dimensions measured by angiography, two-dimensional intravascular ultrasonography and longitudinal gray-scale reconstructions (r = 0.74 to 0.95; p = 0.34 to 0.001) but poor correlation with measurements from three-dimensional surface-rendered images (r = 0.13 to 0.48; p = 0.42 to 0.87). We conclude that three-dimensional intravascular ultrasound imaging is an innovative new method for identifying the type, extent, and spatial configuration of arterial disease, with promising diagnostic and therapeutic applications.

Morphology and distribution of nicotinamide adenine dinucleotide phosphate (reduced form) diaphorase reactive neurons in human brainstem.

Nicotinamide adenine dinucleotide phosphate diaphorase reactive neurons were found in several regions of human brainstem. Three major groups were located in the medulla: a dorsomedial group in the central gray and floor of the fourth ventricle, a ventromedial group in the vicinity of the medullary raphe, and a lateral group in the lateral reticular nucleus. In the upper pons a large cluster of reactive neurons was centered in the nucleus centralis oralis extending into the locus coeruleus and dorsal tegmental region. A second cluster in the lateral parabrachial nucleus merged with this group more rostrally and continued into the midbrain tegmentum (paracoeruleus-cuneiform group). Nicotinamide adenine dinucleotide phosphate diaphorase neurons in this region often contained acetylcholinesterase activity. A second midbrain group was seen in the nucleus paranigralis. Aside from these discrete neuronal collections, scattered reactive neurons were found in the medullary reticular formation, periaqueductal gray, inferior colliculus and superior colliculus. Nicotinamide adenine dinucleotide phosphate diaphorase neurons were classified into three groups based on somal size. Parvocellular neurons (10-20 micron) were primarily found in the ventromedial medulla and lateral parabrachial nucleus. Intermediate neurons (20-25 micron) were located in the paranigralis nucleus and dorsomedial medulla. Magnocellular neurons (25-35 micron) were characteristically found in the lateral reticular nucleus and paracoeruleus-cuneiform region. Nicotinamide adenine dinucleotide phosphate diaphorase reactive neurons are present in substantial numbers in human brainstem and their distribution is complex. They represent the caudal end of a widespread network of nicotinamide adenine dinucleotide phosphate diaphorase-enriched neurons that extend rostrally from the brainstem reticular formation into the basal forebrain, striatum, and cerebral cortex.

Changes in lung glycosaminoglycans during postresectional lung growth.

We studied changes in glycosaminoglycan content and concentration during postresectional compensatory lung growth in adult male rats. After right trilobectomy, left lung dry weight was normal at 4 days, increased 74% between 4 and 7 days, and more slowly over the next week. Total glycosaminoglycan content per milligram dry lung weight increased early and rapidly, reaching 189% of the control value at 4 days postresection. The magnitude and temporal pattern of increase was different for different glycosaminoglycan subtypes. Hyaluronate and chondroitin sulfate content were increased by 198 and 113%, respectively, at 4 days, with no further increases subsequently. Heparan sulfate content increased more slowly and steadily, and dermatan sulfate concentrations did not change. At 4 days, the percent of total glycosaminoglycans that was hyaluronate was almost doubled, whereas the percent that was heparan sulfate was decreased; by day 7 the percent compositions had returned to normal. We conclude that changes in glycosaminoglycans occur early in postresectional lung growth and speculate that they may play a facilitatory role.