RESUMO
PURPOSE: To test whether an electromagnetic guidance system such as CathTrack would allow long-term central venous access devices to be reliably placed at a decreased cost and without radiation exposure to patients and staff. The following study was undertaken to verify accuracy of the CathTrack system for catheter placement and to develop guidelines for its use. METHODS: Twenty-nine consecutive patients were prospectively enrolled in the study and taken to the operating room for implantation of a permanent central venous access port. By protocol, the CathTrack system was used to guide initial catheter positioning using the center of the third intercostal space along the right sternal border as the desired external target. Fluoroscopy was then used to visualize tip position and relocate the catheter tip to the exact position desired by the surgeon. RESULTS: Catheter placement using the CathTrack system was successfully accomplished in 27 out of 29 patients. In two instances CathTrack was abandoned and fluoroscopy utilized because of difficulty in threading the initial guidewire into the superior vena cava. CONCLUSION: The CathTrack electromagnetic locator system can be used to reliably position catheters for the establishment of long-term central venous access. Decreased cost and elimination of radiation exposure are distinct advantages of this system over fluoroscopy.
RESUMO
The long-term effects of partial deafferentation in the neocortex of adult rats were studied in four-month old rats in which the corpus callosum had been completely sectioned when they were one-month old. Quantitative light microscopy was used to identify morphological changes in the auditory cortex resulting from the loss of established callosal connections. Particular attention was directed at those cortical layers known to receive the heaviest callosal projection (layers II and III) and at neurons known to be postsynaptic to callosal afferents (layer V pyramidal neurons). The comparative analysis of both semithin plastic sections and Golgi-impregnated material from long-term, callosally-lesioned rats and age-matched control animals reveals no differences in the overall cortical thickness, the thickness of cortical layers, the numbers of neurons or the density of spines along apical dendrites of layer V pyramidal neurons. However, as a result of the callosal lesion, large diameter apical dendrites are significantly thinner in the callosally deafferented cortex and there is a small increase in the number of neuroglial cells in the deeper cortical layers. To determine whether another system of afferents to the auditory cortex spreads into the deafferented callosal domain, geniculate lesions were made in long-term, callosally-lesioned animals and age-matched controls. The terminal projection patterns of thalamic afferents were compared using the Fink-Heimer technique and quantitative electron microscopy. Normally in the auditory cortex there is only a small region of overlap between the terminal projection fields of callosal afferents and thalamic afferents, the latter projecting chiefly to layer IV and low layer III. However, three months after callosal lesions, thalamic axons had proliferated superficially into part of the callosal domain. Furthermore, in the normal auditory cortex after geniculate lesions, there were three rostrocaudally oriented bands of relatively dense thalamocortical terminal degeneration separated by regions of less dense degeneration. In the doubly lesioned animals these bands of degeneration were less distinct due to a proliferation of thalamic axons into the regions characterized by sparse projections.
