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Biomedical subjects

A Rappe

Publications and source records attributed to A Rappe.

At least 19 recordsLinked to original sources
PubMed2001

Effect of Guglielmi detachable coil placement on intraaneurysmal pressure: experimental study in canines.

BACKGROUND AND PURPOSE: Treatment of ruptured aneurysms with Guglielmi detachable coils (GDCs) has been shown to prevent repeat bleeding. To assess whether GDC coiling alters aneurysmal pressure, we measured intraaneurysmal pressure in two canine types of carotid artery aneurysms before and after GDC placement. METHODS: A 0.014-inch guidewire with a pressure transducer was inserted into parent arteries and domes of surgically created aneurysms. Intravascular static pressures were recorded before and during saline power injections (10, 20, and 30 mL over 1 and 2 s), before and after GDC placement. Common femoral arterial pressure was monitored. RESULTS: Saline power injections reproducibly and abruptly increased pressure in parent arteries and aneurysms. Mean intraaneurysmal pressure varied (18 +/- 4 [10 mL] to 75 +/- 15 mm Hg [30 mL]), independent of injection duration. Intraaneurysmal baseline pressures were higher after GDC placement (111 +/- 10 versus 93 +/- 15 mm Hg; P =.05). Aneurysmal pressure increases with saline injections were slightly higher after GDC placement, which dampened intraaneurysmal pressure amplitude at baseline (26.5 +/- 5.6 versus 19.6 +/- 7.4 mm Hg; P =.003) and during hypertension (25.3 +/- 5.4 versus 19.8 +/- 7.5 mm Hg, P =.002). The pressure increase slope with saline injection was delayed with GDC placement (0.24 +/- 0.1 versus 0.38 +/- 0.19 s; P <.001). CONCLUSION: Graded saline power injections into parent arteries can rapidly increase intraaneurysmal pressure. GDC treatment did not attenuate mean intraaneurysmal pressures, but both dampened the pressure amplitude and delayed pressure increases during locally induced hypertension.

Aneurysm↗
PubMed1997

Collagen-coated acrylic microspheres for embolotherapy: in vivo and in vitro characteristics.

PURPOSE: To evaluate the in vivo and in vitro properties of collagen-coated acrylic microspheres and to compare them with polyvinyl alcohol (PVA) particles. METHODS: Samples of 100- to 300-microns, 300- to 500-microns, 500- to 700-microns, and 700- to 900-microns collagen-coated acrylic microspheres and 200- to 300-microns PVA particles were suspended in solutions of 50% saline and 50% contrast material. The samples were evaluated for quantitative and qualitative microscopic characteristics (shape, size, deformability); injectability via standardized microcatheters; degree of particulate penetration in the pig rete mirabile; and reaction of tissue to the particles in 48-hour- and 4-week-old specimens. RESULTS: The acrylic microspheres were spherical and deformable. The sample of 100- to 300-microns microspheres (n = 202) had a mean diameter of 210 microns (standard deviation, 43 microns). Hub accumulation, particle aggregation, and catheter occlusion were not observed with the microspheres (all sizes) but were noted with the PVA particles. The 200- to 300-microns PVA particles formed aggregates in the proximal rete. The 100- to 300-microns microspheres were found throughout the rete and beyond. Chronic transmural and perivascular inflammation was observed with the microspheres and the PVA particles. CONCLUSIONS: Particle aggregation and catheter occlusion do not complicate the transcatheter delivery of collagen-coated acrylic microspheres as they do with PVA particles. For a given particle and vessel size, acrylic microspheres penetrate to a much greater extent than the PVA particles. Tissue reaction to acrylic microspheres and PVA particles is similar.

Acrylic Resins↗
PubMed1997

Intraarterial thrombolysis in a pig model: a preliminary note.

PURPOSE: To develop a pig model of arterial thrombosis suitable for assessing different methods of thrombolysis and to use this model to compare the efficacy of intraarterial thrombolysis performed by continuous proximal urokinase infusion versus mechanical clot disruption combined with intrathrombic urokinase injection. METHODS: In a control group of five pigs, a thrombus was made in a short segment of femoral artery and observed for 2 hours to assess its stability. In a treatment group of six pigs, intraarterial thrombolysis was performed immediately after thrombus formation. Thrombolysis was accomplished by continuously infusing urokinase into the proximal leading edge of the thrombus in three pigs and by mechanical clot disruption combined with intrathrombic urokinase injection in the remaining three pigs. RESULTS: There was no spontaneous reestablishment of flow in the control group during the 2-hour observation period. In the first treatment group, no flow was observed after a 1-hour treatment period when urokinase was infused continuously into the proximal edge of the thrombus. In the second treatment group, with mechanical clot disruption and intrathrombic urokinase injection, some degree of flow was observed in all three pigs. Reestablishment of flow was more sustained and of a greater degree with the addition of systemic heparinization. CONCLUSION: This animal model could provide a useful way to evaluate and compare different methods of thrombolysis. Our results suggest that mechanical clot disruption combined with intrathrombic urokinase injection is more effective in achieving reestablishment of flow than is continuous infusion of urokinase into the proximal edge of the thrombus.

Animals↗
PubMed1986

Field triage for on-scene helicopter transport.

This prospective study evaluated the use of basic vital signs, two mechanisms of injury, and time-distance factors as field triage criteria for on-scene helicopter transport of 130 patients to a trauma center serving a rural area. The vital signs criteria included any one or more of the following: level of consciousness (LOC) less than or equal to unresponsive to verbal stimulation; respiration rate (RR) less than or equal to 10 or greater than or equal to 30; systolic blood pressure (BP) less than or equal to 90; pulse (P) less than or equal to 60 or greater than or equal to 120. The flight crew recorded vital signs taken by the first responder capable of basic assessment. Entrapment and associated fatalities in motor vehicular accidents were recorded and flight logistics were examined. The presence of one or more abnormal signs identified a group of seriously injured trauma patients (mean Injury Severity Score = 29.1) with 24% mortality compared to a predicted mortality of 32% (p less than 0.02). Unresponsiveness to verbal stimulation in the field was the single most predictive criterion, yielding sensitivity of 93% and specificity of 85%. Time-distance criteria were helpful to determine helicopter use.

Adolescent↗
PubMedDate not supplied

Flow dynamics of lateral carotid artery aneurysms and their effects on coils and balloons: an experimental study in dogs.

PURPOSE: To investigate the hemodynamic characteristics of lateral carotid artery aneurysms in a canine model and to determine their influence on coils and balloons. MATERIALS AND METHODS: Forty aneurysms were created in fourteen dogs and their hemodynamic characteristics and influence on coils and balloons were evaluated with angiography and color Doppler pre- and postplacement. Twenty aneurysms were treated with coils, eight with balloons, and 12 aneurysms served as controls. RESULTS: The aneurysms demonstrated three distinct zones of flow: 1) an inflow zone entering at the distal aspect of the aneurysm ostium, 2) an outflow zone exiting at the proximal ostium, and 3) a central slow flow vortex. The inflow zone is a determining factor in the placement and stability of coils and balloons placed within the aneurysm and in the thrombosis of an aneurysm. The force of the inflow is considerable and can alter the shape of coils and displace both coils and balloons positioned within the aneurysm. CONCLUSIONS: Coils and balloons need to be of shapes and sizes that do not conform to the inflow and outflow zones. Filling the aneurysm and blocking or displacing the inflow zone can produce thrombosis of an aneurysm with preservation of the parent artery.

Angioplasty, Balloon↗
PubMedDate not supplied

Aneurysm hemodynamics: an experimental study.

PURPOSE: To study the flow of blood in aneurysms. METHODS: A canine model was used to study the hemodynamics of lateral, bifurcation, and terminal aneurysms with angiography and color Doppler techniques. FINDINGS: Flow within experimental aneurysms, although not laminar, is seldom if ever turbulent, but rather is highly predictable, varying primarily according to the relationship of the aneurysm to its parent artery. CONCLUSIONS: These studies support earlier in vitro work and provide further evidence that not all aneurysms share similar stresses. A more complete understanding of these hemodynamic features will be useful in the establishment of criteria that allow recognition of those aneurysms that are more or less likely to rupture, to grow, or to thrombose.

Aneurysm↗
PubMedDate not supplied

Glioblastoma multiforme: MR imaging at 1.5 and 9.4 T after injection of polylysine-DTPA-Gd in rats.

Polylysine-DTPA-Gd, a new MR contrast agent, was injected into the aorta of rats 7 days after C6 glioblastoma was implanted in their brains; MR imaging was performed 3 days later. The imaging was done at two field strengths: (1) 1.5 T with a 3-mm slice thickness and in-plane resolutions of 600 microns and (2) 9.4 T with a 125- or 500-microns slice thickness and in-plane resolutions of 95 microns. In animals injected with polylysine-DTPA-Gd (1 microgram or more per rat), the T1-weighted images and mixed T1, T2 images of the C6 glioblastoma revealed a higher signal intensity at the marginal region between tumor and normal brain than that seen in surrounding normal brain. The central tumor region had a low signal intensity. The concentration of Gd in the C6 glioblastoma, after injection of 1 microgram polylysine-DTPA-Gd per rat, was calculated to be 0.14 mumol/l. The central tumor region also had a low signal intensity in animals that were not injected with the contrast agent, but the margin between tumor and normal brain was resolved poorly, if at all. The polylysine-DTPA-Gd revealed the microvasculature of the C6 glioblastoma in the 125-micron-thick slices obtained at 9.4 T. This is the first study to reveal the utility of the 9.4-T MR imager for examination of glioblastomas in situ and to demonstrate the utility of polylysine-DTPA-Gd as a contrast agent for the definition of the margin between glioblastoma and normal brain tissue.

Animals↗
PubMedDate not supplied

Glutaraldehyde cross-linked collagen (GAX): a new material for therapeutic embolization.

In a search for a better agent for use in therapeutic embolization, a newly available bovine collagen product, glutaraldehyde cross-linked collagen (GAX), was evaluated to determine its effectiveness in causing arterial obstruction, its persistence after embolization, and the acute and chronic pulmonary toxicity resulting from direct pulmonary embolization. GAX is an effective agent for causing arterial obstruction: 3-4 ml caused prompt flow arrest when injected into the internal iliac artery of six dogs. In this canine model, the material persisted within embolized tissue for as long as 2 months, and at follow-up intervals of 2 days, 2 weeks, and 2 months, its presence did not produce any cellular response. Studies of both acute and chronic pulmonary toxicity reveal that when GAX is embolized directly into the pulmonary circulation it causes adverse effects only by mechanical blockage of pulmonary arteries. GAX offers several advantages over other currently available agents and is of sufficient safety that clinical trials in humans can be undertaken.

Animals↗