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Dennis W Ashley

Publications and source records attributed to Dennis W Ashley.

12 recordsLinked to original sources
PubMed2006

Accelerated migration and proliferation of smooth muscle cells cultured from neointima induced by a vena cava filter.

Formation of a neointima is associated with grafted artery or vein, angioplasty, and stent and inferior vena cava filter (IVCF) implantation. Contributing to the neointima is a population of vascular smooth muscle cells (SMC) that migrates from media and subsequently proliferates within intima. The purpose of this present study was to culture SMC from normal vessel wall and from neointima and to compare migration and growth of these cells. Neointima was stimulated in the vena cava of pigs by placement of an IVCF for 30 days. Tissue was taken from the thickened wall between the struts and from a normal segment of the IVCF. After removal of the endothelium and adventitia, explants were placed in culture dishes and were observed for the migration of cells. Immunoassay for smooth muscle alpha-actin was used to identify cell origin. Proliferation was determined by cell counting. The cell cycle regulator cyclin D1 was detected by Western blot analysis. SMC phenotype was confirmed by positive immunostaining for smooth muscle alpha-actin. Cells migrated from the neointimal explants (NI-SMC) more rapidly than cells from explants of normal media (NM-SMC). Proliferation of NI-SMC was also more rapid than NM-SMC with or without exogenous mitogens. NI-SMC expressed more cyclin D1 than NM-SMC. Injury to the vena cava triggered neointima formation characterized by the expansion of a population of SMC with increased migration and replication compared with SMC from normal regions of the vessel.

Animals↗
PubMed2005

Removal of the OptEase retrievable vena cava filter is not feasible after extended time periods because of filter protrusion through the vena cava.

BACKGROUND: Therapeutic and prophylactic vena cava filters (VCFs) are used to prevent pulmonary embolism. Concerns exist over placing a permanent filter in a young trauma patient. Recently, retrievable VCFs have become available. One such filter is the OptEase, which has a recommended time of removal of up to 23 days after insertion. Data supporting this recommendation are sparse. Many trauma patients will need filters for more than 2 weeks, and there are no data evaluating the safety of removal after extended time periods. The purpose of this study was to determine the safety, feasibility, and reaction of the vena cava when removing the OptEase retrievable VCF at different time intervals. METHODS: Twenty Yorkshire cross pigs (80-113 kg) underwent general anesthesia with tiletamine and zolazepam. Filters were placed in the infrarenal vena cava (VC) through the femoral vein under fluoroscopic guidance. Animals were then divided into four groups. In group 1, filters were removed at 14 days; in group 2, at 30 days; in group 3, at 60 days; and in group 4, at 90 days. Removal was attempted using a snare-and-sheath technique through the femoral vein. Animals with successful filter removal were allowed to recover; then, the animals underwent autopsy (gross and microscopic VC examination) 2 months later. Animals with unsuccessful filter removal underwent autopsy immediately after attempted removal. Venacavograms were taken at filter insertion, at removal, and before autopsy to evaluate any VC abnormalities. RESULTS: Successful removal of the filter in all five pigs (100%) was reliably performed only in the 14-day group. In this group, the initial VC transverse diameter was 19.4 +/- 0.8 mm and was significantly reduced to 9.8 +/- 1.1 mm (p < 0.05) immediately after removal. Sixty days later, before autopsy, VC diameter had increased to 15.3 +/- 1.9 mm, which was significantly larger than at removal (p < 0.05) but not different from the initial value. In the 30-day group, removal was successful in only one of five animals. Although removal was successful in the one pig, autopsy at 2 months postremoval revealed total occlusion of the VC. Filters could not be removed from 60- and 90-day groups. At autopsy, the VCF struts were embedded or protruded through the VC wall. Microscopic examination of the VC revealed significant scarring underneath and between the struts. CONCLUSION: Removal of the retrievable OptEase VCF may be successfully performed up to 14 days after insertion. Strut protrusion through the VC wall prohibited successful and safe removal at extended time intervals.

Animals↗
PubMed2004

The natural history of untreated penetrating diaphragm injury: an animal model.

BACKGROUND: Surgical repair of diaphragm injuries is rather straightforward, but diagnosis can be difficult. The natural history of diaphragm injury is quite controversial. Undoubtedly, many diaphragmatic injuries are missed at the initial evaluation. Some theories state that diaphragm injuries do not heal, and that all eventually lead to herniation. Current theories regarding uniform herniation of all diaphragm injuries are not supported by animal models. The authors developed a penetrating diaphragm injury model to study the natural history of this injury. METHODS: This study used 48 male Sprague-Dawley rats weighing 300-425 g. During the study, 24 of the rats received a 16-gauge needle puncture of the left diaphragm mimicking a small penetrating wound, whereas 24 of the rats received an injury produced with a 2.7-mm aortic punch, which created a defect comparable to a much larger penetrating wound. Half of the animals in each group were euthanized at 1 month, and the other half at 10 months. This allowed short- and long-term follow-up of the injuries. Gross inspection of the left diaphragm was performed after the animals were sacrificed via a thoracoabdominal incision. All diaphragms then were removed for examination. RESULTS: All the rats experienced perioperative recovery. None of the 24 rats with a 16-gauge needle injury had an injury at 1 month (n = 12) or 10 months (n = 12). No patent injury was noted in the aortic punch injury group (n = 12) sacrificed at 1 month. At 10 months, 1 of 12 animals had a small hepatic herniation through the aortic punch injury. All the injuries displayed adhesions to the underlying left hepatic lobe. CONCLUSIONS: The authors developed a penetrating diaphragm injury model to understand better the natural history of this injury. Spontaneous healing occurred in 98% of the animals. In this animal model, because the left lobe of the liver is present beneath the left diaphragm, healing without herniation usually occurs. A role may exist for nonoperative treatment of human right diaphragm injuries in clinical practice. This animal model may prove useful in further defining future management for these injuries.

Animals↗
PubMed2004

Bedside insertion of vena cava filters in the intensive care unit using intravascular ultrasound to locate renal veins.

BACKGROUND: Historically, contrast venography has been used to determine renal vein location and assist with vena cava filter placement. This technique, however, exposes the patient to nephrotoxic contrast and radiation. For trauma patients in the intensive care unit (ICU), inferior vena cava filters should ideally be placed without contrast at the bedside to avoid nephrotoxic agents, radiation, and transport of a critically injured patient to the operating room or x-ray department. Previously, the authors have shown that intravascular ultrasound is a safe and accurate method for locating renal veins and assisting with vena cava filter placement. The purpose of this study was to evaluate bedside vena cava filter placement prospectively using only intravascular ultrasound for imaging. METHODS: Between August 2000 and July 2003, 29 patients met trauma service criteria for prophylactic or therapeutic placement of a vena cava filter. The 7 females and 22 males had a mean age of 51.3 years (range, 20-92 years), a mean height of 177 cm (range, 160-218.4 cm), a mean weight of 101.9 kg (range, 59.1-186.4 kg), and a body mass index of 33 (range, 14.7-56.1). Fifteen patients (55.5%) had a body mass index exceeding 30. The mean Injury Severity Score was 25.4 (range, 12-45). Intravascular ultrasound was the sole imaging method, and no contrast or fluoroscopy was used. All procedures were performed in the ICU by trauma surgeons. Data collection was prospective and included demographics, injuries, vena caval anatomy, length of procedure, complications, and follow-up radiographic confirmation of appropriate deployment. RESULTS: The location of the renal veins and vena cava diameter was imaged in all the patients. Three patients were noted to have accessory renal veins, and no patient had thrombus in the vena cava. The inferior vena cava diameter was less than 28 mm in all the patients, thus allowing standard filters to be deployed. Filter deployment was successful for all the patients. Of the 29 patients, 27 had abdominal computed tomography (CT) during their hospital stay. When the location of the renal veins identified by CT was compared with the level of the filter on abdominal x-ray, the filter tip was found to be at or below the level of the most caudal renal vein in 26 of the 27 patients (96.3%). In one patient, the filter tip was purposely placed 2 to 3 cm above an accessory caudal renal vein, but below the main right and left renal veins. The mean procedure time was 37.7 minutes (range, 12-86 minutes). No complications were associated with filter placement. CONCLUSIONS: Intravascular ultrasound is a safe and effective imaging method that may be used for the bedside placement of vena cava filters in the ICU. This technique avoids the use of nephrotoxic intravenous contrast and eliminates the risk of transporting a critically injured patient to the operating room or x-ray department.

Adult↗
PubMed2004

Norepinephrine is a more potent inhibitor of tumor necrosis factor over a range of doses than dopamine.

In the current study, we test the hypothesis that norepinephrine has greater anti-inflammatory effects versus dopamine over a range of doses in a model of lipopolysaccharide (LPS)-stimulated cytokine release in human saphenous vein. Segments of saphenous vein were cut and separated into 1 mm x 1 mm squares and placed into two 24-well plates. These small segments of vessels were incubated in the presence of 20 microg/mL bacterial LPS, alone as a control or with 10x-6, 10x-5, 10x-4, 10x-3 concentration of dopamine or norepinephrine and LPS. The general linear models (GLM) statistical analysis for least squares means and adjustment for multiple comparisons was chosen to analyze the data. Both norepinephrine and dopamine were able to suppress the production of tumor necrosis factor (TNF) in a dose-dependent fashion. Over the range of doses, norepinephrine is a more potent inhibitor of TNF production than dopamine. This is a statistically significant linear trend (P < .0001). Both norepinephrine and dopamine are powerful anti-inflammatory agents. Norepinephrine is a more potent inhibitor of TNF than dopamine.

Dopamine↗
PubMed2003

A prospective evaluation of a bedside technique for placement of inferior vena cava filters: accuracy and limitations of intravascular ultrasound.

Our objective was to evaluate the safety and accuracy of a bedside technique for placing vena cava filters with intravascular ultrasonography. We conducted a prospective case series of 36 patients requiring prophylactic vena cava filter placement. Intravascular ultrasound (IVUS) was used to assess the best location for inferior vena cava filter placement. Location of best filter placement was compared with a bedside technique using a fluoroscopic examination. Thirty-six patients underwent an IVUS examination. The 21 men and 15 women had a mean age of 51 years. Our bedside placement technique was successfully performed in 34 patients. Two patients did not undergo a bedside technique because of inadequate imaging. The difference between best filter placement and bedside technique was 1.22 +/- 1.24 cm. In three patients our bedside technique differed from best filter placement by more than 3 cm. Excluding these three patients the difference between best filter placement and bedside technique was 0.92 +/- 0.79 cm. This bedside IVUS technique for placement of inferior vena cava filters is established as safe and accurate; however, knowledge of the limitations involving the technique is important.

Female↗