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Biomedical subjects

H Bjarnason

Publications and source records attributed to H Bjarnason.

At least 19 recordsLinked to original sources
PubMed2001

Renal artery embolization with diluted hot contrast medium: an experimental study.

PURPOSE: To evaluate the safety and efficacy of diluted hot contrast medium to embolize the renal arteries in a canine model. MATERIALS AND METHODS: Transcatheter embolization was performed in 15 dogs (five dogs in each phase: I, II, and control). The diluted hot contrast medium was heated to 90 degrees C--100 degrees C and 30--60 mL were injected into a renal artery of each dog in phase I (optimization studies) and II (efficacy studies). In the control group, balloon inflation was performed without injection of diluted hot contrast medium. The temperature measurement was performed on one dog in phase I by temperature probe. Follow-up angiography was performed immediately (n = 15), at 1 week (n = 9), at 1 month (n = 9), and after 3 months (n = 5). All dogs were killed and kidneys were removed for histologic examination. RESULTS: The procedure was performed successfully in all dogs. Follow-up angiography showed complete obstruction of the injected renal arteries in phases I and II. The microscopic findings showed acute full-thickness necrosis of the renal cortex and renal artery in phase I, and complete coagulative necrosis of the cortex, medulla, and intrarenal blood vessels in phase II. There were no histologic changes of renal veins, inferior vena cava (IVC), and aorta. There were nonspecific findings in the control group. CONCLUSION: This preliminary experimental study suggests that diluted hot contrast medium may be a safe agent for renal ablation without thrombus formation in the renal vein or IVC.

Animals↗
PubMed2001

Preventing contrast-induced nephropathy with fenoldopam.

Fenoldopam is an interesting orphan drug that is a variant of dopamine. It differs significantly from dopamine in that it is a specific agonist for the type I (DA-1) receptor. The DA-1 receptors are particularly prominent in the renal vasculature, renal tubules, mesenteric vasculature, and peripheral vessels. The DA-1 receptor stimulation vasodilates renal and peripheral vessels, causing a decrease in blood pressure and an increase in renal blood flow (RBF). Stimulation of the DA-1 receptors in the tubules causes an increase in sodium excretion, which gives rise to an increase in urine volume on the basis of a sodium natriuresis. Animal testing with fenoldopam has indicated that it is 6 times more potent than dopamine in its ability to decrease renal vascular resistance and increase RBF; this suggests that it could be a much more selective and potent renal protective agent against any toxin or stimulus that causes renal dysfunction by reducing RBF or increasing renal ischemia. The clinical activity of fenoldopam, which is administered intravenously, begins almost immediately and is clearly noticeable after 5 minutes. The drug has no rebound effect, and its use can be stopped at any time. The protocol for the use of fenoldopam as a renal protective agent (performed at the University of Minnesota) involves starting an intravenous fenoldopam infusion 2 hours before the procedure at a rate of 0.1 microg/kg/min and increasing the dose in increments of 0.1 microg/kg/min every 20 minutes, until a rate of 0.5 microg/kg/min is reached or the systolic blood pressure falls more than 40 mm Hg (or below 110 mm Hg). Any infusion level at or above 0.1 microg/kg/min is considered acceptable because the response in individual patients varies so widely. The fenoldopam infusion is maintained at the maximum rate throughout the procedure and for up to 4 hours after the end of the contrast administration. At the University of Minnesota, we have had anecdotal experience using the drug in 29 patients. The drug was used for patients who were thought to be at the highest risk for contrast-induced nephropathy, ie, patients who have both diabetes and pre-existing renal failure. In this small group of patients in whom hydration and other variables were not controlled, there was a startling lack of contrast-induced creatinine increase at any point during the 24 to 48 hours after the administration of contrast in all but 1 patient. Our experience suggests that fenoldopam may be of distinct benefit to high-risk patients who need intravascular contrast, especially those who may receive a large contrast dose, such as patients undergoing peripheral or coronary angiography and intervention and/or computed tomography. Although it is impossible on the basis of simple anecdotal case reports to determine whether or not the drug was the primary reason that such a marked protective effect was seen, the results are promising enough to indicate that a careful, prospective, randomized trial of fenoldopam versus hydration is warranted.

Animals↗
PubMed2000

Superior vena cava stenting.

Treatment of SVC obstruction with metallic stents is a rewarding procedure. The patients have symptoms that are severe and debilitating and cause significant impairment of life-style. Stent placement rapidly alleviates the symptoms of SVC syndrome and improves the patient's quality of life. The long-term patency rates have not been established; however, in patients with SVC syndrome secondary to malignant disease, stents usually remain patent for the lifetime of the patient. Recurrences can be treated with further interventional radiographic techniques. Currently, because the long-term patency rates of SVC stents are not known, most interventional radiologists tend to treat SVC stenosis from benign causes with balloon angioplasty before placing metallic stents.

Anticoagulants↗
PubMed2000

Fisher information for two gamma frailty bivariate Weibull models.

The asymptotic properties of frailty models for multivariate survival data are not well understood. To study this aspect, the Fisher information is derived in the standard bivariate gamma frailty model, where the survival distribution is of Weibull form conditional on the frailty. For comparison, the Fisher information is also derived in the bivariate gamma frailty model, where the marginal distribution is of Weibull form.

Bacterial Infections↗
PubMed1999

Tracheobronchial metal stents: effects of covering a bronchial ostium in pigs.

RATIONALE AND OBJECTIVES: The purpose of this study was to examine the effects of placing a metal stent across a bronchial orifice. MATERIALS AND METHODS: Nine pigs were used as test subjects, because the right upper lobe bronchus comes directly off the trachea in these animals. One of three types of metal stents was placed into the trachea of each pig and covered the orifice of the right upper lobe bronchus. Follow-up studies were performed at 1 and 3 months to evaluate the right upper lobe for signs of bronchial obstruction, infection, and atelectasis. The animals were sacrificed at 3 months to study the histopathologic changes of the trachea and lungs. RESULTS: Two upper lobe bronchi remained patent; seven were obstructed by granulation tissue or plugs of mucus and inflammatory cells. Right upper lobe infiltration and atelectasis were seen in eight animals. Interestingly, radiographic opacities were also common in other lung segments. There was a tendency toward fewer and less extensive lung opacities at 3 months compared with that at 1 month. At histopathologic examination, areas of both acute and chronic pneumonia were found in the right upper lobe of all animals. The segment of trachea covered by the stent was lined with a thin layer of granulation tissue containing neutrophils, monocytes, and lymphocytes. The stent luminal surface was covered with columnar, cuboidal, and stratified squamous epithelium. Tracheal stenosis was seen in three animals because of excessive granulation tissue in two and a collapsed stent in one. CONCLUSION: Placement of metal stents in pig trachea covering the orifice of the right upper lobe bronchus resulted in retention of secretions and secondary infection in the right upper lobe and other distant lung segments.

Animals↗
PubMed1997

Biliary tree malignancies: the University of Minnesota experience.

Because of its slow-growing natural history, most patients with extrahepatic biliary tree malignancies present with inoperable disease. For the minority of patients with operable disease, surgical resection remains the treatment of choice and offers the patient the best chance for long-term local control. The role of chemotherapy and radiotherapy in the management of these patients in the definitive, adjuvant, and palliative setting is expanding, although unsettled. Response rates with chemotherapy have been low and will most likely find a place in a combined multimodality setting. Radiotherapy (external beam, intraoperative, and intraluminal brachytherapy using 192Ir) has played a major role in the treatment of these cancers. The close proximity of bowel, kidney, and liver limits the external beam radiotherapy doses that can be safely delivered. Since most patients require placement of percutaneous transhepatic biliary catheters to relieve jaundice, this route has been utilized to deliver higher doses of radiation to the tumor area with intraluminal 192Ir ribbons. The University of Minnesota has treated 15 patients with extrahepatic bile duct cancers. Most were located at the bifurcation of the common bile duct and were treated with intraluminal brachytherapy alone or with external beam radiotherapy. Our results are comparable to previously reported retrospective data with a median survival of 8 months and three long-term survivors.

Aged↗
PubMed1997

Refractory ascites: midterm results of treatment with a transjugular intrahepatic portosystemic shunt.

PURPOSE: To assess midterm results and examine factors associated with successful treatment of refractory ascites with creation of a transjugular intrahepatic portosystemic shunt (TIPS). MATERIALS AND METHODS: In 50 patients with refractory ascites, TIPS creation was performed. Clinical and ultrasound follow-up were performed. Success was defined as survival with no further therapeutic paracentesis and decreased ascites. RESULTS: Mean follow-up was 11.6 months after the TIPS procedure. Major complications occurred in 16% of patients including intraperitoneal hemorrhage, refractory encephalopathy, and progression of liver and renal failure. Overall mortality was 60% (30 patients). In 23 (62%) of 37 patients not lost to follow-up, ascites was controlled successfully at 1-3 months. A bilirubin level greater than 3.0 mg/dL (52 mumol/L) and creatinine level greater than 1.9 mg/dL (170 mumol/L) were associated with treatment failure (86% treatment failure at 3 months) and early mortality (P = .03). In all 14 patients alive at 1-year follow-up, ascites was controlled successfully. CONCLUSION: TIPS creation is often useful in treatment of severe ascites not controlled with medical therapy. In patients with advanced liver and renal failure, TIPS creation is not associated with a definite benefit and may hasten death.

Adolescent↗
PubMed1996

The mechanisms of positional dysfunction of subclavian venous catheters.

PURPOSE: To determine the origin of subclavian vein catheter and lead dysfunction. MATERIALS AND METHODS: Cineradiography was performed on 10 patients with subclavian venous catheter dysfunction and three patients with pacemaker or defibrillator lead dysfunction. The leads and catheters were removed and replaced with use of a fluoroscopically guided technique; the needle entered the vein lateral to the first rib. Repeat cine examinations were performed following placement of new catheters. RESULTS: The cause of the dysfunction of all 10 catheters was shown to be pinch by the subclavicular musculotendinous tissues as the catheter passed below the clavicle toward its entry into the vein. All three leads were entrapped in the subclavicular tissues and stretched during abduction. The abnormal motion and clinical problems were eliminated after replacement. CONCLUSION: Subclavian catheter and lead malfunction is not due to compression between the first rib and the clavicle. It is due to entrapment in the subclavius muscle-costoclavicular ligament complex, which binds or compresses the device during movements. These problems can be avoided by employing fluoroscopically guided puncture techniques that enter the vein lateral to the first rib.

Catheterization, Central Venous↗
PubMed1996

Iliofemoral venous stenoses: effectiveness of treatment with metallic endovascular stents.

PURPOSE: To assess effectiveness of metallic endovascular stents in treatment of venous stenoses and occlusions. MATERIALS AND METHODS: Stents were placed intravenously in 56 patients (59 stenoses or occlusions) over a 6-year period. Stent sites included the inferior vena cava (n = 10) and common iliac (n = 31), external iliac (n = 46), common femoral (n = 27), and superficial femoral veins (n = 4). Indications for stent placement included stenoses from pelvic malignancy and its treatment; trauma, surgery, or pregnancy; and idiopathic stenoses. Patients underwent anticoagulation therapy for 3-6 months after stent placement. Follow-up was performed with duplex ultrasound. RESULTS: With use of life-table analysis, overall primary and secondary 1-year patency rates were 50% and 81%, respectively. Primary and secondary 4-year patency rates were and 50% and 75%, respectively. Five patients died of primary disease progression within 6 months after stent placement. Major complications occurred in 6.8% of cases. One-year secondary patency rates were statistically significantly lower (P = .05) for patients with malignant disease, although primary patency rates were comparable. Overall sustained decrease in symptoms (P < .0001) was observed 1 year later. CONCLUSION: Endovascular stent placement is a nonsurgical alternative for reestablishment of venous flow and sustained relief of symptoms in patients with malignant or benign pelvic venous disease.

Adult↗
PubMed1996

Effect of transjugular intrahepatic portosystemic shunt on quality of life.

OBJECTIVE: The objective of this study was to determine the effect of the transjugular intrahepatic portosystemic shunt (TIPS) procedure on the quality of life. SUBJECTS AND METHODS: Data were collected on 99 patients who underwent the TIPS procedure between September 1991 and September 1995. Quality of life was assessed by the Karnofsky scale before and at intervals after the procedure. Procedure-related complications and other aspects of the patients' overall well-being, as reflected in liver and kidney function and nutritional status, were reviewed immediately before and after TIPS creation. Finally, mortality and TIPS patency rates were tabulated. RESULTS: We observed significantly improved quality of life. The quality of life remained significantly improved throughout the 24-month follow-up period. During the 1- to 3-month interval after the TIPS procedure, we observed in patients a significant decrease in blood urea nitrogen and an increase in albumin and bilirubin. During this period, patients had no significant change in liver enzymes, prothrombin time, ammonia, or creatinine. Complications of the TIPS procedure included a 30% incidence of new or worsened encephalopathy and a 15% incidence of other severe complications (intraperitoneal hemorrhage, severe accelerated liver failure). The procedure-related death rate was 5%. Longer term follow-up showed an overall sustained decrease in blood urea nitrogen, an increase in albumin, and a return of bilirubin to the pre-TIPS levels or below. CONCLUSION: For patients who survive longer than 1 month, TIPS results in an overall, sustained improvement in the quality of life. Improved quality of life may result from a low incidence of repeat variceal bleeding, decreased ascites, and improved nutritional status.

Adolescent↗
PubMed1995

Applications of the Amplatz snare device during interventional radiologic procedures.

The Amplatz gooseneck snare (Microvena, St. Paul, MN) is a recently developed device for the percutaneous removal of intravascular foreign bodies [1-5] (Fig. 1). In the past several years, various other applications of this snare system have been devised for placing, replacing, repositioning, or removing guidewires, catheters, and other devices during interventional procedures. The Amplatz gooseneck snare, which has been described [1], comes in a variety of loop sizes and is provided with either 4- or 6-French guiding catheters, although substitution with any of several soft, blunt-tipped guiding catheters is possible [5]. The principal advantage of the Amplatz snare over past systems is that the loop is at a right angle to the catheter, easing the capture of foreign bodies, devices, or catheters.

Blood Vessels↗
PubMed1994

In vitro metal fatigue testing of inferior vena cava filters.

RATIONALE AND OBJECTIVES: Inferior vena cava filter fractures have been described in vivo on several occasions. No studies have compared the fatigue life of the different filter types. Four different, frequently used filters (Vena-Tech filters [VTF], stainless-steel Greenfield filters [SSGF], Simon nitinol filters [SNF], and titanium Greenfield filters [TGF]) were, therefore, tested with regard to fatigue life. METHODS: Ten filters of each type were tested by compressing the filter legs repeatedly. A travel distance of 1.5 cm was used, setting minimal and maximal filter leg separations of 1.0 cm and 2.5 cm, respectively. The endpoint was filter fracture or 10,000,000 compressions. The test was then repeated on five of the filters from each group, but on a different filter leg pair. RESULTS: Seven of 10 VTFs fractured during the first part of the study, and all five VTFs fractured during the second part of the study. One SSGF fractured in each part of the study. None of the SNFs or the TGFs fractured. Significant difference in fracture frequency was found. CONCLUSION: The VTFs appear to have the shortest fatigue life. The TGF and the SNF have a fatigue life exceeding the test limits. The consequences of filter fracture are unknown.

Alloys↗
PubMed1994

Development of stenoses in transjugular intrahepatic portosystemic shunts.

PURPOSE: To evaluate the frequency and significance of stenoses or occlusions developing within transjugular intrahepatic portosystemic shunts (TIPS) and identify predictive factors. MATERIALS AND METHODS: Medical records of 52 patients who underwent TIPS placement between September 1991 and October 1993 were reviewed. Various shunt parameters were correlated with the development of shunt abnormalities. Findings at follow-up portography and frequency of variceal bleeding and paracentesis were also noted. RESULTS: Twenty-four patients were followed up for at least 6 months. In eight patients, stenoses developed within 6 months; one shunt occluded. No clear correlations were found between shunt parameters and development of shunt abnormalities. Two of four patients with recurrent variceal bleeding had associated shunt abnormalities. The frequency of stenosis of TIPS was high. CONCLUSION: Early detection and prompt revision of stenotic shunts may decrease the frequency of recurrent variceal bleeding and ascites.

Adolescent↗
PubMed1993

Refractory ascites: early experience in treatment with transjugular intrahepatic portosystemic shunt.

PURPOSE: To evaluate the transjugular intrahepatic portosystemic shunt (TIPS) in treatment of refractory ascites. MATERIALS AND METHODS: Fourteen patients with chronic liver disease and portal hypertension were included in a prospective study. Six patients had Child-Pugh class B disease; eight had class C disease. Indications for TIPS were three previous hospital admissions over 9 months for treatment of tense ascites, no response to diuretic therapy, or an occluded peritoneovenous shunt with tense ascites. The volume of ascitic fluid was sonographically evaluated before and after TIPS placement. RESULTS: The technical success rate for TIPS creation was 93%. Mean portosystemic gradient decreased from 22.8 mm Hg +/- 7.2 before TIPS placement to 11.3 mm Hg +/- 3.6 after TIPS (P = .005). Complete resolution of ascites was achieved in seven (50%) patients. Treatment failed in seven; five had Child-Pugh class C disease, and four of these had a Child-Pugh score greater than 11. CONCLUSION: These results are comparable to those for other forms of treatment of ascites. The authors do not, however, recommend TIPS in patients with a Child-Pugh score greater than 11.

Ascites↗