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Biomedical subjects

F Laerum

Publications and source records attributed to F Laerum.

67 records · Page 4Linked to original sources
PubMedDate not supplied

Sequestrated thrombolysis: comparative evaluation in vivo.

PURPOSE: Lysis of a thrombus is a function of the local concentration of thrombolytic enzymes. This study was designed to determine in a porcine model of acute deep vein thrombosis (DVT) whether perithrombic sequestration of small volumes of a concentrated enzyme solution can accelerate the process of thrombolysis. METHODS: DVT was induced in both hind limbs using a previously described technique (n = 32). Thirty minutes later the animal was heparinized and unilateral thrombolysis was attempted using 8 mg recombinant tissue plasminogen activator (rt-PA); saline was administered in the opposite leg. For conventional high-volume infusion (CI) (n = 5) rt-PA (0.067 mg/ml) was infused at 1 ml/min. For sequestrated thrombolysis the external iliac vein was endoluminally occluded, and rt-PA (0.25 mg/ml) administered either for proximal injection (ST-P) (n = 5), as a bolus every 3 min through a microcatheter placed via the balloon catheter, or for transthrombic injection (ST-T) (n = 5), as a bolus every 3 min through a Katzen wire in the balloon catheter. At autopsy, the thrombus mass in the iliofemoral veins was measured, and the extent of residual thrombosis in the venous tributaries graded at four sites. From these data a thrombolysis score was calculated. RESULTS: One pig died before thrombolysis could be performed. Only with ST-T was residual thrombus mass in the test limb normalized to control, residual thrombus index (RTI), consistently less than unity. The median RTI of this group was 0.50 (range 0.39-0.97) compared with 1.22 (0.64-1.38) for ST-P and 0.88 (0.37-1.13) for CI. Compared with contralateral controls, a lower grade of residual thrombosis in tributaries was observed in test limbs at more venous sites with ST-T (8/20; 95% confidence interval 5-13) and ST-P (9/20; confidence interval 5-13) than with CI (2/20; confidence interval 0-5) (p = 0.04). A trend toward lower thrombolysis scores was observed with ST-T (p = 0.08). Systemic fibrinogenolysis was not observed in any of the groups. Changes in coagulation parameters during thrombolysis were similar irrespective of treatment protocol. CONCLUSIONS: "Transthrombic" sequestrated thrombolysis may offer some advantages over conventional selective infusion for the treatment of acute DVT. However further refinements will be necessary before it can be considered an alternative to the latter.

Acute Disease↗
PubMedDate not supplied

The new interventional centre--a multidisciplinary R&D clinic for interventional radiology and minimal access surgery.

The National Hospital wanted to coordinate and promote the development of new minimally invasive procedures by structuring collaboration and communication across traditional speciality boundaries. To achieve this, a new hospital department has been established, a 'neutral ground' for working with such clinical applications in multi-disciplinary teams with surgeons, radiologists, cardiologists etc., individually composed for the type of intervention to be performed. The Interventional Centre also represents a full fusion of a modern radiology department with a state-of-the-art operating department, securing the use of relevant imaging technologies, aseptic conditions and options of converting any 'key-hole' procedure to open, conventional surgery within minutes. The Centre represents a new organizational model for such activities. It is also a technology centre, a common 'tool-box' securing better access and higher quality for the use of advanced radiological and surgical technology in our hospital.

Hospital Departments↗
PubMedDate not supplied

Complement activation by angiographic catheters in vitro.

PURPOSE: Four different polymers used in commercial angiographic catheters were compared in vitro with respect to their ability to activate the complement system. MATERIALS AND METHODS: Commercially available angiographic catheters made from one of the following plastics were used: polyamide, polyethylene, polyurethane, and polytetrafluoroethylene. Silicone-coated latex urinary catheters served as the reference standard. Each catheter was cut into 20-mm segments, immersed in a polypropylene tube containing fresh serum from a volunteer donor, and incubated at 37 degrees C. Samples were drawn at 15 minutes, 1 hour, and 6 hours; C3 activation products (C3AP) and the terminal complement complex (TCC) content were estimated with enzyme immunoassays. RESULTS: By 1 hour, a significant increase in C3AP and TCC concentrations was observed with all angiographic catheters relative to controls (P < .01-.001). The time-concentration plots for both C3AP and TCC were steepest for polyamide. C3AP concentrations relative to controls were significantly higher with exposure to polyamide compared with polyurethane at 1 hour (P < .01), and with both polyethylene and polyurethane at 6 hours (P < .01). Polytetrafluoroethylene induced larger amounts of C3AP formation by 6 hours than polyethylene and polyurethane (P < .05). However, polytetrafluoroethylene was associated with the lowest relative median concentrations of TCC; the difference with polyamide was significant at 6 hours (P < .001). As with C3AP, differences in TCC generation between polyethylene and polyurethane were marginal at all observation points (P > .05). CONCLUSIONS: All the polymers tested activated the complement system. Activation was most prominent with exposure to polyamide and least marked with polyurethane.

Angiography↗
PubMedDate not supplied

Multiple emboli and filter function: an in vitro comparison of three vena cava filters.

PURPOSE: To establish the influence of number of emboli on the trapping ability of vena cava filters in vitro. MATERIALS AND METHODS: Three filters, the titanium Greenfield, Vena Tech-LGM, and Günther Tulip retrievable, were studied with use of 20- or 26-mm-diameter tubes to simulate the inferior vena cava. In the first protocol, five small (4 x 20-mm) or medium (6 x 10-mm) emboli were delivered in sequence, and the fate of each was recorded. In the second protocol, medium or large (6 x 30-mm) clots were sequentially introduced until filter occlusion occurred or 50 clots had been delivered. RESULTS: For the first protocol, 82% of first small clots and 60% of second clots were trapped in 20-mm tubes (P = .001) and 63% and 45%, respectively, were trapped in 26-mm tubes (P - .02). With medium clots, the proportion trapped also dropped significantly with ascending clot rank. In the second protocol the proportion of clots captured was invariably higher for the first 10 clots (P < .001 for all combinations of covariables). CONCLUSION: Filter function deteriorates with number of emboli delivered, irrespective of embolus size and simulated vein caliber.

Confidence Intervals↗
PubMedDate not supplied

Induced thrombosis in the pig inferior vena cava: a model of deep venous thrombosis.

PURPOSE: To establish a new animal model of deep venous thrombosis. MATERIALS AND METHODS: Fifteen young pigs underwent temporary interruption of the inferior vena cava (IVC) below the entry of the right renal vein by means of either a silicone band (surgical technique, n = 6) or an intraluminal balloon catheter (endovascular technique, n = 9), followed by injection of absolute ethanol. Lumbar veins within 3 cm below the obstruction were ligated or occluded interventionally. The iatrogenic caval obstruction was relieved after 2 days. RESULTS: Procedure-related mortality was 33% (n = 2) and 11% (n = 1) for the surgical and endovascular groups, respectively. An adherent, occlusive thrombus was found in all four of the remaining surgically treated animals and in six of eight animals treated percutaneously. The IVC remained patent in two animals in whom balloon migration occurred. Severe caval stenosis invariably occurred after surgical banding. CONCLUSION: IVC thrombi suitable for the study of various recanalization therapies can be reliably created with this pig model.

Angioplasty, Balloon↗
PubMedDate not supplied

Human endothelial cell culture as an evaluation system for the toxicity of intravascular contrast media.

Endothelial cells in primary cultures from human umbilical cord veins were incubated with various radiographic contrast media in increasing concentrations up to approximately 60 mgI/ml for 24 hours in order to study their toxicity. Cell death was recorded with the chromium-51 (51Cr)-release method and controlled by dye exclusion tests, Coulter counting, and protein determination. The hyperosmolar, ionic contrast medium, meglumine metrizoate, was far more toxic to the endothelium than the nonionic media, metrizamide and iohexol, which are far less hyperosmolar. The 51Cr-release test on endothelial cultures provides a simple and useful technique in the evaluation of various intravascular contrast media and their components.

Cell Survival↗
PubMedDate not supplied

Double blind evaluation of the effects of various contrast media on extremity veins in the dog.

Canine superficial extremity veins were examined grossly and microscopically in a double blind fashion for endothelial damage and phlebitis one hour and four days after the injection of ionic monomeric or dimeric, and non-ionic monomeric, 300 mg I/ml, contrast media. Superficial veins of all four extremities and the tail vein were injected with the same amounts of contrast medium after application of tourniquets for 20 minutes following the injections. Silver staining and prefixation of the veins were done in situ. The specimens were evaluated together with cross-sectioned, hematoxylin-eosin stained biopsies. On the basis of a randomized study of 77 dogs, endothelial damage or thrombosis caused by various contrast media as seen in man was not demonstrated. This may be due to species differences. It is postulated that canine endothelium may have a higher resistance to contrast medium injury than human endothelium.

Animals↗
PubMedDate not supplied

Acute lethality after enteral administration of contrast media in anaesthetized rats with intestinal ischaemia.

The acute lethality was evaluated during enteric follow-through in anaesthetized rats with a ligature applied to the anterior mesenteric artery and vein. In 121 animals 3 ml of either sodium diatrizoate, iohexol or barium sulphate was administered via orogastric tube. Alternatively, they had the oro-gastric tube inserted but no test substance instilled (controls). A total of 103 rats was observed until spontaneous death while 18 were sacrificed after 8 hours of observation. The survival time in the sodium diatrizoate group was significantly shorter than for the other three groups (p less than 0.006). The 50% survival time was 5 h 42 min (range 2 h 48 min to 12 h 45 min) for sodium diatrizoate as compared with 8 h 4 min to 8 h 26 min for the other three groups; iohexol 8 h 4 min (range 2 h 4 min to 14 h 43 min), barium 8 h 13 min (range 4 h 55 min to 16 h 26 min) and no instilled substance 8 h 26 min (range 3 h 38 min to 16 h 10 min) with no significant differences between these 3 groups. The use of hyperosmolar contrast media in enteric follow-through significantly shortens the survival of rats with acute intestinal ischaemia. A more rapid spread of intestinal bacteria through the distended bowel wall and the ensuing septicaemia, accompanied by enhanced dehydration, are probably the mechanisms responsible for the earlier deaths.

Anesthesia↗
PubMedDate not supplied

Cytotoxic effects of six angiographic contrast media on human endothelium in culture.

Human endothelial cells in cultures derived from the veins of fresh umbilical cords were incubated for 24 hours with angiographic contrast media added to the cell culture medium. The cells were preincubated with Na2(51Cr)O4 for subsequent 51Cr-release test. Four different concentrations of the contrast media were used. Cell toxicity as judged by measuring the release of 51Cr was, in decreasing order, as follows: Sodium/meglumine diatrizoate, meglumine metrizoate, ioxaglate, iopamidol, metrizamide, iohexol. The highest concentration of sodium/meglumine diatrizoate (Urografin) led to 99 per cent cell death after 24 hours, while the same concentration of iohexol (Omnipaque) induced about 40 per cent cell lysis. The assay system with human endothelial cells thus seems to be useful for evaluation of the toxicity of contrast media. The osmolality was measured in all the solutions. Hyperosmolality accounted for a major part of the cell toxicity, but additional toxic effects of the substances were observed. The strongest osmolality-independent toxic effect was caused by ioxaglate.

Angiography↗
PubMedDate not supplied

Iohexol and ioxaglate in peripheral angiography.

A double-blind, cross-over trial of the non-ionic, low-osmolar contrast medium iohexol (Omnipaque) and the ionic, low-osmolar medium ioxaglate (Hexabrix) at concentrations of 300 mg I/ml was carried out in 107 consecutive patients with arterial insufficiency of the lower limbs. The purpose of the study was to observe possible 'carry-over' effects from any of the contrast media, and to evaluate patient discomfort such as pain, adverse reactions, or effect on peripheral blood pressure. No carry-over effect was seen. Ioxaglate caused less injection pain and heat sensations than iohexol, and showed less effect on the systemic blood pressure.

Aged↗
PubMedDate not supplied

Water-soluble contrast media in radiography of small bowel obstruction. Comparison of ionic and non-ionic contrast media.

Fifty patients with possible gastrointestinal obstruction, referred for enteric follow-through examination, were randomized for a double-blind, parallel comparison of the hyperosmolar contrast medium Gastrografin and the low-osmolar Omnipaque. The result was that Omnipaque retained its radiographic density in the small bowel better than Gastrografin. Omnipaque was thus a better alternative than Gastrografin in follow-through examinations of intestinal obstruction. Also, 23 patients out of 28 with small bowel obstruction due to peritoneal adhesions, had spontaneous relief of symptoms during the observation period following contrast medium ingestion with no significant difference between the two media. This indicated that enteric follow-through procedures may have a therapeutic efficacy similar to the treatment of small bowel obstruction using nasogastric suction and gastrointestinal rest. Possible mechanisms for this action of the contrast media are discussed.

Aged↗
PubMedDate not supplied

Water-soluble contrast media compared with barium in enteric follow-through. Local effects and radiographic efficacy in rats with simple obstruction of the small bowel.

The local effects and radiographic efficacy of 4 water-soluble contrast media, barium and saline were evaluated in 86 anaesthetized rats with the distal ileum ligated. The rats were observed for 8 hours after instillation of 3 ml of the test substance via orogastric tube. Radiographs were taken after 1, 4 and 8 hours of observation. After 8 hours the intestines were weighed and biopsied for light microscopy, and blood and urine were sampled for testing. Sodium diatrizoate caused increased fluid influx to the bowel lumen and, like barium, provided poorer radiographic images as compared with iohexol, ioxaglate or iodixanol. Barium showed slower progression through the small bowel than the other agents, while sodium diatrizoate was the most rapidly progressing contrast medium and caused the greatest distension. Correlation to osmolality was obvious. No significant morphologic effects on the small bowel mucosa were seen in any of the groups. Low-osmolar, water-soluble contrast media may have prospects for clinical use in patients with suspected small bowel obstruction.

Animals↗