Search PubMed⌕ Search

Biomedical subjects

M Zwaan

Publications and source records attributed to M Zwaan.

At least 37 records · Page 2Linked to original sources
PubMed1994

[DSA with mechanically injected carbon dioxide. Animal experimental results].

Carbon dioxide was used as an intra-arterial contrast medium by mechanical injection in 10 pigs. 127 angiographic examinations of 114 vascular territories were carried out and 93 were successful. A mechanism providing even gas volumes was chosen to obtain reproducible volume and pressures when using a compressible medium such as gas. Gas pressure is exponentially correlated with volume and volumes of 20-50 cm3 at 1000 mbar adequate for filling various infradiaphragmatic vascular areas. In parenchymatous organs, gas filling is seen only as far as third order arteries. The reason for this is escape of gas through preexisting arteriovenous fistulae into the efferent veins.

Angiography, Digital Subtraction↗
PubMed1993

Insufficient hemodialysis access fistulas: 18 months' experience in laser-supported dilation.

Patients with end-stage renal failure disease frequently develop venous stenoses or occlusions in their hemodialysis access fistulas caused by intimal fibrosis. A complete dilation with high pressure balloons up to 20 atm may be unsuccessful in those cases. We investigated two new pulsed dye laser devices for the ablation of obstructions, which were not adequately treatable with a previous balloon angioplasty. From November 1990 to April 1992 a total of 154 percutaneous transluminal angioplasties (PTAs) of hemodialysis access fistulas were performed. In 23 of them an additive laser angioplasty was necessary. Twenty patients with Cimino fistulas presented 28 stenoses and two occlusions, and three Goretex loops presented all occlusions. Two pulsed dye laser devices emitting at 504 nm and 595 nm wavelength were tested. Technical success was achieved in 22/23 cases, but clinical success was obtained in 20/23 patients because two early reocclusions caused by thrombosis appeared. Five restenoses occurred 2, 3, 10, and in two cases 14 months after angioplasty with a mean follow-up period of 13.5 (5-18) months. Pulsed dye laser ablation in hemodialysis access fistula lesions due to intimal fibrosis is a valuable enrichment of radiological recanalization techniques and an alternative to surgery if stand alone balloon PTA fails.

Angioplasty, Laser↗
PubMed1993

[Thrombotic and thromboembolic occlusions of leg arteries and bypasses. Short-term versus long-term lysis].

Since thrombolytic therapy is less invasive than operative thrombectomy, it is often used as initial treatment for thrombotic or thrombo-embolic occlusions of lower limb arteries or by-passes. We compared four patient groups with acute and subacute occlusions: 1. 19 patients with occluded by-passes treated by rapid lysis using 15.5 (2.5-35) mg rt-PA. 2. 12 patients with by-pass occlusions treated with initial rt-PA in a dose of 6.5 (2.5-12.5) mg followed by prolonged lysis with 5.6 (2.5-10) x 10(6) units of urokinase. 3. 16 patients with arterial occlusions treated by rapid lysis with 15 (2.5-25) mg rt-PA. 4. 14 patients with arterial occlusions given 10.5 (2.5-60) mg rt-PA followed by overnight treatment with 5.9 (2.5-15) x 10(6) units of urokinase. For by-pass recanalisation, prolonged lysis overnight had a success rate of 83% (10/12) which was better than short term lysis with a success rate of 74% (14/19). Similar results were obtained in arterial occlusions with a success rate of 86% (12/14) compared with 69% (11/16). Long term lysis did, however, have significantly more complications. In about one-third of cases further procedures had to be used in addition to lytic therapy.

Aged↗
PubMed1993

[The laser-assisted balloon angioplasty of insufficient hemodialysis-access fistulae].

Patients with end-stage renal failure frequently develop venous stenoses or occlusions in their haemodialysis access fistulas caused by intimal fibrosis. A complete dilation with high pressure balloons up to 20 atm may be unsuccessful in such cases. We investigated two pulsed dye laser devices for the ablation of obstructions, which were not adequately treatable with a previous balloon angioplasty. From 11/90 to 4/92 a total amount of 154 PTAs of haemodialysis access fistulas were performed. In 23 of them additive laser angioplasty was necessary. 20 patients with Cimino fistulas presented 28 stenoses and two occlusions, whereas all the three patients with Goretex loops presented with occlusions. Two pulsed dye laser devices emitted at the wavelengths 504 nm (green) and 595 nm (red). Technical success was achieved in 22/23 cases, but clinical success was obtained in only 20/23 patients, due to two early reocclusions caused by thrombosis. 5 restenoses occurred two, three, 10, and twice 14 months after angioplasty with a mean follow-up period of 13.5 (5-18) months. Pulsed dye laser ablation in haemodialysis access fistula lesions due to intimal fibrosis greatly enriches radiological recanalisation techniques and is a valuable alternative to surgery if stand-alone balloon PTA fails.

Angioplasty, Balloon, Laser-Assisted↗
PubMed1993

[Carbon dioxide as an irrigation medium for percutaneous angioscopy].

Since technical progress has allowed the development of small and flexible endoscopes, percutaneous, transluminal angioscopy promises to be a diagnostic and therapeutic tool. Nevertheless, the main problem is to obtain a satisfactory bloodless visual field. The saline solutions used for this purpose present problems with hypervolaemia, insufficient clearance, and decreased refraction. We investigated a CO2 application system for angioscopy that allows the reproducible injection of variable quantities of gas, pressure, and injection time. In 10 pigs undergoing angioscopy, CO2 was injected through a Swan-Ganz catheter under blockade of the distal aorta. Using a bifemoral approach, the application of gas and the blocking balloon were controlled by an automatic gas injector. The CO2 was injected through the tip of the catheter with a constant flow and a variable pressure and time. The angioscopy procedures were videotaped. With small volumes of carbon dioxide (approximately 50 cm3; 1000 mbar application pressure) a column of gas can be created which, unlike liquids, completely displaces blood from the vessels and allows for several minutes a bloodless inspection of the aorta and the side branches without blood mixture. Carbon dioxide application allows safe and successful percutaneous angioscopy under optimal conditions if the quantities of gas, pressure, and injection time are adjustable. The tested gas injection device fulfills these conditions.

Angioscopes↗
PubMed1991

A new concept for a realtime feedback system in angioplasty with a flashlamp pumped dye laser.

The feasibility of using a pulsed dye laser in angioplasty for detection and disintegration of calcified plaques was studied in vitro. A flashlamp-pumped dye laser (495 nm, 2 microseconds) was used as the exciting source for laser-induced-fluorescence (LIF) signals. Spectral data in the 520 nm to 800 nm region of normal intima, calcified plaque and fibro-fatty plaques were analyzed with an optical multichannel analyzer, using the same fiber for energy delivery and fluorescence diagnostic. Good signal to noise ratio and different spectra for different specimens were obtained within only 2 microseconds. The spectral difference is caused by selective reabsorption of oxyhemoglobin in the vessel wall. Time resolved LIF-spectroscopy shows that the fluorescence intensity reaches its maximum value before the maximum laser intensity is delivered. Fluorescence analysis can be performed in less than 300 ns and therefore the laser can be controlled before plasma threshold is reached. The described in vitro results can lead to a clinical useful feedbacksystem for energy control of microseconds lasers in angioplasty if the blood interference effects can be minimized by changing the laser excitation wavelength or staining the tissue.

Angioplasty, Laser↗
PubMed1991

[Normal wall thickness and neoplastic wall changes in the gastrointestinal tract as shown by computed tomography].

55 patients with tumours of the gastrointestinal tract were examined by CT, using a paraffin emulsion as a negative oral contrast medium. These were compared with 119 normal patients. The appearance of normal and tumour bearing portions of the gut wall against the contrast medium was studied. Under hypotonic conditions the gut wall could regularly be distinguished from surrounding organs and gut content. Mural thickness of the oesophagus greater than 7 mm and of the stomach and colon greater than 8 mm must be regarded as abnormal. Benign diseases cannot be distinguished from malignant conditions on the basis of wall thickness. Artifacts, such as are caused by positive oral contrast, were of less significance when using paraffin emulsion.

Adult↗
PubMed1990

[Computerized tomography findings in neck abscess ].

Computed tomography was the diagnostic confirming method in two patients with a necrotic cervical phlegmon caused by an infection of streptococcus pyogenes and candida albicans. A cervical phlegmon is frequently caused by the lymphogenic transmission of diverse primary infections. The time between the primary infection and the appearance of a cervical phlegmon is very varied. In rare cases it is possible that the primary focus will have cured completely. The cervical fasciae separate the neck into three different spaces, which, together with their hypostatic abscess paths, can be visualized using CT. The use of the central veins (e.g., the jugular vein) to administer medication etc. means that the deep cervical phlegmone will continue to be a complication in intensive-care patients.

Candidiasis↗
PubMed1990

[Selective catheter angiography using a translumbar technic].

By using a new 5-F-needle-sheath system for translumbar aortic puncture, it was possible to introduce 4-F-catheters of different lengths and shapes. In nine patients 19 vessels were selectively catheterised. There were no complications. The trans-lumbar approach to selective angiography is a simple and safe alternative to the more dangerous trans-brachial method.

Aged↗