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Biomedical subjects

D Maass

Publications and source records attributed to D Maass.

36 records · Page 2Linked to original sources
PubMed1986

Experience with the helix cava filter.

A new caval filter of helico-spiral geometry (Helix-Filter) was implanted in 13 patients for the prevention of pulmonary embolism (PE). The indications for implantation were: recurrent PE despite adequate anticoagulation (5 cases) or contraindication to anticoagulation (3 cases), incomplete local therapeutic fibrinolysis after severe paracentral PE (2 cases), and prophylaxis in high risk patients (3 cases). Implantation was effected by the saphenous/femoral vein approach in 12 patients, and via the right atrial appendage during open heart surgery in one instance. There were no intraoperative technical problems and in no case was the filter misplaced. During the follow-up period (mean 14.8 months, maximum 28 months) no filter-related complications were encountered. One patient with an exceptionally enlarged vena cava, due to abnormal renal vein inflow, had a fatal recurrent PE despite high dosage heparinization. One patient with an event-free follow-up died 12 months after filter placement from unrelated diseases. The remaining 11 patients are free of symptoms with no recurrent PE, no deterioration of venous circulation or presence of caval thrombosis. Emboli trapped at the filter were documented in 2 patients; spontaneous resolution occurred in one case. Experimental and early clinical results indicate that the hemodynamically optimal design of the Helix-Filter permits controlled and uniform luminal filtering with high patency. As such, it represents an alternative and highly promising solution to the problem of "mechanical" prevention of pulmonary embolism in selected patients.

Adult↗
PubMed1985

Intravenous spiral support for the prevention of outflow-tract stenosis in av-shunts for hemodialysis?

Intraluminal spiral support of bovine heterografts (Solcograft-P) offers promising mechanical characteristics for av-shunts. Using a tunneling technique the spiral prevents twisting and kinking during subcutaneous placement and allows prolonged and vigorous post-puncture compression for hemostasis without compromising shunt flow. Canine experiments (femoro-femoral loop) suggest that additional insertion of the spiral into the efferent vein for some centimeters can prevent or delay the development of outflow-tract stenosis, the main cause of late shunt failure (0% (0/5) vs. 75% (3/4) significant stenosis; total patency rate 90% (9/10); follow-up 3 months). Preliminary clinical results with brachio-cephalic/basilic av-shunts in the forearm (loop) support our experimental investigations. In all eight patients the shunt is functioning perfectly without reinterventions being necessary (mean follow-up 8.8 months, totally 55 dialysis months). In five patients the shunt was used early for hemodialysis (days 1-10 post operation). Angiographically, stenoses developed in the outflow-tract in five of six shunts, but only one stenosis was observed in the spiral-supported venous segment where it usually occurs. In some cases shunt function was preserved by collaterals from the nonstenotic spiral-supported venous segment despite occlusion of the main efferent vein. Thus, it appears that a spiral placed into the graft and efferent vein is suitable to prolong the functional life of av-shunts.

Adult↗
PubMed1984

Radiological follow-up of transluminally inserted vascular endoprostheses: an experimental study using expanding spirals.

A technique for transluminal implantation of vascular endoprostheses was developed. Using a suitable instrument, 160 spiral-shaped prostheses of various forms and sizes were torsion-reduced in diameter and transluminally inserted under fluoroscopy in our study population consisting of 65 dogs and five calves. At the target, the spirals were enlarged and released from the carrier, whereupon they attached themselves to the vessel wall by elastic expansion. We implanted spirals into the vena cava or the thoracic and abdominal aorta, using the infrarenal aorta and the jugular or femoral vein for access. Angiography (the maximum follow-up was two years) demonstrated that the operation was reproducable and that it could be planned. Angiography also demonstrated that the position of the spiral prosthesis was stable and that the spiral did not lead to stenosis, thrombosis, or perforation, providing an adequate technique was used. The side branches of the main vessels remained patent, even with several spiral coils across their orifices. The method can be clinically implemented and lends itself to many applications in the vascular field.

Animals↗
PubMed1984

[Nisoldipine, a new calcium antagonist: its effect on systolic function and relaxation in the dog].

The effect of calcium-blockers on left ventricular (LV) relaxation is still a matter of debate. In 7 open-chest dogs we studied the effect of 0.01 mg/kg Nisoldipine intravenously on LV systolic function and relaxation. LV long and short axes and LV wall thickness were measured by ultrasonic crystals. LV high-fidelity pressure and aortic pressure were recorded at rest, and 2 and 30 min after i.v. Nisoldipine. Partial obstruction of the ascending aorta was performed to keep LV peak systolic pressure close to control values. LV systolic wall stress and LV ejection fraction were calculated in all dogs. The time constant of LV pressure decay (T; ms) was determined from a linear regression of LV pressure and neg. dP/dt. Heart rate and LV end-diastolic pressure remained unchanged following the administration of Nisoldipine. LV peak systolic pressure and wall stress decreased significantly 2 and 30 min after Nisoldipine but were in the normal range with partial obstruction of the ascending aorta. Max. dP/dt decreased slightly although not significantly after Nisoldipine. LV ejection fraction increased, however, significantly from 30% to 39% at 2 min and to 35% at 30 min after Nisoldipine. The time constant T increased from 27 ms to 40 ms (P less than 0.05) at 2 min and amounted to 28 ms at 30 min following Nisoldipine. It is concluded that Nisoldipine is associated with a persistent decrease of LV afterload and a transitory increase in T.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1981

Murein biosynthesis in ether permeabilized Escherichia coli starting from early peptidoglycan precursors.

ETB, ether treated bacteria, from E. coli and other Gram-negative strains, contain in a cell-free system all enzymes necessary for murein biosynthesis. Starting with a variety of combinations of peptidoglycan precursors, high yields of sodium dodecylsulfate (SDS, 4%) insoluble murein or murein like material were synthesized. The amount of newly synthesized SDS insoluble material (NSM) was dependent upon the growing phase at which cells had been harvested for preparation of ETB. This data may provide some insight into the regulation of peptidoglycan biosynthesis. Starting from early peptidoglycan precursors, the cell-free synthesis of NSM was inhibited by specific inhibitors of murein synthesis, such as D-cycloserine, D-fluoroalanine, 2-amino-ethylphosphonate, analogues of D-alanyl-D-alanine and beta-lactam antibiotics at appropriate concentrations. Some D-alanyl-D-alanine analogues and 4-chlorodiaminopimelic acid were incorporated into NSM in place of their corresponding natural substrates.

Cell Membrane Permeability↗
PubMed1978

[Groin flap plastic surgery using McGregor's method].

The specific advantages of the groin flap to the other axial pattern flaps from the trunk are outlined, followed by a detailed description of the operative procedure and the postoperative management. Based on our experience, the groin flap is an uncritical flap and can be recommended in numerous instances either of primary repair or secondary reconstruction of the injured hand.

Hand Injuries↗
PubMed1978

[Ambroxol, studies of biotransformation in man and determination in biological samples (author's transl)].

15 mg trans-4-[2-amino-3,5-dibromo-benzyl)-amino]-cyclohexanol-hydrochloride (ambroxol, NA 872) was administered i.v. and orally to healthy volunteers. The metabolic pattern in urine and plasma was similar for both routes of administration. Biotransformation reactions are straightforward, yielding two major products of phage I reactions identified as 6,8-dibromo-3-(trans-4-hydroxycyclohexyl)-1,2,3,4-tetrahydro-quinazoline and 3,5-dibromo-anthranilic acid. These metabolites as well as the parent compound are also converted to conjugates, predominantly glucuronides. Quantification of unlabelled ambroxol in biological fluids is achieved by radiochemical derivatisation with 14C-labelled formaldehyde in imitation of the biotransformation.

Administration, Oral↗
PubMed1976

Successful replantation of a hand amputated through the metacarpus.

A successful replantation is reported of a hand completely severed by a circular saw through all five metacarpals. The sequence of primary reconstruction of all important structures beginning three hours after the injury and the functional results eighteen months later are presented.

Adult↗
PubMed1975

The absorption, excretion and metabolic pattern of bromhexine in man after oral and i.v. administration.

The fate of 14C-labelled bromhexine (Bisolvon¿) in man following intravenous and oral administration was studied by investigation of the blood and plasma levels and the excretion profiles. Slight variations observed between the two administration routes are explained by the somewhat different distribution patterns resulting from the different "first path" after oral application (liver) and intravenous injection (tissues).

Administration, Oral↗
PubMedDate not supplied

Treatment of major venous obstruction with an expandable endoluminal spiral prosthesis.

Six patients with extensive iliofemoral and/or caval thrombosis were treated by thrombectomy and subsequent implantation of an expandable endoluminal spiral prosthesis in case of congenital caval stenoses (1) or extravascular compression or traction (5). Five of these patients had undergone previous surgery and thrombosis had developed despite low dose heparin given postoperatively. Three patients had had an unsuccessful thrombectomy prior to spiral implantation. No complications related to the endoluminal prosthesis occurred. There was one retroperitoneal hematoma from guide wire perforation of the inferior vena cava (IVC) necessitating laparotomy and reversal of the previously constructed femoral av-fistula with subsequent iliofemoral rethrombosis. All other endoluminally reconstructed veins remained open at early and late (up to 12 months) review confirmed by phlebography. We conclude that with increasing clinical experience endoluminal relining of obstructed major veins will probably become a valuable method of venous reconstruction with minimal surgical trauma.

Adolescent↗
PubMedDate not supplied

The helix filter: a new vena caval filter for the prevention of pulmonary embolism.

The helix caval filter is a continuous band spiral composed of a highly elastic metal alloy. A vertical double-helix coil fixes the filter in the infrarenal vena cava by elastic expansion while a watch spring type horizontal coil works as the filtering element. The diameter of the filter can be reduced by torsion from 32 to 7 mm. Transvenous implantation was performed under fluoroscopy using a newly developed instrument featuring intraoperative angiographic control, high flexibility, a guidance system, and a well-controlled release mechanism. The filter and the implantation technique were tested in a circulation system and in 10 dogs and 4 calves (follow-up 3-91 days). In addition, two filters were released intentionally into the right atrium of a dog and a calf. Flow resistance of the filter is negligible up to more than 10 1/min. Thrombi larger than 3.5 mm were filtered out reliably. Lethal complications, filter migrations or perforations did not occur in animal experiments. Filter coils which are in contact with the vessel wall become firmly incorporated within 3 to 4 weeks. The patency rate of the vena cava was 80% (8/10) for dogs and 100% (4/4) for calves. Implantations in the right atrium did not cause any symptoms. The filter's design allows fixation without hooks or spikes and consequently makes transvenous extraction possible up to 7-10 days after implantation. Comparable clinical results could extend the indications for caval filter implantation, and the decision which is still difficult today could be made easier.

Animals↗