Biomedical subjects

W Trubel

Publications and source records attributed to W Trubel.

At least 19 recordsLinked to original sources

PubMed2004

Experimental comparison of four methods of end-to-side anastomosis with expanded polytetrafluoroethylene.

BACKGROUND: Four established techniques of distal end-to-side anastomosis (direct anastomosis, Linton patch, Taylor patch and Miller cuff) were compared to investigate the local distribution of anastomotic intimal hyperplasia. The study aimed to elucidate whether mechanical factors or flow alterations are mainly responsible for the improved patency rates reported for vein cuff interposition techniques in infrainguinal arterial reconstructions using prosthetic graft material. METHODS: Thirty-two expanded polytetrafluoroethylene (ePTFE) femoropopliteal bypass grafts were implanted in 16 sheep using the four anastomotic techniques. After 6 months the grafts were explanted and examined histologically. The local distribution of intimal hyperplasia was determined, particularly for areas of material transition and of high and low shear stress. RESULTS: The mean amount and distribution of intimal hyperplasia were similar for all anastomotic types. Intimal hyperplasia was greatest along all transitions between ePTFE and venous patches, and between ePTFE and recipient artery. It was lower along the transitions between venous patches and artery, and was lowest at the host artery floor. CONCLUSION: Vein interposition did not reduce anastomotic intimal hyperplasia and did not change the distribution patterns of hyperplasia, which were influenced mainly by mechanical factors. The effect of vein interposition is to move areas of maximum intimal hyperplasia away from the small recipient artery up to the more capacious graft-patch anastomosis.

Anastomosis, Surgical↗

PubMed2004

Limb-salvage by femoro-distal bypass and free muscle flap transfer.

OBJECTIVES: To evaluate the feasibility and long-term outcome of distal arterial reconstruction combined with free muscle flap transfer for patients who would otherwise have undergone major amputation. METHODS: Between 1996 and 2001, 27 reconstructions using autologous vein were performed in 25 patients. Seventeen of these patients had diabetes mellitus. Gracilis, rectus abdominis and latissimus dorsi muscles were used as free flaps, covered with split-thickness skin grafts. RESULTS: Eighty-five percent of patients had a patent graft and viable muscle flap after 1-month. Mean follow-up was 51 months (4-72 months). At the time of follow-up 77% of reconstructions were patent and 70% of patients regained full functional capacity of their lower extremities. CONCLUSION: Limb-salvage by distal arterial reconstruction and free muscle flap transfer, is feasible with low mortality and morbidity and provides excellent long-term results with regard to graft patency and functional status.

Arteriovenous Shunt, Surgical↗

PubMed2002

Streptococcus pneumoniae mycotic aortic aneurysm after allogeneic bone marrow transplantation.

BACKGROUND: Streptococcus pneumoniae (SP) is a common cause of community-acquired pneumonia and accounts for up to 30% of all cases of pneumonia. Patients with chronic graft-versus-host-disease (GvHD) after allogeneic bone marrow transplantation (BMT) have a high susceptibility to SP infections. So far, mycotic aneurysm resulting from SP has not been reported after BMT. METHODS: We report on a patient with extensive, chronic GvHD who developed low back pain 22 months after allogeneic BMT. RESULTS: Computed tomography of the abdomen displayed mycotic, saccular aneurysmatic enlargement of the infrarenal aorta, with leakage of contrast medium into the aneurysm. The aneurysm was resected, and the defect was closed with an autologous patch from the internal iliac artery. Bacteriologic samples from the abscess grew SP. The patient recovered uneventfully. CONCLUSIONS: This observation confirms the importance of pneumococcal prophylaxis after BMT and suggests that an aggressive diagnostic approach should always be considered in patients with chronic GvHD, even if they present with nonspecific symptoms.

Adult↗

PubMed2000

Collagen patch coated with fibrin glue components. Treatment of suture hole bleedings in vascular reconstruction.

BACKGROUND: Bleeding from suture holes during vascular reconstruction, particularly when polytetrafluoroethylene (PTFE) prostheses are used, is still a problem which can lead to intraoperative delay and increased blood loss. The aim of this prospective, randomised, open, controlled multicentre study was to evaluate whether the use of a new local haemostyptic would reduce intraoperative blood loss and the time to haemostasis. METHODS: Thirty patients received a new haemostyptic (TachoComb H, Nycomed Pharma AG), whereas another 30 patients were treated with compresses. The vascular reconstructions were either anastomoses or patch angioplasties and were performed using PTFE vascular prostheses. RESULTS: The mean time to haemostasis of suture hole bleeding in the haemostyptic group (326.0 sec) was significantly shorter compared to the control group (514.3 sec) (p=0.006). The median intraoperative blood loss was 24.5 g in the treatment group and 57.3 g in the control group (p=0.045). CONCLUSIONS: It was shown that collagen patches coated with components of fibrin glue significantly reduce the time to haemostasis as well as blood loss at the operation site in patients undergoing vascular reconstruction with PTFE grafts.

Aged↗

PubMed2000

[Abdominal vascular surgery emergencies: abdominal aortic aneurysm, acute mesenteric ischemia--indications, technique, results].

Ruptured infrarenal aortic aneurysms and mesenteric ischemia are abdominal emergency situations, which should be treated by vascular surgeons. Modern means of patient transport and specialized emergency centers make it possible to bring patients suspect of having a ruptured aneurysm or a mesenteric ischemia to experienced clinics. Indication for surgery in case of symptomatic or ruptured aortic aneurysms is doubtless absolute. If there is suspicion for a ruptured aneurysm, emergency operation is indicated. In patients having undergone emergency surgery for a ruptured aneurysm of the infrarenal aorta, hospital mortality was 41%. The initial indication for surgery for patients with mesenteric ischemia usually is the "acute abdomen". Mostly only the patient's history reveals the suspicion for this disease. There are no valid radiologic examinations for proving or ruling out mesenteric ischemia. Most of our patients had arterial embolism (64%) as a source of mesenteric ischemia, followed by arterial thrombosis (28%), venous thrombosis (3%) and non-occlusive ischemia (5%). Monitoring of levels of serum lactate can be an additional tool for decision making, if a second look operation is discussed. The key for surgical success with these critically ill patients is shortening of the interval between the first symptoms of the patient and the start of surgical therapy.

Aged↗

PubMed1999

Detection of Chlamydia pneumoniae DNA in atheromatous tissues by polymerase chain reaction.

Chlamydia pneumoniae is an important human respiratory pathogen. Recently, seroepidemiological data and the demonstration of chlamydial DNA or antigen within parts of atherosclerotic lesions have suggested a causal association between chlamydial infections and atherosclerosis. As the results obtained by different groups show considerable variations, we provide further data based on a highly specific and sensitive nested PCR method. Positivity was confirmed by nonradioactive hybridization with a specific probe, and sensitivity was determined by titration experiments. C. pneumoniae DNA was detected in 8/29 (28%) of carotid artery samples and 3/14 (21%) of aortic aneurysms.

Aged↗

PubMed1999

Evaluation of distal anastomotic intimal hyperplasia: an experimental comparison by arteriography, duplex sonography, angioscopy, and intravascular ultrasound.

Routine follow-up investigation methods after peripheral arterial bypass surgery, such as arteriography and colour duplex sonography, do not always allow correct analysis of moderate alterations in the vessel wall, e.g. initial stages of distal anastomotic intimal hyperplasia (DAIH). The aim of this study was to evaluate the efficiency of angioscopy and intravascular ultrasound compared to the named routine methods regarding detection of early DAIH. Eight months after bilateral femoropopliteal bypass surgery with venous grafts in 18 sheep, we investigated the distal anastomotic sites using the named methods. The findings were then correlated to histologic specimens. Intravascular ultrasound presented the highest sensitivity followed by angioscopy, with results markedly different from the findings arrived at by conventional methods.

Anastomosis, Surgical↗

PubMed1997

Intraoperative and early postoperative colour Doppler sonography after carotid artery reconstruction: follow-up of technical defects.

We studied 50 patients with intraoperative colour-coded Doppler sonography (CCDS) after carotid artery reconstruction. Technical defects could be detected in 19 cases (38 %): residual plaques in 9, flaps in 8 and strictures in 2. In 9 cases (18 %) the carotid endarterectomy was revised. One residual plaque and one residual stricture caused thrombosis at the operative site a few hours postoperatively. One of the patients with residual plaques developed a high-grade stenosis within the follow-up period. Of the patients with residual plaques two had a medium-grade stenosis at follow-up. Six flaps decreased in size or disappeared within 1 week after operation. No patient with a flap developed a stenosis within the follow-up period. Our findings seem to indicate that correction of intimal flaps less than 10 mm in size is not necessary.

Aged↗

PubMed1997

Endovascular AAA treatment: expensive prestige or economic alternative?

OBJECTIVES: To compare the costs of endovascular aneurysm treatment versus open surgery during the perioperative period. METHODS: Retrospective analysis of a consecutive series of 44 patients undergoing infrarenal abdominal aneurysm repair from February 1995 to March 1996 at a university teaching hospital. RESULTS: No endovascular procedure was converted to open repair. Operative time was shorter for endovascular treatment (207.6 min vs. 229.1 min, n.s.), as well as postoperative intensive care unit stay (ICU, 22.7 h vs. 55.0 h, p = 0.017) and the postoperative recovery period (5.6 days vs. 13.3 days, p < 0.001). Open surgery generated significantly more costs (25,374.07 ECU vs. 22,268.78 ECU, p < 0.001), despite evaluation and a more expensive endovascular procedure (10,699.48 ECU vs. 4032.01 ECU, p < 0.001). During the study, costs for open surgery exceeded the cost for endovascular treatment by 13.95%. CONCLUSIONS: Endovascular aneurysm treatment is cost effective and less expensive than open surgery. The main reason for cost saving is faster patient recovery after surgery, associated with a shorter LOS in the patients treated with endovascular procedure.

Aged↗

PubMed1997

The contribution of extracranial blood oxygenation on near-infrared spectroscopy during carotid thrombendarterectomy.

To determine the contribution of extracranial oxygenation on regional cerebral oxygenation measured by an Invos 3100 near-infrared spectrometer, we measured oxygenation in blood drawn from both the facial vein (draining substantially blood from forehead areas) and the jugular venous bulb. There was no correlation between regional cerebral oxygenation and facial vein oxygenation (p = 0.35) but there was a significant correlation between regional cerebral oxygenation and jugular venous bulb oxygenation (p = 0.027). Linear regression analysis predicted a 3.6% change in regional oxygenation for every 10% change in jugular venous bulb oxygenation. We showed that extracranial tissue oxygenation had a negligible influence on the values recorded using near-infrared spectroscopy. Individual changes in jugular venous bulb oxygenation were poorly reflected. Data obtained by this near-infrared spectroscopy device are an unreliable guide to the adequacy of cerebral oxygenation.

Adult↗

PubMed1997

[Abdominal aortic aneurysm: surgery, indications, technique, outcome].

The fate of a patient with an abdominal aortic aneurysm] (AAA) is influenced by the risk of rupture and embolism. When the indication for operation is considered, individual associated risk factors have to be taken into account. With regard to the literature, the following recommendations concerning indication for surgery can be given: emergency surgery for symptomatic or ruptured aneurysm; elective surgery: aneurysms 5 cm diameter or growing AAA 5 mm/year, patient with acceptable individual risk for operation; asymptomatic aneurysms less than 5 cm in diameter, without growth in patients aged over 75 years and/or considerable perioperative risk should not be operated on: sonography should be done 3-monthly as a continuing control. Finally the results in our institution are presented for elective surgery: 30-day mortality 3.5%, AAA with rupture, no shock: 20%, ruptured AAA with shock 47%, respectively.

Aortic Dissection↗

PubMed1997

[Acute mesenteric ischemia].

UNLABELLED: Acute mesenteric ischemia is a life-threatening vascular emergency. A retrospective analysis of our patients was performed to describe the development of the various procedures of diagnostic assessment and treatment between 1970 and 1996, to show the influence on survival and to define recent standards. PATIENTS: Between 1970 and 1996, 145 patients, 75 male and 70 female, suffering from acute mesenteric ischemia, have been treated at the Department of Surgery-University Hospital Vienna. RESULTS: In most cases AMI was caused by arterial embolism (64.1%, n = 93) followed by arterial thrombosis (27.6%, n= 40). Venous thrombosis (3.5%, n = 5) and non-occlusive AMI (4.8%, n = 7) were rare events. Serum lactate level has been determined routinely in all patients having been admitted with acute abdomen since 1984 and turned out to be positive in 81.2% (mean value 9.81 (3.21-22.3) mmol/l). Abdominal x-ray gave only in some individual cases special hints to the advanced intestinal gangrene. Abdominal sonography led to the correct diagnostic assessment in 52 patients (= 35.8%). Angiography was in 92% conclusive for the diagnosis. Abdominal CT led to establish the correct diagnosis in > 80%. Our series with revascularisation (thrombectomy/embolectomy or bypass) has resulted in 73.8% patient survival with intestine having been maintained in the most favourable cases. CONCLUSIONS: Early diagnostic assessment and treatment are decisive for survival. Abdominal-CT, angiography and serum-lactate constitute quick and reliable means to provide diagnosis and to judge the stage of AMI in addition to meticulous examination of patients' history, symptoms and physical conditions.

Acute Disease↗

PubMed1996

Numerical study of wall mechanics and fluid dynamics in end-to-side anastomoses and correlation to intimal hyperplasia.

In order to analyse the wall mechanics and the flow dynamics in compliant vascular distal end-to-side anastomoses, computer simulation has been performed. In a model study the effect of compliance mismatch on the wall displacements and on the intramural stresses as well as the influence of wall distensibility on the flow patterns are demonstrated applying two distensible models with different graft elasticity. In addition, the flow in a rigid model simulating a vein graft without adaption of the venous lumen has been investigated. The geometries for these models were obtained from a concurrent experimental study, where the formation of distal anastomotic intimal hyperplasia (DAIH) was studied in untreated and externally stiffened autologous venous grafts in sheep. In the flow study the time-dependent, three-dimensional Navier-Stokes equations describing the motion of an incompressible Newtonian fluid are applied. The vessel wall is modelled using a geometrically non-linear shell structure. In an iteratively coupled approach the transient shell equations and the governing fluid equations are solved numerically using the finite element method. In both compliant models maximum displacement and areas of steep stress gradients are observed in the junction region along the graft-artery intersection. The comparison of the normal deformations and the distribution and magnitude of intramural stress shows quantitative differences. The graft elasticity acts as a regulating factor for the deformability and the stress concentration in the junction area: In the model with high graft-elasticity maximum normal deformation at the side wall is 17%. This is twice as large as in the stiff graft model and maximum principle stress at the inner surface differs by one order of magnitude. The numerical results concerning the flow patterns indicate strongly skewed axial velocity profiles downstream of the junction, large secondary motion, flow separation and recirculation on the artery floor opposite the junction and at the inner wall downstream of the toe. In these regions a correlation between the time-averaged fluid wall shear stress and intimal thickening found in the animal experiment can be observed, whereas the pronounced formation of DAIH at the suture line seems to be mainly dependent on wall mechanical factors such as intramural stress and strain.

Adaptation, Physiological↗

PubMed1996

Coefficient of variation: a powerful Doppler ultrasonographic parameter for detection of renal artery stenosis.

The aim of our study was to objectively compare the effectiveness of various Doppler parameters in the diagnosis of renal artery stenosis. In three sheep, variable degrees of renal artery stenosis were induced and renal segmental arteries were investigated using pulsed Doppler sonography. In each animal the standard deviation of the instantaneous peak velocity within one cardiac cycle normalized by the mean peak velocity (coefficient of variation) had significantly higher normalized regression coefficients (k* = -0.215, average of three animals) when compared to resistive index (k* = -0.090) and acceleration index (k* = -0.069). In each individual animal, coefficient of variation detected lower pressure gradients (6.3 mm Hg, average value) than did resistive index (13.4 mm Hg) or acceleration index (17.3 mm Hg). The coefficient of variation may detect the presence of pressure gradients in renal artery stenosis more accurately than acceleration index or resistive index.

Animals↗

PubMed1995

Compliance mismatch and formation of distal anastomotic intimal hyperplasia in externally stiffened and lumen-adapted venous grafts.

OBJECTIVE: Compliance and formation of distal anastomotic intimal hyperplasia (DAIH) were investigated in externally stiffened venous grafts of varying calibers. METHODS: 36 femoropopliteal reconstructions were performed in 18 sheep. The autologous venous grafts were inserted into tubes made of Dacron mesh to achieve compliance-mismatch and lumen adaptation. Compliance was measured by echotracked ultrasonography and profiles of DAIH were generated from histologic sections harvested after 8.3 months. MAIN RESULTS: The external mesh tube significantly lowered the local compliance of graft and host artery. DAIH appeared extensively in those groups where mesh tube constricted venous grafts met untreated host arteries (p = 0.002). No differences in compliance and DAIH formation were observed when grafts with large and adapted diameters were compared. CONCLUSIONS: For prevention of DAIH the distal venous graft diameter is not important, while the local compliance of an autologous vein is a predictive factor for DAIH formation and thus long-term patency.

Anastomosis, Surgical↗

PubMed1995

Recovery of intraoperatively shed blood in aortoiliac surgery: comparison of cell washing with simple filtration.

To regain blood shed intraoperatively, two different systems are clinically established: washing and centrifuging red blood cells to produce autologous erythrocyte concentrates and devices for immediate reinfusion of whole blood after mere filtration. In a prospective-randomised study to compare both methods regarding their efficiency, adverse effects, and economy, 20 patients of our department undergoing elective aortoiliac surgery received intraoperative autotransfusion by means of either cell-washing (CS) or salvage of whole blood (WB). Patients were preoperatively randomized into one of the two groups and were evaluated with respect to standard metabolic and haematological laboratory parameters preoperatively, during surgery, after transfer into the recovery room, 24 h after surgery, after transfer into the recovery room, 24 h after surgery, and at discharge. Both patient groups were well comparable in demographics, preoperative laboratory data, and indication for operation. Handling was easier, the set-up time was shorter with the whole blood filtration device (10.2 +/- 2.3 versus 21 +/- 1.9 min, p = 0.0023), and no additional personnel was needed to run the system. The whole blood device also allowed a greater percentage of aspirated blood to be returned intraoperatively compared to cell washing (73.5% +/- 7.2 versus 51.1% +/- 6.5, p = 0.03). Thrombocytopenia occurred in 7 (CS) and 3 (WB) patients intraoperatively with a significant difference in platelet count between the two groups (118 +/- 17 [CS] versus 170 +/- 12 [WB]*10(9)/L, p = 0.025). Expected changes in the perioperative course of the clotting parameters such as highly increased PTT levels and moderately prolonged prothrombin times occurred in all cases.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗

PubMed1995

An implantable seal-less centrifugal pump with integrated double-disk motor.

Thrombus formation and sealing problems at the shaft as well as the compact and efficient design of the driving unit have been major difficulties in the construction of a long-term implantable centrifugal pump. To eliminate the problems of the seal, motor size, and efficiency, two major steps were taken by modifying the Vienna implantable centrifugal pump. First, a special driving unit was developed, in which the permanent magnets of the motor themselves are used for coupling the force into the rotor. Second, the rotor shaft in the pumping chamber was eliminated by adopting a concept recently presented by Ohara. The rotor is supported by 3 pins, which run on a carbon disk, whose concave shape leads to stabilization. The device has the following specifications: size: 65 mm (diameter) by 35 mm (height), 101 cm3; priming volume 30 cm3, 240 g; and a 6-pole brushless double disk DC motor. The required input power of the described prototype is 15 W at 150 mm Hg, 5 L/min (overall eta = 11%), and has an in vitro index of hemolysis (IH) of 0.0046 g/100 L. The test for in vitro thrombus growth exhibited far less thrombus formation in the new design than in designs with axles. In conclusion, the design of a special driving unit and the elimination of the axle led to the construction of a small pump with very low blood traumatization.

Biomechanical Phenomena↗

PubMed1995

Intrarenal Doppler ultrasonography: which vessel should be investigated?

The aim of our study was to determine whether the site of intrarenal Doppler measurement influences diagnosis of renal artery stenosis. In an experimental test, three sheep with variable degrees of renal artery stenosis were investigated. In each animal, the resistive index from renal segmental arteries correlated better with mean pressure gradient (r = 0.85, 0.71, 0.85) and had lower standard deviation (s = 0.02 to 0.05) than resistive index from interlobar arteries (r = 0.48, 0.54, 0.61) (s = 0.03 to 0.11). In two animals the difference was significant (correlation: P < or = 0.01, P = 0.13, P < or = 0.05; standard deviation: P < or = 0.01, P < or = 0.34, P < or = 0.05). For detecting renal artery stenosis, vessels within the renal sinus should be used for Doppler sampling.

Animals↗