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Biomedical subjects

F Unger

Publications and source records attributed to F Unger.

144 records · Page 8Linked to original sources
PubMedDate not supplied

Serial magnetic resonance imaging evaluation of a bioabsorbable interference screw and the adjacent bone.

The purpose of this prospective study was to review, using expanded clinical assessment tools, the initial use of a bioabsorbable interference screw (copolymer 85/15 D, L lactide/glycolide) in anterior cruciate ligament (ACL) reconstruction at the Wels Hospital, Austria. The study enlisted 32 patients of whom 28 were available for follow-up at minimum of 2.5 years. Since the implant material was new and the screw would not show on plain film radiographs, the clinical assessment was expanded beyond the usual historical and physical findings. The evaluation included opportunistic knee joint aspiration and repeat magnetic resonance imaging (MRI) studies to investigate the longevity of the implant and potential adverse effects of this new bioabsorbable material. The knee joint aspirations showed no infection. Serial MRIs showed the physical presence of the screw to remain intact for 4 months and disappear in 6 months. The MRIs showed minimal collection of edema around the bone tunnels that resolved by 12 months. There were no symptoms or adverse clinical result correlated with the MRI evidence of edema. There was temporary bone tunnel expansion. The clinical results were good. The OAK-score (Orthopädische Arbeitsgruppe Knie) showed 89.5% excellent and good results, 7% fair results and 3.5% poor results. The average score was 90.7 points (range, 63 to 100 points). The knee joint stability measured with the KT-1000 arthrometer showed 93% to have a 3-mm or less difference compared with the unoperated knee. This bioabsorbable interference screw appeared safe and effective for fixation of bone blocks during ACL reconstruction while producing no occult infection or adverse clinical response during the degradation process.

Absorbable Implants↗
PubMedDate not supplied

Perioperative immunoglobulin E response to coronary artery bypass grafting.

Serial estimation of total immunoglobulin E (IgE) concentration in 30 consecutive male patients undergoing coronary artery bypass grafting revealed three patterns--a low, middle and high response--during the perioperative period. The mean IgE level was higher in patients with higher mean preoperative left ventricular ejection fractions and these patients had a higher left ventricular stroke work index. However, there was no correlation with the severity of coronary artery disease or with degree of adequacy of revascularisation. Mean IgE level correlated moderately well with the mean right ventricular stroke work index and mean pulmonary capillary wedge pressure and minimally with the triple index. A higher level of IgE was usually observed with better cardiac performance and may be associated with factors related to the pulmonary circulation. However we could neither confirm nor refute whether an elevated level of IgE indicated an increased risk of cardiovascular events or a "protected status" against the complications of necrotising ischemia.

Adult↗
PubMedDate not supplied

Intestinal ischemia associated with cardio-pulmonary-bypass surgery: a life threatening complication.

Intestinal ischemia following open heart surgery is rare but nevertheless extremely dangerous and the causes are still unclear. The purpose of this study was to evaluate the factors influencing the occurrence and outcome of patients with this complication. At our institution between 1985 and 1989 1712 patients underwent open heart surgery and 4 female patients suffered from intestinal ischemia. The early mortality was 2.5% for the whole group and 100% for the group with intestinal ischemia. All these 4 patients were elderly and had a history of hypertension and hyperlipoproteinemia. Three of the four patients with intestinal ischemia had various risk factors for thromboembolic events such as pre-existing occlusive arterial disease and cardiac dysrhythmias or had a complicated postoperative course. In two patients an enormous increase in serum lactate to over 10 mmol/l occurred prior to the intestinal ischemia. We therefore consider advancing age, female gender and a susceptibility for thromboembolic events as important risk factors for the development of intestinal ischemia. A serum lactate over 10 mmol/l should lead to an aggressive diagnostic and therapeutic approach including exploratory laparotomy.

Aged↗
PubMedDate not supplied

Functional heart replacement with the spindle pump: first results.

The spindle pump is a nonpulsatile blood pump with a double function, i.e., it works centrifugally and represses simultaneously. The first experiences with this type of pump used as a biventricular assist device in four short-term animal experiments (up to 13 hours) are described. It can be demonstrated that in cases of a normally beating heart, this BVAD decompresses both ventricles by 60-70%, while the aortic pressure is slightly increased; on the other hand, in case of ventricular fibrillation, the BVAD with two spindle pumps maintained the entire circulation, at an arterial pressure between 80 and 90 mmHg with a flow volume between 3.5 and 4 L/min.

Animals↗
PubMedDate not supplied

The spindle pump. Development of a nonpulsatile blood pump for assisted circulation.

The spindle pump is a combined working nonpulsatile blood pump, i.e., a centrifugally propelling device. This special concept was chosen to tackle the main problems of nonpulsatile pumps, such as thromboembolic complications, sealing difficulties, and traumatic hemolysis. The first two of these problems were relatively simple to solve compared with the third problem--traumatic hemolysis. Various modifications and constructive steps of the spindle pump were necessary to keep stress on blood components within adequate limits. The actual prototype--tested in three acute experiments and eight experiments with a longer pumping duration (the longest lasting 63 hours)--is described in extenso, and its development is discussed.

Animals↗
PubMedDate not supplied

A new hydraulic heart assist device.

For the right drive of a hydraulic biventricular assist device (HBVAD), a new lightweight magnet with a permanent magnetic armature was constructed. A miniature optically incremental position sensor was developed, which is an integral part of the control loop of the driving unit, and was incorporated in the armature. Mock circulation tests proved the stability of the drive and showed the expected sensitivity to the preload pressure. In vivo experiments in calves were carried out in order to test its haemodynamic efficiency on a beating and on a fibrillating heart, and to test the mutual interaction of the left and right hydraulic assist devices (LVAD, RVAD) via the vascular system. Both drives were controlled independently, operating in the volume-controlled mode. For the modelling of a heart disease, the heart was blocked by the administration of verapamil (Isoptin). It could be shown that the HBVAD is able to maintain the circulation. Various tests with the left and/or right drive active showed distinct unloading effects for the natural heart and proved the mutual interaction of both drives via the vascular system. An inherent feature of the hydraulic drive system is its ability to be triggered by a (weakly) beating heart. The preload sensitivity of the HBVAD was tested by the administration of adrenaline. Similar reactions of the drives resulted for a beating and for a fibrillating heart, showing the regulation characteristic according to Starling's law.

Animals↗
PubMedDate not supplied

Artificial heart driven by an automatic driving system.

Thrombi formation within artificial ventricles is caused by the effects of biomaterials, stagnation areas, and major turbulences. During systolic and diastolic cycles, stagnation area increase in hearts that are properly designed. Stagnation areas may also occur in properly designed artificial hearts that are not working with a maximum stroke volume. The ellipsoid heart avoids stagnation areas and major turbulences because all the inside surfaces have an adequate washout with blood. The optimum washout of these surfaces is obtained by driving the heart with a constant maximum stroke volume. The cardiac output is regulated according to Starling's law by adjusting the frequency according to the venous return.

Animals↗
PubMedDate not supplied

The Windkesselventricle with guiding balloon as a new approach for assisted circulation.

A simple method was developed to aid the patient with low cardiac output syndrome following cardiac surgery. The concept was shown to be feasible in electric circulatory analog studies and verified in 20 dog experiments. A Dacron graft (end-to-side) through the right second intercostal space connects the ascending aorta to the subcutaneously implanted, ellipsoidal-shaped artifical ventricle. A spherical polyurethane balloon is positioned in the aorta distal to the Dacron graft via the femoral artery. The ventricle and balloon are pneumatically driven synchronously with the ECG. In natural systole the balloon is inflated, occluding the aorta, and the artificial ventricle sucks the entire stroke volume. In natural diastole the balloon deflates and the artificial ventricle ejects the blood into the peripheral arteries. With this system it is possible to maintain a normal systemic pressure and have high hemodynamic efficiency. The left ventricular systolic pressure is 85 percent unloaded. The systolic wave is turned 180 degrees to the natural. After treatment, the device can be removed without thoracotomy.

Animals↗