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Biomedical subjects

G Laufer

Publications and source records attributed to G Laufer.

At least 163 records · Page 9Linked to original sources
PubMed1988

Whole blood aggregometry and platelet adenine nucleotides during cardiac surgery.

The influence of extracorporeal circulation (ECC) on human platelet adenine nucleotides has been studied in 28 coronary bypass patients before, during and after operation. An oscillating pattern of transient increases and decreases in total platelet ATP was observed following the sternotomy until the end of the operation. A highly significant increase in platelet ATP (20% +/- 14 of the pre-anaesthesia values) occurred during the first 24 h after surgery. Total platelet ADP however, did not show this oscillation nor was there any significant release of ADP from the platelets during ECC. Following collagen activation, increased amounts of 'releaseable ATP' were found after protaminization (124% +/- 38 of pre-anaesthesia values) (p less than 0.05), although whole blood aggregability was slightly reduced (89% +/- 18 of pre-anaesthesia values). This study indicates that 1) the metabolic ATP pool of circulating platelets underwent rapid changes during open heart surgery; 2) the majority of platelets did not release inert ADP during ECC; 3) there may be a compensatory enhancement of platelet function by other blood cells, which could explain the discrepancy between our aggregatory results in whole blood and those reported in platelet rich plasma (PRP) aggregometry.

Adenosine Diphosphate↗
PubMed1987

[Orthotopic heart transplantation--experiences at the University Surgical Clinic II in Vienna (status: June 1986)].

Since 1984 27 heart transplantations (HTX) were carried out in 25 patients at the 2nd Department of Surgery, University of Vienna. The classic orthotopic technique of Lower and Shumway was used in all cases. Routine immunosuppression consisted of azathioprine and cyclosporin-A. In order to treat the main complications successfully, i.e. rejection and infections, we were compelled to establish an extensive follow up regimen. The early recognition of acute rejection was based on the findings obtained by cutaneous as well as epicardial ECG leads, in conjunction with cytoimmunological monitoring on the basis of RIA measurements of the serum levels of Neopterin and gamma-Interferon. Furthermore, we recorded some parameters of ventricular performance, such as the isovolumetric relaxation time and the radiologically measured heart volume. An endomyocardial biopsy was carried out to secure the diagnosis. Pulsed doses of methylprednisolone were used for the treatment of rejection, facultatively combined with ATG in the absence of improvements. Infections were pinpointed by comprehensive serum tests and various blood, sputum and urine cultures. The management consisted of treatment with the requisite antibiotics. Of 25 primarily transplanted patients 15 patients are still alive. 5 persons, amongst them 2 children, have survived already for more than 1 year. 6 patients died at an early stage. In 3 cases the cause of death was intractable infection. In 1 case multi-organ failure occurred and 1 patient died due to acute organ failure. 4 patients died at a late stage and acute severe rejection was responsible in all these cases.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1987

Tissue precooling for thermochemical damage reduction during laser surgery.

This report describes a preliminary investigation of the possibility of reducing the thermal damage induced by lasers in the course of laser surgery. Skin incisions made by CO2 laser beams--with and without precooling--were evaluated and compared with scalpel cuts. Full thickness cuts were carried out on the flank of adult cats. Precooling was achieved by spraying chlorethyl just before the laser application. Both the precooled and the regular laser incisions were bloodless. The precooled cuts however produced considerably less amount of charring and therefore smoother and cleaner cut edge. The incisions were sutured and the cats were kept under supervision. Upon inspection four weeks later all incisions were completely healed. No skin thickening or keloid were present. The scar produced by the regular laser technique was much more pronounced and wide relative both to the scars of the precooled or the scalpel cuts which were almost alike.

Animals↗
PubMed1987

New techniques for reducing the thermochemical damage in the course of laser surgery.

New techniques were proposed for reducing the damage incurred to living tissues owing to temperature rise induced by surgical lasers. Precooling of the tissue and spatial filtering were evaluated numerically and were shown to be most effective in most surgical procedures. Application of pulse trains was also evaluated numerically and optimal operating conditions were identified.

Animals↗
PubMed1986

Laser-induced vascular lesions by cw-NdYAG or pulsed UV lasers during angioplastic procedures.

Conventional (NdYAG, Argon and CO2 lasers) laser and pulsed far ultraviolet laser radiation are able to remove arteriosclerotic tissue of the arterial wall. However, there is a striking difference between both systems: The continuous wave of conventional wave-length laser-radiation produces considerable thermal injury to the surrounding tissue, whereas the effect of pulsed far ultraviolet radiation induces less or no thermal damage despite an easily assessable tissue-removing effect. In the following study the potential of far UV laser-radiation for recanalization of occluded vessels is demonstrated in in-vitro experiments on fresh and well preserved atherosclerotic human vessels.

Animals↗
PubMed1986

Asymptotic and dimensionless analysis of the response of living tissue to surgical pulsed CO2 lasers.

The mathematical model of the interaction between the radiation of pulsed CO2 lasers and tissue was revisited. Asymptotic calculations were employed to determine upper and lower bounds for the evaporated volume and crater depth. Dimensionless time variables for conduction, beam attenuation by tissue vapors and for damage were introduced. Optimal exposure parameters were identified through a dimensionless analysis.

Biophysical Phenomena↗
PubMed1985

[Qualitative and quantitative effects of neodymium YAG laser irradiation of the aortas of swine with reference to angioplasty].

During last few years the concept of vaporizing atheromatous plaques and thrombotic occlusions by laser energy arose. This method is a new and possibly valuable modality in the treatment of obstructive vascular diseases. We used a continuous 1,060 nm Nd-YAG laser with a focused optical wave guide. Sections of porcine aortic vessels were split longitudinally and exposed to laser radiation. Four major types of tissue alterations were observed: local swelling, disruption of the inner layers of the vessel wall, charred punched-out defects and wall perforation. Histologic examination revealed a typical damage pattern as a result of thermic injury. Clean tissue alteration is the desired effect for angioplasty. The thermic alterations limit the applicability when dealing with the cw Nd-YAG laser for this purpose.

Animals↗
PubMed1985

Plasma fibronectin, albumin, IgM and total protein during cardiopulmonary bypass.

Plasma concentrations of fibronectin, albumin, total protein and IgM were measured in 14 male patients undergoing aorto-coronary bypass operations. Fibronectin and IgM concentrations fell to 55% of the preoperative values 5 minutes after start of the extracorporeal circulation, and the same percentages were encountered 5 minutes after the termination of bypass. The concentrations had recovered to 75% of the preoperative values by the end of the operation. The plasma concentration of albumin was 68 +/- 9% of the preoperative value after 5 minutes of bypass, 66 +/- 7% at the end of bypass, and 83 +/- 9% of the end of operation (significantly different from fibronectin and IgM, p less than 0.05; Wilcoxon's test for paired differences). No correlation was found between the duration of extracorporeal circulation and the post-bypass concentrations of any protein (Kendall correlation). It is concluded that the fall of fibronectin concentrations during cardiopulmonary bypass can be sufficiently explained by dilution, and that a specific consumption of fibronectin does not occur. The less marked decreases of albumin and total protein were probably due to infusion of plasma-protein solution, which is poor in fibronectin and IgM.

Adult↗
PubMed1985

The response of living tissue to pulses of a surgical CO2 laser.

The response of living tissue to surgical lasers was studied numerically. An algorithm computed the crater boundaries formed by a single laser pulse and the thermochemical damage around this crater. Heat conduction and beam attenuation by tissue vapors were found to be the major factor in the reduction of cutting efficiency.

Carbon Dioxide↗
PubMed1985

Experimental coronary angioplasty using a UV-Excimer laser.

Both conventional Argon- and NdYAG-lasers in continuous wave or pulsed application and far ultraviolet laser radiation are able to cause a loss of substance of biologic tissue. The thermic and ablative effects of NdYAG-lasers and UV-Excimer lasers at the wavelengths of 193 nm (ArF) and 248 mm (KrF) on inconspicuous and atherosclerotic human and animal coronary vessels were compared by histologic and, in some cases, by scanning electron microscopic examinations. Whereas common lasers generally produce thermal injuries of the surroundings, pulsed far ultra-violet radiation is characterized by a lack of thermic damage. The UV-radiation in vitro cleaned precise defects of substance, and assessable tissue-removing effects were found. These results were influenced by the wavelength used. In general, the removing effect was good in normal and atherosclerotic tissue, whereas massive calcification was very resistant. Excimer lasers seem to be preferable for ablation of atherosclerotic tissue, but still there is a great number of technical problems to be solved until use in the clinical setting can be justified.

Journal Article↗
PubMed1985

[Coronary laser angioplasty].

Experimental studies have confirmed the feasibility of removing thrombotic material and atheromatous plaques with laser energy. Secondary to the heat generated at the site of conventional, continuous-wave laser radiation, thermic lesions of the vascular wall can be observed as adverse reactions. In the clinical setting, these lesions could prove to be of substantial potential danger. The energy emitted from the excimer laser, in the lower UV range, does not result in thermic damage. The luminal widening rendered is well delineated and the newly-created surfaces are relatively smooth. The extent of ablation is highly predictable. Problems dealing with transmissions of the UV laser energy remain to be solved. Nevertheless, high-energy, pulsed NdYAG- or argon laser systems, at least for medium-term periods, would appear to represent a useful alternative.

Angioplasty, Balloon↗
PubMed1984

Measurement of the laser exposure levels for burn threshold in biological tissue.

Experiments for the evaluation of the laser energy density required to induce burn threshold in biological tissue are presented. The results are compared with a theoretical model. The values obtained for soft tissue are higher than the pain threshold and the safety standards for the maximum permissible exposure. This is due to the different nature of injury associated with the surgical process.

Biomedical Engineering↗
PubMedDate not supplied

The electrophysiology of cardiac allograft rejection: independent effects of rejection and perioperative ischemia on the sinus node recovery phenomenon after cardiac transplantation.

We characterized the effect of cardiac allograft rejection on the sinus node (SN) recovery response from overdrive suppression. A total of 54 corresponding data sets (SN recovery time [SNRT]/endomyocardial biopsy [EMB]) was available in 24 transplant recipients with normal SNRT. Data were pooled in the rejection vs the no-rejection group (n = 16 vs n = 38, respectively). During cardiac rejection (defined as a 7-day period starting 3 days prior to and lasting until 3 days after the EMB) the SNRT curves were moderately, but significantly shifted towards higher values (F = 13.4, p = .0003). All changes occurred within accepted normal limits for the SNRT. Multivariate analysis indicated independent effects of donor heart ischemic time (p = .0005) on SNRT in addition to that of rejection. After accounting for that influence of ischemic time respective F values regarding the influence of rejection on the SNRT excursions were 10.8 (ischemic time < 100 min, p = .0014) and 4.36 (ischemic time > or = 100 min, p = .039). This study shows that cardiac allograft rejection significantly delays the SN recovery response from overdrive suppression. These changes, however, are subtle and, hence, are an unlikely explanation for the often grossly abnormal postoperative SN function.

Adolescent↗