PubMed Health⌕ Search

Biomedical subjects

B Ott

Publications and source records attributed to B Ott.

At least 19 recordsLinked to original sources
PubMed2001

Laser solder welding of articular cartilage: tensile strength and chondrocyte viability.

BACKGROUND AND OBJECTIVE: The surgical treatment of full-thickness cartilage defects in the knee joint remains a therapeutic challenge. Recently, new techniques for articular cartilage transplantation, such as mosaicplasty, have become available for cartilage repair. The long-term success of these techniques, however, depends not only on the chondrocyte viability but also on a lateral integration of the implant. The goal of this study was to evaluate the feasibility of cartilage welding by using albumin solder that was dye-enhanced to allow coagulation with 808-nm laser diode irradiation. STUDY DESIGN/MATERIALS AND METHODS: Conventional histology of light microscopy was compared with a viability staining to precisely determine the extent of thermal damage after laser welding. Indocyanine green (ICG) enhanced albumin solder (25% albumin, 0.5% HA, 0.1% ICG) was used for articular cartilage welding. For coagulation, the solder was irradiated through the cartilage implant by 808-nm laser light and the tensile strength of the weld was measured. RESULTS: Viability staining revealed a thermal damage of typically 500 m in depth at an irradiance of approximately 10 W/cm(2) for 8 seconds, whereas conventional histologies showed only half of the extent found by the viability test. Heat-bath investigations revealed a threshold temperature of minimum 54 degrees C for thermal damage of chondrocytes. Efficient cartilage bonding was obtained by using bovine albumin solder as adhesive. Maximum tensile strength of more than 10 N/cm(2) was achieved. CONCLUSIONS: Viability tests revealed that the thermal damage is much greater (up to twice) than expected after light microscopic characterization. This study shows the feasibility to strongly laser weld cartilage on cartilage by use of a dye-enhanced albumin solder. Possibilities to reduce the range of damage are suggested.

Animals↗
PubMed2001

Comparative in vitro study of tissue welding using a 808 nm diode laser and a Ho:YAG laser.

In vitro porcine arteries and veins have been welded end-to-end using either a 808 nm diode laser combined with an indocyanine green enhanced albumin solder, or with a continuous-wave (cw) Ho:YAG laser without biological solder. The vascular stumps were approached to each other over a coronary dilatation catheter in order to obtain a precise alignment and good coaptation. Standard histology revealed for both welding techniques lateral tissue damage between 2 and 3 mm caused by laser-induced heat. Good solder attachment to the tissue was observed by the use of a scanning electron microscope. The vessels soldered with the 808 nm diode laser using albumin solder showed considerably higher tensile strength (1 N compared to 0.3 N) than vessels welded exclusively by Ho:YAG laser radiation. In contrast, leaking pressure (350 +/- 200 mmHg) and bursting pressure (457 +/- 200 mmHg) were found to be independent of the welding technique used. This study demonstrates that fast (total welding time about 2-5 min), stable and tight microvascular anastomosis can be achieved with the use of a dye-enhanced albumin laser soldering technique and an ancillary coronary dilatation catheter.

Anastomosis, Surgical↗
PubMed2001

Internal limiting membrane ablation in pig eyes with the Er:YAG laser under perfluorodecalin.

PURPOSE: The aim of our study was to evaluate the in vivo feasibility of non-contact Er:YAG laser ablation of the internal limiting membrane (ILM), which is recommended for the treatment of macular holes. METHOD: Vitrectomy was performed in 16 eyes of 15 pigs. After perfluorodecalin filling, it was attempted to remove the ILM using a free-running fiber-guided Er:YAG laser (lambda=2.94 microm, pulse length 250 micros, repetition rate 1.7 Hz, radiant exposure 0.6-2.05 J/cm2). The eyes were enucleated either immediately (11 eyes, group 1) or 2 weeks after laser therapy (5 eyes, group 2). Furthermore, in one additional pig eye the retina was carefully treated with microforceps after vitrectomy to assess the damage produced by conventional techniques of ILM peeling. All eyes were examined histologically. RESULTS: Group 1: Nine eyes could be examined (problems with fixation in two eyes). In four of nine eyes, the ILM was either removed or detached, in one eye there was a superficial retinal hemorrhage, and in four eyes the ILM was still intact. In the latter cases, there was no intraoperative whitening or bleeding and no posterior vitreous detachment was present histologically. Group 2: Four eyes (problems with fixation in one eye) could be examined. The ILM was either removed or detached in three eyes. In one eye there was a superficial retinal hemorrhage. In one eye the ILM was not removed and there had neither been intraoperative whitening or hemorrhage nor histologically visible posterior vitreous detachment. In both groups, the nerve fiber layer in treated areas was thicker than in adjacent untreated retina. In one eye the retina was gently manipulated with microforceps in an attempt to perform ILM peeling. This led to damage to all layers of the retina. CONCLUSIONS: Removal of the ILM by Er:YAG laser is possible in vivo. However, the variability of the laser effects calls for further improvement such as a reliable indicator of ablation depth. In any case, any damage to the retina was lesser than that produced by microforceps.

Animals↗
PubMed2000

Acute and chronic effects of transmyocardial laser revascularization in the nonischemic pig myocardium by using three laser systems.

BACKGROUND AND OBJECTIVE: Transmyocardial laser revascularization (TMLR) improves symptoms in patients with coronary heart disease. It is based on the hypothesis of direct perfusion of ischemic myocardium by means of laser-created channels. Three different lasers were used to study alternative effects on myocardium. STUDY DESIGN/MATERIALS AND METHODS: The present study was conducted to evaluate comprehensively and compare the short and long-term tissue effects and the basic interaction mechanisms of CO2, Ho:YAG, and Er:YAG laser radiation with myocardium. The dynamics of laser-induced impacts in gel used as tissue phantom was visualized by time-resolved flash photography. Pressure measurements performed during perforation of myocardium in vitro revealed the explosive character of the ablation process. Channels made into the left ventricle of normal pig hearts were examined immediately and 6 weeks after creation. RESULTS: Regardless of laser source, all channels became occluded within 6 weeks by scar. Minimal acute thermal damage by Er:YAG laser corresponded to smaller scars. Pulsed Ho:YAG caused stronger tissue tearing than continuous wave CO2 irradiation. An increased volume density of intramyocardial vessels was found about the scars 6 weeks after treatment with all lasers. CONCLUSION: The laser sources permitted to study outcome of pressure effects and thermal damage in vivo. There were only minor differences between the three laser systems used. Rapid channel occlusion suggests that rather than revascularization, subsidiary physiologic tissue effects elicited by the thermal, oxidative, or mechanical action of the laser impact may contribute to the beneficial clinical effects of TMLR.

Animals↗
PubMed2000

Erbium: YAG laser ablation of retinal tissue under perfluorodecaline: determination of laser-tissue interaction in pig eyes.

PURPOSE: To evaluate the effect of Er;YAG laser on pig retina using a perfluorodecaline/retina interphase with the goal of precisely determining the extent of retinal tissue ablation. METHODS: Free running (tau = 250 microsec) Er:YAG laser pulses were transmitted through a zirconium fluoride (ZrF4) fiber guarded by quartz rod (d = 1000 microm). Laser pulses were applied to the retinal surface of enucleated pig eyes. Eyes were mounted in a specially designed rotating sample holder. The fiber probe was elevated 1.0 +/- 0.3 mm above the retinal surface with perfluorodecaline serving as transmitting medium. The laser energy was applied in a circular pattern with a radius of 3.0 mm. Radiant exposures were set to 1, 3, 5, and 10 J/cm2. RESULTS: Tissue ablation linearly increased with radiant exposure from 3.2 +/- 3.7 microm at 1 J/cm2 up to 40.9 +/- 12.9 microm at 10 J/cm2. Thermal tissue changes extended 70 +/- 10 microm vertically into the retina and 25 +/- 5 microm horizontally. Distortion of outer photoreceptor segments was noticed when the retina was exposed to radiant exposures of 3 J/cm2 or higher. CONCLUSIONS: The Er:YAG laser in combination with perfluorodecaline produced precise ablation of the pig retina, which suggests the feasibility of this technique for safe ablation of epiretinal membranes.

Animals↗
PubMed1997

Technical aspects of laparoscopic splenectomy in children.

Different authors reported about their experiences in laparoscopic splenectomy. The preparation of vessels and ligaments are feasable without major problems. Nevertheless the handling of the organ during the operation and during splenic extraction can be very difficult, especially in larger organs. The authors report experience with the technique of laparoscopic splenectomy and describe a new technical aspect in handling the spleen during this procedure. A loop of an umbilical band is used for retracting the organ during the preparation and placing the spleen into a sterile bag for the removal of the organ. This device helps prevent damages to the capsule caused by forceps. Large organs can be placed into the pelvis, and the bag is placed and opened in the upper abdomen. The authors used this technique successfully in seven patients. The results are compared with previous experiences.

Adolescent↗
PubMed1997

An approach to defining and operationalizing critical thinking.

The faculty in a midwestern university confronted the imperative to define and measure critical thinking in the nursing undergraduate curriculum. Theoretical and operational definitions were developed by faculty through literature review, extensive discussion, student participation, and evaluation. These activities also led to the generation of a list of indicators to assess the presence of critical thinking. Through the process faculty have developed a deeper understanding of critical thinking and fostered students' critical thinking abilities.

Clinical Competence↗
PubMed1992

Significant factors in the disinfection and sterilization of flexible endoscopes.

BACKGROUND: Many nosocomial infection outbreaks have been linked to improper disinfection of the flexible endoscopes used in hospitals and clinics. The objective of this study was to evaluate the efficacy of scope disinfection with glutaraldehyde and hydrogen peroxide in manual and mechanical protocols. METHODS: Bacillus subtilis and Pseudomonas cepacia were the test organisms. Each channel in two different endoscopes was seeded and evaluated separately. Residual chemical germicide levels in the channels and in the work environment were also measured. RESULTS: Parametric analyses were carried out on log transformations of number of colony-forming units recovered. Repeated measures analysis demonstrated that both the type of disinfectant and the method of washing were significant factors for disinfection. CONCLUSIONS: Hydrogen peroxide proved to be more efficacious than glutaraldehyde for killing or removing B. subtilis in a 10-minute contact period. Automatic disinfection was more efficacious than manual disinfection for killing or removing B. subtilis in a 10-minute contact period. The channel being disinfected also proved to be a significant factor, with carbon dioxide and elevator channels the most difficult to disinfect consistently.

Bacillus subtilis↗
PubMed1992

[The effect of adding clonidine to mepivacaine. Axillary brachial plexus blockade].

Clonidine (Cl) added to local anaesthetics (LA) prolongs the duration of both anaesthesia and analgesia after peripheral nerve blocks. In this study, we investigated the dose-dependent effect of Cl added to mepivacaine (M) on clinical efficacy, onset, and regression time of brachial plexus block. METHODS. Ninety patients were randomly assigned to one of three groups. Every patient received 46 ml of a mixture containing 400 mg M (pH adjusted with NaHCO3 to 7.25) and either 0.9% NaCl (group A), 0.12 mg Cl (group B), or 0.24 mg Cl (group C). The axillary block was performed using the catheter technique. In a double-blind fashion, the onset of sensory and motor blockade was tested every 5 min for 30 min. Duration of anaesthesia, analgesia, and motor blockade (time between injection and return of sensation, onset of pain, or ability to move, respectively) was assessed using a questionnaire. M plasma levels were measured by HPLC in 10 patients from each group for up to 120 min. Blood pressure (BP), heart rate (HR), and respiratory rate (RR) were measured for up to 120 min. Sedation was assessed using a verbal rating scale. RESULTS. There was no difference in the onset of blockade. There was dose-dependent prolongation of the duration of anaesthesia, analgesia, and motor blockade with significant differences between groups C and A regarding all three parameters, between groups C and B regarding duration of anaesthesia, and between groups B and A regarding duration of analgesia. There was no significant difference in M plasma levels. Although there was only a slight but significant decrease in mean BP values in groups B+C and no difference in HR and RR, 2 patients (1 group B, 1 group C) had marked decreases in BP and HR (less than 70 mmHg systolic resp. less than 50/min) after 120 and 210 min. Sedation occurred in most patients receiving Cl. CONCLUSIONS. Addition of Cl to LA produces a dose-dependent prolongation of anaesthesia, analgesia, and motor blockade. Neither the onset time nor the number of patients with adequate surgical anaesthesia was influenced by Cl. Considering the M plasma levels, it is unlikely that the prolongation of the block is caused by local vasoconstriction, which is proposed to be the mechanism of action of epinephrine. The mean differences in haemodynamic parameters were not of clinical relevance, but the two dramatic drops in BP and HR, probably caused by Cl, were significant.

Adult↗
PubMed1991

[Orthotopic liver transplantation at the Island Hospital. Initial experiences 1985-1990].

Between 1985 and 1990 22 orthotopic liver transplantations (OLT) were realized in 19 patients. Active infection and diffuse splanchnic venous thrombosis were the only contra-indications to the intervention. Sixteen patients were transplanted electively; three had to be retransplanted urgently. Three patients had an urgent primary transplant. The incidence of surgical complications related to liver implantation was fair. One patient (5%) developed a late portal vein thrombosis; another patient (5%) had to be retransplanted because of hepatic artery thrombosis. All patients presented one or more major postoperative complications. All, but one, patients had a rejection of the allograft; five of them needed treatment with mono- or polyclonal antilymphocytic sera to reverse the rejection. One patient was retransplanted because of a hyperacute rejection. The six-month survival in this series is 68.5% (13 of 18 patients); one patient died 7 months post-OLT due to a neurological complication of her Wilson disease. Quality of life (from 6 to 64 months post-OLT) is excellent in the 12 long-term survivors. This small experience of the Bernese transplantation program shows that liver transplantation is a safe surgical procedure allowing excellent quality of life in a majority of patients.

Adult↗
PubMed1989

Obliteration of the axillary artery after axillary block.

A case of total obliteration of the axillary artery after axillary block is presented. This resulted from an accidental intramural injection of local anaesthetic (mepivacaine 1%, 40 ml, with adrenaline 1:200,000). Axillary block was performed using the loss of resistance technique with a blunt needle (45 degrees bevel). The diagnosis was made by palpation of the peripheral pulse and by comparison between the skin temperatures of each arm. The thrombosed part of the artery was successfully reconstructed with an autologous saphenous vein graft.

Adolescent↗
PubMed1986

Significance of physical exercise in hypertension. Influence of water temperature and beta-blockade on blood pressure, degree of cardiac hypertrophy and cardiac function in swimming training of spontaneously hypertensive rats.

In previous studies swimming training (ST) of spontaneously hypertensive rats (SHR) at 36 degrees water temperature (WT) led to a decrease in blood pressure (BP). A similar effect of ST has not been described in human hypertension. Our purpose was to investigate the influence of WT on this training effect, the influence of ST on LV hypertrophy and the involvement of adrenergic stimuli in the latter. Male SHR (20 weeks old) were divided randomly into 4 groups. 1) SHR sedentary 2) SHR ST 36 degrees 3) SHR ST 26 degrees 4) SHR ST 36 degrees + atenolol (50 mg/kg/die). ST was performed 2 X 90 min/day for 31 days and then reduced to 2 X 60 min/day. After 7 weeks of ST BP was lower in all ST groups compared with SHR sedentary (p less than 0.001). BP was higher in ST 26 degrees than in ST 36 degrees (p less than 0.05). No additional effect of atenolol on BP was observed. The increase in the degree of LV hypertrophy during ST (ST 36 degrees: +15%; ST 26 degrees: +26%) could be prevented by atenolol (ST 36 degrees + atenolol: -1.5%). ST 36 degrees led to improved ventricular and myocardial performance with decreased LV wall stress ("luxury hypertrophy"), while in ST 26 degrees ventricular dilatation occurred with increased systolic wall stress and elevated LVEDP. It was uncertain whether this should be interpreted as a state of LV pre-insufficiency in ST 26 degrees in spite of no indications of impaired myocardial contractile capability. Peripheral vascular resistance (PVR) was significantly reduced by ST. The reduction was more evident in ST 26 degrees, but was partially compensated for by an increased cardiac output. The weights of adrenal glands increased (p less than 0.001), most markedly for ST 26 degrees. The level of thyroid hormones (T3 and fT3) was increased in ST 26 degrees. In summary, ST proved to be effective in lowering BP of SHR. WT had great influence with respect to cardiovascular adaptation and mechanisms involved in ST of SHR. Cardioadrenergic drive was of great significance for the process of hypertrophy during ST in SHR.

Animals↗
PubMed1986

Myocardial and ventricular mechanics as influenced by disopyramide.

The effects of disopyramide (D) on the mechanics of isolated myocardium as well as on the whole ventricle were examined in the rat model. Moreover bipolar leads of the apex and an area at the base of the left ventricle were set up to get indications for changes in the spread of excitation. D in concentrations of 10(-8) to 10(-4) mol/l did not affect the diastolic elastic properties of isolated myocardium. Isometric contraction amplitude was nearly unaltered, while rate of isometric contraction and relaxation were slightly increased. In the whole ventricle in situ D (2 to 10 mg/kg b.w. administered i.v.) induced a dose-dependent decrease in left ventricular isovolumetric peak pressure (16%), max.pos. dP/dt (40%) and max.neg. dP/dt (30%; for highest doses respectively), while time to peak pressure and relaxation time 90% were prolonged. Therapeutic dose of D (2 mg/kg b.w.i.v.) induced no decrease in essential systolic parameters of the whole ventricle under auxotonic conditions. Left ventricular pressure, dP/dt max.pos. and neg., left ventricular end-diastolic pressure and cardiac output were nearly unaltered. Heart rate showed a tendency to decrease, while total time of contraction and left ventricular ejection time increased. Higher doses of D led to marked cardiac depressant effects. The time interval between the excitation of the apex and an area at the base of the heart was increased. It was concluded that the negative dromotropic effect of D and thereby an altered pattern of left ventricular contraction are essential components in the elimination of the pressure gradient between left ventricle and aorta, observed in patients with muscular subaortic stenosis, and are presumably involved in the cardiac depressant effect of the drug in over-therapeutic doses.

Animals↗
PubMed1982

Plasma concentrations and haemodynamic effects of nitroglycerin during and after intravenous infusion in healthy volunteers.

The effects of nitroglycerin, infused intravenously at 3.4 and 7.5 micrograms/min over 30 min, on haemodynamic parameters were determined in the morning and the afternoon in a randomized, placebo-controlled study in 5 healthy volunteers. The mean steady-state concentrations of nitroglycerin reached in the plasma during the infusions of 3.4 and 7.5 micrograms/min were 0.35 +/- 0.06 ng/ml and 0.64 +/- 0.22 ng/ml, respectively. Wide inter-individual variation was noted. The nitroglycerin-induced increase in the orthostatic rise in heart rate and the change in digital-pulse-wave morphology roughly paralleled the plasma concentration, whereas the reduction in systolic blood pressure in the upright position was still evident 15 mins after the infusion, i.e. when nitroglycerin was no longer measurable in plasma. No significant diurnal variation in vascular sensitivity to the vasodilative action of nitroglycerin was demonstrable. The change in pulse-wave morphology resulting from the reduction in peripheral resistance (shift of the dicrotic wave in the descending limb towards the base-line) proved to be the most sensitive haemodynamic parameter.

Adult↗
PubMed1981

[Urokinase (in situ) in the case of acute ischemia of the lower limbs (author's transl)].

Eighteen patients with severe, acute ischemia of the lower limbs were treated with an arterial perfusion of the ischemic leg with Urokinase. This was associated, in thirteen patients, with a limited attempt of revascularization. The result of this treatment was an immediate improvement in twelve cases, which lasted, more than six months, in six patients. The authors insist on the interest of the arteriography performed after the fibrinolytic treatment in order to complete the revascularization.

Acute Disease↗
PubMed1980

Difference in nitroglycerin dose-response in the venous and arterial beds.

In twelve healthy volunteers given nitroglycerin sublingually (1.6 mg) or epicutaneously (12 mg), venous distensibility was found to be maximal, even at low plasma concentrations (less than 0.2 ng/ml); there was no further change with increasing concentrations. Peripheral arterial resistance, on the other hand, decreased progressively with rising plasma concentrations and no distinct plateau was demonstrable, even at the highest plasma concentration measured (greater than 2.0 ng/ml).

Adult↗