Search PubMed⌕ Search

Biomedical subjects

H Scherer

Publications and source records attributed to H Scherer.

At least 37 records · Page 2Linked to original sources
PubMed1999

[Laser surgery of the middle nasal meatus in recurrent sinusitis].

We present our concept for treating patients suffering from recurrent sinusitis with coagulating lasers (Nd:YAG 1024 nm, Diode 810 or 904 nm). In these patients, the middle meatus is often narrowed by a hyperplastic middle turbinate, septum spurs and ridges, or by isolated polyps that block an ostium. We treat these patients by linear or punctate coagulation of the lateral wall of the middle turbinate, reducing the size of septum spurs, and blunting septal ridges or coagulating polyps. The outpatient procedure is performed with a laser fiberoptic system of 400 nm in contact mode with an energy of 3-5 watts. The amount of total energy applied to a specific tissue depends on the duration of laser contact at that point. The patient is anaesthesized superficially. Patients with a high degree of nasal hyperreactivity also receive antihistaminic preoperative treatment. Initial results show a significant increase of nasal flow with a decrease of sinus symptoms.

Chronic Disease↗
PubMed1999

Combined intratumor cisplatinum injection and Nd:YAG laser therapy.

OBJECTIVES/HYPOTHESIS: Interstitial laser therapy (ILT) has become useful for tumor palliation in patients with advanced head and neck cancer. Cisplatinum chemotherapy also is a frequent adjuvant treatment for recurrent tumors, but systemic toxicity limits application. Intratumor cisplatinum injection combined with ILT may improve therapy of these recurrent tumors with reduced toxicity. STUDY DESIGN: Prospective. Tumor transplants were injected with cisplatinum in a gel implant before ILT to evaluate treatment response and toxicity in a preclinical study. METHODS: UCLA-P3 human squamous cell carcinoma tumors were grown as subcutaneous transplants in nude mice and treated by intratumor injection of 2 mg/mL cisplatinum in a slow-release, collagen-based gel carrier 4 hours before interstitial implantation of Nd:YAG laser fiberoptics to induce local tumor hyperthermia. Treatment efficacy and toxicity were followed for 12 weeks after combined drug and laser therapy compared with ILT alone. RESULTS: Combined cisplatinum gel and ILT was a significant improvement (P < .01 by chi-square test) and induced 57% complete responses without regrowth in 21 transplanted tumors compared with only 24% in 21 tumors after ILT alone during 12-week follow-up. Recurrences in both cases appeared to result from nonuniform laser energy delivery within tumors via the implanted fiberoptic tip. CONCLUSIONS: The results of this experimental combined cisplatinum and ILT study suggest it may be possible to improve treatment of advanced head and neck cancer by intratumor injection of gel implants containing the drug followed by interstitial Nd:YAG laser hyperthermia.

Animals↗
PubMed1999

Influence of CO2 laser application to the guinea-pig cochlea on compound action potentials.

HYPOTHESIS: Experiments in guinea pigs were performed to clarify which, if any, of the CO2 lasers in different modes (continuous wave [cw] and superpulse) can damage the inner ear on application of the laser parameters required for stapedotomy and to determine their application safety. METHODS: The laser effect connected with perforating the basal convolution of the guinea-pig cochlea (cochleostomy) was examined. Acoustic evoked potentials (compound action potentials [CAPs]) yielded information on inner-ear function. RESULTS: In cw mode, even single applications of an approximately four times higher power density (60,000 W/cm2) than necessary for stapedotomy at a pulse duration of 50 msec (energies up to 1 J) and 20-fold applications of effective parameters for a footplate perforation (power density 16,000 W/cm2; energy 0.2 J) did not cause CAP changes. Experimental studies with the CO2 superpulse laser used (peak pulse powers: ca. 300 W) have demonstrated that irreversible CAP alterations already occur in the effective laser range in > 40% of the animals. CONCLUSIONS: Because damage is expected only at much higher energies (> 2 J) than those used clinically, the CO2 laser in cw mode has a high application safety for laser stapedotomy. The application of the CO2 laser in superpulse mode with peak pulse powers of approximately 300 W in stapedotomy appears to be more unreliable and dangerous for the inner ear.

Animals↗
PubMed1998

Thermic effects in the "vestibule" during laser stapedotomy with pulsed laser systems.

BACKGROUND AND OBJECTIVE: Apart from the ablation properties at the stapes footplate, the degree of thermic loading in the inner ear is important in determining the suitability of pulsed lasers for stapedotomy. The aim of the study is to compare the thermic effects in the vestibule with different pulsed laser systems. STUDY DESIGN/MATERIALS AND METHODS: Temperature increases and heat exchange processes in the fluid (physiological saline) were examined in a calorically and physiologically approximated cochlea model for applying the laser parameters effective in creating footplate perforations. RESULTS: With all systems, increases in the energy density, number of pulses, and thus resultant total energy lead to higher temperatures. In the effective energy density range, the highest temperature increases achieved with the requisite number of pulses at a distance of 2 mm behind the perforation are 26 degrees C with the Ho:YAG laser. The lowest temperature maxima are 5.5 degrees C with the Er:YAG and <5 degrees C with the Er:YSGG laser. The excimer laser, investigated at only one energy density, showed maximal temperatures of 10 degrees C. CONCLUSION: The Er:YSGG and Er:YAG laser can be applied in laser stapedotomy in a relatively broad energy density range without a risk of inner ear damage by thermic loading. On the other hand, the Ho:YAG laser is not recommended for stapedotomy because of the higher energy density and pulse rate required for sufficient perforation and the resultant higher temperature increases in the perilymph. Though likewise achieving perforations with only slight temperature increases in the fluid of the cochlea model, the excimer laser does not seem appropriate for stapedotomy because of the long period of heat exposure (ca. 60 s) due to the lower ablation rate at the stapes necessitating a longer application time.

Cochlea↗
PubMed1998

Combined coronary artery bypass grafting and abdominal aortic aneurysm repair.

BACKGROUND: We report here the results of combined coronary artery bypass grafting (CABG) and abdominal aortic aneurysm (AAA) repair and the factors associated with higher mortality following this procedure. METHODS: The authors performed a retrospective chart review of 26 patients who underwent combined CABG and AAA repair between March 1990 and October 1996. RESULTS: No postoperative myocardial infarction or major cardiac complications were noted. A morbidity rate of 38% (n = 10) and mortality rate of 11% (n = 3) were noted. Comparative analysis of nonsurvivors (n = 3) versus survivors (n = 23) revealed the following: ejection fraction (EF) was significantly lower (33% +/- 3% versus 44% +/- 14%, P < 0.05), duration of cardiopulmonary bypass (CPB) was significantly longer (239 +/- 122 minutes versus 141 +/- 54 minutes, P < 0.05), and incidence of postoperative respiratory failure (67% versus 17%, P = 0.001) were significantly higher in nonsurvivors. No differences in mean age, gender distribution, incidence of hypertension or diabetes were noted between the groups. CONCLUSIONS: Combined CABG and AAA repair protected patients from postoperative aneurysm rupture and myocardial infarction. Poor EF, prolonged CPB, and postoperative respiratory failure were associated with higher mortality.

Aged↗
PubMed1998

[Effect of the pulsed Er:YSGG and Ho:YAG laser on the organ of Corti of the guinea pig cochlear--a scanning electron microscopy study].

BACKGROUND: Recent experimental studies have demonstrated that, apart from the continuous wave lasers, several pulsed laser systems are also suitable for stapedotomy. The aim of this study was to clarify whether irradiation of the basal convolution of the guinea pig cochlea could cause morphological inner-ear changes using the Er:YSGG and Ho:YAG laser with laser parameters required for stapedotomy. METHODS: After opening the bulla, the basal convolution of the guinea pig cochlea, whose thickness is similar to that of the human stapes footplate, was irradiated with the Er:YSGG and Ho:YAG laser. The laser parameters used were those necessary for an adequate perforation of a human stapes footplate (500-600 microns). The cochleae were removed 90 minutes, 1 day, 2 weeks, or 4 weeks after laser application. The organ of Corti was examined by scanning electron microscopy in all convolutions. RESULTS: Application of Er:YSGG laser parameters effective for stapedotomy (5 pulses, energy: 85 J/pulse, energy density: 36 J/cm2, total energy: 0.425 J) had no adverse effects on the organ of Corti in the guinea pig cochlea. On the other hand, effective Ho:YAG laser parameters (10 pulses, energy: 210 J/pulse, energy density: 90 J/cm2, total energy: 2.1 J) caused damage to the outer hair cells with fusion of stereocilia and formation of giant cilia leading to partial or total cell loss. The inner hair cells and supporting cells were usually normal. CONCLUSION: Our results clearly demonstrate that the Er:YSGG laser has high application safety. It could prove to be a viable alternative to the thermically acting CO2 laser for stapedotomy. The Ho:YAG laser is not well tolerated in animals and has low application safety. Its use in stapedotomy would be unreliable and dangerous for the inner ear.

Animals↗
PubMed1997

Effects of pulsed laser systems on stapes footplate.

BACKGROUND AND OBJECTIVE: The aim of the present study was to investigate the tissue ablation capacity of various pulsed lasers at the stapes footplate. STUDY DESIGN/MATERIALS AND METHODS: Isolated human stapes and bovine compact-bone platelets were used to determine the effective laser parameters and appropriate application technique for achieving a perforation measuring 500-600 microns in diameter. Of interest were also the shape and quality of the perforations, the reproducibility of the perforation effect, and the thermically altered marginal zones occurring at the footplate. Three pulsed laser systems were used: excimer, holmium:YAG (Ho:YAG), and erbium:YSGG (Er:YSGG) lasers. RESULTS: The tissue-ablating effect of pulsed laser systems permits a precise and controlled management of the stapes footplate through low and readily reproducible ablation rates. The extent of thermic side effects at the footplate is lower in comparison to the purely thermically acting cw and superpulse laser systems. The Er:YSGG laser exhibits the highest ablation rate at the stapes and is thus the most effective laser for perforation of the stapes footplate. Though somewhat less effective, the Ho:YAG laser also appears to be suitable for stapedotomy. On the other hand, we do not consider the applied excimer laser (308 nm) to be particularly appropriate at the stapes because of its low ablation rates. CONCLUSION: Thus, the erbium laser could represent an alternative to the argon, KTP 532, and CO2 lasers, already clinically successful in stapes surgery. However, further studies are necessary to examine the transmission of thermic energy into the vestibule and the acoustic stress to the inner ear during laser stapedotomy, to be able to make a definitive statement about the safest and most effective laser system for stapes surgery.

Animals↗
PubMed1997

[Individual differences in susceptibility to motion sickness].

Several different theories exist about the origin of kinetosis and the space adaptation syndrome, with individual sensitivities differing significantly. One explanation involves the hypothesis of a different otolith mass between the right and left statolith organ and especially a difference in the utricles. A difference in mass results in a different sensitivity to acceleration. For this reason we measured interindividual variances in saccular and utricular otolith mass. Since the anatomy of the vestibular organ in vertebrates is based as similar principles, we selected fish (salmon and trout) as our study model to facilitation preparations. The maximum difference in mass in the saccule was 17% and was generally smaller in the utricle, although in individual cases was much higher. We assume that a misbalanced sensitivity of the statolith organs occurs but is totally compensated for by the vestibular system as long as physiological motion patterns take place. Decompensation leads to kinetosis under non-physiological motion patterns. When the vestibular system is better balanced and has an equally distributed otolith mass to both sides, the possibility for developing kinetosis or space adaptation syndrome is much less likely.

Animals↗
PubMed1997

Normal interleukin-12 production in individuals with antibodies to Helicobacter pylori.

It is increasingly recognized that the inability of the immune system to clear H. pylori infection is caused by an inadequate immune response and is associated with chronic gastric inflammation. To further investigate the cellular immune response to H. pylori, we studied PBMC from 31 H. pylori antibody-negative and 16 H. pylori antibody-positive individuals for H. pylori-induced DNA synthesis, secretion of the Th1-type cytokine IFN-gamma and secretion of IL-12, a cytokine produced by bacteria-stimulated monocyte/macrophages and a potent inducer of antibacterial immune responses and Th1-type T cells. All experiments were performed using Y. enterocolitica 03 as control. Our results demonstrate that DNA synthesis, IFN-gamma production and IL-12 production induced by H. pylori or Y. enterocolitica 03 did not differ significantly between H. pylori antibody-positive and H. pylori antibody-negative individuals. However, in the H. pylori-positive group there was a tendency, although not statistically significant, to produce less IFN-gamma in response to H. pylori but not Y. enterocolitica. These results demonstrate that monocyte/macrophages from H. pylori-positive individuals secrete normal amounts of IL-12 upon bacterial challenge and suggest that the decreased production of IFN-gamma in H. pylori-positive individuals observed in previous studies is selective for H. pylori and not caused by decreased IL-12 secretion.

Antibodies, Bacterial↗
PubMed1997

On the origin of interindividual susceptibility to motion sickness.

According to the otolith asymmetry hypothesis for susceptibility to motion sickness, the interlabyrinthine asymmetry in the otoconial mass, which is normally compensated in the circuity of the vestibular system by appropriate neuronal weighting, becomes disrupted as a result of unfamiliar movement patterns or force environments. Measurements in various species have demonstrated a large scatter in the otoconial mass. As the utricle and saccule have distinct functions in the vestibular system it seems appropriate to deal with these organs separately. Results are presented on mass distribution and lateral preponderance of the otoconial mass in the utricles and saccules of the salmon (Salmo salar) and trout (Salmo irideus). The measurements revealed considerably larger dimensions of the saccular otoconia in these species, amounting to twenty-fold. This substantial difference indicates that different regulatory principles underlie the otoconial generation of each of the organs and is presumably related to their specific functions. The lateral preponderance was found to be normally distributed for both organs in both species, with standard deviations of approx. 4% except for the utricular otoconia of the salmon (13%). In a second set of experiments, fish were exposed to a Coriolis force environment. Their sealed aquarium was subjected to constant vertical axis rotation combined with pendular oscillation around the horizontal axis. The aquarium was illuminated by a light source fixed to project through the top, and a video camera recorded the movements of the fish. During combined rotation and pendular oscillation, one group of fish maintained an active compensatory swimming behaviour, whereas the movements of a second group became uncoordinated and often led to passive behaviour. Analysis of the otoconia of these two groups of fish promises to yield further evidence relevant to the otolith asymmetry hypothesis.

Animals↗
PubMed1996

Effects of continuous-wave laser systems on stapes footplate.

BACKGROUND AND OBJECTIVE: The aim of the present study was to clarify which of the presently available continuous-wave laser systems are best suited for application in stapes surgery. STUDY DESIGN/MATERIALS AND METHODS: Isolated human stapes and bovine compact-bone platelets were used to investigate the connections between the parameters of various laser systems and their effects on bone tissue. The purpose was to optimize the laser parameters required to achieve a perforation measuring 500 microns to 600 microns in diameter. Three different laser systems were applied: the argon and CO2 laser in continuous wave (cw) mode and the CO2 laser in superpulse mode. RESULTS: The suitability of the argon laser for stapedotomy is doubtful in view of the lower absorption coefficient of the stapes for the argon beam and the considerable influence which the degree of pigmentation of the irradiated medium exerts on its effect with the resultant poor reproducibility of the perforation diameter. The beam of the CO2 laser is far better absorbed at the footplate than that of the argon laser. This results in higher effectivity, lower thermic side effects, and better reproducibility of the perforation. The two modes of the CO2 laser do not show any appreciable differences. CONCLUSION: The experimental results presented indicate that the CO2 laser in cw and superpulse mode is the most suitable of the systems now clinically applied in stapes surgery.

Animals↗
PubMed1996

The dynamic contributions of the otolith organs to human ocular torsion.

We measured human ocular torsion (OT) monocularly (using video) and binocularly (using search coils) while sinusoidally accelerating (0.7 g) five human subjects along an earth-horizontal axis at five frequencies (0.35, 0.4, 0.5, 0.75, and 1.0 Hz). The compensatory nature of OT was investigated by changing the relative orientation of the dynamic (linear acceleration) and static (gravitational) cues. Four subject orientations were investigated: (1) Y-upright-acceleration along the interaural (y) axis while upright; (2) Y-supine-acceleration along the y-axis while supine; (3) Z-RED-acceleration along the dorsoventral (z) axis with right ear down; (4) Z-supine-acceleration along the z-axis while supine. Linear acceleration in the Y-upright, Y-supine and Z-RED orientations elicited conjugate OT. The smaller response in the Z-supine orientation appeared disconjugate. The amplitude of the response decreased and the phase lag increased with increasing frequency for each orientation. This frequency dependence does not match the frequency response of the regular or irregular afferent otolith neurons; therefore the response dynamics cannot be explained by simple peripheral mechanisms. The Y-upright responses were larger than the Y-supine responses (P < 0.05). This difference indicates that OT must be more complicated than a simple low-pass filtered response to interaural shear force, since the dynamic shear force along the interaural axis was identical in these two orientations. The Y-supine responses were, in turn, larger than the Z-RED responses (P < 0.01). Interestingly, the vector sum of the Y-supine responses plus Z-RED responses was not significantly different (P = 0.99) from the Y-upright responses. This suggests that, in this frequency range, the conjugate OT response during Y-upright stimulation might be composed of two components: (1) a response to shear force along the y-axis (as in Y-supine stimulation), and (2) a response to roll tilt of gravitoinertial force (as in Z-RED stimulation).

Acceleration↗
PubMed1996

Differential effects of D2- and D4-blocking neuroleptics on the procedural learning of schizophrenic patients.

OBJECTIVE: To illustrate the differential effects of D2- and D4-blocking neuroleptics on the procedural learning of patients with schizophrenia. METHOD: Twenty-nine schizophrenic patients were divided into 3 groups according to their pharmacological treatment: 1) drug naive, 2) haloperidol, and 3) clozapine. They were all assessed on clinical and procedural measures, the latter being the mirror drawing task. RESULTS: All groups showed progressive learning over the successive trials, and drug-naive patients performed better than the other groups. Patients in the haloperidol group showed many fluctuations over trials, suggesting difficulty in the progressive automation of the task. Such fluctuations did not occur in the clozapine group, but performances per se were worse than in the other groups during the learning trials. Automation of the task occurred at the same point (second block of trials) for all groups. CONCLUSION: These results suggest that D2- and D4-blocking neuroleptics do not similarly affect striatal dependent procedural learning in schizophrenia.

Adult↗
PubMed1996

Ocular counterrolling in response to asymmetric radial acceleration.

The fact that the labyrinths are positioned at approx. 3.5 cm from the head-centric axis leads to the generation of systematic radial acceleratory, or centrifugal, forces during physiological head rotations. Under physiological conditions, the forces exerted on the right and left maculae are generally assumed to be equal and opposite. In the present test, however, the subject was displaced eccentrically during constant angular velocity so that one labyrinth was aligned concentrically with the rotatory axis, whilst the other was exposed to the radial acceleration component generated by the chair rotation. In comparison with previous testing based on subjective setting of the visual vertical, three-dimensional eye movements were recorded in order to obtain an objective measure of the otolith-ocular response mechanisms in the brainstem. The results obtained from normal subjects demonstrate a predominant ocular counterroll (OCR) response to this asymmetric, or unilateral application of linear acceleration. The direction of the OCR response proved to be independent of direction of rotation. The findings demonstrate a symmetrical response magnitude for stimulation of the left and right maculae. In comparison with the OCR response to head-tilt, which can be described as critically damped, the time course of the present response appeared to be underdamped.

Acceleration↗
PubMed1996

[Manifestation of tuberous sclerosis in the ENT area].

Tuberous sclerosis (Bourneville-Pringle's disease) is a rare, largely autosomal dominant neurocutaneous disease. The disease can also result from spontaneous mutations. Although strongly variable in its manifestation, manifestations are typically characterized by involvement of the central nervous system (early childhood seizures), skin (facial angiofibromas) and kidneys (angiomyolipomas). In the case described, a 67-year-old female patient complained exclusively of obstructed nasal breathing that was found to be due to angiofibromas in the nasal vestibule. Oral fibromas were asymptomatic, while fibromas in the facial region resulted in some cosmetic changes. This exclusively ENT manifestation of a patient with tuberous sclerosis has not been described previously. As treatment, the fibromas were ablated by an Nd:YAG laser under local anesthesia. Other therapeutic options are described. Additional clarification of all organ manifestations is advisable in view of numerous possible pathologies present. Genetic consultation is also recommended, particularly for patients with an oligosymptomatic variant.

Aged↗
PubMed1996

[Thermal stress on the inner ear in laser stapedotomy].

Apart from ablation properties at the stapes footplate, the degree of thermal stress of the inner ear is important when considering the suitability of pulsed lasers for stapedotomy. The aim of the present study was to compare the heating of cochlear structures with presently available pulsed laser systems during stapedotomy under reproducible conditions. Temperature increases and heat-exchange processes were examined in a physiologic model of the cochlea using various laser parameters effective for footplate perforations. With all systems, increases in energy density, number of pulses and resultant total energy led to higher temperatures. In the effective energy density range, the highest temperature increases achieved with the requisite number of pulses at a distance of 2 mm behind the footplate perforation were 30 degrees and 26 degrees C with the pulsed CO2 and Ho:YAG lasers, respectively. The lowest temperature recorded was 5.5 degrees C with the Er:YAG and <5 degrees C with the Er:YSGG laser. The excimer laser investigated at only one energy density showed maximum temperatures of 10 degrees C. With regard to possible inner ear damage from thermal stress during laser stapedotomy, the Er:YSGG laser can be used safely over a relatively broad energy density range. The Er:YAG laser investigated also appears suitable for stapedotomy when considering thermal effects. In contrast, application of the pulsed CO2 laser at parameters effective for stapedotomy leads to high temperatures and wide scattering to compromise its use. The Ho:YAG laser also appears to be unsuitable because of the higher energy density and pulse rate required for sufficient perforation and the resultant higher temperature increases in the perilymph. Although footplate perforations can be achieved with only slight temperature increases in the fluid of the cochlea model, the excimer laser does not seem to be appropriate for stapedotomy because of the long period of heat exposure required and the lower ablation rates at the stapes.

Body Temperature↗
PubMed1995

Experimental studies on the suitability of the erbium laser for stapedotomy in an animal model.

Animal experiments in mature guinea pigs were devised to determine whether and to what extent inner ear damage can be caused by in vivo use of the erbium laser for stapedotomy. The present study examined the laser effect in connection with perforation of the basal convolution of the cochlea and subsequent application in the opened cochlea. Acoustic evoked potentials as compound action potentials (CAP) were recorded for changes in inner ear function. Findings demonstrated that five applications of the erbium:YSGG (yttrium-scandium-gallium-garnet) laser (energy, 85 mJ/pulse; energy density, 36 J/cm2) were needed to create a footplate perforation of 500-600 microns and did not lead to CAP alteration in any animal (n = 20). An increase of the repetition rate from 1 to 5 Hz likewise caused no CAP alteration (n = 17). Application of high total energies in the open cochlea (n = 5) to determine the safety of the laser system for stapedotomy revealed that a 10-fold increase in the total energy required for adequate perforation led to irreversible CAP alterations and no CAP could be recorded at a 15-fold increase in total energy. In contrast, a 5-fold maximum increase in total energy caused no CAP alterations. These results demonstrate the safety of the Er:YSGG laser comparable to that of the CO2 laser for stapedotomy, supporting its utility as an alternative method for surgery.

Acoustic Stimulation↗