Search PubMed⌕ Search

Biomedical subjects

U Schwarz

Publications and source records attributed to U Schwarz.

At least 37 records · Page 2Linked to original sources
PubMed2001

The effects of sevoflurane and halothane anesthesia on cerebral blood flow velocity in children.

UNLABELLED: We compared cerebral blood flow velocity during anesthesia with sevoflurane and halothane in 23 children admitted for elective surgery (age, 0.4-9.7 yr; median age, 1.9 yr; ASA physical status I-II). Inhaled induction was performed in a randomized sequence with sevoflurane or halothane. Under steady-state conditions, cerebral blood flow velocity (systolic [V(s)], mean [V(mn)], and diastolic [VD]) were measured by a blinded investigator using transcranial pulsed Doppler ultrasonography. The anesthetic was then changed. CBFV measurements were repeated after washout of the first anesthetic and after steady-state of the second (equivalent minimal alveolar concentration to first anesthetic). The resistance index was calculated. VD and V(mn) were significantly lower during sevoflurane (V(mn) 1.35 m/s) than during halothane (V(mn) 1.50 m/s; P = 0.001), whereas V(s) was unchanged. The resistance index was lower during halothane (P < 0.001). Our results indicate lower vessel resistance and higher mean velocity during halothane than during sevoflurane. IMPLICATIONS: The mean cerebral blood flow velocity is significantly decreased in children during inhaled anesthesia with sevoflurane than during halothane. This might be relevant for the choice of anesthetic in children with risk of increased intracranial pressure, neurosurgery, or craniofacial osteotomies.

Anesthetics, Inhalation↗
PubMed2000

Hierarchical visual processing is dependent on the oculomotor system.

Using functional MRI and eye movement recordings we studied the processing of hierarchical stimuli. In agreement with others, we found a minor left hemispheric dominance during local and right dominance during global processing. When attention was directed locally, well-known oculomotor cortical areas were activated, and saccades were elicited in 41% of the trials. Their latencies were similar to pro-saccades. During global processing virtually no saccades occurred. These results suggest two different operational modes of attention. Attending to local features induces a shift of attention, which simultaneously computes a saccade on any level above the brainstem with a computational burden equal to reflexive saccades. Conversely, attending to global features induces an expansion of the focus of attention, which reinforces fixation.

Attention↗
PubMed2000

Provision of supplementary fluids to breast fed infants and later breast feeding success.

It has been shown that altering hospital policies in a way to avoid interference of routine prescriptions with initiation of breast feeding and to provide active encouragement to mothers and personnel can result in significant benefit for later breast feeding success. It is less clear, however, which of the elements of a promotional programme such as UNICEF/WHO's "ten steps to successful breast feeding" are absolutely essential and which can be adapted to local cultural habits. We performed an open randomized multicenter study in Switzerland to evaluate, whether restriction of supplementary fluids for breast fed infants in the first week of life and strict avoidance of artificial teats and pacifiers affects later breast feeding success. Follow up to 6 months was ensured by mailed questionnaires. 602 mother infant pairs were enrolled. Of 294 infants in the intervention group 39% were excluded from the final analysis because of protocol violations, mainly maternal request for the use of pacifiers or bottles. Though the number of dextrin maltose supplements during the first two days (1.7 vs. 2.2 on day 1, 2.2 vs. 2.6 on day 2) and the percentage of infants receiving any supplement (85% vs. 96.6%) was significantly smaller in the intervention group, the difference was disappointingly small. The prevalence of breast feeding was 100% vs. 99% at day 5, 88% vs. 88% at 2 months, 75% vs. 71% at 4 months and 57% vs. 55% at 6 months, none of the differences being significant. We conclude that rigorous adherence to all of the ten steps may encounter obstinate resistance from cultural habits even in a population highly favourable to breast feeding. An improvement in adherence does not necessarily lead to better breast feeding success. The results of the few comparable studies in the literature show also that cultural practices during the first months of life may influence profoundly the long term effects of interventions during the first days of life.

Breast Feeding↗
PubMed2000

Difficult airway management: comparison of the Bullard laryngoscope with the video-optical intubation stylet.

PURPOSE: To evaluate, whether the video-optical intubation stylet (VOIS) was more successful for difficult tracheal intubation than the Bullard laryngoscope (BL). METHODS: An intubation mannequin head was modified so that, using a Macintosh blade size 3, only the epiglottis was visible at direct laryngoscopy, representing a grade III laryngoscopic view. Forty anesthesiologists attempted tracheal intubation using each technique. Tracheal intubation with the Bullard laryngoscope was performed using the attached non-malleable intubating stylet preloaded with an endotracheal tube. The video-optical intubation stylet inserted into an endotracheal tube was used with direct laryngoscopy. During conventional laryngoscopy, the video-view from the stylet tip allowed the tracheal tube to be guided behind the epiglottis into the trachea. Ten attempts with each technique were performed by each anesthesiologist in randomized order. Intubation time, and failed intubation (> 60 sec/esophageal intubation) were recorded. The operators assessed the degree of difficulty of each method using a Likert-scale. RESULTS: Mean intubation time (19.2+/-4.5 sec for the BL and 18.8+/-4.6 sec for the VOIS) was almost the identical. The video-optical intubation stylet was associated with fewer failed intubations (8 vs. 41; P<0.005) and had a lower degree of difficulty (1.7+/-0.65 for the VOIS and 2.6+/-0.74 for the BL; P<0.0001). No correlation was found between the anesthesiologist's experience and mean intubation time, estimated degree of difficulty or number of unsuccessful intubation. CONCLUSION: The video-optical intubation stylet was a more effective and simpler intubation device to facilitate difficult tracheal intubation than the Bullard laryngoscope.

Epiglottis↗
PubMed2000

Video-intuboscopic monitoring of tracheal intubation in pediatric patients.

PURPOSE: To evaluate the efficacy of video-intuboscopic monitoring during orotracheal intubation in a pediatric anesthesia teaching unit. METHODS: In 100 pediatric patients direct laryngoscopy performed by residents or nurse anesthetists was monitored on a video display using a flexible, ultralight video-endoscopic system (O.D. 2.8 mm/length 1.8 m) within the endotracheal tube (ETT). Best direct laryngoscopic view was assessed by the intubator. The instructor observed the intubation procedure on the video display and noted number of intubation attempts, best laryngoscopic monitor view, tube passage through the larynx and final tube position. If required he gave instructions or corrections. After removal of the laryngoscope, tracheal tube position was adjusted using the monitor view. Difficulties attributed to the fibreoptic endoscope during intubation and removal from the ETT were recorded. RESULTS: The trachea was successfully intubated at the first attempt in all patients. The supervisor detected one esophageal and 12 endobronchial intubations that were immediately corrected before starting ventilation. Final visualized endotracheal tube adjustment above the carina was possible in all patients except in one with copious tracheal secretions. Compared with direct laryngoscopy the video display provided an improved view of the vocal cords during intubation. In six patients direct laryngoscopy was difficult but the tracheas were intubated using the monitor view. No difficulties with the equipment were encountered except that the black coated endoscope compromised recognition of the black ETT depth-markings in small tubes. CONCLUSIONS: Video-intuboscopic monitoring is a useful monitor of tracheal intubation. "The improved view of the cords may provide assistance during difficult laryngoscopy.

Adolescent↗
PubMed2000

Quantitative human in vivo evaluation of high resolution MRI for vessel wall morphometry after percutaneous transluminal angioplasty.

Visualization of the vessel wall after transluminal angioplasty is important to monitor the restenosis progress. Intravascular ultrasound proved its capabilities as an invasive procedure in many studies. The aim of this study was to evaluate the feasibility of high-resolution MRI as a non-invasive tool for follow-up after PTA. High-resolution magnetic resonance images (pixel size: 0.49 * 0.49 mm(2)) were acquired on a 1.0 T clinical scanner. Morphometry was conducted after conversion of DICOM images into TIFF format using ScionImage on a PC. In-vitro studies using a polyvinylchloride tube were evaluated by two independent investigators. Goldstandard was a caliper rule and direct radiography. Five patients were monitored before and 24 h, six weeks, three months and six months after PTA. In vivo measurements promised a good concordance for both investigators for area as well as for diameter measurements. Area measurements showed correlations up to r = 0.86 (p < 0.001) whereas the correlations of diameters were slightly inferior (r between 0.58 and 0.84; p < 0.005). Relocation of the same slice position in the follow up studies could be guaranteed using anatomic landmarks in the images. As a non-invasive tool to assess restenosis after PTA high-resolution MRI promises to be a reproducible technique. It is easy to identify the same vascular region in different studies due to neighboring anatomic landmarks. Progression of disease as well as success of pharmacologic treatment to prevent restenosis may be monitored.

Aged↗
PubMed2000

Morphology of coronary atherosclerotic lesions in patients with end-stage renal failure.

BACKGROUND: An excessive rate of cardiac death is a well-known feature of renal failure. Coronary heart disease is frequent and the possibility has been raised that the natural history of the coronary plaque is different in uraemic patients. We assessed the morphology of coronary arteries in patients with end-stage renal failure and compared them with coronary arteries of matched non-uraemic control patients. METHODS: Fifty-four cases were identified at autopsy who met the inclusion criteria: cases, end-stage renal disease (n=27); controls, non-renal patients with coronary artery disease (n=27). At autopsy all three coronary arteries were prepared at corresponding sites for investigations: (i) qualitative analysis (after Stary), (ii) quantitative measurements of intima and media thickness (by planimetry), (iii) immunohistochemical analysis of the coronary plaques and (iv) X-ray diffraction of selected calcified plaques. RESULTS: Qualitative analysis of the coronary arteries showed significantly more calcified plaques of coronary arteries in patients with end-stage renal failure. Plaques of non-uraemic patients were mostly fibroatheromatous. Media thickness of coronary arteries was significantly higher in uraemic patients (187+/-53 microm vs 135+/-29 microm in controls) and intima thickness tended to be higher (158+/-38 microm vs 142+/-31 microm) but this difference was not statistically significant. Plaque area (4.09+/-1. 50 mm(2) vs 4.39+/-0.88 mm(2)) was comparable in both groups. Lumen area, however, was significantly lower in end-stage renal patients. Immunohistochemical analysis of the cellular infiltrate in coronary arteries showed no major differences in these advanced plaques of uraemic and non-uraemic subjects. CONCLUSION: Coronary plaques in patients with end-stage renal failure are characterized by increased media thickness and marked calcification. In contrast to the previous opinion the most marked difference compared to non-uraemic controls does not concern the size, but the composition of the plaque. Deposition of calcium within the plaques may contribute to the high complication rate in uraemic patients.

Aged↗
PubMed2000

Linear and nonlinear time series analysis of the black hole candidate cygnus X-1

We analyze the variability in the x-ray lightcurves of the black hole candidate Cygnus X-1 by linear and nonlinear time series analysis methods. While a linear model describes the overall second order properties of the observed data well, surrogate data analysis reveals a significant deviation from linearity. We discuss the relation between shot noise models usually applied to analyze these data and linear stochastic autoregressive models. We debate statistical and interpretational issues of surrogate data testing for the present context. Finally, we suggest a combination of tools from linear and nonlinear time series analysis methods as a procedure to test the predictions of astrophysical models on observed data.

Journal Article↗
PubMed1999

[Postdural puncture headache: diagnosis, prevention and therapy].

Lumbar puncture (LP) is a routine technique performed for a variety of procedures, e.g. diagnosis, administration of drugs, myelography and spinal anaesthesia. Postdural puncture headache is a common complication (30-40% in diagnostic LP). Prevention can be accomplished by using small-gauge needles (< or = 25 G) or pencil-point needles (22 G). Therapy should be carried out in a stepwise approach. The first step is bedrest, use of analgetics, i.v. fluids and an adequate guidance of the patient. The second step comprises special drug therapy. Several methods of pharmacologic management have been presented in the literature, but most of these are case reports. There is a lack of large double-blind placebo-controlled studies. Theophylline, caffeine, ACTH and sumatriptan are potentially promising agents for the treatment of postdural puncture headache. The efficacy of theophylline has been proven in a double-blind and placebo-controlled study. There are a few studies and case reports reporting that caffeine p.o. and i.v. is effective in the treatment of postdural puncture headache, but recurrence of headache after caffeine therapy is frequent. ACTH acts on a complex hormonal system. The treatment with sumatriptan has been reported in only a few case reports. The third step, and one of the most effective treatments of postdural puncture headache, is the epidural blood patch. The success rate ranges between 80 and 97%.

English Abstract↗
PubMed1999

Asymmetry in visual motion processing.

The smooth pursuit system is traditionally employed using a single small target moving on a homogeneous background. It still is not fully understood, however, how accurate tracking is sustained in the presence of a structured background, which will activate global motion processing in the opposite direction as a consequence of the ongoing eye movement. To further study this interaction, we used brief shifts of a textured background injected at various times during the initiation of smooth pursuit. While shifts opposite to the target direction did not alter smooth pursuit performance, those in the same direction resulted in a marked transient perturbation of the pursuit. These results suggest a simple yet limited mechanism that adjusts the sensitivity of global motion processing.

Adolescent↗
PubMed1999

[Development of a new closed-loop system for controlling mivacurium-induced neuromuscular blockade].

UNLABELLED: There are many closed-loop control systems for muscle relaxants reported, but only a few could cope with the introduction of the latest shorter acting neuromuscular blocking drugs. These new muscle relaxants such as mivacurium require a fast adapting closed-loop system for controlling an adequate infusion. METHODS: After approval of the local ethics committee and having the patients' informed consent a total number of 75 patients [ASA I and II] were included in the study and assigned either to a training-, prediction-, prediction-/feedback- or a validation phase, as needed. Anaesthesia was induced and maintained with propofol in a TCI-mode with a plasma level of 3 to 5 micrograms/ml and 0.1 mg fentanyl boli as needed in all patients. In the last validation phase, having 20 patients, the prediction error and the error of the whole system was taken and analysed. RESULTS: A closed-loop system using a neural network as a predictor could be established. In the final validation phase consisting of 20 patients the mean square prediction error was found to be 0.1% +/- 0.2% [mean +/- SD]. The mean square error of the whole system was 0.55% +/- 0.59% [mean +/- SD]. CONCLUSIONS: A closed-loop system for control of a mivacurium infusion could be established. The system proofed to be reliable for a closed-loop infusion of mivacurium in order to maintain a predefined degree of neuromuscular blockade of 95% during routine surgery. The performance of the described controller is comparable to all recent attempts and could therefore be useful for scientific studies. It should be further validated and established for other muscle relaxants, as well.

Adolescent↗
PubMed1999

Complete thromboendarterectomy of the calcified ascending aorta and aortic arch.

BACKGROUND: Arteriosclerotic plaques of the ascending aorta and transverse arch increase the operative risk of cardiac operations and are strong predictors for late cerebrovascular events. METHODS: Twenty-two patients, mean age 68 +/- 6 years (range, 55 to 77 years), with grade IV + V plaques of the ascending aorta and transverse arch underwent coronary artery bypass grafting (n = 21) and aortic valve replacement (n = 8). Cerebrovascular emboli from unknown sources were found preoperatively in 8 patients (36%). All were in sinus rhythm. Complete thromboendarterectomy of the ascending aorta and transverse arch was performed during hypothermic circulatory arrest. After 21 +/- 12 months (range, 4 to 44 months), magnetic resonance imaging and transthoracic echocardiography of endarterectomized vessels was performed. RESULTS: There was one perioperative death (4.5%), one early (4.5%), and one late (4.7%) adverse neurologic event. Follow-up examinations revealed normal diameters of the endarterectomized aorta. CONCLUSIONS: For patients with grade IV + V plaques, thromboendarterectomy of the ascending aorta and transverse arch can be performed with an acceptable surgical risk and a low recurrence rate for cerebrovascular events. Dilatation of the endarterectomized aorta was not observed.

Aged↗
PubMed1999

Transfer of 131I and fluoresceinyl sialic acid derivatives into the oligosaccharide chains of IgG: a new method for site-specific labeling of antibodies.

Biochemical modifications of IgG can help to avoid damages caused by oxidation or reduction. Terminal groups of the saccharide structures, located in the Fc-portion of IgG molecules, were modified by enzymatic reactions. IgG was pretreated with sialidase, to cleave bound sialic acid, and with galactosyltransferase, to increase the number of acceptor sites for transfer reactions. Afterward, modified sialic acid derivatives were transferred enzymatically into the oligosaccharide chains of IgG. Labeling was possible with sialic acids modified in either position 5 or position 9. The usefulness of this method was demonstrated for radioactive and fluoresceinylated reagents, with yields up to 90% in 1 h. Immunological investigations have shown no influence on the immunoreactivity by the described modification of saccharide structures.

Animals↗
PubMed1999

[Effects of priming technique on onset profile of cisatracurium].

Compared to atracurium, cisatracurium releases less laudanosine and histamine, but it has a longer onset time. The primary objective of this study was a blinded, randomized comparison of intubation scores and onset times of a threefold ED 95 of cisatracurium using the priming technique with two priming substances cisatracurium itself and pancuronium. To test the effect of priming with cisatracurium or pancuronium on the onset of cisatracurium, 45 patients were anaesthetised with 0.15-0.25 mg/kg alfentanil, 0.25-0.3 mg/kg edomidate i.v. and O2/N2O, and were randomisely divided into one of three groups. After induction, 15 patients were primed with sodium chloride and thereafter received 0.15 mg/kg cisatracurium, 15 patients were primed with 0.01 mg/kg cisatracurium, another 15 patients were primed with 0.015 mg/kg pancuronium and the last two groups received 0.14 mg/kg cisatracurium three minutes later. Neuromuscular response was monitored by adductor pollicis electromyogram (EMG) by stimulating in a TOF pattern. Times for T1 reduction to 75%, 50%, 25% and 0% and T1 recovery to 25% were taken. Intubation was performed 120 seconds after the main relaxant dose and scored in four grades. The two priming groups showed a significantly faster onset of neuromuscular blockade than the control group (cisatracurium priming group: T1 = 0: 178.4 +/- 16.3 sec., pancuronium priming group 171.2 +/- 15.3 sec. vs. control group: T1 = 0: 205.5 +/- 18.9 sec.). Both primed groups showed no significantly better intubation scores, compared with the control group. Using the priming principle, cisatracurium will give good intubation scores 120 seconds after injection with a clinical duration profile comparable to an equipotent dose of atracurium.

Adult↗