Biomedical subjects

Bernd Schmitz

Publications and source records attributed to Bernd Schmitz.

15 recordsLinked to original sources

PubMed2007

Non-normality and transformations of random fields, with an application to voxel-based morphometry.

Parametric tests of linear models for images modeled as random fields are based like ordinary univariate tests on distributional assumptions. It is here shown that the effect of departures from assumptions in random field tests is more pronounced than in the univariate condition. Simulations are presented investigating in detail the influence of smoothing, unbalancedness and leverages on empirical thresholds. In certain conditions, significance tests may become invalid. As a case study, the existence and effect of departures from normality of gray matter probability maps, commonly used in voxel-based morphometry, is investigated, as well as the effect of different transformation strategies involving estimating the degree of transformation from the data by maximum likelihood. The best results are achieved with a voxel-by-voxel transformation, suggesting heterogeneity of distributional form across the volume for this kind of data.

Adult↗

PubMed2007

MR neurography with multiplanar reconstruction of 3D MRI datasets: an anatomical study and clinical applications.

INTRODUCTION: Extracranial MR neurography has so far mainly been used with 2D datasets. We investigated the use of 3D datasets for peripheral neurography of the sciatic nerve. METHODS: A total of 40 thighs (20 healthy volunteers) were examined with a coronally oriented magnetization-prepared rapid acquisition gradient echo sequence with isotropic voxels of 1 x 1 x 1 mm and a field of view of 500 mm. Anatomical landmarks were palpated and marked with MRI markers. After MR scanning, the sciatic nerve was identified by two readers independently in the resulting 3D dataset. RESULTS: In every volunteer, the sciatic nerve could be identified bilaterally over the whole length of the thigh, even in areas of close contact to isointense muscles. The landmark of the greater trochanter was falsely palpated by 2.2 cm, and the knee joint by 1 cm. The mean distance between the bifurcation of the sciatic nerve and the knee-joint gap was 6 cm (+/-1.8 cm). The mean results of the two readers differed by 1-6%. CONCLUSION: With the described method of MR neurography, the sciatic nerve was depicted reliably and objectively in great anatomical detail over the whole length of the thigh. Important anatomical information can be obtained. The clinical applications of MR neurography for the brachial plexus and lumbosacral plexus/sciatic nerve are discussed.

Adolescent↗

PubMed2007

Milrinone combined with vasopressin improves cardiac index after cardiopulmonary resuscitation in a pig model of myocardial infarction.

BACKGROUND: Milrinone used for acute cardiac insufficiency could be of interest during cardiopulmonary resuscitation because of its positive inotropic effects. In this study, the combination of milrinone-vasopressin was compared with epinephrine and vasopressin, as well as with the combination of epinephrine-vasopressin, in reference to hemodynamics. METHODS: Thirty-two pigs underwent ligation of the circumflex coronary artery and induction of ventricular fibrillation lasting for 4 min. Cardiopulmonary resuscitation was performed after randomization to one of four groups: epinephrine (30-microg/kg bolus), vasopressin (0.4-U/kg bolus), epinephrine-vasopressin (15-microg/kg epinephrine bolus, 0.2-U/kg vasopressin bolus), or milrinone-vasopressin (0.4-U/kg vasopressin bolus, 50-microg/kg milrinone bolus over 5 min and a continuous infusion of 0.4 microg.kg.min). The hemodynamic variables were measured before cardiopulmonary resuscitation as well as 4, 8, 15, and 30 min after return of spontaneous circulation. RESULTS: All animals were resuscitated successfully. The animals of the milrinone-vasopressin group displayed significantly (P<0.05) higher cardiac index values (30 min after return of spontaneous circulation: epinephrine, 65.8+/-13.2; vasopressin, 70.7+/-18.3; epinephrine-vasopressin, 69.1+/-36.2; milrinone-vasopressin, 120.7+/-34.8 ml.min.kg) without a decrease in mean arterial pressure or coronary perfusion pressure. CONCLUSIONS: The combination of vasopressin-milrinone as compared with epinephrine during cardiopulmonary resuscitation leads to an improved cardiac index without relevant decrease of mean arterial pressure or coronary perfusion pressure.

Animals↗

PubMed2006

Esophageal perforation: principles of diagnosis and surgical management.

PURPOSE: Esophageal perforation (EP) is still associated with a high mortality rate, even after surgical repair. We reviewed 17 cases of EP to evaluate the management of this major surgical problem. METHODS: We reviewed the medical records of all patients treated for EP in our department between November 2001 and November 2004. Therapy was based on various patient-related factors. RESULTS: Seventeen patients, with a mean age of 63 years, presented with EP mostly caused by iatrogenic incidents (11/17). In nine patients, the perforation was located in the thoracic segment, with a mean size of 2.5 +/- 0.6 cm. Thoracic computed tomography (CT) was performed in all patients to assess the periesophageal inflammation precisely. More than 50% showed signs of systemic inflammation indicative of sepsis, reflected by a dramatic increase in serum C-reactive protein and leukocytosis. Treatment consisted of debridement and drainage (n = 3), primary repair (n = 3), reinforced repair (n = 4), esophageal resection (n = 5), and conservative measures (n = 2). All patients, except for three with pre-existing liver dysfunction and other comorbidities, survived, representing a mortality rate of 17.6% (14/17). An analysis of the literature (2000-2005) revealed an overall mortality rate of 19.7% (101/521), ranging from 3% to 67%. CONCLUSION: Our data support the individualized surgical management of EP, based on careful evaluation of various patient-related factors, including CT findings.

Adult↗

PubMed2005

Multislice MR first-pass myocardial perfusion imaging: impact of the receiver coil array.

PURPOSE: To compare a new 12-element body phased-array coil with a conventional four-element surface receiver coil array to provide increased signal-to-noise ratios (SNRs) for cardiac steady state free precession (SSFP) perfusion imaging. MATERIALS AND METHODS: Thirteen consecutive patients were included in the study. Patients were examined both with a four-element surface coil array and a 12-element body coil array. First-pass myocardial perfusion imaging using saturation recovery SSFP was acquired during antecubital injection of Gd-DTPA. Imaging parameters: TR 2.8 msec/TE 1.3 msec, flip angle 50 degrees , bandwidth 960 Hz/pixel and half-Fourier acquisition. SNR was calculated using six regions of interest (ROI) for the myocardial perfusion scans. Calculations of corresponding ROIs using the two different coil setups were compared using analysis of variance (ANOVA). Semiquantitative perfusion parameters were calculated for both groups. RESULTS: The mean SNR in myocardial perfusion imaging increased by 21% using the 12-element coil setup (P < 0.001) when compared to the four-element coil. ROI comparisons revealed an increased signal inhomogeneity with the 12-element coil when compared to four-element coil experiments. Absolute normal range values of semiquantitative perfusion parameters were consistently higher using the 12-element coil setup (P < 0.001). CONCLUSION: The 12-element coil array provides higher SNR, but these improvements come with trade-offs in image homogeneity. Increased SNR translates into higher semiquantitative perfusion values and offers the potential for improved detection of perfusion defects.

Adult↗

PubMed2005

Intraoperative low-dose S-ketamine has no preventive effects on postoperative pain and morphine consumption after major urological surgery in children.

BACKGROUND: Clinical studies suggest low-dose ketamine may have preemptive effects on postoperative pain in adults. The objective of this study was to determine whether intraoperative low-dose S-ketamine reduces postoperative pain and morphine consumption in children undergoing major urological surgery. MATERIALS: Thirty children scheduled for major urological surgery were included in this prospective study. Anesthesia was performed as total intravenous anesthesia (TIVA) with alfentanil and propofol. Fifteen patients additionally received an intravenous bolus of S-ketamine (0.2 mg.kg-1) followed by a continuous infusion of 5 microg.kg-1.min-1, which was stopped immediately after skin closure (Ketamine Group). Another 15 patients received an infusion of saline (CONTROL group). After transfer to the PACU, pain intensity was evaluated using a numeric rating scale (NRS). First patient controlled analgesia (PCA) request, cumulative morphine consumption and pain intensities within the first 72 h were compared. RESULTS: Morphine consumption was not significantly different during the first 72 h ( CONTROL: 0.4 mg.kg-1, 0.24-0.51 mg.kg-1, Ketamine: 0.32 mg.kg-1, 0.19-0.61 mg.kg-1; median, 25-75% percentile; n.s.). However, differences were found in pain intensity during the first postoperative hour ( CONTROL: 4.0, 3.2-4.6, Ketamine: 2.5, 1.3-3.5; median, 25-75% percentile; P<0.05) and in the time to first PCA use ( CONTROL: 37, 28-46 min, Ketamine: 62, 38-68 min; median, 25-75% percentile; P<0.05). CONCLUSIONS: Intraoperative low-dose S-ketamine had no effect on morphine consumption during the first 72 h after surgery. The differences in pain intensity and time to first PCA use probably reflect additional sedation and antinociceptive effects of S-ketamine rather than a true 'prevention' of pain.

Alfentanil↗

PubMed2004

MRI of the brainstem in patients with major depression, bipolar affective disorder and normal controls.

Structural imaging studies of bipolar affective disorder or major depression have shown a spectrum of abnormal findings. However, a characteristic pattern of abnormality for either disease has not yet emerged. While the majority of studies focused on brain atrophy and the volumes of supratentorial cerebral structures, little attention has been paid to infratentorial structures. This MRI study focused on the pontomesencephalic area including the region of the raphe nuclei. The raphe nuclei are of special interest in affective disorders as they are the origin of the major serotonergic projections in this region. MRI scans of 10 bipolar I patients, 10 patients with major depression and 10 age-matched healthy control subjects were studied. The brain stem and the fourth ventricle areas as well as T2-relaxation times in the area of the raphe nuclei were evaluated. A difference between patients with major depression and control subjects for T(2)-relaxation times was found in a region of interest located along the midline of the pons. No difference was found between patients with bipolar disorder and control subjects. This finding needs to be replicated in a larger sample with more elaborated MRI techniques (multi-echo sequences) for the determination of T2-relaxation times.

Adult↗

PubMed2004

Monocular visual activation patterns in albinism as revealed by functional magnetic resonance imaging.

Human albinism is characterized by a disturbance of the chiasmatic projection system leading to predominant representation of just one eye in the contralateral hemisphere. Patients show congenital nystagmus without perceiving oscillopsia. The purpose of the present study was to demonstrate the consequences of atypical chiasmatic crossing with monocular visual stimulation using functional magnetic resonance imaging (fMRI). Sixteen patients with albinism and fifteen normally pigmented controls were stimulated with a monocular visual activation paradigm using flickering checkerboards. In patients, we observed contralaterally dominated activation of visual cortices correlating to clinical albinism parameters. This confirms albinism as a continuous range of hypopigmentation disorders. Additionally, albinos showed activation of the superior colliculus and of visual motion areas although the stimulus was stationary. Activation of visual motion areas is due probably to congenital nystagmus without a conscious correlate like oscillopsia.

Adult↗

PubMed2004

ECG artifacts during intraoperative high-field MRI scanning.

High-field magnetic resonance imaging (MRI) (1.5 T) has recently been introduced into the neurosurgical operating room for intraoperative resection control and functional neuronavigational guidance. However, long-lasting neurosurgical procedures in an operating room equipped with a high-field MRI scanner raise new challenges to the anesthesiologist. In particular, monitoring of vital signs during anesthesia requires equipment compatible with working in close vicinity to the strong magnetic field. However, even MRI-compatible electrocardiographic (ECG) monitoring interferes with electromagnetic fields, so several ECG artifacts can be observed in static and pulsed magnetic fields. As shown in this study, pulsed high-frequency fields induce characteristic field frequency-based artifacts in the ECG that can imitate malignant arrhythmia or provoke ST-segment abnormalities. The knowledge of possible and characteristic ECG artifacts during high-field MRI is therefore essential to prevent misinterpretation. Moreover, interference-free parameters such as pulse oximetry or invasive blood pressure curves are highly relevant during intraoperative MRI scans.

Adult↗

PubMed2003

Improved resuscitation after cardiac arrest in rats expressing the baculovirus caspase inhibitor protein p35 in central neurons.

BACKGROUND: Global cerebral ischemia is associated with delayed neuronal death. Given the role of caspases in apoptosis, caspase inhibitors may provide neuronal protection after cardiac arrest. To this end, the authors generated a transgenic rat line expressing baculovirus p35, a broad-spectrum caspase inhibitor, in central neurons. Its effects were evaluated on neuronal cell death and outcome after global cerebral ischemia. METHODS: Global cerebral ischemia was induced by cardiocirculatory arrest. After 6 min, animals were resuscitated by controlled ventilation, extrathoracic cardiac massage, epinephrine, and electrical countershocks. Neuronal death was assessed after 7 days by histologic evaluation of the hippocampal cornu ammonis 1 sector. Postischemic outcome was assessed by determination of overall survival and according to neurologic deficit scores 24 h, 3 days, and 7 days after resuscitation. RESULTS: The rate of 7-day survival after cardiac arrest for the transgenic rats (85%) was significantly higher than that for the nontransgenic controls (52%; P < 0.05). However, no differences were observed either in the number of terminal deoxynucleotidyltransferase-mediated d-uracil triphosphate-biotin nick end-labeling-positive cells or viable neurons in the cornu ammonis 1 sector or in the neurologic deficit score when comparing surviving transgenic and nontransgenic rats. These findings suggest that neuronal apoptosis after cardiac arrest is not primarily initiated by activation of caspases. CONCLUSION: Expression of baculovirus p35 can improve survival after cardiac arrest in rats, but the mode and site of action remain to be elucidated.

Animals↗

PubMed2003

Anesthesia during high-field intraoperative magnetic resonance imaging experience with 80 consecutive cases.

Intraoperative magnetic resonance imaging (MRI) has been used for years to update neuronavigation and for intraoperative resection control. For this purpose, low-field (0.1-0.2 T) MR scanners have been installed in the operating room, which, in contrast to machines using higher magnetic field strength, allowed the use of standard anesthetic and surgical equipment. However, these low-field MR systems provided only minor image quality and a limited battery of MR sequences, excluding functional MRI, diffusion-weighted MRI, or MR angiography and spectroscopy. Based on these advantages, a concept using high-field MRI (1.5 T) with intraoperative functional neuronavigational guidance has been developed that required adaptation of the anesthetic regimen to working in the close vicinity to the strong magnetic field. In this paper the authors present their experience with the first 80 consecutive patients who received anesthesia in a specially designed radio frequency-shielded operating room equipped with a high-field (1.5 T) MR scanner. We describe the MR-compatible anesthesia equipment used including ventilator, monitoring, and syringe pumps, which allow standard neuroanesthesia in this new and challenging environment. This equipment provides the use of total intravenous anesthesia with propofol and remifentanil allowing rapid extubation and neurologic examination following surgery. In addition, extended intraoperative monitoring including EEG monitoring required for intracranial surgery is possible. Moreover, problems and dangers related to the effects of the strong magnetic field are discussed.

Adolescent↗

PubMed2003

Configuration of the optic chiasm in humans with albinism as revealed by magnetic resonance imaging.

PURPOSE: To determine whether the size and configuration of the optic chiasm in humans with albinism is different from that in normal control subjects. METHODS: Seventeen patients and 15 control subjects underwent magnetic resonance imaging of the entire head. Images were reformatted to the chiasm region and analyzed with observer-independent morphometry and measurements by a blinded observer. RESULTS: The albino group showed significantly smaller chiasmatic widths, smaller optic nerves and tracts, and wider angles between nerves and tracts. Statistical morphometry showed a different configuration of the optic chiasm. CONCLUSIONS: Size and configuration of the optic chiasm in humans with albinism are distinctly different from those in normal control subjects and reflect the atypical crossing of optic fibers.

Adult↗

PubMed2002

Subjective memory complaints: objective neural markers in patients with Alzheimer's disease and major depressive disorder.

Patients with probable Alzheimer's disease and depressive patients frequently present with subjective memory complaints. Objective distinction of underlying neuronal substrate malfunction and early cross-sectional differential diagnosis have been elusive thus far. We used repetitive learning and free recall of abstract geometric patterns during functional magnetic resonance imaging to assess episodic memory in older subjects (ages 56-64 years) who sought first-time medical attention with subjective memory complaints and were diagnosed with probable Alzheimer's disease (NINCDS-ADRDA criteria; ages 51-67 years) or major depressive disorder (DSM-IV; ages 50-65 years). Contrasting healthy seniors or depressive patients with Alzheimer's disease patients revealed superiority of hippocampal activation. Contrasting Alzheimer's disease patients with seniors showed bilateral prefrontal activity as a correlate of futile compensation of episodic memory failure. Contrasting patients who had major depressive disorder with seniors or patients who had Alzheimer's disease showed bilateral activation of the orbitofrontal cortex and the anterior cingulate. Subjective memory complaints may be classified objectively and very early with functional magnetic resonance imaging of episodic memory in groups of patients with Alzheimer's disease and depressive syndrome. This may facilitate drug trials with evaluation of specific treatments, but further studies will be needed to establish the differential diagnosis for the individual patient.

Aged↗

PubMed2002

Pediatric trauma anesthesia.

Trauma has a significant impact on pediatric morbidity and mortality. Depending on the emergency medical services and health care system, anesthesiologists may be involved in pediatric trauma care at the scene, in the emergency department, in the operating room, or in the intensive care unit. Familiarity with the pathophysiology of pediatric trauma and age-dependent anatomical and physiological features is, therefore, essential to every anesthesiologist. Fast and appropriate interventions with respect to the clinical status and the suspected injuries are the key to successful treatment. Due to the high incidence of head injury, airway management and hemodynamic stabilization are of utmost importance. For preclinical trauma care, however, evidence-based data showing a gold standard for pediatric trauma care are still lacking.

Journal Article↗

PubMedDate not supplied

Variability in memory performance in aged healthy individuals: an fMRI study.

Episodic memory performance varies in older subjects but underlying biological correlates remain as yet ambiguous. We investigated episodic memory in healthy older individuals (n=24; mean age: 64.4+/-6.7 years) without subjective memory complaints or objective cognitive impairment. Episodic memory was assessed with repetitive learning and recall of abstract geometric patterns during fMRI. Group analysis of brain activity during initial learning and maximum recall revealed hippocampal activation. Correlation analysis of brain activation and task performance demonstrated significant hippocampal activity during initial learning and maximum recall in a success-dependent manner. Neither age nor gray matter densities correlated with hippocampal activation. Functional imaging of episodic memory thus permits to detect objectively variability in hippocampal recruitment in healthy aged individuals without subjective memory complaints. Correlation analysis of brain activation and performance during an episodic memory task may be used to determine and follow-up hippocampal malfunction in a very sensitive manner.

Aged↗