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C Leithner

Publications and source records attributed to C Leithner.

At least 19 recordsLinked to original sources
PubMed2001

No evidence for early decrease in blood oxygenation in rat whisker cortex in response to functional activation.

Using optical methods through a closed cranial window over the rat primary sensory cortex in chloralose/urethane-anesthetized rats we evaluated the time course of oxygen delivery and consumption in response to a physiological stimulus (whisker deflection). Independent methodological approaches (optical imaging spectroscopy, single fiber spectroscopy, oxygen-dependent phosphorescence quenching) were applied to different modes of whisker deflection (single whisker, full whisker pad). Spectroscopic data were evaluated using different algorithms (constant pathlength, differential pathlength correction). We found that whisker deflection is accompanied by a significant increase of oxygenated hemoglobin (oxy-Hb), followed by an undershoot. An early increase in deoxygenated hemoglobin (deoxy-Hb) proceeded hyperoxygenation when spectroscopic data were analyzed by constant pathlength analysis. However, correcting for the wavelength dependence of photon pathlength in brain tissue (differential pathlength correction) completely eliminated the increase in deoxy-Hb. Oxygen-dependent phosphorescence quenching did not reproducibly detect early deoxygenation. Together with recent fMRI data, our results argue against significant early deoxygenation as a universal phenomenon in functionally activated mammalian brain. Interpreted with a diffusion-limited model of oxygen delivery to brain tissue our results are compatible with coupling between neuronal activity and cerebral blood flow throughout stimulation, as postulated 110 years ago by C. Roy and C. Sherrington (1890, J. Physiol. 11:85--108).

Animals↗
PubMed2001

Optic neuropathy in uremia: an interdisciplinary emergency.

Optic neuropathy in uremia is rare. Although the consequences of optic neuropathy-blindness or substantial loss of vision-are devastating, only a few cases have been reported by way of single case reports and case series studies. The reported patients are heterogeneous with regard to the cause of neuropathy. We report the case of a patient with uremic optic neuropathy and summarize the other cases reported in the literature so far. Based on the data available from these reports, we propose a classification system, which includes nonischemic neurotoxic uremic optic neuropathy; ischemic optic neuropathy, more specifically anterior ischemic optic neuropathy; and optic neuropathy as a result of drug side effects, benign intracranial hypertension, and optic neuritis. The immediate institution of dialysis and corticosteroid therapy and correction of anemia and relative hypotension can optimize the chances of visual recovery for these patients. Close collaboration among nephrologists, ophthalmologists, and neurologists is important in this interdisciplinary emergency.

Anti-Inflammatory Agents↗
PubMed1994

Magnetic resonance imaging of the heart during positive end-expiratory pressure ventilation in normal subjects.

OBJECTIVES: Magnetic resonance imaging was used to assess the effects of ventilation with positive end-expiratory pressure (PEEP) on cardiac volumes, especially on atrial volumes as well as to determine semiquantitative measurements of spatial interactions between heart, lungs and chest. DESIGN: Prospective study with healthy volunteers undergoing mechanical ventilation with different levels of PEEP during magnetic resonance imaging. SETTING: Magnetic resonance unit, Institute of Diagnostic Imaging, Rudolfinerhaus Hospital. SUBJECTS: Twelve healthy volunteers. INTERVENTIONS: Volunteers were imaged, using a multislice-multiphase technique during spontaneous breathing and with PEEP values of 0, 7, and 15 cm H2O. MEASUREMENTS AND MAIN RESULTS: Atrial as well as ventricular volumes, chest diameters, and midventricular contact between the heart and anterior chest wall were determined on transverse-oblique sections. Atrial volumes showed a progressive decline beginning at a PEEP of 7 cm H2O. Diastolic filling of both ventricles was reduced. A PEEP level of 15 cm H2O induced a significant increase in the sagittal-oblique but not in the transverse-oblique chest diameter. PEEP values of 7 and 15 cm H2O shortened the length of the midventricular contact between the heart and anterior chest wall. CONCLUSIONS: Left and right ventricular end-diastolic volumes and stroke volumes decreased significantly during ventilation with PEEP at 15 cm H2O, as did end-systolic atrial volumes. Volume changes in association with changes of chest and heart configuration suggest external cardiac compression by the expanding lungs. Furthermore, this study illustrates the feasibility of magnetic resonance imaging in mechanically ventilated patients.

Adult↗
PubMed1993

Atrial natriuretic peptide release in response to different positive end-expiratory pressure levels.

OBJECTIVE: To assess the influence of different positive end-expiratory pressure (PEEP) levels on plasma atrial natriuretic peptide concentrations. DESIGN: Prospective, randomized study. SETTING: Intensive care unit of a university hospital. PATIENTS: Twenty-seven patients who were mechanically ventilated due to acute respiratory failure. INTERVENTION: None. MEASUREMENTS AND MAIN RESULTS: The patients were randomized into three groups: in each group, a defined PEEP level (5, 10, or 15 cm H2O, respectively) was applied, alternating with zero PEEP (0 cm H2O) in consecutive order (reversal experiment). Blood samples for the determination of atrial natriuretic peptide concentrations were drawn from the pulmonary artery and the radial artery catheters. There were no decreases in atrial natriuretic peptide concentrations with a PEEP of 5 cm H2O, but significant decreases could be shown for PEEP values of 10 and 15 cm H2O. The patients of all groups were subjected to PEEP levels of 5, 10, 15, and 20 cm H2O in randomized order (step experiment). The data demonstrated a significant inverse correlation between changes in PEEP levels and changes in plasma atrial natriuretic peptide concentrations. CONCLUSION: The data suggest that the release of atrial natriuretic peptide is influenced by a PEEP of > or = 10 cm H2O, while a PEEP of < or = 5 cm H2O does not disturb this cardiac endocrine function.

Adult↗
PubMed1992

Influence of age on outcome of mechanically ventilated patients in an intensive care unit.

OBJECTIVE: To assess the influence of age on the outcome of patients receiving prolonged mechanical ventilation. DESIGN: Retrospective study. SETTING: Intensive care unit. PATIENTS: A total of 1,141 patients in our ICU during a 32-month period. A total of 536 patients required mechanical ventilation. After exclusion of 171 patients ventilated for less than 24 hrs after surgery, 365 patients were investigated. MEASUREMENTS AND MAIN RESULTS: Two hundred sixty-six (73%) patients were aged less than 70 yrs; 99 (27%) patients were greater than or equal to 70 yrs. There was no significant difference in mortality rate between the younger and the older age groups. There was no significant influence of other important factors, such as severity of illness, duration of mechanical ventilation, or length of ICU stay. The only factor showing a significant influence on patient outcome was the reason for mechanical ventilation. There were more survivors in the group being ventilated because of ventilatory insufficiency than in the group with oxygenation impairment (57.8% vs. 23.9%, p less than .001). CONCLUSION: An influence of age on the outcome of mechanically ventilated patients in the ICU could not be ascertained in this study.

Adolescent↗
PubMed1989

Esophageal tracheal combitube (ETC) for emergency intubation: anatomical evaluation of ETC placement by radiography.

The esophageal tracheal combitube (ETC) is designed for emergency intubation. The ETC is inserted blindly allowing ventilation after either esophageal or endotracheal placement. A special pharyngeal balloon serves to seal the upper airways. In 10 cardiac arrest patients, emergency intubation with the ETC was performed. Blood gas analyses showed adequate ventilation. Radiography proved correct placement of the proximal and distal balloons in accordance with design theory. Hyperinflation experiments documented expansion of the proximal balloon into the oral cavity rather than towards the epiglottis.

Emergencies↗
PubMed1989

Esophageal tracheal combitube, endotracheal airway, and mask: comparison of ventilatory pressure curves.

The esophageal tracheal Combitube (ETC) is a new airway especially designed for airway maintenance and ventilation in unconscious patients such as those requiring CPR. The ETC may be used as an esophageal obturator or an endotracheal airway. Previous studies yielded a significantly higher mean arterial oxygen tension (PaO2) during ventilation using an ETC in the esophageal position compared to a conventional endotracheal airway (ETA). To investigate this phenomenon, endotracheal and airway opening pressures were examined in 12 patients in randomized order during ventilation with an ETC in the esophageal position, with an ETA, and with a mask, respectively. In this study again the PaO2 was higher with ETC compared to ETA. The following differences in intratracheal pressure and flow could be found for ETC when compared to ETA: smaller rising pressure during inspiration, prolonged expiratory flow time, and formation of a small positive end expiratory pressure (PEEP). These factors may be responsible for the improved oxygen tension with ETC. Comparing mask to ETC ventilation, PaO2 did not differ; however, mean arterial carbon dioxide tension was higher during mask ventilation.

Adult↗
PubMed1988

Atrial natriuretic peptide decrease during spontaneous breathing with continuous positive airway pressure in volume-expanded healthy volunteers.

We examined the effect of spontaneous breathing with continuous positive airway pressure (CPAP) on the plasma concentrations of immunoreactive (ir) alpha-atrial natriuretic peptide (ANP). In three experiments, each of 11 healthy male volunteers performed CPAP at 20, 10 and 0 cm H2O for 2 h during continuous volume loading. Samples were drawn from a peripheral vein. Plasma concentrations of irANP were determined by a sensitive radioimmunoassay. Significantly lower concentrations of irANP were observed during 20 cm H2O CPAP than at 10 and 0 cm H2O. The concentrations of irANP did not differ significantly when individuals breathing with CPAP at 10 and at 0 cm H2O were compared. Our data suggest that CPAP at 20 cm H2O lowers the release of ANP in volume-expanded subjects. We hypothesize that this phenomenon may contribute to the fluid retention and renal dysfunction observed frequently during high CPAP levels. The decline in plasma concentrations of irANP may be the result of atrial compression by the distended lungs and of reduced venous return to the heart during CPAP.

Adult↗
PubMed1987

Mechanical ventilation with positive end-expiratory pressure decreases release of alpha-atrial natriuretic peptide.

The influence of PEEP during controlled mechanical ventilation (CMV) on plasma levels of alpha-atrial natriuretic peptide (alpha-ANP) was examined in seven patients suffering from acute respiratory failure. The majority of patients were volume-expanded. Samples were drawn from the superior vena cava, right atrium, pulmonary artery, and radial artery. All alpha-ANP levels were significantly depressed by 15 cm H2O PEEP for one hour, when compared to CMV without PEEP. During the PEEP period, cardiac index, creatinine clearance, urinary flow and urinary sodium excretion were decreased. CMV with PEEP of 20 cm H2O depressed peripheral venous plasma levels of alpha-ANP in six volume-expanded healthy volunteers, too. The decreased release of alpha-ANP could be a consequence of atrial compression by the distended lungs and of reduced venous return. We suggest that the decline in plasma alpha-ANP levels contributes to fluid retention and renal dysfunction, which occur frequently during CMV with PEEP. More detailed studies are necessary to confirm our hypothesis.

Adult↗
PubMed1987

Evaluation of esophageal tracheal combitube in cardiopulmonary resuscitation.

Prompt establishment of an airway is a primary goal in CPR of nonbreathing and unconscious patients. The esophageal tracheal combitube (ETC) is a new airway, designed for emergency intubation providing sufficient ventilation whether the airway is placed into the trachea or into the esophagus. We evaluated the effectiveness of the ETC in 31 patients during CPR. Blood gas analyses obtained during esophageal placement of the ETC showed results comparable to those of ventilation with a conventional endotracheal airway (ETA). The ETC appeared to oxygenate and ventilate patients adequately without complications. The efficacy, safety, and ease of insertion ensure rapid airway control. It is concluded that the ETC provides a sufficient alternative to the ETA whenever ideal conditions or trained staff for endotracheal intubation are not immediately available.

Aged↗
PubMed1987

Mechanical ventilation with the esophageal tracheal combitube (ETC) in the intensive care unit.

Mechanical ventilation in critically ill patients is usually performed with the conventional endotracheal airway. The esophageal tracheal combitube (ETC) is a new device for cardiopulmonary resuscitation, conceived to bridge the gap between hospital and prehospital phases. The ETC may be used in esophageal and endotracheal positions. The authors report six patients who were ventilated with the ETC in the esophageal obturator position for 2-8 h after emergency ventilation. Blood gas data showed adequate ventilation with the ETC during the observation period. Data suggest that mechanical ventilation with the ETC is possible for several hours after cardiopulmonary resuscitation. This might be helpful during the initial post-arrest period, when replacement of the ETC by a conventional endotracheal airway might destabilize a vulnerable patient.

Aged↗
PubMed1987

Eicosanoids of platelets and vascular wall in chronic renal insufficiency.

There is good evidence that retention products accumulating in chronic renal insufficiency influence prostaglandin (PG) synthesis, thus affecting platelet-vascular wall interaction. The vascular PGI2 synthesis is increased and prolonged in vitro, the plasma factor activity enhanced. A defective platelet function is frequently observed; it is completely restored by peritoneal dialysis, but only partially by hemodialysis. The sensitivity of platelets to PGI2 and its plasmatic degradation are unchanged. There is evidence of a shift of arachidonic acid metabolism from cyclooxygenase to lipoxygenase. These changes may be attributed to undialyzable plasma constituents, the 'middle molecules'.

Arachidonic Acids↗
PubMed1986

Continuous pump-driven hemofiltration associated with a decline in alpha-atrial natriuretic peptide.

The levels of alpha-atrial natriuretic peptide (ANP) in the right atrium, pulmonary artery, radial artery, and superior vena cava plasma were measured by radioimmunoassay in eight patients with volume-expansion due to different diseases. The alpha-ANP levels were significantly increased, but became decreased after fluid removal by continuous veno-venous hemofiltration. When all alpha-ANP concentrations of different anatomical locations and hemodynamic variables were grouped, pulmonary capillary wedge pressure correlated significantly with all alpha-ANP groups, whereas right atrial mean pressure correlated with alpha-ANP levels in pulmonary artery plasma only. Alpha-ANP concentrations were distinctly lower in superior vena cava plasma than in plasma from the right atrium, pulmonary artery, and radial artery. Since alpha-ANP plays an important role in the homeostasis of sodium and fluid balance, measurement of alpha-ANP concentrations, particularly in right atrium, pulmonary artery, or radial artery plasma, might provide valuable information on the status of the critically ill.

Adult↗