Production of reflex cough by brainstem respiratory networks

Delineation of neural mechanisms involved in reflex cough is essential for understanding its many physiological and clinical complexities, and the development of more desirable antitussive agents. Brainstem networks that generate and modulate the breathing pattern are also involved in producing the motor patterns during reflex cough. Neurones of the ventrolateral medulla respiratory pattern generator mutually interact with neural networks in the pons, medulla and cerebellum to form a larger dynamic network. This paper discusses evidence from our laboratory and others supporting the involvement of the nucleus tractus solitarii, midline raphe nuclei and lateral tegmental field in the medulla, and the pontine respiratory group and cerebellum in the production of reflex cough. Gaps in our knowledge are identified to stimulate further research on this complicated issue.     

Impaired chemoreflex sensitivity in adult patients with multiple organ dysfunction syndrome—the potential role of disease severity

Objective The cardiac chemoreflex sensitivity is a powerful predictor of autonomic dysfunction in chronic heart failure and after myocardial infarction. The objective of the present study was to characterize cardiac chemoreflex sensitivity in patients with multiple organ dysfunction syndrome (MODS). We also aimed to elucidate the effect of the severity of MODS on the assessment of cardiac chemoreflex sensitivity.Design Prospective cohort study.Setting Twelve-bed medical intensive care unit in a university center.Patients Forty consecutively admitted patients with MODS during a 7-month period. Patients with MODS were identified by an APACHE II score of 20 or more. Sepsis was defined as a Sepsis Score, according to Elebute and Stoner, of 12 or more.Interventions The cardiac chemoreflex sensitivity was assessed using the regression of heart interval (ms) versus arterial oxygen pressure (mmHg).Measurements and results First, we established a new method to assess cardiac chemoreflex sensitivity and applied it to healthy controls and patients. Second, we found that cardiac chemoreflex sensitivity correlated with the severity of MODS as calculated by the APACHE II score (r²=0.34, p=0.001). This relation was best fitted by a model including minimum heart rate and standard bicarbonate in 24 h (r²=0.5, p<0.001) and Glasgow Coma Scale (r²=0.5, p=0.005). Age, however, did not significantly contribute (r²=0.001, p=0.8).Conclusions The calculation of cardiac chemoreflex sensitivity enabled us to quantify an important component of the cardiorespiratory interactions in patients with MODS. Severity of illness was a more pronounced determinant of impaired cardiac chemoreflex sensitivity than age. The quantification of the cardiorespiratory interactions by measuring the cardiac chemoreflex sensitivity has potential to identify a subgroup of patients with worse prognosis.     

Synergistic Effects of Antimicrobial Peptides and Antibiotics against Clostridium difficile

Accelerating rates of health care-associated infections caused by Clostridium difficile, with increasing recurrence and rising antibiotic resistance rates, have become a serious problem in recent years. This study was conducted to explore whether a combination of antibiotics with human antimicrobial peptides may lead to an increase in antibacterial activity. The in vitro activities of the antimicrobial peptides HBD1 to HBD3, HNP1, HD5, and LL-37 and the antibiotics tigecycline, moxifloxacin, piperacillin-tazobactam, and meropenem alone or in combination against 10 toxinogenic and 10 nontoxinogenic C. difficile strains were investigated. Bacterial viability was determined by flow cytometry and toxin production by enzyme-linked immunosorbent assay (ELISA). When combined at subinhibitory concentrations, antimicrobial peptides and antibiotics generally led to an additive killing effect against toxinogenic and nontoxinogenic C. difficile strains. However, LL-37 and HBD3 acted in synergism with all the antibiotics that were tested. Electron microscopy revealed membrane perturbation in bacterial cell walls by HBD3. In 3 out of 10 toxinogenic strains, HBD3, LL-37, piperacillin-tazobactam, and meropenem administration led to an increased toxin release which was not neutralized by the addition of HNP1. Antimicrobial peptides increase the bacterial killing of antibiotics against C. difficile regardless of the antibiotics'' mode of action. Membrane perturbation in or pore formation on the bacterial cell wall may enhance the uptake of antibiotics and increase their antibacterial effect. Therefore, a combination of antibiotics with antimicrobial peptides may represent a promising novel approach to the treatment of C. difficile infections.     

Central chemoreceptor modulation of breathing via multipath tuning in medullary ventrolateral respiratory column circuits

Ventrolateral respiratory column (VRC) circuits that modulate breathing in response to changes in central chemoreceptor drive are incompletely understood. We employed multielectrode arrays and spike train correlation methods to test predictions of the hypothesis that pre-B?tzinger complex (pre-B?tC) and retrotrapezoid nucleus/parafacial (RTN-pF) circuits cooperate in chemoreceptor-evoked tuning of ventral respiratory group (VRG) inspiratory neurons. Central chemoreceptors were selectively stimulated by injections of CO(2)-saturated saline into the vertebral artery in seven decerebrate, vagotomized, neuromuscularly blocked, and artificially ventilated cats. Among sampled neurons in the B?tzinger complex (B?tC)-to-VRG region, 70% (161 of 231) had a significant change in firing rate after chemoreceptor stimulation, as did 70% (101 of 144) of the RTN-pF neurons. Other responsive neurons (24 B?tC-VRG; 11 RTN-pF) had a change in the depth of respiratory modulation without a significant change in average firing rate. Seventy B?tC-VRG chemoresponsive neurons triggered 189 offset-feature correlograms (96 peaks; 93 troughs) with at least one responsive B?tC-VRG cell. Functional input from at least one RTN-pF cell could be inferred for 45 B?tC-VRG neurons (19%). Eleven RTN-pF cells were correlated with more than one B?tC-VRG target neuron, providing evidence for divergent connectivity. Thirty-seven RTN-pF neurons, 24 of which were chemoresponsive, were correlated with at least one chemoresponsive B?tC-VRG neuron. Correlation linkage maps and spike-triggered averages of phrenic nerve signals suggest transmission of chemoreceptor drive via a multipath network architecture: RTN-pF modulation of pre-B?tC-VRG rostral-to-caudal excitatory inspiratory neuron chains is tuned by feedforward and recurrent inhibition from other inspiratory neurons and from "tonic" expiratory neurons.     

Spezielle Aspekte bei Sepsispatienten

This article deals with specific aspects of the patient with sepsis and his treatment. With adequate therapy (antibiotics started within the first hour, early goal-directed therapy) initiated as early as possible, the patient with community-aquired severe sepsis in the emergency department has a considerable better chance to survive than the patient with prolonged severe sepsis in the ICU. The average age of patients with severe sepsis and septic shock treated at the ICU is rising, with consequences like oligosymptomatic presentation, altered pharmakokinetics according to older-age-induced reduced organ functions and prolonged stay at the ICU due to comorbidity. Due to sexual dimorphisms of the immune system, women have a better prognosis in sepsis than men. In an animal sepsis model activation of the estrogen receptor beta improves prognosis. Within six months after having survived severe sepsis, morbidity and mortality is still increased. Taking care for the patient in a post-ICU outpatient department during this time will help to recognize these problems and to effectively treat the patient as soon as possible.     

A theory of the dual pathways for smooth pursuit based on dynamic gain control

The smooth pursuit eye movement (SPEM) system is much more sensitive to target motion perturbations during pursuit than during fixation. This sensitivity is commonly attributed to a dynamic gain control mechanism. Neither the neural substrate nor the functional architecture for this gain control has been fully revealed. There are at least two cortical areas that crucially contribute to smooth pursuit and are therefore eligible sites for dynamic gain control: the medial superior temporal area (MST) and the pursuit area of the frontal eye fields (FEFs), which both project to brain stem premotor structures via parallel pathways. The aim of this study was to develop a model of smooth pursuit based on behavioral, anatomical, and neurophysiological results to account for nonlinear dynamic gain control. Using a behavioral paradigm in humans consisting of a sinusoidal oscillation (4 Hz, +/-8 degrees/s) superimposed on a constant velocity target motion (0-24 degrees/s), we were able to identify relevant gain control parameters in the model. A salient feature of our model is the emergence of two parallel pathways from higher visual cortical to lower motor areas in the brain stem that correspond to the MST and FEF pathways. Detailed analysis of the model revealed that one pathway mainly carries eye velocity related signals, whereas the other is associated mostly with eye acceleration. From comparison with known neurophysiological results we conclude that the dynamic gain control can be attributed to the FEF pathway, whereas the MST pathway serves as the basic circuit for maintaining an ongoing SPEM.     

Ivabradine in combination with beta-blocker improves symptoms and quality of life in patients with stable angina pectoris: results from the ADDITIONS study

Aim

Several clinical trials have demonstrated the antianginal and anti-ischemic efficacy of ivabradine in combination with beta-blocker in patients with stable angina pectoris. The ADDITIONS (PrActical Daily efficacy anD safety of Procoralan^® In combinaTION with betablockerS) study evaluated the efficacy, safety, and tolerability of ivabradine added to beta-blocker, and its effect on angina symptoms and quality of life in routine clinical practice.

Methods

This non-interventional, multicenter, prospective study included 2,330 patients with stable angina pectoris treated with a flexible dose of ivabradine twice daily in addition to beta-blocker for 4 months. The parameters recorded included heart rate, number of angina attacks, nitrate consumption, tolerance, and quality of life.

Results

After 4 months ivabradine (mean dose 12.37 ± 2.95 mg/day) reduced heart rate by 19.4 ± 11.4 to 65.6 ± 8.2 bpm (p < 0.0001). The number of angina attacks was reduced by 1.4 ± 1.9 per week (p < 0.0001), and nitrate consumption by 1.9 ± 2.9 U per week (p < 0.0001). At baseline (i.e., on beta-blocker), half of the patients (51%) were classified as Canadian Cardiovascular Society (CCS) grade II; 29% were CCS grade I. After 4 months’ treatment with ivabradine, most of the patients were CCS grade I (68%). The EQ-5D index improved by 0.17 ± 0.23 (p < 0.0001). The overall efficacy of ivabradine was considered by the physicians as “very good” (61%) or “good” (36%) in most patients. Suspected adverse drug reactions were documented in 14 patients; none were severe.

Conclusion

In daily clinical practice, combining ivabradine with beta-blocker not only reduces heart rate, number of angina attacks, and nitrate consumption, but also improves the quality of life in patients with stable angina pectoris.

     

Harninkontinenz nach vaginaler Entbindung oder Sectio caesarea

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