Infective Endocarditis Due to Kingella kingae.

Infective endocarditis due to Kingella kingae is a rare but serious invasive infection that occurs mostly in children. Recent advances in nucleic acid amplification testing as well as in cardiac imaging have enabled more accurate diagnosis. A good understanding of the epidemiology and virulence factors remains crucial to guide the therapeutic approach. Here, we synthesize the current state of knowledge on epidemiological features, pathophysiological insights, complications, and therapy regarding Kingella kingae endocarditis in children and adults. Finally, throughout this comprehensive review, knowledge gaps and areas for future research are also identified.

Early and Late Postoperative Tachyarrhythmias in Children and Young Adults Undergoing Congenital Heart Disease Surgery.

The population of patients with congenital heart disease is constantly growing with an increasing number of individuals reaching adulthood. A significant proportion of these children and young adults will suffer from tachyarrhythmias due to the abnormal anatomy, the hemodynamic burden, or as a sequela of surgical treatment. Depending on the underlying mechanism, arrhythmias may arise in the early postoperative period (hours to days after surgery) or in the late postoperative period (usually years after surgery). A good understanding of the electrophysiological characteristics and pathophysiological mechanisms is therefore crucial to guide the therapeutic approach. Here, we synthesize the current state of knowledge on epidemiological features, risk factors, pathophysiological insights, electrophysiological features, and therapy regarding tachyarrhythmias in children and young adults undergoing reparative surgery for congenital heart disease. The evolution and latest data on treatment options, including pharmacological therapy, ablation procedures, device therapy decision, and thromboprophylaxis, are summarized. Finally, throughout this comprehensive review, knowledge gaps and areas for future research are also identified.

Blockade of the cholinergic system during sensitization enhances lung responsiveness to allergen in rats.

Although acute prophylactic administration of atropine modulates airway responsiveness, the role of the parasympathetic nervous system in the pathogenesis of sensitization and in antigen-induced bronchoconstriction remains unclear. The aim of the present study is to determine whether blocking muscarinic receptors during chronic allergen exposure modulates lung responsiveness to the specific allergen. Forty rats were randomly assigned to one of the following five treatment groups: sensitization with saline vehicle, intraperitoneal injection of ovalbumin (1 mg) with or without atropine treatment (10 mg/kg per day) and repeated ovalbumin aerosol (1.25 mg/mL for 20 minutes) either alone or combined with atropine. Lung responsiveness to methacholine (4-16 µg/kg per minute) and intravenous ovalbumin (2 mg) was established before and 21 days after treatment with forced oscillations following bilateral vagotomy. Lung cellularity was determined by analysis of bronchoalveolar lavage fluid (BALF). A lung inflammatory response in all sensitized animals was defined as an increase in the number of inflammatory cells in the BALF. Baseline respiratory mechanics and methacholine responsiveness on Days 0 and 21 were comparable in all groups. However, increases in airway resistance following intravenous allergen challenge were significantly exacerbated in rats that received atropine. Inhibition of the cholinergic nervous system during allergic sensitization potentiates bronchoconstriction following exposure to the specific allergen. These findings highlight the role of the cholinergic neuronal pathway in airway sensitization to a specific allergen.

Synchrotron Imaging Shows Effect of Ventilator Settings on Intrabreath Cyclic Changes in Pulmonary Blood Volume.

Despite the importance of dynamic changes in the regional distributions of gas and blood during the breathing cycle for lung function in the mechanically ventilated patient, no quantitative data on such cyclic changes are currently available. We used a novel gated synchrotron computed tomography imaging to quantitatively image regional lung gas volume (Vg), tissue density, and blood volume (Vb) in six anesthetized, paralyzed, and mechanically ventilated rabbits with normal lungs. Images were repeatedly collected during ventilation and steady-state inhalation of 50% xenon, or iodine infusion. Data were acquired in a dependent and nondependent image level, at zero end-expiratory pressure (ZEEP) and 9 cm H2O (positive end-expiratory pressure), and a tidal volume (Vt) of 6 ml/kg (Vt1) or 9 ml/kg (Vt2) at an Inspiratory:Expiratory ratio of 0.5 or 1.7 by applying an end-inspiratory pause. A video showing dynamic decreases in Vb during inspiration is presented. Vb decreased with positive end-expiratory pressure (P = 0.006; P = 0.036 versus Vt1-ZEEP and Vt2-ZEEP, respectively), and showed larger oscillations at the dependent image level, whereas a 45% increase in Vt did not have a significant effect. End-inspiratory Vb minima were reduced by an end-inspiratory pause (P = 0.042, P = 0.006 at nondependent and dependent levels, respectively). Normalized regional Vg:Vb ratio increased upon inspiration. Our data demonstrate, for the first time, within-tidal cyclic variations in regional pulmonary Vb. The quantitative matching of regional Vg and Vb improved upon inspiration under ZEEP. Further study is underway to determine whether these phenomena affect intratidal gas exchange.

Pressure-regulated volume control vs. volume control ventilation in healthy and injured rabbit lung: An experimental study.

BACKGROUND: It is not well understood how different ventilation modes affect the regional distribution of ventilation, particularly within the injured lung. OBJECTIVES: We compared respiratory mechanics, lung aeration and regional specific ventilation ((Equation is included in full-text article.)) distributions in healthy and surfactant-depleted rabbits ventilated with pressure-regulated volume control (PRVC) mode with a decelerating inspiratory flow or with volume control (VC) mode. DESIGN: Randomised experimental study. ANIMALS AND INTERVENTIONS: New Zealand white rabbits (n = 8) were anaesthetised, paralysed and mechanically ventilated either with VC or PRVC mode (tidal volume: 7 ml kg; rate: 40 min; positive end-expiratory pressure (PEEP): 3 cmH2O), at baseline and after lung injury induced by lung lavage. MAIN OUTCOME MEASURES: Airway resistance (Raw), respiratory tissue damping (G) and elastance (H) were measured by low-frequency forced oscillations. Synchrotron radiation computed tomography during stable xenon wash-in was used to measure regional lung aeration and specific ventilation and the relative fraction of nonaerated, trapped, normally, poorly and hyperinflated lung regions. RESULTS: Lung lavage significantly elevated peak inspiratory pressure (PIP) (P < 0.001). PIP was lower on PRVC compared with VC mode (-12.7 ±â€Š1.7%, P < 0.001). No significant differences in respiratory mechanics, regional ventilation distribution, strain or blood oxygenation could be detected between the two ventilation modes. CONCLUSION: A decelerating flow pattern (PRVC) resulted in equivalent regional ventilation distribution, respiratory mechanics and gas exchange, in both normal and mechanically heterogeneous lungs with, however, a significantly lower peak pressure. Our data suggest that the lower PIP on PRVC ventilation was because of the decelerating flow pattern rather than the ventilation distribution.

Surgical Repair of Mitral Valve Disease in Children: Perioperative Changes in Respiratory Function.

OBJECTIVE: To assess the profile of changes in airway and respiratory tissue mechanics within a follow-up study performed in children with mitral valve disease, before and after surgical valve repair. DESIGN: Perioperative measurements in a prospective, consecutive cross-sectional study. SETTING: University hospital, tertiary care teaching hospital PARTICIPANTS: The study comprised 24 children with congenital or post-rheumatic mitral valve insufficiency. INTERVENTIONS: Input impedance of the respiratory system during spontaneous breathing was measured before and 5 days and 3 weeks after mitral valve surgery. In addition, airway and respiratory tissue mechanics and pulmonary arterial pressure were assessed with the patient under general anesthesia preoperatively and immediately postoperatively. Respiratory tissue elastance and changes in airway measurements were estimated from forced oscillatory impedance data by fitting an appropriate model. MEASUREMENT AND MAIN RESULTS: Relating airway and respiratory tissue mechanics to previously established reference values obtained in age-matched healthy control patients revealed abnormal respiratory function (135±6.2% and 148±13% in respiratory elastance and resistance, respectively; p<0.001). Improvement in the airway properties was observed immediately after surgery (-15.2±3.4%; p<0.005) and lasted for the study period (-19±4.1%; p<0.001). Respiratory tissue elastance, which correlated preoperatively to the diastolic pulmonary arterial pressure, decreased only 5 days postoperatively (-20.6±4.1%; p<0.005). However, there was no evidence of a clear, immediate effect of surgery on the tissue mechanical parameters measured intraoperatively despite a decrease in diastolic pulmonary pressure. CONCLUSIONS: Mitral valve disease in children leads to abnormal airway and respiratory tissue mechanics. Even though surgical repair of mitral insufficiency alleviates abnormal airway function, residual lung tissue stiffening may persist even weeks after the surgery, contributing to a sustained impairment in lung function.

Effect of surfactant on regional lung function in an experimental model of respiratory distress syndrome in rabbit.

We assessed the changes in regional lung function following instillation of surfactant in a model of respiratory distress syndrome (RDS) induced by whole lung lavage and mechanical ventilation in eight anaesthetized, paralyzed, and mechanically ventilated New Zealand White rabbits. Regional specific ventilation (sV̇) was measured by K-edge subtraction synchrotron computed tomography during xenon washin. Lung regions were classified as poorly aerated (PA), normally aerated (NA), or hyperinflated (HI) based on regional density. A functional category was defined within each class based on sV̇ distribution (High, Normal, and Low). Airway resistance (Raw), respiratory tissue damping (G), and elastance (H) were measured by forced oscillation technique at low frequencies before and after whole lung saline lavage-induced (100 ml/kg) RDS, and 5 and 45 min after intratracheal instillation of beractant (75 mg/kg). Surfactant instillation improved Raw, G, and H (P < 0.05 each), and gas exchange and decreased atelectasis (P < 0.001). It also significantly improved lung aeration and ventilation in atelectatic lung regions. However, in regions that had remained normally aerated after lavage, it decreased regional aeration and increased sV̇ (P < 0.001) and sV̇ heterogeneity. Although surfactant treatment improved both central airway and tissue mechanics and improved regional lung function of initially poorly aerated and atelectatic lung, it deteriorated regional lung function when local aeration was normal prior to administration. Local mechanical and functional heterogeneity can potentially contribute to the worsening of RDS and gas exchange. These data underscore the need for reassessing the benefits of routine prophylactic vs. continuous positive airway pressure and early "rescue" surfactant therapy in very immature infants.