Visualization of fidaxomicin association with the exosporium layer of Clostridioides difficile spores.

BACKGROUND: Fidaxomicin has novel pharmacologic effects on C. difficile spore formation including outgrowth inhibition and persistent spore attachment. However, the mechanism of fidaxomicin attachment on spores has not undergone rigorous microscopic studies. MATERIALS & METHODS: Fidaxomicin attachment to C. difficile spores of three distinct ribotypes and C. difficile mutant spores with inactivation of exosporium or spore-coat protein-coding genes were visualized using confocal microscopy with a fidaxomicin-bodipy compound (green fluorescence). The pharmacologic effect of the fidaxomicin-bodipy compound was determined. Confocal microscopy experiments included direct effect on C. difficile wild-type and mutant spores, effect of exosporium removal, and direct attachment to a comparator spore forming organism, Bacillus subtilis. RESULTS: The fidaxomicin-bodipy compound MIC was 1 mg/L compared to 0.06 mg/L for unlabeled fidaxomicin, a 16-fold increase. Using confocal microscopy, the intracellular localization of fidaxomicin into vegetative C. difficile cells was observed consistent with its RNA polymerase mechanism of action and inhibited spore outgrowth. The fidaxomicin-bodipy compound was visualized outside of the core of C. difficile spores with no co-localization with the membrane staining dye FM4-64. Exosporium removal reduced fidaxomicin-bodipy association with C. difficile spores. Reduced fidaxomicin-bodipy was observed in C. difficile mutant spores for the spore surface proteins CdeC and CotE. CONCLUSION: This study visualized a direct attachment of fidaxomicin to C. difficile spores that was diminished with mutants of specific exosporium and spore coat proteins. These data provide advanced insight regarding the anti-spore properties of fidaxomicin.

Redistribution of pulmonary blood flow impacts thermodilution-based extravascular lung water measurements in a model of acute lung injury.

BACKGROUND: Studies using transthoracic thermodilution have demonstrated increased extravascular lung water (EVLW) measurements attributed to progression of edema and flooding during sepsis and acute lung injury. The authors hypothesized that redistribution of pulmonary blood flow can cause increased apparent EVLW secondary to increased perfusion of thermally silent tissue, not increased lung edema. METHODS: Anesthetized, mechanically ventilated canines were instrumented with PiCCO (Pulsion Medical, Munich, Germany) catheters and underwent lung injury by repetitive saline lavage. Hemodynamic and respiratory physiologic data were recorded. After stabilized lung injury, endotoxin was administered to inactivate hypoxic pulmonary vasoconstriction. Computed tomographic imaging was performed to quantify in vivo lung volume, total tissue (fluid) and air content, and regional distribution of blood flow. RESULTS: Lavage injury caused an increase in airway pressures and decreased arterial oxygen content with minimal hemodynamic effects. EVLW and shunt fraction increased after injury and then markedly after endotoxin administration. Computed tomographic measurements quantified an endotoxin-induced increase in pulmonary blood flow to poorly aerated regions with no change in total lung tissue volume. CONCLUSIONS: The abrupt increase in EVLW and shunt fraction after endotoxin administration is consistent with inactivation of hypoxic pulmonary vasoconstriction and increased perfusion to already flooded lung regions that were previously thermally silent. Computed tomographic studies further demonstrate in vivo alterations in regional blood flow (but not lung water) and account for these alterations in shunt fraction and EVLW.

Total and regional lung volume changes during high-frequency oscillatory ventilation (HFOV) of the normal lung.

The effect of high-frequency oscillatory ventilation (HFOV) settings on the distribution of lung volume (V(L)) with changes in mean airway pressure (Paw), frequency (f(R)) and tidal volume (V(T)) remains controversial. We used computer tomographic (CT) imaging to quantify the distribution of V(L) during HFOV compared to static continuous positive airway pressure (CPAP). In anesthetized, supine canines, CT imaging of the entire lung was performed during CPAP and HFOV at Paw of 5, 12.5 and 20 cm H(2)O, f(R)=5, 10, 15 Hz. We found small, statistically significant decreases compared with CPAP in total and regional V(L) during HFOV that were greatest at lower f(R) and Paw. Apex and base sub-volumes underwent changes comparable to the lung overall. Increases in f(R) were accompanied by increases in Pa(O)(2). These finding provide additional insight into the impact of HFOV settings on the distribution of V(L) and suggest that there is low risk of occult regional over-distention during HFOV in normal lungs.

Same-day cardiac catheter ablation is safe and cost-effective: Experience from a UK tertiary center.

BACKGROUND: Catheter ablation is a curative intervention for common arrhythmias such as supraventricular tachycardia and atrial flutter. Many centers still admit patients overnight after this procedure. OBJECTIVE: This study was performed to evaluate the safety and cost-effectiveness of same-day standard catheter ablation. METHODS: We conducted a retrospective study of all consecutive elective same-day procedures performed between 2010 and 2014. Data were collected on baseline parameters, procedure details and success, postoperative complications, unplanned overnight hospital admissions, and clinical outcome (including mortality) at 4-month follow-up. A cost analysis of potential savings was also performed. RESULTS: A total of 1142 patients underwent planned same-day electrophysiological study with or without ablation. Radiofrequency ablation was performed in 897 of these patients (mean age ± standard error 56 ± 0.6 years, range 16-95 years, 467 males), with 921 arrhythmias ablated and with complete procedural success in 883 cases (96%). There were 92 unplanned admissions (10.3%): 50 for concealed pathways that required transseptal puncture, 19 for immediate complications (including 9 femoral bleeds and 5 pacemakers for heart block), 12 admitted at the operator's discretion, and 11 for other clinical reasons. All had transthoracic echocardiography after the procedure, and none had significant pericardial effusion. At 4-month follow-up, there were 16 readmissions (1 deep vein thrombosis, 3 pericarditic chest pain, 2 femoral hematomas, 7 palpitations, and 3 others) and 1 death (unrelated to ablation). An overnight stay at our center costs $450 (£300); same-day ablation over this period saved our institution $365,000 (£240,000). CONCLUSION: Same-day standard catheter ablation is safe and cost-effective, with significant benefits for patients and health care providers. This is particularly important given the current financial climate.

Hemodynamic changes following the administration of propofol to facilitate endotracheal intubation during sevoflurane anesthesia.

BACKGROUND: The common intravenous anesthetic agent, propofol, is frequently reported to have negative inotropic and chronotropic effects. In the pediatric population, propofol is commonly used after inhalation induction to facilitate endotracheal intubation without the need for a neuromuscular blocking drug agent. In this setting, we have noted that propofol administration is commonly followed by tachycardia. The current study prospective evaluates heart rate and blood pressure changes following the administration of propofol to pediatric patients anesthetized with nitrous oxide (N2O) and sevoflurane. METHODS: ASA class 1 and 2 pediatric surgical patients were enrolled in the study. After premedication with midazolam and inhalation induction with N2O in oxygen and sevoflurane, a bolus dose of propofol was administered to facilitate endotracheal intubation. Heart rate (HR) was measured at baseline and at 30 second intervals following propofol administration. Blood pressure (MAP) was measured at baseline and 120 seconds post-administration. RESULTS: The study cohort consisted of 40 patients who ranged in age from 1 to 15 years. After inhalation induction, propofol (average dose of 2.6 mg/kg) was administered. The end-tidal N2O and sevoflurane concentrations were 62.2 ± 10.3% and 5.7 ± 1.1% respectively. Nineteen of 40 patients had a HR increase >10 bpm. When comparing these patients to those who did not experience a HR increase >10 bpm, there were no differences in the demographic data. Those with a HR increase received a greater dose of propofol when compared to patients whose HR change was <10 bpm (3.0 ± 0.8 versus 2.2 ± 0.5 mg/kg; p=0.0007). There was a significantly greater decreased in the MAP at 120 seconds following propofol administration in the group that did not sustain a >10 bpm HR increase. CONCLUSION: Tachycardia following propofol administration occurs in approximately 50% of pediatric patients despite preceding inhalation induction and concurrent administration of N2O and sevoflurane. Future studies are needed to define the mechanism for this effect.