Endothelial cell nitric oxide production in acute chest syndrome

Acute chest syndrome (ACS) is the most common form of acute pulmonary disease associated with sickle cell disease. To investigate the possibility that alterations in endothelial cell (EC) production and metabolism of nitric oxide (NO) products might be contributory, we measured NO products from cultured pulmonary EC exposed to red blood cells and/or plasma from sickle cell patients during crisis. Exposure to plasma from patients with ACS caused a 5- to 10-fold increase in S-nitrosothiol (RSNO) and a 7- to 14-fold increase in total nitrogen oxide (NO(x)) production by both pulmonary arterial and microvascular EC. Increases occurred within 2 h of exposure to plasma in a concentration-dependent manner and were associated with increases in endothelial nitric oxide synthase (eNOS) protein and eNOS enzymatic activity, but not with changes in nitric oxide synthase (NOS) III or NOS II transcripts, inducible NOS (iNOS) protein nor iNOS enzymatic activity. RSNO and NO(x) increased whether plasma was obtained from patients with ACS or other forms of vasoocclusive crisis. Furthermore, an oxidative state occurred and oxidative metabolites of NO, particularly peroxynitrite, were produced. These findings suggest that altered NO production and metabolism to damaging oxidative molecules contribute to the pathogenesis of ACS.

Weaning from mechanical ventilation

In this review, traditional weaning parameters, integrative indexes, and experimental methods of predicting weaning outcomes have been reviewed. All have limitations; however, judicious application of these parameters may guide clinical decisions regarding timing of weaning trials. Of the parameters reviewed, the RSBI has several advantages and may identify patients who are candidates for weaning. Likewise, application of tools such as the daily screen or implementation of multidisciplinary weaning teams may assist clinicians in weaning patients earlier in their ICU course. Most patients will be successfully extubated after a single SBT, and weaning methods that focus on sequential decrements in ventilator support appear to needlessly prolong ventilation. However, for patients who fail, identification of potential causes of continued ventilator dependence should focus on the various pathophysiological causes outlined. Although a number of patients will require prolonged ventilator support beyond the critical care setting, the growing experience with this population demonstrates that a large percentage have favorable outcomes.

Erosion of the right mainstem bronchus by an esophageal stent

Self-expanding metallic stents (SEMSs) are used to palliate malignant esophageal strictures. We describe a patient who had an extensive mediastinal tumor for which he was receiving irradiation therapy; chest pain, hemoptysis, and recurrent Gram-negative pneumonia developed in this patient after stent placement. Fiberoptic bronchoscopy revealed protrusion of the SEMS into the tracheobronchial tree, a novel complication for this new type of stent.