Harrison W. Farber

Nosocomial pneumonia in intubated patients given sucralfate as compared with antacids or histamine type 2 blockers. The role of gastric colonization

Gram-negative nosocomial pneumonia may result from retrograde colonization of the pharynx from the stomach, and this may be more likely when the gastric pH is relatively high. We studied the rate of nosocomial pneumonia among 130 patients given mechanical ventilation in an intensive care unit who were receiving as prophylaxis for stress ulcer either sucralfate (n = 61), which does not raise gastric pH, or conventional treatment with antacids, histamine type 2 (H2) blockers, or both (n = 69). At the time of randomization to treatment, the two groups were similar in age, underlying diseases, and severity of acute illness. Patients in the sucralfate group had a higher proportion of gastric aspirates with a pH less than or equal to 4 (P less than 0.001) and significantly lower concentrations of gram-negative bacilli (P less than 0.05) in gastric aspirates, pharyngeal swabs, and tracheal aspirates than did patients in the antacid-H2-blocker group. The rate of pneumonia was twice as high in the antacid-H2 group as in the sucralfate group (95 percent confidence interval, 0.89 to 4.58; P = 0.11). Gram-negative bacilli were isolated more frequently from the tracheal aspirates of patients with pneumonia who were receiving antacids or H2 blockers. Mortality rates were 1.6 times higher in the antacid-H2 group than in the sucralfate group (95 percent confidence interval, 0.99 to 2.50; P = 0.07). Although our results fell just short of statistical significance when they were analyzed according to intention to treat, they suggest that agents that elevate gastric pH increase the risk of nosocomial pneumonia in patients receiving ventilation by favoring gastric colonization with gram-negative bacilli. We conclude that in patients receiving mechanical ventilation, the use of a prophylactic agent against stress-ulcer bleeding that preserves the natural gastric acid barrier against bacterial overgrowth may be preferable to antacids and H2 blockers.

Pulmonary Arterial Hypertension : Baseline Characteristics From the REVEAL Registry

BACKGROUND The Registry to EValuate Early And Long-term pulmonary arterial hypertension disease management (REVEAL Registry) was established to provide updated characteristics of patients with pulmonary arterial hypertension (PAH) and to improve diagnosis, treatment, and management. METHODS Fifty-four US centers enrolled consecutively screened patients with World Health Organization group I PAH who met expanded hemodynamic criteria of mean pulmonary arterial pressure (PAP) > 25 mm Hg at rest (30 mm Hg with exercise), pulmonary capillary wedge pressure (PCWP) <or= 18 mm Hg, and pulmonary vascular resistance >or= 240 dynes x s x cm(-5). Patients meeting the traditional hemodynamic definition (PCWP <or= 15 mm Hg) were compared with those with a PCWP of 16 to 18 mm Hg. RESULTS Between March 2006 and September 2007, 2,967 patients enrolled. Among 2,525 adults meeting traditional hemodynamic criteria, the mean age was 53 +/- 14 years, and 2,007 (79.5%) were women. The mean duration between symptom onset and diagnostic catheterization was 2.8 years, and 1,008 (41.3%) patients were treated with more than one pulmonary vascular-targeted medication. Compared with patients meeting the traditional hemodynamic definition of PAH, patients with a PCWP of 16 to 18 mm Hg were older, more obese, had a lower 6-min walk distance, and had a higher incidence of systemic hypertension, sleep apnea, renal insufficiency, and diabetes. CONCLUSIONS Patients in the REVEAL Registry are older and more often female than in previous descriptions. Delays between symptom onset and diagnostic catheterization persist. Many treatment regimens are fundamentally empirical, and data will be required to determine outcomes, improve risk stratification, and develop and validate more precise prognostic tools. Patients with PCWP of 16 to 18 mm Hg differ in a number of important respects from those meeting the traditional hemodynamic definition of PAH.

Endothelial dysfunction in a murine model of mild hyperhomocyst(e)inemia

Homocysteine is a risk factor for the development of atherosclerosis and its thrombotic complications. We have employed an animal model to explore the hypothesis that an increase in reactive oxygen species and a subsequent loss of nitric oxide bioactivity contribute to endothelial dysfunction in mild hyperhomocysteinemia. We examined endothelial function and in vivo oxidant burden in mice heterozygous for a deletion in the cystathionine beta-synthase (CBS) gene, by studying isolated, precontracted aortic rings and mesenteric arterioles in situ. CBS(-/+) mice demonstrated impaired acetylcholine-induced aortic relaxation and a paradoxical vasoconstriction of mesenteric microvessels in response to superfusion of methacholine and bradykinin. Cyclic GMP accumulation following acetylcholine treatment was also impaired in isolated aortic segments from CBS(-/+) mice, but aortic relaxation and mesenteric arteriolar dilation in response to sodium nitroprusside were similar to wild-type. Plasma levels of 8-epi-PGF(2alpha) (8-IP) were somewhat increased in CBS(-/+) mice, but liver levels of 8-IP and phospholipid hydroperoxides, another marker of oxidative stress, were normal. Aortic tissue from CBS(-/+) mice also demonstrated greater superoxide production and greater immunostaining for 3-nitrotyrosine, particularly on the endothelial surface. Importantly, endothelial dysfunction appears early in CBS(-/+) mice in the absence of structural arterial abnormalities. Hence, mild hyperhomocysteinemia due to reduced CBS expression impairs endothelium-dependent vasodilation, likely due to impaired nitric oxide bioactivity, and increased oxidative stress apparently contributes to inactivating nitric oxide in chronic, mild hyperhomocysteinemia.

Nutritional outcome and pneumonia in critical care patients randomized to gastric versus jejunal tube feedings

ObjectiveTo compare nutritional status, gastric colonization, and rates of nosocomial pneumonia in ICU patients randomized to gastric tube feeding vs. patients fed by an endoscopically placed jejunal tube. DesignRandomized, prospective study. SettingMedical and surgical ICUs at Boston City Hospital; surgical ICU at University Hospital. PatientsOf the 38 study patients, 19 were randomized to gastric tube feeding and 19 were randomized to an endoscopically placed jejunal tube. The two groups were similar in age, sex, race, underlying disease, and type of surgery. ResultsThe two patient groups were similar in number of days fed, duration of ICU stay, duration of mechanical ventilation, days of antibiotic therapy, and days with fever. Compared with the gastric group, the jejunal group had more patients with circulatory shock on admission (79% vs. 68.4%), higher admission Acute Physiology Score (24.0 vs. 21.7), and fewer patients with pneumonia at randomization (26.3% vs. 31.6%). The jejunal group received a significantly higher percentage of their daily goal caloric intake (p = .05), and had greater increases in serum prealbumin concentrations (p <.05) than the patients with gastric tube feeding. Although the jejunal tube group had more days of diarrhea (3.3 ±PT 6.6 vs. 1.8 ±PT 2.9), this difference was not statistically significant. Nosocomial pneumonia was diagnosed clinically in two (10.5%) patients in the gastric tube group and in no patients in the jejunal tube group. ConclusionsPatients fed by jejunal tube received a significantly higher proportion of their daily goal caloric intake, had a significantly greater increase in serum prealbumin concentrations, and had a lower rate of pneumonia than patients fed by continuous gastric tube feeding.

The changing picture of patients with pulmonary arterial hypertension in the United States: How REVEAL differs from historic and non-US contemporary registries

BACKGROUND REVEAL (The Registry to Evaluate Early and Long-term Pulmonary Arterial Hypertension Disease Management) provides current demographics of patients with group 1 pulmonary arterial hypertension (PAH) in the United States. METHODS A total of 2,967 patients with PAH diagnosed based on right-sided heart catheterization were enrolled in REVEAL between March 2006 and September 2007. Demographics from the REVEAL patient cohort and REVEAL subpopulations (matched by inclusion criteria to other registries) were compared with historic US registry data and other contemporary US and non-US national PAH registries by inclusion criteria, including the National Institutes of Health (NIH) PAH registry and the French PAH registry. RESULTS REVEAL patients matched to NIH registry patients were older at diagnosis (mean ± SE, 44.9 ± 0.6 years vs 36.4 ± 1.1 years; difference, 8.5 ± 1.4; P < .001) and more likely to be women (78.7 ± 1.2% vs 63.1 ± 3.5%; P < .001). REVEAL patients matched to French registry patients had similar age and severity at diagnosis, but REVEAL patients were more likely to be women (79.8 ± 0.8% vs 65.3 ± 1.8%; P < .001) and obese (BMI, ≥ 30 kg/m(2), 32.5 ± 1.0% vs 14.8 ± 1.4%; P < .001), whereas French patients were more likely to have HIV-associated PAH (6.2% vs 2.3%). The female preponderance is similar to that in other US-based contemporary registries. CONCLUSIONS At diagnosis, REVEAL patients were older than NIH registry patients and similar in age to patients enrolled in contemporary registries. Compared with NIH and contemporary European and UK registries, there was a striking preponderance of women, and REVEAL patients were more likely to be obese. These observations and the difference in HIV-associated PAH between REVEAL and other non-US contemporary registries warrant further investigation. TRIAL REGISTRY ClinicalTrials.gov; No.: NCT00370214; URL: clinicaltrials.gov.

Imatinib Mesylate in the Treatment of Refractory Idiopathic Pulmonary Arterial Hypertension

TO THE EDITOR: I read the study by Roy and colleagues (1) with great interest. However, one thing puzzled me. In their Figure 2, the authors showed that pulmonary embolism (PE) had appropriately been ruled out when spiral computed tomography (CT) and enzyme-linked immunosorbent assay (ELISA) D-dimer results were negative in the low clinical probability group and that only a negative D-dimer result is sufficient to rule out PE in the high probability group. From basic epidemiology and studies concerning the value of D-dimer in the diagnosis of PE, we know that a negative D-dimer result provides high certainty for excluding PE (low post-test probability of PE). On the other hand, a negative D-dimer result in a group with a high a priori chance is insufficient to rule out PE (higher post-test probability of PE) (2). Could an error have occurred?

Identification of an oxygen responsive enhancer element in the glyceraldehyde-3-phosphate dehydrogenase gene

The glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is induced by hypoxia in endothelial cells (EC). Upregulation occurs primarily at the level of transcription and occurs to a much greater extent in EC than in other cell types. To characterize EC specific hypoxia response elements within the GAPDH gene, we performed transient transfection studies in EC, fibroblasts and smooth muscle cells using portions of the GAPDH promoter linked to a CAT reporter gene. These initial studies identified an EC specific hypoxia responsive region that was further characterized (using SV40-promoter-CAT reporter constructs) as a 19-nucleotide sequence (-130 to -112) containing both an hypoxia inducible factor-1 (HIF-1)-binding site and a novel flanking sequence. Electrophoretic mobility shift assays confirmed inducible EC protein binding to this fragment. Mutation of either the HIF-1-binding site or the flanking sequence resulted in complete loss of function and loss of inducible protein binding. Thus, a single HIF-1-binding site is necessary, but not sufficient, for hypoxic regulation of GAPDH in EC. Furthermore, the novel HIF-1 flanking sequence required for GAPDH upregulation and the protein(s) that bind to it may be EC specific.

VEGF is deposited in the subepithelial matrix at the leading edge of branching airways and stimulates neovascularization in the murine embryonic lung

We used whole lung cultures as a model to study blood vessel formation in vitro and to examine the role that epithelial‐mesenchymal interactions play during embryonic pulmonary vascular development. Mouse lungs were isolated at embryonic day 11.5 (E11.5) and cultured for up to 4 days prior to blood vessel analysis. Platelet endothelial cell adhesion molecule‐1 (PECAM/CD31) and thrombomodulin (TM/CD141) immunolocalization demonstrate that vascular development occurs in lung cultures. The vascular structures identified in lung cultures first appear as a loosely associated plexus of capillary‐like structures that with time surround the airways. To investigate the potential role of vascular endothelial cell growth factor (VEGF) during pulmonary neovascularization, we immunolocalized VEGF in embryonic lungs. Our data demonstrate that VEGF is uniformly present in the airway epithelium and the subepithelial matrix of E11.5 lungs. At later time points, E13.5 and E15.5, VEGF is no longer detected in the proximal airways, but is restricted to the branching tips of airways in the distal lung. RT‐PCR analysis reveals that VEGF164 is the predominant isoform expressed in lung cultures. Grafting heparin‐bound VEGF164 beads onto lung explants locally stimulates a marked neovascular response within 48 hr in culture. Semi‐quantitative RT‐PCR reveals an 18% increase in PECAM mRNA in VEGF164‐treated whole lung cultures as compared with untreated cultures. The restricted temporal and spatial expression of VEGF suggests that matrix‐associated VEGF links airway branching with blood vessel formation by stimulating neovascularization at the leading edge of branching airways.

Role of free radicals in the pathogenesis of acute chest syndrome in sickle cell disease

Acute chest syndrome (ACS) of sickle cell disease (SCD) is characterized pathologically by vaso-occlusive processes that result from abnormal interactions between sickle red blood cells (RBCs), white blood cells (WBCs) and/or platelets, and the vascular endothelium. One potential mechanism of vascular damage in ACS is by generation of oxygen-related molecules, such as superoxide (O2-), hydrogen peroxide (H2O2), peroxynitrite (ONOO-), and the hydroxyl (•OH) radical. The present review summarizes the evidence for alterations in oxidant stress during ACS of SCD, and the potential contributions of RBCs, WBCs and the vascular endothelium to this process.

Delay in recognition of pulmonary arterial hypertension: factors identified from the REVEAL Registry.

BACKGROUND Pulmonary arterial hypertension (PAH) is a progressive and fatal disorder. Despite the emergence of effective therapy, PAH is commonly at an advanced stage when recognized. Factors associated with a prolonged symptomatic period before the recognition of PAH have not been fully evaluated. METHODS The Registry to Evaluate Early and Long-term PAH Disease Management (REVEAL Registry) enrolled 2,967 US adult patients with PAH from March 2006 to September 2007. Patients were considered to have delayed disease recognition if > 2 years elapsed between symptom onset and the patient receiving a PAH diagnosis, starting on PAH-specific therapy, or receiving a diagnosis by right-sided heart catheterization. RESULTS In 21.1% of patients, symptoms were experienced for > 2 years before PAH was recognized. Patients with onset of PAH symptoms before age 36 years showed the highest likelihood of delayed disease recognition (OR, 3.07; 95% CI, 2.03-4.66). History of obstructive airways disease (OR, 1.93; 95% CI, 1.5-2.47) and sleep apnea (OR, 1.72; 95% CI, 1.33-2.22) were independently associated with delayed PAH recognition. Six-minute walk distance < 250 m (OR, 1.91; 95% CI, 1.16-3.13), right atrial pressure < 10 mm Hg (OR, 1.77; 95% CI, 1.26-2.48), and pulmonary vascular resistance < 10 Wood units (OR, 1.28; 95% CI, 1.02-1.60) were also associated with delayed disease recognition, but sex, race/ethnicity, and geographic region showed no association. CONCLUSIONS One in five patients in the REVEAL Registry who were diagnosed with PAH reported symptoms for > 2 years before their disease was recognized. Younger individuals and patients with histories of common respiratory disorders were most likely to experience delayed PAH recognition. TRIAL REGISTRY ClinicalTrials.gov; No.: NCT00370214; URL: www.clinicaltrials.gov.