Citations

Background —Experimental hypercholesterolemia (HC) impairs intramyocardial microvascular function. However, whether this is associated with alterations in microvascular architecture remained unknown. Using a novel 3D micro-CT scanner, we tested the hypothesis that HC is associated with an alteration in the microvascular architecture. Methods and Results —Pigs were euthanized after 12 weeks of either normal (n=6) or 2% HC (n=6) diet. The hearts were excised and the coronary arteries injected with a radiopaque contrast material. Myocardial samples were scanned with micro-CT, and 3D images were reconstructed with 21-μm cubic voxels. The myocardium was tomographically subdivided into subepicardium and subendocardium, and microvessels (<500 μm in diameter) were counted in situ within each region. In the subendocardium of HC pigs, the intramyocardial density of microvessels was significantly higher than in normal animals (1221.4±199.7 versus 758.3±90.8 vessels/cm 3 , P <0.05) because of an increase in the number of microvessels <200 μm in diameter (1214.4±199.7 versus 746.6±101.5 vessels/cm 3 , P <0.05). The subepicardial vascular density was similar in both groups. Conclusions —HC has differential effects on the spatial density of the subendocardial microvasculature that may play a role in regulation and/or spatial distribution of myocardial blood flow. This study also demonstrates the feasibility of studying myocardial microvascular architecture with micro-CT in pathophysiological states.

BACKGROUND Transient bacteremia may lead to endocarditis in patients with significant valvular lesions. METHODS AND RESULTS Because transesophageal echocardiography selects a patient population with a high prevalence of valvular lesions, we prospectively evaluated the risk of transient bacteremia associated with transesophageal echocardiography in 49 patients. Blood cultures were obtained immediately before transesophageal echocardiography and at 5, 10, and 20 minutes after the start of the procedure. For each culture, 30 ml venous blood was obtained and 10 ml was inoculated into each of an Isolator tube, Septi-chek bottle, and a nonvented Trypticase soy broth bottle. Broth cultures were incubated for 14 days. Blood from the Isolator tube was plated onto appropriate media for recovery of bacteria and fungi. Two patients were excluded from analysis because the final two sets of blood cultures could not be obtained. Among the remaining 47 study patients, two preprocedure control blood cultures were positive, and two of 141 subsequent cultures were positive. All isolates were considered contaminants. Thus, we found no significant bacteremia due to pathogenic oral flora during transesophageal echocardiography (0%; 95% CI, 0.0-7.5%). CONCLUSIONS Although recommendations for antimicrobial prophylaxis for transesophageal echocardiography should be individualized for each patient, many patients may not require antimicrobial prophylaxis.

BACKGROUND: Optimal titration of inspired oxygen is important to prevent hyperoxia in mechanically ventilated patients in ICUs. There is mounting evidence of the deleterious effects of hyperoxia; however, there is a paucity of data about F IO 2 practice and oxygen exposure among patients in ICUs. We therefore sought to assess excessive F IO 2 exposure in mechanically ventilated patients with acute lung injury and to evaluate the effect on pulmonary outcomes. METHODS: From a database of ICU patients with acute lung injury identified by prospective electronic medical record screening, we identified those who underwent invasive mechanical ventilation for > 48 hours from January 1 to December 31, 2008. Ventilator settings, including F IO 2 and corresponding S pO 2 , were collected from the electronic medical record at 15-min intervals for the first 48 hours. Excessive F IO 2 was defined as F IO 2 > 0.5 despite S pO 2 > 92%. The association between the duration of excessive exposure and pulmonary outcomes was assessed by change in oxygenation index from baseline to 48 hours and was analyzed by univariate and multivariate linear regression analysis. RESULTS: Of 210 patients who met the inclusion criteria, 155 (74%) were exposed to excessive F IO 2 for a median duration of 17 hours (interquartile range 7.5–33 h). Prolonged exposure to excessive F IO 2 correlated with worse oxygenation index at 48 hours in a dose-response manner ( P < .001.). Both exposure to higher F IO 2 and longer duration of exposure were associated with worsening oxygenation index at 48 hours ( P < .001), more days on mechanical ventilation, longer ICU stay, and longer hospital stay ( P = .004). No mortality difference was noted. CONCLUSIONS: Excessive oxygen supplementation is common in mechanically ventilated patients with ALI and may be associated with worsening lung function.

Object Near-infrared spectroscopy (NIRS) offers noninvasive bedside measurement of direct regional cerebral arteriovenous (mixed) brain oxygenation. To validate the accuracy of this monitoring technique, the authors analyzed the statistical correlation of NIRS and CT perfusion with respect to regional cerebral blood flow (CBF) measurements. Methods The authors retrospectively reviewed all cases in which NIRS measurements were obtained at a single, academic neurointensive care unit from February 2008 to June 2011 in which CT perfusion was performed at the same time as NIRS data was collected. Regions of interest were obtained 2.5 cm below the NIRS bifrontal scalp probe on CT perfusion with an average volume between 2 and 4 ml, with mean CBF values used for purposes of analysis. Linear regression analysis was performed for NIRS and CBF values. Results The study included 8 patients (2 men, 6 women), 6 of whom suffered subarachnoid hemorrhage, 1 ischemic stroke, and 1 intracerebral hemorrhage and brain edema. Mean CBF measured by CT perfusion was 61 ml/100 g/min for the left side and 60 ml/100 g/min for the right side, while mean NIRS values were 75 on the right and 74 on the left. Linear regression analysis demonstrated a statistically significant probability value (p < 0.0001) comparing NIRS frontal oximetry and CT perfusion–obtained CBF values. Conclusions The authors demonstrated a linear correlation for frontal NIRS cerebral oxygenation measurements compared with regional CBF on CT perfusion imaging. Thus, frontal NIRS cerebral oxygenation measurement may serve as a useful, noninvasive, bedside intensive care unit monitoring tool to assess brain oxygenation in a direct manner.

Abstract Rationale Transfusion-related pulmonary complications are leading causes of morbidity and mortality attributed to transfusion. Observational studies suggest an important role for red blood cell (RBC) storage duration in these adverse outcomes. Objectives To evaluate the impact of RBC storage duration on short-term pulmonary function as well as immunologic and coagulation status in mechanically ventilated patients receiving RBC transfusion. Methods This is a double-blind, randomized, clinical trial comparing fresh (≤5 d of storage) versus standard issue single-unit RBC transfusion in adult intubated and mechanically ventilated patients. The primary outcome is the change in pulmonary gas exchange as assessed by the partial pressure of arterial oxygen to fraction of inspired oxygen concentration ratio (ΔPaO2/FiO2). Secondary outcomes include changes in immune and coagulation status. Measurements and Main Results Fifty patients were randomized to receive fresh RBCs and an additional 50 patients to standard issue RBCs. Median storage age was 4.0 days (interquartile range, 3.0–5.0) and 26.5 days (interquartile range, 21.0–36.0) in the fresh RBC group and standard issue RBC group, respectively. No differences were noted in the primary outcome of ΔPaO2/FiO2 (difference between the mean ΔPaO2/FiO2 in the standard issue RBC group vs. the fresh RBC group, –11.5; 95% confidence interval, −35.3 to 12.3; P = 0.22). Similarly, no significant differences were noted in markers of immunologic or coagulation status. Conclusions In this randomized clinical trial, no differences were noted in early measures of pulmonary function or in immunologic or coagulation status when comparing fresh versus standard issue single-unit RBC transfusion. Clinical trial registered with ClinicalTrials.gov (NCT00751322).