Stephen J. Huang

The confounding effects of age, gender, serum creatinine, and electrolyte concentrations on plasma B-type natriuretic peptide concentrations in critically ill patients.

ObjectiveTo investigate the confounding effects of age, gender, serum creatinine, and electrolyte concentrations on plasma B-type natriuretic peptide (BNP) concentrations in critically ill patients. DesignA prospective cross-sectional study. SettingA 20-bed general intensive care unit of a tertiary referral hospital. PatientsPatients were 121 patients admitted to the intensive care unit over a period of 9 wks. InterventionsIntravenous blood was collected for BNP measurements, and cardiac investigations including echocardiography were carried out for every patient on admission. Measurements and Main ResultsThe mean BNP concentration was 201 ± 317 pg/mL (n = 121). Thirty-five patients (28.9%), identified to have cardiac abnormalities, exhibited higher BNP concentrations than those without cardiac abnormalities (518 ± 394 vs. 60 ± 98 pg/mL, p < .001). The females exhibited higher concentrations of BNP than males in the noncardiac abnormality group (96 ± 132 pg/mL, n = 39 vs. 31 ± 38 pg/mL, n = 47, p = .016). BNP correlated significantly with age (r2 = .19) and creatinine (r2 = .084). The latter correlation became insignificant when patients with cardiac abnormality were excluded. No correlation was found between serum Na+ and K+ concentrations with BNP. Multivariate analyses demonstrated that the presence of cardiac abnormalities accounted for nearly 50% of the BNP variation. Addition of age and gender improved R2 to 60%. The contribution of creatinine was found to be insignificant. There was no association between BNP concentrations and serum Na+ and K+ concentrations. Logistic analysis confirmed that BNP is the strongest predictor for cardiac abnormalities in the critically ill patients. ConclusionThe current study demonstrated that plasma BNP concentrations increased with age and were higher in females than in males. Although the presence of cardiac disease was the most important determinant for BNP variations, age and gender also contributed significantly. The results suggest that age and gender need to be taken into account in the interpretation of BNP concentrations in critically ill patients.

Gene-expression profiling of peripheral blood mononuclear cells in sepsis.

Objectives:It has been shown that gene-expression profiling of circulating neutrophils could identify signature genes of sepsis. However, whether similar transcriptional changes occurred in peripheral blood mononuclear cells (PBMC) was not known. Using microarray technology, we performed gene-expression profiling of PBMC to identify signature genes that distinguish sepsis from noninfectious causes of systemic inflammatory response syndrome (SIRS), between Gram-positive and Gram-negative sepsis. Design:A cross-sectional, observational study. Setting:A 20-bed general intensive care unit of a tertiary referral hospital. Patients:Seventy critically ill patients (46 sepsis and 24 SIRS). Interventions:Intravenous blood was collected for leukocyte separation and RNA extraction. Gene-expression profiling was performed on PBMC using Affymetrix GeneChip microarrays with 54,675 transcripts. Data were divided into a training set (n = 35) and a validation set (n = 35). A molecular signature was developed in the training set using support vector machine and was then validated in the validation set. Measurements and Main Results:We identified a molecular signature of 138 genes that could differentiate between sepsis and SIRS patients with 91% and 80% accuracy in the training and validation sets, respectively. There were no signature genes that could differentiate between Gram-positive and Gram-negative sepsis. The expression of genes involved in inflammatory response and immune function was significantly reduced in septic patients when compared with those with SIRS. Genes involved in apoptosis, on the other hand, were more highly expressed in septic patients. Conclusion:There was evidence of sepsis-related immunosuppression and reduced inflammatory response in mononuclear cells on a transcriptome level. These characteristic transcriptional changes can be used to aid the diagnosis of sepsis.

Genome-wide transcription profiling of human sepsis: a systematic review

IntroductionSepsis is thought to be an abnormal inflammatory response to infection. However, most clinical trials of drugs that modulate the inflammatory response of sepsis have been unsuccessful. Emerging genomic evidence shows that the host response in sepsis does not conform to a simple hyper-inflammatory/hypo-inflammatory model. We, therefore, synthesized current genomic studies that examined the host response of circulating leukocytes to human sepsis.MethodsElectronic searches were performed in Medline and Embase (1987 to October 2010), supplemented by additional searches in multiple microarray data repositories. We included studies that (1) used microarray, (2) were performed in humans and (3) investigated the host response mediated by circulating leukocytes.ResultsWe identified 12 cohorts consisting of 784 individuals providing genome-wide expression data in early and late sepsis. Sepsis elicited an immediate activation of pathogen recognition receptors, accompanied by an increase in the activities of signal transduction cascades. These changes were consistent across most cohorts. However, changes in inflammation related genes were highly variable. Established inflammatory markers, such as tumour necrosis factor-α (TNF-α), interleukin (IL)-1 or interleukin-10, did not show any consistent pattern in their gene-expression across cohorts. The finding remains the same even after the cohorts were stratified by timing (early vs. late sepsis), patient groups (paediatric vs. adult patients) or settings (clinical sepsis vs. endotoxemia model). Neither a distinctive pro/anti-inflammatory phase nor a clear transition from a pro-inflammatory to anti-inflammatory phase could be observed during sepsis.ConclusionsSepsis related inflammatory changes are highly variable on a transcriptional level. We did not find strong genomic evidence that supports the classic two phase model of sepsis.

Prognostic values of B-type natriuretic peptide in severe sepsis and septic shock.

Objective:To investigate the changes in B-type natriuretic peptide concentrations in patients with severe sepsis and septic shock and to investigate the value of B-type natriuretic peptide in predicting intensive care unit outcomes. Design:Prospective observational study. Setting:General intensive care unit. Patients:Forty patients with severe sepsis or septic shock. Interventions:None. Measurements and Main Results:B-type natriuretic peptide measurements and echocardiography were carried out daily for 10 consecutive days. In-hospital mortality and length of stay were recorded. The admission B-type natriuretic peptide concentrations were generally increased (747 ± 860 pg/mL). B-type natriuretic peptide levels were elevated in patients with normal left ventricular systolic function (568 ± 811 pg/mL), with sepsis-related reversible cardiac dysfunction (630 ± 726 pg/mL), and with chronic cardiac dysfunction (1311 ± 1097 pg/mL). There were no significance changes in B-type natriuretic peptide levels over the 10-day period. The daily B-type natriuretic peptide concentrations for the first 3 days neither predicted in-hospital mortality nor correlated with length of intensive care unit or hospital stay. Conclusion:B-type natriuretic peptide concentrations were increased in patients with severe sepsis or septic shock regardless of the presence or absence of cardiac dysfunction. Neither the B-type natriuretic peptide levels for the first 3 days nor the daily changes in B-type natriuretic peptide provided prognostic value for in-hospital mortality and length of stay in this mixed group of patients, which included patients with chronic cardiac dysfunction.

Gene-expression profiling of gram-positive and gram-negative sepsis in critically ill patients.

Objective:It is unclear whether the host response of Gram-positive sepsis differs from Gram-negative sepsis at a transcriptome level. Using microarray technology, we compared the gene-expression profiles of Gram-positive sepsis and Gram-negative sepsis in critically ill patients. Design:A prospective cross-sectional study. Setting:A 20-bed general intensive care unit of a tertiary referral hospital. Patients:Seventy-two patients admitted to the intensive care unit. Interventions:Intravenous blood was collected for leukocyte separation and RNA extraction. Microarray experiments were then performed examining the expression level of 18,664 genes in each sample. Measurements and Main Results:There was no difference in the expression profile between Gram-positive and Gram-negative sepsis. The finding remained unchanged even when genes with lower expression level were included or after statistical stringency was lowered. There were, however, 94 genes differentially expressed between sepsis and control patients. These genes included those involved in immune regulation, inflammation, and mitochondrial function. Hierarchical cluster analysis confirmed that the difference in gene expression profile existed between sepsis and control patients but not between Gram-positive and Gram-negative patients. Conclusions:Gram-positive sepsis and Gram-negative sepsis share a common host response at a transcriptome level. These findings support the hypothesis that the septic response is nonspecific and is designed to provide a more general response that can be elicited by a wide range of different microorganisms.

Is early ventricular dysfunction or dilatation associated with lower mortality rate in adult severe sepsis and septic shock? A meta-analysis

IntroductionReversible myocardial depression occurs early in severe sepsis and septic shock. The question of whether or not early ventricular depression or dilatation is associated with lower mortality in these patients remains controversial. Most studies on this topic were small in size and hence lacked statistical power to answer the question. This meta-analysis attempted to answer the question by increasing the sample size via pooling relevant studies together.MethodsPubMed, Embase (and Medline) databases and conference abstracts were searched to July 2012 for primary studies using well-defined criteria. Two authors independently screened and selected studies. Eligible studies were appraised using defined criteria. Additional information was sought the corresponding authors if necessary. Study results were pooled using random effects models. Standardized mean differences (SMD) between survivor and non-survivor groups were used as the main effect measures.ResultsA total of 62 citations were found. Fourteen studies were included in the analysis. The most apparent differences between the studies were sample sizes and exclusion criteria. All studies, except four pre-1992 studies, adopted the Consensus definition of sepsis. Altogether, there were >700 patients available for analysis of the left ventricle and >400 for the right ventricle. There were no significant differences in left ventricular ejection fractions, right ventricular ejection fractions, and right ventricular dimensions between the survivor and non-survivor groups. When indexed against body surface area or body height, the survivors and non-survivors had similar left ventricular dimensions. However, the survivors had larger non-indexed left ventricular dimensions.ConclusionThis meta-analysis failed to find any evidence to support the view that the survivors from severe sepsis or septic shock had lower ejection fractions. However, non-indexed left ventricular dimensions were mildly increased in the survivor group but the indexed dimensions were similar between the groups. Both survivors and non-survivors had similar right ventricular dimensions.

A distinct influenza infection signature in the blood transcriptome of patients with severe community-acquired pneumonia

IntroductionDiagnosis of severe influenza pneumonia remains challenging because of a lack of correlation between the presence of influenza virus and clinical status. We conducted gene-expression profiling in the whole blood of critically ill patients to identify a gene signature that would allow clinicians to distinguish influenza infection from other causes of severe respiratory failure, such as bacterial pneumonia, and noninfective systemic inflammatory response syndrome.MethodsWhole-blood samples were collected from critically ill individuals and assayed on Illumina HT-12 gene-expression beadarrays. Differentially expressed genes were determined by linear mixed-model analysis and overrepresented biological pathways determined by using GeneGo MetaCore.ResultsThe gene-expression profile of H1N1 influenza A pneumonia was distinctly different from those of bacterial pneumonia and systemic inflammatory response syndrome. The influenza gene-expression profile is characterized by upregulation of genes from cell-cycle regulation, apoptosis, and DNA-damage-response pathways. In contrast, no distinctive gene-expression signature was found in patients with bacterial pneumonia or systemic inflammatory response syndrome. The gene-expression profile of influenza infection persisted through 5 days of follow-up. Furthermore, in patients with primary H1N1 influenza A infection in whom bacterial co-infection subsequently developed, the influenza gene-expression signature remained unaltered, despite the presence of a superimposed bacterial infection.ConclusionsThe whole-blood expression-profiling data indicate that the host response to influenza pneumonia is distinctly different from that caused by bacterial pathogens. This information may speed the identification of the cause of infection in patients presenting with severe respiratory failure, allowing appropriate patient care to be undertaken more rapidly.

Aberrant cell cycle and apoptotic changes characterise severe influenza A infection--a meta-analysis of genomic signatures in circulating leukocytes.

Influenza A infection is a global disease that has been responsible for four pandemics over the last one hundred years. However, it remains poorly understood as to why some infected individuals succumb to life threatening complications whilst others recover and are relatively unaffected. Using gene-expression analysis of circulating leukocytes, here we show that the progression towards severe influenza A infection is characterised by an abnormal transcriptional reprogramming of cell cycle and apoptosis pathways. In severely infected humans, leukocyte gene-expression profiles display opposing cell cycle activities; an increased aberrant DNA replication in the G1/S phase yet delayed progression in the G2/M phase. In mild infection, cell cycle perturbations are fewer and are integrated with an efficient apoptotic program. Importantly, the loss of integration between cell cycle perturbations and apoptosis marks the transition from a mild viral illness to a severe, life threatening infection. Our findings suggest that circulating immune cells may play a significant role in the evolution of the host response. Further study may reveal alternative host response factors previously unrecognized in the current disease model of influenza.

Identifying key regulatory genes in the whole blood of septic patients to monitor underlying immune dysfunctions

ABSTRACT There is currently no reliable tool available to measure immune dysfunction in septic patients in the clinical setting. This proof-of-concept study assesses the potential of gene expression profiling of whole blood as a tool to monitor immune dysfunction in critically ill septic patients. Whole-blood samples were collected daily for up to 5 days from patients admitted to the intensive care unit with sepsis. RNA isolated from whole-blood samples was assayed on Illumina HT-12 gene expression microarrays consisting of 48,804 probes. Microarray analysis identified 3,677 genes as differentially expressed across 5 days between septic patients and healthy controls. Of the 3,677 genes, biological pathway analysis identified 86 genes significantly downregulated in the sepsis patients were present in pathways relating to immune response. These 86 genes correspond to known immune pathways implicated in sepsis, including lymphocyte depletion, reduced T-lymphocyte activation, and deficient antigen presentation. Furthermore, expression levels of these genes correlated with clinical severity, with a significantly greater degree of downregulation found in nonsurvivors compared with survivors. The results show that whole-blood gene expression analysis can capture systemic immune dysfunctions in septic patients. Our study provides an experimental basis to support further study on the use of a gene expression–based assay, to assess immunosuppression, and to guide immunotherapy in future clinical trials.

DURATION OF THE BENEFICIAL EFFECTS OF LEVOSIMENDAN IN DECOMPENSATED HEART FAILURE AS MEASURED BY ECHOCARDIOGRAPHIC INDICES AND B-TYPE NATRIURETIC PEPTIDE

Levosimendan is effective in the treatment of decompensated heart failure. The beneficial effects of a single dose of levosimendan last much longer than those of other inotropes. However, the exact duration of the beneficial effects is unknown. We prospectively determined the duration of the cardiac effects, as measured by echocardiography, of levosimendan (LS) following a 24-hour infusion regimen in patients with decompensated heart failure (DHF). The effects of LS on plasma B-type natriuretic peptide (BNP) were also examined. Twenty patients with DHF displaying (1) deteriorating symptoms despite optimal oral therapy, (2) left ventricular ejection fractions (LVEF) < 35%, and (3) cardiac indices of < 2.5 L/m2/min received 24 hours of LS infusion. Echocardiography and BNP measurements were performed pre- and postinfusion and were reassessed on days 7, 30, and 90. Left ventricular systolic function indices (cardiac output and LVEF), LV filling pressure indices, and right ventricular systolic function indices all improved following LS treatment. Most of these improvements were sustained for at least 7 days (P < 0.05) and returned to baseline by day 30 postinfusion and remained so on day 90. Plasma BNP also displayed the same pattern of transient improvements. In conclusion, LS transiently improved the cardiac function, and the effects lasted for at least 7 days after discontinuation of infusion. Most effects, except LVEF, were not significantly different from baseline on day 30.