alpha-atrial natriuretic peptide, cyclic guanosine monophosphate, and endothelin in plasma as markers of myocardial depression in human septic shock

Natriuretic peptide receptor-C mediates the inhibitory effect of atrial natriuretic peptide on neutrophil recruitment to the lung during acute lung injury

Atrial natriuretic peptide (ANP) protects against acute lung injury (ALI), but the receptor that mediates this effect is not known. Transgenic mice with 0 (knockout), 1 (heterozygote), or 2 (wild-type) functional copies of Npr3, the gene that encodes for natriuretic peptide receptor-C (NPR-C), were treated with intravenous infusion of ANP or saline vehicle before oropharyngeal aspiration of Pseudomonas aeruginosa (PA103) or saline vehicle. Lung injury was assessed 4 h following aspiration by measurement of lung wet/dry (W/D) weight, whole lung leukocyte and cytokine levels, and protein, leukocyte, and cytokine concentration in bronchoalveolar lavage fluid (BALF). PA103 induced acute lung injury as evidenced by increases in lung W/D ratio and protein concentration in BALF. The severity of PA103-induced lung injury did not differ between NPR-C genotypes. Treatment with intravenous ANP infusion reduced PA103-induced increases in lung W/D and BALF protein concentration in all three NPRC genotypes. PA103 increased the percentage of leukocytes that were neutrophils and cytokine levels in whole lung and BALF in NPR-C wild-type and knockout mice. This effect was blunted by ANP in wild-type mice but not in the NPR-C knockout mice. NPR-C does not mediate the protective effect of ANP on endothelial cell permeability in settings of PA103-induced injury but may mediate the effect of ANP on inhibition of the recruitment of neutrophils to the lung and thereby attenuate the release of inflammatory cytokines.

Septic cardiomyopathy: Diagnosis and management

There is an extensive body of literature focused on sepsis-induced myocardial dysfunction, but results are conflicting and no objective definition of septic cardiomyopathy (SCM) has been established. SCM may be defined as a sepsis-associated acute syndrome of non-ischemic cardiac dysfunction with systolic and/or diastolic left ventricular (LV) dysfunction and/or right ventricular dysfunction. Physicians should consider this diagnosis in patients with sepsis-associated organ dysfunction, and particularly in cases of septic shock that require vasopressors. Echocardiography is currently the gold standard for diagnosis of SCM. Left ventricular ejection fraction is the most common parameter used to describe LV function in the literature, but its dependence on loading conditions, particularly afterload, limits its use as a measure of intrinsic myocardial contractility. Therefore, repeated echocardiography evaluation is mandatory. Evaluation of global longitudinal strain (GLS) may be more sensitive and specific for SCM than LV ejection fraction (LVEF). Standard management includes etiological treatment, adapted fluid resuscitation, use of vasopressors, and monitoring. Use of inotropes remains uncertain, and heart rate control could be an option in some patients.

B-type natriuretic peptide is upregulated by c-Jun N-terminal kinase and contributes to septic hypotension

B-type natriuretic peptide (BNP) is secreted by ventricular cardiomyocytes in response to various types of cardiac stress and has been used as a heart failure marker. In septic patients, increased BNP suggests poor prognosis; however, no causal link has been established. Among various effects, BNP decreases systemic vascular resistance and increases natriuresis that leads to lower blood pressure. We previously observed that JNK inhibition corrects cardiac dysfunction and suppresses cardiac BNP mRNA in endotoxemia. In this study, we investigated the transcriptional mechanism that regulates BNP expression and the involvement of plasma BNP in causing septic hypotension. Our in vitro and in vivo findings confirmed that activation of JNK signaling increases BNP expression in sepsis via direct binding of c-Jun in activating protein–1 (AP-1) regulatory elements of the Nppb promoter. Accordingly, genetic ablation of BNP, as well as treatment with a potentially novel neutralizing anti-BNP monoclonal antibody (19B3) or suppression of its expression via administration of JNK inhibitor SP600125 improved cardiac output, stabilized blood pressure, and improved survival in mice with polymicrobial sepsis. Therefore, inhibition of JNK signaling or BNP in sepsis appears to stabilize blood pressure and improve survival.

Effects of protease activated receptor (PAR)2 blocking peptide on endothelin-1 levels in kidney tissues in endotoxemic rat mode

AIMS

Septic shock, the severe form of sepsis, is associated with development of progressive damage in multiple organs. Kidney can be injured and its functions altered by activation of coagulation, vasoactive-peptide and inflammatory processes in sepsis. Endothelin (ET)-1, a potent vasoconstrictor, is implicated in the pathogenesis of sepsis and its complications. Protease-activated receptors (PARs) are shown to play an important role in the interplay between inflammation and coagulation. We examined the time-dependent alterations of ET-1 and inflammatory cytokine, such as tumor necrosis factor (TNF)-α in kidney tissue in lipopolysaccharide (LPS)-induced septic rat model and the effects of PAR2 blocking peptide on the LPS-induced elevations of renal ET-1 and TNF-α levels.

MAIN METHODS

Male Wistar rats at 8 weeks of age were administered with either saline solution or LPS at different time points (1, 3, 6 and 10h). Additionally, we treated LPS-administered rats with PAR2 blocking peptide for 3h to assess whether blockade of PAR2 has a regulatory role on the ET-1 level in septic kidney.

KEY FINDINGS

An increase in ET-1 peptide level was observed in kidney tissue after LPS administration time-dependently. Levels of renal TNF-α peaked (around 12-fold) at 1h of sepsis. Interestingly, PAR2 blocking peptide normalized the LPS-induced elevations of renal ET-1 and TNF-α levels.

SIGNIFICANCE

The present study reveals a distinct chronological expression of ET-1 and TNF-α in LPS-administered renal tissues and that blockade of PAR2 may play a crucial role in treating renal injury, via normalization of inflammation, coagulation and vaso-active peptide.

A review of methylene blue treatment for cardiovascular collapse

BACKGROUND

Historically, methylene blue (MB) has been used for multiple purposes, including as an antidote for toxin-induced and hereditary methemoglobinemia, ifosfamide-induced encephalopathy, and ackee fruit and cyanide poisoning; as an aniline dye derivative, antimalarial agent, and antidepressant.

DISCUSSION

Most recently, the use of MB has been advocated as a potential adjunct in the treatment of shock states. Our article reviews the role of MB in septic shock, anaphylactic shock, and toxin-induced shock. MB is proposed to increase blood pressure in these shock states by interfering with guanylate cyclase activity, and preventing cyclic guanosine monophosphate production and vasodilatation.

SUMMARY

MB may be an adjunct in the treatment of septic shock, anaphylactic shock, and toxin-induced shock.

Biomarkers in community-acquired pneumonia: a state-of-the-art review

Community-acquired pneumonia (CAP) exhibits mortality rates, between 20% and 50% in severe cases. Biomarkers are useful tools for searching for antibiotic therapy modifications and for CAP diagnosis, prognosis and follow-up treatment. This non-systematic state-of-the-art review presents the biological and clinical features of biomarkers in CAP patients, including procalcitonin, C-reactive protein, copeptin, pro-ANP (atrial natriuretic peptide), adrenomedullin, cortisol and D-dimers.

Vasopressors and inotropes in the treatment of human septic shock: effect on innate immunity?

Catecholamines have been suggested to modulate innate immune responses in experimental settings. The significance hereof in the treatment of human septic shock is unknown. We therefore sought if and how vasopressor/inotropic doses relate to pro-inflammatory mediators during treatment of septic shock. We prospectively studied 20 consecutive septic shock patients. For 3 days after admission, hemodynamic variables, lactate and plasma levels of interleukins (IL)-6 and 8, tumor necrosis factor (TNF)-α, and elastase-α₁-antitrypsin were measured six hourly. Doses of vasoactive drugs were recorded. Of the 20 patients, nine died in the intensive care unit. Dobutamine doses were positively associated and related to TNF-α plasma levels, independently of disease severity, hemodynamics, and outcome, in multivariable models. Dopamine doses were positively associated with IL-6, and norepinephrine was inversely associated with IL-8 and TNF-α levels. Our observations suggest that catecholamines used in the treatment of human septic shock differ in their potential modulation of the innate immune response to sepsis in vivo. Dobutamine treatment may contribute to circulating TNF-α and dopamine to IL-6, independently of activated neutrophils. Conversely, norepinephrine may lack pro-inflammatory actions.

Comparing the accuracy of predictors of mortality in ventilator-associated pneumonia

OBJECTIVE

Levels of procalcitonin, midregional pro-atrial natriuretic peptide (MR-proANP), C-terminal provasopressin (copeptin), and C-reactive protein (CRP), as well as Sequential Organ Failure Assessment (SOFA) scores, are associated with severity and described as predictors of outcome in ventilator-associated pneumonia (VAP). This study sought to compare the predictive value of these biomarkers for mortality in VAP.

METHODS

An observational study of 71 patients with VAP. Levels of procalcitonin, MR-proANP, copeptin, and CRP, together with SOFA scores, were determined at VAP onset, designated day 0 (D0), and on day 4 of treatment (D4). Patients received empirical antimicrobial therapy, with modifications based on culture results. Patients who died before D28 were classified as nonsurvivors.

RESULTS

Of the 71 patients evaluated, 45 were classified as survivors. Of the 45 survivors, 35 (77.8%) received appropriate antimicrobial therapy, compared with 18 (69.2%) of the 26 nonsurvivors (p = 0.57). On D0 and D4, the levels of all biomarkers (except CRP), as well as SOFA scores, were lower in eventual survivors than in eventual nonsurvivors. For D0 and D4, the area under the ROC curve was largest for procalcitonin. On D0, MR-proANP had the highest positive likelihood ratio (2.71) and positive predictive value (0.60), but procalcitonin had the highest negative predictive value (0.87). On D4, procalcitonin had the highest positive likelihood ratio (3.46), the highest positive predictive value (0.66), and the highest negative predictive value (0.93).

CONCLUSIONS

The biomarkers procalcitonin, MR-proANP, and copeptin can predict mortality in VAP, as can the SOFA score. Procalcitonin alone has the greatest predictive power for such mortality.

Uncoordinated regulation of atrial natriuretic factor and brain natriuretic peptide in lipopolysaccharide-treated rats

We investigated the expression and secretion of the natriuretic peptides (NPs) ANF and BNP in lipopolysaccharide (LPS)-induced sepsis and its association with cytokines and other biologically active substances. LPS treatment increased plasma levels of ANF and BNP. The latter increase was larger than the increase in plasma ANF. LPS also increased cardiac content and gene expression of BNP but not of ANF. LPS treatment significantly increased gene expression cytokines, chemokines and proteases, which significantly correlated with BNP gene expression. SB203580, a p38 MAP kinase inhibitor, inhibited the elevation of BNP in plasma. The present work suggests that during inflammation, BNP gene expression and secretion is uniquely related to changes in gene expression in the absence of hemodynamic changes and hence differentiates ANF and BNP as biomarkers of cardiac disease.

Cardiac biomarkers in the critically ill

Cardiac biomarkers have well-established roles in acute coronary syndrome and congestive heart failure. In many instances, the detection of cardiac biomarkers may aid in the diagnosis and risk assessment of critically ill patients. Despite increasing interest in the use of cardiac biomarkers in noncardiac critical illness, no clear consensus exists on how and in which settings markers should be measured. This article briefly describes what constitutes an ideal biomarker and focuses on those that have been most well studied in critical illness, specifically troponin, the natriuretic peptides, and heart-type fatty acid-binding protein.

Multimarker panels in sepsis

Biomarkers differentiate between 2 or more biologic states. The complexity of diseases like sepsis makes it unlikely that any single marker will allow for precise disease specification. Combining several biomarkers into a single classification rule should help to improve their accuracy and, therefore, their usefulness. This article reviews several studies using multimarker panels, and highlights the potential of more sophisticated diagnostic and prognostic techniques in future multimarker panels. More complex algorithms should accelerate the adoption of multimarker panels into the routine management of patients with sepsis, provided that clinicians understand the multimarker approach.

Resistance to endotoxic shock in mice lacking natriuretic peptide receptor-A

Background and purpose:

Excessive production of nitric oxide (NO) by inducible NO synthase (iNOS) is thought to underlie the vascular dysfunction, systemic hypotension and organ failure that characterize endotoxic shock. Plasma levels of atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP) and C-type natriuretic peptide (CNP) are raised in animal models and humans with endotoxic shock and correlate with the associated cardiovascular dysfunction. Since both NO and natriuretic peptides play important roles in cardiovascular homeostasis via activation of guanylate cyclase-linked receptors, we used mice lacking natriuretic peptide receptor (NPR)-A (NPR1) to establish if natriuretic peptides contribute to the cardiovascular dysfunction present in endotoxic shock.

Experimental approach:

Wild-type (WT) and NPR-A knockout (KO) mice were exposed to lipopolysaccharide (LPS) and vascular dysfunction (in vitro and in vivo), production of pro-inflammatory cytokines, and iNOS expression and activity were evaluated.

Key results:

LPS-treated WT animals exhibited a marked fall in mean arterial blood pressure (MABP) whereas NPR-A KO mice maintained MABP throughout. LPS administration caused a greater suppression of vascular responses to the thromboxane-mimetic U46619, ANP, acetylcholine and the NO-donor spermine-NONOate in WT versus NPR-A KO mice. This differential effect on vascular function was paralleled by reduced pro-inflammatory cytokine production, iNOS expression and activity (plasma [NO_x] and cyclic GMP).

Conclusions and implications:

These observations suggest that NPR-A activation by natriuretic peptides facilitates iNOS expression and contributes to the vascular dysfunction characteristic of endotoxic shock. Pharmacological interventions that target the natriuretic peptide system may represent a novel approach to treat this life-threatening condition.

The hemodynamics of human septic shock relate to circulating innate immunity factors

The role of innate immunity, e.g., complement activation and cytokine release in the hemodynamic alterations in the course of human septic shock is largely unknown. We prospectively studied 14 consecutive septic shock patients with a pulmonary artery catheter in place. For 3 days after admission, hemodynamic variables and plasma levels of C3a, a product of complement activation, and interleukin (IL)-6 and tumor necrosis factor alpha (TNF-α) were measured 6-hourly. Doses of vasoactive drugs were recorded. Of the 14 patients, 8 died in the ICU. Patients had a hyperdynamic circulation with tachycardia, mild hypotension, increased cardiac index, peripheral vasodilation and myocardial depression. C3a, IL-6 and TNF-α plasma levels were supranormal in 123 of 138 (89%), 132 of 138 (96%) and 83 of 111 (75%) measurements, respectively. Independently of blood culture results, treatment with vasoactive drugs and outcome, mean arterial blood pressure and systemic vascular resistance index were lower when IL-6 levels were higher and left ventricular function was less depressed when C3a levels were higher in the course of septic shock. The TNF-α levels did not invariably relate to peripheral vascular and myocardial function parameters. Our serial observations suggest that, in human septic shock, peripheral vasodilation is most strongly and independently, of all inflammatory factors, associated with IL-6 release, whereas complement activation partly offsets the myocardial depression of the syndrome. Innate immunity factors may thus differ in their contribution to the course of hemodynamic abnormalities of septic shock.

Sepsis biomarkers: a review

INTRODUCTION

Biomarkers can be useful for identifying or ruling out sepsis, identifying patients who may benefit from specific therapies or assessing the response to therapy.

METHODS

We used an electronic search of the PubMed database using the key words "sepsis" and "biomarker" to identify clinical and experimental studies which evaluated a biomarker in sepsis.

RESULTS

The search retrieved 3370 references covering 178 different biomarkers.

CONCLUSIONS

Many biomarkers have been evaluated for use in sepsis. Most of the biomarkers had been tested clinically, primarily as prognostic markers in sepsis; relatively few have been used for diagnosis. None has sufficient specificity or sensitivity to be routinely employed in clinical practice. PCT and CRP have been most widely used, but even these have limited ability to distinguish sepsis from other inflammatory conditions or to predict outcome.

Biomarkers: diagnosis and risk assessment in sepsis

Prompt diagnosis, intervention, and risk assessment are critical in caring for septic patient but remain difficult with currently available methods. Biomarkers may become useful adjuncts to clinicians and ultimately serve as targets for future therapeutic trials in sepsis. The most relevant markers are reviewed in this article, including interleukin-6, C-reactive protein, procalcitonin, triggering receptor expressed on myeloid cells-1, and biomarker panels.

Elevation of brain natriuretic peptide levels in children with septic shock

OBJECTIVES

1) To compare brain natriuretic peptide levels in pediatric patients with septic shock with both children admitted to the pediatric intensive care unit without infection and with healthy subjects; and 2) to evaluate the correlation between brain natriuretic peptide with severity of illness and with myocardial dysfunction in children with septic shock.

DESIGN

: Prospective, observational study.

SETTING

Children's Hospital pediatric intensive care unit.

PATIENTS

Children from age 2 wks to 18 yrs. Thirteen children with septic shock requiring inotropic support, 12 healthy controls, and five critically ill patients without infection or heart disease were evaluated.

INTERVENTIONS

For patients with septic shock, brain natriuretic peptide was measured within 6 hrs of admission and throughout the pediatric intensive care unit course. Echocardiograms were performed within 12 hrs of admission and then repeated if the patient continued to require inotropic support. For controls, one measurement was performed.

MEASUREMENTS AND MAIN RESULTS

Children with septic shock had an elevated (p < 0.0001) brain natriuretic peptide on admission (median 115 pg/mL [range 26-2960]) when compared with healthy (9 pg/mL [5-30]) and pediatric intensive care unit controls (10 pg/mL [5-30]). In patients with septic shock, brain natriuretic peptide at 12 hrs correlated directly with Pediatric Risk of Mortality III score (rs = .80, p = 0.002) and inversely with fractional shortening (rs = -.66, p = 0.014). In children with cold shock, brain natriuretic peptide at 12 hrs (718 pg/mL) [63-1530] was higher (p = 0.007) than in those with warm shock (208 pg/mL [20-366]). There was no pattern (p > 0.05) observed for brain natriuretic peptide over time.

CONCLUSIONS

Brain natriuretic peptide measured early after admission is increased in children with septic shock, especially in those with cold shock. In addition, the level at 12 hrs correlates with both severity of illness and myocardial dysfunction. Brain natriuretic peptide may be useful in assessing myocardial dysfunction from septic shock, particularly in identifying children with cold shock. Further studies are warranted to determine whether this measurement will be helpful in guiding therapy in pediatric septic shock.

Combined milrinone and enteral metoprolol therapy in patients with septic myocardial depression

INTRODUCTION

The multifactorial etiology of septic cardiomyopathy is not fully elucidated. Recently, high catecholamine levels have been suggested to contribute to impaired myocardial function.

METHODS

This retrospective analysis summarizes our preliminary clinical experience with the combined use of milrinone and enteral metoprolol therapy in 40 patients with septic shock and cardiac depression. Patients with other causes of shock or cardiac failure, patients with beta-blocker therapy initiated more than 48 hours after shock onset, and patients with pre-existent decompensated congestive heart failure were excluded. In all study patients, beta blockers were initiated only after stabilization of cardiovascular function (17.7 +/- 15.5 hours after shock onset or intensive care unit admission) in order to decrease the heart rate to less than 95 beats per minute (bpm). Hemodynamic data and laboratory parameters were extracted from medical charts and documented before and 6, 12, 24, 48, 72, and 96 hours after the first metoprolol dosage. Adverse cardiovascular events were documented. Descriptive statistical methods and a linear mixed-effects model were used for statistical analysis.

RESULTS

Heart rate control (65 to 95 bpm) was achieved in 97.5% of patients (n = 39) within 12.2 +/- 12.4 hours. Heart rate, central venous pressure, and norepinephrine, arginine vasopressin, and milrinone dosages decreased (all P < 0.001). Cardiac index and cardiac power index remained unchanged whereas stroke volume index increased (P = 0.002). In two patients (5%), metoprolol was discontinued because of asymptomatic bradycardia. Norepinephrine and milrinone dosages were increased in nine (22.5%) and six (15%) patients, respectively. pH increased (P < 0.001) whereas arterial lactate (P < 0.001), serum C-reactive protein (P = 0.001), and creatinine (P = 0.02) levels decreased during the observation period. Twenty-eight-day mortality was 33%.

CONCLUSION

Low doses of enteral metoprolol in combination with phosphodiesterase inhibitors are feasible in patients with septic shock and cardiac depression but no overt heart failure. Future prospective controlled trials on the use of beta blockers for septic cardiomyopathy and their influence on proinflammatory cytokines are warranted.

Brain natriuretic peptide increases in septic patients without severe sepsis or shock

BACKGROUND

B-type natriuretic peptide (BNP) production increases in critically ill septic patients. We assessed the hypothesis that BNP is elevated in patients with community-acquired infections without severe sepsis or septic shock.

METHODS

We studied 54 patients [20 males, median age 39 (interquartile range 23, 71)] without heart disease, persistent arrhythmias, or renal failure. BNP was measured in all patients at hospital admission and at pre-discharge and in a control group of 52 individuals. Myoglobin levels were also measured in septic patients.

RESULTS

The infection was microbial in 40 patients, viral in 11, and of undefined etiology in 3. A systemic inflammatory response was evident in 38 patients on the initial evaluation. BNP on admission was higher in patients than in controls [25 (10, 82) pg/ml vs. 13 (5, 30) pg/ml, p=0.01] and it decreased to 16 (5, 47) pg/ml pre-discharge (p=0.0002). Multiple logistic regression identified the presence of microbial infection as the only independent predictor of an elevated BNP value on admission [adjusted odds ratio 9.8 (1.02-93.8), p=0.04]. In patients with microbial infection, location of infection in the lower respiratory tract and the presence of diabetes mellitus were independent predictors of the magnitude of BNP increase. Myoglobin was also increased on hospital admission 80 (37, 231) ng/ml and decreased pre-discharge to 59 (38, 94) ng/ml, p=0.004. Myoglobin level changes from admission to discharge were more prominent with increasing age and in females.

CONCLUSION

BNP levels are elevated in the acute phase of community-acquired microbial infections without severe sepsis or septic shock.

Circulating levels of pro-atrial natriuretic peptide in lower respiratory tract infections

OBJECTIVE

To analyse the mid region of plasma N-terminal pro-atrial natriuretic peptide (MR-proANP) levels in patients with lower respiratory tract infections to evaluate its prognostic use for the severity of disease and outcome.

DESIGN

Prospective observational study. Setting. Emergency department of a university hospital.

SUBJECTS

A total of 545 consecutive patients with lower respiratory tract infections and 50 healthy controls. Interventions. MR-proANP was measured in serum from all patients using a new sandwich immunoassay.

RESULTS

MR-proANP levels (median [IQR], in pmol L(-1)) were significantly higher in patients with lower respiratory tract infections when compared with controls (138.0 [74.1-279.0] vs. 72.7 [62.5-89.5], P < 0.001), with highest levels in patients with community-acquired pneumonia (CAP). MR-proANP, but not C-reactive protein (CRP) levels, gradually increased with increasing severity of CAP, classified according to the pneumonia severity index (PSI) score (P < 0.001). On admission, MR-proANP levels were significantly higher in nonsurvivors when compared with survivors (293.0 [154.0-633.0] vs. 129.0 [71.4-255.0], P < 0.001). In a receiver operating characteristic (ROC) analysis for the prediction of survival of patients with CAP the area under the ROC curve (AUC) for MR-proANP was 0.69, similar when compared with the PSI (AUC 0.74, P = 0.31), and better when compared with other biomarkers, i.e. procalcitonin (AUC 0.57, P = 0.08), CRP (AUC 0.52, P = 0.02), and leucocyte count (AUC 0.56, P = 0.07).

CONCLUSIONS

MR-proANP levels are increased in lower respiratory tract infections, especially in CAP. Together with other clinical, radiographic and laboratory findings, MR-proANP levels might be helpful for the risk stratification in CAP.

Markers for sepsis diagnosis: what is useful?

Timely diagnosis of the different severities of septic inflammation is potentially lifesaving because therapies that have been shown to lower mortality should be initiated early. Sepsis and severe sepsis are accompanied by clinical and laboratory signs of systemic inflammation but patients with inflammation caused by noninfectious causes may present with similar signs and symptoms. It is important to identify markers for an early diagnosis of sepsis and organ dysfunction. This article presents currently interesting sepsis biomarkers. Other novel markers and their potential role are discussed.

Prognostic value of increased plasma levels of brain natriuretic peptide in patients with septic shock

Our objective was to investigate the plasma levels of brain and atrial natriuretic peptides (BNP and ANP, respectively) in patients with septic shock/severe sepsis and to study the association of BNP and ANP levels with hemodynamic parameters, severity of the disease, and prognosis of those patients. This is a prospective case series study of 22 patients with septic shock, 11 patients with severe sepsis, and 20 healthy volunteers at the Department of Emergency and Critical Care Medicine, Nara Medical University Hospital, Japan. Blood collection was performed on admission and on days 1, 2, and 4. Plasma BNP and ANP levels were measured by radioimmunoassay. Right atrial pressure, mean pulmonary arterial pressure, pulmonary arterial wedge pressure, and left ventricular stroke work index were determined using a thermodilution catheter. Acute Physiological and Chronic Health Evaluation II scores were calculated. Plasma levels of BNP and ANP were markedly elevated in patients with septic shock/severe sepsis compared with controls (BNP, 7 +/- 0.3 pg mL; ANP, 13 +/- 1 pg mL). In patients with septic shock, both BNP and ANP peaked on day 2 (BNP, 987 +/- 160 pg mL; ANP, 103 +/- 17 pg mL). Plasma levels of BNP on day 2 in patients with septic shock significantly correlated with right atrial pressure (r = 0.744, P < 0.01), mean pulmonary arterial pressure (r = 0.670, P < 0.01), pulmonary arterial wedge pressure (r = 0.709, P < 0.01), left ventricular stroke work index (r = -0.552, P < 0.05), Acute Physiological and Chronic Health Evaluation II score (r = 0.581, P < 0.01), and poor prognosis (P < 0.05). The optimal cutoff point for predicting mortality in patients with septic shock was a BNP level of 650 pg mL on day 2, in which sensitivity and specificity were 92% and 80%, respectively. Increased plasma levels of BNP may reflect not only the severity of myocardial depression but also the disease severity and could be of prognostic value in patients with septic shock.

Time-dependent expression of renal vaso-regulatory molecules in LPS-induced endotoxemia in rat

To elucidate roles of microvascular factors in the pathogenesis of renal complications during endotoxemia, that is characterized by renal vasoconstriction and systemic hypotension/generalized non-renal vasodilation, we profile the expression pattern and time-course of three key vaso-regulators, namely endothelin (ET)-1, nitric oxide (NO), and angiotensin II (Ang II). We hypothesize that disruption of the overall balance between vasodilatation and vasoconstriction in the kidney, during the early phase of sepsis, contribute to its (kidney) predisposition to acute renal failure. Adult male Wistar rats were rendered endotoxemic at different time points (1, 3, 6 and 10 h) by a single i.p. injection of lipopolysaccharide (LPS) (15 mg/kg) dissolved in saline. Control group was injected vehicle only (saline). Both systolic and diastolic blood pressures significantly decreased at different time points after LPS administration. Surprisingly, renal histopathological evaluation showed no remarkable changes in LPS-induced endotoxemia. However, overall, levels of the vaso-regulators and, where applicable, their respective receptors were upregulated: (1) plasma ET-1 increased 25-fold and peaked, as renal ET-1 mRNA, at 3 h; renal ET-1 protein and its receptors, ET type A (ET(A)) receptor (vasoconstrictive) and ET type B (ET(B)) receptor (vasodilatatory) increased in a time-dependent fashion, (2) Ang II increased by 53% compared to control, peaking at 6 h. However, while levels of Ang II type 1 (AT1) receptor increased over time after LPS injection, those of Ang II type 2 (AT2) receptor were downregulated, (3) data of NO system (NO-NOS), the key vasodilator, were the most intriguing. Whereas levels of renal NO increased time-dependently following LPS administration, with a 2240-fold increase in renal iNOS expression, levels of eNOS, were almost unchanged. In conclusion, the present study overall reveals intriguing and complex dynamics between levels of vasoconstrictors and vasodilators during the early phase of LPS-induced endotoxemia. These shifts in molecular expressions are likely triggered by compensatory mechanisms aimed at counteracting the undesirable and dominant effects of one group of vaso-regulatory moiety over the other.

Sepsis-associated myocardial dysfunction: diagnostic and prognostic impact of cardiac troponins and natriuretic peptides

Myocardial dysfunction, which is characterized by transient biventricular impairment of intrinsic myocardial contractility, is a common complication in patients with sepsis. Left ventricular systolic dysfunction is reflected by a reduced left ventricular stroke work index or, less accurately, by an impaired left ventricular ejection fraction (LVEF). Early recognition of myocardial dysfunction is crucial for the administration of the most appropriate therapy. Cardiac troponins and natriuretic peptides are biomarkers that were previously introduced for diagnosis and risk stratification in patients with acute coronary syndrome and congestive heart failure, respectively. However, their prognostic and diagnostic impact in critically ill patients warrants definition. The elevation of cardiac troponin levels in patients with sepsis, severe sepsis, or septic shock has been shown to indicate left ventricular dysfunction and a poor prognosis. Troponin release in this population occurs in the absence of flow-limiting coronary artery disease, suggesting the presence of mechanisms other than thrombotic coronary artery occlusion, probably a transient loss in membrane integrity with subsequent troponin leakage or microvascular thrombotic injury. In contrast to the rather uniform results of studies dealing with cardiac troponins, the impact of raised B-type natriuretic peptide (BNP) levels in patients with sepsis is less clear. The relationship between BNP and both LVEF and left-sided filling pressures is weak, and data on the prognostic impact of high BNP levels in patients with sepsis are conflicting. Mechanisms other than left ventricular wall stress may contribute to BNP release, including right ventricular overload, catecholamine therapy, renal failure, diseases of the CNS, and cytokine up-regulation. Whereas cardiac troponins may be integrated into the monitoring of myocardial dysfunction in patients with severe sepsis or septic shock to identify those patients requiring early and aggressive supportive therapy, the routine use of BNP and other natriuretic peptides in this setting is discouraged at the moment.

Biomarkers of sepsis: clinically useful?

PURPOSE OF REVIEW

The purpose of this review is to indicate recent developments in biomarkers of sepsis and to evaluate their impact on clinical use. According to the 'surviving sepsis campaign,' diagnosis of sepsis and infection is urgent; early and specific treatment is most effective to reduce complications and to decrease mortality.

RECENT FINDINGS

A variety of biomarkers of sepsis is presently available. The diagnostic spectrum of the various markers, however, is different. Some primarily indicate severity of inflammation (e.g. interleukin-6), others respond to infection, but do not indicate the host response well (endotoxin, lipoprotein binding protein, triggering receptor on myeloid cells). There are new markers with limited clinical experience, for example triggering receptor on myeloid cells or mid-pro atrial natriuretic peptide (Seristra, Brahms AG, Hennigsdorf, Germany). Procalcitonin is a well-established biomarker of sepsis that fulfills several criteria of clinical needs: it responds both to infection and severity of inflammation and thus has an impact on therapy. Recent studies indicate that antibiotic treatment can also be guided by procalcitonin. Further indications, including diagnosis of invasive bacterial infections and diagnosis of sepsis in neonates and children have been reported recently.

SUMMARY

Recent data and cumulative analyses indicate that biomarkers of sepsis improve diagnosis of sepsis. However, only a few markers have impact on therapy and fulfill the clinical requirements. Procalcitonin is a well-established marker, indicating infection, sepsis, and progression to the more severe stages of the disease. Today, this biomarker should be in the diagnostic portfolio of an intensive care unit or emergency ward.

Prognostic value of plasma N-terminal pro-brain natriuretic peptide in patients with severe sepsis

BACKGROUND

Increased plasma levels of atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) have been identified as predictors of cardiac dysfunction and prognosis in congestive heart failure and ischemic heart disease. In severe sepsis patients, however, no information is available yet about the prognostic value of natriuretic peptides. Therefore, the aim of the present study was to determine the role of the N-terminal prohormone forms of ANP (NT-proANP) and BNP (NT-proBNP) in the context of outcome of septic patients. Furthermore, the effect of treatment with recombinant human activated protein C [drotrecogin alfa (activated)] on plasma levels of natriuretic peptides in severe sepsis was evaluated.

METHODS AND RESULTS

Fifty-seven patients with severe sepsis were included. Levels of NT-proANP and NT-proBNP were measured on the second day of sepsis by ELISA. Septic patients with NT-proBNP levels >1400 pmol/L were 3.9 times more likely (relative risk [RR], 3.9; 95% CI, 1.6 to 9.7) to die from sepsis than patients with lower NT-proBNP values (P<0.01). NT-proANP levels, however, were not predictive of survival in our patient population. A highly significant correlation was found between troponin I levels and plasma concentrations of NT-proBNP in septic patients (r=0.68, P<0.0001). In addition, troponin I significantly accounted for the variation in NT-proBNP levels (P<0.0001), suggesting an important role for NT-proBNP in the context of cardiac injury and dysfunction in septic patients. Twenty-three septic patients who received treatment with drotrecogin alfa (activated) presented with significantly lower concentrations of NT-proANP, NT-proBNP, and troponin I compared with patients not receiving drotrecogin alfa (activated).

CONCLUSIONS

NT-proBNP may serve as useful laboratory marker to predict survival in patients presenting with severe sepsis.

Circulating cardiovascular markers and mediators in acute illness: an update

An update is given of the circulating markers and mediators of cardiovascular dysfunction in acute illness. Some of these circulating markers reflect mediator action on the peripheral vasculature, such as endothelium-derived endothelin and nitrite/nitritate, the stable end products of nitric oxide. Other markers mainly reflect actions on the heart, such as the natriuretic peptide family, released from the heart upon dilatation, serving as a marker of congestive heart failure and potentially having negative inotropic effects. Indeed, some factors may be both markers as well as mediators of cardiovascular dysfunction of the acutely ill and bear prognostic significance. Assessing circulating levels may help refine clinical judgment of the cardiovascular derangements encountered at the bedside, together with clinical signs and hemodynamic variables. For instance, assessing natriuretic peptides in patients with pulmonary edema of unclear origin may help to diagnose congestive heart failure and cardiogenic pulmonary edema, when the pulmonary capillary wedge pressure is not measured or inconclusive. Future aligning of hemodynamic abnormalities with patterns of circulating cardiovascular markers/mediators may help to stratify patients for inclusion in studies to assess the causes, response to therapy and prognosis of cardiovascular derangements in the acutely ill.

Changes of tissue endothelin-1 and nitric oxide synthase in a sheep model of large intestinal obstruction

Large intestinal obstruction (LIO) in farm animals can cause a ischaemic necrosis of intestinal tissue, eventually leading to death. The roles of endothelin-1 (ET-1) and nitric oxide (NO) are not well understood in the process of LIO, but evidence suggests that endothelial-derived mediators may participate. In the present study, ET-1 concentration and total nitric oxide synthase (NOS) activity were measured in heart, liver, pancreas, lung and kidney in a model of LIO in sheep. Our data demonstrated that ET-1 concentration and NOS activity were altered, with significant increases of ET-1 in heart, lung and kidney and of NOS activity in pancreas and kidney, but a marked decline of NOS activity in liver (p < 0.05). It is postulated that these alterations in NOS activity and ET-1 concentration may contribute to the progressive loss of organ function, and finally lead to death in LIO in sheep.

Pro-atrial natriuretic peptide is a prognostic marker in sepsis, similar to the APACHE II score: an observational study

Introduction

Additional biomarkers in sepsis are needed to tackle the challenges of determining prognosis and optimizing selection of high-risk patients for application of therapy. In the present study, conducted in a cohort of medical intensive care unit patients, our aim was to compare the prognostic value of mid-regional pro-atrial natriuretic peptide (ANP) levels with those of other biomarkers and physiological scores.

Methods

Blood samples obtained in a prospective observational study conducted in 101 consecutive critically ill patients admitted to the intensive care unit were analyzed. The prognostic value of pro-ANP levels was compared with that of the Acute Physiology and Chronic Health Evaluation (APACHE) II score and with those of various biomarkers (i.e. C-reactive protein, IL-6 and procalcitonin). Mid-regional pro-ANP was detected in EDTA plasma from all patients using a new sandwich immunoassay.

Results

On admission, 53 patients had sepsis, severe sepsis, or septic shock, and 68 had systemic inflammatory response syndrome. The median pro-ANP value in the survivors was 194 pmol/l (range 20–2000 pmol/l), which was significantly lower than in the nonsurvivors (median 853.0 pmol/l, range 100–2000 pmol/l; P < 0.001). On the day of admission, pro-ANP levels, but not levels of other biomarkers, were significantly higher in surviving than in nonsurviving sepsis patients (P = 0.001). In a receiver operating characteristic curve analysis for the survival of patients with sepsis, the area under the curve (AUC) for pro-ANP was 0.88, which was significantly greater than the AUCs for procalcitonin and C-reactive protein, and similar to the AUC for the APACHE II score.

Conclusion

Pro-ANP appears to be a valuable tool for individual risk assessment in sepsis patients and for stratification of high-risk patients in future intervention trials. Further studies are needed to validate our results.

Brain natriuretic peptide: a potential marker for mortality in septic shock

Brain natriuretic peptide (BNP) is a diagnostic marker for left ventricular dysfunction. Sepsis and septic shock are increasing in incidence and mortality. Myocardial dysfunction frequently accompanies severe sepsis and septic shock. Although previously described as a preterminal event, ventricular dysfunction with reduced ejection fraction and biventricular dilatation is present in most patients with severe sepsis and septic shock. In survivors, this depression in cardiac function is reversible over the course of seven to ten days. Even though some prognostic factors have been identified in patients with sepsis-induced myocardial dysfunction, their measurement often includes costly and cumbersome techniques. Thus, there is a need for an inexpensive, simple, rapid and readily available marker to predict mortality in septic shock. At present, a relationship between BNP with myocardial dysfunction in septic shock has not been evaluated. However, growing evidence supports the hypothesis that BNP could be an early predictor of mortality in septic shock. If proven, the hypothesis would have important clinical and public health implications.

Science review: natriuretic peptides in critical illness

The present review will cover the mechanisms of release and the potential pathophysiological role of different natriuretic peptides in critically ill patients. By focusing on the cardiovascular system, possible implications of natriuretic peptides for diagnosis and treatment will be presented. In critical illness such as sepsis, trauma or major surgery, systemic hypotension and an intrinsic myocardial dysfunction occur. Impairment of the cardiovascular system contributes to poor prognosis in severe human sepsis. Natriuretic peptides have emerged as valuable marker substances to detect left ventricular dysfunction in congestive heart failure of different origins. Increased plasma levels of circulating natriuretic peptides, atrial natriuretic peptide, N-terminal pro-atrial natriuretic peptide, brain natriuretic peptide and its N-terminal moiety N-terminal pro-brain natriuretic peptide have also been found in critically ill patients. All of these peptides have been reported to reflect left ventricular dysfunction in these patients. The increased wall stress of the cardiac atria and ventricles is followed by the release of these natriuretic peptides. Furthermore, the release of atrial natriuretic peptide and brain natriuretic peptide might be triggered by members of the IL-6-related family and endotoxin in the critically ill. Apart from the vasoactive actions of circulating natriuretic peptides and their broad effects on the renal system, anti-ischemic properties and immunological functions have been reported for atrial natriuretic peptide. The early onset and rapid reversibility of left ventricular impairment in patients with good prognosis associated with a remarkably augmented plasma concentration of circulating natriuretic peptides suggest a possible role of these hormones in the monitoring of therapy success and the estimation of prognosis in the critically ill.

Brain natriuretic peptide: A marker of myocardial dysfunction and prognosis during severe sepsis

OBJECTIVE

To investigate the value of brain natriuretic peptide plasma levels as a marker of systolic myocardial dysfunction during severe sepsis and septic shock.

DESIGN

Prospective observational study.

SETTING

Intensive care unit.

PATIENTS

A total of 34 consecutive patients with severe sepsis (nine patients) or septic shock (25 patients) without previous cardiac, respiratory, or chronic renal failure.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Myocardial systolic performance was assessed by fractional area contraction (FAC) using echocardiography performed on days 2 (FACD2) and 8. Plasma levels of brain natriuretic peptide were measured at days 1-4 and 8 after the beginning of severe sepsis. Among 34 patients (Simplified Acute Physiology Score II, 43 +/- 2.5), 15 (44%) presented with initial myocardial dysfunction (FACD2 < 50%). Lungs were the origin of sepsis in 65% of patients. The 28-day mortality was 29%. Comparisons were performed between patients with (FACD2 < 50%) and without (FACD2 > or = 50%) myocardial dysfunction. Plasma levels of brain natriuretic peptide were significantly higher in patients with FACD2 < 50% than in those with FACD2 > or = 50% (p <.05) from day 2 to day 4. Brain natriuretic peptide levels were also significantly higher on days 2 and 3 in patients who died during their intensive care unit stay (p <.05).

CONCLUSIONS

Systolic myocardial dysfunction is present in 44% of patient with severe sepsis or septic shock. In this setting, brain natriuretic peptide seems useful to detect myocardial dysfunction, and high plasma levels appear to be associated with poor outcome of sepsis, but further studies are needed.

Complement activation, endothelin-1 and neuropeptide Y in relation to the cardiovascular response to endotoxin-induced systemic inflammation in healthy volunteers

BACKGROUND

Endotoxin is a major stimulus for triggering the host response in septicaemia. The pathophysiology of sepsis involves activation of the vascular endothelium and leukocytes, resulting in the release of various mediators, e.g. cytokines, nitric oxide (NO), endothelin (ET-1) and complement factors. We evaluated the blood levels of complement activation, ET-1 and neuropeptide Y (NPY) in parallel with the haemodynamic and oxygen transport response during human experimental endotoxemia.

METHODS

Eleven healthy men had venous, arterial and pulmonary arterial catheters placed for continuous haemodynamic measuring. After 30 min rest endotoxin (E. Coli 4 ng kg(-1), Lot G1) was intravenously administered. Blood samples from pulmonary and arterial catheters were collected hourly over 4 h.

RESULTS

Body temperature augmented significantly from baseline values (36.7 +/- 0.7 degrees C, mean +/- SEM) with a maximum after 3.5 h (39.1 +/- 0.3 degrees C, P < 0.001). Cardiac output increased by 100%, systemic vascular resistance decreased by 50%, the oxygen consumption and the tissue oxygen transport increased. Activation of the complement system was indicated by an increase in SC5b-9. Endothelin-1-like immunoreactivity (ET-1-LI) increased over time in arterial blood. NPY-like immunoreactivity (NPY-LI) did not change over time.

CONCLUSION

A dose of endotoxin associated with reproducible systemic vasodilation and fever in healthy subjects causes complement activation and increased systemic levels of ET-1-LI, illustrating that the model is a useful tool for inducing moderate systemic inflammation where several mediator systems are activated.

Relationship between Natriuretic Peptides and Residual Diuresis during Continuous Hemodiafiltration

BACKGROUND

The reasons for the decrease or increase of urine output following the start of continuous venovenous hemodiafiltration (CVVHDF) have not yet been explained sufficiently. The renoprotective properties of natriuretic peptides were described.

METHODS

The levels of atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) were measured in 23 mechanically ventilated patients before and during the first 48 h of CVVHDF. Samples were drawn both from the ports proximal and distal to the filter. The results were compared between the group where daily diuresis (Vu) remained low or decreased and the group where diuresis increased to the level of 1.5 ml x kg(-1) x h(-1) or higher after 48 h of treatment. Left ventricular dysfunction (LVD) was defined as LV ejection fraction below 40%. A control group consisted of 10 patients exposed to abdominal surgery.

RESULTS

The average AVdiff (%) of ANP and BNP on filter were insignificant. Patients with increasing diuresis (n = 12) had significantly lower levels of both ANP (p < 0.001) and BNP (p < 0.005) than the patients with decreasing diuresis (n = 11). Significant correlations were revealed for ANP and Vu (p < 0.01) and for BNP and Vu (p < 0.05). The levels of both peptides were grossly elevated in comparison to controls and were predictive of survival. The differences between cardiac and non-cardiac patients were significant both for ANP and for BNP.

CONCLUSIONS

The elimination of ANP and BNP by the CVVHDF is negligible. The levels of natriuretic peptides are inversely related to Vu and predict survival. ANP and BNP levels correlate with left ventricular function even during acute renal failure and CVVHDF.

ANP inhibits TNF-alpha-induced endothelial MCP-1 expression--involvement of p38 MAPK and MKP-1

Atrial natriuretic peptide (ANP) has been shown to reduce tumor necrosis factor-alpha (TNF-alpha)-induced activation of endothelial cells via inhibition of p38 mitogen-activated protein kinase (MAPK) and nuclear factor (NF)-kappaB pathways. The aim of this study was to determine whether ANP is able to inhibit TNF-alpha-induced expression of monocyte chemoattractant protein-1 (MCP-1) in endothelial cells and to elucidate the mechanisms involved. Pretreatment of human umbilical vein endothelial cells (HUVEC) with ANP significantly reduced TNF-alpha-induced expression of MCP-1 protein and mRNA. The effects of ANP were shown to be mediated via the guanylyl-cyclase (GC)-coupled A receptor. Activation of the other GC-coupled receptor (natriuretic peptide receptor-B) by the C-type natriuretic peptide as well as activation of soluble GC with S-nitroso-L-glutathione (GSNO) exerted similar effects as ANP, supporting a role for cyclic guanosine monophosphate (cGMP) in the signal transduction. Antisense experiments showed a requirement of MAPK phosphatase-1 (MKP-1) induction and therefore, inhibition of p38 MAPK in the ANP-mediated inhibition of TNF-alpha-induced expression of MCP-1. To investigate a potential interplay between TNF-alpha-induced activation of p38 MAPK and NF-kappaB, the p38 MAPK inhibitor SB203580 and a dominant-negative p38 MAPK mutant were used. The results indicated that the blockade of p38 MAPK activity leads to an increased activation of NF-kappaB and therefore, suggest a counter-regulatory action of p38 MAPK and NF-kappaB. As antisense experiments revealed a pivotal role for MKP-1 induction and therefore, p38 MAPK inhibition in ANP-mediated attenuation of MCP-1 expression, this action seems to be rather independent of NF-kappaB inhibition.

Does methylene blue administration to septic shock patients affect vascular permeability and blood volume?

OBJECTIVE

To assess the effects of the inhibition of guanylate cyclase, an enzyme involved in sepsis-related vascular and myocardial dysfunctions, on hemodynamic variables including blood volume and pulmonary vascular permeability during septic shock.

DESIGN

Prospective, open study with repeated measurements.

SETTING

A medicosurgical intensive care unit of a university hospital.

PATIENTS

Fifteen patients with septic shock associated with persisting hypotension despite conventional treatment including fluid loading, vasopressors, and inotropes.

INTERVENTIONS

A fiberoptic catheter was inserted for the determination of blood and extravascular volumes by the thermal-dye double indicator technique, using indocyanine green (COLD system). A bolus dose of methylene blue (3 mg/kg) was infused intravenously over 10 mins. COLD-derived variables were recorded before methylene blue and 20 mins, 1 hr, and 2 hrs after the end of methylene blue infusion.

MEASUREMENTS AND MAIN RESULTS

Standard hemodynamic and oxygen-derived variables; total, intrathoracic, systolic, and diastolic cardiac blood volumes; extravascular lung water; plasma osmolarity; and lactate and protein concentrations were recorded. Mean arterial and pulmonary artery pressures, systemic and pulmonary vascular resistances, and left ventricular stroke work index increased, and blood lactate transiently decreased after methylene blue (p <.05). The other variables recorded were unchanged during the 2-hr period following methylene blue infusion.

CONCLUSIONS

This study confirmed the acute vasoconstrictive and positive inotropic effects of methylene blue during septic shock. These effects were not associated with changes in blood volume, myocardial diastolic function, or pulmonary vascular permeability assessed by extravascular lung water.

Pro-atrial natriuretic peptide hormone from right atria is correlated with cardiac depression in septic patients

N-terminal pro-atrial natriuretic peptide [proANP(1-98)] has been extensively investigated in patients with chronic heart failure and ishemic heart disease. It is found to be a better marker of cardiac dysfunction than atrial natriuretic peptide (ANP). The possible involvement of proANP(1-98) in cardiac depression caused by sepsis has not been studied yet. Therefore, we analyzed atrial plasma concentration of proANP(1-98) in 17 septic patients with hemodynamic variables measured or calculated using pulmonary artery catheter. The results of altogether 96 measurements show a significant negative correlation of proANP(1-98) and cardiac index (p<0.024), oxygen delivery (p<0.03) and oxygen consumption (p<0.03). There is also a positive correlation with pulmonary vascular resistance (p<0.03). ProANP(1-98) is significantly higher in patients who developed acute respiratory distress syndrome (ARDS) (p<0.001). This study implies that proANP(1-98) is a possible novel hormone marker of cardiac depression caused by sepsis that could be used for prediction of ARDS.