Myocardial dysfunction in septic shock: Part I. Clinical manifestation of cardiovascular dysfunction

Assessment of Dynamic Changes in Stressed Volume and Venous Return during Hyperdynamic Septic Shock

The present work investigated the dynamic changes in stressed volume (Vs) and other determinants of venous return using a porcine model of hyperdynamic septic shock. Septicemia was induced in 10 anesthetized swine, and fluid challenges were started after the diagnosis of sepsis-induced arterial hypotension and/or tissue hypoperfusion. Norepinephrine infusion targeting a mean arterial pressure (MAP) of 65 mmHg was started after three consecutive fluid challenges. After septic shock was confirmed, norepinephrine infusion was discontinued, and the animals were left untreated until cardiac arrest occurred. Baseline Vs decreased by 7% for each mmHg decrease in MAP during progression of septic shock. Mean circulatory filling pressure (Pmcf) analogue (Pmca), right atrial pressure, resistance to venous return, and efficiency of the heart decreased with time (p < 0.001 for all). Fluid challenges did not improve hemodynamics, but noradrenaline increased Vs from 107 mL to 257 mL (140%) and MAP from 45 mmHg to 66 mmHg (47%). Baseline Pmca and post-cardiac arrest Pmcf did not differ significantly (14.3 ± 1.23 mmHg vs. 14.75 ± 1.5 mmHg, p = 0.24), but the difference between pre-arrest Pmca and post-cardiac arrest Pmcf was statistically significant (9.5 ± 0.57 mmHg vs. 14.75 ± 1.5 mmHg, p < 0.001). In conclusion, the baseline Vs decreased by 7% for each mmHg decrease in MAP during progression of hyperdynamic septic shock. Significant changes were also observed in other determinants of venous return. A new physiological intravascular volume existing at zero transmural distending pressure was identified, termed as the rest volume (Vr).

Should Vasopressors Be Started Early in Septic Shock?

Sepsis can influence blood volume, its distribution, vascular tone, and cardiac function. Persistent hypotension or the need for vasopressors after volume resuscitation is part of the definition of septic shock. Since increased positive fluid balance has been associated with increased morbidity and mortality in sepsis, timing of vasopressors in the treatment of septic shock seems crucial. However, conclusive evidence on timing and sequence of interventions with the goal to restore tissue perfusion is lacking. The aim of this narrative review is to depict the pathophysiology of hypotension in sepsis, evaluate how common interventions to treat hypotension interfere with physiology, and to give a resume of the results from clinical studies focusing on targets and timing of vasopressor in sepsis. The majority of studies comparing early versus late administration of vasopressors in septic shock are rather small, single-center, and retrospective. The range of "early" is between 1 and 12 hours. The available studies suggest a mean arterial pressure of 60 to 65 mm Hg as a threshold for increased risk of morbidity and mortality, whereas higher blood pressure targets do not seem to add further benefits. The data, albeit mostly from observational studies, speak for combining vasopressors with fluids rather "early" in the treatment of septic shock (within a 0-3-hour window). Nevertheless, the optimal resuscitation strategy should take into account the source of infection, the pathophysiology, the time and clinical course preceding the diagnosis of sepsis, and also comorbidities and sepsis-induced organ dysfunction.

Emerging benefits and drawbacks of α2 -adrenoceptor agonists in the management of sepsis and critical illness

Agonists of α₂ -adrenoceptors are increasingly being used for the provision of comfort, sedation and the management of delirium in critically ill patients, with and without sepsis. In this context, increased sympathetic and inflammatory activity are common pathophysiological features linked to multi-organ dysfunction, particularly in patients with sepsis or those undergoing cardiac surgery requiring cardiopulmonary bypass. Experimental and clinical studies support the notion that the α₂ -adrenoceptor agonists, dexmedetomidine and clonidine, mitigate sympathetic and inflammatory overactivity in sepsis and cardiac surgery requiring cardiopulmonary bypass. These effects can protect vital organs, including the cardiovascular system, kidneys, heart and brain. We review the pharmacodynamic mechanisms by which α₂ -adrenoceptor agonists might mitigate multi-organ dysfunction arising from pathophysiological conditions associated with excessive inflammatory and adrenergic stress in experimental studies. We also outline recent clinical trials that have examined the use of dexmedetomidine in critically ill patients with and without sepsis and in patients undergoing cardiac surgery.

Pathophysiology of Acute Illness and Injury

The pathophysiology of acute illness and injury recognizes three main effectors: infection, trauma, and ischemia-reperfusion injury. Each of them can act by itself or in combination with the other two in developing a systemic inflammatory reaction syndrome (SIRS) that is a generalized reaction to the morbid event. The time course of SIRS is variable and influenced by the number and severity of subsequent insults (e.g., reparative surgery, acquired hospital infections). It occurs simultaneously with a complex of counter-regulatory mechanisms (compensatory anti-inflammatory response syndrome, CARS) that limit the aggressive effects of SIRS. In adjunct, a progressive dysfunction of the acquired (lymphocytes) immune system develops with increased risk for immunoparalysis and associated infectious complications. Both humoral and cellular effectors participate to the development of SIRS and CARS. The most important humoral mediators are pro-inflammatory (IL-1β, IL-6, IL-8, IL-12) and anti-inflammatory (IL-4, IL-10) cytokines and chemokines, complement, leukotrienes, and PAF. Effector cells include neutrophils, monocytes, macrophages, lymphocytes, and endothelial cells. The endothelium is a key factor for production of remote organ damage as it exerts potent chemo-attracting effects on inflammatory cells, allows for leukocyte trafficking into tissues and organs, and promotes further inflammation by cytokines release. Moreover, the loss of vasoregulatory properties and the increased permeability contribute to the development of hypotension and tissue edema. Finally, the disseminated activation of the coagulation cascade causes the widespread deposition of microthrombi with resulting maldistribution of capillary blood flow and ultimately hypoxic cellular damage. This mechanism together with increased vascular permeability and vasodilation is responsible for the development of the multiple organ dysfunction syndrome (MODS).

Dual Behavior of Exosomes in Septic Cardiomyopathy

Sepsis is one of the main causes of ICU hospitalization worldwide, with a high mortality rate, and is associated with a large number of comorbidities. One of the main comorbidities associated with sepsis is septic cardiomyopathy. This process occurs mainly due to mechanisms of damage in the cardiovascular system that will lead to changes in cardiovascular physiology, such as decreased Ca²⁺ response, mitochondrial dysfunction and decreased β-adrenergic receptor response. Within this process the exosomes play an important role in the pathophysiology of this disease, in which the exosomal content is related to mechanisms that will trigger its development. After platelet activation through ROS exposition, exosomes containing high concentrations of NADPH are released in heart blood vessels, those exosomes will be internalized in endothelial cells leading to cell death and cardiac dysfunction. On the opposite, exosomes derived from mesenchymal stem cells contain miR-223, that have anti-inflammatory properties, are released in less quantities in septic patients causing an imbalance that leads to cardiac dysfunction.

Complement and sepsis-induced heart dysfunction

It is well known that cardiac dysfunction develops during sepsis in both humans and in rodents (rats, mice). These defects appear to be reversible, since after "recovery" from sepsis, cardiac dysfunction disappears and the heart returns to its function that was present before the onset of sepsis. Our studies, using in vivo and in vitro models, have demonstrated that C5a and its receptors (C5aR1 and C5aR2) play key roles in cardiac dysfunction developing during sepsis. Use of a neutralizing antibody to C5a largely attenuates cardiac dysfunction and other adverse events developing during sepsis. The molecular basis for cardiac dysfunctions is linked to generation of C5a and its interaction with C5a receptors present on surfaces of cardiomyocytes (CMs). It is established that C5a interactions with C5a receptors leads to significant reductions involving faulty contractility and relaxation in CMs. In addition, C5a interactions with C5a receptors on CMs results in reductions in Na⁺/K⁺-ATPase in CMs. This ATPase is essential for intact action potentials in CMs. The enzymatic activity and protein for this ATPase were strikingly reduced in CMs during sepsis by unknown mechanisms. In addition, C5a interactions with C5aRs also caused reductions in CM homeostatic proteins that regulate cytosolic [Ca²⁺]i in CMs: sarco/endoplasmic reticulum Ca²⁺-ATPase2 (SERCA2) and Na⁺/Ca²⁺ exchanger (NCX). In the absence of C5a receptors, defects in SERCA2 and NCX in CMs after sepsis are strikingly attenuated. These observations suggest new strategies to protect the heart from dysfunction developing during sepsis.

PPARα augments heart function and cardiac fatty acid oxidation in early experimental polymicrobial sepsis

Children with sepsis and multisystem organ failure have downregulated leukocyte gene expression of peroxisome proliferator-activated receptor-α (PPARα), a nuclear hormone receptor transcription factor that regulates inflammation and lipid metabolism. Mouse models of sepsis have likewise demonstrated that the absence of PPARα is associated with decreased survival and organ injury, specifically of the heart. Using a clinically relevant mouse model of early sepsis, we found that heart function increases in wild-type (WT) mice over the first 24 h of sepsis, but that mice lacking PPARα (Ppara^-/-) cannot sustain the elevated heart function necessary to compensate for sepsis pathophysiology. Left ventricular shortening fraction, measured 24 h after initiation of sepsis by echocardiography, was higher in WT mice than in Ppara^-/- mice. Ex vivo working heart studies demonstrated greater developed pressure, contractility, and aortic outflow in WT compared with Ppara^-/- mice. Furthermore, cardiac fatty acid oxidation was increased in WT but not in Ppara^-/- mice. Regulatory pathways controlling pyruvate incorporation into the citric acid cycle were inhibited by sepsis in both genotypes, but the regulatory state of enzymes controlling fatty acid oxidation appeared to be permissive in WT mice only. Mitochondrial ultrastructure was not altered in either genotype indicating that severe mitochondrial dysfunction is unlikely at this stage of sepsis. These data suggest that PPARα expression supports the hyperdynamic cardiac response early in the course of sepsis and that increased fatty acid oxidation may prevent morbidity and mortality.

NEW & NOTEWORTHY

In contrast to previous studies in septic shock using experimental mouse models, we are the first to demonstrate that heart function increases early in sepsis with an associated augmentation of cardiac fatty acid oxidation. Absence of peroxisome proliferator-activated receptor-α (PPARα) results in reduced cardiac performance and fatty acid oxidation in sepsis.

Interleukin-27 is elevated in sepsis-induced myocardial dysfunction and mediates inflammation

INTRODUCTION

Interleukin (IL)-27 is an important cytokine involved in many human inflammatory diseases. In this study, we investigated its role in the pathogenesis of sepsis-induced myocardial dysfunction (SIMD).

METHODS

Twenty patients with SIMD and 24healthy donors were prospectively enrolled. Expression of IL-27 was detected in serum from SIMD patients by ELISA. Cardiac dysfunction was induced by administration of Escherichia coli lipopolysaccharide (LPS) to C57BL/6 (wild type) or IL-27R^-/- mice. IL-27 mRNA in the myocardium was measured by RT-PCR. Cytokine levels in serum were determined by ELISA.

RESULTS

Expression of IL-27 in the serum was markedly increased in patients with SIMD compared with that in controls. Serum IL-27 levels and cardiac IL-27 mRNA expression were significantly increased after LPS injection compared with control specimens. Compared with wild-type mice, IL-27R^-/- mice had higher expression of brain natriuretic peptide, cardiac troponin I, IL-6, IL-12, tumor necrosis factor-α and transforming growth factor-β.

CONCLUSIONS

IL-27 is an important protective mediator of SIMD.

Early norepinephrine decreases fluid and ventilatory requirements in pediatric vasodilatory septic shock

AIMS

We previously reported that vasodilatation was common in pediatric septic shock, regardless of whether they were warm or cold, providing a rationale for early norepinephrine (NE) to increase venous return (VR) and arterial tone. Our primary aim was to evaluate the effect of smaller fluid bolus plus early-NE versus the American College of Critical Care Medicine (ACCM) approach to more liberal fluid boluses and vasoactive-inotropic agents on fluid balance, shock resolution, ventilator support and mortality in children with septic shock. Secondly, the impact of early NE on hemodynamic parameters, urine output and lactate levels was assessed using multimodality-monitoring.

METHODS

In keeping with the primary aim, the early NE group (N-27) received NE after 30ml/kg fluid, while the ACCM group (N-41) were a historical cohort managed as per the ACCM Guidelines, where after 40-60ml/kg fluid, patients received first line vasoactive-inotropic agents. The effect of early-NE was characterized by measuring stroke volume variation(SVV), systemic vascular resistance index (SVRI) and cardiac function before and after NE, which were monitored using ECHO + Ultrasound-Cardiac-Output-Monitor (USCOM) and lactates.

RESULTS

The 6-hr fluid requirement in the early-NE group (88.9+31.3 to 37.4+15.1ml/kg), and ventilated days [median 4 days (IQR 2.5-5.25) to 1day (IQR 1-1.7)] were significantly less as compared to the ACCM group. However, shock resolution and mortality rates were similar. In the early NE group, the overall SVRI was low (mean 679.7dynes/sec/cm5/m2, SD 204.5), and SVV decreased from 23.8±8.2 to 18.5±9.7, p=0.005 with NE infusion suggesting improved preload even without further fluid loading. Furthermore, lactate levels decreased and urine-output improved.

CONCLUSION

Early-NE and fluid restriction may be of benefit in resolving shock with less fluid and ventilator support as compared to the ACCM approach.

Effects of selective β1-adrenoceptor blockade on cardiovascular and renal function and circulating cytokines in ovine hyperdynamic sepsis

Introduction

Activation of the sympathetic nervous system has beneficial cardiovascular effects in sepsis, but there is also evidence that sympatholytics have beneficial actions in sepsis. We therefore determined the effect of selective β₁-adrenoceptor blockade on cardiac and renal function and cytokine release in ovine hyperdynamic sepsis.

Methods

Hyperdynamic sepsis was induced by infusion of live E. coli for 24 hours in nine conscious sheep instrumented with flow probes on the pulmonary and left renal artery. Cardiovascular and renal function and levels of plasma cytokines were determined in a control group and during selective β1-adrenoceptor blockade with atenolol (10 mg intravenous bolus then 0.125 mg/kg/h) from 8 to 24 hours of sepsis.

Results

Hyperdynamic sepsis was characterized by hypotension with increases in cardiac output (CO), heart rate (HR) and renal blood flow (RBF), and acute kidney injury. Atenolol caused sustained reductions in HR (P <0.001) and CO (P <0.001). Despite the lower CO the sepsis-induced fall in mean arterial pressure (MAP) was similar in both groups. The sepsis-induced increase in RBF, decrease in renal function and increase in arterial lactate were unaffected by atenolol. Sepsis increased plasma levels of tumour necrosis factor alpha (TNF-α), interleukin 6 (IL-6) and IL-10. Atenolol caused a further increase in IL-10, but did not affect levels of TNF-α or IL-6.

Conclusions

In sepsis, selective β₁-adrenoceptor blockade reduced CO, but not MAP. During sepsis, atenolol did not alter the development of acute kidney injury or the levels of pro-inflammatory cytokines, but enhanced the release of IL-10. Atenolol appears safe in sepsis, has no deleterious cardiovascular or renal effects, and has an anti-inflammatory effect.

Adiponectin ameliorates endotoxin-induced acute cardiac injury

Background. Obesity is a risk factor for cardiovascular disease. Increasing evidence suggests that reduced levels of the adipocyte-derived plasma protein adiponectin are associated with an increased cardiovascular risk. Here, we examined the effects of adiponectin on lipopolysaccharide- (LPS-) induced acute cardiac injury in vivo. Methods and Results. A single dose of LPS (10 mg/kg) was intraperitoneally injected into wild-type (WT) and adiponectin-knockout (APN-KO) mice. Following LPS administration, APN-KO mice had exacerbation of left ventricular (LV) systolic dysfunction compared with WT mice. Administration of LPS to WT and APN-KO mice led to an increased expression of inflammatory cytokines including TNF-α and IL-6 in the heart, but the magnitude of this induction was greater in APN-KO mice compared to WT mice. Systemic delivery of an adenoviral vector expressing adiponectin (Ad-APN) improved LPS-induced LV dysfunction in APN-KO mice, and this effect was accompanied by the reduced expression of TNF-α and IL-6 in the heart. Administration of etanercept, a soluble TNF receptor abolished the reduced LV contractile function in response to LPS in APN-KO mice. Conclusion. These results suggest that adiponectin protects against LPS-induced acute cardiac injury by suppressing cardiac inflammatory responses, and could represent a potential therapeutic target in sepsis-associated myocardial dysfunction.

Timing of vasopressor initiation and mortality in septic shock: a cohort study

Introduction

Despite recent advances in the management of septic shock, mortality remains unacceptably high. Earlier initiation of key therapies including appropriate antimicrobials and fluid resuscitation appears to reduce the mortality in this condition. This study examined whether early initiation of vasopressor therapy is associated with improved survival in fluid therapy-refractory septic shock.

Methods

Utilizing a well-established database, relevant information including duration of time to vasopressor administration following the initial documentation of recurrent/persistent hypotension associated with septic shock was assessed in 8,670 adult patients from 28 ICUs in Canada, the United States of America, and Saudi Arabia. The primary endpoint was survival to hospital discharge. Secondary endpoints were length of ICU and hospital stay as well as duration of ventilator support and vasopressor dependence. Analysis involved multivariate linear and logistic regression analysis.

Results

In total, 8,640 patients met the definition of septic shock with time of vasopressor/inotropic initiation documented. Of these, 6,514 were suitable for analysis. The overall unadjusted hospital mortality rate was 53%. Independent mortality correlates included liver failure (odds ratio (OR) 3.46, 95% confidence interval (CI), 2.67 to 4.48), metastatic cancer (OR 1.63, CI, 1.32 to 2.01), AIDS (OR 1.91, CI, 1.29 to 2.49), hematologic malignancy (OR 1.88, CI, 1.46 to 2.41), neutropenia (OR 1.78, CI, 1.27 to 2.49) and chronic hypertension (OR 0.62 CI, 0.52 to 0.73). Delay of initiation of appropriate antimicrobial therapy (OR 1.07/hr, CI, 1.06 to 1.08), age (OR 1.03/yr, CI, 1.02 to 1.03), and Acute Physiology and Chronic Health Evaluation (APACHE) II Score (OR 1.11/point, CI, 1.10 to 1.12) were also found to be significant independent correlates of mortality. After adjustment, only a weak correlation between vasopressor delay and hospital mortality was found (adjusted OR 1.02/hr, 95% CI 1.01 to 1.03, P <0.001). This weak effect was entirely driven by the group of patients with the longest delays (>14.1 hours). There was no significant relationship of vasopressor initiation delay to duration of vasopressor therapy (P = 0.313) and only a trend to longer duration of ventilator support (P = 0.055) among survivors.

Conclusion

Marked delays in initiation of vasopressor/inotropic therapy are associated with a small increase in mortality risk in patients with septic shock.

Multimodal monitoring for hemodynamic categorization and management of pediatric septic shock: a pilot observational study*

OBJECTIVES

To evaluate the cardiovascular aberrations using multimodal monitoring in fluid refractory pediatric septic shock and describe the clinical characteristics of septic myocardial dysfunction.

DESIGN

Prospective observational study of patients with unresolved septic shock after infusion of 40 mL/kg fluid in the first hour.

SETTING

Two tertiary care referral Indian PICUs.

PATIENTS

Patients aged 1 month to 16 years who had fluid refractory septic shock.

INTERVENTIONS

Changes in therapy were based on findings of clinical assessment, bedside echocardiography, and invasive blood pressure monitoring within 6 hours of recognition of septic shock.

MEASUREMENTS AND MAIN RESULTS

Over a 4-year period, 48 patients remained in septic shock despite at least 40 mL/kg fluid infusion. On clinical examination, 21 patients had cold shock and 27 had warm shock. Forty-one patients (85.5%) had vasodilatory shock on invasive blood pressure; these included 14 patients who initially presented with cold shock. The commonest echocardiography findings were impaired left ± right ventricular function in 19 patients (39.6%) and hypovolemia in 16 patients (33%). Three patients who had normal myocardial function on day 1 developed secondary septic myocardial dysfunction on day 3. Echocardio graphy, along with invasive arterial pressure monitoring, allowed fluid, inotropy, and pressors to be titrated more precisely in 87.5% of patients. Shock resolved in 46 of 48 patients (96%) and 44 patients (91.6%) survived to discharge.

CONCLUSION

Bedside echocardiography provided crucial information leading to the recognition of septic myocardial dysfunction and uncorrected hypovolemia that was not apparent on clinical assessment. With invasive blood pressure monitoring, echocardiography affords a simple noninvasive tool to determine the cause of low cardiac output and the physiological basis for adjustment of therapy in patients who remain in shock despite 40 mL/kg fluid.

The effects of tumor necrosis factor-alpha on systolic and diastolic function in rat ventricular myocytes

The proinflammatory cytokine tumor necrosis factor-alpha (TNF-α) is associated with myocardial dysfunction observed in sepsis and septic shock. There are two fundamental components to this dysfunction. (1) systolic dysfunction; and (2) diastolic dysfunction. The aim of these experiments was to determine if any aspect of whole-heart dysfunction could be explained by alterations to global intracellular calcium ([Ca²⁺]_i), contractility, and [Ca²⁺]_i handling, by TNF-α, at the level of the individual rat myocyte. We took an integrative approach to simultaneously measure [Ca²⁺]_i, contractility and sarcolemmal Ca fluxes using the Ca indicator fluo-3, video edge detection, and the perforated patch technique, respectively. All experiments were performed at 37°C. The effects of 50 ng/mL TNF-α were immediate and sustained. The amplitude of systolic [Ca²⁺]_i was reduced by 31% and systolic shortening by 19%. Diastolic [Ca²⁺]_i, myocyte length and relaxation rate were not affected, nor were the activity of the [Ca²⁺]_i removal mechanisms. The reduction in systolic [Ca²⁺]_i was associated with a 14% reduction in sarcoplasmic reticulum (SR) content and a 11% decrease in peak L-type Ca current (I_Ca-L). Ca influx was decreased by 7% associated with a more rapid I_Ca-L inactivation. These data show that at the level of the myocyte, TNF-α reduces SR Ca which underlies a reduction in systolic [Ca²⁺]_i and thence shortening. Although these findings correlate well with aspects of systolic myocardial dysfunction seen in sepsis, in this model, acutely, TNF-α does not appear to provide a cellular mechanism for sepsis-related diastolic myocardial dysfunction.

The soluble guanylate cyclase activator BAY 58-2667 protects against morbidity and mortality in endotoxic shock by recoupling organ systems

Sepsis and septic shock are associated with high mortality rates and the majority of sepsis patients die due to complications of multiple organ failure (MOF). The cyclic GMP (cGMP) producing enzyme soluble guanylate cyclase (sGC) is crucially involved in the regulation of (micro)vascular homeostasis, cardiac function and, consequently, organ function. However, it can become inactivated when exposed to reactive oxygen species (ROS). The resulting heme-free sGC can be reactivated by the heme- and nitric oxide (NO)-independent sGC activator BAY 58-2667 (Cinaciguat). We report that late (+8 h) post-treatment with BAY 58-2667 in a mouse model can protect against lethal endotoxic shock. Protection was associated with reduced hypothermia, circulating IL-6 levels, cardiomyocyte apoptosis, and mortality. In contrast to BAY 58-2667, the sGC stimulator BAY 41-2272 and the phosphodiesterase 5 inhibitor Sildenafil did not have any beneficial effect on survival, emphasizing the importance of the selectivity of BAY 58-2667 for diseased vessels and tissues. Hemodynamic parameters (blood pressure and heart rate) were decreased, and linear and nonlinear indices of blood pressure variability, reflective for (un)coupling of the communication between the autonomic nervous system and the heart, were improved after late protective treatment with BAY 58-2667. In conclusion, our results demonstrate the pivotal role of the NO/sGC axis in endotoxic shock. Stabilization of sGC function with BAY 58-2667 can prevent mortality when given in the correct treatment window, which probably depends on the dynamics of the heme-free sGC pool, in turn influenced by oxidative stress. We speculate that, considering the central role of sGC signaling in many pathways required for maintenance of (micro)circulatory homeostasis, BAY 58-2667 supports organ function by recoupling inter-organ communication pathways.

Bedside echocardiography is useful in assessing children with fluid and inotrope resistant septic shock

OBJECTIVE

To report changes in the cardiovascular management of fluid and inotropic resistant septic shock in children based on echocardiography.

DESIGN

Retrospective case series.

SETTING

Tertiary care Pediatric Intensive Care Unit (PICU), Chennai.

PATIENTS

Twenty-two patients with unresolved septic shock after 60 ml/kg fluid plus inotropic agents in the first hour.

INTERVENTIONS

Bedside echocardiography (echo) within 6 h of admission to the PICU.

RESULTS

Over a 28-month period, of 37 patients with septic shock, 22 children remained in shock despite 60 ml/kg fluid and dopamine and/or dobutamine infusions as per guidelines. On clinical exam, 12 patients had warm shock and ten had cold shock, however, six exhibited an unusual pattern of cold shock with wide pulse pressures on invasive arterial monitoring. The most common echocardiographic finding was uncorrected hypovolemia in 12/22 patient while ten patients had impaired left ± right ventricular function. Echocardiography permitted an appreciation of the underlying disordered pathophysiology and a rationale for adjustment of treatment. Shock resolved in 17 (77%) and 16 patients (73%) survived to discharge.

CONCLUSIONS

Bedside echo provided crucial information that was not apparent on clinical assessment and affords a simple noninvasive tool to determine the cause of low cardiac output in patients who remain in shock despite 60 ml/kg fluid and inotropic support. Most patients in our series had vasodilatory shock with wide pulse pressures and most common finding on echo was uncorrected hypovolemia. The echo findings allowed adjustment of therapy which was not possible based on clinical examination alone.

Role of the venous return in critical illness and shock: part II-shock and mechanical ventilation

OBJECTIVE

To provide a conceptual and clinical review of the physiology of the venous system as it is related to cardiac function in health and disease.

DATA

An integration of venous and cardiac physiology under normal conditions, critical illness, and resuscitation.

SUMMARY

The usual clinical teaching of cardiac physiology focuses on left ventricular pathophysiology and pathology. Due to the wide array of shock states dealt with by intensivists, an integrated approach that takes into account the function of the venous system and its interaction with the right heart may be more useful. In part II of this two-part review, we describe the physiology of venous return and its interaction with the right heart function as it relates to mechanical ventilation and various shock states including hypovolemic, cardiogenic, obstructive, and septic shock. In particular, we demonstrate how these shock states perturb venous return/right heart interactions. We also show how compensatory mechanisms and therapeutic interventions can tend to return venous return and cardiac output to appropriate values.

CONCLUSION

An improved understanding of the role of the venous system in pathophysiologic conditions will allow intensivists to better appreciate the complex circulatory physiology of shock and related therapies. This should enable improved hemodynamic management of this disorder.

Endothelial NOS (NOS3) impairs myocardial function in developing sepsis

Endothelial nitric oxide synthase (NOS)3-derived nitric oxide (NO) modulates inotropic response and diastolic interval for optimal cardiac performance under non-inflammatory conditions. In sepsis, excessive NO production plays a key role in severe hypotension and myocardial dysfunction. We aimed to determine the role of NOS3 on myocardial performance, NO production, and time course of sepsis development. NOS3(-/-) and C57BL/6 wildtype mice were rendered septic by cecum ligation and puncture (CLP). Cardiac function was analyzed by serial echocardiography, in vivo pressure and isolated heart measurements. Cardiac output (CO) increased to 160 % of baseline at 10 h after sepsis induction followed by a decline to 63 % of baseline after 18 h in wildtype mice. CO was unaltered in septic NOS3(-/-) mice. Despite the hyperdynamic state, cardiac function and mean arterial pressure were impaired in septic wildtype as early as 6 h post CLP. At 12 h, cardiac function in septic wildtype was refractory to catecholamines in vivo and respective isolated hearts showed impaired pressure development and limited coronary flow reserve. Hemodynamics remained stable in NOS3(-/-) mice leading to significant survival benefit. Unselective NOS inhibition in septic NOS3(-/-) mice diminished this survival benefit. Plasma NO( x )- and local myocardial NO( x )- and NO levels (via NO spin trapping) demonstrated enhanced NO( x )- and bioactive NO levels in septic wildtype as compared to NOS3(-/-) mice. Significant contribution by inducible NOS (NOS2) during this early phase of sepsis was excluded. Our data suggest that NOS3 relevantly contributes to bioactive NO pool in developing sepsis resulting in impaired cardiac contractility.

Early course of microcirculatory perfusion in eye and digestive tract during hypodynamic sepsis

INTRODUCTION

The aim of the study was to evaluate and compare the microcirculatory perfusion during experimental sepsis in different potentially available parts of the body, such as sublingual mucosa, conjunctiva of the eye, and mucosa of jejunum and rectum.

METHODS

Pigs were randomly assigned to sepsis (n = 9) and sham (n = 4) groups. The sepsis group received a fixed dose of live Escherichia coli infusion over a 1-hour period (1.8 × 10(9)/kg colony-forming units). Animals were observed 5 hours after the start of E. coli infusion. In addition to systemic hemodynamic assessment, we performed conjunctival, sublingual, jejunal, and rectal evaluation of microcirculation by using Sidestream Dark Field (SDF) videomicroscopy at the same time points: at baseline, and at 3 and 5 hours after the start of live E. coli infusion. Assessment of microcirculatory parameters of convective oxygen transport (microvascular flow index (MFI) and proportion of perfused vessels (PPV)), and diffusion distance (perfused vessel density (PVD) and total vessel density (TVD)) was done by using a semiquantitative method.

RESULTS

Infusion of E. coli resulted in a hypodynamic state of sepsis associated with low cardiac output and increased systemic vascular resistance despite fluid administration. Significant decreases in MFI and PPV of small vessels were observed in sublingual, conjunctival, jejunal, and rectal locations 3 and 5 hours after the start of E. coli infusion in comparison with baseline variables. Correlation between sublingual and conjunctival (r = 0.80; P = 0.036), sublingual and jejunal (r = 0.80; P = 0.044), and sublingual and rectal (r = 0.79; P = 0.03) MFI was observed 3 hours after onset of sepsis. However, this strong correlation between the sublingual and other regions disappeared 5 hours after the start of E. coli infusion. Overall, the sublingual mucosa exhibited the most-pronounced alterations of microcirculatory flow in comparison with conjunctival, jejunal, and rectal microvasculature (P < 0.05).

CONCLUSIONS

In this pig model, a time-dependent correlation exists between sublingual and microvascular beds during the course of a hypodynamic state of sepsis.

Diastolic dysfunction and mortality in early severe sepsis and septic shock: a prospective, observational echocardiography study

Background

Patients with severe sepsis or septic shock often exhibit significant cardiovascular dysfunction. We sought to determine whether severity of diastolic dysfunction assessed by transthoracic echocardiography (TTE) predicts 28-day mortality.

Methods

In this prospective, observational study conducted in two intensive care units at a tertiary care hospital, 78 patients (age 53.2 ± 17.1 years; 51% females; mean APACHE II score 23.3 ± 7.4) with severe sepsis or septic shock underwent TTE within 6 h of ICU admission, after 18 to 32 h, and after resolution of shock. Left ventricular (LV) diastolic dysfunction was defined according to modified American Society of Echocardiography 2009 guidelines using E, A, and e’ velocities; E/A and E/e’; and E deceleration time. Systolic dysfunction was defined as an ejection fraction < 45%.

Results

Twenty-seven patients (36.5%) had diastolic dysfunction on initial echocardiogram, while 47 patients (61.8%) had diastolic dysfunction on at least one echocardiogram. Total mortality was 16.5%. The highest mortality (37.5%) was observed among patients with grade I diastolic dysfunction, an effect that persisted after controlling for age and APACHE II score. At time of initial TTE, central venous pressure (CVP) (11+/- 5 mmHg) did not differ among grades I-III, although patients with grade I received less intravenous fluid.

Conclusions

LV diastolic dysfunction is common in septic patients. Grade I diastolic dysfunction, but not grades II and III, was associated with increased mortality. This finding may reflect inadequate fluid resuscitation in early sepsis despite an elevated CVP, suggesting a possible role for TTE in sepsis resuscitation.

Thrombopoietin as biomarker and mediator of cardiovascular damage in critical diseases

Thrombopoietin (TPO) is a humoral growth factor originally identified for its ability to stimulate the proliferation and differentiation of megakaryocytes. In addition to its actions on thrombopoiesis, TPO directly modulates the homeostatic potential of mature platelets by influencing their response to several stimuli. In particular, TPO does not induce platelet aggregation per se but is able to enhance platelet aggregation in response to different agonists (“priming effect”). Our research group was actively involved, in the last years, in characterizing the effects of TPO in several human critical diseases. In particular, we found that TPO enhances platelet activation and monocyte-platelet interaction in patients with unstable angina, chronic cigarette smokers, and patients with burn injury and burn injury complicated with sepsis. Moreover, we showed that TPO negatively modulates myocardial contractility by stimulating its receptor c-Mpl on cardiomyocytes and the subsequent production of NO, and it mediates the cardiodepressant activity exerted in vitro by serum of septic shock patients by cooperating with TNF-α and IL-1β. This paper will summarize the most recent results obtained by our research group on the pathogenic role of elevated TPO levels in these diseases and discuss them together with other recently published important studies on this topic.

Matrix metalloproteinase-2 proteolysis of calponin-1 contributes to vascular hypocontractility in endotoxemic rats

OBJECTIVE

Matrix metalloproteinase (MMP)-2 is activated in aorta during endotoxemia and plays a role in the hypocontractility to vasoconstrictors. Calponin-1 is a regulator of vascular smooth muscle tone with similarities to troponin, a cardiac myocyte protein that is cleaved by MMP-2 in myocardial oxidative stress injuries. We hypothesized that calponin-1 may be proteolyzed by MMP-2 in endotoxemia-induced vascular hypocontractility.

METHODS AND RESULTS

Rats were given a nonlethal dose of bacterial lipopolysaccharide (LPS) or vehicle. Some rats were given the MMP inhibitors ONO-4817 or doxycycline. Six hours later, plasma nitrate+nitrite increased >15-fold in LPS-treated rats, an effect unchanged by doxycycline. Both ONO-4817 and doxycycline prevented LPS-induced aortic hypocontractility to phenylephrine. LPS activated MMP-2 in the aorta by S-glutathiolation. Calponin-1 levels decreased by 25% in endotoxemic aortae, which was prevented by doxycycline. Calponin-1 and MMP-2 coimmunoprecipitated and both exhibited uniform cytosolic staining in medial vascular smooth muscle cells. In vitro incubation of calponin-1 with MMP-2 led to calponin-1 degradation and appearance of its cleavage product.

CONCLUSION

Calponin-1 is a target of MMP-2, which contributes to endotoxemia-induced vascular hypocontractility.

Matrix metalloproteinase inhibitor properties of tetracyclines: therapeutic potential in cardiovascular diseases

Matrix metalloproteinases (MMPs) are a family of proteases best known for their capacity to proteolyse several proteins of the extracellular matrix. Their increased activity contributes to the pathogenesis of several cardiovascular diseases. MMP-2 in particular is now considered to be also an important intracellular protease which has the ability to proteolyse specific intracellular proteins in cardiac muscle cells and thus reduce contractile function. Accordingly, inhibition of MMPs is a growing therapeutic aim in the treatment or prevention of various cardiovascular diseases. Tetracyclines, especially doxycycline, have been frequently used as important MMP inhibitors since they inhibit MMP activity independently of their antimicrobial properties. In this review we will focus on the intracellular actions of MMPs in some cardiovascular diseases including ischemia and reperfusion (I/R) injury, inflammatory heart diseases and septic shock; and explain how tetracyclines, as MMP inhibitors, have therapeutic actions to treat such diseases. We will also briefly discuss how MMPs can be intracellularly regulated and activated by oxidative stress, thus cleaving several important proteins inside cells. In addition to their potential therapeutic effects, MMP inhibitors may also be useful tools to understand the biological consequences of MMP activity and its respective extra- and intracellular effects.

Thrombopoietin modulates cardiac contractility in vitro and contributes to myocardial depressing activity of septic shock serum

Thrombopoietin (TPO) is a humoral growth factor that has been shown to increase platelet activation in response to several agonists. Patients with sepsis have increased circulating TPO levels, which may enhance platelet activation, potentially participating to the pathogenesis of multi-organ failure. Aim of this study was to investigate whether TPO affects myocardial contractility and participates to depress cardiac function during sepsis. We showed the expression of the TPO receptor c-Mpl on myocardial cells and tissue by RT-PCR, immunofluorescence and western blotting. We then evaluated the effect of TPO on the contractile function of rat papillary muscle and isolated heart. TPO did not change myocardial contractility in basal conditions, but, when followed by epinephrine (EPI) stimulation, it blunted the enhancement of contractile force induced by EPI both in papillary muscle and isolated heart. An inhibitor of TPO prevented TPO effect on cardiac inotropy. Treatment of papillary muscle with pharmacological inhibitors of phosphatidylinositol 3-kinase, NO synthase, and guanilyl cyclase abolished TPO effect, indicating NO as the final mediator. We finally studied the role of TPO in the negative inotropic effect exerted by human septic shock (HSS) serum and TPO cooperation with TNF-alpha and IL-1beta. Pre-treatment with the TPO inhibitor prevented the decrease in contractile force induced by HSS serum. Moreover, TPO significantly amplified the negative inotropic effect induced by TNF-alpha and IL-1beta in papillary muscle. In conclusion, TPO negatively modulates cardiac inotropy in vitro and contributes to the myocardial depressing activity of septic shock serum.

Inhibition of matrix metalloproteinase activity in vivo protects against vascular hyporeactivity in endotoxemia

Persistent arterial hypotension is a hallmark of sepsis and is believed to be caused, at least in part, by excess nitric oxide (NO). NO can combine with superoxide to produce peroxynitrite, which activates matrix metalloproteinases (MMPs). Whether MMP inhibition in vivo protects against vascular hyporeactivity induced by endotoxemia is unknown. Male Sprague-Dawley rats were administered either bacterial lipopolysaccharide (LPS, 4 mg/kg ip) or vehicle (pyrogen-free water). Later (30 min), animals received the MMP inhibitor doxycycline (4 mg/kg ip) or vehicle (pyrogen-free water). After LPS injection (6 h), animals were killed, and aortas were excised. Aortic rings were mounted in organ baths, and contractile responses to phenylephrine or KCl were measured. Aortas and plasma were examined for MMP activity by gelatin zymography. Aortic MMP and inducible nitric oxide synthase (iNOS) were examined by immunoblot and/or immunohistochemistry. Doxycycline prevented the LPS-induced development of ex vivo vascular hyporeactivity to phenylephrine and KCl. iNOS protein was significantly upregulated in aortic homogenates from endotoxemic rats; doxycycline did not alter its level. MMP-9 activity was undetectable in aortic homogenates from LPS-treated rats but significantly upregulated in the plasma; this was attenuated by doxycycline. Plasma MMP-2 activities were unchanged by LPS. Specific MMP-2 activity was increased in aortas from LPS-treated rats. This study demonstrates the in vivo protective effect of the MMP inhibitor doxycycline against the development of vascular hyporeactivity in endotoxemic rats.

Sepsis and septic shock: a history

Infectious disease has been a leading cause of death in humans since the first recorded tabulations. From Hippocrates and Galen, to Lister, Fleming and Semmelweiss, this article reviews the notable historical figures of sepsis research. The early descriptions and theories about the etiology (microbial pathogens), pathogenesis (toxins and mediators), and treatment of sepsis-associated disease are also discussed.

The history and evolution of circulatory shock

This article reviews the development of early ideas regarding the origins and pathogenesis of shock. The early history of shock is related primarily to traumatic shock. More recent history centers on differentiation of clinical syndromes and individual characteristics. Definitions, classification systems, pathogenic theories, and treatments have evolved. Progress has been aided by constant development of improved assessment technologies. Today, shock is not a single syndrome and the definition of shock no longer is descriptive in nature. The most accepted current definition involves an oxygen supply/demand imbalance that can have various causes-hypovolemia, cardiac dysfunction, vascular failure, or obstructive processes.

sGC(alpha)1(beta)1 attenuates cardiac dysfunction and mortality in murine inflammatory shock models

Altered cGMP signaling has been implicated in myocardial depression, morbidity, and mortality associated with sepsis. Previous studies, using inhibitors of soluble guanylate cyclase (sGC), suggested that cGMP generated by sGC contributed to the cardiac dysfunction and mortality associated with sepsis. We used sGC(alpha)(1)-deficient (sGC(alpha)(1)(-/-)) mice to unequivocally determine the role of sGC(alpha)(1)beta(1) in the development of cardiac dysfunction and death associated with two models of inflammatory shock: endotoxin- and TNF-induced shock. At baseline, echocardiographic assessment and invasive hemodynamic measurements of left ventricular (LV) dimensions and function did not differ between wild-type (WT) mice and sGC(alpha)(1)(-/-) mice on the C57BL/6 background (sGC(alpha)(1)(-/-B6) mice). At 14 h after endotoxin challenge, cardiac dysfunction was more pronounced in sGC(alpha)(1)(-/-B6) than WT mice, as assessed using echocardiographic and hemodynamic indexes of LV function. Similarly, Ca(2+) handling and cell shortening were impaired to a greater extent in cardiomyocytes isolated from sGC(alpha)(1)(-/-B6) than WT mice after endotoxin challenge. Importantly, morbidity and mortality associated with inflammatory shock induced by endotoxin or TNF were increased in sGC(alpha)(1)(-/-B6) compared with WT mice. Together, these findings suggest that cGMP generated by sGC(alpha)(1)beta(1) protects against cardiac dysfunction and mortality in murine inflammatory shock models.

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.

Platelet-derived exosomes from septic shock patients induce myocardial dysfunction

Introduction

Mechanisms underlying inotropic failure in septic shock are incompletely understood. We previously identified the presence of exosomes in the plasma of septic shock patients. These exosomes are released mainly by platelets, produce superoxide, and induce apoptosis in vascular cells by a redox-dependent pathway. We hypothesized that circulating platelet-derived exosomes could contribute to inotropic dysfunction of sepsis.

Methods

We collected blood samples from 55 patients with septic shock and 12 healthy volunteers for exosome separation. Exosomes from septic patients and healthy individuals were investigated concerning their myocardial depressant effect in isolated heart and papillary muscle preparations.

Results

Exosomes from the plasma of septic patients significantly decreased positive and negative derivatives of left ventricular pressure in isolated rabbit hearts or developed tension and its first positive derivative in papillary muscles. Exosomes from healthy individuals decreased these variables non-significantly. In hearts from rabbits previously exposed to endotoxin, septic exosomes decreased positive and negative derivatives of ventricular pressure. This negative inotropic effect was fully reversible upon withdrawal of exosomes. Nitric oxide (NO) production from exosomes derived from septic shock patients was demonstrated by fluorescence. Also, there was an increase in myocardial nitrate content after exposure to septic exosomes.

Conclusion

Circulating platelet-derived exosomes from septic patients induced myocardial dysfunction in isolated heart and papillary muscle preparations, a phenomenon enhanced by previous in vivo exposure to lipopolysaccharide. The generation of NO by septic exosomes and the increased myocardial nitrate content after incubation with exosomes from septic patients suggest an NO-dependent mechanism that may contribute to myocardial dysfunction of sepsis.

Endothelial dependence of matrix metalloproteinase-mediated vascular hyporeactivity caused by lipopolysaccharide

Septic shock remains the leading cause of death in intensive care units in North America. Recent evidence implicates matrix metalloproteinases (MMP) in the pathogenesis of sepsis. MMP activity is upregulated in blood vessels exposed to bacterial lipopolysaccharide (LPS) or pro-inflammatory cytokines and contributes to vascular hyporeactivity to vasoconstrictors. The exact mechanism of MMP-mediated vascular hyporeactivity is unknown. We investigated the contribution of the endothelium in the MMP response to LPS-mediated vascular hyporeactivity in vitro. Tone induced by phenylephrine in isolated rat aortic rings with either intact or denuded endothelium was measured in the presence of LPS for 6 h. These rings were incubated with the nitric oxide (NO) synthase inhibitor, N(G)-nitro-l-arginine methyl ester (l-NAME), to determine whether NO synthase was involved in the response, or the MMP inhibitors, doxycycline or GM6001. MMP activity was measured after 6 h. LPS caused a greater reduction of phenylephrine-induced tone in endothelium-intact rings versus endothelium-denuded rings, indicating both endothelium-independent and -dependent mechanisms for LPS-induced vascular hyporeactivity. l-NAME abolished the response to LPS in both endothelium-intact and endothelium-denuded rings. MMP inhibitors prevented the LPS-induced loss of tone in endothelium-intact but not endothelium-denuded rings. LPS caused significantly greater MMP-2 activity in endothelium-intact aortae which was attenuated by doxycycline. MMP-2 activity in endothelium-denuded aortae was unchanged by LPS. The vascular endothelium contributes to MMP-mediated vascular dysfunction induced by LPS. The protective effect of MMP inhibition is endothelium-dependent and is a novel mechanism by which MMPs contribute to vascular dysfunction.

The effect of adrenomedullin on the L-type calcium current in myocytes from septic shock rats: signaling pathway

Adrenomedullin (ADM) is upregulated in cardiac tissue under various pathophysiological conditions, particularly in septic shock. The intracellular mechanisms involved in the effect of ADM on adult rat ventricular myocytes are still to be elucidated. Ventricular myocytes were isolated from adult rats 4 h after an intraperitoneal injection of lipopolysaccharide (LPS, 10 mg/kg). Membrane potential and L-type calcium current ( ICa,L) were determined using whole cell patch-clamp methods. APD in LPS group was significantly shorter than control values (time to 50% repolarization: LPS, 169 ± 2 ms; control, 257 ± 2 ms, P < 0.05; time to 90% repolarization: LPS, 220 ± 2 ms; control, 305 ± 2 ms, P < 0.05). ICa,Ldensity was significantly reduced in myocytes from the LPS group (−3.2 ± 0.8 pA/pF) compared with that of control myocytes (−6.7 ± 0.3 pA/pF, P < 0.05). The ADM antagonist ADM-(22-52) reversed the shortened APD and abolished the reduction of ICa,Lin shock myocytes. In myocytes from control rats, incubating with ADM for 1 h induced a marked decrease in peak ICa,Ldensity. This effect was reversed by ADM-(22-52). The Giprotein inhibitor, pertussis toxin (PTX), the protein kinase A (PKA) inhibitor, KT-5720, and the specific cyclooxygenase 2 (COX-2) inhibitor, nimesulide, reversed the LPS-induced reduction in peak ICa,L. The results suggest a COX-2-involved PKA-dependent switch from Gscoupled to PTX-sensitive Gicoupling by ADM in adult rat ventricular myocytes. The present study delineates the intracellular pathways involved in ADM-mediated effects on ICa,Lin adult rat ventricular myocytes and also suggests a role of ADM in sepsis.

The fetal inflammatory response syndrome

The fetal inflammatory response syndrome (FIRS) is a condition characterized by systemic inflammation and an elevation of fetal plasma interleukin-6. This syndrome has been observed in fetuses with preterm labor with intact membranes, preterm prelabor rupture of the membranes, and also fetal viral infections such as cytomegalovirus. FIRS is a risk factor for short-term perinatal morbidity and mortality after adjustment for gestational age at delivery and also for the development of long-term sequelae such as bronchopulmonary dysplasia and brain injury. Multiorgan involvement in FIRS has been demonstrated in the hematopoietic system, thymus, adrenal glands, skin, kidneys, heart, lung, and brain. This article reviews the fetal systemic inflammatory response as a mechanism of disease. Potential interventions to control an exaggerated inflammatory response in utero are also described.

Acute actions and novel targets of matrix metalloproteinases in the heart and vasculature

Matrix metalloproteinases (MMPs) have been shown to play significant roles in a number of physiological as well as pathological processes. Best known to proteolyse components of the extracellular matrix, MMPs have recently been discovered to also target a growing list of proteins apart from these, both inside and outside the cell. MMPs have also been traditionally thought of as enzymes involved in chronic processes such as angiogenesis, remodelling and atherosclerosis on a days-week time-scale. However they are now understood to also act acutely in response to oxidative stress on a minutes time-scale on non-extracellular matrix substrates. This review focuses on the acute actions and both extracellular and intracellular targets of two prominent MMP family members, MMP-2 and -9, in cardiovascular diseases including ischaemia/reperfusion injury, inflammatory heart disease, septic shock and pre-eclampsia. Also discussed are various ways of regulating MMP activity, including post-translational mechanisms, the endogenous tissue inhibitors of metalloproteinases and pharmacological inhibitors. A comprehensive understanding of MMP biology is necessary for the development of novel pharmacological therapies to combat the impact of cardiovascular disease.

Albumin resuscitation improves ventricular contractility and myocardial tissue oxygenation in rat endotoxemia

OBJECTIVE

Fluid resuscitation to improve delivery of oxygen to vital organs is a principal clinical intervention for septic patients. We previously reported that albumin resuscitation in rat endotoxemia improved contractility in isolated cardiomyocytes, but whether this effect occurs in vivo is unknown. We hypothesized that albumin resuscitation would improve decreased ventricular contractility and myocardial tissue oxygenation in vivo.

DESIGN

Randomized, controlled, prospective animal study.

SETTING

University animal laboratory.

SUBJECTS

Male Sprague-Dawley rats (250-350 g).

INTERVENTIONS

Rats were randomized into three groups: control with no lipopolysaccharide (n = 8), lipopolysaccharide (10 mg/kg) without albumin resuscitation (n = 8), and lipopolysaccharide with albumin resuscitation (n = 6). Five hours after lipopolysaccharide injection, animals were resuscitated with 10 mL/kg 5% rat albumin in 0.9% saline. Six hours after 10 mL/kg lipopolysaccharide, a pressure-volume conductance catheter (MIKRO-Tip 2.0-Fr, Millar Instruments, Houston, TX) was inserted into the left ventricle to quantify maximum elastance as an index of contractility. Myocardial tissue Po2 was measured using a fiberoptic oxygen probe.

MEASUREMENTS AND MAIN RESULTS

Maximum elastance decreased after lipopolysaccharide relative to control (47%, from 5.9 +/- 0.8 to 3.1 +/- 0.4 mm Hg/microL, p < .05). Albumin resuscitation prevented the lipopolysaccharide-induced decrease in maximum elastance (7.0 +/- 1.2 mm Hg/microL, p < .05 vs. lipopolysaccharide). Myocardial tissue Po2 was reduced in endotoxemia compared with control (53%, from 10.1 +/- 0.9 to 4.7 +/- 0.6 mm Hg, p < .05), and albumin resuscitation improved the lipopolysaccharide-induced tissue hypoxia toward the control value (9.0 +/- 1.4 mm Hg, p < .05).

CONCLUSIONS

Albumin resuscitation improved decreased ventricular contractility and myocardial oxygenation in endotoxemic rats. This result suggests that albumin resuscitation may improve ventricular dysfunction by improving myocardial hypoxia.

Toll-like receptor 2 activation by bacterial peptidoglycan-associated lipoprotein activates cardiomyocyte inflammation and contractile dysfunction

OBJECTIVE

Although cardiac dysfunction plays an important role in the pathogenesis of sepsis, the mechanisms that underlie cardiac dysfunction in sepsis remain poorly understood. Bacterial peptidoglycan-associated lipoprotein (PAL), an outer-membrane protein of Gram-negative bacteria, was recently found to be released into the bloodstream in sepsis and to cause inflammation and death in mice. The present studies assessed the effects of PAL on cardiomyocyte function and its signal transduction in cardiomyocytes.

DESIGN

Randomized prospective animal study.

SETTING

Research laboratory.

SUBJECTS

Male C57BL/6 mice, B6;129S-Tnfrsf1a(tm1Imx) Tnfrsf1b(tm1Imx)/J knockout mice, Toll-like receptor 2 (TLR2) knockout mice, and myeloid differentiation factor 88 (MyD88) knockout mice.

INTERVENTIONS

None.

MEASUREMENTS AND RESULTS

Immunohistochemical staining and immunoblot analysis indicated that intravenously injected PAL bound to myocardium. Injection of PAL decreased cardiac function in vivo. Challenge with PAL altered cell shortening and Ca2+ transients in isolated mouse cardiomyocytes but not in cardiomyocytes isolated from TLR2 -/- and MyD88 -/- mice. Cytokine profiling arrays demonstrated that tumor necrosis factor-alpha (TNFalpha), granulocyte colony-stimulating factor, and interferon-gamma-production were elevated in PAL-treated cardiomyocytes. Increased TNFalpha production was abolished in MyD88 -/- cardiomyocytes but restored by adenovirally mediated expression of MyD88. PAL did not affect cell shortening and Ca2+ cycling in cardiomyocytes obtained from mice deficient for TNFalpha receptor (TNFR) 1 and TNFR2 (TNFR1/2 -/-).

CONCLUSION

Our data reveal that PAL uses the TLR2/MyD88 signaling cascade to induce cardiomyocyte dysfunction and inflammatory responses and that TNFalpha is a major mediator of PAL-induced dysfunction in cardiomyocytes. These studies suggest that circulating PAL and other TLR2 agonists may contribute to cardiac dysfunction in sepsis.

Complement-related molecular events in sepsis leading to heart failure

Despite intensive ongoing research efforts, the mortality of patients with sepsis remains unacceptably high. A significant number of clinical trials have failed to produce sufficient therapeutic strategies despite showing promising results in animal models. So far, many studies have focused on deterioration of the humoral and cellular components of the immune system, the main cause of death in septic patients being multi-organ failure. However, not much is known about the effects of the complement system on parenchymal cells of organs such as the heart. Recently, septic cardiomyopathy has been recognized as one of the major complications during sepsis, often determining the clinical outcome. In this review, we describe molecular events which are thought to be related to cardiac dysfunction during sepsis. A special emphasis will be placed on the complement system, which generates powerful anaphylatoxins (such as C5a) and which has recently been associated with septic cardiomyopathy. Together with the impact on cardiac function of various cytokines we will provide a synopsis of the current knowledge regarding the pathophysiology underlying cardiac failure during sepsis with a special emphasis on C5a and C5aR.

The role of inflammation and infection in preterm birth

Inflammation has been implicated in the mechanisms responsible for preterm and term parturition, as well as fetal injury. Out of all of the suspected causes of preterm labor and delivery, infection and/or inflammation is the only pathological process for which both a firm causal link with preterm birth has been established and a molecular pathophysiology defined. Inflammation has also been implicated in the mechanism of spontaneous parturition at term. Most cases of histopathological inflammation and histological chorioamnionitis, both in preterm and term labor, are sub-clinical in nature. The isolation of bacteria in the amniotic fluid, known as microbial invasion of the amniotic cavity, is a pathological finding; the frequency of which is dependent upon the clinical presentation and gestational age. This article reviews the role of inflammation in preterm and term parturition.

Diagnostic accuracy of left ventricular function for identifying sepsis among emergency department patients with nontraumatic symptomatic undifferentiated hypotension

The hypothesis of this study states that in emergency department (ED) patients with non-traumatic symptomatic hypotension, the presence of hyperdynamic left ventricular function (LVF) is specific for sepsis as the etiology of shock. We performed a secondary analysis of patients with non-traumatic symptomatic hypotension enrolled in a randomized, clinical diagnostic trial. The study was done in an urban tertiary ED with a census over 100,000 visits per year. Inclusion criteria were non-trauma ED patients aged >17 years, initial vital signs consistent with shock (systolic blood pressure <100 mm Hg or shock index >1.0), and agreement of two independent observers for one sign and symptom of circulatory shock. All patients underwent focused ED echocardiography (echo) during initial resuscitation. Echos were reviewed post-hoc by a blinded physician and categorized by qualitative LVF as hyperdynamic (ejection fraction [EF] >55%), normal to moderate impairment (EF 30%-55%), and severe impairment (EF <30%). Main outcome was the criterion standard diagnosis of septic shock. Analyses include the diagnostic performance of LVF, Cohen's kappa for interobserver agreement of LVF, and logistic regression for independent predictors of sepsis. There were 103 echos that were adequate for analysis. The mean age was 57+/-16.7 years, 59% were male, and the mean initial systolic blood pressure was 83+/-11.3 mm Hg. A final diagnosis of septic shock was made in 38% (39/103) of patients. Seventeen of 103 (17%) patients had hyperdynamic LVF with an interobserver agreement of kappa=0.8. The sensitivity and specificity of hyperdynamic LVF for predicting sepsis were 33% (95% CI 19%-50%) and 94% (85%-98%), respectively. Hyperdynamic LVF had a positive likelihood ratio of 5.3 for the diagnosis of sepsis and was a strong independent predictor of sepsis as the final diagnosis with an odds ratio of 5.5 (95% CI 1.1-45). Among ED patients with non-traumatic undifferentiated symptomatic hypotension, the presence of hyperdynamic LVF on focused echo is highly specific for sepsis as the etiology of shock.

An essential role for complement C5a in the pathogenesis of septic cardiac dysfunction

Defective cardiac function during sepsis has been referred to as “cardiomyopathy of sepsis.” It is known that sepsis leads to intensive activation of the complement system. In the current study, cardiac function and cardiomyocyte contractility have been evaluated in rats after cecal ligation and puncture (CLP). Significant reductions in left ventricular pressures occurred in vivo and in cardiomyocyte contractility in vitro. These defects were prevented in CLP rats given blocking antibody to C5a. Both mRNA and protein for the C5a receptor (C5aR) were constitutively expressed on cardiomyocytes; both increased as a function of time after CLP. In vitro addition of recombinant rat C5a induced dramatic contractile dysfunction in both sham and CLP cardiomyocytes, but to a consistently greater degree in cells from CLP animals. These data suggest that CLP induces C5aR on cardiomyocytes and that in vivo generation of C5a causes C5a–C5aR interaction, causing dysfunction of cardiomyocytes, resulting in compromise of cardiac performance.

Increased leakage of sarcoplasmic reticulum Ca2+ contributes to abnormal myocyte Ca2+ handling and shortening in sepsis*

OBJECTIVE

Changes in cardiac function due to sepsis have been widely reported. However, the underlying mechanisms remain poorly understood. In the mammalian heart, myocyte function and intracellular calcium homeostasis are closely coupled. In this study we tested the hypothesis that alterations in cardiac calcium homeostasis due to sepsis underlie the observed myocyte dysfunction.

DESIGN

Randomized prospective animal study.

SETTING

Research laboratory.

SUBJECTS

Male Sprague-Dawley rats weighing 250-275 g.

INTERVENTIONS

We induced sepsis by cecal ligation and puncture in the rat, which mimics the type of infection caused by perforation of the intestine in humans.

MEASUREMENTS AND RESULTS

Forty-eight hours after cecal ligation and puncture, isolated cardiac ventricular cardiomyocytes demonstrated a 57% decreased peak systolic [Ca]. The time constant of the Ca transient increased 71% and 57% in myocytes obtained 24 hrs and 48 hrs after cecal ligation and puncture, respectively. The average shortening of cardiomyocytes 48 hrs after cecal ligation and puncture was significantly decreased. To investigate the cellular mechanisms of altered Ca transients and myocyte shortening, we measured Ca sparks, the spontaneous local Ca release events in cardiomyocytes at resting states. The Ca spark frequency progressively increased in myocytes 24 hrs and 48 hrs after cecal ligation and puncture. The total activity of sparks also increased compared with sham-operated animals. The overall leakage of sarcoplasmic reticulum Ca in resting states was increased in sepsis and resulted in reduced sarcoplasmic reticulum Ca content.

CONCLUSIONS

Abnormal Ca leakage from the sarcoplasmic reticulum contributes significantly to the depressed myocyte shortening in sepsis. In the future, modalities that prevent this Ca leakage may prove beneficial in the treatment of sepsis-induced myocyte shortening.

Bone marrow-derived cells contribute to contractile dysfunction in endotoxic shock

How infection precipitates depressed contractility is incompletely understood but may involve the immune, nervous, and endocrine systems as well as the heart itself. In this study, we examined the role of Toll-like receptor 4 (TLR4) in LPS-induced myocardial contractile depression. Eighteen hours following endotoxin challenge, we compared contractile responses in hearts from wild-type (WT) and TLR4-deficient mice using modified Langendorff preparations. Unlike hearts from WT mice, TLR4-deficient hearts did not reveal significant contractile dysfunction following LPS administration, as measured by decreased responses in maximal left ventricular pressure, +dP/d tmax, and −dP/d tmaxin ex vivo Langendorff preparations. These findings indicate a requirement for TLR4 in LPS-induced contractile depression. To determine the contribution of bone marrow-derived TLR4 function to LPS-induced myocardial dysfunction, we generated TLR4 chimeras using adoptive transfer between histocompatible mouse strains: either TLR4-deficient mice with TLR4+/+ bone marrow-derived cells or TLR4+/+ animals lacking TLR4 in their hematopoietic cells. We then compared the contractile responses of engrafted animals after LPS challenges. Engraftment of TLR4-deficient mice with WT marrow restored sensitivity to the myocardial depressant effects of LPS in TLR4-deficient hearts ( P < 0.05). Inactivation of bone marrow-derived TLR4 function, via transplantation of WT mice with TLR4−/− marrow, however, did not protect against the depressant effect of endotoxin. These findings indicate that bone marrow-derived TLR4 activity is sufficient to confer sensitivity to mice lacking TLR4 in all other tissues. However, because inactivation of marrow-derived TLR4 function alone does not protect against endotoxin-triggered contractile dysfunction, TLR4 function in other tissues may also contribute to this response.