Sympathetic overstimulation during critical illness: adverse effects of adrenergic stress

Impact of 5-HT₃ receptor antagonists on peripheral and central diseases

In this article we discuss the novel pharmacological aspects of 5-HT(3) receptor antagonists. Commonly used to counteract chemotherapy-induced emesis, these agents now appear to be reaching out for newer indications. Studies have reported neuroprotective and anti-inflammatory properties in vitro and in vivo. 5-HT(3) receptor antagonists can modulate the immune-inflammatory axis through blockade of 5-HT(3) receptors present on immune cells. We review evidence addressing the effects of these drugs on peripheral inflammatory diseases, including asthma, rheumatoid diseases, inflammatory bowel disease and sepsis in addition to diabetes and CNS disorders, including Alzheimer's disease (AD), seizure and stroke.

The neurological wake-up test increases stress hormone levels in patients with severe traumatic brain injury

OBJECTIVES

The "neurological wake-up test" is needed to evaluate the level of consciousness in patients with severe traumatic brain injury. However, the neurological wake-up test requires interruption of continuous sedation and may induce a stress response and its use in neurocritical care is controversial. We hypothesized that the neurological wake-up test induces an additional biochemical stress response in patients with severe traumatic brain injury.

PATIENTS

Twenty-four patients who received continuous propofol sedation and mechanical ventilation after moderate to severe traumatic brain injury (Glasgow Coma Scale score ≤ 8; patient age 18-71 yrs old) were analyzed. Exclusion criteria were age <18 yrs old, ongoing pentobarbital infusion, or markedly increased intracranial pressure on interruption of continuous sedation.

DESIGN

Single-center prospective study. During postinjury days 1-8, 65 neurological wake-up tests were evaluated. Adrenocorticotrophic hormone, epinephrine, and norepinephrine levels in plasma and cortisol levels in saliva were analyzed at baseline (during continuous intravenous propofol sedation) and during neurological wake-up test. Data are presented using medians and 25th and 75th percentiles.

SETTING

The study was performed in a university hospital neurocritical care unit.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

At baseline, adrenocorticotrophic hormone and cortisol levels were 10.6 (6.0-19.4) ng/L and 16.0 (10.7-31.8) nmol/L, respectively. Immediately after the neurological wake-up test, adrenocorticotrophic hormone levels increased to 20.5 (11.1-48.4) ng/L (p < .05) and cortisol levels in saliva increased to 24.0 (12.3-42.5) nmol/L (p < .05). The plasma epinephrine and norepinephrine levels increased from a baseline of 0.3 (0.3-0.6) and 1.6 (0.9-2.3) nmol/L, respectively, to 0.75 (0.3-1.4) and 2.8 (1.28-3.58) nmol/L, respectively (both p < .05).

CONCLUSIONS

The neurological wake-up test induces a biochemical stress response in patients with severe traumatic brain injury. The clinical importance of this stress response remains to be established but should be considered when deciding the frequency and use of the neurological wake-up test during neurocritical care.

Case report: successful lipid resuscitation in multi-drug overdose with predominant tricyclic antidepressant toxidrome

We report a case of profound neurologic and cardiovascular manifestations of tricyclic antidepressant intoxication following self-poisoning with multiple pharmaceuticals including amitriptyline in excess of 43 mg/kg, in a 51-year-old male. Institution of mechanical ventilation, volume expansion, systemic alkalinisation (pH 7.51), and intermittent bolus metaraminol resulted in QRS narrowing but failed to resolve the developed shock. One 100-ml bolus of 20% lipid emulsion followed by a further 400 ml over 30 min was administered with restoration of haemodynamic stability, thereby curtailing the need for ongoing vasopressor medications. Assayed blood levels were consistent with the 'lipid sink' being a major effecter in the observed improvement.

Synergistic induction of interleukin-6 expression by endothelin-1 and cyclic AMP in adipocytes

BACKGROUND

We have demonstrated previously that endothelin-1 (ET-1) may stimulate interleukin-6 (IL-6) release from 3T3-L1 adipocytes. In this study, we further examined the combined effect of ET-1 and cyclic adenosine monophosphate (cAMP) on IL-6 release.

METHODS

IL-6 release was measured by enzyme-linked immuosorbent assay. Reverse transcriptase-PCR and real-time PCR analyses were used to determine cellular mRNA levels. A luciferase reporter driven by promoter (-1310/+198) of mouse IL-6 gene was transfected into 3T3-L1 adipocytes to monitor IL-6 transcription.

RESULTS

ET-1 and cAMP induced IL-6 release in a synergistic manner that can be attributed to their synergistic induction of IL-6 gene expression, as evidenced by IL-6 mRNA analysis and the IL-6 promoter reporter assay. Both ET(A) and ET(B) receptors seem to be involved. In addition, enhanced IL-6 promoter activity can be similarly induced by ET-1 and catecholamines (epinephrine and norepinephrine). The cooperative interaction between ET-1 and cAMP on IL-6 expression seems distinctive, as no other proinflammatory cytokines, such as tumor necrosis factor-α (TNF-α) and IL-1β, are similarly affected. In fact, cAMP inhibited ET-1-stimulated TNF-α and IL-1β expressions in adipocytes. Furthermore, injection of mice with epinephrine and ET-1 induced a tremendously synergistic increase in serum IL-6 levels. Nevertheless, whereas cAMP induced IL-6 expression in RAW264.7 mouse macrophages, ET-1 had no effect on either the basal or the cAMP-induced IL-6 expression.

CONCLUSION

ET-1 and epinephrine may boost plasma IL-6 levels in mice in a synergistic manner, probably through their synergistic induction of IL-6 expression in adipocytes.

SIGNIFICANCE

This study should provide a new perspective for treating IL-6-related diseases, especially those accompanied with elevated ET-1 and catecholamine levels.

Effects of a peripheral cholinesterase inhibitor on cytokine production and autonomic nervous activity in a rat model of sepsis

PURPOSE

Recently, cholinergic anti-inflammatory pathway manipulation has been proposed as a new strategy to control cytokine production in sepsis. We investigated whether hypercytokinemia can be controlled via this pathway in an animal model of sepsis, with concomitant monitoring of autonomic nervous activity involving heart rate variability (HRV) analysis of electrocardiographic R-R intervals.

METHODS

Sixty-eight adult male Sprague-Dawley rats were used (28 for examination of cytokine production and autonomic nervous activity; 40 for survival analysis). Each part of the study involved four animal groups, including two control groups without drug administration. Sepsis was induced by cecal ligation and puncture (CLP). Distigmine bromide, a peripheral, non-selective cholinesterase inhibitor (0.01mg/kg), was administered subcutaneously 90 min after surgery. Continuous electrocardiograms were recorded for 5 min before and after surgery (at intervals of 5h) in CLP and sham-operated animals for HRV analysis. Blood samples were collected 20 h after surgery for serum cytokine and catecholamine assay.

RESULTS

On HRV analysis, distigmine inhibited reduction of total power and high-frequency components in CLP animals (P<0.05). Distigmine significantly inhibited cytokine induction (IL-6 and IL-10) (P<0.01) as well as increase in serum levels of noradrenaline and dopamine (P<0.05). Distigmine did not significantly improve CLP animal survival rate.

CONCLUSIONS

The cholinesterase inhibitor distigmine inhibited induction of inflammatory cytokines and catecholamines as well as HRV suppression in a rat CLP model, suggesting that an agent modulating the cholinergic anti-inflammatory pathway can control excess cytokine production involved in the pathogenesis of severe sepsis/septic shock.

Takotsubo Cardiomyopathy: Its Possible Impact during Adult Donor Care

Takotsubo cardiomyopathy, the syndrome caused by an extreme release and circulation of catecholamines, shares several histopathological and clinical similarities with cardiac changes after brain death noted in animal investigations and human observation. Overwhelming stimulation of myocardial inotropic β receptors may alter their responsiveness and induce other biochemical processes, producing reduced cardiac contractility. Treatment methods in Takotsubo cardiomyopathy that use extracorporeal circulatory support and medications that do not rely on β-receptor stimulation and preemptive blockade of β receptors or calcium channels before brain death may be relevant to donor care.

A high admission syndecan-1 level, a marker of endothelial glycocalyx degradation, is associated with inflammation, protein C depletion, fibrinolysis, and increased mortality in trauma patients

OBJECTIVE

To investigate the association between markers of acute endothelial glycocalyx degradation, inflammation, coagulopathy, and mortality after trauma.

BACKGROUND

Hyperinflammation and acute coagulopathy of trauma predict increased mortality. High catecholamine levels can directly damage the endothelium and may be associated with enhanced endothelial glycocalyx degradation, evidenced by high circulating syndecan-1.

METHODS

Prospective cohort study of trauma patients admitted to a Level 1 Trauma Centre in 2003 to 2005. Seventy-five patients were selected blindly post hoc from 3 predefined injury severity score (ISS) groups (<16, 16-27, >27). In all patients, we measured 17 markers of glycocalyx degradation, inflammation, tissue and endothelial damage, natural anticoagulation, and fibrinolysis (syndecan-1, IL-6, IL-10, histone-complexed DNA fragments, high-mobility group box 1 (HMGB1), thrombomodulin, von Willebrand factor, intercellular adhesion molecule-1, E-selectin, protein C, tissue factor pathway inhibitor (TFPI), antithrombin, D-dimer, tissue-type plasminogen activator (tPA), urokinase-type plasminogen activator (uPA), soluble uPA receptor, and plasminogen activator inhibitor-1), hematology, coagulation, catecholamines, and assessed 30-day mortality. Variables were compared in patients stratified according to syndecan-1 median.

RESULTS

Patients with high circulating syndecan-1 had higher catecholamines, IL-6, IL-10, histone-complexed DNA fragments, HMGB1, thrombomodulin, D-dimer, tPA, uPA (all P < 0.05), and 3-fold increased mortality (42% vs. 14%, P = 0.006) despite comparable ISS (P = 0.351). Only in patients with high glycocalyx degradation was higher ISS correlated with higher adrenaline, IL-6, histone-complexed DNA fragments, HMGB1, thrombomodulin, and APTT, lower protein C (all P < 0.05), unchanged TFPI and blunted D-dimer response (P < 0.001) because D-dimer was profoundly increased even at low ISS. After adjusting for age and ISS, syndecan-1 was an independent predictor of mortality (OR: 1.01 [95%CI, 1.00-1.02]; P = 0.043).

CONCLUSIONS

In trauma patients, high circulating syndecan-1, a marker of endothelial glycocalyx degradation, is associated with inflammation, coagulopathy and increased mortality.

Ethanol intoxication is associated with a lower incidence of admission coagulopathy in severe traumatic brain injury patients

The aim of this study was to determine the impact of ethanol (ETOH) on the incidence of severe traumatic brain injury (sTBI)-associated coagulopathy and to examine the effect of ETOH on in-hospital outcomes in patients sustaining sTBI. Patients admitted to the surgical intensive care unit from June 2005 through December 2008 following sTBI, defined as a head Abbreviated Injury Scale (AIS) score ≥3, were retrospectively identified. Patients with a chest, abdomen, or extremity AIS score >3 were excluded to minimize the impact of extracranial injuries. Criteria for sTBI-associated coagulopathy included thrombocytopenia and/or elevated International Normalized Ratio (INR) and/or prolonged activated partial thromboplastin time (aPTT). The incidence of admission coagulopathy, in-hospital complications, and mortality were compared between patients who were ETOH positive [ETOH (+)] and ETOH negative [ETOH (-)]. During the study period, there were 439 patients with ETOH levels available for analysis. Overall, 46.5% (n=204) of these patients were ETOH (+), while 53.5% (n=235) were ETOH (-). Coagulopathy was significantly less frequent in the ETOH (+) patients compared to their ETOH (-) counterparts (5.4% versus 15.3%; adjusted p<0.001). In the forward logistic regression analysis, a positive ETOH level proved to be an independent protective factor for admission coagulopathy [OR (95% CI)=0.24 (0.10,0.54; p=0.001]. ETOH (+) patients had a significantly lower in-hospital mortality rate than ETOH (-) patients [9.8% versus 16.6%; adjusted p=0.011; adjusted OR (95% CI)=0.39 (0.19,0.81)]. For brain-injured patients arriving alive to the hospital, ETOH intoxication is associated with a significantly lower incidence of early coagulopathy and in-hospital mortality. Further research to establish the pathophysiologic mechanisms underlying any potential beneficial effect of ETOH on the coagulation system following sTBI is warranted.

A physiological model for autonomic heart rate regulation in human endotoxemia

The systemic inflammatory response syndrome often accompanies critical illnesses and can be an important cause of morbidity and mortality. Marked abnormalities in cardiovascular function accompany acute illnesses manifested as sustained tachyarrhythmias, which are but one component of systemic dysregulation. The realization that cardiac pacemaker activity is under control of the autonomic nervous system has promoted the analysis of heart rate (HR) variation for assessing autonomic activities. In acute illnesses, autonomic imbalance manifesting in part as parasympathetic attenuation is associated with increased morbidity in patients who manifest systemic inflammatory response syndrome phenotype. Driven by the premise that biological phenotypes emerge as the outcome of the coordinated action of network elements across the host, a multiscale model of human endotoxemia, as a prototype model of systemic inflammation in humans, is developed that quantifies critical aspects of the complex relationship between inflammation and autonomic HR regulation. In the present study, changes in HR response to acute injury, phenotypically expressed as tachycardia, are simulated as a result of autonomic imbalance that reflects sympathetic activity excess and parasympathetic attenuation. The proposed model assesses both the anti-inflammatory and cardiovascular effects of antecedent stresses upon the systemic inflammatory manifestations of human endotoxemia as well as a series of nonlinear inflammatory relevant scenarios. Such a modeling approach provides a comprehensive conceptual framework linking inflammation and physiological complexity via a multiscale model that may advance the translational potential of systems modeling in clinical research.

Echocardiographic hemodynamic monitoring in the critically ill patient

Echocardiography has shown to be an essential diagnostic tool in the critically ill patient's assessment. In this scenario the initial fluid therapy, such as it is recommended in the actual clinical guidelines, not always provides the desired results and maintains a considerable incidence of cardiorrespiratory insufficiency. Echocardiography can council us on these patients' clinical handling, not only the initial fluid therapy but also on the best-suited election of the vasoactive/ inotropic treatment and the early detection of complications. It contributes as well to improving the etiological diagnosis, allowing one to know the heart performance with more precision. The objective of this manuscript is to review the more important parameters that can assist the intensivist in theragnosis of hemodynamically unstable patients.

Haematological changes at altitude

Hypobaric hypoxia is associated with an increase in erythropoesis and an increased thrombotic risk. This is true of long haul air travel, mountaineering expeditions and longer stays at altitude. Studies looking at clotting on mountaineering expeditions are further complicated by the effects of exercise, plasma volume changes and the catecholamine response to hypoxia. This review examines the evidence for changes in clotting factors and functional clotting at altitude and considers the implications of altitude travel for those with pre-existing medical conditions.

β-blockade protection of bone marrow following trauma: the role of G-CSF

BACKGROUND

Following severe trauma, there is a profound elevation of catecholamine that is associated with a persistent anemic state. We have previously shown that β-blockade (βB) prevents erythroid growth suppression and decreases hematopoietic progenitor cell (HPC) mobilization following injury. Under normal conditions, granulocyte colony stimulating factor (G-CSF) triggers the activation of matrix metalloprotease-9 (MMP-9), leading to the egress of progenitor cells from the bone marrow (BM). When sustained, this depletion of BM cellularity may contribute to BM failure. This study seeks to determine if G-CSF plays a role in the βB protection of BM following trauma.

METHODS

Male Sprague-Dawley rats were subjected to either unilateral lung contusion (LC) ± βB, hemorrhagic shock (HS) ± βB, or both LC/HS ± βB. Propranolol (βB) was given immediately following resuscitation. Animals were sacrificed at 3 and 24 h and HPC mobilization was assessed by evaluating BM cellularity and flow cytometric analysis of peripheral blood for HPCs. The concentration of G-CSF and MMP-9 was measured in plasma by ELISA.

RESULTS

BM cellularity is decreased at 3 h following LC, HS, and LC/HS. HS and LC/HS resulted in significant HPC mobilization in the peripheral blood. The addition of βB restored BM cellularity and reduced HPC mobilization. Three h following HS and LC/HS, plasma G-CSF levels more than double, however LC alone showed no change in G-CSF. βB significantly decreased G-CSF in both HS and LC/HS. Similarly, MMP-9 is elevated following LC/HS, and βB prevents this elevation (390 ± 100 pg/mL versus 275 ± 80 pg/mL).

CONCLUSION

βB protection of the BM following shock and injury may be due to reduced HPC mobilization and maintenance of BM cellularity. Following shock, there is an increase in plasma G-CSF and MMP-9, which is abrogated by βB and suggests a possible mechanism how βB decreases HPC mobilization thus preserving BM cellularity. In contrast, βB protection of BM following LC is not mediated by G-CSF. Therefore, the mechanism of progenitor cell mobilization from the BM is dependent on the type of injury.

Beta-block the septic heart

OBJECTIVES

Cardiac depression is a well-described manifestation of the sepsis syndrome. An important underlying mechanism is the attenuation of the adrenergic response at the cardiomyocyte level. By reducing their cell-specific function (contractility), the cardiomyocytes reduce their energy expenditure. Consequently, the cardiac myocytes survive in a hibernation-like state as long as intracellular energy generation is limited. The objective of this study was to review β-blocker therapy for the treatment of septic patients.

DATA SOURCE

MEDLINE database.

DATA SYNTHESIS

During established sepsis with organ failure, external adrenergic stimulation of the heart must be kept at a minimum. To blunt the adrenergic response, β-blockers have been used in several preclinical and clinical studies. In septic animals, β-blockers reduced heart rate, whereas stroke volume was maintained. Esmolol in vivo prevented the downregulation of adrenergic pathways, preserving full cardiac function ex vivo. In addition, β-blockers reduced the inflammatory response and the degree of lung injury. Some animal studies documented survival benefits, particularly when β-blockers were administered before the septic insult. In patients with septic shock, blood pressure increased and cardiac indices remained stable with metoprolol administration.

CONCLUSIONS

Preclinical and clinical studies with β-1 receptor blockers during sepsis show promising results. Future studies are needed to establish the optimal dose and timing of its administration.

Critical care "normality": individualized versus protocolized care

Patients with critical illness are heterogeneous, with differing physiologic requirements over time. Goal-directed therapy in the emergency room demonstrates that protocolized care could result in improved outcomes. Subsequent studies have confirmed benefit with such a "bundle-based approach" in the emergency room and in preoperative and postoperative scenarios. However, this cannot be necessarily extrapolated to the medium-term and long-term care pathway of the critically ill patient. It is likely that the development of mitochondrial dysfunction could result in goal-directed types of approaches being detrimental. Equally, arterial pressure aims are likely to be considerably different as the patient's physiology moves toward "hibernation." The agents we utilize as sedative and pressor agents have considerable effects on immune function and the inflammatory profile, and should be considered as part of the total clinical picture. The role of gut failure in driving inflammation is considerable, and the drive to feed enterally, regardless of aspirate volume, may be detrimental in those with degrees of ileus, which is often a difficult diagnosis in the critically ill. The pathogenesis of liver dysfunction may be, at least in part, related to venous engorgement that will contribute toward portal hypertension and gut edema. This, in association with loss of the hepatosplanchnic buffer response, it is likely to contribute to venous pooling in the abdominal cavity, impaired venous return, and decreased central blood volumes. Therapies such as those used in "small-for-size syndrome" may have a role in the chronic stages of septic vascular failure.

Ghrelin and its potential in the treatment of eating/wasting disorders and cachexia

The gastrointestinal "hunger" hormone ghrelin is the only known circulating peripheral molecule with the ability to decrease body fat utilization and to increase body weight gain. Accordingly, due to ghrelin's effects to promote food intake while decreasing energy expenditure ghrelin may offer potential as a drug for treatment of eating/wasting disorders and cachexia. Therapeutic potential of ghrelin and ghrelin analogues to promote food intake and body weight gain was recently indicated in several clinical studies. The recent discovery of the ghrelin O-acyltransferase as the key enzyme responsible for ghrelin acylation has further deepened our understanding of ghrelin activation, thereby paving the way for more efficient targeting of the ghrelin pathway. Here, we summarize the current knowledge pertaining to the potential of the endogenous ghrelin system as a drug target for the treatment of eating/wasting disorders and cachexia.

Thyroid hormone receptors are down-regulated in skeletal muscle of patients with non-thyroidal illness syndrome secondary to non-septic shock

AIM

Non-thyroidal illness syndrome (NTIS) is related to changes in thyroid hormone (TH) physiology. Skeletal muscle (SM) plays a major role in metabolism, and TH regulates SM phenotype and metabolism. We aimed to characterize the SM of non-septic shock NTIS patients in terms of: i) expression of genes and proteins involved in TH metabolism and actions; and ii) NFKB's pathway activation, a responsible factor for some of the phenotypic changes in NTIS. We also investigated whether the patient's serum can induce in vitro the effects observed in vivo.

METHODS

Serum samples and SM biopsies from 14 patients with non-septic shock NTIS and 11 controls. Gene and protein expression and NFKB1 activation were analyzed by quantitative PCR and immunoblotting. Human SM cell (HSkMC) cultures to investigate the effects of patient's serum on TH action mediators.

RESULTS

Patients with non-septic shock NTIS showed higher levels of pro-inflammatory cytokines than controls. Expression of TRβ (THRB), TRα1 (THRA), and retinoid X receptor γ (RXRG) was decreased in NTIS patients. RXRA gene expression was higher, but its protein was lower in NTIS than controls, suggesting the existence of a post-transcriptional mechanism that down-regulates protein levels. NFKB1 pathway activation was not different between NTIS and control patients. HSkMC incubated with patient's serum increased TH receptor and RXRG gene expression after 48  h.

CONCLUSIONS

Patients with non-septic shock NTIS showed decreased expression of TH receptors and RXRs, which were not related to increased activation of the NFKB1 pathway. These findings could not be replicated in cultures of HSkMCs incubated in the patient's serum.

Pulmonary vascular and right ventricular dysfunction in adult critical care: current and emerging options for management: a systematic literature review

INTRODUCTION

Pulmonary vascular dysfunction, pulmonary hypertension (PH), and resulting right ventricular (RV) failure occur in many critical illnesses and may be associated with a worse prognosis. PH and RV failure may be difficult to manage: principles include maintenance of appropriate RV preload, augmentation of RV function, and reduction of RV afterload by lowering pulmonary vascular resistance (PVR). We therefore provide a detailed update on the management of PH and RV failure in adult critical care.

METHODS

A systematic review was performed, based on a search of the literature from 1980 to 2010, by using prespecified search terms. Relevant studies were subjected to analysis based on the GRADE method.

RESULTS

Clinical studies of intensive care management of pulmonary vascular dysfunction were identified, describing volume therapy, vasopressors, sympathetic inotropes, inodilators, levosimendan, pulmonary vasodilators, and mechanical devices. The following GRADE recommendations (evidence level) are made in patients with pulmonary vascular dysfunction: 1) A weak recommendation (very-low-quality evidence) is made that close monitoring of the RV is advised as volume loading may worsen RV performance; 2) A weak recommendation (low-quality evidence) is made that low-dose norepinephrine is an effective pressor in these patients; and that 3) low-dose vasopressin may be useful to manage patients with resistant vasodilatory shock. 4) A weak recommendation (low-moderate quality evidence) is made that low-dose dobutamine improves RV function in pulmonary vascular dysfunction. 5) A strong recommendation (moderate-quality evidence) is made that phosphodiesterase type III inhibitors reduce PVR and improve RV function, although hypotension is frequent. 6) A weak recommendation (low-quality evidence) is made that levosimendan may be useful for short-term improvements in RV performance. 7) A strong recommendation (moderate-quality evidence) is made that pulmonary vasodilators reduce PVR and improve RV function, notably in pulmonary vascular dysfunction after cardiac surgery, and that the side-effect profile is reduced by using inhaled rather than systemic agents. 8) A weak recommendation (very-low-quality evidence) is made that mechanical therapies may be useful rescue therapies in some settings of pulmonary vascular dysfunction awaiting definitive therapy.

CONCLUSIONS

This systematic review highlights that although some recommendations can be made to guide the critical care management of pulmonary vascular and right ventricular dysfunction, within the limitations of this review and the GRADE methodology, the quality of the evidence base is generally low, and further high-quality research is needed.

Heart rate characteristics: physiomarkers for detection of late-onset neonatal sepsis

Early detection of late-onset neonatal sepsis, before the onset of obvious and potentially catastrophic clinical signs, is an important goal in neonatal medicine. Sepsis causes a well-known series of physiologic changes including abnormalities of blood pressure, respiration, temperature, and heart rate, and less well-known changes in heart rate variability. Although vital signs are frequently or continuously monitored in patients in the neonatal intensive care unit (NICU), changes in these parameters are subtle in the early phase of sepsis and difficult to interpret using traditional NICU monitoring tools. A new tool, continuous monitoring of heart rate characteristics (HRC), is now available for clinical use. Recent research has established that 2 abnormalities of HRC that have long been used by obstetricians to identify fetal compromise, reduced heart rate variability and transient decelerations, occur early in the course of sepsis in patients in the NICU, often before clinical signs of illness. Through mathematical modeling of electrocardiogram data from hundreds of patients in the NICU, an HRC index that represents the fold increase in risk that a neonate will be diagnosed with clinical or culture-proven sepsis within the next 24 hours was derived. The effect of continuous HRC monitoring on outcomes in preterm very low birth weight infants is the subject of a multicenter randomized clinical trial of 3000 patients, which will be complete in 2010. Further research into mechanisms of abnormal HRC and regulation of autonomic nervous system function in sepsis and other disease processes will shed light on additional applications of this exciting new technology.

Endotoxemia-induced inflammation and the effect on the human brain

INTRODUCTION

Effects of systemic inflammation on cerebral function are not clear, as both inflammation-induced encephalopathy as well as stress-hormone mediated alertness have been described.

METHODS

Experimental endotoxemia (2 ng/kg Escherichia coli lipopolysaccharide [LPS]) was induced in 15 subjects, whereas 10 served as controls. Cytokines (TNF-alpha, IL-6, IL1-RA and IL-10), cortisol, brain specific proteins (BSP), electroencephalography (EEG) and cognitive function tests (CFTs) were determined.

RESULTS

Following LPS infusion, circulating pro- and anti-inflammatory cytokines, and cortisol increased (P < 0.0001). BSP changes stayed within the normal range, in which neuron specific enolase (NSE) and S100-beta changed significantly. Except in one subject with a mild encephalopathic episode, without cognitive dysfunction, endotoxemia induced no clinically relevant EEG changes. Quantitative EEG analysis showed a higher state of alertness detected by changes in the central region, and peak frequency in the occipital region. Improved CFTs during endotoxemia was found to be due to a practice effect as CFTs improved to the same extent in the reference group. Cortisol significantly correlated with a higher state of alertness detected on the EEG. Increased IL-10 and the decreased NSE both correlated with improvement of working memory and with psychomotor speed capacity. No other significant correlations between cytokines, cortisol, EEG, CFT and BSP were found.

CONCLUSIONS

Short-term systemic inflammation does not provoke or explain the occurrence of septic encephalopathy, but primarily results in an inflammation-mediated increase in cortisol and alertness.

TRIAL REGISTRATION

NCT00513110.

Dose-response relationship between norepinephrine and erythropoiesis: evidence for a critical threshold

BACKGROUND

Severe traumatic injury elicits a neuroendocrine response that activates the sympathetic nervous system. Our previous work suggests that norepinephrine (NE) influences the bone marrow (BM) erythropoietic response. However, the dose-response relationship between NE and erythropoiesis remains unclear.

MATERIALS AND METHODS

Two days following chemical sympathectomy with 6-hydroxydopamine (6-OHDA) or injection with saline vehicle (SHAM), male Sprague-Dawley rats were infused continuously with either saline (NS) or increasing doses of NE for 5 d via osmotic pumps. Erythropoiesis was assessed by growth of erythroid progenitor colonies (BFU-E and CFU-E for early and late progenitors, respectively).

RESULTS

Following chemical sympathectomy with 6-OHDA, both BFU-E and CFU-E growth is inhibited (42%∗ and 43%∗ versus 100% SHAM, ∗P < 0.05). SHAM rats with continuous infusion of exogenous NE show a clear dose-response inhibition of both BFU-E and CFU-E colony growth. In the 6-OHDA rats, continuous infusion of NE restored BFU-E and CFU-E growth at 10(-8) g/h and 10(-9) g/h, respectively.

CONCLUSIONS

Erythroid precursor colony growth is inhibited in sympathectomized rats. In addition, supraphysiologic doses of exogenous NE inhibit normal erythropoiesis in a dose-dependent fashion. Following chemical sympathectomy with 6-OHDA, exogenous NE restores erythropoiesis in a narrow window. Therefore, NE has a complex interaction within the BM and the elevation of NE following traumatic injury impacts BM erythropoietic function.

Association of arterial blood pressure and vasopressor load with septic shock mortality: a post hoc analysis of a multicenter trial

Introduction

It is unclear to which level mean arterial blood pressure (MAP) should be increased during septic shock in order to improve outcome. In this study we investigated the association between MAP values of 70 mmHg or higher, vasopressor load, 28-day mortality and disease-related events in septic shock.

Methods

This is a post hoc analysis of data of the control group of a multicenter trial and includes 290 septic shock patients in whom a mean MAP ≥ 70 mmHg could be maintained during shock. Demographic and clinical data, MAP, vasopressor requirements during the shock period, disease-related events and 28-day mortality were documented. Logistic regression models adjusted for the geographic region of the study center, age, presence of chronic arterial hypertension, simplified acute physiology score (SAPS) II and the mean vasopressor load during the shock period was calculated to investigate the association between MAP or MAP quartiles ≥ 70 mmHg and mortality or the frequency and occurrence of disease-related events.

Results

There was no association between MAP or MAP quartiles and mortality or the occurrence of disease-related events. These associations were not influenced by age or pre-existent arterial hypertension (all P > 0.05). The mean vasopressor load was associated with mortality (relative risk (RR), 1.83; confidence interval (CI) 95%, 1.4-2.38; P < 0.001), the number of disease-related events (P < 0.001) and the occurrence of acute circulatory failure (RR, 1.64; CI 95%, 1.28-2.11; P < 0.001), metabolic acidosis (RR, 1.79; CI 95%, 1.38-2.32; P < 0.001), renal failure (RR, 1.49; CI 95%, 1.17-1.89; P = 0.001) and thrombocytopenia (RR, 1.33; CI 95%, 1.06-1.68; P = 0.01).

Conclusions

MAP levels of 70 mmHg or higher do not appear to be associated with improved survival in septic shock. Elevating MAP >70 mmHg by augmenting vasopressor dosages may increase mortality. Future trials are needed to identify the lowest acceptable MAP level to ensure tissue perfusion and avoid unnecessary high catecholamine infusions.

How to protect the heart in septic shock: a hypothesis on the pathophysiology and treatment of septic heart failure

Heart failure is a well-recognized manifestation of organ failure in sepsis and septic shock. The pathophysiology of septic heart failure is complex and currently believed to involve several mechanisms. So far, the contributory role of high plasma catecholamine levels has not been investigated. In this manuscript, we present a hypothesis suggesting that excessive catecholamine production and exogenous administration of catecholamines may relevantly contribute to the development of heart failure and cardiovascular collapse in patients suffering from septic shock. Substantially elevated plasma catecholamine levels were measured during critical illness and sepsis or septic shock. There is a growing body of clinical and experimental evidence demonstrating that high catecholamine plasma levels exert direct toxic effects on the heart. The pathophysiologic mechanisms involved in catecholamine-induced cardiomyocyte toxicity may involve a combination of inflammation, oxidative stress, and abnormal calcium handling resulting in myocardial stunning, apoptosis and necrosis. Clinical signs of catecholamine-induced heart failure can present with a wide range of symptoms reaching from subtle histological changes with preserved myocardial pump function to severe heart failure exhibiting a distinctive echocardiographic pattern which became known as "Takotsubo"-like cardiomyopathy or the left ventricular apical ballooning syndrome. In a medical intensive care unit patient population, presence of sepsis was the only variable associated with the development of left ventricular apical ballooning. Since several therapeutic interventions influence catecholamine plasma levels in septic shock patients, treatment strategies aiming at the reduction of endogenous or exogenous catecholamine exposure may protect the heart during septic shock and could facilitate patient survival.

Hemodynamic variables and mortality in cardiogenic shock: a retrospective cohort study

Introduction

Despite the key role of hemodynamic goals, there are few data addressing the question as to which hemodynamic variables are associated with outcome or should be targeted in cardiogenic shock patients. The aim of this study was to investigate the association between hemodynamic variables and cardiogenic shock mortality.

Methods

Medical records and the patient data management system of a multidisciplinary intensive care unit (ICU) were reviewed for patients admitted because of cardiogenic shock. In all patients, the hourly variable time integral of hemodynamic variables during the first 24 hours after ICU admission was calculated. If hemodynamic variables were associated with 28-day mortality, the hourly variable time integral of drops below clinically relevant threshold levels was computed. Regression models and receiver operator characteristic analyses were calculated. All statistical models were adjusted for age, admission year, mean catecholamine doses and the Simplified Acute Physiology Score II (excluding hemodynamic counts) in order to account for the influence of age, changes in therapies during the observation period, the severity of cardiovascular failure and the severity of the underlying disease on 28-day mortality.

Results

One-hundred and nineteen patients were included. Cardiac index (CI) (P = 0.01) and cardiac power index (CPI) (P = 0.03) were the only hemodynamic variables separately associated with mortality. The hourly time integral of CI drops <3, 2.75 (both P = 0.02) and 2.5 (P = 0.03) L/min/m² was associated with death but not that of CI drops <2 L/min/m² or lower thresholds (all P > 0.05). The hourly time integral of CPI drops <0.5-0.8 W/m² (all P = 0.04) was associated with 28-day mortality but not that of CPI drops <0.4 W/m² or lower thresholds (all P > 0.05).

Conclusions

During the first 24 hours after intensive care unit admission, CI and CPI are the most important hemodynamic variables separately associated with 28-day mortality in patients with cardiogenic shock. A CI of 3 L/min/m² and a CPI of 0.8 W/m² were most predictive of 28-day mortality. Since our results must be considered hypothesis-generating, randomized controlled trials are required to evaluate whether targeting these levels as early resuscitation endpoints can improve mortality in cardiogenic shock.

Comparing two different arginine vasopressin doses in advanced vasodilatory shock: a randomized, controlled, open-label trial

PURPOSE

To compare the effects of two arginine vasopressin (AVP) dose regimens on the hemodynamic response, catecholamine requirements, AVP plasma concentrations, organ function and adverse events in advanced vasodilatory shock.

METHODS

In this prospective, controlled, open-label trial, patients with vasodilatory shock due to sepsis, systemic inflammatory response syndrome or after cardiac surgery requiring norepinephrine >0.6 microg/kg/min were randomized to receive a supplementary AVP infusion either at 0.033 IU/min (n = 25) or 0.067 IU/min (n = 25). The hemodynamic response, catecholamine doses, laboratory and organ function variables as well as adverse events (decrease in cardiac index or platelet count, increase in liver enzymes or bilirubin) were recorded before, 1, 12, 24 and 48 h after randomization. A linear mixed effects model was used for statistical analysis in order to account for drop-outs during the observation period.

RESULTS

Heart rate and norepinephrine requirements decreased while MAP increased in both groups. Patients receiving AVP at 0.067 IU/min required less norepinephrine (P = 0.006) than those infused with AVP at 0.033 IU/min. Arterial lactate and base deficit decreased while arterial pH increased in both groups. During the observation period, AVP plasma levels increased in both groups (both P < 0.001), but were higher in the 0.067 IU/min group (P < 0.001) and in patients on concomitant hydrocortisone. The rate of adverse events and intensive care unit mortality was comparable between groups (0.033 IU/min, 52%; 0.067 IU/min, 52%; P = 1).

CONCLUSIONS

A supplementary AVP infusion of 0.067 IU/min restores cardiovascular function in patients with advanced vasodilatory shock more effectively than AVP at 0.033 IU/min.