Autonomic dysfunction predicts both 1- and 2-month mortality in middle-aged patients with multiple organ dysfunction syndrome

Guideline for the application of heart rate and heart rate variability in occupational medicine and occupational health science

This updated guideline replaces the "Guideline for the application of heart rate and heart rate variability in occupational medicine and occupational health science" first published in 2014. Based on the older version of the guideline, the authors have reviewed and evaluated the findings on the use of heart rate (HR) and heart rate variability (HRV) that have been published in the meantime and incorporated them into a new version of this guideline.This guideline was developed for application in clinical practice and research purposes in the fields of occupational medicine and occupational science to complement evaluation procedures with respect to exposure and risk assessment at the workplace by the use of objective physiological workload indicators. In addition, HRV is also suitable for assessing the state of health and for monitoring the progress of illnesses and preventive medical measures. It gives an overview of factors influencing the regulation of the HR and HRV at rest and during work. It further illustrates methods for measuring and analyzing these parameters under standardized laboratory and real workload conditions, areas of application as well as the quality control procedures to be followed during the recording and evaluation of HR and HRV.

Heart rate variability as a marker and predictor of inflammation, nosocomial infection, and sepsis - A systematic review

PURPOSE

The autonomic nervous system interacts with the immune system via the inflammatory response. Heart rate variability (HRV), a marker of autonomic activity, is associated with inflammation, and nosocomial infections/sepsis, and has clinical implications for the monitoring of at-risk patients. Due to the vagal tone's influence on anti-inflammatory immune response, this association may predominately be reflected by vagally-mediated HRV indices. However, HRV's predictive significance on inflammation/infection remains unclear.

METHODS

843 studies examining the associations/prognostic value of HRV indices on inflammation, and nosocomial infection/sepsis were screened in this systematic review. According to inclusion and exclusion criteria, 68 associative studies and 14 prediction studies were included.

RESULTS

HRV and pro-inflammatory state were consistently associated in healthy subjects and patient groups. Pro-inflammatory state was related to reduced total power HRV including vagally- and non-vagally-mediated HRV indices. Similar, compared to controls, HRV reductions were observed during nosocomial infections/sepsis. Only limited evidence supports the predictive value of HRV in the development of nosocomial infections/sepsis. Reduced very low frequency power HRV showed the highest predictive value in adults, even with different clinical conditions. In neonates, an increased heart rate characteristic score, combining reduced total power HRV, decreased complexity, and vagally-dominated asymmetry, predicted sepsis.

CONCLUSIONS

Pro-inflammatory state is related to an overall reduction in HRV rather than a singular reduction in vagally-mediated HRV indices, reflecting the complex autonomic-regulatory changes occurring during inflammation. The potential benefit of using continuous HRV monitoring for detecting nosocomial infection-related states, and the implications for clinical outcome, need further clarification.

HEART RATE VARIABILITY PARAMETERS WERE NOT ASSOCIATED WITH 30-DAY ALL-CAUSE MORTALITY IN INTENSIVE CARE UNIT PATIENTS WITH OR WITHOUT ATRIAL FIBRILLATION: A RETROSPECTIVE STUDY OF THE MIMIC-IV DATABASE

ABSTRACT

Objective: Our study aims to evaluate the association between heart rate variability (HRV) and short- and long-term prognosis in patients admitted to intensive care unit (ICU). Methods and Results: Adult patients continuously monitored for over 24 h in ICUs from the the American Medical Information Mart for Intensive Care (MIMIC)-IV Waveform Database were recruited in our study. Twenty HRV-related variables (8 time domain, 6 frequency domain, and 6 nonlinear variables) were calculated based on RR intervals. The association between HRV and all-cause mortality was assessed. Ninety-three patients met the inclusion criteria and were classified into atrial fibrillation (AF) and sinus rhythm (SR) groups, which were further divided into 30-day survivor group and nonsurvivor\groups based on their survival status. The 30-day all-cause mortality rates in AF and SR groups were 36.3% and 14.6%, respectively. All the time domain, frequency domain, and nonlinear HRV parameters did not differ significantly between survivors and nonsurvivors with or without AF (all P > 0.05). Presence of renal failure, malignancy, and elevated blood urea nitrogen level were associated with increased 30-day all-cause mortality in SR patients, while presence of sepsis, infection, higher platelet count, and magnesium level were associated with increased 30-day all-cause mortality in AF patients. Conclusions: Heart rate variability variables were not associated with increased 30-day all-cause mortality in ICU patients with or without AF.

Ageing and the Autonomic Nervous System

The vertebrate nervous system is divided into central (CNS) and peripheral (PNS) components. In turn, the PNS is divided into the autonomic (ANS) and enteric (ENS) nervous systems. Ageing implicates time-related changes to anatomy and physiology in reducing organismal fitness. In the case of the CNS, there exists substantial experimental evidence of the effects of age on individual neuronal and glial function. Although many such changes have yet to be experimentally observed in the PNS, there is considerable evidence of the role of ageing in the decline of ANS function over time. As such, this chapter will argue that the ANS constitutes a paradigm for the physiological consequences of ageing, as well as for their clinical implications.

Association of onset time of new-onset atrial fibrillation with in-hospital mortality among critically ill patients: A secondary analysis of a prospective multicenter observational study

Background

New-onset atrial fibrillation (AF) in critically ill patients is associated with adverse outcomes. In non-critical settings, the circadian variation in paroxysmal AF is of significant interest; however, circadian variation in critically ill patients with new-onset AF has not been thoroughly studied. This study aimed to examine the association between AF onset time and in-hospital mortality.

Methods

This was a secondary analysis of a prospective multicenter observational study enrolling adult critically ill patients. According to AF onset time, patients were divided into nighttime (0:00–7:59), daytime (8:00–15:59), and evening (16:00–23:59). We conducted a multiple logistic regression analysis to assess the potential association between AF onset time and in-hospital mortality. We also assessed the distribution of AF onset, crude in-hospital mortality, and adjusted in-hospital mortality according to bihourly intervals.

Results

Of 423 patients, in-hospital mortality was 26%. During nighttime, 135 patients (32%) developed new-onset AF. AF emerged during daytime for 141 (33%) and during evening for 147 (35%). Daytime AF was significantly associated with an increased risk of in-hospital mortality (adjusted OR: 1.92; 95% CI: 1.07–3.44; p = 0.030). Bihourly interval analysis showed that adjusted in-hospital mortality was unevenly distributed and bimodal with troughs between 6:00 and 7:59 and between 18:00 and 19:59. A similar trend was seen in the distribution of the number of new-onset AF.

Conclusions

We found that the bihourly adjusted in-hospital mortality was distributed in a bimodal fashion. Further research is needed to determine the causes of the diurnal variation and its impact on patient outcomes.

Survivors of Intensive Care With Type 2 Diabetes and the Effect of Shared-Care Follow-Up Clinics: The SWEET-AS Randomized Controlled Pilot Study

BACKGROUND

Follow-up clinics after ICU admission have demonstrated limited benefit. However, existing trials have evaluated heterogeneous cohorts and used physicians who had limited training in outpatient care.

RESEARCH QUESTION

What are the effects of a "shared-care" intensivist-endocrinologist clinic for ICU survivors with type 2 diabetes on process measures and clinical outcomes 6 months after hospital discharge, and is it feasible to conduct a larger trial?

STUDY DESIGN AND METHODS

This was a prospective, randomized, single-center pilot study with blinded outcome assessment. Patients with type 2 diabetes, who required ≥ 5 days of ICU care (mixed medical-surgical ICU) and survived to ICU discharge, were eligible. Participants were randomized to attendance at the shared-care clinic 1 month after hospital discharge or usual care. Six months after hospital discharge, participants were assessed for outcomes including glycated hemoglobin, neuropathy, nephropathy, quality of life, return to employment, frailty, and health-care use. The primary outcome was participant recruitment and retention.

RESULTS

During an 18-month period, 42 of 82 eligible patients (51%) were recruited. Four participants (10%) withdrew before assessment at 6 months and 11 (26%) died. At 6 months, only 18 of 38 participants who did not withdraw (47%) were living independently without support, and 24 (63%) required at least one subsequent hospital admission. In the intervention group (n = 21), 16 (76%) attended the clinic. Point estimates did not indicate that the intervention improved glycated hemoglobin (+5.6 mmol/mol; 95% CI, -6.3 to 17; P = .36) or quality of life (36-Item Short Form Survey physical summary score, 32 [9] vs. 32 [7]; P = 1.0).

INTERPRETATION

Outcomes for ICU survivors with type 2 diabetes are poor. Because of low participation and high mortality, a larger trial of a shared-care follow-up clinic in this cohort, using the present design, does not appear feasible.

TRIAL REGISTRY

Australian New Zealand Clinical Trials Registry (ANZCTR); No.: ACTRN12616000206426; URL: www.anzctr.org.au.

Identification of cardiovascular and molecular prognostic factors for the medium-term and long-term outcomes of sepsis (ICROS): protocol for a prospective monocentric cohort study

INTRODUCTION

Sepsis is one of the most prevalent life-threatening conditions in the intensive care unit. Patients suffer from impaired organ function, reduced physical functional capacity and decreased quality of life even after surviving sepsis. The identification of prognostic factors for the medium-term and long-term outcomes of this condition is necessary to develop personalised theragnostic approaches. Sepsis can cause cardiac impairment. The impact of this septic cardiomyopathy on patient's long-term outcome remains unclear. This study aims to evaluate cardiovascular risk factors, particularly the occurrence of septic cardiomyopathy, regarding their suitability as prognostic factors for the short-term and long-term outcomes of septic patients. Additionally, the study seeks to validate preclinical pathophysiological findings of septic cardiomyopathy in the clinical setting.

METHODS AND ANALYSIS

In this prospective monocentric cohort study, patients will be clinically assessed during the acute and postacute phase of sepsis and two follow-ups after 6 and 12 months. To determine the effect of septic cardiomyopathy and concomitant cellular and molecular changes on patient mortality and morbidity, a comprehensive cardiovascular and molecular deep phenotyping of patients will be performed. This includes an echocardiographic and electrocardiographic assessment, and the evaluation of heart rate variability, body composition, mitochondrial oxygen metabolism, macrocirculation and microcirculation, and endothelial barrier function. These analyses are complemented by routine immunological, haematological and biochemical laboratory tests and analyses of the serum metabolome and lipidome, microbiome and epigenetic modifications of immune cells. The reversibility of patients' organ dysfunction, their quality of life and physical functional capacity will be investigated in the follow-ups. Patients with cardiomyopathy without infection and healthy subjects will serve as control groups.

ETHICS AND DISSEMINATION

Approval was obtained from the Ethics Committee of the Friedrich Schiller University Jena (5276-09/17). The results will be published in peer-reviewed journals and presented at appropriate conferences.

TRIAL REGISTRATION NUMBERS

DRKS00013347; NCT03620409.

Heart rate variability: Measurement and emerging use in critical care medicine

Variation in the time interval between consecutive R wave peaks of the QRS complex has long been recognised. Measurement of this RR interval is used to derive heart rate variability. Heart rate variability is thought to reflect modulation of automaticity of the sinus node by the sympathetic and parasympathetic components of the autonomic nervous system. The clinical application of heart rate variability in determining prognosis post myocardial infarction and the risk of sudden cardiac death is well recognised. More recently, analysis of heart rate variability has found utility in predicting foetal deterioration, deterioration due to sepsis and impending multiorgan dysfunction syndrome in critically unwell adults. Moreover, reductions in heart rate variability have been associated with increased mortality in patients admitted to the intensive care unit. It is hypothesised that heart rate variability reflects and quantifies the neural regulation of organ systems such as the cardiovascular and respiratory systems. In disease states, it is thought that there is an 'uncoupling' of organ systems, leading to alterations in 'inter-organ communication' and a clinically detectable reduction in heart rate variability. Despite the increasing evidence of the utility of measuring heart rate variability, there remains debate as to the methodology that best represents clinically relevant outcomes. With continuing advances in technology, our understanding of the physiology responsible for heart rate variability evolves. In this article, we review the current understanding of the physiological basis of heart rate variability and the methods available for its measurement. Finally, we review the emerging use of heart rate variability analysis in intensive care medicine and conditions in which heart rate variability has shown promise as a potential physiomarker of disease.

Autonomic nervous system monitoring in intensive care as a prognostic tool. Systematic review

Objective

To present a systematic review of the use of autonomic nervous system monitoring as a prognostic tool in intensive care units by assessing heart rate variability.

Methods

Literature review of studies published until July 2016 listed in PubMed/Medline and conducted in intensive care units, on autonomic nervous system monitoring, via analysis of heart rate variability as a prognostic tool (mortality study). The following English terms were entered in the search field: ("autonomic nervous system" OR "heart rate variability") AND ("intensive care" OR "critical care" OR "emergency care" OR "ICU") AND ("prognosis" OR "prognoses" OR "mortality").

Results

There was an increased likelihood of death in patients who had a decrease in heart rate variability as analyzed via heart rate variance, cardiac uncoupling, heart rate volatility, integer heart rate variability, standard deviation of NN intervals, root mean square of successive differences, total power, low frequency, very low frequency, low frequency/high frequency ratio, ratio of short-term to long-term fractal exponents, Shannon entropy, multiscale entropy and approximate entropy.

Conclusion

In patients admitted to intensive care units, regardless of the pathology, heart rate variability varies inversely with clinical severity and prognosis.

Continuous blood purification ameliorates clinical signs and corrects the plasma phospholipid levels of patients with multiple organ dysfunction syndromes

BACKGROUND

Multiple organ dysfunction syndromes (MODS) is reported as a leading cause of mortality in intensive care units. Recently, continuous blood purification (CBP) has been mostly applied for MODS treatment. Thus, the purpose of this study was to investigate the effects of CBP on plasma phospholipid level in patients with MODS.

METHODS

A total of 126 patients with MODS and 120 healthy people were collected. The serum cytokine levels, blood biochemical parameters, and blood gas indexes were detected, and the correlation among phospholipid compounds with serum cytokine levels, blood biochemical parameters, and blood gas indexes was analyzed.

RESULTS

Before CBP, levels of body temperature, RR, HR, CVP, IL-6, IL-10, TNF-α, BUN, SCr, PaCO₂ , SM747, and LPC540 were obviously higher, and pH, HCO_3- , PaO₂ , SaO₂ , PE750, PI885, PC792, PC826, PC830, PC854, PC802, and PG747 were lower in the MODS group than those in the control group. During CBP, the MODS group had gradually declined RR, CVP, levels of IL-6, IL-10 and TNF-α, BUN, SCr, PaCO₂ , SM747, and LPC540 and increased HCO_3- , PaO₂ and SaO₂ , PE750, PI885, PC792, PC826, PC830, PC854, PC802, and PG747. Besides, levels of PE750, PI885, PC792, PC826, PC830, PC854, PC802, and PG747 had an obvious negative correlation with levels of TNF-α, IL-10, IL-6, BUN, SCr, and PaCO₂ , and a significant positive correlation with levels of HCO_3- , PaO₂ , and SaO₂ .

CONCLUSION

CBP could effectively ameliorate clinical signs of patients with MODS and correct the plasma phospholipid levels.

Association between autonomic control indexes and mortality in subjects admitted to intensive care unit

This study checks whether autonomic markers derived from spontaneous fluctuations of heart period (HP) and systolic arterial pressure (SAP) and from their interactions with spontaneous or mechanical respiration (R) are associated with mortality in patients admitted to intensive care unit (ICU). Three-hundred consecutive HP, SAP and R values were recorded during the first day in ICU in 123 patients. Population was divided into survivors (SURVs, n = 83) and non-survivors (NonSURVs, n = 40) according to the outcome. SURVs and NonSURVs were aged- and gender-matched. All subjects underwent modified head-up tilt (MHUT) by tilting the bed back rest segment to 60°. Autonomic control indexes were computed using time-domain, spectral, cross-spectral, complexity, symbolic and causality techniques via univariate, bivariate and conditional approaches. SAP indexes derived from time-domain, model-free complexity and symbolic approaches were associated with the endpoint, while none of HP variability markers was. The association was more powerful during MHUT. Linear cross-spectral and causality indexes were useless to separate SURVs from NonSURVs, while nonlinear bivariate symbolic markers were successful. When indexes were combined with clinical scores, only SAP variance provided complementary information. Cardiovascular control variability indexes, especially when derived after an autonomic challenge such as MHUT, can improve mortality risk stratification in ICU.

Pathophysiology of the cardio-renal syndromes types 1-5: An uptodate

According to the recent definition proposed by the Consensus conference on Acute Dialysis Quality Initiative Group, the term cardio-renal syndrome (CRS) has been used to define different clinical conditions in which heart and kidney dysfunction overlap. Type 1 CRS (acute cardio- renal syndrome) is characterized by acute worsening of cardiac function leading to AKI (5, 6) in the setting of active cardiac disease such as ADHF, while type - 2 CRS occurs in a setting of chronic heart disease. Type 3 CRS is closely link to acute kidney injury (AKI), while type 4 represent cardiovascular involvement in chronic kidney disese (CKD) patients. Type 5 CRS represent cardiac and renal involvement in several diseases such as sepsis, hepato - renal syndrome and immune - mediated diseases.

The impairment of small nerve fibers in severe sepsis and septic shock

Background

A decrease of small nerve fibers in skin biopsies during the course of critical illness has been demonstrated recently. However, the diagnostic use of skin biopsies in sepsis and its time course is not known.

Methods

Patients (n=32) with severe sepsis or septic shock were examined using skin biopsies, neurological examination, nerve conduction studies, and sympathetic skin response in the first week after onset of sepsis, 2 weeks and 4 months later and compared to gender- and age-matched healthy controls.

Results

Skin biopsies at the ankle and thigh revealed a significant decrease of intraepidermal nerve fiber density (IENFD) during the first week of sepsis and 2 weeks later. All patients developed critical illness polyneuropathy (CIP) according to electrophysiological criteria and 11 showed IENFD values lower than the 0.05 quantile. Four patients were biopsied after 4 months and still showed decreased IENFD. Results of nerve conduction studies and IENFD did considerably change over time. No differences for survival time between patients with IEFND lower and larger than 3.5 fibers/mm were found.

Conclusions

Skin biopsy is able to detect an impairment of small sensory nerve fibers early in the course of sepsis. However, it may not be suited as a prognostic parameter for survival.

Trial registration

German Clinical Trials Register, DRKS-ID: DRKS00000642, 12/17/2010

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-016-1241-5) contains supplementary material, which is available to authorized users.

Survivors of intensive care with type 2 diabetes and the effect of shared care follow-up clinics: study protocol for the SWEET-AS randomised controlled feasibility study

BACKGROUND

Many patients who survive the intensive care unit (ICU) experience long-term complications such as peripheral neuropathy and nephropathy which represent a major source of morbidity and affect quality of life adversely. Similar pathophysiological processes occur frequently in ambulant patients with diabetes mellitus who have never been critically ill. Some 25 % of all adult ICU patients have diabetes, and it is plausible that ICU survivors with co-existing diabetes are at heightened risk of sequelae from their critical illness. ICU follow-up clinics are being progressively implemented based on the concept that interventions provided in these clinics will alleviate the burdens of survivorship. However, there is only limited information about their outcomes. The few existing studies have utilised the expertise of healthcare professionals primarily trained in intensive care and evaluated heterogenous cohorts. A shared care model with an intensivist- and diabetologist-led clinic for ICU survivors with type 2 diabetes represents a novel targeted approach that has not been evaluated previously. Prior to undertaking any definitive study, it is essential to establish the feasibility of this intervention.

METHODS

This will be a prospective, randomised, parallel, open-label feasibility study. Eligible patients will be approached before ICU discharge and randomised to the intervention (attending a shared care follow-up clinic 1 month after hospital discharge) or standard care. At each clinic visit, patients will be assessed independently by both an intensivist and a diabetologist who will provide screening and targeted interventions. Six months after discharge, all patients will be assessed by blinded assessors for glycated haemoglobin, peripheral neuropathy, cardiovascular autonomic neuropathy, nephropathy, quality of life, frailty, employment and healthcare utilisation. The primary outcome of this study will be the recruitment and retention at 6 months of all eligible patients.

DISCUSSION

This study will provide preliminary data about the potential effects of critical illness on chronic glucose metabolism, the prevalence of microvascular complications, and the impact on healthcare utilisation and quality of life in intensive care survivors with type 2 diabetes. If feasibility is established and point estimates are indicative of benefit, funding will be sought for a larger, multi-centre study.

TRIAL REGISTRATION

ANZCTR ACTRN12616000206426.

Heart rate variability is reduced during acute uncomplicated diverticulitis

BACKGROUND

The aim of the present study was to report the trajectory of heart rate variability (HRV) indices during a low-grade acute inflammation and their associations to biomarkers for infection.

METHODS

Twelve patients with uncomplicated acute diverticulitis completed this observational study, which composed of 3 sessions of continuous HRV recording from 9 PM to 8 AM during ongoing diverticulitis and at complete remission (baseline). The blood samples were collected at each study session measuring C-reactive protein (CRP) and leukocytes.

RESULTS

This study showed that the trajectories of the HRV indices were decreased both in time and frequency domains during acute diverticulitis compared to baseline. In particular, the indices reflecting the balance of sympathetic and parasympathetic activities were affected: standard deviation of normal-to-normal beats (P = .003), low-frequency power (P < .001), and total power (P = .001). These HRV changes indicate alterations in the autonomic nervous system during acute inflammation. All reductions of mean HRV indices had significant (P < .001) correlations to increased CRP correlations to increased CRP levels during diverticulitis suggesting inflammatory involvement in the observed HRV alterations.

CONCLUSION

We found substantial HRV depression in relation to acute uncomplicated diverticulitis, and this was associated with the elevated CRP levels.

The C-Reactive Protein/Albumin Ratio as an Independent Predictor of Mortality in Patients with Severe Sepsis or Septic Shock Treated with Early Goal-Directed Therapy

Background

Sepsis, including severe sepsis and septic shock, is a major cause of morbidity and mortality. Albumin and C-reactive protein (CRP) are considered as good diagnostic markers for sepsis. Thus, initial CRP and albumin levels were combined to ascertain their value as an independent predictor of 180-day mortality in patients with severe sepsis and septic shock.

Materials and Methods

We conducted a retrospective cohort study involving 670 patients (>18 years old) who were admitted to the emergency department and who had received a standardized resuscitation algorithm (early goal-directed therapy) for severe sepsis and septic shock, from November 2007 to February 2013, at a tertiary hospital in Seoul, Korea. The outcome measured was 180-day all-cause mortality. A multivariate Cox proportional hazard model was used to identify the independent risk factors for mortality. A receiver operating characteristic (ROC) curve analysis was conducted to compare the predictive accuracy of the CRP/albumin ratio at admission.

Results

The 180-day mortality was 28.35% (190/670). Based on the multivariate Cox proportional hazard analysis, age, the CRP/albumin ratio at admission (adjusted HR 1.06, 95% CI 1.03–1.10, p<0.001), lactate level at admission (adjusted HR 1.10, 95% CI 1.05–1.14, p<0.001), and the Sequential Organ Failure Assessment (SOFA) score at admission (adjusted HR 1.12, 95% CI 1.07–1.18, p<0.001) were independent predictors of 180-day mortality. The area under the curve of CRP alone and the CRP/albumin ratio at admission for 180-day mortality were 0.5620 (P<0.001) and 0.6211 (P<0.001), respectively.

Conclusion

The CRP/albumin ratio was an independent predictor of mortality in patients with severe sepsis or septic shock.

Role of heart rate variability in predicting the severity of severe acute pancreatitis

BACKGROUND

Infected pancreatic necrosis (IPN) and multiple organ dysfunction syndrome (MODS) are major complications of acute pancreatitis which determine disease severity and outcome.

AIMS

The aim of this study is to investigate the value of admission heart rate variability as a marker of IPN or MODS in severe acute pancreatitis (SAP) patients.

METHODS

Forty-one SAP patients within 72 h of symptoms onset were included in this prospective observational study. General demographics, laboratory data and the acute physiology and chronic health evaluation (APACHE) II scores were recorded at admission. 5-minute ECG signals were obtained at the same time for heart rate variability analyses to assess SAP severity.

RESULTS

The baseline heart rate variability measurements, levels of low frequency/high frequency (LF/HF) were significantly lower whereas high frequency norm (nHF) levels were significantly higher in patients who present with IPN and MODS or died (P < 0.01). Low frequency (LF) levels were lower in patients who present with IPN or MODS as compared to patients without these complications. Levels of low frequency norm (nLF) were lower in MODS and non-survival patients. nHF and LF/HF were good predictors of IPN and MODS, superior to procalcitonin. nHF and LF/HF were better than APACHE II in predicting IPN and LF/HF showed superiority over APACHE II in the prediction of MODS.

CONCLUSIONS

Admission heart rate variability is a good marker of IPN and MODS in SAP patients.

I(f) blocking potency of ivabradine is preserved under elevated endotoxin levels in human atrial myocytes

Lower heart rate is associated with better survival in patients with multiple organ dysfunction syndrome (MODS), a disease mostly caused by sepsis. The benefits of heart rate reduction by ivabradine during MODS are currently being investigated in the MODI_fY clinical trial. Ivabradine is a selective inhibitor of the pacemaker current I_f and since I_f is impaired by lipopolysaccharide (LPS, endotoxin), a trigger of sepsis, we aimed to explore I_f blocking potency of ivabradine under elevated endotoxin levels in human atrial cardiomyocytes. Treatment of myocytes with S-LPS (containing the lipid A moiety, a core oligosaccharide and an O-polysaccharide chain) but not R595 (an O-chain lacking LPS-form) caused I_f inhibition under acute and chronic septic conditions. The specific interaction of S-LPS but not R595 to pacemaker channels HCN2 and HCN4 proves the necessity of O-chain for S-LPS–HCN interaction. The efficacy of ivabradine to block I_f was reduced under septic conditions, an observation that correlated with lower intracellular ivabradine concentrations in S-LPS- but not R595-treated cardiomyocytes. Computational analysis using a sinoatrial pacemaker cell model revealed that despite a reduction of I_f under septic conditions, ivabradine further decelerated pacemaking activity. This novel finding, i.e. I_f inhibition by ivabradine under elevated endotoxin levels in vitro, may provide a molecular understanding for the efficacy of this drug on heart rate reduction under septic conditions in vivo, e.g. the MODI_fY clinical trial.

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S-LPS impairs I_f via interaction of its O-chain to HCN channels.

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Efficacy of ivabradine for I_f blockage is reduced under elevated endotoxin levels.

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S-LPS reduces intracellular ivabradine concentrations.

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Ivabradine is efficient to decelerate sinoatrial pacemaking activity under septic conditions in silico.

Cardiorenal syndrome

Cardiorenal syndrome (CRS) includes a broad spectrum of diseases within which both the heart and kidneys are involved, acutely or chronically. An effective classification of CRS in 2008 essentially divides CRS in two main groups, cardiorenal and renocardiac CRS, based on primum movens of disease (cardiac or renal); both cardiorenal and renocardiac CRS are then divided into acute and chronic, according to onset of disease. The fifth type of CRS integrates all cardiorenal involvement induced by systemic disease. This article addresses the pathophysiology, diagnosis, treatment, and outcomes of the 5 distinct types of CRS.

The effect of endotoxin on the controllability of cardiac rhythm in rats

Decreased heart rate variability (HRV) has both diagnostic and prognostic value in patients with sepsis. However, it is not known whether reduced HRV in sepsis reflects an altered input from the autonomic nervous system or a remodeling of the cardiac pacemaker cells by inflammatory mediators. The present study aimed to investigate the effect of endotoxin on the heart rate dynamics of a denervated isolated heart in rats. Saline or endotoxin was injected into rats and their hearts were isolated and perfused. Atrial electrical activity was recorded and memory length in the time-series was assessed using inverse statistical analysis. Memory was defined as a statistical feature that lasts for a period of time and distinguishes the time-series from a random process. Endotoxaemic hearts exhibited a prolonged memory compared to the controls with respect to observing rare events. This indicates that a sudden decelerating event could potentially affect the cardiac rhythm of an endotoxaemic heart for a longer time than the controls. The prolongation of memory is indirectly linked to a reduced controllability in a complex system; therefore our data may provide evidence for a reduced controllability in cardiac rhythm following endotoxaemia.

Application of heart-rate variability in patients undergoing weaning from mechanical ventilation

Introduction

The process of weaning may impose cardiopulmonary stress on ventilated patients. Heart-rate variability (HRV), a noninvasive tool to characterize autonomic function and cardiorespiratory interaction, may be a promising modality to assess patient capability during the weaning process. We aimed to evaluate the association between HRV change and weaning outcomes in critically ill patients.

Methods

This study included 101 consecutive patients recovering from acute respiratory failure. Frequency-domain analysis, including very low frequency, low frequency, high frequency, and total power of HRV was assessed during a 1-hour spontaneous breathing trial (SBT) through a T-piece and after extubation after successful SBT.

Results

Of 101 patients, 24 (24%) had SBT failure, and HRV analysis in these patients showed a significant decrease in total power (P = 0.003); 77 patients passed SBT and were extubated, but 13 (17%) of them required reintubation within 72 hours. In successfully extubated patients, very low frequency and total power from SBT to postextubation significantly increased (P = 0.003 and P = 0.004, respectively). Instead, patients with extubation failure were unable to increase HRV after extubation.

Conclusions

HRV responses differ between patients with different weaning outcomes. Measuring HRV change during the weaning process may help clinicians to predict weaning results and, in the end, to improve patient care and outcome.

Study protocol: prediction of stroke associated infections by markers of autonomic control

Background

Infection is the most important complication after acute stroke. This is substantially based on a stroke-induced immunosuppression. Heart rate variability (HRV) represents the autonomic nervous system activity in connection with stroke-induced immunomodulation and infections. We demonstrated in a feasibility study that HRV indices obtained in patients without acute post-stroke infections can predict infections in the subsequent sub-acute phase.

Methods/Design

The study PRED-SEP is a prospective observational study. Adult patients with acute ischemic infarction in the territory of the middle cerebral artery and severe neurological deficit (National Institutes of Health Stroke Scale: NIHSS ≥ 8) are recruited. Primary endpoint is the development of infections, secondary endpoints are SIRS and severe sepsis in the sub-acute phase (day 3–5) after stroke and the functional outcome after 3 months. Infection is defined according to the PANTHERIS study and comprises pneumonia, urinary tract infection and infections without determined focus. SIRS and severe sepsis are defined according to German Sepsis Society guidelines. Functional outcome is measured by lethality and neurological scores (modified Rankin Scale, Barthel Index). Prognostic factors are HRV risk indices calculated from selected intervals of 24 h ECG measurements within 48 hours after symptom onset. It is planned to recruit 240 patients.

HRV risk indices (predictors) will be calculated according to standards and procedures previously developed and published by the authors. The predictive effects of HRV indices on infections will be estimated by fitting logistic regression models and estimating odds ratios with 95% confidence intervals. A prespecified modelling procedure will be applied to estimate unadjusted and confounder adjusted odds ratios. Secondary endpoints will be analysed in the same way. The functional outcome scales will be dichotomized. The association between HRV indices and pro- and anti-inflammatory markers will be quantified by calculating the appropriate correlation coefficients according to scale (Person or Spearman).

Discussion

Since a general prophylactic antibiotic treatment after stroke is not recommended, results of this study could have essential implications for an early identification and hence, timely appropriate treating of stroke-induced infections.

Trial registration

Prädiktoren für die Sepsis - Pred Sep, German Clinical Trials Register: DRKS00003392.

Impairment of small somatic and autonomic nerve fibres in intensive care unit patients with severe sepsis and critical illness polyneuropathy--a single center controlled observational study

Background

Axonal damage in large myelinated nerve fibres occurs in about 70% of patients with severe sepsis, known as critical illness polyneuropathy and contributes significantly to an increased short- and long-term morbidity and mortality in this population. Among other pathophysiological mechanisms, autonomic dysregulation, characterized by high concentrations of circulating catecholamines in the presence of impaired sympathetic modulation of heart and vessels have been discussed. We hypothesize that autonomic small fibre neuropathy play an important role in autonomic failure.

Methods/Design

Single center, non-randomized, controlled, observational study. Skin biopsies of patients with severe sepsis and/or septic shock are compared with those of age-matched controls. In order to assess impairment of small nerve fibres, skin biopsies are taken at onset of severe sepsis, and two and 16 weeks later. Intraepidermal nerve fibre densities are histologically analyzed using anti protein gene product (PGP) 9.5 immunostaining. In addition, standardized clinical examinations, as Medical Research Council (MRC) scores of muscle strength, Rankin scores, and standardized nerve conduction studies of the right median nerve, the right tibial nerve, the left fibular nerve, and both sural nerves are performed, to identify critical illness polyneuropathy and to neurophysiologically quantify the damage of large nerve fibres.

Discussion

The study will allow to describe the frequency of small fibre neuropathy in patients with severe sepsis up to four months after onset of severe sepsis and to evaluate its relationship to critical illness polyneuropathy.

Trial registration

The trial has been registered to the German Clinical Trials Register. The trial registration number is DRKS-ID: DRKS00000642.

Biomarkers in sepsis

PURPOSE OF REVIEW

This review discusses the current developments in biomarkers for sepsis.

RECENT FINDINGS

With quantum leaps in technology, an array of biomarkers will become available within the next decade as point-of-care tools that will likely revolutionize the management of sepsis. These markers will facilitate early and accurate diagnosis, faster recognition of impending organ dysfunction, optimal selection and titration of appropriate therapies, and more reliable prognostication of risk and outcome. These diagnostics will also enable an improved characterization of the biological phenotype underlying sepsis and thus a better appreciation of the condition.

SUMMARY

The potential for novel biomarkers in sepsis will need to be properly realized with considerable funding, academic-industry collaborations, appropriate investigations and validation in heterogenous populations, but these developments do hold the capacity to transform patient care and outcomes.

Peripheral neural detection of danger-associated and pathogen-associated molecular patterns

Objective:

Bidirectional links between the nervous and immune systems modulate inflammation. The cellular mechanisms underlying the detection of danger-associated molecular patterns and pathogen-associated molecular patterns by the nervous system are not well understood. We hypothesized that the carotid body, a tissue of neural crest origin, detect pathogen associated molecular patterns and danger associated molecular patterns via an inflammasome-dependent mechanism similar to that described in immune cells.

Design:

Randomized, controlled laboratory investigation.

Setting:

University laboratory.

Subjects:

C57Bl/6J mice; juvenile Sprague-Dawley rats, primary human neutrophils.

Interventions:

Rat carotid body chemosensitive cells, and human neutrophils, were treated with TLR agonists to activate inflammasome-dependent pathways. In mice, systemic inflammation was induced by the pathogen associated molecular pattern zymosan (intraperitoneal injection; 500 mg/kg). Isolated carotid body/carotid sinus nerve preparations were used to assess peripheral chemoafferent activity. Ventilation was measured by whole-body plethysmography.

Measurements and Main Results:

Chemosensitive carotid body glomus cells exhibited toll-like receptor (TLR-2 and TLR-4), NLRP1, and NLRP3 inflammasome immunoreactivities. Zymosan increased NLRP3 inflammasome and interleukin-1β expression in glomus cells (p < 0.01). Human neutrophils demonstrated similar LPS-induced changes in inflammasome expression. Carotid body glomus cells also expressed IL-1 receptor and responded to application of IL-1β with increases in intracellular [Ca²⁺]. Four hours after injection of zymosan carotid sinus nerve chemoafferent discharge assessed in vitro (i.e., in the absence of acidosis/circulating inflammatory mediators) was increased five-fold (p < 0.001). Accordingly, zymosan-induced systemic inflammation was accompanied by enhanced respiratory activity.

Conclusions:

In carotid body chemosensitive glomus cells, activation of toll-like receptors increases NLRP3 inflammasome expression, and enhances IL-1β production, which is capable of acting in an autocrine manner to enhance peripheral chemoreceptor drive.

Effect of early statin treatment in patients with cardiogenic shock complicating acute myocardial infarction

Background and Objectives

The benefit of early statin treatment following acute myocardial infarction (MI) complicated with cardiogenic shock (CS) has not been well studied. We sought to assess the effect of early statin therapy in patients with CS complicating acute MI.

Subjects and Methods

We studied 553 statin-naive patients with acute MI and CS (Killip class IV) who underwent revascularization therapy between November 2005 and January 2008 at 51 hospitals in the Korea Acute Myocardial Infarction Registry. Patients were divided into 2 groups: those who received statins during hospitalization (n=280) and those who did not (n=273). The influence of statin treatment on a 12-month clinical outcome was examined using a matched-pairs analysis (n=200 in each group) based on the propensity for receiving statin therapy during hospitalization.

Results

Before adjustment, patients receiving statin, compared to those not receiving statin, had a more favorable clinical profile, were less likely to suffer procedural complications, and more likely to receive adequate medical therapy. Patients receiving statin had lower unadjusted in-hospital mortality and composite rate of mortality, MI, and repeat revascularization at 12 months, which remained significantly lower after adjustment for patient risk, procedural characteristics, and treatment propensity.

Conclusion

In CS patients with acute MI undergoing revascularization therapy, early statin treatment initiated during hospitalization was associated with lower rates of in-hospital death and 12-month adverse cardiac events.

Effort-adapted modes of assisted breathing

PURPOSE OF REVIEW

New developments in mechanical ventilation have focused on increasing the patient's control of the ventilator by implementing information on lung mechanics and respiratory drive. Effort-adapted modes of assisted breathing are presented and their potential advantages are discussed.

RECENT FINDINGS

Adaptive support ventilation, proportional assist ventilation with load adjustable gain factors and neurally adjusted ventilatory assist are ventilatory modes that follow the concept of adapting the assist to a defined target, instantaneous changes in respiratory drive or lung mechanics. Improved patient ventilator interaction, sufficient unloading of the respiratory muscles and increased comfort have been recently associated with these ventilator modalities. There are, however, scarce data with regard to outcome improvement, such as length of mechanical ventilation, ICU stay or mortality (commonly accepted targets to demonstrate clinical superiority).

SUMMARY

Within recent years, a major step forward in the evolution of assisted (effort-adapted) modes of mechanical ventilation was accomplished. There is growing evidence that supports the physiological concept of closed-loop effort-adapted assisted modes of mechanical ventilation. However, at present, the translation into a clear outcome benefit remains to be proven. In order to fill the knowledge gap that impedes the broader application, larger randomized controlled trials are urgently needed. However, with clearly proven drawbacks of conventional assisted modes such as pressure support ventilation, it is probably about time to leave these modes introduced decades ago behind.

Heart rate variability: a diagnostic and prognostic tool in anesthesia and intensive care

The autonomic nervous system (ANS) plays an important role in the human response to various internal and external stimuli, which can modify homeostasis, and exerts a tight control on essential functions such as circulation, respiration, thermoregulation and hormonal secretion. ANS dysfunction may complicate the perioperative course in the surgical patient undergoing anesthesia, increasing morbidity and mortality, and, therefore, it should be considered as an additional risk factor during pre-operative evaluation. Furthermore, ANS dysfunction may complicate the clinical course of critically ill patients admitted to intensive care units, in the case of trauma, sepsis, neurologic disorders and cardiovascular diseases, and its occurrence adversely affects the outcome. In the care of these patients, the assessment of autonomic function may provide useful information concerning pathophysiology, risk stratification, early prognosis prediction and treatment strategies. Given the role of ANS in the maintenance of systemic homeostasis, anesthesiologists and intensivists should recognize as critical the evaluation of ANS function. Measurement of heart rate variability (HRV) is an easily accessible window into autonomic activity. It is a low-cost, non-invasive and simple to perform method reflecting the balance of the ANS regulation of the heart rate and offers the opportunity to detect the presence of autonomic neuropathy complicating several illnesses. The present review provides anesthesiologists and intensivists with a comprehensive summary of the possible clinical implications of HRV measurements, suggesting that autonomic dysfunction testing could potentially represent a diagnostic and prognostic tool in the care of patients both in the perioperative setting as well as in the critical care arena.

Differential reduction of HCN channel activity by various types of lipopolysaccharide

Recently it was shown that lipopolysaccharide (LPS) impairs the pacemaker current in human atrial myocytes. It was speculated that reduced heart rate variability (HRV), typical of patients with severe sepsis, may partially be explained by this impairment. We evaluated the effect of various types of LPS on the activity of human hyperpolarization-activated cyclic nucleotide-gated channel 2 (hHCN2) expressed in HEK293 cells, and on pacemaker channels in native murine sino-atrial node (SAN) cells, in order to determine the structure of LPS necessary to modulate pacemaker channel function. Application of LPS caused a robust inhibition of hHCN2-mediated current (I(hHCN2)) owing to a negative shift of the voltage dependence of current activation and to a reduced maximal conductance. In addition, kinetics of channel gating were modulated by LPS. Pro-inflammatory LPS-types lacking the O-chain did not reduce I(hHCN2), whereas pro-inflammatory LPS-types containing the O-chain reduced I(hHCN2). On the other hand, a detoxified LPS without inflammatory activity, but containing the O-chain reduced I(hHCN2). Similar observations were made in HEK293 cells expressing hHCN4 and in murine SAN cells. This mechanistic analysis showed the novel finding that the O-chain of LPS is required for reduction of HCN channel activity. In the clinical situation the observed modulation of HCN channels may slow down diastolic depolarization of pacemaker cells and, hence, influence heart rate variability and heart rate.

Autonomic dysfunction in older people

The autonomic nervous system comprises the sympathetic, parasympathetic and enteric nervous systems and plays an integral role in homeostasis. This includes cardiovascular and temperature control, glucose metabolism, gastrointestinal and reproductive function and increasing evidence to support its involvement in the inflammatory response to infection and cancer. Ageing is associated with autonomic dysfunction, and many clinical syndromes associated with older adults are due to inadequate autonomic responses to physiological stressors. The aim of this review is to explore the relationship between autonomic dysfunction and ageing illustrated with examples of maladaptive autonomic responses in a variety of different clinical syndromes including an exploration of autonomic cellular changes. Appropriate investigation and management strategies are outlined, recognizing the fine balance needed to improve symptoms without creating further medical complications.

Whole blood cytokine attenuation by cholinergic agonists ex vivo and relationship to vagus nerve activity in rheumatoid arthritis

OBJECTIVE

The central nervous system regulates innate immunity in part via the cholinergic anti-inflammatory pathway, a neural circuit that transmits signals in the vagus nerve that suppress pro-inflammatory cytokine production by an alpha-7 nicotinic acetylcholine receptors (alpha7nAChR) dependent mechanism. Vagus nerve activity is significantly suppressed in patients with autoimmune diseases, including rheumatoid arthritis (RA). It has been suggested that stimulating the cholinergic anti-inflammatory pathway may be beneficial to patients, but it remains theoretically possible that chronic deficiencies in this pathway will render these approaches ineffective.

METHODS

Here we addressed the hypothesis that inflammatory cells from RA patients can respond to cholinergic agonists with reduced cytokine production in the setting of reduced vagus nerve activity.

RESULTS

Measurement of RR interval variability (heart rate variability, HRV), in RA patients (n = 13) and healthy controls (n = 10) revealed that vagus nerve activity was significantly depressed in patients. Whole blood cultures stimulated by exposure to endotoxin produced significantly less tumour necrosis factor in samples from RA patients as compared to healthy controls. Addition of cholinergic agonists (nicotine and GTS-21) to the stimulated whole blood cultures however significantly suppressed cytokine production to a similar extent in patients and healthy controls.

CONCLUSION

These findings suggest that it is possible to pharmacologically target the alpha7nAChR dependent control of cytokine release in RA patients with suppressed vagus nerve activity. As alpha7nAChR agonists ameliorate the clinical course of collagen induced arthritis in animals, it may be possible in the future to explore whether alpha7nAChR agonists can improve clinical activity in RA patients.

Impaired regulation of cardiac function in sepsis, SIRS, and MODS

In sepsis, systemic inflammatory response syndrome (SIRS), and multiorgan dysfunction syndrome (MODS), a severe prognostically relevant cardiac autonomic dysfunction exists, as manifested by a strong attenuation of sympathetically and vagally mediated heart rate variability (HRV). The mechanisms underlying this attenuation are not limited to the nervous system. They also include alterations of the cardiac pacemaker cells on a cellular level. As shown in human atrial cardiomyocytes, endotoxin interacts with cardiac hyperpolarization-activated cyclic nucleotide-gated (HCN) ion channels, which mediate the pacemaker current If and play an important role in transmitting sympathetic and vagal signals on heart rate and HRV. Moreover, endotoxin sensitizes cardiac HCN channels to sympathetic signals. These findings identify endotoxin as a pertinent modulator of the autonomic nervous regulation of heart function. In MODS, the vagal pathway of the autonomic nervous system is particularly compromised, leading to an attenuation of the cholinergic antiinflammatory reflex. An amelioration of the blunted vagal activity appears to be a promising novel therapeutic target to achieve a suppression of the inflammatory state and thereby an improvement of prognosis in MODS patients. Preliminary data revealed therapeutic benefits (increased survival rates and improvements of the depressed vagal activity) of the administration of statins, beta-blockers, and angiotensin-converting enzyme inhibitors in patients with MODS.

Role of nuclear factor-kappaB-dependent induction of cytokines in the regulation of vasopressin V1A-receptors during cecal ligation and puncture-induced circulatory failure

OBJECTIVE

Here we characterize the impact of nuclear factor-kappaB and cytokines on cecal ligation and puncture-induced circulatory failure and regulation of vasopressin V1A-receptors during inflammation.

DESIGN

Prospective animal trial.

SETTING

Laboratory of the Department of Anesthesiology.

SUBJECTS

Male C57/BL6 mice.

INTERVENTIONS

The effects of cecal ligation and puncture on hemodynamic parameters and V1A-receptor expression were measured in cytokine knock-out mice, in mice with/without treatment with glucocorticoids or NF-kappaB-inhibitors, in mice pretreated with small interfering RNA silencing NF-kappaB and in mice treated with V1 receptor agonists. Furthermore, the effects of cytokines on V1A-receptor expression were determined.

MEASUREMENTS AND MAIN RESULTS

Cecal ligation and puncture resulted in a hyperdynamic circulatory failure with diminished blood pressor dose response to V1 receptor agonists and down-regulation of V1A-receptors. Dexamethasone inhibited proinflammatory cytokine production and attenuated cecal ligation and puncture-induced cardiovascular failure in parallel with attenuated down-regulation of V1A-receptor expression. Tumor necrosis factor-alpha, interleukin-1beta, interferon-gamma or interleukin-6 dose-dependently decreased V1A-receptor expression, whereas cecal ligation and puncture-induced down-regulation of V1A-receptors was not affected in cytokine knock-out mice. In contrast, inhibition of NF-kappaB strongly reduced induction of cytokines, prevented septic circulatory failure and down-regulation of V1A-receptor gene expression and improved survival of septic animals.

CONCLUSIONS

Our data demonstrate that down-regulation of V1A-receptor expression during sepsis may be due to proinflammatory cytokines. Our findings explain the failure of therapeutic strategies targeting single cytokines as well as the success of glucocorticoid therapy and define a critical role for NF-kappaB in the pathogenesis of septic shock.