The effects of brain injury on heart rate variability and the innate immune response in critically ill patients

Recovery and immune function after low pressure pneumoperitoneum during robot-assisted radical prostatectomy: a randomised controlled trial

OBJECTIVE

To compare the effectiveness of low intra-abdominal pressure (IAP) facilitated by deep neuromuscular block (NMB) to standard practice in improving the quality of recovery, preserving immune function, and enhancing parietal perfusion during robot-assisted radical prostatectomy (RARP).

PATIENTS AND METHODS

In this blinded, randomised controlled trial, 96 patients were randomised to the experimental group with low IAP (8 mmHg) facilitated by deep NMB (post-tetanic count 1-2) or the control group with standard IAP (14 mmHg) and moderate NMB (train-of-four 1-2). Recovery was measured using the 40-item Quality of Recovery questionnaire and 36-item Short-Form Health survey. Immune function was evaluated by plasma damage-associated molecular patterns, cytokines, and ex vivo lipopolysaccharide-stimulated cytokine production. Parietal peritoneum perfusion was measured by analysing the recordings of indocyanine-green injection.

RESULTS

Quality of recovery was not superior in the experimental group (n = 46) compared to the control group (n = 50). All clinical outcomes, including pain scores, postoperative nausea and vomiting, and hospital stay were similar. There were no significant differences in postoperative plasma concentrations of damage-associated molecular patterns, cytokines, and ex vivo cytokine production capacity. The use of low IAP resulted in better parietal peritoneum perfusion.

CONCLUSION

Despite better perfusion of the parietal peritoneum, low IAP facilitated by deep NMB did not improve the quality of recovery or preserve immune function compared to standard practice in patients undergoing RARP.

The role of surgical tissue injury and intraoperative sympathetic activation in postoperative immunosuppression after breast-conserving surgery versus mastectomy: a prospective observational study

BACKGROUND

Breast cancer is the second most common cause of death from cancer in women worldwide. Counterintuitively, large population-based retrospective trials report better survival after breast-conserving surgery (BCS) compared to mastectomy, corrected for tumour- and patient variables. More extensive surgical tissue injury and activation of the sympathetic nervous system by nociceptive stimuli are associated with immune suppression. We hypothesized that mastectomy causes a higher expression of plasma damage associated molecular patterns (DAMPs) and more intraoperative sympathetic activation which induce postoperative immune dysregulation. Immune suppression can lead to postoperative complications and affect tumour-free survival.

METHODS

In this prospective observational study, plasma DAMPs (HMGB1, HSP70, S100A8/A9 and S100A12), intraoperative sympathetic activation (Nociception Level (NOL) index from 0 to 100), and postoperative immune function (plasma cytokine concentrations and ex vivo cytokine production capacity) were compared in patients undergoing elective BCS (n = 20) versus mastectomy (n = 20).

RESULTS

Ex vivo cytokine production capacity of TNF, IL-6 and IL-1β was nearly absent in both groups one hour after surgery. Levels appeared recovered on postoperative day 3 (POD3), with significantly higher ex vivo production capacity of IL-1β after BCS (p = .041) compared to mastectomy. Plasma concentration of IL-6 was higher one hour after mastectomy (p = .045). Concentrations of plasma alarmins S100A8/A9 and S100A12 were significantly higher on POD3 after mastectomy (p = .003 and p = .041, respectively). Regression analysis showed a significantly lower percentage of NOL measurements ≤ 8 (absence of nociception) during mastectomy when corrected for norepinephrine equivalents (36% versus 45% respectively, p = .038). Percentage of NOL measurements ≤ 8 of all patients correlated with ex vivo cytokine production capacity of IL-1β and TNF on POD3 (r = .408; p = .011 and r = .500; p = .001, respectively).

CONCLUSIONS

This pilot study revealed substantial early postoperative immune suppression after BCS and mastectomy that appears to recover in the following days. Differences between BCS and mastectomy in release of DAMPs and intraoperative sympathetic activation could affect postoperative immune homeostasis and thereby contribute to the better survival reported after BCS in previous large population-based retrospective trials. These results endorse further exploration of (1) S100 alarmins as potential therapeutic targets in breast cancer surgery and (2) suppression of intraoperative sympathetic activation to substantiate the observed association with postoperative immune dysregulation.

The Clinical Characteristics of Heart Rate Variability After Stroke: A Systematic Review

The autonomic nervous system dysfunction has been reported in up to 76% of stroke patients 7 days after an acute stroke. Heart rate variability (HRV) is one of the important indicators reflecting the balance of sympathetic and parasympathetic nerves. Therefore, we performed a systematic literature review of existing literature on the association between heart rate variability and the different types of stroke. We included studies published in the last 32 years (1990 to 2022). The electronic databases MEDLINE and PubMed were searched. We selected the research that met the inclusion or exclusion criteria. A narrative synthesis was performed. This review aimed to summarize evidence regarding the potential mechanism of heart rate variability among patients after stroke. In addition, the association of clinical characteristics of heart rate variability and stroke has been depicted. The review further discussed the relationship between post-stroke infection and heart rate variability, which could assist in curbing clinical infection in patients with stroke. HRVas a noninvasive clinical monitoring tool can quantitatively assess the changes in autonomic nervous system activity and further predict the outcome of stroke. HRV could play an important role in guiding the clinical practice for autonomic nervous system disorder after stroke.

Heart Rate Variability in Patients with Spontaneous Intracerebral Hemorrhage and its Relationship with Clinical Outcomes

BACKGROUND

Although abnormal heart rate variability (HRV) is frequently observed in patients with spontaneous intracerebral hemorrhage (ICH), its time course and presentation of different indices remain unclear, and few studies have focused on its association with clinical outcomes.

METHODS

We prospectively recruited consecutive patients with spontaneous ICH between June 2014 and June 2021. HRV was evaluated twice during hospitalization (within 7 days and 10-14 days after stroke). Time and frequency domain indices were calculated. A modified Rankin Scale score ≥ 3 at 3 months was defined as a poor outcome.

RESULTS

Finally, 122 patients with ICH and 122 age- and sex-matched volunteers were included. Compared with controls, time domain and absolute frequency domain HRV parameters (total power, low frequency [LF], and high frequency [HF]) in the ICH group were significantly decreased within 7 days and 10-14 days. For relative values, normalized LF (LF%) and LF/HF were significantly higher, whereas normalized HF (HF%) was significantly lower, in the patient group than in the control group. Furthermore, LF% and HF% measured at 10-14 days were independently associated with 3-month outcomes.

CONCLUSIONS

HRV values were impaired significantly within 14 days after ICH. Furthermore, HRV indices measured 10-14 days after ICH were independently associated with 3-month outcomes.

Vagal cardiac control in rats with LPS-induced lung injury

Heart rate variability (HRV) as an index of cardiac autonomic control in acute lung injury (ALI) has been evaluated in anaesthetized rats intratracheally instilled with bacterial lipopolysaccharide (LPS) and ventilated with breathing frequency of 60/min, 40% oxygen, inspiratory time 40%, tidal volume of 6 mL/kg. ECG was recorded before and 30, 60, 120, 180 and 240 min after LPS or saline (control) administration. HRV was quantified by time and frequency-domain analysis (mean RR interval, SDRR, RMSSD and spectral power in high frequency (HF) band. Lactate in plasma, and oxidative stress, IL-1β, IL-5, IL-12p70 and IL-13 and galectin-3 in heart tissue raised in LPS-injured rats. Overall HRV magnitude (SDRR) and marker of vagal heart rate control (RMSSD), as well as frequency domain parameter, spectral power HF was increased 120 and 180 min since ALI onset. In conclusion, LPS-induced ALI is accompanied by altered vagal cardiac control mediated by autonomic nervous system, likely based on the close relationship between immune response and vagally mediated autonomic nervous activity.

Heart Rate Variability for Outcome Prediction in Intracerebral and Subarachnoid Hemorrhage: A Systematic Review

This systematic review presents clinical evidence on the association of heart rate variability with outcome prediction in intracerebral and subarachnoid hemorrhages. The literature search led to the retrieval of 19 significant studies. Outcome prediction included functional outcome, cardiovascular complications, secondary brain injury, and mortality. Various aspects of heart rate recording and analysis, based on linear time and frequency domains and a non-linear entropy approach, are reviewed. Heart rate variability was consistently associated with poor functional outcome and mortality, while controversial results were found regarding the association between heart rate variability and secondary brain injury and cardiovascular complications.

Preoperative assessment of optic nerve sheath diameter and heart rate variability to predict intraoperative brain condition in patients with supratentorial tumors: a prospective observational study

Brain relaxation is an important requirement in intracranial neurosurgical procedures and optimal brain relaxation improves the operating conditions. Optic nerve sheath diameter (ONSD) is a non-invasive bedside surrogate marker of intracranial pressure (ICP) status. Elevated ICP is often associated with marked autonomic dysfunction. There is no standard measure to predict intraoperative brain condition non-invasively, considering both anatomical displacement and physiological effects due to raised ICP and brain oedema. This study was aimed to determine the usefulness of heart rate variability (HRV) parameters and ONSD preoperatively in predicting intraoperative brain relaxation in patients with supratentorial tumors undergoing surgery.This prospective observational study was conducted in a tertiary care centre. 58 patients with supratentorial brain tumors undergoing elective surgery were studied. Preoperative clinical presentation, computed tomography (CT) findings, ONSD and HRV parameters were assessed in determining intraoperative brain condition. Intraoperative hemodynamic parameters and brain relaxation score after craniotomy were studied. There was significant difference in CT grade, ONSD and HRV parameters in patients between lax and tight brain. A receiver operating curve was constructed to determine the cut off to predict intraoperative brain bulge. A CT grade more than 2, ONSD of greater than 0.63 cms and ratio of low frequency to high ratio (LF/HF) of more than 1.8 were good predictors of brain bulge. The changes in ONSD and HRV parameters, with the CT findings can be used as surrogate markers of increased ICP to help predict intraoperative brain condition.

The cholinergic anti-inflammatory pathway in humans: State-of-the-art review and future directions

The parasympathetic nervous system modulates inflammation through efferent vagus nerve signaling. Tracey (2002) termed this process as the cholinergic anti-inflammatory pathway (CAP). Interest in the potential practical use of this immune-modulatory process is increasing alongside increasing appreciation for the role of systemic inflammation in the etiology of somatic and psychological disease. A diverse literature exists providing expansive correlational evidence and some preliminary experimental evidence of the CAP in humans. However, so far this literature has not been well integrated and critically evaluated. This review describes the current state-of-the-art of research into vagus nerve driven parasympathetic control of inflammation in humans. Substantial limitations and gaps in the literature are identified, and promising directions for future research are highlighted.

Dynamic Temporal Relationship Between Autonomic Function and Cerebrovascular Reactivity in Moderate/Severe Traumatic Brain Injury

There has been little change in morbidity and mortality in traumatic brain injury (TBI) in the last 25 years. However, literature has emerged linking impaired cerebrovascular reactivity (a surrogate of cerebral autoregulation) with poor outcomes post-injury. Thus, cerebrovascular reactivity (derived through the pressure reactivity index; PRx) is emerging as an important continuous measure. Furthermore, recent literature indicates that autonomic dysfunction may drive impaired cerebrovascular reactivity in moderate/severe TBI. Thus, to improve our understanding of this association, we assessed the physiological relationship between PRx and the autonomic variables of heart rate variability (HRV), blood pressure variability (BPV), and baroreflex sensitivity (BRS) using time-series statistical methodologies. These methodologies include vector autoregressive integrative moving average (VARIMA) impulse response function analysis, Granger causality, and hierarchical clustering. Granger causality testing displayed inconclusive results, where PRx and the autonomic variables had varying bidirectional relationships. Evaluating the temporal profile of the impulse response function plots demonstrated that the autonomic variables of BRS, ratio of low/high frequency of HRV and very low frequency HRV all had a strong relation to PRx, indicating that the sympathetic autonomic response may be more closely linked to cerebrovascular reactivity, then other variables. Finally, BRS was consistently associated with PRx, possibly demonstrating a deeper relationship to PRx than other autonomic measures. Taken together, cerebrovascular reactivity and autonomic response are interlinked, with a bidirectional impact between cerebrovascular reactivity and circulatory autonomics. However, this work is exploratory and preliminary, with further study required to extract and confirm any underlying relationships.

Central nervous system injury-induced immune suppression

Central nervous system trauma is a common cause of morbidity and mortality. Additionally, these injuries frequently occur in younger individuals, leading to lifetime expenses for patients and caregivers and the loss of opportunity for society. Despite this prevalence and multiple attempts to design a neuroprotectant, clinical trials for a pharmacological agent for the treatment of traumatic brain injury (TBI) or spinal cord injury (SCI) have provided disappointing results. Improvements in outcome from these disease processes in the past decades have been largely due to improvements in supportive care. Among the many challenges facing patients and caregivers following neurotrauma, posttraumatic nosocomial infection is a significant and potentially reversible risk factor. Multiple animal and clinical studies have provided evidence of posttraumatic systemic immune suppression, and injuries involving the CNS may be even more prone, leading to a higher risk for in-hospital infections following neurotrauma. Patients who have experienced neurotrauma with nosocomial infection have poorer recovery and higher risks of long-term morbidity and in-hospital mortality than patients without infection. As such, the etiology and reversal of postneurotrauma immune suppression is an important topic. There are multiple possible etiologies for these posttraumatic changes including the release of damage-associated molecular patterns, the activation of immunosuppressive myeloid-derived suppressor cells, and sympathetic nervous system activation. Postinjury systemic immunosuppression, particularly following neurotrauma, provides a challenge for clinicians but also an opportunity for improvement in outcome. In this review, the authors sought to outline the evidence of postinjury systemic immune suppression in both animal models and clinical research of TBI, TBI polytrauma, and SCI.

The Effect of Hyperbaric Oxygen Therapy on Markers of Oxidative Stress and the Immune Response in Healthy Volunteers

Hyperbaric oxygen therapy (HBOT) consists of breathing 100% oxygen under increased ambient pressure. There are indications that HBOT induces oxidative stress and activates immune pathways. However, previous research on immunological effects of HBOT has mainly been established in in vitro experiments and selected patient populations, limiting generalizability and increasing the chances of confounding by comorbidities and specific patient-related factors. More insight into the immunological effects of HBOT would aid investigation and comprehension of potentially novel treatment applications. Therefore, in this study, we investigated the effects of three 110-min HBOT-sessions with 24-h intervals on immunological parameters in healthy, young, male volunteers. Blood samples were obtained before and after the first and third HBOT sessions. We assessed neutrophilic reactive oxygen species (ROS) production, systemic oxidative stress [plasma malondialdehyde (MDA) concentrations] as well as neutrophil phagocytic activity, plasma concentrations of tumor necrosis factor (TNF), interleukin (IL)-6, IL-8, and IL-10, and production of TNF, IL-6, and IL-10 by leukocytes ex vivo stimulated with the Toll-like receptor (TLR) ligands lipopolysaccharide (TLR4) and Pam3Cys (TLR2). We observed decreased neutrophilic ROS production and phagocytosis following the second HBOT session, which persisted after the third session, but no alterations in MDA concentrations. Furthermore, plasma concentrations of the investigated cytokines were unaltered at all-time points, and ex vivo cytokine production was largely unaltered over time as well. These results indicate no induction of systemic oxidative stress or a systemic inflammatory response after repeated HBOT in healthy volunteers but may suggest exhaustion of ROS generation capacity and phagocytosis.

Case-control study on the interplay between immunoparalysis and delirium after cardiac surgery

Background

Delirium occurs frequently following cardiothoracic surgery, and infectious disease is an important risk factor for delirium. Surgery and cardiopulmonary bypass induce suppression of the immune response known as immunoparalysis. We aimed to investigate whether delirious patients had more pronounced immunoparalysis following cardiothoracic surgery than patients without delirium, to explain this delirium-infection association.

Methods

A prospective matched case–control study was performed in two university hospitals. Cytokine production (tumor necrosis factor (TNF)-α, interleukin (IL)-6, IL-8 and IL-10) of ex vivo lipopolysaccharide (LPS)-stimulated whole blood was analyzed in on-pump cardiothoracic surgery patients preoperatively, and at 5 timepoints up to 3 days after cardiothoracic surgery. Delirium was assessed by trained staff using two validated delirium scales and chart review.

Results

A total of 89 patients were screened of whom 14 delirious and 52 non-delirious patients were included. Ex vivo-stimulated production of TNF-α, IL-6, IL-8, and IL-10 was severely suppressed following cardiothoracic surgery compared to pre-surgery. Postoperative release of cytokines in non-delirious patients was attenuated by 84% [IQR: 13–93] for TNF-α, 95% [IQR: 78–98] for IL-6, and 69% [IQR: 55–81] for IL-10. The attenuation in ex vivo-stimulated production of these cytokines was not significantly different in patients with delirium compared to non-delirious patients (p > 0.10 for all cytokines).

Conclusions

The post-operative attenuation of ex vivo-stimulated production of pro- and anti-inflammatory cytokines was comparable between patients that developed delirium and those who remained delirium-free after on-pump cardiothoracic surgery. This finding suggests that immunoparalysis is not more common in cardiothoracic surgery patients with delirium compared to those without.

Heart Rate Variability and Circulating Inflammatory Markers in Midlife

Theoretical perspectives and empirical evidence suggest that the parasympathetic nervous system engages in active monitoring and moderating of inflammatory processes. A clearer understanding of the bidirectional communication between the parasympathetic nervous system and the immune system could lead to novel clinical interventions for inflammatory illnesses. The current study used a large (N ​= ​836) nationally representative sample of adults in the United States to investigate the associations between resting parasympathetic modulation of the heart, indexed through both high frequency heart rate variability (HF-HRV) and low frequency heart rate variability (LF-HRV), and six circulating markers of inflammation. Statistical analyses revealed robust inverse associations of HF-HRV with interleukin-6 (IL6), C-reactive protein (CRP), and fibrinogen, with or without covariate adjustment. Similar inverse associations were observed between LF-HRV and IL6 and CRP. No significant associations were observed between HRV and either inflammatory adhesion molecules (E-selectin, intracellular adhesion molecule-1) or soluble IL6 receptor. Results are consistent with the cholinergic anti-inflammatory pathway and suggest that parasympathetic modulation of inflammation through the vagus nerve may act on specific inflammatory molecules more than others.

Heart rate variability as possible marker of brain damage in neonates with hypoxic ischemic encephalopathy: a systematic review

Heart rate variability (HRV) is currently considered the most valuable non-invasive test to investigate the autonomic nervous system function, based on the fact that fast fluctuations might specifically reflect changes of sympathetic and vagal activity. An association between abnormal values of HRV and brain impairment has been reported in the perinatal period, although data are still fragmentary. Considering such association, HRV has been suggested as a possible marker of brain damage also in case of hypoxic-ischemic encephalopathy following perinatal asphyxia. The aim of the present manuscript was to review systematically the current knowledge about the use of HRV as marker of cerebral injury in neonates suffering from hypoxic-ischemic encephalopathy. Findings reported in this paper were based on qualitative analysis of the reviewed data. Conclusion: A growing body of research supports the use of HRV as non-invasive, bedside tool for the monitoring of hypoxic-ischemic encephalopathy. The currently available data about the role of HRV as prognostic tool in case of hypoxic ischemic encephalopathy are promising but require further validation by future studies. What is Known: • Heart rate variability (HRV) is a non-invasive monitoring technique to assess the autonomic nervous system activity. • A correlation between abnormal HRV and cerebral injury has been reported in the perinatal period, and HRV has been suggested as possible marker of brain damage in case of hypoxic-ischemic encephalopathy. What is New: • HRV might provide precocious information about the entity of brain injury in asphyxiated neonates and be of help to design early, specific, and personalized treatments according to severity. • Further investigations are required to confirm these preliminary data.

Utilizing heart rate variability to predict ICU patient outcome in traumatic brain injury

Background

Prediction of patient outcome in medical intensive care units (ICU) may help for development and investigation of early interventional strategies. Several ICU scoring systems have been developed and are used to predict clinical outcome of ICU patients. These scores are calculated from clinical physiological and biochemical characteristics of patients. Heart rate variability (HRV) is a correlate of cardiac autonomic regulation and has been evident as a marker of poor clinical prognosis. HRV can be measured from the electrocardiogram non-invasively and monitored in real time. HRV has been identified as a promising ‘electronic biomarker’ of disease severity. Traumatic brain injury (TBI) is a subset of critically ill patients admitted to ICU, with significant morbidity and mortality, and often difficult to predict outcomes. Changes of HRV for brain injured patients have been reported in several studies. This study aimed to utilize the continuous HRV collection from admission across the first 24 h in the ICU in severe TBI patients to develop a patient outcome prediction system.

Results

A feature extraction strategy was applied to measure the HRV fluctuation during time. A prediction model was developed based on HRV measures with a genetic algorithm for feature selection. The result (AUC: 0.77) was compared with earlier reported scoring systems (highest AUC: 0.76), encouraging further development and practical application.

Conclusions

The prediction models built with different feature sets indicated that HRV based parameters may help predict brain injury patient outcome better than the previously adopted illness severity scores.

Autonomic nervous system activity and the risk of nosocomial infection in critically ill patients with brain injury

PURPOSE

Nosocomial infection contributes to adverse outcome after brain injury. This study investigates whether autonomic nervous system activity is associated with a decreased host immune response in patients following stroke or traumatic brain injury (TBI).

METHODS

A prospective study was performed in adult patients with TBI or stroke who were admitted to the Intensive Care Unit of our tertiary university hospital between 2013 and 2016. Heart rate variability (HRV) was recorded daily and assessed for autonomic nervous system activity. Outcomes were nosocomial infections and immunosuppression, which was assessed ex vivo using whole blood stimulations with plasma of patients with infections, matched non-infected patients and healthy controls.

RESULTS

Out of 64 brain injured patients, 23 (36%) developed an infection during their hospital stay. The ability of brain injured patients to generate a host response to the bacterial endotoxin lipopolysaccharides (LPS) was diminished compared to healthy controls (p < 0.001). Patients who developed an infection yielded significantly lower TNF-α values (86 vs 192 pg/mL, p = 0.030) and a trend towards higher IL-10 values (122 vs 84 pg/mL, p = 0.071) following ex vivo whole blood stimulations when compared to patients not developing an infection. This decreased host immune response was associated with altered admission HRV values. Brain injured patients who developed an infection showed increased normalized high-frequency power compared to patients not developing an infection (0.54 vs 0.36, p = 0.033), whereas normalized low-frequency power was lower in infected patients (0.46 vs 0.64, p = 0.033).

CONCLUSION

Brain injured patients developing a nosocomial infection show parasympathetic predominance in the acute phase following brain injury, reflected by alterations in HRV, which parallels a decreased ability to generate an immune response to stimulation with LPS.

A Narrative Review of Cardiovascular Abnormalities After Spontaneous Intracerebral Hemorrhage

BACKGROUND

The recommended cardiac workup of patients with spontaneous intracerebral hemorrhage (ICH) includes an electrocardiogram (ECG) and cardiac troponin. However, abnormalities in other cardiovascular domains may occur. We reviewed the literature to examine the spectrum of observed cardiovascular abnormalities in patients with ICH.

METHODS

A narrative review of cardiovascular abnormalities in ECG, cardiac biomarkers, echocardiogram, and hemodynamic domains was conducted on patients with ICH.

RESULTS

We searched PubMed for articles using MeSH Terms "heart," "cardiac," hypertension," "hypotension," "blood pressure," "electro," "echocardio," "troponin," "beta natriuretic peptide," "adverse events," "arrhythmi," "donor," "ICH," "intracerebral hemorrhage." Using Covidence software, 670 articles were screened for title and abstracts, 482 articles for full-text review, and 310 extracted. A total of 161 articles met inclusion and exclusion criteria, and, included in the manuscript. Cardiovascular abnormalities reported after ICH include electrocardiographic abnormalities (56% to 81%) in form of prolonged QT interval (19% to 67%), and ST-T changes (19% to 41%), elevation in cardiac troponin (>0.04 ng/mL), and beta-natriuretic peptide (BNP) (>156.6 pg/mL, up to 78%), echocardiographic abnormalities in form of regional wall motion abnormalities (14%) and reduced ejection fraction. Location and volume of ICH affect the prevalence of cardiovascular abnormalities. Prolonged QT interval, elevated troponin-I, and BNP associated with increased in-hospital mortality after ICH. Blood pressure control after ICH aims to preserve cerebral perfusion pressure and maintain systolic blood pressure between 140 and 179 mm Hg, and avoid intensive blood pressure reduction (110 to 140 mm Hg). The recipients of ICH donor hearts especially those with reduced ejection fraction experience increased early mortality and graft rejection.

CONCLUSIONS

Various cardiovascular abnormalities are common after spontaneous ICH. The workup of patients with spontaneous ICH should involve 12-lead ECG, cardiac troponin-I, as well as BNP, and echocardiogram to evaluate for heart failure. Blood pressure control with preservation of cerebral perfusion pressure is a cornerstone of hemodynamic management after ICH. The perioperative implications of hemodynamic perturbations after ICH warrant urgent further examination.

Spectral analysis of heart rate variability for trauma outcome prediction: an analysis of 210 ICU multiple trauma patients

PURPOSE

This study aimed to test and compare short-term spectral HRV indices with most used trauma scorings in outcome prediction of multiple trauma, and then to explore the efficacy of their combined application.

METHODS

A prospective study was conducted for patients with blunt multiple trauma admitted to an emergency intensive care unit (ICU) between January 2016 and December 2017. Short-term spectral HRV indices on admission were measured, including normalized low-frequency power (nLF), normalized high-frequency power (nHF), and the nLF/nHF ratio. Injury severity score (ISS), new injury severity score (NISS), and revised trauma score (RTS) were evaluated for each patient, as well as probability of survival (Ps) by trauma and injury severity score (TRISS) model. The primary outcome was 30-day mortality and secondary outcomes were incidence of multiple organ dysfunction syndrome (MODS) and length of ICU stay.

RESULTS

Two hundred and ten patients were recruited. The nLF/nHF ratio, RTS, and Ps_(TRISS) were independent predictors of 30-day mortality, while nLF/nHF, NISS and RTS were independent predictors of MODS. The area under the receiver operating characteristic (ROC) curve (AUC) of nLF/nHF for 30-day mortality prediction was 0.924, comparable to RTS (0.951) and Ps_(TRISS) (0.892). AUC of nLF/nHF-RTS combination was 0.979, significantly greater than that of each alone. Combination of nLF/nHF and Ps_(TRISS) showed an increased AUC (0.984) compared to each of them. The nLF/nHF ratio presented a similar AUC (0.826) to NISS (0.818) or RTS (0.850) for MODS prediction. AUC of nLF/nHF-RTS combination was 0.884, significantly greater than that of nLF/nHF. Combination of nLF/nHF and NISS showed a greater AUC (0.868) than each alone. The nLF/nHF ratio, NISS, RTS, and Ps_(TRISS) were correlated with length of ICU stay for survivors, with correlation coefficients 0.476, 0.617, - 0.588, and - 0.539.

CONCLUSIONS

These findings suggest that the short-term spectral analysis of HRV might be a potential early tool to assess injury severity and predict outcome of multiple trauma. Combination of nLF/nHF and conventional trauma scores can provide more accuracy in outcome prediction of multiple trauma.

Baroreflex sensitivity and heart rate variability are predictors of mortality in patients with aneurysmal subarachnoid haemorrhage

OBJECT

We aimed to investigate the link between the autonomic nervous system (ANS) impairment, assessed using baroreflex sensitivity (BRS) and heart rate variability (HRV) indices, and mortality after aneurysmal subarachnoid haemorrhage (aSAH).

METHODS

A total of 57 patients (56 ± 18 years) diagnosed with aSAH were retrospectively enrolled in the study, where 25% of patients died in the hospital. BRS was calculated using a modified cross-correlation method. Time- and frequency-domain HRV indices were calculated from a time-series of systolic peak intervals of arterial blood pressure signals. Additionally, cerebral autoregulation (CA) was assessed using the mean velocity index (Mxa), where Mxa > 0 indicates impaired CA.

RESULTS

Both BRS and HRV indices were lower in non-survivors than in survivors. The patients with disturbed BRS and HRV had more extensive haemorrhage in the H-H scale (p = .040) and were more likely to die (p = .013) when compared to patients with the intact ANS. The logistic regression model for mortality included: the APACHE II score (p = .002; OR 0.794) and the normalised high frequency power of the HRV (p < <.001; OR 0.636). A positive relationship was found between the Mxa and BRS (R = 0.48, p = .003), which suggests that increasing BRS is moderately strongly associated with worsening CA.

CONCLUSION

Our results indicated that lower values of HRV indices and BRS correlate with mortality and that there is a link between cerebral dysautoregulation and the analysed estimates of the ANS in aSAH patients.

Heart rate variability is associated with outcome in spontaneous intracerebral hemorrhage

PURPOSE

Autonomic imbalance as measured by heart rate variability (HRV) has been associated with poor outcome after stroke. Observations on HRV changes in intracerebral hemorrhage (ICH) are scarce. Here, we aimed to investigate HRV in ICH as compared to a control group and to explore associations with stroke severity, hemorrhage volume and outcome after ICH.

METHODS

We examined the autonomic modulation using frequency domain analysis of HRV during the acute phase of the ICH and in a healthy age- and hypertension-matched control group. Hematoma volume, intraventricular extension, initial stroke severity and baseline demographic, clinical parameters as well as mortality and functional outcome were included in the analysis.

RESULTS

47 patients with ICH and 47 age- and hypertension matched controls were analyzed. ICH patients showed significantly lower total high frequency band (HF) and low frequency band (LF) powers (p = 0.01, p < 0.001), higher normalized HF power (p = 0.03), and lower LF/HF ratio (p < 0.001) as compared to the controls. Autonomic parameters showed associations with stroke severity (p = 0.004) and intraventricular involvement (p = 0.01) and predicted poor outcome independently (p = 0.02).

CONCLUSIONS

Autonomic changes seems to be present in acute ICH and are associated with poor outcome independently. This may have future monitoring and therapeutic implications.

Vagal-immune interactions involved in cholinergic anti-inflammatory pathway

Inflammation and other immune responses are involved in the variety of diseases and disorders. The acute response to endotoxemia includes activation of innate immune mechanisms as well as changes in autonomic nervous activity. The autonomic nervous system and the inflammatory response are intimately linked and sympathetic and vagal nerves are thought to have anti-inflammation functions. The basic functional circuit between vagus nerve and inflammatory response was identified and the neuroimmunomodulation loop was called cholinergic anti-inflammatory pathway. Unique function of vagus nerve in the anti-inflammatory reflex arc was found in many experimental and pre-clinical studies. They brought evidence on the cholinergic signaling interacting with systemic and local inflammation, particularly suppressing immune cells function. Pharmacological/electrical modulation of vagal activity suppressed TNF-alpha and other proinflammatory cytokines production and had beneficial therapeutic effects. Many questions related to mapping, linking and targeting of vagal-immune interactions have been elucidated and brought understanding of its basic physiology and provided the initial support for development of Tracey´s inflammatory reflex. This review summarizes and critically assesses the current knowledge defining cholinergic anti-inflammatory pathway with main focus on studies employing an experimental approach and emphasizes the potential of modulation of vagally-mediated anti-inflammatory pathway in the treatment strategies.

Increased Plasma Levels of Danger-Associated Molecular Patterns Are Associated With Immune Suppression and Postoperative Infections in Patients Undergoing Cytoreductive Surgery and Hyperthermic Intraperitoneal Chemotherapy

Introduction

Danger-associated molecular patterns (DAMPs) can elicit immune responses and may subsequently induce an immune-suppressed state. Previous work showed that increased plasma levels of DAMPs are associated with immune suppression and increased susceptibility toward infections in trauma patients. Like trauma, major surgical procedures, such as cytoreductive surgery (CRS) combined with hyperthermic intraperitoneal chemotherapy (HIPEC), are also thought to cause profound DAMP release. Furthermore, the incidence of postoperative infections in these patients, ranging from 10 to 36%, is very high compared to that observed in patients undergoing other major surgical procedures. We hypothesized that the double hit of surgical trauma (CRS) in combination with HIPEC causes excessive DAMP release, which in turn contributes to the development of immune suppression. To investigate this, we assessed DAMP release in patients undergoing CRS-HIPEC, and investigated its relationship with immune suppression and postoperative infections.

Methods

In 20 patients undergoing CRS-HIPEC, blood was obtained at five time points: just before surgery (baseline), after CRS, after HIPEC, at ICU admission, and 1 day after surgery. Circulating levels of DAMPs [heat shock protein (HSP)70, high mobility group box (HMGB)1, S100A12, S100A8/S100A9, nuclear (n)DNA, mitochondrial (mt)DNA, lactate dehydrogenase (LDH), a marker of unscheduled cell death], and cytokines [tumor necrosis factor (TNF)α, IL-6, IL-8, IL-10, macrophage inflammatory protein (MIP)-1α, MIP-1β, and MCP-1] were measured. The extent of immune suppression was determined by measuring HLA-DR gene expression and ex vivo leukocytic cytokine production capacity.

Results

Plasma levels of DAMPs (maximum fold increases of HSP70: 2.1 [1.5–2.8], HMGB1: 5.9 [3.2–9.8], S100A8/S100A9: 3.6 [1.8–5.6], S100A12: 2.6 [1.8–4.3], nDNA 3.9 [1.0–10.8], LDH 1.7 [1.2–2.5]), and all measured cytokines increased profoundly following CRS-HIPEC. Evidence of immune suppression was already apparent during the procedure, illustrated by a decrease of HLA-DR expression compared with baseline (0.5-fold [0.3–0.9]) and diminished ex vivo pro-inflammatory cytokine production capacity. The increase in HMGB1 levels correlated with the decrease in HLA-DR expression (r = −0.46, p = 0.04), and peak HMGB1 concentrations were significantly higher in the five patients who went on to develop a postoperative infection (p = 0.04).

Conclusion

CRS-HIPEC is associated with profound DAMP release and immune suppression, and plasma HMGB1 levels are related with the occurrence of postoperative infections in these patients.

Release of Danger-Associated Molecular Patterns following Chemotherapy Does Not Induce Immunoparalysis in Leukemia Patients

Chemotherapy may result in the release of danger-associated molecular patterns (DAMPs), which can cause immunoparalysis (deactivation of the immune system). We investigated DAMPs following chemotherapy and their relationship with markers of immunoparalysis in leukemia patients. In 6 patients with acute myeloid leukemia or myelodysplastic syndrome and 12 healthy subjects, DAMPs, cytokines, and markers of immunoparalysis were determined before and during the first week after chemotherapy initiation. In the patients, plasma levels of nuclear DNA (a marker of general DAMP release) were profoundly increased before chemotherapy and further increased 4-6 h afterwards, while the specific DAMP mitochondrial DNA showed only a trend towards increase. Circulating cytokine levels did not change following chemotherapy. Leukocyte cytokine production capacity and HLA-DR expression were similar in patients and healthy controls until day 4 when leukocytes were found to be virtually absent. In conclusion, in the early phase following chemotherapy in leukemia patients, increased DAMP release does not induce immunoparalysis.

Autonomic Impairment in Severe Traumatic Brain Injury: A Multimodal Neuromonitoring Study

OBJECTIVES

Autonomic impairment after acute traumatic brain injury has been associated independently with both increased morbidity and mortality. Links between autonomic impairment and increased intracranial pressure or impaired cerebral autoregulation have been described as well. However, relationships between autonomic impairment, intracranial pressure, impaired cerebral autoregulation, and outcome remain poorly explored. Using continuous measurements of heart rate variability and baroreflex sensitivity we aimed to test whether autonomic markers are associated with functional outcome and mortality independently of intracranial variables. Further, we aimed to evaluate the relationships between autonomic functions, intracranial pressure, and cerebral autoregulation.

DESIGN

Retrospective analysis of a prospective database.

SETTING

Neurocritical care unit in a university hospital.

SUBJECTS

Sedated patients with severe traumatic brain injury.

MEASUREMENTS AND MAIN RESULTS

Waveforms of intracranial pressure and arterial blood pressure, baseline Glasgow Coma Scale and 6 months Glasgow Outcome Scale were recorded. Baroreflex sensitivity was assessed every 10 seconds using a modified cross-correlational method. Frequency domain analyses of heart rate variability were performed automatically every 10 seconds from a moving 300 seconds of the monitoring time window. Mean values of baroreflex sensitivity, heart rate variability, intracranial pressure, arterial blood pressure, cerebral perfusion pressure, and impaired cerebral autoregulation over the entire monitoring period were calculated for each patient. Two hundred and sixty-two patients with a median age of 36 years entered the analysis. The median admission Glasgow Coma Scale was 6, the median Glasgow Outcome Scale was 3, and the mortality at 6 months was 23%. Baroreflex sensitivity (adjusted odds ratio, 0.9; p = 0.02) and relative power of a high frequency band of heart rate variability (adjusted odds ratio, 1.05; p < 0.001) were individually associated with mortality, independently of age, admission Glasgow Coma Scale, intracranial pressure, pressure reactivity index, or cerebral perfusion pressure. Baroreflex sensitivity showed no correlation with intracranial pressure or cerebral perfusion pressure; the correlation with pressure reactivity index was strong in older patients (age, > 60 yr). The relative power of high frequency correlated significantly with intracranial pressure and cerebral perfusion pressure, but not with pressure reactivity index. The relative power of low frequency correlated significantly with pressure reactivity index.

CONCLUSIONS

Autonomic impairment, as measured by heart rate variability and baroreflex sensitivity, is significantly associated with increased mortality after traumatic brain injury. These effects, though partially interlinked, seem to be independent of age, trauma severity, intracranial pressure, or autoregulatory status, and thus represent a discrete phenomenon in the pathophysiology of traumatic brain injury. Continuous measurements of heart rate variability and baroreflex sensitivity in the neuromonitoring setting of severe traumatic brain injury may carry novel pathophysiological and predictive information.

Alterations in nitric oxide homeostasis during traumatic brain injury

Changes in nitric oxide (NO) levels have been often associated with various forms of trauma, including secondary damage after traumatic brain injury (TBI). Several studies demonstrate the upregulation of NO synthase (NOS) enzymes, and concomitant increases in brain NO levels, which contribute to the TBI-associated glutamate cytotoxicity, including the pathogenesis of mitochondrial dysfunction. TBI is also associated with elevated NO levels in remote organs, indicating that TBI can induce systemic changes in NO regulation, which can be either beneficial or detrimental. Here we review the possible mechanisms responsible for changes in NO metabolism during TBI. Better understanding of the changes in NO homeostasis in TBI will be necessary to design rational therapeutic approaches for TBI. This article is part of a Special Issue entitled: Immune and Metabolic Alterations in Trauma and Sepsis edited by Dr. Raghavan Raju.

Plasma levels of danger-associated molecular patterns are associated with immune suppression in trauma patients

PURPOSE

Danger-associated molecular patterns (DAMPs) released of trauma could contribute to an immune suppressed state that renders patients vulnerable towards nosocomial infections. We investigated DAMP release in trauma patients, starting in the prehospital phase, and assessed its relationship with immune suppression and nosocomial infections.

METHODS

Blood was obtained from 166 adult trauma patients at the trauma scene, emergency room (ER), and serially afterwards. Circulating levels of DAMPs and cytokines were determined. Immune suppression was investigated by determination of HLA-DRA gene expression and ex vivo lipopolysaccharide-stimulated cytokine production.

RESULTS

Compared with healthy controls, plasma levels of nuclear DNA (nDNA) and heat shock protein-70 (HSP70) but not mitochondrial DNA were profoundly increased immediately following trauma and remained elevated for 10 days. Plasma cytokines were increased at the ER, and levels of anti-inflammatory IL-10 but not of pro-inflammatory cytokines peaked at this early time-point. HLA-DRA expression was attenuated directly after trauma and did not recover during the follow-up period. Plasma nDNA (r = -0.24, p = 0.006) and HSP70 (r = -0.38, p < 0.0001) levels correlated negatively with HLA-DRA expression. Ex vivo cytokine production revealed an anti-inflammatory phenotype already at the trauma scene which persisted in the following days, characterized by attenuated TNF-α and IL-6, and increased IL-10 production. Finally, higher concentrations of nDNA and a further decrease of HLA-DRA expression were associated with infections.

CONCLUSIONS

Plasma levels of DAMPs are associated with immune suppression, which is apparent within minutes/hours following trauma. Furthermore, aggravated immune suppression during the initial phase following trauma is associated with increased susceptibility towards infections.

Respiratory mechanics in brain injury: A review

Several clinical and experimental studies have shown that lung injury occurs shortly after brain damage. The responsible mechanisms involve neurogenic pulmonary edema, inflammation, the harmful action of neurotransmitters, or autonomic system dysfunction. Mechanical ventilation, an essential component of life support in brain-damaged patients (BD), may be an additional traumatic factor to the already injured or susceptible to injury lungs of these patients thus worsening lung injury, in case that non lung protective ventilator settings are applied. Measurement of respiratory mechanics in BD patients, as well as assessment of their evolution during mechanical ventilation, may lead to preclinical lung injury detection early enough, allowing thus the selection of the appropriate ventilator settings to avoid ventilator-induced lung injury. The aim of this review is to explore the mechanical properties of the respiratory system in BD patients along with the underlying mechanisms, and to translate the evidence of animal and clinical studies into therapeutic implications regarding the mechanical ventilation of these critically ill patients.

The Involvement of Danger-Associated Molecular Patterns in the Development of Immunoparalysis in Cardiac Arrest Patients

OBJECTIVES

After cardiac arrest, patients are highly vulnerable toward infections, possibly due to a suppressed state of the immune system called "immunoparalysis." We investigated if immunoparalysis develops following cardiac arrest and whether the release of danger-associated molecular patterns could be involved.

DESIGN

Observational study.

SETTING

ICU of a university medical center.

PATIENTS

Fourteen post-cardiac arrest patients treated with mild therapeutic hypothermia for 24 hours and 11 control subjects.

MEASUREMENTS AND MAIN RESULTS

Plasma cytokines showed highest levels within 24 hours after cardiac arrest and decreased during the next 2 days. By contrast, ex vivo production of cytokines interleukin-6, tumor necrosis factor-α, and interleukin-10 by lipopolysaccharide-stimulated leukocytes was severely impaired compared with control subjects, with most profound effects observed at day 0, and only partially recovering afterward. Compared with incubation at 37°C, incubation at 32°C resulted in higher interleukin-6 and lower interleukin-10 production by lipopolysaccharide-stimulated leukocytes of control subjects, but not of patients. Plasma nuclear DNA, used as a marker for general danger-associated molecular pattern release, and the specific danger-associated molecular patterns (EN-RAGE and heat shock protein 70) were substantially higher in patients at days 0 and 1 compared with control subjects. Furthermore, plasma heat shock protein 70 levels were negatively correlated with ex vivo production of inflammatory mediators interleukin-6, tumor necrosis factor-α, and interleukin-10. Extracellular newly identified receptor for advanced glycation end products-binding protein levels only showed a significant negative correlation with ex vivo production of interleukin-6 and tumor necrosis factor-α and a borderline significant inverse correlation with interleukin-10. No significant correlations were observed between plasma nuclear DNA levels and ex vivo cytokine production.

INTERVENTIONS

None.

CONCLUSIONS

Release of danger-associated molecular patterns during the first days after cardiac arrest is associated with the development of immunoparalysis. This could explain the increased susceptibility toward infections in cardiac arrest patients.

Whole body periodic acceleration (pGz) preserves heart rate variability after cardiac arrest

AIMS

Heart rate variability (HRV) is a measure of the balance between the sympathetic and parasympathetic autonomic nervous system and lack thereof an ominous sign in many cardiac and neurological conditions including post-cardiac arrest syndrome. Whole body periodic acceleration (pGz) has been shown to be cardio protective when applied prior to during and after cardiac arrest (CA). Here, we investigate whether or not pGz pre or post treatment after CA preserves HRV.

METHODS

Eight min of unsupported ventricular fibrillation followed by CPR and defibrillation was carried out in 32 anesthetized and paralyzed male swine who were randomized to pretreatment (1h pGz prior to CA, pre-pGz [n=8]) or post-treatment (pGz beginning at 30min after return of spontaneous circulation ([ROSC], post-pGz [n=8]) or none (CONT [n=8]). pGz was applied together with conventional mechanical ventilation. In a separate group (n=8), infusion of TRIM (nNOS inhibitor) was used to determine the effects of nNOS inhibition on HRV.

RESULTS

Time and frequency domain measures of HRV were determined along with measurements of blood gases and hemodynamics, obtained at baseline and at 30, 60, 120 and 180min after ROSC. All animals had ROSC and there were no significant differences for arterial blood gases, mean blood pressure and coronary perfusion pressure after ROSC among the groups. HRV was significantly depressed after cardiac arrest and remained depressed in CONT group. In contrast, both pre and post pGz treated groups had significantly higher and preserved time domain measures of HRV (RMSSD and SDNN) from 60 to 180min after ROSC, and nNOS inhibition markedly reduced HRV. The frequency domain of HRV did not show changes.

CONCLUSIONS

In a pig model of CA, pre or post treatment with pGz preserves HRV. Inhibition of nNOS markedly reduced HRV. Post-treatment with pGz is a novel therapeutic strategy that might serve as an adjunct to current pharmacological or hypothermia modalities to potentially improve outcomes from post-cardiac arrest syndrome.

Short-term hyperoxia does not exert immunologic effects during experimental murine and human endotoxemia

Oxygen therapy to maintain tissue oxygenation is one of the cornerstones of critical care. Therefore, hyperoxia is often encountered in critically ill patients. Epidemiologic studies have demonstrated that hyperoxia may affect outcome, although mechanisms are unclear. Immunologic effects might be involved, as hyperoxia was shown to attenuate inflammation and organ damage in preclinical models. However, it remains unclear whether these observations can be ascribed to direct immunosuppressive effects of hyperoxia or to preserved tissue oxygenation. In contrast to these putative anti-inflammatory effects, hyperoxia may elicit an inflammatory response and organ damage in itself, known as oxygen toxicity. Here, we demonstrate that, in the absence of systemic inflammation, short-term hyperoxia (100% O2 for 2.5 hours in mice and 3.5 hours in humans) does not result in increased levels of inflammatory cytokines in both mice and healthy volunteers. Furthermore, we show that, compared with room air, hyperoxia does not affect the systemic inflammatory response elicited by administration of bacterial endotoxin in mice and man. Finally, neutrophil phagocytosis and ROS generation are unaffected by short-term hyperoxia. Our results indicate that hyperoxia does not exert direct anti-inflammatory effects and temper expectations of using it as an immunomodulatory treatment strategy.

Ventilator-associated Pneumonia caused by commensal oropharyngeal Flora; [corrected] a retrospective Analysis of a prospectively collected Database

Background

The significance of commensal oropharyngeal flora (COF) as a potential cause of ventilator-associated pneumonia (VAP) is scarcely investigated and consequently unknown. Therefore, the aim of this study was to explore whether COF may cause VAP.

Methods

Retrospective clinical, microbiological and radiographic analysis of all prospectively collected suspected VAP cases in which bronchoalveolar lavage fluid exclusively yielded ≥ 10⁴ cfu/ml COF during a 9.5-year period. Characteristics of 899 recent intensive care unit (ICU) admissions were used as a reference population.

Results

Out of the prospectively collected database containing 159 VAP cases, 23 patients were included. In these patients, VAP developed after a median of 8 days of mechanical ventilation. The patients faced a prolonged total ICU length of stay (35 days [P < .001]), hospital length of stay (45 days [P = .001]), and a trend to higher mortality (39 % vs. 26 %, [P = .158]; standardized mortality ratio 1.26 vs. 0.77, [P = .137]) compared to the reference population. After clinical, microbiological and radiographic analysis, COF was the most likely cause of respiratory deterioration in 15 patients (9.4 % of all VAP cases) and a possible cause in 2 patients.

Conclusion

Commensal oropharyngeal flora appears to be a potential cause of VAP in limited numbers of ICU patients as is probably associated with an increased length of stay in both ICU and hospital. As COF-VAP develops late in the course of ICU admission, it is possibly associated with the immunocompromised status of ICU patients.

Innate immune function predicts the development of nosocomial infection in critically injured children

BACKGROUND

Critical injury has been associated with reduction in innate immune function in adults, with infection risk being related to degree of immune suppression. This relationship has not been reported in critically injured children.

HYPOTHESIS

Innate immune function will be reduced in critically injured children, and the degree of reduction will predict the subsequent development of nosocomial infection.

METHODS

Children (≤18 years old) were enrolled in this longitudinal, prospective, observational, single-center study after admission to the pediatric intensive care unit following critical injury, along with a cohort of outpatient controls. Serial blood sampling was performed to evaluate plasma cytokine levels and innate immune function as measured by ex vivo lipopolysaccharide-induced tumor necrosis factor α (TNF-α) production capacity.

RESULTS

Seventy-six critically injured children (and 21 outpatient controls) were enrolled. Sixteen critically injured subjects developed nosocomial infection. Those subjects had higher plasma interleukin 6 and interleukin 10 levels on posttrauma days 1-2 compared with those who recovered without infection and outpatient controls. Ex vivo lipopolysaccharide-induced TNF-α production capacity was lower on posttrauma days 1-2 (P = 0.006) and over the first week following injury (P = 0.04) in those who went on to develop infection. A TNF-α response of less than 520 pg/mL at any time in the first week after injury was highly associated with infection risk by univariate and multivariate analysis. Among transfused children, longer red blood cell storage age, not transfusion volume, was associated with lower innate immune function (P < 0.0001). Trauma-induced innate immune suppression was reversible ex vivo via coculture of whole blood with granulocyte-macrophage colony-stimulating factor.

CONCLUSIONS

Trauma-induced innate immune suppression is common in critically injured children and is associated with increased risks for the development of nosocomial infection. Potential exacerbating factors, including red blood cell transfusion, and potential therapies for pediatric trauma-induced innate immune suppression are deserving of further study.

Transvenous vagus nerve stimulation does not modulate the innate immune response during experimental human endotoxemia: a randomized controlled study

INTRODUCTION

Vagus nerve stimulation (VNS) exerts beneficial anti-inflammatory effects in various animal models of inflammation, including collagen-induced arthritis, and is implicated in representing a novel therapy for rheumatoid arthritis. However, evidence of anti-inflammatory effects of VNS in humans is very scarce. Transvenous VNS (tVNS) is a newly developed and less invasive method to stimulate the vagus nerve. In the present study, we determined whether tVNS is a feasible and safe procedure and investigated its putative anti-inflammatory effects during experimental human endotoxemia.

METHODS

We performed a randomized double-blind sham-controlled study in healthy male volunteers. A stimulation catheter was inserted in the left internal jugular vein at spinal level C5-C7, adjacent to the vagus nerve. In the tVNS group (n = 10), stimulation was continuously performed for 30 minutes (0-10 V, 1 ms, 20 Hz), starting 10 minutes before intravenous administration of 2 ng kg(-1) Escherichia coli lipopolysaccharide (LPS). Sham-instrumented subjects (n = 10) received no electrical stimulation.

RESULTS

No serious adverse events occurred throughout the study. In the tVNS group, stimulation of the vagus nerve was achieved as indicated by laryngeal vibration. Endotoxemia resulted in fever, flu-like symptoms, and hemodynamic changes that were unaffected by tVNS. Furthermore, plasma levels of inflammatory cytokines increased sharply during endotoxemia, but responses were similar between groups. Finally, cytokine production by leukocytes stimulated with LPS ex vivo, as well as neutrophil phagocytosis capacity, were not influenced by tVNS.

CONCLUSIONS

tVNS is feasible and safe, but does not modulate the innate immune response in humans in vivo during experimental human endotoxemia.

TRIAL REGISTRATION

Clinicaltrials.gov NCT01944228. Registered 12 September 2013.

Substance P mediates reduced pneumonia rates after traumatic brain injury

OBJECTIVES

Traumatic brain injury results in significant morbidity and mortality and is associated with infectious complications, particularly pneumonia. However, whether traumatic brain injury directly impacts the host response to pneumonia is unknown. The objective of this study was to determine the nature of the relationship between traumatic brain injury and the prevalence of pneumonia in trauma patients and investigate the mechanism of this relationship using a murine model of traumatic brain injury with pneumonia.

DESIGN

Data from the National Trauma Data Bank and a murine model of traumatic brain injury with postinjury pneumonia.

SETTING

Academic medical centers in Cincinnati, OH, and Boston, MA.

PATIENTS/SUBJECTS

Trauma patients in the National Trauma Data Bank with a hospital length of stay greater than 2 days, age of at least 18 years at admission, and a blunt mechanism of injury. Subjects were female ICR mice 8-10 weeks old.

INTERVENTIONS

Administration of a substance P receptor antagonist in mice.

MEASUREMENTS AND MAIN RESULTS

Pneumonia rates were measured in trauma patients before and after risk adjustment using propensity scoring. In addition, survival and pulmonary inflammation were measured in mice undergoing traumatic brain injury with or without pneumonia. After risk adjustment, we found that traumatic brain injury patients had significantly lower rates of pneumonia compared to blunt trauma patients without traumatic brain injury. A murine model of traumatic brain injury reproduced these clinical findings with mice subjected to traumatic brain injury demonstrating increased bacterial clearance and survival after induction of pneumonia. To determine the mechanisms responsible for this improvement, the substance P receptor was blocked in mice after traumatic brain injury. This treatment abrogated the traumatic brain injury-associated increases in bacterial clearance and survival.

CONCLUSIONS

The data demonstrate that patients with traumatic brain injury have lower rates of pneumonia compared to non-head-injured trauma patients and suggest that the mechanism of this effect occurs through traumatic brain injury-induced release of substance P, which improves innate immunity to decrease pneumonia.

CNS-disease affecting the heart: brain-heart disorders

There are a number of hereditary and non-hereditary central nervous system (CNS) disorders, which directly or indirectly affect the heart (brain-heart disorders). The most well-known of these CNS-disorders are epilepsy, stroke, subarachanoid bleeding, bacterial meningitis, and head injury. In addition, a number of hereditary and non-hereditary neurodegenerative disorders may impair cardiac functions. Affection of the heart may manifest as arrhythmias, cardiomyopathy, or autonomic dysfunction. Rarer cardiac complications of CNS disorders include heart failure, systolic or diastolic dysfunction, myocardial infarction, arterial hypertension, or pulmonary hypertension. Cardiomyopathy induced by hereditary CNS disease mainly include stress-induced myocardial dysfunction, known as Takotsubo syndrome (TTS). CNS disease triggering TTS includes epilepsy, ischemic stroke, subarachnoid bleeding, or PRES syndrome. Arrhythmias induced by hereditary CNS disease include supraventricular or ventricular arrhythmias leading to palpitations, dizziness, vertigo, fainting, syncope, (near) sudden cardiac death, or sudden unexplained death in epilepsy (SUDEP). Appropriate management of cardiac involvement in CNS-disorders is essential to improve outcome of affected patients.

Abnormal heart rate characteristics are associated with abnormal neuroimaging and outcomes in extremely low birth weight infants

OBJECTIVE

Brain injury in preterm infants may lead to an inflammatory response and central nervous system dysfunction reflected by abnormal heart rate characteristics (HRC). We hypothesized that a continuously monitored HRC index reflecting reduced HR variability and decelerations correlates with abnormal neuroimaging and outcomes in extremely low birth weight infants (ELBW).

STUDY DESIGN

We analyzed the average HRC index within 28 days after birth (aHRC28) and head ultrasound (HUS) in 384 ELBW infants. In 50 infants with brain magnetic resonance imaging (MRI) and 70 infants with Bayley neurodevelopmental testing at 1 year of age, we analyzed the relationship between aHRC28, MRI abnormalities and low Bayley scores.

RESULT

aHRC28 was higher in infants with severe HUS abnormalities (2.65±1.27 for Grade III-IV intraventricular hemorrhage (IVH) or cystic periventricular leukomalacia (cPVL) versus 1.72±0.95 for normal or Grade I-II IVH, P<0.001). Higher aHRC28 was also associated with white matter damage on MRI and death or Bayley motor or mental developmental index <70. Associations persisted after adjusting for gestational age, birth weight and septicemia. For every one point increase in aHRC28, the odds ratio of death or Bayley score <70 was 2.45 (95% CI 1.46, 4.05, P<0.001).

CONCLUSION

A continuously monitored HRC index provides an objective, noninvasive measure associated with abnormal brain imaging and adverse neurologic outcomes in ELBW infants.

Traumatic brain injury in rats induces lung injury and systemic immune suppression

Traumatic brain injury (TBI) is frequently complicated by acute lung injury, which is predictive for poor outcome. However, it is unclear whether lung injury develops independently or as a result of mechanical ventilation after TBI. Further, TBI is strongly associated with the development of pneumonia, suggesting a specific vulnerability for the development of nosocomial infections in the lung after TBI. In this study, we evaluated whether indeed pulmonary injury and immune suppression develop spontaneously in an animal model of mild TBI (mTBI). TBI was induced in male PVG rats by closed-head trauma using a weight-drop device. Subsequently, we evaluated the effects of this on the lungs as well as on the excitability of the systemic immune system. Finally, we performed an experiment in which TBI was followed by induction of pneumonitis and evaluated whether TBI affects the severity of subsequent pneumonitis induced by intratracheal instillation of heat-killed Staphylococcus aureus. mTBI resulted in significant lung injury, as evidenced by pulmonary edema, protein leakage to the alveolar compartment, and increased concentrations of interleukin-1 and -6 in broncho alveolar lavage fluid (all p<0.05 vs. sham-treated animals). Further, after TBI, the release of tumor necrosis factor alpha was decreased when whole blood was stimulated ex vivo (p<0.05 TBI vs. sham), indicating systemic immune suppression. When TBI was followed by pneumonitis, the severity of subsequent pneumonitis was not different in rats previously subjected to TBI or sham treatment (p>0.05), suggesting that systemic immune suppression is not translated toward the pulmonary compartment in this specific model. We here show that during mild experimental TBI, acute pulmonary injury, as well as a decrease in the excitability of the systemic immune system, can be observed.

Heart rate before ICU discharge: a simple and readily available predictor of short- and long-term mortality from critical illness

PURPOSE

A heart rate >90 bpm serves as one of four characteristics defining the systemic inflammatory response syndrome and is used in scoring systems to predict in-hospital mortality of intensive care unit (ICU) patients. Despite its central role in critical illness, specific data regarding the relationship between heart rate and outcome are rare.

METHODS

In this post hoc analysis of a prospectively collected database, we analyzed the value of heart rate averaged from four predefined time points during the last 24 h before ICU discharge as a predictor of post-ICU in-hospital and post-hospital mortality in medical ICU patients. Furthermore, the relationship between heart rate and inflammation, as well as the influence of rate control medications on the association between heart rate and outcome were identified.

RESULTS

Among the 702 ICU patients discharged from the ICU, 7.1 % died before hospital discharge. At 4 years of follow-up, post-hospital mortality was 14.4 %. Multivariate Cox proportional hazards models revealed heart rate before ICU discharge (HR 5.95; 95 % CI 1.24-28.63; p = 0.03) as an independent predictor of post-ICU in-hospital mortality. Both heart rate (HR 2.56; 95 % CI, 1.05-6.34; p = 0.04) and the C-reactive protein serum concentration before ICU discharge (HR, 1.26; 95 % CI, 1.09-1.46; p = 0.002) were independently associated with post-hospital mortality. Heart rate control therapy reduced the risk of post-ICU in-hospital (HR 0.38; 95 % CI, 0.18-0.81; p = 0.01) and post-hospital (HR, 0.47; 95 % CI, 0.22-1.00; p = 0.05) mortality.

CONCLUSION

Heart rate evaluated 24 h before ICU discharge was independently associated with post-ICU in-hospital and post-hospital mortality. Pharmacological interventions to control heart rate may beneficially influence post-ICU mortality.