Dysfunction of vasomotor reactivity in severe sepsis and septic shock

Estimated Cerebral Perfusion Pressure and Intracranial Pressure in Septic Patients

BACKGROUND

Sepsis-associated brain dysfunction (SABD) is frequent and is associated with poor outcome. Changes in brain hemodynamics remain poorly described in this setting. The aim of this study was to investigate the alterations of cerebral perfusion pressure and intracranial pressure in a cohort of septic patients.

METHODS

We conducted a retrospective analysis of prospectively collected data in septic adults admitted to our intensive care unit (ICU). We included patients in whom transcranial Doppler recording performed within 48 h from diagnosis of sepsis was available. Exclusion criteria were intracranial disease, known vascular stenosis, cardiac arrhythmias, pacemaker, mechanical cardiac support, severe hypotension, and severe hypocapnia or hypercapnia. SABD was clinically diagnosed by the attending physician, anytime during the ICU stay. Estimated cerebral perfusion pressure (eCPP) and estimated intracranial pressure (eICP) were calculated from the blood flow velocity of the middle cerebral artery and invasive arterial pressure using a previously validated formula. Normal eCPP was defined as eCPP ≥ 60 mm Hg, low eCPP was defined as eCPP < 60 mm Hg; normal eICP was defined as eICP ≤ 20 mm Hg, and high eICP was defined as eICP > 20 mm Hg.

RESULTS

A total of 132 patients were included in the final analysis (71% male, median [interquartile range (IQR)] age was 64 [52-71] years, median [IQR] Acute Physiology and Chronic Health Evaluation II score on admission was 21 [15-28]). Sixty-nine (49%) patients developed SABD during the ICU stay, and 38 (29%) were dead at hospital discharge. Transcranial Doppler recording lasted 9 (IQR 7-12) min. Median (IQR) eCPP was 63 (58-71) mm Hg in the cohort; 44 of 132 (33%) patients had low eCPP. Median (IQR) eICP was 8 (4-13) mm Hg; five (4%) patients had high eICP. SABD occurrence and in-hospital mortality did not differ between patients with normal eCPP and patients with low eCPP or between patients with normal eICP and patients with high eICP. Eighty-six (65%) patients had normal eCPP and normal eICP, 41 (31%) patients had low eCPP and normal eICP, three (2%) patients had low eCPP and high eICP, and two (2%) patients had normal eCPP and high eICP; however, SABD occurrence and in-hospital mortality were not significantly different among these subgroups.

CONCLUSIONS

Brain hemodynamics, in particular CPP, were altered in one third of critically ill septic patients at a steady state of monitoring performed early during the course of sepsis. However, these alterations were equally common in patients who developed or did not develop SABD during the ICU stay and in patients with favorable or unfavorable outcome.

Treating the body to prevent brain injury: lessons learned from the coronavirus disease 2019 pandemic

PURPOSE OF REVIEW

We aim to provide the current evidence on utility and application of neuromonitoring tools including electroencephalography (EEG), transcranial Doppler (TCD), pupillometry, optic nerve sheath diameter (ONSD), cerebral near-infrared spectroscopy (cNIRS), somatosensory-evoked potentials (SSEPs), and invasive intracranial monitoring in COVID-19. We also provide recent evidence on management strategy of COVID-19-associated neurological complications.

RECENT FINDINGS

Despite the common occurrence of neurological complications, we found limited use of standard neurologic monitoring in patients with COVID-19. No specific EEG pattern was identified in COVID-19. Frontal epileptic discharge was proposed to be a potential marker of COVID-19 encephalopathy. TCD, ONSD, and pupillometry can provide real-time data on intracranial pressure. Additionally, TCD may be useful for detection of acute large vessel occlusions, abnormal cerebral hemodynamics, cerebral emboli, and evolving cerebral edema at bedside. cNIRS was under-utilized in COVID-19 population and there are ongoing studies to investigate whether cerebral oxygenation could be a more useful parameter than peripheral oxygen saturation to guide clinical titration of permissive hypoxemia. Limited data exists on SSEPs and invasive intracranial monitoring.

SUMMARY

Early recognition using standardized neuromonitoring and timely intervention is important to reduce morbidity and mortality. The management strategy for neurological complications is similar to those without COVID-19.

Sepsis-Related Brain MRI Abnormalities Are Associated With Mortality and Poor Neurological Outcome in Pediatric Sepsis

BACKGROUND

It is not known whether brain magnetic resonance imaging (MRI) abnormalities in pediatric sepsis are associated with clinical outcomes. Study objectives were to (1) determine the prevalence and type of sepsis-related neuroimaging abnormalities evident on clinically indicated brain MRI in children with sepsis and (2) test the association of these abnormalities with mortality, new disability, length of stay (LOS), and MRI indication.

METHODS

Retrospective cohort study of 140 pediatric patients with sepsis and a clinically indicated brain MRI obtained within 60 days of sepsis onset at a single, large academic pediatric intensive care unit (PICU). Two radiologists systematically reviewed the first post-sepsis brain MRI and determined which abnormalities were sepsis-related. Outcomes compared in patients with versus without sepsis-related MRI abnormalities.

RESULTS

PICU mortality was 7%. Thirty patients had one or more sepsis-related MRI abnormality, yielding a prevalence of 21% (95% confidence interval 15%, 28%). Among those, 53% (16 of 30) had sepsis-related white matter signal abnormalities; 53% (16 of 30) sepsis-related ischemia, infarction, or thrombosis; and 27% (eight of 30) sepsis-related posterior reversible encephalopathy. Patients with one or more sepsis-related MRI abnormality had increased mortality (17% vs 5%; P = 0.04), new neurological disability at PICU discharge (32% vs 11%; P = 0.03), and longer PICU LOS (median 18 vs 11 days; P = 0.04) compared with patients without.

CONCLUSIONS

In children with sepsis and a clinically indicated brain MRI, 21% had a sepsis-related MRI abnormality. Sepsis-related MRI abnormalities were associated with increased mortality, new neurological disability, and longer PICU LOS.

Dynamic Autoregulation is Impaired in Circulatory Shock

BACKGROUND

Circulatory shock is a life-threatening disorder that is associated with high mortality, with a state of systemic and tissue hypoperfusion that can lead to organ failure, including the brain, where altered mental state is often observed. We hypothesized that cerebral autoregulation (CA) is impaired in patients with circulatory shock.

METHODS

Adult patients with circulatory shock and healthy controls were included. Cerebral blood flow velocity (CBFV, transcranial Doppler ultrasound) and arterial blood pressure (BP, Finometer or intra-arterial line) were continuously recorded during 5 min in both groups. Autoregulation Index (ARI) was estimated from the CBFV response to a step change in BP, derived by transfer function analysis; ARI ≤ 4 was considered impaired CA. The relationship between organ dysfunction, assessed with the Sequential Organ Failure Assessment (SOFA) score and the ARI, was assessed with linear regression.

RESULTS

Twenty-five shock patients and 28 age-matched healthy volunteers were studied. The mean ± SD SOFA score was 10.8 ± 4.3. Shock patients compared with control subjects had lower ARI values (4.0 ± 2.1 vs. 5.9 ± 1.5, P = 0.001). Impaired CA was more common in shock patients (44.4% vs. 7.1%, P = 0.003). There was a significant inverse relationship between the ARI and the SOFA score (R = -0.63, P = 0.0008).

CONCLUSIONS

These results suggest that circulatory shock is often associated with impaired CA and that the severity of CA alterations is correlated with the degree of multiple organ failure, reinforcing the need to monitor cerebral hemodynamics in patients with circulatory shock.

Endothelial Dysfunction and Impaired Neurovascular Coupling Responses Precede Cognitive Impairment in a Mouse Model of Geriatric Sepsis

Sepsis is a life-threatening condition, the incidence of which is significantly increased in elderly patients. One of the long-lasting effects of sepsis is cognitive impairment defined as a new deficit or exacerbation of preexisting deficits in global cognition or executive function. Normal brain function is dependent on moment-to-moment adjustment of cerebral blood flow to match the increased demands of active brain regions. This homeostatic mechanism, termed neurovascular coupling (NVC, also known as functional hyperemia), is critically dependent on the production of vasodilator NO by microvascular endothelial cells in response to mediators released from activated astrocytes. The goal of this study was to test the hypothesis that sepsis in aging leads to impairment of NVC responses early after treatment and that this neurovascular dysfunction associates with impairments in cognitive performance and vascular endothelial dysfunction. To test this hypothesis, we used a commonly studied bacterial pathogen, Listeria monocytogenes, to induce sepsis in experimental animals (males, 24 months of age) and subjected experimental animals to a standard clinical protocol of 3 doses of ampicillin i.p. and 14 days of amoxicillin added to the drinking water. NVC responses, endothelial function and cognitive performance were measured in septic and age-matched control groups within 14 days after the final antibiotic treatment. Our data demonstrate that sepsis in aging significantly impairs NVC responses measured in somatosensory cortex during whisker stimulation, significantly impairs endothelial function in isolated and pressure cannulated aorta rings in response to acetylcholine stimulation. No significant impairment of cognitive function in post-sepsis aged animals has been observed when measured using the PhenoTyper homecage based system. Our findings suggest that sepsis-associated endothelial dysfunction and impairment of NVC responses may contribute to long-term cognitive deficits in older sepsis survivors.

Cerebral autoregulation and neurovascular coupling are progressively impaired during septic shock: an experimental study

Background

Alteration of the mechanisms of cerebral blood flow (CBF) regulation might contribute to the pathophysiology of sepsis-associated encephalopathy (SAE). However, previous clinical studies on dynamic cerebral autoregulation (dCA) in sepsis had several cofounders. Furthermore, little is known on the potential impairment of neurovascular coupling (NVC) in sepsis. The aim of our study was to determine the presence and time course of dCA and NVC alterations in a clinically relevant animal model and their potential impact on the development of SAE.

Methods

Thirty-six anesthetized, mechanically ventilated female sheep were randomized to sham procedures (sham, n = 15), sepsis (n = 14), or septic shock (n = 7). Blood pressure, CBF, and electrocorticography were continuously recorded. Pearson’s correlation coefficient Lxa and transfer function analysis were used to estimate dCA. NVC was assessed by the analysis of CBF variations induced by cortical gamma activity (Eγ) peaks and by the magnitude-squared coherence (MSC) between the spontaneous fluctuations of CBF and Eγ. Cortical function was estimated by the alpha-delta ratio. Wilcoxon signed rank and rank sum tests, Friedman tests, and RMANOVA test were used as appropriate.

Results

Sepsis and sham animals did not differ neither in dCA nor in NVC parameters. A significant impairment of dCA occurred only after septic shock (Lxa, p = 0.03, TFA gain p = 0.03, phase p = 0.01). Similarly, NVC was altered during septic shock, as indicated by a lower MSC in the frequency band 0.03–0.06 Hz (p < 0.001). dCA and NVC impairments were associated with cortical dysfunction (reduction in the alpha-delta ratio (p = 0.03)).

Conclusions

A progressive loss of dCA and NVC occurs during septic shock and is associated with cortical dysfunction. These findings indicate that the alteration of mechanisms controlling cortical perfusion plays a late role in the pathophysiology of SAE and suggest that alterations of CBF regulation mechanisms in less severe phases of sepsis reported in clinical studies might be due to patients’ comorbidities or other confounders. Furthermore, a mean arterial pressure targeting therapy aiming to optimize dCA might not be sufficient to prevent neuronal dysfunction in sepsis since it would not improve NVC.

Utility of Doppler ultrasound in early-onset neonatal sepsis

Background:

Neonatal sepsis is an important cause of morbidity and mortality among newborns. As there is paucity of literature regarding early alteration of the cerebral blood flow (CBF) in neonatal sepsis our study aims to evaluate the changes in the CBF velocities and Doppler indices in neonates with early-onset neonatal sepsis (EONS) and to evaluate the predictive accuracy of cerebral blood flow velocities (CBFV) by using ultrasound Doppler as a diagnostic marker of EONS.

Methods:

This cross-sectional analytical study was conducted over a period of 2 years with 123 neonates enrolled in the study. The neonates were divided into two groups: Group I (with 54 neonates) - neonates with EONS and group II (with 69 neonates) - age-matched neonates without any signs of sepsis. Ultrasound Doppler examination was performed and the cerebral hemodynamics assessed in neonates during the first seventy two hours of life. Doppler indices and CBFV were measured in the internal carotid artery (ICA), middle cerebral artery (MCA), and vertebral artery (VA) of either side. Data were analyzed using the statistical program SPSS version 23.0 (SPSS Inc., Chicago, IL, USA). Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and diagnostic accuracy were calculated at different selected cutoff values for CBFV parameters.

Results:

Lower resistance and higher peak systolic velocity and end diastolic velocity have been documented in neonates with EONS.

Conclusion:

Our study shows that the cerebral hemodynamics in neonates with EONS is altered which can be assessed bedside by noninvasive ultrasound Doppler examination.

Association Between Sepsis and Microvascular Brain Injury

OBJECTIVES

Many survivors of sepsis suffer long-term cognitive impairment, but the mechanisms of this association remain unknown. The objective of this study was to determine whether sepsis is associated with cerebral microinfarcts on brain autopsy.

DESIGN

Retrospective cohort study.

SETTING AND SUBJECTS

Five-hundred twenty-nine participants of the Adult Changes in Thought, a population-based prospective cohort study of older adults carried out in Kaiser Permanente Washington greater than or equal to 65 years old without dementia at study entry and who underwent brain autopsy.

MEASUREMENTS AND MAIN RESULTS

Late-life sepsis hospitalization was identified using administrative data. We identified 89 individuals with greater than or equal to 1 sepsis hospitalization during study participation, 80 of whom survived hospitalization and died a median of 169 days after discharge. Thirty percent of participants with one or more sepsis hospitalization had greater than two microinfarcts, compared with 19% participants without (χ p = 0.02); 20% of those with sepsis hospitalization had greater than two microinfarcts in the cerebral cortex, compared with 10% of those without (χ p = 0.01). The adjusted relative risk of greater than two microinfarcts was 1.61 (95% CI, 1.01-2.57; p = 0.04); the relative risk for having greater than two microinfarcts in the cerebral cortex was 2.12 (95% CI, 1.12-4.02; p = 0.02). There was no difference in Braak stage for neurofibrillary tangles or consortium to establish a registry for Alzheimer's disease score for neuritic plaques between, but Lewy bodies were less significantly common in those with sepsis.

CONCLUSIONS

Sepsis was specifically associated with moderate to severe vascular brain injury as assessed by microvascular infarcts. This association was stronger for microinfarcts within the cerebral cortex, with those who experienced severe sepsis hospitalization being more than twice as likely to have evidence of moderate to severe cerebral cortical injury in adjusted analyses. Further study to identify mechanisms for the association of sepsis and microinfarcts is needed.

Vasopressor Therapy and the Brain: Dark Side of the Moon

Sepsis, a leading cause of morbidity and mortality, is caused by a deregulated host response to pathogens, and subsequent life-threatening organ dysfunctions. All major systems, including the cardiovascular, respiratory, renal, hepatic, hematological, and the neurological system may be affected by sepsis. Sepsis associated neurological dysfunction is triggered by multiple factors including neuro-inflammation, excitotoxicity, and ischemia. Ischemia results from reduced cerebral blood flow, caused by extreme variations of blood pressure, occlusion of cerebral vessels, or more subtle defects of the microcirculation. International guidelines comprehensively describe the initial hemodynamic management of sepsis, revolving around the normalization of systemic hemodynamics and of arterial lactate. By contrast, the management of sepsis patients suffering from brain dysfunction is poorly detailed, the only salient point being mentioned is that sedation and analgesia should be optimized. However, sepsis and the hemodynamic consequences thereof as well as vasopressors may have severe untoward neurological consequences. The current review describes the general neurological complications, as well as the consequences of vasopressor therapy on the brain and its circulation and addresses methods for cerebral monitoring during sepsis.

Effects of sepsis on hippocampal volume and memory function

BACKGROUND

This study aimed to determine the effects of sepsis on brain integrity, memory, and executive function.

METHODS

Twenty sepsis patients who were not diagnosed with sepsis-associated encephalopathy (SAE) but had abnormal electroencephalograms (EEGs) were included. The control group included twenty healthy persons. A neuropsychological test of memory and executive function and a brain magnetic resonance imaging scan were performed. The volumes of cortex and subcortex were measured using the FreeSurfer software. Acute Physiology and Chronic Health Evaluation II (APACHE II) score was used to determine the disease severity.

RESULTS

In the sepsis group, the levels of immediate free recall, immediate cued recall, and delayed cued recall in the California Verbal Learning Test-II (CVLT-II) were significantly lower; the explicit memory (recollection process) in the process dissociation procedure test was lower; and the volumes of the left and right hippocampi were significantly lower compared with the control group. The volume of the presubiculum in the hippocampus of sepsis patients showed statistically significant decrease. In the sepsis group, the volumes of the left and right hippocampi were negatively correlated with the APACHE II score and positively with immediate free recall, immediate cued recall, and delayed cued recall in the CVLT-II; moreover, the hippocampal volume was significantly correlated with recollection but not with familiarity.

CONCLUSIONS

Patients with abnormal EEGs during hospitalization but with no SAE still have reduced hippocampal volume and memory deficits. This finding indicates that sepsis leads to damage to specific parts of the hippocampus.

Transcranial Doppler Can Predict Development and Outcome of Sepsis-Associated Encephalopathy in Pediatrics With Severe Sepsis or Septic Shock

Background and Aim: Sepsis is a common cause of pediatric intensive care unit (ICU) admission. Sepsis-associated encephalopathy (SAE) may occur owing to brain dysfunction in those patients and may be related to impaired cerebral microcirculation. Transcranial Doppler (TCD) can be used to detect this impairment. In this study, we aimed to assess the role of TCD in prediction of SAE and mortality in patients with severe sepsis or septic shock admitted to PICU. Patients and Methods: This prospective study included 75 children admitted to PICU owing to severe sepsis or septic shock. Upon admission, all patients were subjected to careful history taking, thorough clinical examination, and standard laboratory workup. Severity of clinical illness was assessed using the Pediatric Risk of Mortality (PRISM) III score. TCD was performed on the first day of admission after the normalization of systolic blood pressure with or without vasopressors. The primary study outcome was differences in the measurement of TCD in SAE, and the secondary outcome was discharge from ICU or mortality. Results: The study comprised 45 children with SAE and 30 age- and sex-matched children without SAE. In this study, SAE patients had significantly higher pulsatility index [PI; median interquartile range (IQR): 1.15 (0.98-1.48) vs. 1.0 (0.95-1.06), p = 0.002] and resistive index [RI; median (IQR): 0.68 (0.61-0.77) vs. 0.62 (0.59-0.64), p = 0.001] than had non-SAE patients. PI and RI showed good performance as predictors of subsequent SAE development [area under the curve (AUC): 0.72 and 0.73, respectively]. Non-survivors in SAE patients had significantly higher PRISM III. Receiver operating characteristic (ROC) curve analysis showed good performance of PI and RI as predictors of mortality at the end of follow-up. Conclusions: In children with SAE, cerebrovascular resistance is high and is associated with increased mortality.

The Role of ALDH2 in Sepsis and the To-Be-Discovered Mechanisms

Sepsis, defined as life-threatening tissue damage and organ dysfunction caused by a dysregulated host response to infection, is a critical disease which imposes global health burden. Sepsis-induced organ dysfunction, including circulatory and cardiac dysfunction, hepatic dysfunction, renal dysfunction, etc., contributes to high mortality and long-term disability of sepsis patients. Altered inflammatory response, ROS and reactive aldehyde stress, mitochondrial dysfunction, and programmed cell death pathways (necrosis, apoptosis, and autophagy) have been demonstrated to play crucial roles in septic organ dysfunction. Unfortunately, except for infection control and supportive therapies, no specific therapy exists for sepsis. New specific therapeutic targets are highly warranted. Emerging studies suggested a role of potential therapeutic target of ALDH2, a tetrameric enzyme located in mitochondria to detoxify aldehydes, in septic organ dysfunction. In this article, we will review the presentations and pathophysiology of septic organ dysfunction, as well as summarize and discuss the recent insights regarding ALDH2 in sepsis.

Histopathological changes of organ dysfunction in sepsis

BACKGROUND

Sepsis is a highly lethal disorder. Organ dysfunction in sepsis is not defined as a clinicopathological entity but rather by changes in clinical, physiological, or biochemical parameters. Pathogenesis and specific treatment of organ dysfunction in sepsis are unknown. The study of the histopathological correlate of organ dysfunction in sepsis will help understand its pathogenesis.

METHODS

We searched in PubMed, EMBASE, and Scielo for original articles on kidney, brain, and liver dysfunction in human sepsis. A defined search strategy was designed, and pertinent articles that addressed the histopathological changes in sepsis were retrieved for review. Only studies considered relevant in the field were discussed.

RESULTS

Studies on acute kidney injury (AKI) in sepsis reveal that acute tubular necrosis is less prevalent than other changes, indicating that kidney hypoperfusion is not the predominant pathogenetic mechanism of sepsis-induced AKI. Other more predominant histopathological changes are apoptosis, interstitial inflammation, and, to a lesser extent, thrombosis. Brain pathological findings include white matter hemorrhage and hypercoagulability, microabscess formation, central pontine myelinolysis, multifocal necrotizing leukoencephalopathy, metabolic changes, ischemic changes, and apoptosis. Liver pathology in sepsis includes steatosis, cholangiolitis and intrahepatic cholestasis, periportal inflammation, and apoptosis. There is no information on physiological or biochemical biomarkers of the histopathological findings.

CONCLUSIONS

Histopathological studies may provide important information for a better understanding of the pathogenesis of organ dysfunction in sepsis and for the design of potentially effective therapies. There is a lack of clinically available biomarkers for the identification of organ dysfunction as defined by the histological analysis.

Increased risk of non-multiple sclerosis demyelinating syndromes in patients with preexisting septicaemia: a nationwide retrospective cohort study

Background

Growing evidence shows links between septicaemia and non-multiple sclerosis demyelinating syndromes (NMSDS); nevertheless, epidemiological data are still very limited. This study aimed to explore the relationship between septicaemia and NMSDS in a general population.

Methods

The study included 482 781 individuals diagnosed with septicaemia and 1 892 825 age/sex-matched non-septicaemia patients for the comparison. Data were drawn from a population-based nationwide National Health Insurance Research Database Taiwan, from 1 January 2002 to 31 December 2011. The two cohorts of patients with and without septicaemia were followed up for the occurrence of NMSDS. The Cox-proportional hazard regression model was performed to estimate adjusted HR after multivariate adjustment.

Results

Individuals with septicaemia had a 4.17-fold (95% CI 3.21 to 5.4, p < 0.001) higher risk to develop NMSDS compared with those without septicaemia. Patients aged <65 years had a greater NMSDS risk (<45 years: HR = 6.41, 95% CI 3.65 to 11.3, p < 0.001; 45–64 years: HR = 6.66, 95% CI 3.98 to 11.2, p < 0.001). Furthermore, females with septicaemia and individuals with higher severity of septicaemia were associated with increased risks of developing NMSDS.

Conclusions

Our results indicated that patients with septicaemia were likely to develop NMSDS. A possible contributing role of septicaemia in increasing the hazard of NMSDS is proposed, based on the outcome that individuals with higher severity of septicaemia carried elevated threat of encountering NMSDS.

Effects of mean arterial pressure on arousal in sedated ventilated patients with septic shock: a SEPSISPAM post hoc exploratory study

BACKGROUND

It is unknown whether the recommended mean arterial pressure (MAP) target of 65 mmHg during initial resuscitation of septic shock is sufficient to maintain cerebral perfusion. Thus, we tested the hypothesis that a higher MAP target in patients with septic shock may improve level of arousal.

METHODS

We performed a post hoc exploratory analysis of the SEPSISPAM trial, which assessed the effect of a "high-target" level of MAP (80-85 mmHg) versus the recommended "low-target" MAP (65-70 mm Hg) on mortality in patients with septic shock. Among the 776 patients originally recruited in SEPSISPAM trial, we selected those who were mechanically ventilated and sedated and with available evaluation of arousal level assessed by the Richmond Agitation and Sedation Scale (RASS).

RESULTS

We restricted our analysis to the period in which patients were treated with vasoactive drugs. Cumulative sedative drugs were assessed daily. A total of 532 patients were included in this study: 253 (47.6%) in the low-target group and 279 (52.4%) in the high-target group. Daily cumulative sedative drugs were similar in both groups. Compared to the low-target group, minimal and maximal RASS were significantly higher in the high-target group at day 2, 4 and 5. Furthermore, in order to consider the fact that multiple measures were done for each patient and to consider the global effect of time on these measures, we used a mixed linear regression and multivariate models: we confirmed that maximal RASS values were significantly higher in the high-target group.

CONCLUSION

In patients with septic shock who were mechanically ventilated and sedated, resuscitation with MAP target between 80 and 85 mmHg was associated with higher arousal level as compared to a MAP target between 65 and 70 mmHg.

Dexmedetomidine protects against high mobility group box 1-induced cellular injury by inhibiting pyroptosis

Dexmedetomidine (DEX) is a widely used clinical anesthetic with proven anti-inflammatory effects. Both high mobility group box 1 (HMGB1) and pyroptosis play an important role in the inflammatory response to infection and trauma. Thus far, there have been no studies published addressing the effect of DEX on HMGB1 and pyroptosis. In order to fill this gap in the literature, bone marrow-derived macrophages (BMDMs) were exposed to HMGB1 (4 µg/mL) with or without DEX (50 μM) pretreatment. The production of pro-inflammatory cytokines [such as tumor necrosis factor α (TNF-α), interleukin 1β (IL-1β), and IL-18], phosphorylation of extracellular signal-regulated protein kinases 1 and 2 (ERK1/2) and P38, and the activation of caspase-1 were measured by enzyme immunosorbent assay, western blot analysis, confocal microscope, and flow cytometry, respectively. We found that DEX protected against HMGB1-induced cell death of BMDMs. In addition, DEX suppressed the generation of TNF-α, IL-1β, and IL-18 as well as the phosphorylation of ERK1/2 and P38. Moreover, DEX inhibited caspase-1 activation and decreased pyroptosis. Taken together, these findings demonstrate the protective effect of DEX in mediating HMGB1-induced cellular injury, thus indicating that DEX may be a potential therapeutic candidate for the management of infection and trauma-derived inflammation.

Changes of rScO2 and ScvO2 in children with sepsis-related encephalopathy with different prognoses and clinical features

Clinical features of sepsis-associated encephalopathy in children with different prognoses were analyzed and the changes of regional cerebral oxygen saturation (rScO₂) and central venous oxygen saturation (ScvO₂) were measured. Eighty children with sepsis-related encephalopathy, admitted to the Pediatric Intensive Care Unit (PICU) of the Children's Hospital Affiliated to Zhengzhou University, were enrolled in this study and post-intensive care syndrome (PICS) scoring was performed within 24 h after admission. Patients were separated into groups according to the score results and treatment outcomes. Clinical features, functional tests, imaging examinations, PICS scores, and modified Glasgow Coma Scale (GCS) scores were compared among children with varying severities and prognoses. The changes of rScO₂ and ScvO₂ at different time-points among children with different prognoses were measured and compared. According to PICS scores, there were 8 non-critically ill children, 42 critically ill children, and 30 extremely critically ill children. Fifty-two children survived, and the survival rate was 65%. Comparison of the clinical characteristics of children with different conditions showed that deep coma, generalized seizure, severe electroencephalogram (EEG) abnormalities, and the survival of children were significantly associated with the severity of disease (P<0.05). At the same time, compared to the survivors group, the rates of generalized seizures and severe EEG abnormalities were significantly increased in the deceased children group, while the PICS and GCS scores were significantly decreased (P<0.05). rScO₂ values in the deceased group were lower than those in the survival group at different time-points, but the differences were not significant (P>0.05). On the contrary, ScvO₂ values were significantly higher in the deceased group than those in the survivors group (P<0.05). The lower the PICS and GCS scores in children with sepsis-related encephalopathy, the more serious the condition, and the more likely to develop disturbance of consciousness, epileptic seizures, and abnormal EEG changes. Whereas, changes of ScvO₂ are closely related to prognosis.

Impact of chronic hypertension on time to goal mean arterial pressure and clinical outcomes in critically ill patients with septic shock requiring vasopressors

PURPOSE

Mean arterial pressure (MAP) reflects the adequacy of tissue perfusion. In septic shock, vasopressors are recommended to target MAP ≥65 mmHg. The impact of chronic hypertension (HTN) on MAP achievement and outcomes are uncertain.

MATERIALS AND METHODS

This retrospective, cohort study compared time to goal MAP in critically ill patients with septic shock admitted between May 2014 and July 2016. Between-group differences of patients with and without HTN were compared using appropriate statistical tests. To adjust for imbalances in baseline characteristics, inverse probability of treatment weighting (IPTW) procedure was performed.

RESULTS

Of the 133 included patients, 75 (56.4%) had a history of HTN. Baseline characteristics were mostly similar. Patients with HTN had higher in-hospital (49.3 vs. 31.0%, p = .035) and 28-day mortality (53.3 vs. 31.0%, p = .011). After weighting and adjustment for imbalanced variables, patients with HTN achieved goal MAP more rapidly than those without (HR: 1.84, 95% CI: 1.14-2.96; p = .012). However, they also have higher odds of dying within 28 days of discharge (OR: 3.04, 95% CI: 1.11-8.38; p = .031).

CONCLUSIONS

Patients with HTN achieved goal MAP more rapidly but had higher odds of mortality.

Oxygen-Flow-Pressure Targets for Resuscitation in Critical Hemodynamic Therapy

Far from traditional "vital signs," the field of hemodynamic monitoring (HM) is rapidly developing. However, it is also easy to misunderstand hemodynamic therapy as merely HM and some concrete bundles or guidelines for circulation support. Here, we describe the concept of "critical hemodynamic therapy" and clarify the concepts of the "therapeutic target" and "therapeutic endpoint" in clinical practice. Three main targets (oxygen delivery, blood flow, perfusion pressure) for resuscitation are reviewed in critically ill patients according to the sepsis guidelines and hemodynamic consensus. ScvO2 at least 70% has not been recommended as a directed target for initial resuscitation, and the directed target of mean arterial pressure (MAP) still is 65 mmHg. Moreover, the individual MAP target is underlined, and using flow-dependent monitoring to guide fluid infusion is recommended. The flow-directed target for fluid infusion might be a priority, but it remains controversial in resuscitation. The interpretation of these targets is necessary for adequate resuscitation and the correction of tissue hypoxia. The incoherence phenomenon of resuscitation (macrocirculation and microcirculation, tissue perfusion, and cellular oxygen utilization) is gaining increased attention, and early identification of these incoherences might be helpful to reduce the risk of over-resuscitation.

Impact of fluid challenge increase in cardiac output on the relationship between systemic and cerebral hemodynamics in severe sepsis compared to brain injury and controls

Background

Cognitive dysfunction and delirium after ICU are frequent and may partially result from brain ischemia episodes. We hypothesized that systemic inflammation (severe sepsis or septic shock) modifies the control of brain circulation and the relation between systemic and cerebral hemodynamic after a positive response to fluid challenge (FC).

Methods

Three groups of patients were studied if they increased stroke volume (SV) > 10% after 250 or 500 ml of crystalloids: control group: patients free of comorbidity anesthetized for orthopedic surgery; sepsis group: patients with severe sepsis or septic shock (classic definition); brain injury (BI) group: trauma brain jury or hemorrhagic stroke with no detectable systemic inflammation. The measurements before and after FC were mean arterial blood pressure (MAP) (radial catheter); SV and cardiac output (CO; transesophageal Doppler); bilateral middle cerebral artery (MCAv) velocity with peak systolic (PSV) and end diastolic (EDV) values (transcranial Doppler); end-tidal CO₂. The role of MAP increase was investigated by an arbitrarily threshold increase of 5%, called responder in CO and MAP (RR). The remaining patients were call responders in CO and non-responders in MAP (RnR). Nonparametric tests were used for statistical analysis.

Results

Among the 86 screened patients, 66 have completed the protocol: 17 in control group; 38 in sepsis group; and 11 in BI group. All patients increased SV > 10% after FC. Only the sepsis group increased MAP [+ 12 (2–25%), p < 0.05] with a significant increase in PSV and EDV [(17 (3–30)% and 17 (12–42)%, respectively (p < 0.05)], which did not change in the two other groups. The septic RR or RnR had similar variations in MCAv after FC. The baseline MAP < or > baseline median MAP had similar MCAv.

Conclusions

After a FC-induced increase in SV, MCAv (PSV and EDV) increased only in septic group, mostly independently from MAP increase and from baseline MAP level. Cerebral perfusion becomes passively dependent on systemic blood flow, suggesting a modification of the control of cerebrovascular tone in sepsis-induced systemic inflammation. This information has been considered in the clinical management of septic patients.

Electronic supplementary material

The online version of this article (10.1186/s13613-018-0419-1) contains supplementary material, which is available to authorized users.

Effect of ringers acetate in different doses on plasma volume in rat models of hypovolemia

Background

Even though crystalloids are the first choice for fluid resuscitation in hemodynamically unstable patients, their potency as plasma volume expanders in hypovolemia of different etiologies is largely unknown. The objective of the study was to investigate dose–response curves of a crystalloid in hypovolemia induced by either sepsis or hemorrhagic shock.

Results

Rats were randomized to resuscitation with Ringers acetate at a dose 10, 30, 50, 75, or 100 ml/kg at 4 h after induction of sepsis by cecal ligation and puncture (CLP) or 2.5 h after a 30 ml/kg hemorrhage. Plasma volume (¹²⁵I–albumin) was the primary outcome. Plasma volume decreased by about 11.8 (IQR 9.9–14.5) ml/kg relative baseline after CLP and increased dose-dependently by at most 5.8 (IQR 3.3–7.0) ml/kg in the 100 ml/kg group at 15 min after resuscitation. In the hemorrhage group, the plasma volume increased by at most 13.8 (IQR 7.1–15.0) ml/kg in 100 ml/kg group. Blood volumes at baseline, calculated using hematocrit and plasma volumes, were 72.4 (IQR 68.2–79.5) ml/kg in sepsis group and 71.1 (IQR 69.1–74.7) ml/kg in hemorrhage group. At 15 min after resuscitation with a dose of 100 ml/kg blood volumes increased to 54.8 (IQR 52.5–57.7) ml/kg and ; 49.6 (IQR 45.3–56.4) ml/kg, in the sepsis and hemorrhage groups, respectively. Plasma volume expansion as the percentage of dose at 15 min was 5.9 (IQR 2.5–8.8)% and 14.5 (IQR 12.1–20.0)% in the sepsis and hemorrhage groups, respectively. At 60 min, average plasma volume as the percentage of dose had decreased to 2.9 (IQR ([−2.9] − 8.3)% (P = 0.006) in the sepsis group whereas no change was detected in the hemorrhage group. A dose-dependent decrease in the plasma oncotic pressure, which was more marked in sepsis, was detected at 60 min after resuscitation.

Conclusions

We conclude that the efficacy of Ringers acetate as a plasma volume expander is context dependent and that plasma volume expansion is lower than previously realized across a wide range of doses. Ringers acetate decreases plasma oncotic pressure in sepsis, in part, by mechanisms other than dilution.

Assessment of cerebral circulation in a porcine model of intravenously given E. coli induced fulminant sepsis

BACKGROUND

The aim of the present work was to assess cerebral hemodynamic changes in a porcine model of E.coli induced fulminant sepsis.

METHODS

Nineteen healthy female Hungahib pigs, 10-12 weeks old, randomly assigned into two groups: Control (n = 9) or Septic Group (n = 10). In the Sepsis group Escherichia coli culture suspended in physiological saline was intravenously administrated in a continuously increasing manner according to the following protocol: 2 ml of bacterial culture suspended in physiological saline was injected in the first 30 min, then 4 ml of bacterial culture was administered within 30 min, followed by infusion of 32 ml bacterial culture for 2 h. Control animals received identical amount of saline infusion. Systemic hemodynamic parameters were assessed by PiCCo monitoring, and cerebral hemodynamics by transcranial Doppler sonography (transorbital approach) in both groups.

RESULTS

In control animals, systemic hemodynamic variables and cerebral blood flow velocities and pulsatility indices were relatively stable during the entire procedure. In septic animals shock developed in 165 (IQR: 60-255) minutes after starting the injection of E.coli solution. Blood pressure values gradully decreased, whereas pulse rate increased. A decrease in cardiac index, an increased systemic vascular resistance, and an increased stroke volume variation were observed. Mean cerebral blood flow velocity in the middle cerebral artery did not change during the procedure, but pulsatility index significantly increased.

CONCLUSIONS

There is vasoconstriction at the level of the cerebral arterioles in the early phase of experimental sepsis that overwhelmes autoregulatory response. These results may serve as additional pathophysiological information on the cerebral hemodynamic changes occurring during the septic process and may contribute to a better understanding of the pathomechanism of septic encephalopathy.

Diagnostic and Predictive Levels of Calcium-binding Protein A8 and Tumor Necrosis Factor Receptor-associated Factor 6 in Sepsis-associated Encephalopathy: A Prospective Observational Study

Background:

Despite its high prevalence, morbidity, and mortality, sepsis-associated encephalopathy (SAE) is still poorly understood. The aim of this prospective and observational study was to investigate the clinical significance of calcium-binding protein A8 (S100A8) in serum and tumor necrosis factor receptor-associated factor 6 (TRAF6) in peripheral blood mononuclear cells (PBMCs) in diagnosing SAE and predicting its prognosis.

Methods:

Data of septic patients were collected within 24 h after Intensive Care Unit admission from July 2014 to March 2015. Healthy medical personnel served as the control group. SAE was defined as cerebral dysfunction in the presence of sepsis that fulfilled the exclusion criteria. The biochemical indicators, Glasgow Coma Scale, Acute Physiology and Chronic Health Evaluation score II, TRAF6 in PBMC, serum S100A8, S100β, and neuron-specific enolase were evaluated in SAE patients afresh. TRAF6 and S100A8 were also measured in the control group.

Results:

Of the 57 enrolled patients, 29 were diagnosed with SAE. The S100A8 and TRAF6 concentrations in SAE patients were both significantly higher than that in no-encephalopathy (NE) patients, and higher in NE than that in controls (3.74 ± 3.13 vs. 1.08 ± 0.75 vs. 0.37 ± 0.14 ng/ml, P < 0.01; 3.18 ± 1.55 vs. 1.02 ± 0.63 vs. 0.47 ± 0.10, P < 0.01). S100A8 levels of 1.93 ng/ml were diagnostic of SAE with 92.90% specificity and 69.00% sensitivity in the receiver operating characteristic (ROC) curve, and the area under the curve was 0.86 (95% confidence interval [CI]: 0.76–0.95). TRAF6-relative levels of 1.44 were diagnostic of SAE with 85.70% specificity and 86.20% sensitivity, and the area under the curve was 0.94 (95% CI: 0.88–0.99). In addition, S100A8 levels of 2.41 ng/ml predicted 28-day mortality of SAE with 90.00% specificity and 73.70% sensitivity in the ROC curve, and the area under the curve was 0.88. TRAF6 relative levels of 2.94 predicted 28-day mortality of SAE with 80.00% specificity and 68.40% sensitivity, and the area under the curve was 0.77. Compared with TRAF6, the specificity of serum S100A8 in diagnosing SAE and predicting mortality was higher, although the sensitivity was low. In contrast, the TRAF6 had higher sensitivity for diagnosis.

Conclusions:

Peripheral blood levels of S100A8 and TRAF6 in SAE patients were elevated and might be related to the severity of SAE and predict the outcome of SAE. The efficacy and specificity of S100A8 for SAE diagnosis were superior, despite its weak sensitivity. S100A8 might be a better biomarker for diagnosis of SAE and predicting prognosis.

Neurologic complications of sepsis

Over the past decades, the incidence of sepsis and resultant neurologic sequelae has increased, both in industrialized and low- or middle-income countries, by approximately 5% per year. Up to 300 patients per 100 000 population per year are reported to suffer from sepsis, severe sepsis, and septic shock. Mortality is up to 30%, depending on the precision of diagnostic criteria. The increasing incidence of sepsis is partially explained by demographic changes in society, with aging, increasing numbers of immunocompromised patients, dissemination of multiresistant pathogens, and greater availability of supportive medical care in both industrialized and middle-income countries. This results in more septic patients being admitted to intensive care units. Septic encephalopathy is a manifestation especially of severe sepsis and septic shock where the neurologist plays a crucial role in diagnosis and management. It is well known that timely treatment of sepsis improves outcome and that septic encephalopathy may precede other signs and symptoms. Particularly in the elderly and immunocompromised patient, the brain may be the first organ to show signs of failure. The neurologist diagnosing early septic encephalopathy may therefore contribute to the optimal management of septic patients. The brain is not only an organ failing in sepsis (a "sepsis victim" - as with other organs), but it also overwhelmingly influences all inflammatory processes on a variety of pathophysiologic levels, thus contributing to the initiation and propagation of septic processes. Therefore, the best possible pathophysiologic understanding of septic encephalopathy is essential for its management, and the earliest possible therapy is crucial to prevent the evolution of septic encephalopathy, brain failure, and poor prognosis.

Cerebral Blood Flow Autoregulation in Sepsis for the Intensivist: Why Its Monitoring May Be the Future of Individualized Care

Cerebral blood flow (CBF) autoregulation maintains consistent blood flow across a range of blood pressures (BPs). Sepsis is a common cause of systemic hypotension and cerebral dysfunction. Guidelines for BP management in sepsis are based on historical concepts of CBF autoregulation that have now evolved with the availability of more precise technology for its measurement. In this article, we provide a narrative review of methods of monitoring CBF autoregulation, the cerebral effects of sepsis, and the current knowledge of CBF autoregulation in sepsis. Current guidelines for BP management in sepsis are based on a goal of maintaining mean arterial pressure (MAP) above the lower limit of CBF autoregulation. Bedside tools are now available to monitor CBF autoregulation continuously. These data reveal that individual BP goals determined from CBF autoregulation monitoring are more variable than previously expected. In patients undergoing cardiac surgery with cardiopulmonary bypass, for example, the lower limit of autoregulation varied between a MAP of 40 to 90 mm Hg. Studies of CBF autoregulation in sepsis suggest patients frequently manifest impaired CBF autoregulation, possibly a result of BP below the lower limit of autoregulation, particularly in early sepsis or with sepsis-associated encephalopathy. This suggests that the present consensus guidelines for BP management in sepsis may expose some patients to both cerebral hypoperfusion and cerebral hyperperfusion, potentially resulting in damage to brain parenchyma. The future use of novel techniques to study and clinically monitor CBF autoregulation could provide insight into the cerebral pathophysiology of sepsis and offer more precise treatments that may improve functional and cognitive outcomes for survivors of sepsis.

Cerebral hemodynamics in sepsis assessed by transcranial Doppler: a systematic review and meta-analysis

Cerebral microcirculation is gradually compromised during sepsis, with significant reductions in the function of capillaries and blood perfusion in small vessels. Transcranial Doppler ultrasound (TCD) has been used to assess cerebral circulation in a typical clinical setting. This study was to systematically review TCD studies, assess their methodological quality, and identify trends that can be associated with the temporal evolution of sepsis and its clinical outcome. A meta-analysis of systematic reviews was conducted according to the PRISMA statement. Articles were searched from 1982 until the conclusion of this review in December 2015. Twelve prospective and observational studies were selected. Evaluations of cerebral blood flow, cerebral autoregulation, and carbon dioxide (CO₂) vasoreactivity were summarized. A temporal pattern of the evolution of the illness was found. In early sepsis, the median blood flow velocity (Vm) and pulsatility index (PI) increased, and the cerebral autoregulation (CA) remained unchanged. In contrast, Vm normalization, PI reduction and CA impairment were found in later sepsis (patients with severe sepsis or septic shock). Cerebral haemodynamic is impaired in sepsis. Modifications in cerebral blood flow may be consequence to the endothelial dysfunction of the microvasculature induced by the release of inflammatory mediators. A better understanding of cerebral hemodynamics may improve the clinical management of patients with sepsis and, consequently, improve clinical outcomes.

Regulation of the cerebral circulation: bedside assessment and clinical implications

Regulation of the cerebral circulation relies on the complex interplay between cardiovascular, respiratory, and neural physiology. In health, these physiologic systems act to maintain an adequate cerebral blood flow (CBF) through modulation of hydrodynamic parameters; the resistance of cerebral vessels, and the arterial, intracranial, and venous pressures. In critical illness, however, one or more of these parameters can be compromised, raising the possibility of disturbed CBF regulation and its pathophysiologic sequelae. Rigorous assessment of the cerebral circulation requires not only measuring CBF and its hydrodynamic determinants but also assessing the stability of CBF in response to changes in arterial pressure (cerebral autoregulation), the reactivity of CBF to a vasodilator (carbon dioxide reactivity, for example), and the dynamic regulation of arterial pressure (baroreceptor sensitivity). Ideally, cerebral circulation monitors in critical care should be continuous, physically robust, allow for both regional and global CBF assessment, and be conducive to application at the bedside. Regulation of the cerebral circulation is impaired not only in primary neurologic conditions that affect the vasculature such as subarachnoid haemorrhage and stroke, but also in conditions that affect the regulation of intracranial pressure (such as traumatic brain injury and hydrocephalus) or arterial blood pressure (sepsis or cardiac dysfunction). Importantly, this impairment is often associated with poor patient outcome. At present, assessment of the cerebral circulation is primarily used as a research tool to elucidate pathophysiology or prognosis. However, when combined with other physiologic signals and online analytical techniques, cerebral circulation monitoring has the appealing potential to not only prognosticate patients, but also direct critical care management.

Effects of short-term mechanical hyperventilation on cerebral blood flow and dynamic cerebral autoregulation in critically ill patients with sepsis

In sepsis, higher PaCO2 levels are associated with impaired dynamic cerebral autoregulation (dCA), which may expose the brain to hypo- and hyperperfusion during acute fluctuations in blood pressure. We hypothesised that short-term mechanical hyperventilation would dCA in critically ill patients with sepsis. Seven mechanically ventilated septic patients were included. We assessed dCA before and after 30 min of mechanical hyperventilation. Transfer function analysis of spontaneous oscillations in transcranial Doppler-based middle cerebral artery blood flow velocity (MCAv) and invasive mean arterial blood pressure was used to assess dCA. Mechanical enhance hyperventilation reduced the median PaCO2 from 5.3 (IQR, 5.0-6.5) to 4.7 (IQR, 4.2-5.1) kPa (p < 0.05). This was associated with a reduction in the median MCAv from 57 (IQR, 33-68) to 32 (IQR, 21-40) cm sec(-1) (p < 0.05). Apart from a small increase in gain in the low frequency range (2.32 [IQR 1.80-2.41] vs. 2.59 (2.40-4.64) cm mmHg(-1) sec(-1); p < 0.05), this was not associated with any enhancement in dCA. In conclusion, cerebral CO2 vasoreactivity was found to be preserved in septic patients; nevertheless, and in contrast to our working hypothesis, short-term mechanical hyperventilation did not enhance dCA.

Optimizing mean arterial pressure in septic shock: a critical reappraisal of the literature

Guidelines recommend that a mean arterial pressure (MAP) value greater than 65 mm Hg should be the initial blood pressure target in septic shock, but what evidence is there to support this statement? We searched Pubmed and Google Scholar by using the key words 'arterial pressure', 'septic shock', and 'norepinephrine' and retrieved human studies published between 1 January 2000 and 31 July 2014. We identified seven comparative studies: two randomized clinical trials and five observational studies. The results of the literature review suggest that a MAP target of 65 mm Hg is usually sufficient in patients with septic shock. However, a MAP of around 75 to 85 mm Hg may reduce the development of acute kidney injury in patients with chronic arterial hypertension. Because of the high prevalence of chronic arterial hypertension in patients who develop septic shock, this finding is of considerable importance. Future studies should assess interactions between time, fluid volumes administered, and doses of vasopressors.

Clinical neurophysiological assessment of sepsis-associated brain dysfunction: a systematic review

Introduction

Several studies have reported the presence of electroencephalography (EEG) abnormalities or altered evoked potentials (EPs) during sepsis. However, the role of these tests in the diagnosis and prognostic assessment of sepsis-associated encephalopathy remains unclear.

Methods

We performed a systematic search for studies evaluating EEG and/or EPs in adult (≥18 years) patients with sepsis-associated encephalopathy. The following outcomes were extracted: a) incidence of EEG/EP abnormalities; b) diagnosis of sepsis-associated delirium or encephalopathy with EEG/EP; c) outcome.

Results

Among 1976 citations, 17 articles met the inclusion criteria. The incidence of EEG abnormalities during sepsis ranged from 12% to 100% for background abnormality and 6% to 12% for presence of triphasic waves. Two studies found that epileptiform discharges and electrographic seizures were more common in critically ill patients with than without sepsis. In one study, EEG background abnormalities were related to the presence and the severity of encephalopathy. Background slowing or suppression and the presence of triphasic waves were also associated with higher mortality. A few studies demonstrated that quantitative EEG analysis and EP could show significant differences in patients with sepsis compared to controls but their association with encephalopathy and outcome was not evaluated.

Conclusions

Abnormalities in EEG and EPs are present in the majority of septic patients. There is some evidence to support EEG use in the detection and prognostication of sepsis-associated encephalopathy, but further clinical investigation is needed to confirm this suggestion.

Plasma Volume Expansion with 5% Albumin Compared to Ringer’s Acetate during Normal and Increased Microvascular Permeability in the Rat

Background:

It is believed that the effectiveness of colloids as plasma volume expanders is dependent on the endothelial permeability for macromolecules. The objective of this study was to test the hypothesis that the plasma volume expanding effect of 5% albumin relative to that of a crystalloid solution is reduced if microvascular permeability is increased.

Methods:

A control group was resuscitated with either 5% albumin (8 ml/kg) or Ringer’s acetate (36 ml/kg) immediately after a hemorrhage of 8 ml/kg (n = 29). In a second group, permeability was increased by inducing sepsis through cecal ligation and incision (n = 28). Three hours after cecal ligation and incision, the animals were resuscitated with either 5% albumin in a ratio of 1:1 relative to the volume of lost plasma, or Ringer’s acetate in a ratio of 4.5:1.

Results:

In the hemorrhage group, plasma volumes at 15 min after resuscitation with albumin or Ringer’s acetate had increased by 9.8 ± 2.6 ml/kg (mean ± SD) and 7.4 ± 2.9 ml/kg and were similar at 2 and 4 h. Plasma volume 3 h after cecal ligation and incision had decreased by approximately 7 ml/kg, and at 15 min after resuscitation with albumin or Ringer’s acetate it had increased by 5.7 ± 2.9 and 2.4 ± 3.0 ml/kg, respectively (P &lt; 0.05). At 2 and 4 h after resuscitation, plasma volumes did not differ between the groups.

Conclusion:

This study does not support the hypothesis that the plasma-volume-expanding effect of albumin relative to that of crystalloids is decreased under conditions characterized by increased permeability.

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

Introduction

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

Methods

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

Results

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

Conclusion

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

Sepsis Associated Encephalopathy

Sepsis associated encephalopathy (SAE) is a common but poorly understood neurological complication of sepsis. It is characterized by diffuse brain dysfunction secondary to infection elsewhere in the body without overt CNS infection. The pathophysiology of SAE is complex and multifactorial including a number of intertwined mechanisms such as vascular damage, endothelial activation, breakdown of the blood brain barrier, altered brain signaling, brain inflammation, and apoptosis. Clinical presentation of SAE may range from mild symptoms such as malaise and concentration deficits to deep coma. The evaluation of cognitive dysfunction is made difficult by the absence of any specific investigations or biomarkers and the common use of sedation in critically ill patients. SAE thus remains diagnosis of exclusion which can only be made after ruling out other causes of altered mentation in a febrile, critically ill patient by appropriate investigations. In spite of high mortality rate, management of SAE is limited to treatment of the underlying infection and symptomatic treatment for delirium and seizures. It is important to be aware of this condition because SAE may present in early stages of sepsis, even before the diagnostic criteria for sepsis can be met. This review discusses the diagnostic approach to patients with SAE along with its epidemiology, pathophysiology, clinical presentation, and differential diagnosis.

Functional imaging of cerebral perfusion

The functional imaging of perfusion enables the study of its properties such as the vasoreactivity to circulating gases, the autoregulation and the neurovascular coupling. Downstream from arterial stenosis, this imaging can estimate the vascular reserve and the risk of ischemia in order to adapt the therapeutic strategy. This method reveals the hemodynamic disorders in patients suffering from Alzheimer's disease or with arteriovenous malformations revealed by epilepsy. Functional MRI of the vasoreactivity also helps to better interpret the functional MRI activation in practice and in clinical research.

Early neurovascular uncoupling in the brain during community acquired pneumonia

INTRODUCTION

Sepsis leads to microcirculatory dysfunction and therefore a disturbed neurovascular coupling in the brain. To investigate if the dysfunction is also present in less severe inflammatory diseases we studied the neurovascular coupling in patients suffering from community acquired pneumonia.

METHODS

Patients were investigated in the acute phase of pneumonia and after recovery. The neurovascular coupling was investigated with a simultaneous electroencephalogram (EEG)-Doppler technique applying a visual stimulation paradigm. Resting EEG frequencies, visual evoked potentials as well as resting and stimulated hemodynamic responses were obtained. Disease severity was characterized by laboratory and cognitive parameters as well as related scoring systems. Data were compared to a control group.

RESULTS

Whereas visually evoked potentials (VEP) remained stable a significant slowing and therefore uncoupling of the hemodynamic responses were found in the acute phase of pneumonia (Rate time: control group: 3.6 ± 2.5 vs. acute pneumonia: 1.6 ± 2.4 s; P < 0.0005). In the initial investigation, patients who deteriorated showed a decreased hemodynamic response as compared with those who recovered (gain: recovered: 15% ± 4% vs. deteriorated: 9% ± 3%, P < 0.05; control: 14% ± 5%). After recovery the coupling normalized.

CONCLUSIONS

Our study underlines the role of an early microcirculatory dysfunction in inflammatory syndromes that become evident in pre-septic conditions with a gradual decline according to disease severity.

Impaired cerebrovascular autoregulation in patients with severe sepsis and sepsis-associated delirium

Introduction

Sepsis-associated delirium (SAD) increases morbidity in septic patients and, therefore, factors contributing to SAD should be further characterized. One possible mechanism might be the impairment of cerebrovascular autoregulation (AR) by sepsis, leading to cerebral hypo- or hyperperfusion in these haemodynamically unstable patients. Therefore, the present study investigates the relationship between the incidence of SAD and the status of AR during sepsis.

Methods

Cerebral blood flow velocity was measured using transcranial Doppler sonography and was correlated with the invasive arterial blood pressure curve to calculate the index of AR Mx (Mx>0.3 indicates impaired AR). Mx was measured daily during the first 4 days of sepsis. Diagnosis of a SAD was performed using the confusion assessment method for ICU (CAM-ICU) and, furthermore the predominant brain electrical activity in electroencephalogram (EEG) both at day 4 after reduction of sedation to RASS >-2.

Results

30 critically ill adult patients with severe sepsis or septic shock (APACHE II 32 ± 6) were included. AR was impaired at day 1 in 60%, day 2 in 59%, day 3 in 41% and day 4 in 46% of patients; SAD detected by CAM-ICU was present in 76 % of patients. Impaired AR at day 1 was associated with the incidence of SAD at day 4 (p = 0.035).

Conclusions

AR is impaired in the great majority of patients with severe sepsis during the first two days. Impaired AR is associated with SAD, suggesting that dysfunction of AR is one of the trigger mechanisms contributing to the development of SAD.

Trial registration

clinicalTrials.gov ID NCT01029080

Sepsis-associated encephalopathy

Sepsis-associated encephalopathy (SAE) is a diffuse brain dysfunction that occurs secondary to infection in the body without overt CNS infection. SAE is frequently encountered in critically ill patients in intensive care units, and in up to 70% of patients with severe systemic infection. The severity of SAE can range from mild delirium to deep coma. Seizures and myoclonus are infrequent and cranial nerves are almost always spared, but most severe cases have an associated critical illness neuromyopathy. Development of SAE probably involves a number of mechanisms that are not mutually exclusive and vary from patient to patient. Substantial neurological and psychological morbidities often occur in survivors. Mortality is almost always due to multiorgan failure rather than neurological complications, and is almost 70% in patients with severe SAE. Further research into the pathophysiology, management and prevention of SAE is needed. This Review discusses the epidemiology and clinical presentation of SAE. Recent evidence for SAE pathophysiology is outlined and a diagnostic approach to patients with this syndrome is presented. Lastly, prognosis and management of SAE is discussed.

Endotoxemia reduces cerebral perfusion but enhances dynamic cerebrovascular autoregulation at reduced arterial carbon dioxide tension

OBJECTIVE

The administration of endotoxin to healthy humans reduces cerebral blood flow but its influence on dynamic cerebral autoregulation remains unknown. We considered that a reduction in arterial carbon dioxide tension would attenuate cerebral perfusion and improve dynamic cerebral autoregulation in healthy subjects exposed to endotoxemia.

DESIGN

Prospective descriptive study.

SETTING

Hospital research laboratory.

SUBJECTS

Ten healthy young subjects (age: 32 ± 8 yrs [mean ± SD]; weight: 84 ± 10 kg; weight: 184 ± 5 cm; body mass index: 25 ± 2 kg/m2) participated in the study.

INTERVENTIONS

Systemic hemodynamics, middle cerebral artery mean flow velocity, and dynamic cerebral autoregulation evaluated by transfer function analysis in the very low (<0.07 Hz), low (0.07-0.15 Hz), and high (>0.15 Hz) frequency ranges were monitored in these volunteers before and after an endotoxin bolus (2 ng/kg; Escherichia coli).

MEASUREMENTS AND MAIN RESULTS

Endotoxin increased body temperature of the subjects from 36.8 ± 0.4°C to 38.6 ± 0.5°C (p < .001) and plasma tumor necrosis factor-α from 5.6 (2.8-6.7) pg/mL to 392 (128-2258) pg/mL (p < .02). Endotoxemia had no influence on mean arterial pressure (95 [74-103] mm Hg vs. 92 [78-104] mm Hg; p = .75), but increased cardiac output (8.3 [6.1-9.5] L·min(-1) vs. 6.0 [4.5-8.2] L·min(-1); p = .02) through an elevation in heart rate (82 ± 9 beats·min(-1) vs. 63 ± 10 beats·min(-1); p < .001), whereas arterial carbon dioxide tension (37 ± 5 mm Hg vs. 41 ± 2 mm Hg; p < .05) and middle cerebral artery mean flow velocity (37 ± 9 cm·sec(-1) vs. 47 ± 10 cm·sec(-1); p < .01) were reduced. In regard to dynamic cerebral autoregulation, endotoxemia was associated with lower middle cerebral artery mean flow velocity variability (1.0 ± 1.0 [cm·sec(-1)] Hz vs. 2.8 ± 1.5 [cm·sec(-1)] Hz; p < .001), reduced gain (0.52 ± 0.11 cm·sec(-1) x mm Hg(-1) vs. 0.74 ± 0.17 cm·sec(-1) x mm Hg(-1); p < .05), normalized gain (0.22 ± 0.05 vs. 0.40 ± 0.17%·%; p < .05), and higher mean arterial pressure-to-middle cerebral artery mean flow velocity phase difference (p < .05) in the low frequency range (0.07-0.15 Hz).

CONCLUSIONS

These data support that the reduction in arterial carbon dioxide tension explains the improved dynamic cerebral autoregulation and the reduced cerebral perfusion encountered in healthy subjects during endotoxemia.

[Septic encephalopathy]

Septic encephalopathy describes a diffuse cerebral dysfunction in association with sepsis. It is the most common cause of altered brain function in the intensive care unit setting but other causes have to be excluded. Alterations in the level of consciousness occur early and are common. Epileptic seizures may occur but asymmetric neurological findings are not typical. The pathophysiology of septic encephalopathy is diverse and not fully elucidated; however, perfusion abnormalities play an important role. Neuropathological findings are diffuse, widespread and often show features of ischemia and non-bacterial inflammation. Diagnostic procedures should exclude frequent differential diagnoses, such as stroke, meningitis or encephalitis. Cerebral computed tomography (CT) is usually unremarkable but magnetic resonance imaging (MRI) may reveal vasogenic edema in terms of a posterior reversible encephalopathy syndrome. Septic encephalopathy requires an adequate therapy of the sepsis syndrome but a specific therapy is not yet available.

Cerebral blood flow velocity in early-onset neonatal sepsis and its clinical significance

Chorioamnionitis is a known risk factor for neurological damage in newborns. The present study aimed at assessing the changes in cerebral blood flow velocity (CBFV) in early-onset neonatal sepsis (EONS) and determining its predictive value as well as prognostic significance. Inborn neonates with antenatal risk factors for chorioamnionitis were followed up for development of EONS, diagnosed by presence of clinical signs along with positive blood culture and/or elevated interleukin-6 (IL-6) concentrations (≥50 pg/mL) in umbilical cord blood. Comparison group was formed by asymptomatic neonates who had risk factors for chorioamnionitis but did not develop EONS and cord blood IL-6 concentrations were <50 pg/mL. CBFV (resistance and pulsatility indices, peak systolic flow velocity, and vascular diameter) of internal carotid, vertebral, and middle cerebral arteries was assessed by transcranial Doppler ultrasonography within 24 h of birth. The babies were kept under clinical and radiological follow-up for a minimum period of 6 months. Data were analyzed by SPSS 16.0. Final study group contained 55 neonates with sepsis and 35 asymptomatic control neonates. Blood culture was positive in 27 babies of the sepsis group with a preponderance of Gram-negative bacterial isolation. Significantly lower resistance, vasodilatation, and higher blood flow were noted in all the cerebral arteries of the sepsis group. Increase in CBFV was correlated with elevated IL-6 concentrations. CBFV parameters showed significant predictive accuracy as early diagnostic markers of EONS. Among the sepsis group, 14 patients showed signs of intracranial hemorrhage during the hospital stay of which four expired and six showed signs of ventricular dilatation during follow-up. These patients had significantly higher CBFV compared to those who survived. Assessment of CBFV at early hours of birth can be adopted as an additional bedside, non-invasive investigation with immediate diagnostic and late prognostic significance.