Vasopressors Do Not Influence Cerebral Critical Closing Pressure During Systemic Inflammation Evoked by Experimental Endotoxemia and Sepsis in Humans

Review of the therapeutic effects of traditional Chinese medicine in sepsis-associated encephalopathy

ETHNOPHARMACOLOGICAL RELEVANCE

Sepsis-associated encephalopathy (SAE) is a common and serious complication during the acute phase of and after recovery from sepsis that seriously affects the quality of life of patients. Traditional Chinese medicine (TCM) has been widely used in modern medicine for neurological anomalies and has become a therapeutic tool for the treatment of SAE due to its multitargeting effects and low toxicity and side effects.

AIMS OF THE STUDY

This review provides insights into the pathogenesis and treatments of SAE, focusing on the clinical and experimental impacts of TCM formulations and their single components.

METHODS

Several known databases such as PubMed, Web of Science, Google Scholar, China National Knowledge Infrastructure (CNKI), and others were extensively explored with keywords and phrases such as "sepsis-associated encephalopathy", "traditional Chinese medicine", "herbs", "SAE", "sepsis", "cerebral" or other relevant terms to obtain literature between 2018 and 2024.

RESULTS

Extensive evidence indicated that TCM could decrease mortality and normalize neurological function in patients with sepsis; these effects might be associated with factors such as reduced oxidative stress and downregulated expression of inflammatory factors.

CONCLUSIONS

TCM shows notable efficacy in treating SAE, warranting deeper mechanistic studies to optimize its clinical application.

Sepsis and delayed cerebral ischemia are associated and have a cumulative effect on poor functional outcome in aneurysmal subarachnoid hemorrhage

Objective

Although sepsis and delayed cerebral ischemia (DCI) are severe complications in patients with aneurysmal subarachnoid hemorrhage (aSAH) and share pathophysiological features, their interrelation and additive effect on functional outcome is uncertain. We investigated the association between sepsis and DCI and their cumulative effect on functional outcome in patients with aSAH using current sepsis-3 definition.

Methods

Patients admitted to our hospital between 11/2014 and 11/2018 for aSAH were retrospectively analyzed. The main explanatory variable was sepsis, diagnosed using sepsis-3 criteria. Endpoints were DCI and functional outcome at hospital discharge (modified Rankin Scale (mRS) 0-3 vs. 4-6). Propensity score matching (PSM) and multivariable logistic regressions were performed.

Results

Of 238 patients with aSAH, 55 (23.1%) developed sepsis and 74 (31.1%) DCI. After PSM, aSAH patients with sepsis displayed significantly worse functional outcome (p < 0.01) and longer ICU stay (p = 0.046). Sepsis was independently associated with DCI (OR = 2.46, 95%CI: 1.28-4.72, p < 0.01). However, after exclusion of patients who developed sepsis before (OR = 1.59, 95%CI: 0.78-3.24, p = 0.21) or after DCI (OR = 0.85, 95%CI: 0.37-1.95, p = 0.70) this statistical association did not remain. Good functional outcome gradually decreased from 56.3% (76/135) in patients with neither sepsis nor DCI, to 43.8% (21/48) in those with no sepsis but DCI, to 34.5% (10/29) with sepsis but no DCI and to 7.7% (2/26) in patients with both sepsis and DCI.

Conclusion

Our study demonstrates a strong association between sepsis, DCI and functional outcome in patients with aSAH and suggests a complex interplay resulting in a cumulative effect towards poor functional outcome, which warrants further studies.

Static autoregulation in humans

The process by which cerebral blood flow (CBF) remains approximately constant in response to short-term variations in arterial blood pressure (ABP) is known as cerebral autoregulation. This classic view, that it remains constant over a wide range of ABP, has however been challenged by a growing number of studies. To provide an updated understanding of the static cerebral pressure-flow relationship and to characterise the autoregulation curve more rigorously, we conducted a comprehensive literature research. Results were based on 143 studies in healthy individuals aged 18 to 65 years. The mean sensitivities of CBF to changes in ABP were found to be 1.47 ± 0.71%/% for decreased ABP and 0.37 ± 0.38%/% for increased ABP. The significant difference in CBF directional sensitivity suggests that cerebral autoregulation appears to be more effective in buffering increases in ABP than decreases in ABP. Regression analysis of absolute CBF and ABP identified an autoregulatory plateau of approximately 20 mmHg (ABP between 80 and 100 mmHg), which is much smaller than the widely accepted classical view. Age and sex were found to have no effect on autoregulation strength. This data-driven approach provides a quantitative method of analysing static autoregulation that can be easily updated as more experimental data become available.

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.

Impacts of a Pressure Challenge on Cerebral Critical Closing Pressure and Effective Cerebral Perfusion Pressure in Patients with Traumatic Brain Injury

INTRODUCTION

Cerebral critical closing pressure (CrCP) comprises intracranial pressure (ICP) and arteriolar wall tension (WT). It is the arterial blood pressure (ABP) at which small vessels close and circulation stops. We hypothesized that the increase in WT secondary to a systemic hypertensive challenge would lead to an increase in CrCP and that the "effective" cerebral perfusion pressure (CPPeff; calculated as ABP - CrCP) would give more complete information than the "conventional" cerebral perfusion pressure (CPP; calculated as ABP - ICP).

OBJECTIVE

This study aimed to compare CrCP, CPP, and CPPeff changes during a hypertensive challenge in patients with a severe traumatic brain injury.

PATIENTS AND METHODS

Data on ABP, ICP, and cerebral blood flow velocity, measured by transcranial Doppler ultrasound, were acquired simultaneously for 30 min both basally and during a hypertensive challenge. An impedance-based CrCP model was used.

RESULTS

The following values are expressed as median (interquartile range). There were 11 patients, aged 29 (14) years. CPP increased from 73 (17) to 102 (26) mmHg (P ≤ 0.001). ICP did not change. CrCP changed from 23 (11) to 27 (10) mmHg (P ≤ 0.001). WT increased from 7 (5) to 11 (7) mmHg (P ˂ 0.005). CPPeff changed less than CPP.

CONCLUSION

The CPP change was greater than the CPPeff change, mainly because CrCP increased simultaneously with the WT increase as a result of the autoregulatory response. CPPeff provides information about the real driving force generating blood movement.

Phenylephrine impairs host defence mechanisms to infection: a combined laboratory study in mice and translational human study

BACKGROUND

Immunosuppression after surgery is associated with postoperative complications, mediated in part by catecholamines that exert anti-inflammatory effects via the β-adrenergic receptor. Phenylephrine, generally regarded as a selective α-adrenergic agonist, is frequently used to treat perioperative hypotension. However, phenylephrine may impair host defence through β-adrenergic affinity.

METHODS

Human leukocytes were stimulated with lipopolysaccharide (LPS) in the presence or absence of phenylephrine and α- and β-adrenergic antagonists. C57BL/6J male mice received continuous infusion of phenylephrine (30-50 μg kg-1 min-1 i.v.) or saline via micro-osmotic pumps, before LPS administration (5 mg kg-1 i.v.) or caecal ligation and puncture (CLP). Twenty healthy males were randomised to a 5 h infusion of phenylephrine (0.5 μg kg-1 min-1) or saline before receiving LPS (2 ng kg-1 i.v.).

RESULTS

In vitro, phenylephrine enhanced LPS-induced production of the anti-inflammatory cytokine interleukin (IL)-10 (maximum augmentation of 93%) while attenuating the release of pro-inflammatory mediators. These effects were reversed by pre-incubation with β-antagonists, but not α-antagonists. Plasma IL-10 levels were higher in LPS-challenged mice infused with phenylephrine, whereas pro-inflammatory mediators were reduced. Phenylephrine infusion increased bacterial counts after CLP in peritoneal fluid (+42%, P=0.0069), spleen (+59%, P=0.04), and liver (+35%, P=0.09). In healthy volunteers, phenylephrine enhanced the LPS-induced IL-10 response (+76%, P=0.0008) while attenuating plasma concentrations of pro-inflammatory mediators including IL-8 (-15%, P=0.03).

CONCLUSIONS

Phenylephrine exerts potent anti-inflammatory effects, possibly involving the β-adrenoreceptor. Phenylephrine promotes bacterial outgrowth after surgical peritonitis. Phenylephrine may therefore compromise host defence in surgical patients and increase susceptibility towards infection.

CLINICAL TRIAL REGISTRATION

NCT02675868 (Clinicaltrials.gov).

The cerebrovascular response to norepinephrine: A scoping systematic review of the animal and human literature

Intravenous norepinephrine (NE) is utilized commonly in critical care for cardiovascular support. NE's impact on cerebrovasculature is unclear and may carry important implications during states of critical neurological illness. The aim of the study was to perform a scoping review of the literature on the cerebrovascular/cerebral blood flow (CBF) effects of NE. A search of MEDLINE, BIOSIS, EMBASE, Global Health, SCOPUS, and Cochrane Library from inception to December 2019 was performed. All manuscripts pertaining to the administration of NE, in which the impact on CBF/cerebral vasculature was recorded, were included. We identified 62 animal studies and 26 human studies. Overall, there was a trend to a direct vasoconstriction effect of NE on the cerebral vasculature, with conflicting studies having demonstrated both increases and decreases in regional CBF (rCBF) or global CBF. Healthy animals and those undergoing cardiopulmonary resuscitation demonstrated a dose-dependent increase in CBF with NE administration. However, animal models and human patients with acquired brain injury had varied responses in CBF to NE administration. The animal models indicate an increase in cerebral vasoconstriction with NE administration through the alpha receptors in vessels. Global and rCBF during the injection of NE displays a wide variation depending on treatment and model/patient.

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.