Intensive Care Medicine Experimental最新文献

Molecular hydrogen gas (HG), administered through inhalation or as hydrogen-rich fluids (HRF), has demonstrated antioxidant, anti-inflammatory, antiapoptotic, cytoprotective, and beneficial mitochondrial effects in critical illness. Preclinical studies and human clinical studies consistently endorse hydrogen gas as safe, with mechanisms of action linked to vital molecular pathways, such as reductions in both oxidative stress and inflammation with beneficial effects on mitochondria. In preclinical studies, HG has been shown to improve outcomes in conditions such as sepsis, acute lung injury, hepatic injury, pancreatitis, cardiac arrest, traumatic injury, acute kidney injury, and brain injury. HG has been given to human subjects across multiple disease states and has a good safety profile with encouraging clinical effects. Given its accessibility, safety, and low-cost, hydrogen gas therapy should be assessed in adequately powered clinical trials in critical illness.

Background: The relationship between carbon dioxide pressures (PCO₂) and contents (CCO₂) is linked to the Haldane effect. Nevertheless, under shock conditions, hydrogen ion accumulation might strongly influence the discrepancies between PCO₂ and CCO₂. This study aims to evaluate the impact of hydrogen ion accumulation and hemoglobin oxygen saturation (Haldane effect) on PCO₂:CCO₂ relationships during induction and resuscitation of endotoxemic shock.

Methods: Shock was induced by an escalating dose of lipopolysaccharide in 12 female Landrace pigs. Norepinephrine was then started to maintain mean arterial pressure ≥ 75 mmHg, while successive fluid boluses were administered targeting arterial lactate < 2.0 mmol·L^-1 or decreases > 10% per 30 min. Mesenteric venous and arterial PCO₂ were measured at baseline, time of shock, and then, every hour for 6 h, while their respective CCO₂ were computed using the Douglas equation. Mesenteric venous-to-arterial PCO₂ and CCO₂ differences (i.e., ΔPCO₂ and ΔCCO₂), and then, their absolute arithmetic differences (i.e., [|ΔPCO₂ - ΔCCO₂|]) were calculated. Discrepancies in [|ΔPCO₂ - ΔCCO₂|] between adjacent measurement time points (i.e., ∆-[|ΔPCO₂ - ΔCCO₂|]) were compared with the variations in mesenteric venous O₂ saturation (∆-S_vmesO₂) and arterial-to-mesenteric venous pH (∆-pH_a-vmes). In addition, arterial and venous CCO₂ values were recalculated, maintaining baseline pH (Def_pH) or SO₂ values (Def_SO2) to then quantify the impact of pH and S_vmesO₂ on the PCO₂:CCO₂ relationship.

Results: Variations in ∆-[|∆PCO₂ - ∆CCO₂|]) were paralleled by ∆-pH_a-vmes (R² = 0.56, p < 0.001), while poorly correlated with ∆-S_vmesO₂ (R² = 0.15, p < 0.001). When variations in pH were not included in CCO₂ calculations (i.e., Def_pH-CCO₂), both arterial and mesenteric venous CCO₂ disagreed in ranges from 21.8 to 50.4% and 15.3 to 47.6%, respectively. Conversely, overestimation of CCO₂ was almost null when variations in SvmesO₂ were not assumed (Def_SvmesO2). Calculations under Def_pH-CCO₂ conditions revealed an almost linear relationship between PCO₂ and CCO₂, contrasting with a non-linear relationship when pH variations were acknowledged.

Conclusions: Regional splanchnic PCO₂:CCO₂ relationship was mostly influenced by hydrogen ion accumulation rather than the Haldane effect during development and resusc

Introduction: Endothelial cells play a central role in the pathophysiology of sepsis-associated acute kidney injury (SA-AKI), yet we have limited understanding of the markers of microvascular-specific response. We therefore employed a translational approach integrating spatially resolved transcriptomics in a mouse SA-AKI model with validation in human kidney tissues and plasma, aiming to define the molecular signature of the endothelial response to SA-AKI in mice and in human patients.

Methods: In this post hoc analysis of prospectively collected data, we identified sepsis-associated target mRNAs and validated their expression via RT-qPCR in distinct renal microvascular compartments isolated by laser microdissection (LMD) from both cecal ligation and puncture (CLP) mice and post-mortem kidney biopsies of SA-AKI patients. Additionally, we measured the corresponding circulating proteins in plasma from two patient cohorts with sepsis and SA-AKI: one consisting of patients presenting to the emergency department, and the other of patients with severe sepsis requiring organ support in the ICU.

Results: We identified several differentially expressed genes in the renal microvasculature following sepsis, including Mt1, Mt2, Saa3, Hp, C3, Sparc, Mmp8, and Chil3. Whole-organ samples from CLP mice also showed increased expression in the liver and lung. Except for SPARC, all genes were similarly upregulated in human kidney biopsies from SA-AKI patients. Circulating protein levels were elevated in sepsis and SA-AKI patients compared to controls; however, only CHI3L1 and MMP8 showed significantly higher levels in SA-AKI versus sepsis across both early and advanced stages.

Conclusion: Our findings reveal markers of the microvascular response to sepsis, which include increased levels of HP, C3, Chil3/CHI3L1, and MMP8, both at the transcriptomic level in mouse and human kidney microvasculature and at the protein level in circulating plasma of SA-AKI patients. The upregulation of these markers was shared across multiple organs and may reflect widespread endothelial activation contributing to sepsis pathophysiology.

Delirium is a frequent and serious complication of critical illness, yet its pathophysiological mechanisms remain incompletely understood. Serum biomarkers offer a potential avenue for improved diagnosis, risk stratification, and mechanistic insight. This systematic review synthesises evidence from 28 studies evaluating 54 serum biomarkers in relation to delirium among critically ill adult patients. Biomarkers were categorised by mechanistic pathway, including central nervous system (CNS) injury, immune activation, hormonal dysregulation, neurotransmission, coagulation, and amino acid metabolism. Among CNS injury markers, S100β and neurofilament light chain (NfL) demonstrated the most consistent associations with delirium presence and severity, supporting a role for astrocytic and axonal injury in delirium pathogenesis. Inflammatory markers such as interleukin-6 (IL-6), C-reactive protein (CRP), and tumour necrosis factor-alpha (TNF-α) were frequently studied but showed variable associations, reflecting the complex and non-specific nature of systemic inflammation. Hormonal biomarkers, including cortisol and prolactin, showed preliminary promise, while neurotransmitter-related biomarkers yielded inconsistent results, challenging canonical hypotheses. A major limitation in the literature was the lack of standardisation in delirium assessment, sampling timelines, and adjustment for confounding variables. Only a minority of studies incorporated temporal profiling or longitudinal outcomes, and replication across cohorts was limited. Heterogeneity in ICU populations further reduced generalisability. This review proposes a new conceptual framework of mechanistic endotyping, integrating multimodal biomarker profiling with clinical phenotyping to define biologically distinct subtypes of delirium. Such an approach may support precision medicine strategies by aligning therapeutic interventions with underlying pathophysiology. Future biomarker research should prioritise longitudinal sampling, harmonised protocols, and integration with EEG, imaging, and cognitive outcomes. Despite early promise, serum biomarkers for ICU delirium remain investigational and require further validation before clinical application.

Background: Low systolic blood pressure (SBP) is a key criterion for diagnosing cardiogenic shock (CS) caused by a reduction in stroke volume and cardiac output (CO). The temporal interaction between changes in pressure and flow has not been well described in the development of CS. In a large animal model, we assessed the temporal relationships of SBP, CO, and blood flow in the carotid artery during induction of CS.

Methods: Fifteen adult Danish landrace pigs (median weight 71 kg) underwent CS induction by stepwise injection of polyvinyl alcohol microspheres into the left main coronary artery every 3 min to induce microvascular obstruction. After each injection, CO, SBP, and mixed venous saturation (SvO₂) were recorded simultaneously from a ventricle sheath in the carotid artery and a pulmonary artery catheter in the right internal jugular vein. A Doppler flow probe measured blood flow in the left carotid artery. CS was defined as a ≥ 50% reduction in CO or SvO₂ from baseline, or absolute SvO₂ < 30%.

Results: CS occurred after a mean of 8 (range 5 to 19) boluses of microspheres. SBP declined from 99 (± 15) mmHg to 74 (± 6) mmHg, equal to 74 (± 13)% of the baseline value. CO was reduced to 5.8 (± 0.7) L/min to 2.2 (± 1.3) L/min, equal to 38 (± 23)% and SvO₂ from 63 (± 7)% to 37 (± 7)%, equal to 60 (± 13)% of baseline values. The decrease in CO was due to a reduction to 43 (± 26)% in stroke volume, as heart rate remained unchanged. The carotid artery blood flow was reduced from 285 (± 50) mL/min to 155 (± 56) mL/min, equal to 54% of baseline values. The decline in SvO₂ and CO preceded a reduction in SBP, and after 25% of emboli were given, CO decreased by 24% while SBP was unchanged.

Conclusion: In a porcine model of ischemic myocardial injury, the decrease in blood flow and stroke volume preceded a decline in SBP, suggesting pressure preservation occurs in the presence of hypoperfusion.

Dobutamine is the most commonly used inotropic agent in critically ill patients with impaired cardiac contractility. However, its benefit-risk profile remains debated, and clear, structured guidance for its use is lacking. This hypothesis proposes a pragmatic framework for dobutamine administration to promote rational and consistent clinical and experimental practice. The aim is to propose a rational and reproducible use of inotropic therapy with dobutamine in both clinical and experimental settings in cases of shock with low cardiac output, particularly cardiogenic shock, septic shock with septic cardiomyopathy, and low cardiac output syndrome after cardiac surgery (LCOS). Dobutamine should be prescribed only in the presence of acute circulatory failure with signs of peripheral hypoperfusion and impaired cardiac contractility. A low cardiac index (CI) alone does not mandate inotrope initiation. Echocardiography is essential for initial assessment but should be complemented by continuous cardiac output monitoring for evaluating dose-response. The recommended starting dose is 2.5 μg/kg*min, with stepwise titration based on CI and perfusion markers reassessed every 20 min. A significant CI increase and resolution of hypoperfusion should guide further escalation. Persistent hypoperfusion despite CI improvement may indicate inadequate response and justify cautious dose increases, while continued hypoperfusion with further CI rise suggests a flow-independent deficit, discouraging further titration. Dobutamine should be used with clear indications, guided by a standardized approach integrating continuous hemodynamic and perfusion monitoring. This strategy may help optimize therapeutic benefit while minimizing unnecessary exposure and adverse effects.

Background: Critical illness is known to reduce gut microbiota (GM) diversity, a change associated with adverse outcomes. Among potential mechanisms, splanchnic hypoperfusion may play a key role. Cardiac arrest (CA), characterized by transient global hypoperfusion, provides a relevant model to explore this effect.

Results: We conducted a secondary, propensity score-matched analysis of a cohort study investigating GM changes during early intensive care unit stay. Stool samples were collected at ICU admission (S1) and at least 24 h later (S2). GM profiling was performed using 16S rRNA sequencing. Shannon diversity index and taxonomic composition were compared between CA and non-CA patients. Propensity score matching and generalized linear models (GLM) were used to adjust for confounding. A total of 26 patients were included in this analysis (13 CA, 13 matched controls). At S1, CA patients had significantly lower GM diversity (Shannon index: 3.6 [3.0-3.8] vs. 4.3 [3.9-4.8], p = 0.019). This was confirmed in the GLM (β = - 0.30, SE 0.12, p = 0.022). At S2, diversity remained lower (3.2 [2.7-3.8] vs. 4.0 [3.7-4.3], p = 0.064). While no global compositional shifts were observed between groups, differences in the abundance of specific taxa were noted.

Conclusion: CA is associated with reduced GM diversity in the first few days of intensive care unit admission compared to non-CA patients, supporting a role for splanchnic hypoperfusion in GM modulation. Further research should investigate clinical consequences and evaluate microbiota-targeted interventions in this high-risk population.

Background: Hypernatremia, a common electrolyte disorder in critically ill patients, induces a hyperosmotic state linked to increased mortality and metabolic stress. While loop diuretics such as furosemide are used for fluid management, their main effect is water excretion, often worsening hypernatremia. This study aimed to determine whether free water infusion enhances sodium excretion when combined with furosemide after a sodium chloride bolus. We also hypothesized that hyperosmolar hypernatremia stimulates protein degradation and urea synthesis.

Results: Fourteen pigs (seven per group) received a sodium chloride bolus to induce hypernatremia (plasma Na⁺ > 150 mmol/L). One group received furosemide alone, while the other received furosemide plus free water to maintain normo-osmolality. Renal and metabolic parameters were analyzed over five hours. Free water infusion significantly lowered plasma sodium levels (134 ± 4 vs. 150 ± 4 mmol/L, p = 1.2e-14) and increased total sodium excretion (99 ± 20 vs. 70 ± 18 mmol, p = 0.00056) and urine output (1860 ± 220 vs. 1200 ± 160 mL, p = 2.47e-05). Fractional sodium excretion was higher with free water (5.3 ± 1.1% vs. 3.5 ± 2.2%, p = 0.012). Plasma glutamine was elevated in the no-water group (1305 ± 209 vs. 1084 ± 110 µmol/L, p = 0.029), indicating greater metabolic stress.

Conclusions: These results suggest that free water infusion enhances sodium clearance and reduces hypernatremia-induced metabolic alterations, supporting its potential role in fluid management strategies.

Background and aims: Acute pulmonary thromboembolism (PE) may require haemodynamic supportive therapies while appropriate therapies for clot burden reduction are pursued. This scoping review aims to identify the non-mechanical haemodynamic support interventions that have been investigated for the management of acute PE, and to map the available evidence for each intervention.

Methods: An iterative search of MEDLINE, Embase, CINAHL and the Cochrane Library was performed to map all available animal studies, case-series, observational studies, human trials, systematic reviews and meta-analyses that investigate any non-mechanical haemodynamic support in acute PE.

Results: 6,362 unique articles were screened and of the 132 studies that met the eligibility criteria, 98 were animal studies, 31 human studies, and 3 were systematic reviews. Among all studies 57 different agents were found, including 16 among the human studies. 6 agents were investigated across 7 human randomised controlled trials (RCTs) and included inhaled nitric oxide, fluid, furosemide, diclofenac, sildenafil, and epoprostenol, but were limited to intermediate-risk PE and none demonstrated a mortality benefit from the intervention tested.

Conclusion: The evidence to guide clinical practice in the non-mechanical haemodynamic support of PE is severely limited. However, there are numerous candidate agents that could be further investigated. The high-risk group are an understudied population.

Transcranial ultrasound is gaining widespread recognition as a useful bedside monitoring tool and non-invasive diagnostic device in the critically ill patient. The capabilities of transcranial ultrasound are themselves ever-increasing, and this, combined with improved physiological understanding, affords insights into pathophysiological processes often concealed from the bedside critical care clinician. Transcranial ultrasound remains unique in regard to its non-invasive, rapid, and critically composite blood flow velocity-centric (not pressure-centric) information. The mobility of transcranial ultrasound devices is of particular value to the largely immobile critically ill patient requiring multiple organ supportive therapies. In this review, we discuss some important origins of more modern composite techniques and highlight relevant major key concepts, whilst noting exciting frontier possibilities.