A profile of metabolic acidosis in patients with sepsis in an Intensive Care Unit setting

Integrated Electrochemical Aptamer Biosensing and Colorimetric pH Monitoring via Hydrogel Microneedle Assays for Assessing Antibiotic Treatment

Current methods for therapeutic drug monitoring (TDM) have a long turnaround time as they involve collecting patients' blood samples followed by transferring the samples to medical laboratories where sample processing and analysis are performed. To enable real-time and minimally invasive TDM, a microneedle (MN) biosensor to monitor the levels of two important antibiotics, vancomycin (VAN) and gentamicin (GEN) is developed. The MN biosensor is composed of a hydrogel MN (HMN), and an aptamer-functionalized flexible (Flex) electrode, named HMN-Flex. The HMN extracts dermal interstitial fluid (ISF) and transfers it to the Flex electrode where sensing of the target antibiotics happens. The HMN-Flex performance is validated ex vivo using skin models as well as in vivo in live rat animal models. Data is leveraged from the HMN-Flex system to construct pharmacokinetic profiles for VAN and GEN and compare these profiles with conventional blood-based measurements. Additionally, to track pH and monitor patient's response during antibiotic treatment, an HMN is developed that employs a colorimetric method to detect changes in the pH, named HMN-pH assay, whose performance has been validated both in vitro and in vivo. Further, multiplexed antibiotic and pH detection is achieved by simultaneously employing the HMN-pH and HMN-Flex on live animals.

Acidity induces durable enhancement of Treg cell suppressive functions for tumor immune evasion

The microenvironment within solid tumors often becomes acidic due to various factors associated with abnormal metabolism and cellular activities, including increased lactate production as a result of dysregulated tumor glycolysis. Recently, we have identified multiple tumor microenvironment (TME) factors that potentiate regulatory T (Treg) cell function in evading anti-tumor immunosurveillance. Despite the strong correlation between lactate and acidity, the potential roles of acidity in intratumoral Treg cell adaptation and underlying molecular mechanisms have gone largely unstudied. In this study, we demonstrate that acidity significantly enhances immunosuppressive functions of nTreg cells, but not iTreg cells, without altering the expression of either FoxP3 or the cell surface receptors CD25, CTLA4, or GITR in these cells. Surprisingly, the addition of lactate, often considered a major contributor to increased acidity of the TME, completely abolished the acidity-induced enhancement of nTreg suppressive functions. Consistently, metabolic flux analyses showed elevated basal mitochondrial respiratory capacity and ATP-coupled respiration in acidity-treated nTreg cells without altering glycolytic capacity. Genome-wide transcriptome and metabolomics analyses revealed alterations in multiple metabolic pathways, particularly the one-carbon folate metabolism pathway, with reduced SAM, folate, and glutathione, in nTreg cells exposed to low pH conditions. Addition of a one-carbon metabolic contributor, formate, diminished the acidity-induced enhancement in nTreg cell suppressive functions, but neither SAM nor glutathione could reverse the phenotype. Remarkably, in vitro transient treatment of nTreg cells resulted in sustained enhancement of their functions, as evidenced by more vigorous tumor growth observed in mice adoptively receiving acidity-treated nTreg cells. Further analysis of intratumoral infiltrated T cells confirmed a significant reduction in CD8+ T cell frequency and their granzyme B production. In summary, our study elucidates how acidity-mediated metabolic reprogramming leads to sustained Treg-mediated tumor immune evasion.

Infantile Hypertrophic Pyloric Stenosis Without Metabolic Alkalosis: A Report of Two Cases

Infantile hypertrophic pyloric stenosis (IHPS) is a condition typically characterized by hypertrophy of the pylorus, leading to gastric outlet obstruction and forceful, nonbilious vomiting in young infants. This case series reports two infants with IHPS who exhibited metabolic acidosis, deviating from the classical biochemical presentation of hypochloremic, hypokalemic metabolic alkalosis. The unusual occurrence of metabolic acidosis in these cases suggests the possibility of alternative or additional pathophysiological mechanisms at play. Such deviations from the expected biochemical profile highlight the complexity of IHPS and the need for a broader diagnostic perspective.

Splenic SUMO1 controls systemic inflammation in experimental sepsis

Introduction

The recent discovery of TAK981(Subasumstat), the first-in-class selective inhibitor of SUMOylation, enables new immune treatments. TAK981 is already in clinical trials to potentiate immunotherapy in metastatic tumors and hematologic malignancies. Cancer patients have more than ten times higher risk of infections, but the effects of TAK981 in sepsis are unknown and previous studies on SUMO in infections are conflicting.

Methods

We used TAK981 in two sepsis models; polymicrobial peritonitis (CLP) and LPS endotoxemia. Splenectomy was done in both models to study the role of spleen. Western blotting of SUMO-conjugated proteins in spleen lysates was done. Global SUMO1 and SUMO3 knockout mice were used to study the specific SUMO regulation of inflammation in LPS endotoxemia. Splenocytes adoptive transfer was done from SUMO knockouts to wild type mice to study the role of spleen SUMOylation in experimental sepsis.

Results and discussion

Here, we report that inhibition of SUMOylation with TAK981 improved survival in mild polymicrobial peritonitis by enhancing innate immune responses and peritoneal bacterial clearance. Thus, we focused on the effects of TAK981 on the immune responses to bacterial endotoxin, showing that TAK981 enhanced early TNFα production but did not affect the resolution of inflammation. Splenectomy decreased serum TNFα levels by nearly 60% and TAK981-induced TNFα responses. In the spleen, endotoxemia induced a distinct temporal and substrate specificity for SUMO1 and SUMO2/3, and both were inhibited by TAK981. Global genetic depletion of SUMO1, but not SUMO3, enhanced TNFα production and metabolic acidosis. The transfer of SUMO1-null, but not wild-type, splenocytes into splenectomized wild-type mice exacerbated TNFα production and metabolic acidosis in endotoxemia.

Conclusion

These results suggest that specific regulation of splenic SUMO1 can modulate immune and metabolic responses to bacterial infection.

Clinical effectiveness of sodium bicarbonate therapy on mortality for septic patients with acute moderate lactic acidosis

Objective: This study aimed to explore the effectiveness of sodium bicarbonate (SB) administration on mortality in septic patients with acute moderate lactic acidosis (MLA). Methods: The large ICU database (MIMIC-IV) was retrospectively analyzed. Patients with sepsis and acute MLA were identified. Propensity score analysis (PSA) was performed to explain baseline differences in the probability of accepting or not accepting SB. The edge structured cox model (MSCM) was used to adjust for baseline and time-varying confounding variables. The primary outcome was the ICU and hospital mortality. The subgroup of septic shock was also investigated. Results: A total of 512 septic patients with acute MLA were identified in this study, including 160 in the SB group and 352 in the non-SB group. In the PSA, SB administration was associated with reduced ICU (HR .58, 95% CI 0.38-.89; p <.05) and hospital (HR .67, 95% CI 0.47-.95; p <.05) mortality in septic patients with acute MLA. In the subgroup, the results were similar with septic patients. In the MSCM, SB administration could also improve the ICU (HR .35, 95% CI 0.16-.75; p <.01) and (HR .50, 95% CI 0.28-.88; p <.05) mortality on septic patients. However, In the subgroup, SB administration could only be found associated with improved hospital (HR .44, 95% CI 0.20-.97; p <.05) survival in septic shock. Conclusion: SB administration treatment could reduce ICU and hospital mortality of septic patients with acute MLA. Meanwhile, it could also improve hospital survival in the subgroup of septic shock patients with acute MLA.

Comparison between early and late mortalities due to severe sepsis in a pediatric intensive care unit: five-years-experience

Background

The majority of children who die of sepsis suffer from refractory shock and/or multiple organ dysfunction syndrome, with many deaths occurring within the initial 48–72 h of treatment.

Methods

A retrospective observational study of deceased patients due to severe sepsis over 5 years, from the 1st of August 2015 to the end of July 2020, that were admitted in a pediatric intensive care unit.

Results

Over 5-year duration of the study, the trend of cases with severe sepsis increased from 26.4% in 2015 to 40.7% in 2020. Meanwhile, the trend of mortality among this category of patients dropped from 66.7% in 2015 to 33.9% in 2020. From the studied 163 deceased patients, results showed predominance of Klebsiella pneumoniae of the extended resistance pattern in bronchoalveolar lavage and blood cultures, and it came second to Candida in urine cultures. Pandrug-resistant organism was recorded in 8.59% (n = 14 patients). Patients with bacteremia, acidosis, high pediatric index of mortality (PIM-2), and pediatric logistic organ dysfunction (PELOD) scores were statistically related to early fatality fate.

Conclusion

High mortality was associated with the increasing spread of resistant organisms especially Klebsiella pneumoniae. Patients with bacteremia, acidosis, and high PIM-2 and PELOD scores probably will need immediate, vigorous, and intense care in order to save their lives.

Effectiveness of sodium bicarbonate infusion on mortality for elderly septic patients with acute metabolic acidosis

Objective: This study aimed to explore the effectiveness of sodium bicarbonate (SB) infusion on mortality in elderly septic patients with acute metabolic acidosis (MA) and in other subgroups.

Methods: Retrospective analysis of a large ICU database (MIMIC-IV) was performed. Elderly septic patients with acute MA were identified from MIMIC-IV. Propensity score analysis (PSA) was performed to explain for the baseline differences in the probability to receive SB or not. The marginal structural Cox model (MSCM) was developed to adjust for both baseline and time-varying confounding variables. The primary outcome was the ICU and hospital mortality.

Results: A total of 869 elderly septic patients with acute MA were identified in this study, including 361 in the SB group and 508 in the non-SB group. In the PSA, SB infusion was not associated with reduced ICU (HR 0.82, 95% CI 0.62–1.10; p = 0.19) or hospital (HR 0.94, 95% CI 0.74–1.19; p = 0.60) mortality in overall elderly septic patients with acute MA. In the subgroup of severe metabolic acidosis, SB infusion could not improve the ICU (HR 0.82, 95% CI 0.62–1.10; p =0.19) and hospital (HR 0.94, 95% CI 0.74–1.19; p =0.60) mortality on elderly septic patients. However, In the subgroup of moderate metabolic acidosis, SB infusion could be found associated with improved ICU (HR 0.64, 95% CI 0.43–0.95; p &lt;0.05) and hospital (HR 0.70, 95% CI 0.50–0.99; p &lt;0.05) survival in elderly septic patients. In the MSCM, the results were similar with PSA.

Conclusion: SB infusion could improve both ICU and hospital survival for elderly septic patients with acute metabolic acidosis.

Transcutaneous Flexible Sensor for In Vivo Photonic Detection of pH and Lactate

Clinical research shows that frequent measurements of both pH and lactate can help guide therapy and improve patient outcome. However, current methods of sampling blood pH and lactate make it impractical to take readings frequently (due to the heightened risk of blood infection and anemia). As a solution, we have engineered a subcutaneous pH and lactate sensor (PALS) that can provide continuous, physiologically relevant measurements. To measure pH, a sheet containing a pH-sensitive fluorescent dye is placed over 400 and 465 nm light-emitting diodes (LEDs) and a filter-coated photodetector. The filter-coated photodetector collects an emitted signal from the dye for each LED excitation, and the ratio of the emitted signals is used to monitor pH. To measure lactate, two sensing sheets comprising an oxygen-sensitive phosphorescent dye are each mounted to a 625 nm LED. One sheet additionally comprises the enzyme lactate oxidase. The LEDs are sequentially modulated to excite the sensing sheets, and their phase shift at the LED drive frequency is used to monitor lactate. In vitro results indicate that PALS successfully records pH changes from 6.92 to 7.70, allowing for discrimination between acidosis and alkalosis, and can track lactate levels up to 9 mM. Both sensing strategies exhibit fast rise times (< 5 min) and stable measurements. Multianalyte in vitro models of physiological disorders show that the sensor measurements consistently quantify the expected pathophysiological trends without cross talk; in vivo rabbit testing further indicates usefulness in the clinical setting.

Sepsis as a Pan-Endocrine Illness-Endocrine Disorders in Septic Patients

Sepsis is defined as "life-threatening organ dysfunction caused by a dysregulated host response to infection". One of the elements of dysregulated host response is an endocrine system disorder. Changes in its functioning in the course of sepsis affect almost all hormonal axes. In sepsis, a function disturbance of the hypothalamic-pituitary-adrenal axis has been described, in the range of which the most important seems to be hypercortisolemia in the acute phase. Imbalance in the hypothalamic-pituitary-thyroid axis is also described. The most typical manifestation is a triiodothyronine concentration decrease and reverse triiodothyronine concentration increase. In the somatotropic axis, a change in the secretion pattern of growth hormone and peripheral resistance to this hormone has been described. In the hypothalamic-pituitary-gonadal axis, the reduction in testosterone concentration in men and the stress-induced "hypothalamic amenorrhea" in women have been described. Catecholamine and β-adrenergic stimulation disorders have also been reported. Disorders in the endocrine system are part of the "dysregulated host response to infection". They may also affect other components of this dysregulated response, such as metabolism. Hormonal changes occurring in the course of sepsis require further research, not only in order to explore their potential significance in therapy, but also due to their promising prognostic value.

Biomarkers and Associated Immune Mechanisms for Early Detection and Therapeutic Management of Sepsis

Sepsis is conceptually defined as life-threatening organ dysfunction that is caused by a dysregulated host response to infection. Although there has been significant advancement in recent decades in defining and understanding sepsis pathology, clinical management of sepsis is challenging due to difficulties in diagnosis, a lack of reliable prognostic biomarkers, and treatment options that are largely limited to antibiotic therapy and fundamental supportive measures. The lack of reliable diagnostic and prognostic tests makes it difficult to triage patients who are in need of more urgent care. Furthermore, while the acute inpatient treatment of sepsis warrants ongoing attention and investigation, efforts must also be directed toward longer term survival and outcomes. Sepsis survivors experience incomplete recovery, with long-term health impairments that may require both cognitive and physical treatment and rehabilitation. This review summarizes recent advances in sepsis prognosis research and discusses progress made in elucidating the underlying causes of prolonged health deficits experienced by patients surviving the early phases of sepsis.

Sensing acidosis: nociception or sngception?

Background

Sensing tissue acidosis is an important function of the somatosensory nervous system to response to noxious stimuli.

Main body

In the pain clinic, acid or soreness sensation is a characteristic sensory phenotype of various acute and chronic pain syndromes, such as delayed onset muscle soreness, fibromyalgia, and radicular pain. However, soreness sensation is a sign of successful analgesia for acupuncture and noxipoint therapy. Thus, the nature of acid or soreness sensation is not always nociceptive (or painful) and could be anti-nociceptive. To facilitate the investigation of the molecular and neurobiological mechanisms of soreness sensation, we propose a concept called “sngception (sng- ception)” to describe the response of the somatosensory nervous system to sense tissue acidosis and to distinguish it from nociception. “Sng” is a Taiwanese word that represents the state of soreness while at the same time imitates the natural vocalization of humans feeling sore.

Conclusion

Here we propose sngception as a specific somatosensory function that transmits the acid sensation from the peripheral to the central nervous system. Sngception could partially overlap with nociception, but it could also transmit antinociception, proprioception, and pruriception.

Can base excess and anion gap predict lactate level in diagnosis of septic shock?

Background

Lactate measurement is the key component in septic shock identification and resuscitation. However, point-of-care lactate testing is not widely used due to the lack of access to nearby test equipment. Biomarkers such as serum lactate, anion gap (AG), and base excess (BE) are used in determining shock in patients with seemingly normal vital signs.

Purpose

We aimed to determine if these biomarkers can be used interchangeably in patients with septic shock in the emergency setting.

Patients and methods

A prospective observational cohort study was undertaken at a tertiary hospital in southern Thailand. Baseline point-of-care BE, AG, and serum lactate were recorded in all patients presenting with septic shock at the emergency department. Overall correlations including area under the receiver operating characteristic curve (AUROC) for both BE and AG to predict serum lactate level were calculated.

Results

One hundred and fifteen patients were enrolled. Pearson correlation of serum lactate to BE was −0.59 (r² = 0.35; 95% confidence interval [CI], −0.69 to −0.44; P < 0.001) and BE to AG was −0.67 (r² = 0.49; 95% CI, −0.76 to −0.55; P < 0.001), and serum lactate to AG was 0.64 (r² = 0.41; 95% CI, 0.52 to 0.74; P < 0.001). A cut-off point of 15.8 for AG identified a lactate level ≥2 mmol/L (sensitivity, 71.4%; specificity, 80.7%; and AUROC, 0.76), and the best cut-off value to predict a lactate level ≥4 mmol/L was 18.5 (sensitivity, 64.2%; specificity, 85.5%; and AUROC 0.78).

Conclusion

In patients with septic shock, lactate and AG showed a strong correlation with each other, whereas lactate and BE showed a moderate correlation with each other. Thus, these biomarkers can be used interchangeably to help determine septic shock earlier in patients.