Extracorporeal circulation impairs microcirculation perfusion and organ function

Acute Dapagliflozin Administration Ameliorates Cardiac Surgery-Associated Acute Kidney Injury in a Rabbit Model

BACKGROUND

 Several studies have shown that sodium-glucose cotransporter-2 inhibitors have a renoprotective effect on acute kidney injury (AKI), but their effect on cardiac surgery-associated AKI is unknown.

METHODS AND RESULTS

 AKI was induced in 25 rabbits without diabetes mellitus by cardiopulmonary bypass (CPB) for 2 h and they were divided into 5 groups: sham; dapagliflozin-treated sham; CPB; dapagliflozin-treated CPB; and furosemide-treated CPB (n=5 in each group). Dapagliflozin was administered via the femoral vein before initiating CPB. Kidney tissue and urine and blood samples were collected after the surgical procedure. There were no differences in the hemodynamic variables of each group. Dapagliflozin reduced serum creatinine and blood urea nitrogen concentrations, and increased overall urine output (all P<0.05). Hematoxylin and eosin staining showed that the tubular injury score was improved after dapagliflozin administration (P<0.01). Dapagliflozin administration mitigated reactive oxygen species and kidney injury molecule-1 as assessed by immunohistochemistry (both P<0.0001). Protein expression analysis showed improvement of inflammatory cytokines and apoptosis, and antioxidant enzyme expression was elevated (all P<0.05) through activation of the nuclear factor erythroid 2-related factor 2 pathway (P<0.01) by dapagliflozin.

CONCLUSIONS

 Acute intravenous administration of dapagliflozin protects against CPB-induced AKI. Dapagliflozin may have direct renoprotective effects in renal tubular cells.

From bench to bedside: A review of the application and potential of microcirculatory assessment by hand-held videomicroscopy

In clinical practice, there is vast knowledge regarding the evaluation of macrocirculatory parameters, such as systemic blood pressure and cardiac output, for the hemodynamic monitoring of patients. However, assessment of the microcirculation has not yet been incorporated into the bedside armamentarium. Hand-held intravital video microscopy enables the direct, noninvasive, evaluation of the sublingual microcirculation at the bedside, offering insights into the status of the systemic microcirculation. It is easily performed and may be employed in several clinical settings, providing immediate results that may help guide patient management. Therefore, the incorporation of hand-held intravital video microscopy into clinical practice may lead to tremendous improvements in the quality of care of critical, unstable patients or offer new data in the evaluation of patients with chronic diseases, especially those with microcirculatory involvement, such as occurs in diabetes.

Transcatheter Versus Surgical Aortic Valve Replacement in Recipients of Solid Organ Transplants and Liver Cirrhosis: A Propensity-Matched Analysis of National Readmission Data

Transcatheter aortic valve replacement (TAVR) continues to grow in the United States. There are limited data on recipients of solid organ transplant (SOT) and patients with liver cirrhosis who undergo aortic valve replacement (AVR). Our study aims to evaluate outcomes in these populations. Using the national readmission database (2016 to 2020), we identified recipients of SOT and patients with liver cirrhosis without previous liver transplants who were admitted for severe aortic stenosis and underwent either TAVR or surgical AVR (SAVR). We used multivariable regression for adjusted analysis and the propensity score matching model, implementing complete Mahalanobis distance matching within the Propensity Score Caliper (0.2) to match TAVR and SAVR cohorts for outcomes. Of 3,394 hospitalizations for AVR in recipients of SOT, 2,181 underwent TAVR, and 1,213 underwent SAVR. On propensity-matched analysis, SAVR was associated with more adverse events than was TAVR, including in-hospital mortality (5.2% vs 1.1%, adjusted odds ratio [aOR] 4.49, p <0.001), acute kidney injury (43.7% vs 10.2%, p <0.001), cardiogenic shock (9.0% vs 1.6%, p <0.001), sudden cardiac arrest (15.9 vs 6.0%, p <0.001), major adverse cardiac and cerebrovascular events (28% vs 10.4%, p <0.001), and net adverse events (72.8 vs 37.6%, p <0.001). A greater median length of stay (10 vs 2 days, p <0.001) and adjusted cost ($80,842 vs $57,014, p <0.001) were also observed. The readmission rates were the same for both cohorts after a 6-month follow-up. Similarly, in 14,763 hospitalizations for AVR in liver cirrhosis, 7,109 patients underwent TAVR, and 7,654 underwent SAVR. In propensity-matched cohorts (n = 2,341), SAVR was found to be associated with greater adverse events, including in-hospital mortality (19.8% vs 10%), stroke (6.7% vs 2%), acute kidney injury (67.7% vs 30.3%), cardiogenic shock (41.9% vs 19.9%), sudden cardiac arrest (31.8% vs 13.2%, aOR 2.89), major adverse cardiac and cerebrovascular events (66.2% vs 35.7%), and net adverse events (86% vs 59.5%) (p <0.001). A greater median length of stay (16 vs 3 days) and cost ($500,218 vs $263,383) were also observed (p <0.001). However, the rate of readmissions at 30-day (9% vs 11.1%) and 180-day intervals (33.4% vs 39.8%) was lower for the SAVR cohort (p <0.05). In recipients of SOT and patients with liver cirrhosis, SAVR is associated with greater short-term mortality, adverse events, and healthcare burden than is TAVR. TAVR is a relatively safer alternative to SAVR in these patient populations, although further studies are warranted to compare the long-term outcomes.

High-molecular-weight linear polymers improve microvascular perfusion after extracorporeal circulation

High-molecular-weight linear polymers (HMWLPs) have earned the name "drag-reducing polymers" because of their ability to reduce drag in turbulent flows. Recently, these polymers have become popular in bioengineering applications. This study investigated whether the addition of HMWLP in a venoarterial extracorporeal circulation (ECC) model could improve microvascular perfusion and oxygenation. Golden Syrian hamsters were instrumented with a dorsal skinfold window chamber and subjected to ECC using a circuit comprised of a peristaltic pump and a bubble trap. The circuit was primed with lactated Ringer solution (LR) containing either 5 ppm of polyethylene glycol (PEG) with a low molecular weight of 500 kDa (PEG500k) or 5 ppm of PEG with a high molecular weight of 3,500 kDa (PEG3500k). After 90 min of ECC at 15% of the animal's cardiac output, the results showed that the addition of PEG3500k to LR improved microvascular blood flow in arterioles and venules acutely (2 h after ECC), whereas functional capillary density showed improvement up to 24 h after ECC. Similarly, PEG3500k improved venular hemoglobin O2 saturation on the following day after ECC. The serum and various excised organs all displayed reduced inflammation with the addition of PEG3500k, and several of these organs also had a reduction in markers of damage with the HMWLPs compared to LR alone. These promising results suggest that the addition of small amounts of PEG3500k can help mitigate the loss of microcirculatory function and reduce the inflammatory response from ECC procedures.NEW & NOTEWORTHY High-molecular-weight linear polymers have gained traction in bioengineering applications. The addition of PEG3500k to lactated Ringer solution (LR) improved microvascular blood flow in arterioles and venules acutely after extracorporeal circulation (ECC) in a hamster model and improved functional capillary density up to 24 h after ECC. PEG3500k improved venular hemoglobin O2 saturation and oxygen delivery acutely after ECC and reduced inflammation in various organs compared to LR alone.

Predictors of Mortality in Extracorporeal Membrane Oxygenation Support Patients Following Major Trauma

INTRODUCTION

The usage of extracorporeal membrane oxygenation (ECMO) in trauma patients has increased significantly within the past decade. Despite increased research on ECMO application in trauma patients, there remains limited data on factors predicting morbidity and mortality outcome. Therefore, the primary objective of this study is to describe patient characteristics that are independently associated with mortality in ECMO therapy in trauma patients, to further guide future research.

METHODS

This retrospective study was conducted using the Trauma Quality Improvement Program database from 2010 to 2019. All adult (age ≥ 16 y) trauma patients that utilized ECMO were included. A Significant differences (P < 0.05) in demographic and clinical characteristics between groups were calculated using an independent t-test for normal distributed continuous values, a Mann-Whitney U test for non-normal distributed values, and a Pearson chi-square test for categorical values. A multivariable regression model was used to identify independent predictors for mortality. A survival flow chart was constructed by using the strongest predictive value for mortality and using the optimal cut-off point calculated by the Youden index.

RESULTS

Five hundred forty-two patients were included of whom 205 died. Multivariable analysis demonstrated that the female gender, ECMO within 4 h after presentation, a decreased Glasgow Coma Scale, increased age, units of blood in the first 4 h, and abbreviated injury score for external injuries were independently associated with mortality in ECMO trauma patients. It was found that an external abbreviated injury score of ≥3 had the strongest predictive value for mortality, as patients with this criterion had an overall 29.5% increased risk of death.

CONCLUSIONS

There is an ongoing increasing trend in the usage of ECMO in trauma patients. This study has identified multiple factors that are individually associated with mortality. However, more research must be done on the association between mortality and noninjury characteristics like Pao2/Fio2 ratio, acute respiratory distress syndrome classification, etc. that reflect the internal state of the patient.

Novel Size-Variable Dedicated Rodent Oxygenator for ECLS Animal Models-Introduction of the "RatOx" Oxygenator and Preliminary In Vitro Results

The overall survival rate of extracorporeal life support (ECLS) remains at 60%. Research and development has been slow, in part due to the lack of sophisticated experimental models. This publication introduces a dedicated rodent oxygenator ("RatOx") and presents preliminary in vitro classification tests. The RatOx has an adaptable fiber module size for various rodent models. Gas transfer performances over the fiber module for different blood flows and fiber module sizes were tested according to DIN EN ISO 7199. At the maximum possible amount of effective fiber surface area and a blood flow of 100 mL/min, the oxygenator performance was tested to a maximum of 6.27 mL O₂/min and 8.2 mL CO₂/min, respectively. The priming volume for the largest fiber module is 5.4 mL, while the smallest possible configuration with a single fiber mat layer has a priming volume of 1.1 mL. The novel RatOx ECLS system has been evaluated in vitro and has demonstrated a high degree of compliance with all pre-defined functional criteria for rodent-sized animal models. We intend for the RatOx to become a standard testing platform for scientific studies on ECLS therapy and technology.

Different Acute Kidney Injury Patterns after Renal Ischemia Reperfusion Injury and Extracorporeal Membrane Oxygenation in Mice

The use of extracorporeal membrane oxygenation (ECMO) is associated with acute kidney injury (AKI) in thoracic organ transplantation. However, multiple other factors contribute to AKI development after these procedures such as renal ischemia-reperfusion injury (IRI) due to hypo-perfusion of the kidney during surgery. In this study, we aimed to explore the kidney injury patterns in mouse models of ECMO and renal IRI. Kidneys of C57BL/6 mice were examined after moderate (35 min) and severe (45 min) unilateral transient renal pedicle clamping and 2 h of veno-venous ECMO. Renal injury markers, neutrophil infiltration, tubular transport function, pro-inflammatory cytokines, and renal heme oxygenase-1 (HO-1) expression were determined by immunofluorescence and qPCR. Both procedures caused AKI, but with different injury patterns. Severe neutrophil infiltration of the kidney was evident after renal IRI, but not following ECMO. Tubular transport function was severely impaired after renal IRI, but preserved in the ECMO group. Both procedures caused upregulation of pro-inflammatory cytokines in the renal tissue, but with different time kinetics. After ECMO, but not IRI, HO-1 was strongly induced in tubular cells indicating contact with hemolysis-derived proteins. After IRI, HO-1 was expressed on infiltrating myeloid cells in the tubulo-interstitial space. In conclusion, renal IRI and ECMO both caused AKI, but kidney damage after renal IRI was more pronounced including severe neutrophil infiltration and tubular transport impairment. Enhanced HO-1 expression in tubular cells after ECMO encourages limitation of hemolysis as a therapeutic approach to reduce ECMO-associated AKI.