Furosemide exacerbated the impairment of renal function, oxygenation and medullary damage in a rat model of renal ischemia/reperfusion induced AKI.

BACKGROUND: Perioperative acute kidney injury (AKI) caused by ischemia-reperfusion (IR) is a significant contributor to mortality and morbidity after major surgery. Furosemide is commonly used in postoperative patients to promote diuresis and reduce tissue edema. However, the effects of furosemide on renal microcirculation, oxygenation and function are poorly understood during perioperative period following ischemic insult. Herein, we investigated the effects of furosemide in rats subjected IR insult. METHODS: 24 Wistar albino rats were divided into 4 groups, with 6 in each; Sham-operated Control (C), Control + Furosemide (C + F), ischemia/reperfusion (IR), and IR + F. After induction of anesthesia (BL), supra-aortic occlusion was applied to IR and IR + F groups for 45 min followed by ongoing reperfusion for 15 min (T1) and 2 h (T2). Furosemide infusion was initiated simultaneously in the intervention groups after ischemia. Renal blood flow (RBF), vascular resistance (RVR), oxygen delivery (DO2ren) and consumption (VO2ren), sodium reabsorption (TNa+), oxygen utilization efficiency (VO2/TNa+), cortical (CµO2) and medullary (MµO2) microvascular oxygen pressures, urine output (UO) and creatinine clearance (Ccr) were measured. Biomarkers of inflammation, oxidative and nitrosative stress were measured and kidneys were harvested for histological analysis. RESULTS: IR significantly decreased RBF, mainly by increasing RVR, which was exacerbated in the IR + F group at T2 (2198 ± 879 vs 4233 ± 2636 dyne/s/cm5, p = 0.07). CµO2 (61.6 ± 6.8 vs 86 ± 6.6 mmHg) and MµO2 (51.1 ± 4.1 vs 68.7 ± 4.9 mmHg, p < 0.05) were both reduced after IR and did not improve by furosemide. Moreover, VO2/TNa+ increased in the IR + F group at T2 with respect to the IR group (IR: 3.3 ± 2 vs IR + F: 8.2 ± 10 p = 0.07) suggesting a possible deterioration of oxygen utilization. Ccr did not change, but plasma creatinine increased significantly in IR + F groups. Histopathology revealed widespread damage both in the cortex and medulla in IR, IR + F and C + F groups. CONCLUSION: Renal microvascular oxygenation, renal function, renal vascular resistance, oxygen utilization and damage were not improved by furosemide administration after IR insult. Our study suggests that furosemide may cause additional structural and functional impairment to the kidney following ischemic injury and should be used with caution.

Intra-renal microcirculatory alterations on non-traumatic hemorrhagic shock induced acute kidney injury in pigs.

Acute kidney injury (AKI) is frequently seen in patients with hemorrhagic shock due to hypotension, tissue hypoxia, and inflammation despite adequate resuscitation. There is a lack of information concerning the alteration of renal microcirculation and perfusion during shock and resuscitation. The aim of this study was to investigate the possible role of renal microcirculatory alterations on development of renal dysfunction in a pig model of non-traumatic hemorrhagic shock (HS) induced AKI.Fully instrumented female pigs were divided into the two groups as Control (n = 6) and HS (n = 11). HS was achieved by withdrawing blood until mean arterial pressure (MAP) reached around 50 mmHg. After an hour cessation period, fluid resuscitation with balanced crystalloid was started for the duration of 1 h. The systemic and renal hemodynamics, renal microcirculatory perfusion (contrast-enhanced ultrasound (CEUS)) and the sublingual microcirculation were measured.CEUS peak enhancement was significantly increased in HS during shock, early-, and late resuscitation indicating perfusion defects in the renal cortex (p < 0.05 vs. baseline, BL) despite a stable renal blood flow (RBF) and urine output. Following normalization of systemic hemodynamics, we observed persistent hypoxia (high lactate) and high red blood cell (RBC) velocity just after initiation of resuscitation resulting in further endothelial and renal damage as shown by increased plasma sialic acid (p < 0.05 vs. BL) and NGAL levels. We also showed that total vessel density (TVD) and functional capillary density (FCD) were depleted during resuscitation (p < 0.05).In this study, we showed that the correction of systemic hemodynamic variables may not be accompanied with the improvement of renal cortical perfusion, intra-renal blood volume and renal damage following fluid resuscitation. We suggest that the measurement of renal injury biomarkers, systemic and renal microcirculation can be used for guiding to the optimization of fluid therapies.

Hydroxyl Ethyl Starch (HES) Preserves Intrarenal Microcirculatory Perfusion Shown by Contrast-Enhanced Ultrasound (Ceus), and Renal Function in a Severe Hemodilution Model in Pigs.

ABSTRACT: Acute normovolemic hemodilution (ANH) is associated with low oxygen carrying capacity of blood and purposed to cause renal injury in perioperative setting. It is best accomplished in a perioperative setting by a colloid such as hydroxyl ethyl starch (HES) due its capacity to fill the vascular compartment and maintain colloidal pressure. However, alterations of intra renal microvascular perfusion, flow and its effects on renal function and damage during ANH has not been sufficiently clarified. Based on the extensive use of HES in the perioperative setting we tested the hypothesis that the use of HES during ANH is able to perfuse the kidney microcirculation adequately without causing renal dysfunction and injury in pigs. Hemodilution (n = 8) was performed by stepwise replacing blood with HES to hematocrit (Hct) levels of 20% (T1), 15% (T2), and 10% (T3). Seven control animals were investigated. Systemic and renal hemodynamics were monitored. Renal microcirculatory perfusion was visualized and quantified using contrast-enhanced ultrasound (CEUS) and laser speckle imaging (LSI). In addition, sublingual microcirculation was measured by handheld vital microscopy (HVM). Intrarenal mean transit time of ultrasound contrast agent (IRMTT-CEUS) was reduced in the renal cortex at Hct 10% in comparison to control at T3 (1.4 ±â€Š0.6 vs. 2.2 ±â€Š0.7 seconds, respectively, P < 0.05). Although renal function was preserved, the serum neutrophil gelatinase-associated lipocalin (NGAL) levels was higher at Hct 10% (0.033 ±â€Š0.004 pg/µg protein) in comparison to control at T3 (0.021 ±â€Š0.002 pg/µg protein. A mild correlation between CO and IRMTT (renal RBC velocity) (r -0.53; P = 0.001) and CO and NGAL levels (r 0.66; P = 0.001) was also found. Our results show that HES induced ANH is associated with a preserved intra renal blood volume, perfusion, and function in the clinical range of Hct (<15%). However, at severely low Hct (10%) ANH was associated with renal injury as indicated by increased NGAL levels. Changes in renal microcirculatory flow (CEUS and LSI) followed those seen in the sublingual microcirculation measured with HVM.

Sublingual Microcirculatory Evaluation of Extracorporeal Hemoadsorption with CytoSorb® in Abdominal Sepsis: A Case Report.

Cytokemia is associated with microcirculatory alterations often with persistent loss of coherence between the micro- and macrocirculation, linked to organ failure and poor outcome of septic patients. Addition of a hemoadsorbant filter to an extracorporeal circuit next to conventional treatment of septic shock results in the hematological clearance of cytokines, hypothetically leading to normalization of the microcirculation and thus organ perfusion. Bedside sublingual microcirculatory assessment using handheld vital microscopy allows real-time direct visualization of the microcirculation and its response to therapy. This is demonstrated in the present case report of an 83-year-old man admitted to our intensive care unit after surgical repair of a colonic perforation for fecal soiling after a low anterior resection for a rectum carcinoma, with leakage of bowel content at the resection site. The clinical course of this patient can be described as having undergone adequate surgical treatment taking away the source of the disease, followed by optimal support including antibiotic treatment in the ICU. However, during the course of his stay in the ICU, his condition deteriorated with symptoms consistent with septic shock. Our report shows that the addition of a hemoadsorbent (CytoSorb) to the continuous renal replacement therapy circuit was associated with an improvement in the condition of our severely ill patient with abdominal sepsis. Parallel to the clinical improvement of our patient, the functional parameters of the microcirculation also showed improvement suggesting that such a noninvasive real-time evaluation of the status of the microcirculation may be a sensitive diagnostic tool to monitor the effectiveness of hemoadsorbent therapy.

Increased Hepatic Microvascular Density, Oxygenation, and VEGF in the Hypertrophic Lobe following Portal Vein Embolization in Rabbits.

INTRODUCTION: The microvascular events following portal vein embolization (PVE) are poorly understood despite the pivotal role of the microcirculation in liver regeneration and tumor progression. We aimed to assess the changes in hepatic microvascular perfusion and neo-angiogenesis after experimental PVE. METHODS: PVE of the cranial liver lobes was performed in 12 New Zealand White rabbits divided into 2 groups of permanent (P-PVE) and reversible PVE (R-PVE), respectively. Hepatobiliary scintigraphy and CT were used to evaluate hepatic function and volume. Hepatic microcirculation was assessed using a handheld vital microscope (Cytocam) to measure microvascular density (total vessel density; TVD) before PVE, right after PVE, and 20 min after PVE, as well as at 14 days (D14 post-PVE) and 35 days (D35 post-PVE). Additionally, on D35, microvascular PO2 and liver parenchymal VEGF were assessed. RESULTS: Eleven rabbits were included after PVE (R-PVE, n = 5; P-PVE, n = 6). TVD in the nonembo-lized (hypertrophic) lobes was higher than in the embolized (atrophic) lobes of the P-PVE group at D35 post-PVE (36.7 ± 7.2 vs. 23.4 ± 4.9 mm/mm2; p < 0.05). In the R-PVE group, TVD in the nonembolized lobes was not increased at D35. Function and volume were increased in the nonembolized lobes of the P-PVE group compared to the embolized lobes, but not in the R-PVE group. Likewise, the mmicrovascular PO2 and VEGF staining rate were higher in the nonembolized lobes of the P-PVE group at D35 post-PVE. DISCUSSION/CONCLUSION: Successful volumetric and functional hypertrophy of the nonembolized lobe was accompanied by microvascular alterations featuring increased neo-angiogenesis, microvascular density, and microvascular oxygen pressure following P-PVE.

Kidney Microcirculation as a Target for Innovative Therapies in AKI.

Acute kidney injury (AKI) is a serious multifactorial conditions accompanied by the loss of function and damage. The renal microcirculation plays a crucial role in maintaining the kidney's functional and structural integrity for oxygen and nutrient supply and waste product removal. However, alterations in microcirculation and oxygenation due to renal perfusion defects, hypoxia, renal tubular, and endothelial damage can result in AKI and the loss of renal function regardless of systemic hemodynamic changes. The unique structural organization of the renal microvasculature and the presence of autoregulation make it difficult to understand the mechanisms and the occurrence of AKI following disorders such as septic, hemorrhagic, or cardiogenic shock; ischemia/reperfusion; chronic heart failure; cardiorenal syndrome; and hemodilution. In this review, we describe the organization of microcirculation, autoregulation, and pathophysiological alterations leading to AKI. We then suggest innovative therapies focused on the protection of the renal microcirculation and oxygenation to prevent AKI.

Corrections to "Microbubble Composition and Preparation for High-Frequency Contrast-Enhanced Ultrasound Imaging: In Vitro and In Vivo Evaluation".

In the above article [1], the authors regret that there was a mistake in calculating the mol% of the microbubble coating composition used. For all experiments, the unit in mg/mL was utilized and the conversion mistake only came when converting to mol% in order to define the ratio between the coating formulation components. The correct molecular weight of PEG-40 stearate is 2046.54 g/mol [2], [3], not 328.53 g/mol. On page 556, Table I should read as shown here.

Capillary Leukocytes, Microaggregates, and the Response to Hypoxemia in the Microcirculation of Coronavirus Disease 2019 Patients.

OBJECTIVES: In this study, we hypothesized that coronavirus disease 2019 patients exhibit sublingual microcirculatory alterations caused by inflammation, coagulopathy, and hypoxemia. DESIGN: Multicenter case-controlled study. SETTING: Two ICUs in The Netherlands and one in Switzerland. PATIENTS: Thirty-four critically ill coronavirus disease 2019 patients were compared with 33 healthy volunteers. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: The microcirculatory parameters quantified included total vessel density (mm × mm-2), functional capillary density (mm × mm-2), proportion of perfused vessels (%), capillary hematocrit (%), the ratio of capillary hematocrit to systemic hematocrit, and capillary RBC velocity (µm × s-1). The number of leukocytes in capillary-postcapillary venule units per 4-second image sequence (4 s-1) and capillary RBC microaggregates (4 s-1) was measured. In comparison with healthy volunteers, the microcirculation of coronavirus disease 2019 patients showed increases in total vessel density (22.8 ± sd 5.1 vs 19.9 ± 3.3; p < 0.0001) and functional capillary density (22.2 ± 4.8 vs 18.8 ± 3.1; p < 0.002), proportion of perfused vessel (97.6 ± 2.1 vs 94.6 ± 6.5; p < 0.01), RBC velocity (362 ± 48 vs 306 ± 53; p < 0.0001), capillary hematocrit (5.3 ± 1.3 vs 4.7 ± 0.8; p < 0.01), and capillary-hematocrit-to-systemic-hematocrit ratio (0.18 ± 0.0 vs 0.11 ± 0.0; p < 0.0001). These effects were present in coronavirus disease 2019 patients with Sequential Organ Failure Assessment scores less than 10 but not in patients with Sequential Organ Failure Assessment scores greater than or equal to 10. The numbers of leukocytes (17.6 ± 6.7 vs 5.2 ± 2.3; p < 0.0001) and RBC microaggregates (0.90 ± 1.12 vs 0.06 ± 0.24; p < 0.0001) was higher in the microcirculation of the coronavirus disease 2019 patients. Receiver-operating-characteristics analysis of the microcirculatory parameters identified the number of microcirculatory leukocytes and the capillary-hematocrit-to-systemic-hematocrit ratio as the most sensitive parameters distinguishing coronavirus disease 2019 patients from healthy volunteers. CONCLUSIONS: The response of the microcirculation to coronavirus disease 2019-induced hypoxemia seems to be to increase its oxygen-extraction capacity by increasing RBC availability. Inflammation and hypercoagulation are apparent in the microcirculation by increased numbers of leukocytes and RBC microaggregates.

Hemodilution causes glycocalyx shedding without affecting vascular endothelial barrier permeability in rats.

BACKGROUND: The consequences of acute normovolemic hemodilution (ANH) following different types of fluids on the different components of the glycocalyx and on vascular barrier permeability (VBP) remain unknown. AIM: The aim of the study was to investigate whether the microcirculatory disruption and glycocalyx shedding induced by ANH alters VBP and whether this is affected by the composition and volume of the resuscitation fluid. MATERIALS AND METHODS: Anesthetized Wistar albino rats (n=24) underwent stepwise ANH at hematocrit levels of 35%, 25%, 20%, and 15% induced by the exchange of blood with 6% balanced hydroxyethyl starch (1:1), balanced crystalloid (1:3), and normal saline (NS) (1:3). Glycocalyx-shed products were measured at each level of hemodilution. VBP was reflected in the decay of fluorescence dyes of different molecular size and their plasma retention ratios. Edema was assessed by measuring organ water content and muscle microcirculation by hand-held videomicroscopy. RESULTS: NS caused increased degradation of heparan sulfate and hyaluronan compared with the control group (P=0.003, P=0.004, respectively). Neither VBP nor tissue edema was affected by the fluid used. The total and perfused vessel densities within the microcirculation of muscle tissue decreased at hematocrit 15% in the balanced crystalloid (P=0.02) and NS groups only (P<0.0001, P=0.0003, respectively) compared with baseline. CONCLUSIONS: Balanced colloid solution preserved the glycocalyx layer better than balanced and unbalanced crystalloid solutions while maintaining the microcirculatory function associated with an improved total intravascular volume. Among the fluids tested, NS caused the most microcirculatory alterations. While ANH caused the degradation of glycocalyx components regardless of fluid, it did not disrupt the vascular barrier as indicated by macromolecular leakage. RELEVANCE FOR PATIENTS: The results of this study provide insight into the choice of fluid for optimal perioperative fluid management and the consequences of fluid type on the vascular barrier, glycocalyx, and microcirculation.

Assessment of sublingual microcirculation in critically ill patients: consensus and debate.

The main concern in shock and resuscitation is whether the microcirculation can carry adequate oxygen to the tissues and remove waste. Identification of an intact coherence between macro- and microcirculation during states of shock and resuscitation shows a functioning regulatory mechanism. However, loss of hemodynamic coherence between the macro and microcirculation can be encountered frequently in sepsis, cardiogenic shock, or any hemodynamically compromised patient. This loss of hemodynamic coherence results in an improvement in macrohemodynamic parameters following resuscitation without a parallel improvement in microcirculation resulting in tissue hypoxia and tissue compromise. Hand-held vital microscopes (HVMs) can visualize the microcirculation and help to diagnose the nature of microcirculatory shock. Although treatment with the sole aim of recruiting the microcirculation is as yet not realized, interventions can be tailored to the needs of the patient while monitoring sublingual microcirculation. With the help of the newly introduced software, called MicroTools, we believe sublingual microcirculation monitoring and diagnosis will be an essential point-of-care tool in managing shock patients.

Resuscitation with PEGylated carboxyhemoglobin preserves renal cortical oxygenation and improves skeletal muscle microcirculatory flow during endotoxemia.

PEGylated carboxyhemoglobin (PEGHbCO), which has carbon monoxide-releasing properties and plasma expansion and oxygen-carrying properties, may improve both skeletal microcirculatory flow and renal cortical microcirculatory Po2 (CµPo2) and, subsequently, limit endotoxemia-induced acute kidney injury. Anesthetized, ventilated Wistar albino rats (n = 44) underwent endotoxemic shock. CµPo2 was measured in exposed kidneys using a phosphorescence-quenching method. Rats were randomly assigned to the following five groups: 1) unresuscitated lipopolysaccharide (LPS), 2) LPS + Ringer's acetate (RA), 3) LPS + RA + 0.5 µg·kg·-1min-1 norepinephrine (NE), 4) LPS + RA + 320 mg/kg PEGHbCO, and 5) LPS + RA + PEGHbCO + NE. The total volume was 30 mL/kg in each group. A time control animal group was used. Skeletal muscle microcirculation was assessed by handheld intravital microscopy. Kidney immunohistochemistry and myeloperoxidase-stained leukocytes in glomerular and peritubular areas were analyzed. Endotoxemia-induced histological damage was assessed. Plasma levels of IL-6, heme oxygenase-1, malondialdehyde, and syndecan-1 were assessed by ELISA. CµPo2 was higher in the LPS + RA + PEGHbCO-resuscitated group, at 35 ± 6mmHg compared with 21 ± 12 mmHg for the LPS+RA group [mean difference: -13.53, 95% confidence interval: (-26.35; -0.7156), P = 0.035]. The number of nonflowing, intermittent, or sluggish capillaries was smaller in groups infused with PEGHbCO compared with RA alone (P < 0.05), while the number of normally perfused vessels was greater (P < 0.05). The addition of NE did not further improve CµPo2 or microcirculatory parameters. Endotoxemia-induced kidney immunohistochemistry and histological alterations were not mitigated by PEGHbCO 1 h after resuscitation. Renal leukocyte infiltration and plasma levels of biomarkers were similar across groups. PEGHbCO enhanced CµPo2 while restoring skeletal muscle microcirculatory flow in previously nonflowing capillaries. PEGHbCO should be further evaluated as a resuscitation fluid in mid- to long-term models of sepsis-induced acute kidney injury.

Case Report: Sublingual Microcirculatory Alterations in a Covid-19 Patient With Subcutaneous Emphysema, Venous Thrombosis, and Pneumomediastinum.

The Corona virus disease 2019 (Covid-19) has brought a wide range of challenges in intensive care medicine. Understanding of the pathophysiology of Covid-19 relies on interpreting of its impact on the vascular, particularly microcirculatory system. Herein we report on the first use of the latest generation hand-held vital microscope to evaluate the sublingual microcirculation in a Covid-19 patient with subcutaneous emphysema, venous thrombosis and pneumomediastinum. Remarkably, microcirculatory parameters of the patient were increased during the exacerbation period, which is not a usual finding in critically ill patients mostly presenting with a loss of hemodynamic coherence. In contrast, recovery from the disease led to a subsequent amelioration of these parameters. This report clearly shows the importance of microcirculatory monitoring for evaluating the course and the adequacy of therapy in Covid-19 patients.

Leukocyte-Endothelium Interaction in the Sublingual Microcirculation of Coronary Artery Bypass Grafting Patients.

OBJECTIVE: The aim of this study was to apply an innovative methodology to incident dark-field (IDF) imaging in coronary artery bypass grafting (CABG) patients for the identification and quantification of rolling leukocytes along the sublingual microcirculatory endothelium. METHODS: This study was a post hoc analysis of a prospective study that evaluated the perioperative course of the sublingual microcirculation in CABG patients. Video images were captured using IDF imaging following the induction of anesthesia (T0) and cardiopulmonary bypass (CPB) (T1) in 10 patients. Rolling leukocytes were identified and quantified using frame averaging, which is a technique that was developed for correctly identifying leukocytes. RESULTS: The number of rolling leukocytes increased significantly from T0 (7.5 [6.4-9.1] leukocytes/capillary-postcapillary venule/4 s) to T1 (14.8 [13.2-15.5] leukocytes/capillary-postcapillary venule/4 s) (p < 0.0001). A significant increase in systemic leukocyte count was also detected from 7.4 ± 0.9 × 109/L (preoperative) to 12.4 ± 4.4 × 109/L (postoperative) (p < 0.01). CONCLUSION: The ability to directly visualize leukocyte-endothelium interaction using IDF imaging facilitates the diagnosis of a systemic inflammatory response after CPB via the identification of rolling leukocytes. Integration of the frame averaging algorithm into the software of handheld vital microscopes may enable the use of microcirculatory leukocyte count as a real-time parameter at the bedside.

Attenuated cardiac function degradation in ex vivo pig hearts.

Isolated hearts offer the opportunity to evaluate heart function, treatments, and diagnostic tools without in vivo factor interference. However, the early loss of cardiac function and edema occur over time and do limit the duration of the experiment. This research focuses on delaying these limitations using optimal blood control. This study examines whether blood conditioning by means of the combination of blood predilution and hemodialysis can significantly reduce cardiac function degradation. Slaughterhouse porcine hearts were revived in the PhysioHeart™ platform to restore physiological cardiac performance. Twelve hearts were divided into a control group and a dialysis group; in the latter group, hemodialysis was attached to the blood reservoir. Cardiac hemodynamics and blood parameters were recorded and evaluated. Blood conditioning significantly reduced the loss of cardiac pump function (control group vs dialysis group, -14.9 ± 6.3%/h vs -9.7 ± 2.7%/h) and loss of cardiac output (control group vs dialysis group, -11.8 ± 3.4%/h vs -5.9 ± 2.0%/h). Hemodialysis resulted in physiological and stable blood parameters, whereas in the control group ions reached pathological values, while interstitial edema still occurred. The combination of blood predilution and hemodialysis significantly attenuated ex vivo cardiac function degradation and delayed the loss of cardiac hemodynamics. We hypothesized that besides electrolyte and metabolic control, the hemodialysis-accompanied increase in hematocrit resulted in improved oxygen transport. This could have temporarily compensated the deleterious effect of an increased oxygen-diffusion distance due to edema in the dialysis group and resulted in less progression of cell decay. Clinically validated measures delaying edema might improve the effectiveness of the PhysioHeart™ platform.

Investigating the physiology of normothermic ex vivo heart perfusion in an isolated slaughterhouse porcine model used for device testing and training.

BACKGROUND: The PhysioHeart™ is a mature acute platform, based isolated slaughterhouse hearts and able to validate cardiac devices and techniques in working mode. Despite perfusion, myocardial edema and time-dependent function degradation are reported. Therefore, monitoring several variables is necessary to identify which of these should be controlled to preserve the heart function. This study presents biochemical, electrophysiological and hemodynamic changes in the PhysioHeart™ to understand the pitfalls of ex vivo slaughterhouse heart hemoperfusion. METHODS: Seven porcine hearts were harvested, arrested and revived using the PhysioHeart™. Cardiac output, SaO2, glucose and pH were maintained at physiological levels. Blood analyses were performed hourly and unipolar epicardial electrograms (UEG), pressures and flows were recorded to assess the physiological performance. RESULTS: Normal cardiac performance was attained in terms of mean cardiac output (5.1 ± 1.7 l/min) and pressures but deteriorated over time. Across the experiments, homeostasis was maintained for 171.4 ± 54 min, osmolarity and blood electrolytes increased significantly between 10 and 80%, heart weight increased by 144 ± 41 g, free fatty acids (- 60%), glucose and lactate diminished, ammonia increased by 273 ± 76% and myocardial necrosis and UEG alterations appeared and aggravated. Progressively deteriorating electrophysiological and hemodynamic functions can be explained by reperfusion injury, waste product intoxication (i.e. hyperammonemia), lack of essential nutrients, ion imbalances and cardiac necrosis as a consequence of hepatological and nephrological plasma clearance absence. CONCLUSIONS: The PhysioHeart™ is an acute model, suitable for cardiac device and therapy assessment, which can precede conventional animal studies. However, observations indicate that ex vivo slaughterhouse hearts resemble cardiac physiology of deteriorating hearts in a multi-organ failure situation and signalize the need for plasma clearance during perfusion to attenuate time-dependent function degradation. The presented study therefore provides an in-dept understanding of the sources and reasons causing the cardiac function loss, as a first step for future effort to prolong cardiac perfusion in the PhysioHeart™. These findings could be also of potential interest for other cardiac platforms.

Effect of Polyethylene-glycolated Carboxyhemoglobin on Renal Microcirculation in a Rat Model of Hemorrhagic Shock.

BACKGROUND: Primary resuscitation fluid to treat hemorrhagic shock remains controversial. Use of hydroxyethyl starches raised concerns of acute kidney injury. Polyethylene-glycolated carboxyhemoglobin, which has carbon monoxide-releasing molecules and oxygen-carrying properties, was hypothesized to sustain cortical renal microcirculatory PO2 after hemorrhagic shock and reduce kidney injury. METHODS: Anesthetized and ventilated rats (n = 42) were subjected to pressure-controlled hemorrhagic shock for 1 h. Renal cortical PO2 was measured in exposed kidneys using a phosphorescence quenching method. Rats were randomly assigned to six groups: polyethylene-glycolated carboxyhemoglobin 320 mg · kg, 6% hydroxyethyl starch (130/0.4) in Ringer's acetate, blood retransfusion, diluted blood retransfusion (~4 g · dl), nonresuscitated animals, and time control. Nitric oxide and heme oxygenase 1 levels were determined in plasma. Kidney immunohistochemistry (histologic scores of neutrophil gelatinase-associated lipocalin and tumor necrosis factor-α) and tubular histologic damages analyses were performed. RESULTS: Blood and diluted blood restored renal PO2 to 51 ± 5 mmHg (mean difference, -18; 95% CI, -26 to -11; P < 0.0001) and 47 ± 5 mmHg (mean difference, -23; 95% CI, -31 to -15; P < 0.0001), respectively, compared with 29 ± 8 mmHg for hydroxyethyl starch. No differences between polyethylene-glycolated carboxyhemoglobin and hydroxyethyl starch were observed (33 ± 7 mmHg vs. 29 ± 8 mmHg; mean difference, -5; 95% CI, -12 to 3; P = 0.387), but significantly less volume was administered (4.5 [3.3-6.2] vs. 8.5[7.7-11.4] ml; mean rank difference, 11.98; P = 0.387). Blood and diluted blood increased the plasma bioavailability of nitric oxide compared with hydroxyethyl starch (mean rank difference, -20.97; P = 0.004; and -17.13; P = 0.029, respectively). No changes in heme oxygenase 1 levels were observed. Polyethylene-glycolated carboxyhemoglobin limited tubular histologic damages compared with hydroxyethyl starch (mean rank difference, 60.12; P = 0.0012) with reduced neutrophil gelatinase-associated lipocalin (mean rank difference, 84.43; P < 0.0001) and tumor necrosis factor-α (mean rank difference, 49.67; P = 0.026) histologic scores. CONCLUSIONS: Polyethylene-glycolated carboxyhemoglobin resuscitation did not improve renal PO2 but limited tubular histologic damages and neutrophil gelatinase-associated lipocalin upregulation after hemorrhage compared with hydroxyethyl starch, whereas a lower volume was required to sustain macrocirculation.

Glycocalyx Degradation Is Independent of Vascular Barrier Permeability Increase in Nontraumatic Hemorrhagic Shock in Rats.

BACKGROUND: Glycocalyx shedding after traumatic hemorrhagic or septic shock, as well as different resuscitation fluids, has been causally linked to increased vascular barrier permeability (VBP) resulting in tissue edema. In nontraumatic hemorrhagic shock (NTHS), it remains questionable whether glycocalyx degradation in itself results in an alteration of VBP. The composition of fluids can also have a modulatory effect on glycocalyx shedding and VBP. We hypothesized that the shedding of the glycocalyx during NTHS has little effect on VBP and that the composition of fluids can modulate these effects. METHODS: Fully instrumented Wistar-albino rats were subjected to a pressure-controlled NTHS (mean arterial pressure of 30 mm Hg) for 60 minutes. Animals were fluid resuscitated with Ringer's acetate, balanced hydroxyethyl starch (HES) solution, or 0.9% normal saline to a mean arterial pressure of 80 mm Hg and compared with shams or nonresuscitated NTHS. Glycocalyx shed products were determined at baseline and 60 minutes after fluid resuscitation. Skeletal muscle microcirculation was visualized using handheld vital microscopy. VBP changes were assessed using plasma decay of 3 fluorescent dyes (40- and 500-kDa dextran and 70-kDa albumin), Evans blue dye exclusion, intravital fluorescence microscopy, and determination of tissue edema (wet/dry weight ratio). RESULTS: All glycocalyx shedding products were upgraded as a result of NTHS. Syndecan-1 significantly increased in NTHS (mean difference, -1668; 95% confidence interval [CI], -2336 to -1001; P < .0001), balanced crystalloid (mean difference, -964.2; 95% CI, -1492 to -436.4; P = .0001), and HES (mean difference, -1030; 95% CI, -1594 to -465.8; P = .0001) groups at the end of the experiment compared to baseline. Hyaluronan levels were higher at the end of the experiment in nonresuscitated NTHS (-923.1; 95% CI, -1216 to -630; P = .0001) and balanced crystalloid (-1039; 95% CI, -1332 to -745.5; P = .0001) or HES (-394.2; 95% CI, -670.1 to -118.3; P = .0027) groups compared to controls. Glycocalyx shedding resulted in microcirculation alterations as observed by handheld video microscopy. Total vessel density was altered in the normal saline (mean difference, 4.092; 95% CI, 0.6195-7.564; P = .016) and hemorrhagic shock (mean difference, 5.022; 95% CI, 1.55-8.495; P = .0024) groups compared to the control group, as well as the perfused vessel density and mean flow index. Despite degradation of endothelial glycocalyx, VBP as determined by 4 independent assays remained intact and continued to be so following fluid resuscitation. CONCLUSIONS: NTHS induced glycocalyx shedding and microcirculation alterations, without altering VBP. Fluid resuscitation partially restored the microcirculation without altering VBP. These results challenge the concept that the glycocalyx barrier is a significant contributor to VBP.

Assessment of hepatic microvascular flow and density in patients undergoing preoperative portal vein embolization.

BACKGROUND: The microvascular effects occurring after unilateral preoperative portal vein embolization (PVE) are poorly understood. The aim of this study was to assess the microvascular changes in the embolized and the non-embolized lobes after right PVE. METHODS: Videos of the hepatic microcirculation in patients undergoing right hemihepatectomy following PVE were recorded using a handheld vital microscope (Cytocam) based on incident dark field imaging. Hepatic microcirculation was measured in the embolized and the non-embolized lobes at laparotomy, 3-6 weeks after PVE. The following microcirculatory parameters were assessed: total vessel density (TVD), microcirculatory flow index (MFI), proportion of perfused vessel (PPV), perfused vessel density (PVD), sinusoidal diameter (SinD) and the absolute red blood cell velocity (RBCv). RESULTS: 16 patients after major liver resection were included, 8 with and 8 without preoperative PVE. Microvascular density parameters were higher in the non-embolized lobes when compared to the embolized lobes (TVD: 40.3 ± 8.9 vs. 26.8 ± 4.6 mm/mm2 (p < 0.003), PVD: 40.3 ± 8.8 vs. 26.7 ± 4.7 mm/mm2 (p < 0.002), SinD: 9.2 ± 1.7 vs. 6.3 ± 0.8 µm (p < 0.040)). RBCv, PPV and the MFI were not significantly different. CONCLUSION: The non-embolized lobe has a significantly higher microvascular density, however without differences in microvascular flow. These findings indicate increased angiogenesis in the hypertrophic lobe.