Subnormothermic isolated organ perfusion with Nicorandil increased cold ischemic tolerance of liver in experimental model

BACKGROUND: The cold ischemia –reperfusion injury may lead to microcirculatory disturbances, hepatocellular swelling, inflammation, and organ dysfunction. Nicorandil is an anti-ischemic, ATP-sensitive potassium (KATP) channel opener drug and has proved its effectiveness against hepatic Ischemia/Reperfusion (I/R) injury. OBJECTIVE: This study aimed to investigate the effect of Nicorandil on mitochondrial apoptosis, oxidative stress, inflammation, histopathological changes, and cold ischemic tolerance of the liver in an ex vivo experimental isolated-organ-perfusion model. METHODS: We used an ex vivo isolated rat liver perfusion system for this study. The grafts were retrieved from male Wistar rats (n = 5 in each), preserved in cold storage (CS) for 2 or 4 hours (group 1, 2), or perfused for 2 or 4 hours (group 3, 4) immediately after removal with Krebs Henseleit Buffer (KHB) solution or Nicorandil containing KHB solution under subnormothermic (22–25°C) conditions (group 5, 6). After 15 minutes incubation at room temperature, the livers were reperfused with acellular, oxygenated solution under normothermic condition for 60 minutes. RESULTS: In the Nicorandil perfused groups, significantly decreased liver enzymes, GLDH, TNF-alpha, and IL-1ß were measured from the perfusate. Antioxidant enzymactivity was higher in the perfused groups. Histopathological examination showed ameliorated tissue deterioration, preserved parenchymal structure, decreased apoptosis, and increased Bcl-2 activity in the Nicorandil perfused groups. CONCLUSIONS: Perfusion with Nicorandil containing KHB solution may increase cold ischemic tolerance of the liver via mitochondrial protection which can be a potential therapeutic target to improve graft survival during transplantation.

Coronary Large Conductance Ca2+-Activated K+ Channel Dysfunction in Diabetes Mellitus

Diabetes mellitus (DM) is an independent risk of macrovascular and microvascular complications, while cardiovascular diseases remain a leading cause of death in both men and women with diabetes. Large conductance Ca2+-activated K+ (BK) channels are abundantly expressed in arteries and are the key ionic determinant of vascular tone and organ perfusion. It is well established that the downregulation of vascular BK channel function with reduced BK channel protein expression and altered intrinsic BK channel biophysical properties is associated with diabetic vasculopathy. Recent efforts also showed that diabetes-associated changes in signaling pathways and transcriptional factors contribute to the downregulation of BK channel expression. This manuscript will review our current understandings on the molecular, physiological, and biophysical mechanisms that underlie coronary BK channelopathy in diabetes mellitus.

Plasma Renin Concentration in Critically Ill COVID-19 Patients

Investigations of plasma renin concentration as a marker of organ perfusion in several intensive care settings have shown a significant correlation between its increase and a lack of perfusion in critical tissues, especially in septic patients. Castillo et al. proposed that activation of the non-canonical pathway of the renin–angiotensin–aldosterone system could improve cardiovascular homeostasis under COVID-19. During the first wave of COVID-19, we preliminarily enrolled a small cohort of subjects admitted to the Intensive Care Unit with a diagnosis of COVID-19 and acute respiratory distress syndrome. Their plasma renin value was measured in the first 24 h (T0), in the following 72 h (T1), and after one week (T2). In eight patients, we observed a higher plasma renin concentration—patients with difficulty weaning and in non-survivors. This is a preliminary observation. The variation of plasma renin levels in a septic condition is known, but settings such as COVID-19 infection have recently been investigated, showing a correlation with angiotensin-converting enzyme 2 receptor expression and functionality; in the near future, it will be interesting to have more data about its variation and value in COVID-19 patients.

Assessment and Management of Hypoperfusion in Sepsis and Septic Shock

Diagnosis of organ hypoperfusion in patient with sepsis is not always straightforward which makes septic shock definition, diagnosis, and early treatment are major challenges that emergency physicians and intensivist must deal with in their daily practice. Normal blood pressure does not always mean good organ perfusion, which means patient might develop septic shock, yet they are not hypotensive. There are several indices that could be used in combination to diagnose and manage hypoperfusion in patients with septic shock. Fluid resuscitation and vasopressor administration along with infection sources control are the cornerstones in septic shock management. This chapter will cover indices that can be used to diagnose hypoperfusion, type and amount of fluid and vasopressor that can be used in resuscitating septic shock patients.

Generation of vascular chimerism within donor organs

Whole organ perfusion decellularization has been proposed as a promising method to generate non-immunogenic organs from allogeneic and xenogeneic donors. However, the ability to recellularize organ scaffolds with multiple patient-specific cells in a spatially controlled manner remains challenging. Here, we propose that replacing donor endothelial cells alone, while keeping the rest of the organ viable and functional, is more technically feasible, and may offer a significant shortcut in the efforts to engineer transplantable organs. Vascular decellularization was achieved ex vivo, under controlled machine perfusion conditions, in various rat and porcine organs, including the kidneys, liver, lungs, heart, aorta, hind limbs, and pancreas. In addition, vascular decellularization of selected organs was performed in situ, within the donor body, achieving better control over the perfusion process. Human placenta-derived endothelial progenitor cells (EPCs) were used as immunologically-acceptable human cells to repopulate the luminal surface of de-endothelialized aorta (in vitro), kidneys, lungs and hind limbs (ex vivo). This study provides evidence that artificially generating vascular chimerism is feasible and could potentially pave the way for crossing the immunological barrier to xenotransplantation, as well as reducing the immunological burden of allogeneic grafts.

Measuring flavin mononucleotide concentrations in whole blood, red cell based or acellular perfusate samples by fluorescence spectrometry

Flavin mononucleotide (FMN) is non-covalently bound to complex I of the mitochondrial respiratory chain. During ischemia-reperfusion injury, reduced FMN is released from complex I, leaving the complex impaired. In literature, FMN measured during ex situ organ perfusion has been considered as a biomarker for organ graft quality. With this protocol the FMN concentrations in perfusate samples taken during organ perfusion can be estimated quickly and easily by fluorescence spectrometry. The use of non-binding plates is essential. A fresh standard curve using riboflavin 5'-monophosphate sodium salt hydrate must be prepared every day. To quantitatively compare sample concentrations between different plates, it is advisable to include an internal standard. This internal standard is best prepared by pooling samples from experiments that use the same perfusate composition. This assay will work for samples acquired from whole blood, red cell based solutions or acellular solutions.

Impella RP versus pharmacologic vasoactive treatment in profound cardiogenic shock due to right ventricular failure: Unloading and end-organ perfusion in a large animal model

Funding Acknowledgements Type of funding sources: Foundation. Main funding source(s): The Danish Heart Foundation Unrestricted research grant from Abiomed Background No strong evidence exists regarding the treatment of cardiogenic shock (CS) caused by acute right ventricular (RV) failure which has mainly consisted of vasoactive drugs. There is expert agreement that treatment with the recently developed Impella RP is feasible, but no previous studies have compared vasoactive treatment strategies with the Impella RP in terms of cardiac unloading and end-organ perfusion. Hypothesis Treatment with the Impella RP device will be associated with lower RV myocardial workload (pressure-volume area) compared to vasoactive treatment strategies and can furthermore be achieved without compromising organ perfusion. Methods CS was induced by a stepwise injection of polyvinyl alcohol microspheres into the right coronary artery in twenty adult female Danish landrace pigs weighing 75-80 kg. After induction of CS, the pigs were allocated to one of the two interventions for 180 minutes: 1) vasoactive therapy comprised a continuous infusion of norepinephrine (0.1 µg/kg/min) for the first 30 minutes, supplemented by an infusion of milrinone (0.4 µg/kg/min) for the remaining 150 minutes or 2) immediate insertion of and treatment with the Impella RP. The results are presented as median [Q1;Q3]. Results Treatment with the Impella RP was associated with a lower RV workload compared to the vasoactive group, while no difference was observed with regards to left ventricular workload among intervention groups, Figure 1. Renal venous oxygen saturation increased to a similar degree following both interventions compared to the state of CS. A trend towards a higher cerebral venous oxygen saturation was observed with norepinephrine compared to Impella RP (Impella RP 51 [47;61] % vs Norepinephrine 62 [57;71] % ; p = 0.07), which became significantly higher with the addition of milrinone (Impella RP 45 [32;63] % vs Norepinephrine +Milrinone 73 [66;81] %; p = 0.002). Conclusion In this large animal model of profound CS caused by predominantly RV failure the Impella RP unloaded the failing RV. The vasoactive treatment, however, caused a higher cerebral venous oxygen saturation, while both interventions increased renal venous oxygen saturation to a similar degree. Abstract Figure 1