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

Renal protection after hemorrhagic shock in rats: Possible involvement of SUMOylation

Hemorrhagic shock (HS), a leading cause of preventable death, is characterized by severe blood loss and inadequate tissue perfusion. Reoxygenation of ischemic tissues exacerbates organ damage through ischemia-reperfusion injury. SUMOylation has been shown to protect neurons after stroke and is upregulated in response to cellular stress. However, the role of SUMOylation in organ protection after HS is unknown. This study aimed to investigate SUMOylation-mediated organ protection following HS. Male Wistar rats were subjected to HS (blood pressure of 40 ± 2 mmHg, for 90 min) followed by reperfusion. Blood, kidney, and liver samples were collected at various time points after reperfusion to assess organ damage and investigate the profile of SUMO1 and SUMO2/3 conjugation. In addition, human kidney cells (HK-2), treated with the SUMOylation inhibitor TAK-981 or overexpressing SUMO proteins, were subjected to oxygen and glucose deprivation to investigate the role of SUMOylation in hypoxia/reoxygenation injury. The animals presented progressive multiorgan dysfunction, except for the renal system, which showed improvement over time. Compared to the liver, the kidneys displayed distinct patterns in terms of oxidative stress, apoptosis activation, and tissue damage. The global level of SUMO2/3 in renal tissue was also distinct, suggesting a differential role. Pharmacological inhibition of SUMOylation reduced cell viability after hypoxia-reoxygenation damage, while overexpression of SUMO1 or SUMO2 protected the cells. These findings suggest that SUMOylation might play a critical role in cellular protection during ischemia-reperfusion injury in the kidneys, a role not observed in the liver. This difference potentially explains the renal resilience observed in HS animals when compared to other systems.

"Shock kidney-like Appearance": Objective evaluation of renal color changes in hemorrhagic shock deaths

Severe bleeding due to various traumatic injuries can cause hemorrhagic shock, which is difficult to diagnose using forensic medicine. Therefore, we defined the difference in color between the renal cortex and medulla observed in hemorrhagic shock deaths as "shock kidney-like appearance (SKLA)" and digitally analyzed the color difference with a digital camera and color analysis software. The aim of this study was to develop and evaluate a method for objectively determining SKLA and improve the accuracy of forensic diagnosis. We examined the kidneys of 122 cases (83 males and 39 females; average age, 64.8 years) autopsied at our facility. Using Image J, we analyzed the color of the cortex and medulla from photographs of bisected kidneys. We defined the color difference between the cortex and medulla in the L*a*b* color space as cortical-medullary color difference and performed a comparative analysis between the hemorrhage and control groups. Significant differences were observed in ΔL* and Δa* values between the two groups (p < 0.05 and p < 0.001, respectively). Analysis of Δa* values showed that the cortex was less reddish than the medulla in the hemorrhage group. The cutoff value for determining SKLA was set at Δa* = -1.33 (sensitivity, 0.79; specificity, 0.81; AUC, 0.859). Traditional evaluations of color rely on subjective assessments, which raise issues of reliability and reproducibility. This study successfully overcame the limitations of subjective evaluation by objectively assessing cortical-medullary color difference in the kidneys. Our results represent an important step towards improving the objectivity of color evaluations.

Renal Microcirculation and Function in a Pig Model of Hemorrhagic Shock Resuscitation with Norepinephrine

RATIONALE

Norepinephrine (NE) is commonly used in combination with fluid during resuscitation of hemorrhagic shock, however its impact on kidney microcirculation, oxygenation and function is still unknown in this setting.

OBJECTIVES

During hemorrhagic shock resuscitation, does a combination of fluid and norepinephrine affect kidney oxygenation tension, kidney microcirculatory perfusion and 48-hour kidney function, as compared to fluid alone?

METHODS

Hemorrhagic shock was induced in 24 pigs and 8 pigs were included as sham. Resuscitation of hemorrhagic shock was performed, using a closed-loop device, either by fluid alone (0.9% NaCl, Fluid group) or associated with the administration of NE at two doses (moderate dose: mean rate of 0.64 µg.kg-1.min-1 and high dose: mean rate of 1.57 µg.kg-1.min-1) in order to obtain SAP (systolic arterial pressure) target of 80-90 mmHg. Resuscitation was followed by transfusion of the withdrawn blood.

MEASUREMENTS AND MAIN RESULTS

The amount of fluid required to reach SAP target was lower in NE groups than in Fluid group with subsequent less hemodilution. Norepinephrine restored kidney microcirculation, oxygenation, and function in a manner comparable to that achieved with fluid resuscitation alone. There were no histological differences among animals resuscitated with Fluid or with NE.

CONCLUSION

In pigs with hemorrhagic shock, resuscitation with a combination of NE and fluid restored kidney microcirculation and oxygenation, as well as renal function, in a manner comparable to fluid resuscitation alone and without differences between the two NE doses. NE administration led to a fluid volume sparing effect with subsequently less hemodilution.

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.

Fluids of the Future

Fluids are a vital tool in the armament of acute care clinicians in both civilian and military resuscitation. We now better understand complications from inappropriate resuscitation with currently available fluids; however, fluid resuscitation undeniably remains a life-saving intervention. Military research has driven the most significant advances in the field of fluid resuscitation and is currently leading the search for the fluids of the future. The veterinary community, much like our civilian human counterparts, should expect the fluid of the future to be the fruit of military research. The fluids of the future not only are expected to improve patient outcomes but also be field expedient. Those fluids should be compatible with military environments or natural disaster environments. For decades, military personnel and disaster responders have faced the peculiar demands of austere environments, prolonged field care, and delayed evacuation. Large scale natural disasters present field limitations often similar to those encountered in the battlefield. The fluids of the future should, therefore, have a long shelf-life, a small footprint, and be resistant to large temperature swings, for instance. Traumatic brain injury and hemorrhagic shock are the leading causes of preventable death for military casualties and a significant burden in civilian populations. The military and civilian health systems are focusing efforts on field-expedient fluids that will be specifically relevant for the management of those conditions. Fluids are expected to be compatible with blood products, increase oxygen-carrying capabilities, promote hemostasis, and be easy to administer in the prehospital setting, to match the broad spectrum of current acute care challenges, such as sepsis and severe systemic inflammation. This article will review historical military and civilian contributions to current resuscitation strategies, describe the expectations for the fluids of the future, and describe select ongoing research efforts with a review of current animal data.

Automated quantification of tissue red blood cell perfusion as a new resuscitation target

PURPOSE OF REVIEW

Identification of insufficient tissue perfusion is fundamental to recognizing circulatory shock in critically ill patients, and the primary target to restore adequate oxygen delivery. However, the concept of tissue perfusion remains ill-defined and out-of-reach for clinicians as point-of-care resuscitation target. Even though handheld vital microscopy (HVM) provides the technical prerequisites to collect information on tissue perfusion in the sublingual microcirculation, challenges in image analysis prevent quantification of tissue perfusion and manual analysis steps prohibit point-of-care application. The present review aims to discuss recent advances in algorithm-based HVM analysis and the physiological basis of tissue perfusion-based resuscitation parameters.

RECENT FINDINGS

Advanced computer vision algorithm such as MicroTools independently quantify microcirculatory diffusion and convection capacity by HVM and provide direct insight into tissue perfusion, leading to our formulation a functional parameter, tissue red blood cell (RBC) perfusion (tRBCp). Its definition is discussed in terms of the physiology of oxygen transport to the tissue and its expected effect as a point-of-care resuscitation target. Further refinements to microcirculatory monitoring include multiwavelength HVM techniques and maximal recruitable microcirculatory diffusion and convection capacity.

SUMMARY

tRBCp as measured using algorithm-based HVM analysis with an automated software called MicroTools, represents a promising candidate to assess microcirculatory delivery of oxygen for microcirculation-based resuscitation in critically ill patients at the point-of-care.

Monitoring coherence between the macro and microcirculation in septic shock

PURPOSE OF REVIEW

Currently, the treatment of patients with shock is focused on the clinical symptoms of shock. In the early phase, this is usually limited to heart rate, blood pressure, lactate levels and urine output. However, as the ultimate goal of resuscitation is the improvement in microcirculatory perfusion the question is whether these currently used signs of shock and the improvement in these signs actually correspond to the changes in the microcirculation.

RECENT FINDINGS

Recent studies have shown that during the development of shock the deterioration in the macrocirculatory parameters are followed by the deterioration of microcirculatory perfusion. However, in many cases the restoration of adequate macrocirculatory parameters is frequently not associated with improvement in microcirculatory perfusion. This relates not only to the cause of shock, where there are some differences between different forms of shock, but also to the type of treatment.

SUMMARY

The improvement in macrohemodynamics during the resuscitation is not consistently followed by subsequent changes in the microcirculation. This may result in both over-resuscitation and under-resuscitation leading to increased morbidity and mortality. In this article the principles of coherence and the monitoring of the microcirculation are reviewed.

Crocin ameliorates oxidative stress and suppresses renal damage in streptozotocin induced diabetic male rats

Diabetes mellitus (DM) is a prevalent metabolic disorder with complications including nephropathy, neuropathy, retinopathy and peripheral vascular disease. Crocin is a water soluble carotenoid that exhibits strong antioxidant activity. I investigated the potential hypoglycemic and reno-protective effects of crocin for type 1 diabetic male rats using periodic acid-Schiff and hematoxylin staining; metalloproteinase-7 (MMP-7), phosphatase and tensin homolog (PTEN) and phospho-Akt (p-Akt) immunohistochemistry; measurement of blood glucose, malondialdehyde (MDA), superoxide dismutase (SOD), total antioxidant and total oxidant status; and oxidative stress index. I used four groups of rats: control (saline treated), diabetic (single dose of 65 mg/kg streptozotocin), crocin (treated with 50 mg/kg) and diabetic + crocin. Crocin decreased levels of MDA, SOD, oxidative stress index and glucose significantly in diabetic animals. Renal damage from DM also was decreased by crocin treatment. MMP-7 and p-Akt immunoreactivity were stronger in the diabetic group compared to other groups, but PTEN immunoreactivity was weaker. Crocin treatment returned MMP-7 and PTEN expression to near normal. The ameliorative effect of crocin is attributed to its stimulation of the antioxidant defense system and its ability to regulate the MMP-7/PTEN/Akt signaling cascade.

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.