H12-(ADP)-liposomes for hemorrhagic shock in thrombocytopenia: Mesenteric artery injury model in rabbits.

Background: Damage control resuscitation improves patient outcomes after severe hemorrhage and coagulopathy. However, effective hemostasis methods for these critical situations are lacking.

Objective: We evaluated the hemostatic efficacy of fibrinogen γ-chain (HHLGGAKQAGDV, H12)-coated, adenosine-diphosphate (ADP)-encapsulated liposomes (H12-[ADP]-liposomes) in thrombocytopenic rabbits with hemorrhagic shock.

Cellular and Biochemical Effects of Combined X-Ray Radiation and Storage on Whole Blood.

Background: Evaluating the impact of ionizing radiation on stored blood is relevant since blood banks are major assets in emergency conditions such as radiation incident/attack. This study aimed to fill our knowledge gap of combined radiation and storage effects on blood.

Methods: Blood collected from 16 anesthetized rats was anticoagulated, aliquoted into storage bags, and assigned to 8 groups using protocols combining storage (1-day vs 3-day 4C) plus irradiation (75 Gy vs 0 Gy - control).

Role of albumin on endothelial basement membrane and hemostasis in a rat model of hemorrhagic shock.

Background: We sought to determine the extent of loss of endothelial basement membrane (BM), leukocyte recruitment, and changes in coagulation after hemorrhagic shock, followed by limited-volume resuscitation (LVR) with 5% albumin (ALB).

Methods: Anesthetized rats were bled 40% of blood volume and assigned to treatment groups: untreated (n = 6), LVR with normal saline (NS; n = 8), or LVR with ALB (n = 8). Sham rats (n = 6) underwent all procedures except hemorrhage or resuscitation.

Albumin Saturated With Fatty Acids Prevents Decompensation in a Rat Hemorrhagic Shock Trauma Model With Tourniquet and Hypotensive Resuscitation.

Decompensation is a major prehospital threat to survival from trauma/hemorrhage shock (T/HS) after controlling bleeding. We recently showed higher than expected mortality from a combat-relevant rat model of T/HS (27 mL/kg hemorrhage) with tourniquet (TQ) and permissive hypotensive resuscitation (PHR) with Plasmalyte. Mortality and fluid requirements were reduced by resuscitation with 25% albumin presaturated with oleic acid (OA-sat) compared with fatty-acid -free albumin or Plasmalyte.

Cremaster muscle perfusion, oxygenation, and heterogeneity revealed by a new automated acquisition system in a rodent model of prolonged hemorrhagic shock.

Local blood flow/oxygen partial pressure (Po) distributions and flow-Po relationships are physiologically relevant. They affect the pathophysiology and treatment of conditions like hemorrhagic shock (HS), but direct noninvasive measures of flow, Po, and their heterogeneity during prolonged HS are infrequently presented. To fill this void, we report the first quantitative evaluation of flow-Po relationships and heterogeneities in normovolemia and during several hours of HS using noninvasive, unbiased, automated acquisition.

Automated noninvasive evaluation of blood flow and oxygenation in rats integrated with systemic physiological monitoring.

Background: Many studies evaluating blood flow and oxygen partial pressure (PO2) do not directly measure both parameters, are confined to few locations/microvessels, and depend on investigator's selection of measuring sites. Moreover, clinically/physiologically relevant systemic parameters are not simultaneously recorded. We implemented an automated system for prolonged blood flow/PO2 acquisition in large areas while collecting relevant systemic information.

Fatty Acid-Saturated Albumin Reduces High Mortality and Fluid Requirements in a Rat Model of Hemorrhagic Shock Plus Tourniquet and Hypotensive Resuscitation.

Military prehospital care for hemorrhage is often characterized by use of tourniquets (TQ) and permissive hypotensive resuscitation (PHR) with crystalloids or colloids, but these treatments have not been previously combined in an animal model. Although albumin resuscitation solutions have been tested, the potential effects of nonesterified fatty acids (NEFAs) bound to albumin have not been evaluated in vivo, and few studies have investigated concentrated albumin solutions to reduce fluid requirements. We created a militarily relevant rat model of trauma and hemorrhagic shock (T/HS) (27 mL/kg hemorrhage) with TQ and PHR.

Hemorrhagic Shock and the Microvasculature.

The microvasculature plays a central role in the pathophysiology of hemorrhagic shock and is also involved in arguably all therapeutic attempts to reverse or minimize the adverse consequences of shock. Microvascular studies specific to hemorrhagic shock were reviewed and broadly grouped depending on whether data were obtained on animal or human subjects. Dedicated sections were assigned to microcirculatory changes in specific organs, and major categories of pathophysiological alterations and mechanisms such as oxygen distribution, ischemia, inflammation, glycocalyx changes, vasomotion, endothelial dysfunction, and coagulopathy as well as biomarkers and some therapeutic strategies.

Mini-review: Perfluorocarbons, Oxygen Transport, and Microcirculation in Low Flow States: in Vivo and in Vitro Studies.

The in vivo study of microvascular oxygen transport requires accurate and challenging measurements of several mass transfer parameters. Although recommended, blood flow and oxygenation are typically not measured in many studies where treatments for ischemia are tested. Therefore, the aim of this communication is to briefly review cardinal aspects of oxygen transport, and the effects of perfluorocarbon (PFC) treatment on blood flow and oxygenation based mostly on studies performed in our laboratory.

Low-volume resuscitation with normal saline is associated with microvascular endothelial dysfunction after hemorrhage in rats, compared to colloids and balanced crystalloids.

Background: Restoration of endothelial glycocalyx (EG) barrier may be an essential therapeutic target for successful resuscitation. The aim of this study was to compare in vivo the effects of resuscitation with normal saline (NS) to lactated Ringer's solution (LR), 5% albumin and fresh frozen plasma (FFP) on their ability to maintain EG and barrier function integrity, mitigate endothelial injury and inflammation, and restore vascular homeostasis after hemorrhagic shock.

Methods: Anesthetized rats (N = 36) were subjected to hemorrhagic shock (bled 40% of total blood volume), followed by resuscitation with 45 ml/kg NS or LR, or 15 ml/kg 5% albumin or FFP.

Novel Adjunct Drugs Reverse Endothelial Glycocalyx Damage After Hemorrhagic Shock in Rats.

Introduction: There is interest in the small-volume therapeutic use of adjunct drugs for treating hemorrhagic shock (HS). However, critical information is only partially available on mechanisms of action of promising compounds such as adenosine-lidocaine-magnesium (ALM), beta-hydroxybutyrate plus melatonin (BHB/M), and poloxamer 188 (P-188). Therefore, we tested the hypothesis that these adjuncts would reverse HS-induced damage to microvascular endothelial glycocalyx and hemodynamics.

Fatty Acid Saturation of Albumin Used in Resuscitation Fluids Modulates Cell Damage in Shock: in vitro Results Using a Novel Technique to Measure Fatty Acid Binding Capacity.

The use of albumin for resuscitation has not proven as beneficial in human trials as expected from numerous animal studies. One explanation could be the practice of adding fatty acid (FA) during manufacture of pharmaceutical albumin. During ischemia, unbound free FAs (FFA) in the circulation could potentially induce cellular damage.

Plasma syndecan-1 and heparan sulfate correlate with microvascular glycocalyx degradation in hemorrhaged rats after different resuscitation fluids.

The endothelial glycocalyx plays an essential role in many physiological functions and is damaged after hemorrhage. Fluid resuscitation may further change the glycocalyx after an initial hemorrhage-induced degradation. Plasma levels of syndecan-1 and heparan sulfate have been used as indirect markers for glycocalyx degradation, but the extent to which these measures are representative of the events in the microcirculation is unknown.

Oxygen saturation monitoring using resonance Raman spectroscopy.

Background: The knowledge of hemoglobin oxygen saturation (SO2) and tissue oxygenation is critical to identify the presence of shock and therapeutic options. The resonance vibrational enhancement of hemoglobin allows measurement of oxy- and deoxy species of hemoglobin and resonance Raman spectroscopy (RRS-StO2) has been successfully used to measure aggregate microvascular oxygenation. We tested the hypothesis that noninvasive oxygen saturation measured by RRS-StO2 could serve as surrogate of systemic central venous SO2.

Systemic and microvascular effects of resuscitation with blood products after severe hemorrhage in rats.

Background: Severe hemorrhage is associated with the disruption of the endothelial glycocalyx (EG), a key component of the endothelium. The effects of blood components on the EG are unknown. The present study furthers our investigations into the effects of resuscitation with blood products on the skeletal muscle microcirculation of hemorrhaged rats, focusing on packed red blood cells (PRBCs) or fresh whole blood (FWB).

Tissue oxygenation monitoring using resonance Raman spectroscopy during hemorrhage.

Background: The ability to monitor the patient of hemorrhage noninvasively remains a challenge. We examined the ability of resonance Raman spectroscopy to monitor tissue hemoglobin oxygenation (RRS-StO2) during hemorrhage and compared its performance with conventional invasive mixed venous (SmvO2) and central venous (ScvO2) hemoglobin oxygen saturation as well as with near-infrared spectroscopy tissue hemoglobin oxygenation (NIRS-StO2).

Methods: Five male swine were anesthetized and instrumented followed by hemorrhage at a rate of 30 mL/min for 60 minutes.

Effects of perfluorocarbon emulsions on microvascular blood flow and oxygen transport in a model of severe arterial gas embolism.

Background: Arterial gas embolism (AGE) is a clinical problem that occurs directly in cardiopulmonary bypass machines in open-heart surgeries, or indirectly (through cardiac or pulmonary right to left shunts) in dive accidents, resulting in serious morbidity and even death. Perfluorocarbon (PFC) emulsions have been used for the treatment of AGE in an animal model. We hypothesized that PFC emulsions enhance microvascular blood flow, speed bubble resolution, and oxygenation in AGE compared with saline in a model of cremaster muscle from anesthetized rats.

Evaluation of resuscitation fluids on endothelial glycocalyx, venular blood flow, and coagulation function after hemorrhagic shock in rats.

Background: Endothelial glycocalyx (EG) plays an essential role in endothelium integrity and may be compromised by hemorrhagic shock. The effects of currently available resuscitation fluids such as Hextend (HEX) or lactated Ringer's solution (LR) on vascular function and coagulation are not well understood. The aim of the present study was to compare the effects of fresh frozen plasma (FFP) with HEX or LR in their ability to repair EG structure, promote volume expansion, increase blood flow, and prevent coagulopathy.

Perfluorocarbon emulsion improves oxygen transport of normal and sickle cell human blood in vitro.

Perfluorocarbons (PFC) are compounds with high gas solubility that could help deliver O2 to tissues and have been suggested as adjunct therapy to ischemia. Using a newly designed in vitro system, we tested the hypothesis that a third generation PFC emulsion (Oxycyte) increased O2 transport of blood by measuring changes in O2 extraction ratio. The system included a computer-controlled pump and blood-gas exchange chambers to oxygenate and deoxygenate the blood from nine sickle cell disease (SCD) patients and five healthy donors.

In vivo evaluation of venular glycocalyx during hemorrhagic shock in rats using intravital microscopy.

Hemorrhage is responsible for a large percentage of trauma-related deaths but the mechanisms underlying tissue ischemia are complex and not well understood. Despite the evidence linking glycocalyx degradation and hemorrhagic shock, there is no direct data obtained in vivo showing glycocalyx thickness reduction in skeletal muscle venules after hemorrhage. We hypothesize that damage to the endothelial glycocalyx is a key element in hemorrhage pathophysiology and tested the hypothesis that hemorrhage causes glycocalyx degradation in cremaster muscle microvessels.

In vivo microvascular mosaics show air embolism reduction after perfluorocarbon emulsion treatment.

Massive arteriolar gas embolism (AGE) has never been evaluated in vivo using intravital microscopy and previous perfluorocarbon (PFC) emulsions were only effective in AGE when administered before AGE. We implemented a new system for quantitative studies of massive AGE using brightfield microscopy and tested a treatment with a third-generation PFC emulsion after massive AGE. We studied bubble dynamics in cremaster muscles from anesthetized rats after AGE was induced by direct air injection into the femoral artery ipsilateral to the studied muscle.

Tissue oxygenation and microvascular hemodynamics in experimental arterial gas embolism.

Microvascular hemodynamic responses to arterial gas embolism (AGE) and local oxygen tensions (PO2) have never been evaluated in vivo using intravital microscopy. A system was implemented to study AGE in real time using brightfield and phosphorescence microscopy as well as laser-induced microvessel occlusion. Bubble dynamics, microhemodynamics and oxygenation were studied following AGE in 61 microvessels and 41 interstitial spaces from 19 anesthetized rats.

Oxygen transport characterization of a human model of progressive hemorrhage.

Background: Hemorrhage continues to be a leading cause of death from trauma sustained both in combat and in the civilian setting. New models of hemorrhage may add value in both improving our understanding of the physiologic responses to severe bleeding and as platforms to develop and test new monitoring and therapeutic techniques. We examined changes in oxygen transport produced by central volume redistribution in humans using lower body negative pressure (LBNP) as a potential mimetic of hemorrhage.

Early physiologic responses to hemorrhagic hypotension.

The identification of early indicators of hemorrhagic hypotension (HH) severity may support early therapeutic approaches and bring insights into possible mechanistic implications. However, few systematic investigations of physiologic variables during early stages of hemorrhage are available. We hypothesized that, in certain subjects, early physiologic responses to blood loss are associated with the ability to survive hemorrhage levels that are lethal to subjects that do not present the same responses.

Measurement of hemoglobin oxygen saturation using Raman microspectroscopy and 532-nm excitation.

The resonant Raman enhancement of hemoglobin (Hb) in the Q band region allows simultaneous identification of oxy- and deoxy-Hb. The heme vibrational bands are well known at 532 nm, but the technique has never been used to determine microvascular Hb oxygen saturation (So(2)) in vivo. We implemented a system for in vivo noninvasive measurements of So(2).