Rat Model Of Hemorrhagic Shock Research Articles

Effects of arterial oxygen content on oxidative stress during resuscitation in a rat hemorrhagic shock model

ObjectiveTo examine whether reactive oxygen species (ROS) production is affected by arterial oxygen content (CaO2) in attempted resuscitation to restore blood pressure from hemorrhagic shock (HS) or not. MethodsUnder light anesthesia and spontaneous beating, 16 rats underwent HS for 80min, during which 3.0mL/100g of blood was withdrawn, followed by resuscitation attempt for 70min. At 80min, rats were randomized into a high-CaO2 group (Group 1, transfusion under fractional inspired oxygen (FIO2) of 1.0, n=8) or a low-CaO2 group (Group 2, fluid administration under FIO2 of 0.21, n=8). In each group, either blood or lactate Ringer's (LR) solution was infused to maintain mean arterial pressure ≥75mmHg under each FIO2 concentration. CaO2, O2 utilization coefficient (UC) and plasma %CoQ9 were compared between groups. ResultsMean infused volume for attempted resuscitation was 7.6±1.0mL of blood in Group 1, and 31.4±5.5mL of LR solution in Group 2. At the end of resuscitation, CaO2 was 18.5±1.2 vol% in Group 1, almost double the 9.1±0.8 vol% in Group 2 (P<0.01). O2 UC and %CoQ9 in all rats increased from baselines of 0.25±0.12 and 7.6±1.8% to 0.44±0.13 and 9.7±1.8% after resuscitation, respectively (P<0.05 vs. baseline for each), but did not differ significantly between the groups. ConclusionIn a rat HS model, attempted resuscitation to restore blood pressure increased O2 UC as well as %CoQ9. However, the magnitude of %CoQ9 increase that represents ROS production is not affected by CaO2 during resuscitation from HS.

The influence of hypotensive resuscitation strategy on gut and lung injury in a rat model of uncontrolled hemorrhagic shock

Objective To investigate the effect of hypotensive resuscitation strategies on the hemorrhagic shock-induced gut and lung injury in an uncontrolled hemorrhagic-shock rat model. Methods Uncontrolled hemorrhagic-shock Sprague-Dawley male rats (n = 16;8 rats per group) were randomly assigned to normotensive resuscitation group ( group Ⅰ ) and hypotensive resuscitation group ( group Ⅱ ). 3h after resuscitation,gut injury and lung injury was assessed. Results The percentage of villous injury in group Ⅰwas ( 33. 13 ± 2. 17 ) %, while it was ( 12. 38 ± 1.69 ) % ( P ＜ 0. 05 ). The incidence of bacterial translocation in both groups was 87.5% (7/8) and 25.0% ( 2/8 ) respectively ( P ＜ 0.05 ). The percentage of Evan' s blue leakage was ( 3.03 ± 0. 28 ) % in group Ⅰ , whereas it was ( 1.25 ± 0. 17 ) % in group Ⅱ ( P ＜0. 05). The lung permeability index in both groups was 0. 140 ± 0. 018 and 0. 085 ± 0. 004 respectively (P＜0.05). Myeloperoxidase (MPO) activity in group Ⅰ was significantly higher than in group Ⅱ,(16.4±2.6) u/gvs(33.8±2.1) u/g(P＜0.05). Conclusion In severe and uncontrolled hemorrhagic shock, hypotensive resuscitation before definitive hemorrhage control is achieved is superior to normotensive resuscitation as it decreases both gut and lung injuries. Key words: Uncontrolled hemorrhagic shock; Resuscitation; Gut injury; Lung injury

Emulsified Isoflurane Preconditioning Protects Against Liver and Lung Injury in Rat Model of Hemorrhagic Shock

Isoflurane has demonstrated protective effects against ischemia/reperfusion injury in some organs. In this study, using the hemorrhagic shock model, we investigated whether emulsified isoflurane preconditioning protected against liver and lung injury caused by massive surgical blood loss. Male Sprague-Dawley (SD) rats were randomly divided into five groups: a control group, a hemorrhagic shock (HS) group, an intralipid (IL) group, an isoflurane (Iso) group, and an emulsified isoflurane (E-Iso) group. Saline, intralipid, isoflurane, or emulsified isoflurane were administered over 15 min. Forty-five min after injection, hemorrhage was initiated in the experimental group. Four h after resuscitation alanine aminotransferase (ALT), protein and white blood cell (WBC) in bronchoalveolar lavage fluid (BAL), and the liver and lung histopathology were measured. The malondialdehyde (MDA) and superoxide dismutase (SOD) in the liver and lung mitochondria were tested. The survival was also observed in hemorrhagic shocked rats. Emulsified isoflurane enhanced survival and decreased ALT, protein and WBC in BAL, liver and lung apoptosis, and the histologic score. It also decreased MDA and increased SOD activity in mitochondria. In the IL group, liver mitochondrial SOD activity increased, while ALT, liver apoptosis and histological score decreased. In the Iso group liver and lung mitochondrial SOD activity increased, while liver and lung apoptosis decreased. Emulsified isoflurane preconditioning has a protective effect against liver and lung injury as well as improving the survival in hemorrhagic shock. The potential mechanisms involved are the inhibition of cell death and improvement of antioxidation in mitochondria.

Protective Effects of Fresh Frozen Plasma on Vascular Endothelial Permeability, Coagulation, and Resuscitation After Hemorrhagic Shock Are Time Dependent and Diminish Between Days 0 and 5 After Thaw

Clinical studies have shown that resuscitation with fresh frozen plasma (FFP) is associated with improved outcome after severe hemorrhagic shock (HS). We hypothesized that in addition to its effects on hemostasis, FFP has protective and stabilizing effects on the endothelium that translate into diminished endothelial cell (EC) permeability and improved resuscitation in vivo after HS. We further hypothesized that the beneficial effects of FFP would diminish over 5 days of routine storage at 4 degrees C. EC permeability was induced by hypoxia and assessed by the passage of 70-kDa Dextran between monolayers. Thrombin generation time and coagulation factor levels or activity were assessed in FFP. An in vivo rat model of HS and resuscitation was used to determine the effects of FFP on hemodynamic stability. Thawed FFP inhibits EC permeability in vitro by 10.2-fold. Protective effects diminish (to 2.5-fold) by day 5. Thrombin generation time is increased in plasma that has been stored between days 0 and 5. In vivo data show that day 0 FFP is superior to day 5 FFP in maintaining mean arterial pressure in rats undergoing HS with resuscitation. Both in vitro and in vivo studies show that FFP has beneficial effects on endothelial permeability, vascular stability, and resuscitation in rats after HS. The benefits are independent of hemostasis and diminish between days 0 and 5 of storage.

The Effect of Erythropoietin on Microcirculation Perfusion and Tissue Bioenergetics of the Small Intestine in a Hemorrhagic Shock and Resuscitation Rat Model

Erythropoietin (EPO) can exert acute hemodynamic and anti-inflammatory effects in addition to erythropoiesis. We tested the hypothesis that EPO given at resuscitation with saline will improve capillary perfusion and tissue oxygenation in the gut using a hemorrhagic shock model. Sprague-Dawley rats were bled 30 mL/kg to maintain a mean arterial blood pressure of 40 mm Hg for 50 minutes and then randomized to one of four resuscitation groups (n = 6 per group): blood, blood + recombinant human EPO (rHuEPO), saline, and saline + rHuEPO. Intravenous rHuEPO (1,000 U/kg) was given at the start of resuscitation. Intravital microscopy was used to measure perfused capillary density, flow motion of red blood cell (RBC), and tissue NADH fluorescence 60 minutes after resuscitation. Venous oxygenation saturation (Svo2) was also measured in a second experiment. In the blood +/- rHuEPO resuscitation group, the perfused capillary density, RBC flow motion scores, and NADH fluorescence returned to near normal values. The saline + rHuEPO group compared with the saline group demonstrated an increased RBC flow motion score (2.32 vs. 1.60; p < 0.01); however, the perfused capillary density was not significantly increased (23.03 Cap/mm vs. 21.61 Cap/mm; p = 0.40). The saline + rHuEPO group also demonstrated statistically significant lower NADH fluorescence than the saline group after shock following resuscitation (110% +/- 3.64% vs. 122% +/- 4.26%; p < 0.05) suggesting decreased tissue dysoxia. The Svo2 in the saline + rHuEPO group was higher when compared with the saline group (45% vs. 38% by continuous oximetry; 38% vs. 29% by co-oximetry; p < 0.05). Our results suggest that the addition of rHuEPO at the time of saline resuscitation may have beneficial effects in hemorrhagic shock by improving tissue perfusion and decreasing dysoxia in the gut.

The protective effects of intra-peritoneal fluid resuscitation on small intestinal mucosa in rats with hemorrhagic shock

Objective To investigate the protective effects of intra-peritoneal fluid resuscitation on small intestinal mucosa in rats with hemorrhagic shock. Method Fifty Sprague-Dawley (SD) rats were randomly (random number) divided into five groups, namely sham operation group (group I ), hemorrhagic shock group (group Ⅱ ), intra-venous fluid resuscitation group (group Ⅲ ) . intravenous fluid resuscitation plus intra-peritoneal saline resuscitation (group Ⅳ ) and intravenous fluid resuscitation plus intra-peritoneal PD-2 solution resuscitation group (group Ⅴ ). The rats of 5 groups were processed with cannulations of right common carotid artery, right femoral vein and left femoral artery with systemic heparinization. The rat models of hemorrhagic shock were established with modified Wigger' s method by which the blood exsanguinated from left femoral artery. The rats of group Ⅲ were resuscitated with shed blood plus twice equal volume of Ringer's solution after modeling of hemorrhagic shock.The rats of group Ⅳ and group Ⅴ were administered intra-peritoneally with 30 mL saline and 30 mL of 2.5% PD-2 solution, respectively as adjuncts to those used in the group Ⅲ . The specimens of blood and small intestine of rats of all groups were collected 60-120 minutes after modeling and resuscitation. The activity of plasma diamine oxidase (DAO) was determined with chromatometry, the level of plasma D-lactic acid (D-LA) with spectorophotometry and the level of plasma lipopolysaccharide (LPS) with nephelometry. The histopathological and ultrastructure changes of small intestine tissue of rats were observed under light microscope and electronic microscope. Results There were remarkable differences in activity of DAO, and the levels of D-LA and IPS in rats between those ingroup Ⅱ and group I (P <0.01), and between those in group V and groups Ⅱ , Ⅲ or Ⅳ (P <0.05 or P < 0.01) The pathomorphology and ultra-structure of small intestine tissues were severely damaged in group Ⅱ compared with those in group Ⅰ , and those markedly lessened in group V compared with groups Ⅱ , Ⅲ and Ⅳ . Conclusions Intraperitoneal fluid resuscitation with PD-2 solution can significantly protect the integrity of intestinal mucosa and the normal permeability of intestinal wall, and blunts the histopathological changes, and restrains bacterial translocation from gut and reduces the level of plasma endotoxin. Key words: Hemorrhagic shock; intestinal mucosa intraperitoneal resuscitation; bacterial translocation; multiple organ dysfunction syndrome; diamine oxidase; D-lactic acid; Lipopolysaccharide

STRATEGIES OF EXPERIMENT STANDARDIZATION AND RESPONSE OPTIMIZATION IN A RAT MODEL OF HEMORRHAGIC SHOCK AND CHRONIC HYPERTENSION

Exploratory pilot studies are crucial to best practice in research but are frequently conducted without a systematic method for maximizing the amount and quality of information obtained. We describe the use of response surface regression models and simultaneous optimization methods to develop a rat model of hemorrhagic shock in the context of chronic hypertension, a clinically relevant comorbidity. Response surface regression model was applied to determine optimal levels of two inputs--dietary NaCl concentration (0.49%, 4%, and 8%) and time on the diet (4, 6, 8 weeks)--to achieve clinically realistic and stable target measures of systolic blood pressure while simultaneously maximizing critical oxygen delivery (a measure of vulnerability to hemorrhagic shock) and body mass M. Simultaneous optimization of the three response variables was performed though a dimensionality reduction strategy involving calculation of a single aggregate measure, the "desirability" function. Optimal conditions for inducing systolic blood pressure of 208 mmHg, critical oxygen delivery of 4.03 mL/min, and M of 290 g were determined to be 4% [NaCl] for 5 weeks. Rats on the 8% diet did not survive past 7 weeks. Response surface regression model and simultaneous optimization method techniques are commonly used in process engineering but have found little application to date in animal pilot studies. These methods will ensure both the scientific and ethical integrity of experimental trials involving animals and provide powerful tools for the development of novel models of clinically interacting comorbidities with shock.

Effects of volume therapy with different doses of 6% hydroxyethyl starch 130/0.4 on lung injury in a rat model of hemorrhagic shock

Objective To evaluate the effects of volume therapy with different doses of 6% hydroxyethyl starch 130/0.4 (6% HES 130/0.4) on lung injury in a rat model of hemonhagic shock.Methods Twenty-four male SD rats weighing 220-300 g were randomly divided into 4 groups ( n = 6 each) : group I sham operation (group S); group II Ringer's solution (group RS); group HI and IV 2 HES groups (group H1, H2 ). The animals were anesthetized with intraperitoneal 1% sodium pentobarbital 45 ing/kg. Right common carotid artery (CCA) and left femoral vein were cannulated for blood letting, MAP monitoring, fluid administration and blood sampling. Hemonhagic shock was induced by withdrawing blood from right CCA in group II , III and IV . MAP was reduced to 35-45 mmHg which was maintained for 90 min. In group RS, hemorrhagic shock was resuscitated with Ringer's solution 3 times of the volume of blood withdrawn, while group H1 and H2 received HES 33 and 50 ml/kg respectively and Ringer' s solution (the total volume was equal to 3 times of the volume of blood removed) . Arterial blood samples were taken before blood letting (T0 , baseline), and at 2, 3 h after volume therapy (T1,2) for blood gas analysis and PaO2/FiO2 was calculated. The animals were then sacrificed by exsanguination and the lungs were immediately removed for microscopic examination and determination of protein concentration in broncho-alveolar lavage fuid (BALF), W/D lung weight ratio and TNF-α, IL-1 β and IL-10 contents in the lung.Results TNF-α, IL-1β and IL-10 content in the lung, protein concentration in BALF and W/D ratio were significantly higher in group RS, H1 and H2, while PaO2/FiO2 was significantly lower at T,2 in group RS and at T2 in group H2 than in group S (P < 0.05). TNF-α and IL-1β contents in the lung, protein concentration in BALF and W/D ratio were significantly lower in group H1 and H2 , while PaO2/FiO2 was significantly higher at T,i2 in group H1 and at T1 in group H2 than in group RS (P <0.05) . PaO2/FiO2 at T2 and IL-10 content in the lung were significantly lower in group H2 than in group H, ( P < 0.05) . The lung damage was significantly ameliorated in group H1 and H2 especially in group H, as compared with group RS. Conclusion Volume therapy with 6% HES 130/0.4 33 or 50 ml/kg can attenuate lung injury in a rat model of hemorrhagic shock and the efficacy of 33 ml/kg is better. Key words: Hetastarch; Shock,hemorrhagic; Respiratory distress syndrome,adult

Therapeutic Mild Hypothermia: Effects on Coagulopathy and Survival in a Rat Hemorrhagic Shock Model

: To determine the effects of therapeutic hypothermia on coagulation parameters during hemorrhagic shock (HS) and fluid resuscitation and on survival, in a rat HS model. : Under light anesthesia and spontaneous breathing, 24 rats underwent HS (phase I) for 90 minutes, during which 2.5 mL/100 g blood was withdrawn over 15 minutes; fluid resuscitation (phase II) for 60 minutes, during which no blood was reinfused but 5.0 mL/100 g lactated Ringer's solution was infused over 30 minutes; and an observation (phase III) without anesthesia until 72 hour. After the volume-controlled hemorrhage, rats were randomized into a hypothermia group (n = 12, 33 degrees C) or a normothermia group (n = 12, 38 degrees C). The rectal temperature in each group was maintained during phases I and II. Whole blood coagulopathy was assessed by Sonoclot analysis (SA) at baseline and the end of phases I and II. Fibrinolysis parameters of thrombin-antithrombin III complex and plasma-alpha-2-plasmin inhibitor complex were also monitored. : At 72 hour, 10 of 12 hypothermia group rats, and 5 of 12 normothermia group rats remained alive (p < 0.05). Fluid resuscitation significantly decreased hematocrit (20% +/- 5%) compared with baseline (33% +/- 5%; p < 0.05) in all rats. SA showed no significant differences between groups at the end of phase I. However, at the end of phase of II, SA revealed a decreased "clot rate" in hypothermia compared with normothermia (22 clot signal/min +/- 11 clot signal/min vs. 34 clot signal/min +/- 14 clot signal/min; p < 0.05) and a prolonged "time to peak" in hypothermia (15 minutes +/- 5 minutes versus 6 minutes +/- 2 minutes; p < 0.05). No differences in thrombin-antithrombin III complex and plasma-alpha-2-plasmin inhibitor complex values were seen between groups throughout the experiment. : Therapeutic mild hypothermia of 33 degrees C did not cause coagulopathy during HS, but did impair SA coagulation parameters during fluid resuscitation, probably because of dilution. Hypothermia also prolonged survival after HS. Impairments to coagulation parameters did not worsen outcomes in the rat HS model.

Effects of balanced and unbalanced colloid and crystalloid solutions on renal oxygenation in a rat model of hemorrhagic shock and resuscitation

Hydroxyethyl starch (HES, 130 kD) dissolved either in saline (Voluven®) or in a balanced Ringer's acetate solution (PlasmaVolume Redibag®, PVR) and Ringer's acetate (RA) and 0.9% NaCl (NaCl) were investigated as regards their efficacy in restoring renal oxygenation in a rat model of hemorrhagic shock and resuscitation.

Effects of Different Resuscitation Fluids on Acute Lung Injury in a Rat Model of Uncontrolled Hemorrhagic Shock and Infection

To investigate the effects of different resuscitation fluids on acute lung injury in a rat model of uncontrolled hemorrhagic shock (HS) followed by mimicked infection. Sixty Sprague-Dawley rats were randomly assigned to one of the five groups (n = 12 per group) to receive the following treatments: (1) control group (group C), surgery, no hemorrhage, and no resuscitation; (2) no fluid resuscitation group; (3) lactated Ringer's solution group; (4) 7.5% hypertonic saline (HTS) group; and (5) hydroxyethyl starch group (group HES). All experimental groups were subjected to three phases: phase I entailed massive hemorrhage with a mean arterial pressure of 35 mm Hg to 40 mm Hg for 60 minutes by tail amputation and followed by mimicked infection by intratracheal administration of lipopolysaccharide 2 mg/kg. The animals in each group were then partially resuscitated with the fluid assigned to the group. Phase II of 60 minutes commenced at tail ligation, involved hemostasis, and return of all the blood initially shed. Phase III was an observation phase with no any further treatment and lasted for 3.5 hours. The survival rate at the end of the phase III was recorded. After phase III, arterial blood gases were recorded. The wet to dry lung weight ratio, pulmonary microvascular permeability, the expression of transforming growth factor (TGF)-beta1, and Smad2 were determined. The lung histology was also assessed. HES and HTS solutions were more effective than no fluid resuscitation and lactated Ringer's solution in reducing the detrimental effects of HS and infection on the lungs, as seen by the significantly lower pulmonary microvascular permeability and wet to dry lung weight ratio, the improved arterial blood gases and lower levels of TGF-beta1and Smad2 expression in lung tissues. These beneficial effects were most pronounced in the group HES. This study demonstrated that resuscitation with HTS and especially with HES could reduce lung tissue damage and pulmonary edema after severe uncontrolled HS. The TGF-beta1/Smad2 signaling pathway might play a key role in regulation of pulmonary permeability and formation of pulmonary edema in a rat model of uncontrolled HS and infection.

Cyclosporine preserves intestinal morphology in a rat model of hemorrhagic shock

Yazdi, Cyrus Ahmadi MD; Oakes, Sean M. BS; Sheu, Eric G. MD, PhD; Afnan, Jalil MD; Moore, Francis D. Jr MD, FACS Author Information

A Transient Inflammatory Reaction in the Lung After Experimental Hemorrhagic Shock and Resuscitation With a Hemoglobin-Vesicles Solution Compared With Rat RBC Transfusion

Transfusion for hemorrhagic shock can improve oxygenation, but immunoreactions may induce inflammation. Artificial oxygen carriers have been developed to address clinical concerns of infection and stability, but whether an artificial oxygen carrier might induce inflammation is not well known. To address this question, we compared inflammatory reactions after resuscitation with hemoglobin vesicles (HbVs) or red blood cells (RBCs) in a hemorrhagic shock rat model. Both HbVs and the stored and irradiated rat RBCs deprived of buffy coat were suspended in recombinant human serum albumin [(Hb) = 8.6 g/dL]. Under anesthesia, hemorrhagic shock was induced for 30 min, followed by resuscitation by 20 min transfusion of HbVs or rat RBCs in a volume equivalent to the volume of withdrawn blood. Lungs were excised 2 or 24 h after resuscitation, and mRNA levels of tumor necrosis factor alpha (TNF-alpha), intercellular adhesion molecule-1 (ICAM-1), nitric oxide synthase 2 (iNOS), nitric oxide synthase 3, hypoxia-inducible factor 1 alpha, and heme oxygenase 1 (HO-1) were measured. In rats resuscitated with HbVs, mRNA levels of TNF-alpha and HO-1 2 h after resuscitation were significantly higher than those in the rat RBC group, but the levels at 24 h were similar in both groups. The expression of iNOS and ICAM-1, second messengers of inflammation, was not affected, and inflammatory levels after 24 h with HbVs are similar to rat RBC transfusion. The rat RBC group did not show an expected inflammatory reaction related to a transfusion-induced lung injury, and a clinical relevance concerning this level of transient inflammatory reaction induced by HbVs is not known; however, attention to the early stage of resuscitation in ongoing studies of HbV is required.

Effects of various concentrations of inhaled oxygen on tissue dysoxia, oxidative stress, and survival in a rat hemorrhagic shock model

Objective To test the hypothesis that a fractional inspired oxygen (F IO 2) of 1.0 compared to 0.4 during hemorrhagic shock (HS) and fluid resuscitation (FR): mitigates tissue dysoxia; however, enhances the oxidative stress; therefore, offsets the benefit on survival. Methods Thirty rats underwent: HS for 75 min, during which 3.0 mL/100 g of blood was withdrawn, followed by FR for 75 min, during which 1.0 mL/100 g of shed blood and 3.0 mL/100 g of crystalloid solution were infused. Ten rats were randomized into one of three F IO 2 (0.21 vs. 0.4 vs. 1.0) groups, and observed for survival until 72 h in each group. Hemodynamics, liver tissue PO 2 (P TO 2), and, plasma antioxidants levels were also monitored. Results Oxygen inhalation increased mean arterial pressure (MAP) and decreased heart rate (HR) during HS and FR. Liver P TO 2 was less than 10 Torr in all groups throughout HS; while it increased to average 26–35 Torr in oxygen groups during FR, it remained at 10 Torr with F IO 2 0.21 ( P < 0.01). MAP, HR, and P TO 2 did not differ significantly between oxygen groups. Plasma antioxidants levels did not differ among the three groups. All rats treated with oxygen, but eight of 10 rats with F IO 2 0.21 survived up to 72 h (NS). Conclusions Supplemental oxygen does not mitigate tissue dysoxia during HS, but does reduce tissue dysoxia without enhancing oxidative stress during subsequent FR. Increased F IO 2 appears to prolong survival. These beneficial effects of supplemental oxygen do not differ between an F IO 2 of 0.4 and 1.0.

The spleen is required for 5-HT1Areceptor agonist-mediated increases in mean circulatory filling pressure during hemorrhagic shock in the rat

The 5-HT(1A) receptor agonist, 8- OH-DPAT, increases whole body venous tone (mean circulatory filling pressure; MCFP), and attenuates metabolic acidosis in a rat model of unresuscitated hemorrhagic shock. To determine whether improved acid-base balance was associated with sympathetic activation and venous constriction, MCFP, sympathetic activity (SA), and blood gases were compared in hemorrhaged rats following administration of 5-HT(1A) receptor agonist 8-OH-DPAT, the arterial vasoconstrictor arginine vasopressin (AVP), or saline. To further determine whether protection of acid-base balance was dependent on splenic contraction and blood mobilization, central venous pressure (CVP), MCFP, and blood gases were determined during hemorrhage and subsequent 8-OH-DPAT-administration in rats subjected to real or sham splenectomy. Subjects were hemorrhaged to an arterial pressure of 50 mmHg for 25 min and subsequently were treated with 8-OH-DPAT (30 nmol/kg iv), AVP titrated to match the pressor effect of 8-OH-DPAT (approximately 2 ng/min iv), or infusion of normal saline. 8-OH-DPAT increased MAP, CVP, MCFP, and SA, and decreased lactate accumulation. AVP did not affect CVP or SA, but raised MCFP slightly to a level intermediate between 8-OH-DPAT- and saline-treated rats. Infusion of AVP also produced a modest protection against metabolic acidosis. Splenectomy prevented the rise in CVP, MCFP, and protection against metabolic acidosis produced by 8-OH-DPAT but had no effect on the immediate pressor response to the drug. Together, the data indicate that 8-OH-DPAT produces a pattern of cardiovascular responses consistent with a sympathetic-mediated venoconstriction that is, in part, responsible for the drug's beneficial effect on acid-base balance. Moreover, blood mobilization stimulated by the spleen is required for the beneficial effects of 8-OH-DPAT.

Protective Roles of Hydroxyethyl Starch 130/0.4 in Intestinal Inflammatory Response and Oxidative Stress After Hemorrhagic Shock and Resuscitation in Rats

This study was designed to determine the effects of various resuscitation fluids on intestinal injuries after hemorrhagic shock and resuscitation (HS/R) and to determine the potential mechanisms. We induced HS by bleeding male Sprague-Dawley rats to a blood pressure of 30 to 40 mmHg for 60 min. Sixty minutes later, the rats were killed (HS group) or immediately resuscitated with L-isomer lactated Ringer's solution (HS + LR group), shed blood (HS + BL group), or hydroxyethyl starch (HS + HES group) to maintain the blood pressure to the original value during the 60-min resuscitation period. Three hour after resuscitation, bacterial translocation (BT), intestinal permeability, ileal levels of tumor necrosis factor (TNF)-alpha, interleukin (IL)-6, malondialdehyde (MDA), oxidized and reduced glutathione (GSH and GSSG), myeloperoxidase (MPO) activity, nuclear factor (NF)-kappaB, activator protein (AP)-1 activation, and ileal microscopic and ultrastructural histological changes were measured. Another experiment was designed for survival study of 24 h. HES 130/0.4 solution was as effective as shed blood, required a small volume requirement to restore circulation, and significantly reduced HS/R-induced ileal villous morphological injuries with an anti-inflammatory effect, as reflected by a reduction of TNF-alpha, IL-6, MPO activity, and NF-kappaB activation. In addition, HES resuscitation also reduced intestinal permeability and BT and caused less oxidative stress as reflected by a reduction of MDA, GSSG/GSH and AP-1 activation along with restored GSH, whereas shed blood couldn't. No significant difference was observed in outcome among groups. HES 130/0.4 resuscitation prevents HS/R induced intestinal injury by modulating inflammatory response and preventing oxidative stress in a rat model of hemorrhagic shock. These physiological protective effects appear to be mediated by down-regulation of the transcription factor NF-kappaB and AP-1.

Pharmacokinetics of single and repeated injection of hemoglobin-vesicles in hemorrhagic shock rat model

Hemoglobin-vesicles (HbV) are liposomal artificial oxygen carriers that may be useful as a resuscitation fluid during hemorrhagic shock (HS). It is well-known that the pharmacokinetic properties of liposome change in response to both pathological conditions and repeated administration. Therefore, we compared the pharmacokinetics of single versus repeated administration of HbV during HS. HS was induced by withdrawal of 40% of total blood volume. The normal (non-HS) and HS 1 group was received an injection of 125I-labeled HbV ( 125I-HbV). The HS 2 group was resuscitated with non-labeled HbV, and 1 h later, it received an injection of 125I-HbV. The half-life was shorter in HS 1 rats, but it returned to non-HS levels after the second HbV injection. During 12 h after administration of HbV, tissue distribution of HbV was greatest in the HS 1 group; however, the HS 2 group had the greatest tissue distribution at subsequent time points. Excretion into urine, major elimination pathway, did not differ between non-HS and HS 1 rats, but was significantly reduced in the HS 2 group. Furthermore, the half-life of HbV in humans was estimated to be approximately 3–4 days using an allometric equation. This suggests that HbV may be a useful artificial oxygen carrier in HS based on HbV pharmacokinetics.

Site-specific induction of intestinal hypoxia-inducible factor-1α after hemorrhagic shock

The intestine is a major target organ in hemorrhagic shock (HS)-induced tissue injury. Hypoxia-inducible factor (HIF)-1α is the primary transcription factor responsible for regulating cellular response to changes in oxygen tension. Since HS is an acute hypoxic insult, the present study examined changes in the gene expression of HIF-1α in various regions of the intestine, as well as the distribution of HIF-1α protein in the intestinal cells of a rat model of HS. Levels of HIF-1α mRNA were marginally detectable in the intestine of sham-operated control animals, but obviously induced following HS. Duodenal, jejunal and colonic levels of HIF-1α mRNA robustly increased and reached a maximum during the ischemic phase of HS, followed by a rapid decrease almost to control levels during the early phase of resuscitation. The induction of HIF-1α mRNA was maximal in the duodenum. In contrast to the duodenum, jejunum and colon, in the ileum the HIF-1α mRNA level did not increase after HS. Consistent with enhanced HIF-1α gene expression, HIF-1α protein was expressed in the mucosal cells of the duodenum, jejunum and colon, but not in the ileum following HS. These findings indicate that intestinal HIF-1α expression was up-regulated at both the transcriptional and protein level in a site-specific manner in this rat model of HS. Differential regulation of HIF-1α expression along the longitudinal axes of the intestine might be a determinant of the adaptive response to HS-induced intestinal damage.

Mild Hypothermia Improves Survival During Hemorrhagic Shock Without Affecting Bacterial Translocation

Background: Accidental hypothermia in patients with hemorrhagic shock (HS) is associated with increased mortality. However, experimental mild and moderate hypothermia has beneficial effects. The mechanisms for beneficial effects of hypothermia have not been completely understood. Therefore, the aim of this study was to investigate the effect of hypothermia on survival, bacterial translocation (BT), and remote pulmonary injury in a controlled HS model in rats. Methods: HS was achieved by blood withdrawal through femoral vein. Rats in the normothermia group (group I) were maintained at 37°C. Mild hypothermia group (group II) was observed at 32°C that was spontaneously induced by exposure to ambient temperature. Moderate hypothermia of 28°C was actively induced by external cooling in group III for 90 min. Survival and neurological deficit scores (NDS) were recorded at 24th hr. Mesenteric lymph nodes, liver and spleen samples were collected. Myeloperoxidase (MPO) and malondialdehyde (MDA) levels were measured in lung tissue. Results: Blood pressure significantly increased in hypothermia groups. Mild hypothermia significantly increased survival. No difference was found in BT rates in groups. Hypothermia was found to significantly decrease the NDS points in group III, compared to group I. There was no difference in lung tissue MPO levels among groups. Lung tissue MDA levels increased significantly in groups II and III. Conclusions: Mild hypothermia improved blood pressure, survival, and neurological outcome with a possible detrimental effect on pulmonary ROS production during HS in rats. These effects of hypothermia are not associated with BT.

Does the Type of Resuscitative Fluid Affect Healing of Colonic Anastomosis in Experimentally Induced Hemorrhagic Shock in Rats?

Objective: The aim of the study was to investigate the effects of different resuscitative fluids on the healing of intestinal anastomosis in a hemorrhagic-shock rat model. Materials and Methods: Closed-colony Wistar male rats (n = 40; 8 rats per group) were subjected to volume-controlled hemorrhagic shock, followed by a 30-min shock phase. The animals were then resuscitated with one of the following fluids (which also corresponds to their respective groups): lactated Ringer’s solution (LR), hydroxyethyl starch (HES), 7.5% hypertonic saline (HS) and autologous blood (AB). There was also a control group (CL), which did not experience hemorrhagic shock or receive any resuscitative fluids. All rats underwent laparotomy, segmental resection and anastomosis of the left colon. Five days later, a 2nd laparotomy was performed and the anastomotic bursting pressure was measured in vivo. Thereafter, the anastomosed segment was resected to measure the tissue hydroxyproline level and the grade of anastomotic fibrosis. Results: All experimental groups (LR, HES, HS and AB) exhibited lower anastomotic bursting pressures than the CL group; however, nointergroup differences achieved statistical significance. The mean tissue hydroxyproline level and fibrosis grade also were similar across all 5 groups. Conclusion: In traumatic hemorrhagic shock, anastomosis safety does not appear to be affected by the type of fluid used for resuscitation. Moreover, LR, HES and HS all seemed to reinforce healing as effectively as transfused blood.