Experimental Model Of Hemorrhagic Shock Research Articles

Effects of Different Crystalloid Fluids on Renal Tissue in an Experimental Model of Hemorrhagic Shock.

The type of fluid that should be used in uncontrollable hemorrhages remains an area of research. This study was designed to compare the effects of resuscitation with Ringer's lactate (RL) solution versus a normal saline (NS) solution on hemodynamics, renal tissue histopathology, coagulation, and apoptosis in a rat model of hemorrhagic shock. The study employed groups designated as the control, hemorrhage, NS, and RL groups. Heart rate, mean arterial pressure, and respiratory rate were monitored. Annexin A5 values were assayed, rotational thromboelastometry analysis was performed, and excised kidney tissue samples were histopathologically analyzed. Blood pressure levels were found to be significantly higher in the control group than those measured in the other groups. While the clotting time (CT) and clot formation time (CFT) in the hemorrhage group were significantly longer than those in the control and RL groups, the CT and CFT measured in the control group were significantly shorter compared to the RL group. The mean Annexin A5 level was in the hemorrhage group, which was significantly higher compared to the other groups. In the renal histopathological evaluation, the scores of proximal tubular injury, distal renal tubular injury, and interstitial renal tubular injury were found to be significantly lower in the control group compared to the other groups. This study demonstrated that NS or RL can be used safely to improve the hemodynamic symptoms resulting from hemorrhagic shock as a means to reduce apoptosis, and to decrease findings in favor of coagulopathy in bedside coagulation tests during the early stages of hemorrhagic shock until the time of starting a blood transfusion.

Can a Therapeutic Strategy for Hypotension Improve Cerebral Perfusion and Oxygenation in an Experimental Model of Hemorrhagic Shock and Severe Traumatic Brain Injury?

Restoration of brain tissue perfusion is a determining factor in the neurological evolution of patients with traumatic brain injury (TBI) and hemorrhagic shock (HS). In a porcine model of HS without neurological damage, it was observed that the use of fluids or vasoactive drugs was effective in restoring brain perfusion; however, only terlipressin promoted restoration of cerebral oxygenation and lower expression of edema and apoptosis markers. It is unclear whether the use of vasopressor drugs is effective and beneficial during situations of TBI. The objective of this study is to compare the effects of resuscitation with saline solution and terlipressin on cerebral perfusion and oxygenation in a model of TBI and HS. Thirty-two pigs weighing 20-30kg were randomly allocated into four groups: control (no treatment), saline (60ml/kg of 0.9% NaCl), terlipressin (2mg of terlipressin), and saline plus terlipressin (20ml/kg of 0.9% NaCl + 2mg of terlipressin). Brain injury was induced by lateral fluid percussion, and HS was induced through pressure-controlled bleeding, aiming at a mean arterial pressure (MAP) of 40mmHg. After 30min of circulatory shock, resuscitation strategies were initiated according to the group. The systemic and cerebral hemodynamic and oxygenation parameters, lactate levels, and hemoglobin levels were evaluated. The data were subjected to analysis of variance for repeated measures. The significance level established for statistical analysis was p < 0.05. The terlipressin and saline plus terlipressin groups showed an increase in MAP that lasted until the end of the experiment (p < 0.05). There was a notable increase in intracranial pressure in all groups after starting treatment for shock. Cerebral perfusion pressure and cerebral oximetry showed no improvement after hemodynamic recovery in any group. The groups that received saline at resuscitation had the lowest hemoglobin concentrations after treatment. The treatment of hypotension in HS with saline and/or terlipressin cannot restore cerebral perfusion or oxygenation in experimental models of HS and severe TBI. Elevated MAP raises intracranial pressure owing to brain autoregulation dysfunction caused by TBI.

Bretschneider Solution and Two Antianginal Drugs Protect Peripheral Tissue in an Animal Model of Hemorrhagic Shock.

Shock and subsequent resuscitation provoke ischemia-reperfusion injury. Trimetazidine (TMZ), allopurinol (ALO), and histidine-tryptophan-ketoglutarate (HTK) solution, can protect from ischemia-reperfusion injury in chronic coronary syndromes and in transplantation. The objective of the current study is to compare, in a hemorrhagic shock and standard resuscitation animal model, organ damage parameters between placebo and treatment with TMZ, ALO, or HTK. Shock was induced in Wistar rats by controlled arterial bleeding, maintaining mean arterial pressure between 38 and 42 mm Hg for 60 minutes; then, drawn blood was reinfused. Animals were divided into: Sham (n = 4), Control (n = 6), TMZ (n = 7), ALO (n = 9), and HTK (n = 7). At the end of the experiment, animals were sacrificed and tissue harvested. TMZ, ALO and HTK decreased histopathologic damage in heart [Control: 1.72 (1.7-1.77); TMZ: 1.75 (1.72-1.79); ALO: 1.75 (1.74-1.8); HTK: 1.82 (1.78-1.85); all P < 0.05], kidney [Control: 3 (2-3); TMZ: 1 (1-2); ALO: 1 (1-1); HTK: 1(1-1); all P < 0.05] and intestine [Control: 3 (2-3); TMZ: 1 (1-2); ALO: 1 (1-1); HTK: 1 (0-2); all P < 0.05]. Also, treatment with TMZ, ALO, and HTK increased immunohistochemical expression of thioredoxin-1 in heart [Control: 6.6 (5.6-7.4); TMZ: 9.5 (8.1-9.7); ALO: 9.1 (8.4-10.2); HTK: 14.2 (12.6-15); all P < 0.05]; and kidney [Control: 4.6 (4-5.1); TMZ: 9.7 (9.3-9.9); ALO: 9.6 (9-9.9); HTK: 16.7 (16.1-17); all P < 0.05]. In an experimental model of hemorrhagic shock, TMZ, ALO, and HTK solution attenuated cell damage in multiple parenchyma and increased antioxidant defenses.

Experimental Lung Donor Models for Transplant

<h3>Purpose</h3> The main types of accepted donations may be divided into: Donation after Brain Death and Donation after Circulatory Death. In addition to that, some important events are frequently associated to these two types of donors, such as Hemorrhagic Shock (HS) and Cold Ischemia (CI). These events also guide the standardization of the various experimental models developed by research groups for the employment of specific treatments: brain death (BD), circulatory death (CD), HS and CI. In this study, we aimed to describe and compare the lung mechanics and inflammatory process related to these four experimental models of lung donors. <h3>Methods</h3> Forty Sprague-Dawley rats were divided into 4 groups: BD (intracranial Fogarty balloon inflation), HS (hypovolemic protocol - 40 mmHg), CD (circulatory death + 3 h warm ischemia) and CI (6 h cold ischemia). Inflammatory responses and edema were assessed. In addition to these, as the BD and HS rats were kept hemodynamically stable for six hours, monitoring of lung mechanics was possible. <h3>Results</h3> Six hours after the induction of the HS, increase in elastance and resistance were observed (fig. 1). In lung tissue, BD and HS presented high levels of IL-1β and IL-6 in comparison to the CD and CI groups. In contrast, IL-10 levels were higher in the HS group, being significantly different when compared to the CD group. Finally, the BD group had the highest lung wet-to-dry ratio (fig. 2). <h3>Conclusion</h3> The experimental model of HS cause dysfunction of the lung mechanics. BD and HS lead to increased levels of cytokines and lung edema. These differences should be carefully considered to choose the ideal experimental model for developing specific therapeutic strategies.

Abstract 120: Effects of Therapeutic Hypothermia on Blood Parameters in Rats With Acute Hemorrhagic Shock

Background: Our research group recently observed that therapeutic hypothermia (TH) compared with normothermia improved long-term survival in an experimental model of hemorrhagic shock. The effect of TH on blood counts, blood gases and chemistries during the early phase of recovery from hemorrhagic shock are unknown. Therefore, the purpose of the present study was to examine the effects of TH on blood parameters in the early phase of resuscitation from hemorrhagic shock. Methods and results: Sprague Dawley rats (both genders) were randomly assigned to TH (n= 16) or normothermia group (n= 15). Rats were anesthetized with intraperitoneal ketamine and xylazine. After heparinizing, hemorrhagic shock was induced by withdrawing blood to a fixed mean blood pressure (MBP) of 30 mmHg for 30 minutes and then shed blood was reinfused. TH was started 5 minutes after MBP reached 30 mmHg. Core temperature was maintained at ~ 32 °C until blood volume was fully restored, after which the rats were allowed to warm back to normal temperature. In the normothermia group, body temperature was maintained at ~ 37°C. Arterial blood samples were collected 1 hour after resuscitation with shed blood. We found that pO2 (partial pressure of oxygen) was significantly higher in TH group versus the normothermic group. The rats in normothermic group had significantly elevated potassium, chloride and lactate levels and more negative base excess compared to rats that in TH group (Table). The neutrophil was lower in the TH group; the lymphocyte (%) was higher in the TH group. There were no significantly differences in pH, pCO2, sodium, calcium or glucose between the normothermia and TH groups. Conclusions: pO2 remained normal and levels of potassium, chloride, lactate and neutrophil were lower in TH group. These results may contribute to the protective effect of TH during hemorrhagic shock.

A New Echocardiographic Tool for Cardiac Output Evaluation: An Experimental Study.

The correlation between cardiac output (CO) evaluated by echocardiography and CO measured by thermodilution (COth) varies according to different studies. A new transthoracic echocardiography (TTE) tool allows automatic calculation of the subaortic velocity time index (VTIauto) and CO (COauto). The main objective was to evaluate the correlation between COth and COauto in an anesthetized, ventilated piglet hemorrhagic shock (HS) model. The secondary objectives were to evaluate the correlation between COth and CO evaluated by manual measurements of VTI, and the preload-dependency of VTIvaresp. Eighteen piglets were bled until mean arterial pressure reached 40 mm Hg. Controlled hemorrhage was maintained for 30 min before a resuscitation phase. CO was measured by Pulse index Contour Cardiac Output thermodilution methods. At each time of the experiment, three VTI values were measured (min, med, max) and the average value was calculated. COs were calculated by TTE (COmax, COmed, COmin, COave). For the 204 measures attempted, the success rate was 197 (97%) manually and 122 (60%) automatically (P < 0.01). The correlation coefficients (r) between COth and, respectively, COauto, COave, COmax, COmed, and COmin were: 0.83 (95% CI [0.76; 0.88]; P < 0.01), 0.54 (95% CI [0.43; 0.63]; P < 0.01), 0.43 (95% CI [0.31; 0.54]; P < 0.01), 0.58 (95% CI [0.48; 0.67]; P < 0.01), and 0.52 (95% CI [0.41; 0.62]; P < 0.01). In an experimental model of HS, a new ultrasound tool, COauto, seems better correlated with COth than manual echocardiographic measurements.

Abstract 187: Effects of Anesthetic Agents on the Hemodynamic Stabilization and Long Term Survival in an Experimental Model of Hemorrhagic Shock

Background: We investigated the cardiovascular responses to acute bleeding and shed blood restoration under different anesthetic agents, and their effects on long-term survival rate after hemorrhagic shock in rats, after our initial pilot study suggested differences between anesthetics. Methods: Sprague Dawley rats (both genders) were randomized to receive either intraperitoneal ketamine/xylazine (K/X, 90 mg/kg and 10 mg/kg; n=12), or isoflurane (5% isoflurane induction and 2% maintenance in room air; n=12) for anesthesia. Blood was withdrawn from the carotid artery to maintain mean arterial blood pressure (MBP) at 30 mm Hg for one hour, followed by 30 min of resuscitation with shed blood. Rats remained anesthetized for another 30 min before they were allowed to recovery and survive for 6 weeks. Hemodynamics were monitored during the surgical procedure. Results: During the shock phase, the total withdrawn blood volume (expressed as % of estimated total blood volume) to maintain MBP at 30 mmHg was significantly higher in the isoflurane group (51 ± 1.5 %) compared to the K/X group (45.3 ± 1.8 %; p=0.023). The diastolic internal dimension of the left ventricle, which indicated circulating intravascular blood volume, was significantly larger in the isoflurane group at the end of 1 hour of the shock phase (4.5 ± 0.2 mm compared to 3.5 ± 0.2 mm in K/X group; p=0.0003) and at 1 hour after initiation of shed blood reinfusion (6.3 ± 0.2 mm compared to 5.3 ± 0.3 in K/X group; p=0.014). Recovery of blood pressure during the resuscitation phase was significantly improved in the isoflurane group compared to the K/X group. The survival rate at 6 weeks was 1 of 12 (8.3%) in rats receiving K/X and 10 of 12 (83.3%) in rats receiving isoflurane (p &lt; 0.001). Histology demonstrated brain infarction in the 1 surviving rat receiving K/X; no brain infarction in the 10 surviving rats that received isoflurane at 6 weeks. No infarction was detected in heart, lung, liver or kidneys in all surviving rats. Conclusions: These results suggest that isoflurane stabilizes the cardiovascular response to acute blood lose and benefits the perfusion of tissue, which resulted in significantly higher long term survival rate and improved blood pressure response to resuscitation, without end-organ infarction.

Vasculotide, an Angiopoietin-1 Mimetic, Restores Microcirculatory Perfusion and Microvascular Leakage and Decreases Fluid Resuscitation Requirements in Hemorrhagic Shock

Microcirculatory dysfunction is associated with multiple organ failure and unfavorable patient outcome. We investigated whether therapeutically targeting the endothelial angiopoietin/Tie2 system preserves microvascular integrity during hemorrhagic shock. Rats were treated with the angiopoietin-1 mimetic vasculotide and subjected to hemorrhagic shock and fluid resuscitation. Microcirculatory perfusion and leakage were assessed with intravital microscopy (n = 7 per group) and Evans blue dye extravasation (n = 8 per group), respectively. The angiopoietin/Tie2 system was studied at protein and RNA level in plasma, kidneys, and lungs. Hemorrhagic shock significantly reduced continuously perfused capillaries (7 ± 2 vs. 11 ± 2) and increased nonperfused vessels (9 ± 3 vs. 5 ± 2) during hemorrhagic shock, which could not be restored by fluid resuscitation. Hemorrhagic shock increased circulating angiopoietin-2 and soluble Tie2 significantly, which associated with microcirculatory perfusion disturbances. Hemorrhagic shock significantly decreased Tie2 gene expression in kidneys and lungs and induced microvascular leakage in kidneys (19.7 ± 11.3 vs. 5.2 ± 3.0 µg/g) and lungs (16.1 ± 7.0 vs. 8.6 ± 2.7 µg/g). Vasculotide had no effect on hemodynamics and microcirculatory perfusion during hemorrhagic shock but restored microcirculatory perfusion during fluid resuscitation. Interestingly, vasculotide attenuated microvascular leakage in lungs (10.1 ± 3.3 µg/g) and significantly reduced the required amount of volume supplementation (1.3 ± 1.4 vs. 2.8 ± 1.5 ml). Furthermore, vasculotide posttreatment was also able to restore microcirculatory perfusion during fluid resuscitation. Targeting Tie2 restored microvascular leakage and microcirculatory perfusion and reduced fluid resuscitation requirements in an experimental model of hemorrhagic shock. Therefore, the angiopoietin/Tie2 system seems to be a promising target in restoring microvascular integrity and may reduce organ failure during hemorrhagic shock.

A deficiency in cold-inducible RNA-binding protein accelerates the inflammation phase and improves wound healing.

Chronic or non-healing wounds are a major concern in clinical practice and these wounds are mostly associated with diabetes, and venous and pressure ulcers. Wound healing is a complex process involving overlapping phases and the primary phase in this complex cascade is the inflammatory state. While inflammation is necessary for wound healing, a prolonged inflammatory phase leads to impaired healing. Cold-inducible RNA-binding protein (CIRP) belongs to a family of cold-shock proteins that are expressed in high levels under stress conditions. Recently, we demonstrated that a deficiency in CIRP led to decreased inflammation and mortality in an experimental model of hemorrhagic shock. Thus, we hypothesized that a deficiency in CIRP would accelerate the inflammatory phase and lead to an improvement in cutaneous wound healing. In this study, to examine this hypothesis, a full-thickness wound was created on the dorsum of wild-type (WT) and CIRP-/- mice. The wound size was measured every other day for 14 days. The wound area was significantly decreased in the CIRP-/- mice by day 9 and continued to decrease until day 14 compared to the WT mice. In a separate cohort, mice were sacrificed on days 3 and 7 after wounding and the skin tissues were harvested for histological analysis and RNA measurements. On day 3, the mRNA expression of tumor necrossis factor (TNF)-α in the skin tissues was increased by 16-fold in the WT mice, whereas these levels were increased by 65-fold in the CIRP-/- mice. Of note on day 7, while the levels of TNF-α remained high in the WT mice, these levels were significantly decreased in the CIRP-/- mice. The histological analysis of the wounded skin tissue indicated an improvement as early as day 3 in the CIRP-/- mice, whereas in the WT mice, infiltrated immune cells were still present on day 7. On day 7 in the CIRP-/- mice, Gr-1 expression was low and CD31 expression was high, whereas in the WT mice, Gr-1 expression was high and CD31 expression was low, indicating that the CIRP-/- mice have already moved into the angiogenesis and tissue formation phase, whereas the WT mice were still in the inflammatory state. These data collectively suggest that a deficiency in CIRP accelerates the wound healing process.

Heart Rate Variability Analysis in an Experimental Model of Hemorrhagic Shock and Resuscitation in Pigs.

BackgroundThe analysis of heart rate variability (HRV) has been shown as a promising non-invasive technique for assessing the cardiac autonomic modulation in trauma. The aim of this study was to evaluate HRV during hemorrhagic shock and fluid resuscitation, comparing to traditional hemodynamic and metabolic parameters.MethodsTwenty anesthetized and mechanically ventilated pigs were submitted to hemorrhagic shock (60% of estimated blood volume) and evaluated for 60 minutes without fluid replacement. Surviving animals were treated with Ringer solution and evaluated for an additional period of 180 minutes. HRV metrics (time and frequency domain) as well as hemodynamic and metabolic parameters were evaluated in survivors and non-survivors animals.ResultsSeven of the 20 animals died during hemorrhage and initial fluid resuscitation. All animals presented an increase in time-domain HRV measures during haemorrhage and fluid resuscitation restored baseline values. Although not significantly, normalized low-frequency and LF/HF ratio decreased during early stages of haemorrhage, recovering baseline values later during hemorrhagic shock, and increased after fluid resuscitation. Non-surviving animals presented significantly lower mean arterial pressure (43±7vs57±9 mmHg, P<0.05) and cardiac index (1.7±0.2vs2.6±0.5 L/min/m2, P<0.05), and higher levels of plasma lactate (7.2±2.4vs3.7±1.4 mmol/L, P<0.05), base excess (-6.8±3.3vs-2.3±2.8 mmol/L, P<0.05) and potassium (5.3±0.6vs4.2±0.3 mmol/L, P<0.05) at 30 minutes after hemorrhagic shock compared with surviving animals.ConclusionsThe HRV increased early during hemorrhage but none of the evaluated HRV metrics was able to discriminate survivors from non-survivors during hemorrhagic shock. Moreover, metabolic and hemodynamic variables were more reliable to reflect hemorrhagic shock severity than HRV metrics.

Case Scenario: Management of Trauma-induced Coagulopathy in a Severe Blunt Trauma Patient

Case Scenario: Management of Trauma-induced Coagulopathy in a Severe Blunt Trauma Patient

Proteolytically‐derived inflammatory peptides from the bowel may circulate systemically in shock

Small bowel malperfusion and increased permeability may be key pathologic events in shock, allowing gut‐derived inflammatory peptides systemic access. Proteolytically formed as part of normal digestion, the peptides do not normally cross the mucosal barrier but may do so in shock. To test this idea, rats were subjected to hemorrhagic shock (35 mmHg for 100 min) with laparotomy, and saline or the protease inhibitor nafamostat mesilate was injected into the small bowel. Control animals were subjected to laparotomy without shock. Fluorescently labeled casein was injected into the small bowel to determine the ability of proteolytically generated peptides to reach the systemic circulation. Permeability significantly increased after ischemia in all shock groups compared to controls as assessed by casein fluorescence in the mesenteric microcirculation and in plasma (p&lt;0.01). Nafamostat mesilate decreased permeability in the microcirculation and systemically (p&lt;0.01). These results demonstrate that in an experimental model of hemorrhagic shock, bowel permeability is significantly increased to proteolytically derived peptides, and is mitigated by enteral protease inhibition. Inflammatory peptides from the bowel may reach the systemic circulation and contribute to the pathophysiology of gut‐derived circulatory shock. Supported by GM85072, and the ASCCA/FAER/Hospira Physician Scientist Award.

Effects of the intravenous administration of purine nucleosides guanosine or inosine against hemorrhagic shock in pigs

Hemorrhagic shock leads to the appearance of substances in plasma that depress Na/K ATPase activity, an effect that could be related to significant morbidity and mortality. Recently, some findings indicated that purine nucleosides such as guanosine, inosine or adenosine might prolong survival in shocked rats, an effect potentially related to the stimulation of Na/K ATPase activity. This study aimed to evaluate the effects of intravenous administration of guanosine or inosine combined with lactate Ringer solution (LR) on hemodynamic and oxygenation parameters and survival in an experimental model of hemorrhagic shock (HS).

Ketamine delays mortality in an experimental model of hemorrhagic shock and subsequent sepsis

Background In previous studies ketamine was reported to improve survival and decrease serum interleukin-6 (IL-6) concentration after sepsis alone and after burn injury followed by sepsis. The aim of this study was to determine whether ketamine alters survival and/or IL-6 after hemorrhagic shock alone or hemorrhagic shock followed by sepsis. Materials and methods Rats were subjected to hemorrhagic shock with or without subsequent Gram-negative bacterial sepsis and were either treated with ketamine 5 mg/kg or were not treated. Blood was sampled for IL-6 determination prior to hemorrhage, at the completion of resuscitation, and at 6 and 30 h later. Mortality was recorded for 7 days following hemorrhage or hemorrhage + sepsis. Results After hemorrhage + sepsis the time to median mortality was significantly later in the ketamine-treated group (36 h) than in the control group (12 h). At 12 h the survival rate of the ketamine-treated group (100%) was significantly higher than in the control group (55%). There were no significant differences between groups with respect to IL-6 or 7-day survival after either hemorrhage + sepsis or hemorrhage alone. Conclusion Ketamine improved 12 h survival and delayed mortality after hemorrhage + sepsis without significantly altering IL-6, and did not alter survival or IL-6 after hemorrhage alone.

Comparison of pulse pressure variation and end-diastolic volume index in an experimental model of hemorrhagic shock in the pig

Different hemodynamic parameters, including static indicators of cardiac preload such as the end-diastolic volume index (EDVI) and dynamic parameters such as the pulse pressure variation (PPV) have been used in the decision-making process regarding volume expansion in critically ill patients. The objective of this study was to compare fluid resuscitation guided by either PPV or EDVI, after hemorrhagic shock.

Indução anestésica após o tratamento do choque hemorrágico: estudo experimental comparando a cetamina e o etomidato

Bleeding causing hemorrhagic shock usually requires surgical treatment under general anesthesia. Anesthetic drugs may further compromise hemodynamics. The objective was to compare the hemodynamic effects of ketamine and etomidate during anesthetic induction in dogs submitted to an experimental model of hemorrhagic shock and resuscitation.Thirty-two mongrel dogs were submitted to a pressure-controlled hemorrhagic shock, resuscitation and anesthetic induction model. After achieving the target pressure of 40 mmHg, they were randomly assigned in two groups according to the resuscitation fluid to be used: NaCl 0.9% (32 mL.kg-1) and NaCl 7.5% (4 mL.kg-1). After volume infusion, these groups were reassigned according to anesthetic drug used: GI) NaCl 0.9% and ketamine; GII) NaCl 7.5% and ketamine; GIII) NaCl 0.9% and etomidate; and GIV) NaCl 7.5% and etomidate. Hemodynamic measurements were obtained at five moments: (M0) baseline; (M1) after bleeding to shock; (M2) after volume expansion; (M3) 5 minutes after anesthetic induction; (M4) 15 minutes after anesthetic induction. Statistical analysis was performed using Student t test and two way ANOVA. Value of p lower than 0.05, was considered significant.After shock, both solutions restored hemodynamics to baseline values. Independently of anesthetic agent or expansion solution used, mean arterial pressure remained unaltered for all groups after induction. Central venous pressure, heart rate, pulmonary capillary wedge pressure and pulmonary vascular resistance index increased significantly after ketamine infusion. Cardiac index, systemic vascular resistance index and oxygen transport variables remained stable in all groups.Etomidate or ketamine were able to maintain hemodynamic stability in dogs undergoing severe hemorrhagic shock treated with NaCl 0.9% or NaCl 7.5%.

Crocetin Inhibits mRNA Expression for Tumor Necrosis Factor‐α, Interleukin‐1β, and Inducible Nitric Oxide Synthase in Hemorrhagic Shock

Inflammatory factors play an important role in cellular damage after shock and resuscitation. Crocetin, a saffron-derived carotenoid, has been shown to improve postshock recovery of cellular adenosine triphosphate (ATP) and to increase overall survival in an experimental model of hemorrhagic shock. The hypothesis of the present study is that treatment with crocetin at the beginning of resuscitation suppresses subsequent expression of messenger ribonucleic acid (mRNA) for tumor necrosis factor (TNF-alpha), interleukin-1 (IL-1beta) and inducible nitric oxide synthase (iNOS). Male Sprague-Dawley rats (n = 45, 350 +/- 30 g) were randomly assigned to 5 groups of 9 animals each. After anesthesia with isoflurane, the femoral artery and vein were surgically cannulated. Hemorrhagic shock was induced by withdrawing blood through the arterial cannula until the mean arterial pressure (MAP) was 25-30 mm Hg and maintained at the level for 30 minutes with further withdrawals. Resuscitation was carried out by giving 21 mL/kg Ringer's lactate (LR) and returning the shed blood, with or without the initial administration of crocetin (2 mg/kg). Controls were normal (anesthesia only), sham (surgical preparation), and shock (preparation and shock). Rats were killed 30 minutes after completion of resuscitation. Liver samples were collected for reverse transcription-polymerase chain reaction (RT-PCR) analysis of mRNA (TNF-alpha, IL-1beta, iNOS, and beta-actin). Liver mRNA expression for TNF-alpha, IL-1beta, and iNOS was found in more animals in the shock and shock-plus-resuscitation groups than in the sham control group. The group resuscitated from shock with crocetin had mRNA expression for TNF-alpha, IL-1beta, and iNOS in fewer animals than either of the other shock groups and was no different from the sham control group. Crocetin modified the hepatic mRNA expression of cytokines and iNOS in a shock model. This agent continues to show promise as a potential treatment for hemorrhagic shock.

Modelo experimental de choque hemorrágico

OBJETIVO: É estabelecer um modelo experimental de choque hemorrágico, reproduzindo o mais próximo possível uma real situação que ocorre nas vítimas traumatizadas. MÉTODOS: Utilizou-se 16 animais, distribuídos aleatoriamente em 2 grupos (n=8): Grupo Controle (GC): procedimentos cirúrgicos e observação de 60 minutos; Grupo Choque (GCh): procedimentos cirúrgicos, sangria para estabelecimento do estado de choque (EC) com pressão arterial média (PAM) em 40 mmHg, mantido por 20 minutos (20') seguido de período de reperfusão de 60 minutos (RP60). Para avaliar o EC estabelecido, além da PAM, utilizaram-se os seguintes parâmetros: lactato sérico (LS) e diferença de base (DB). Na instalação do EC, iniciou-se com retirada de volume de sangue correspondente a 5% da volemia estimada até atingir PAM de 60mmHg, ponto do qual as retiradas passaram para 2,5%. RESULTADOS: Após o período de 20' do EC o LS médio do GC foi de 0,92 mmol/l e do GCh foi de 4,16 mmol/l. A DB média do GC foi de 0,02 mmol/l e do GCh foi de 8, 12 mmol/l. CONCLUSÃO: As alterações resultantes do processo de instalação e reanimação do EC mostraram uma relação inversamente proporcional entre LS e DB, fato que confirma a má perfusão tecidual e restauração volêmica dentro do presente modelo experimental.

The Attenuation of Hemorrhage-Induced Liver Injury by Exogenous Nitric Oxide, L -Arginine, and Inhibition of Inducible Nitric Oxide Synthase

We investigated the role of nitric oxide (NO) in its ability to reduce liver injury in an animal model of hemorrhagic shock (HS). Ninety-six Sprague-Dawley rats weighing 250 to 300 g were divided in 6 groups ( n = 16 per group) that included treatment at the beginning of resuscitation with normal saline (groups 1, 3) sodium nitroprusside (NP) (0.5 mg/kg) (groups 2, 4) L -arginine (300 mg/kg) (group 5), and L - N 6 -(1-iminoethyl) lysine (L-NIL, 40 mg/kg) (group 6). The experimental model of HS consisted of the withdrawal of 3 mL blood per 100 g in a 15-min period, tail amputation (75%), and drug administration at 30 min. This was followed by fluid resuscitation (FR) with lactated Ringer's (LR) solution to reach a mean arterial pressure (MAP) of 40 mm Hg, then a hospital phase of 60 min with hemostasis and FR with LR solution to reach a MAP of 70 mm Hg with a 3-day observation phase. NP, L -Arginine, and L-NIL significantly reduced fluid requirements for resuscitation ( p = .0001) as well as significantly increased MAP after resuscitation from hemorrhage. We also observed an improved statistically significant difference ( p = .001) in tests demonstrating less hepatic injury and histology damage. The mRNA expression of cytokines in the liver (interleukin [IL]-1 f , IL- g 1, tumor necrosis factor [TNF] g , IL-3, IL-4, IL-5, IL-6, IL-10, TNF f , IL-2, interferon [IFN] n ) was reduced by NP treatment, L -arginine, and L-NIL. These data suggest that excess NO mediates hemorrhage-induced liver injury and that the suppression of inducible nitric oxide synthase (iNOS)-generated NO bioavailability with the NO donor sodium nitroprusside may reduce the pathophysiologic consequences of severe hemorrhage. This effect could be possibly related to the scavenging of to superoxide radicals (O 2 m ) or the blockade of the deleterious effects of TNF and other inflammatory cytokines. The protective action noted with L -arginine cannot be fully explained within the context of this article, although it could be most likely associated with the supplementation of eNOS-generated NO.

Experimental Model of Hemorrhagic Shock in Swine

Martini, L. Fini, M., Giavaresi, G. and Giardino R. 2001. Experimental model of hemorrhagic shock in swine. J. Appl. Anim. Res., 20: 107–116. A hemorrhagic shock was created in 12 hybrid swine under general anaesthesia by bleeding of 30% of total blood volume and the duration of the shock was 90 minutes. Circulatory parameters progressively decreased (p < 0.005) except for heart rate that progressively increased. End-tidal C02 showed a modest increase of about 7% during the shock between 30 and 60 min after bleeding. Cardiac output and index significantly (p < 0.0005) decreased in the first 30 min. Systemic vascular resistance trend- showed an early fall at the beginning of bleeding, while pulmonary vascular resistance increased (p < 0.01) following an almost linear pattern for 60 min of shock. Oxygen delivery index progressively decreased, while oxygen consumption index remained unchanged. To sum up, this experimental model can be used to evaluate the most reliable monitoring instruments.