Endotoxemia In Sheep Research Articles

Effects of nitroglycerin and flunixin meglumine on circulating inflammatory, cardiovascular and hepatorenal biomarkers of ovine experimental endotoxemia model

Owing to the importance of endotoxemia and its risks, several studies have been conducted to better understand the pathophysiological processes of this disease, and many treatments have been suggested. Nitroglycerin is one of the drugs recommended for the treatment of endotoxemia and its therapeutic effects in some researches have been evaluated in human and animal models. However, there are no comprehensive studies on the effects of nitroglycerin on different circulating inflammatory, cardiovascular and hepatorenal biomarkers following endotoxemia in sheep; therefore, the present experiment was conducted to evaluate the anti-inflammatory effects of two different doses of nitroglycerin compared to the standard dose of flunixin meglumine in the treatment of endotoxemia in sheep. Hence, 25 clinically healthy 1-year old Iranian fat-tailed ewes were randomly divided into 5 equal groups, comprising NTG 0.2, NTG 0.4, Flnx, Ctrl+, and Ctrl-. Lipopolysaccharide from Escherichia coli serotype O55:B5 at 0.4 μg/kg was intravenously administered to the ewes. Flunixin meglumine (at 2.2 mg/kg) and nitroglycerin (at 0.2 and 0.4 μg/kg) were administrated to Flnx, NTG 0.2 and NTG 0.4 groups, respectively. All the ewes were clinically evaluated before and 1.5, 3, 3.5, 4, 4.5, 6 and 24 h after lipopolysaccharide injection, and blood samplings were also performed at those hours. Serum concentrations of haptoglobin, serum amyloid A, tumor necrosis factor-alpha, interferon-gamma, total antioxidant status, malondialdehyde, superoxide dismutase, glutathione peroxidase, creatine kinase-MB, cardiac lactate dehydrogenase, cardiac troponin-I, homocysteine, total bilirubin, aspartate aminotransferase, alanine transaminase, and creatinine were measured. Serum concentrations of acute phase proteins, inflammatory cytokines, oxidative stress, cardiovascular, hepatic and renal biomarkers, and clinical parameters were significantly increased following the induction of endotoxemia in the groups receiving lipopolysaccharide. The results indicated that nitroglycerin at both 0.2 and 0.4 μg/kg did not play an effective role in reducing inflammatory biomarkers and could not reduce circulating hepatic biomarkers following endotoxemia. However, nitroglycerin at 0.4 μg/kg significantly reduced circulating cardiac and renal biomarkers compared to 0.2 μg/kg and flunixin meglumine at 2.2 mg/kg. Clinical evaluations also demonstrated that nitroglycerin could not reduce the heart rate and body temperature compared to flunixin meglumine but significantly reduced respiratory rates at 0.4 μg/kg. In conclusion, nitroglycerin at 0.2 and 0.4 μg/kg could not alleviate inflammatory processes and oxidative stress. Nitroglycerin at 0.2 and 0.4 μg/kg also had suitable effects on reducing the serum concentration of cardiovascular and renal biomarkers, but it was not effective on circulating hepatic indices. Therefore, nitroglycerin at the doses used in this study could not be suggested as an effective drug in reducing inflammatory and hepatic biomarkers which were elevated during endotoxemia in sheep.

Un-fractionated heparin counteracts the systemic inflammatory responses and multiple organ damages caused by endotoxaemia in sheep.

BackgroundEndotoxaemia is believed to be a major cause of mortality and there are several therapeutic regimens for the treatment of this situation.ObjectivesThe present experimental study was conducted to evaluate acute phase response, cardiovascular and hepatorenal damages following the treatment of Ovine experimental endotoxaemia model employing unfractionated heparin (UFH).Materials and MethodsTwenty clinically healthy 1‐year‐old fat‐tailed ewes were randomly divided into four equal groups, comprising UFH 200, UFH 400, Ctrl+ and Ctrl‐. Lipopolysaccharide (LPS) from Escherichia coli serotype O55:B5 at 0.4 μg/kg was administered intravenously to the ewes. UFH (at 200 and 400 IU/kg) was administrated to the UFH 200 and UFH 400 groups, respectively. All the ewes were evaluated clinically before and 1.5, 3, 4.5, 6 and 24 hours after LPS injection. Blood samplings were also performed at those hours. We measured serum concentrations of haptoglobin, interferon‐gamma, total antioxidant status, malondialdehyde, cardiac lactate dehydrogenase, cardiac troponin‐I, total bilirubin, alanine transaminase and creatinine. Serum concentrations of acute phase response, cardiovascular, hepatic and renal biomarkers and clinical parameters increased significantly following the induction of endotoxaemia in the groups receiving LPS.ResultsThe significantly lowest concentrations of these parameters at hours 4.5 and 6 among the treatment groups belonged to the UFH 400 sheep.ConclusionsUFH could act as an anti‐inflammatory mediator by decreasing inflammatory cytokines and acute phase proteins, modulating oxidative stress biomarkers and reducing multiple organ dysfunction following endotoxaemia in a dose–dependent manner. Furthermore, the anti‐inflammatory effects of UFH at 400 IU/kg were significantly higher than another dose. This research examined the effect of two doses of UFH and higher doses may have more anti‐inflammatory effects that require further studies.

Therapeutic regimens of endotoxaemia in sheep

Endotoxaemia is an inflammatory condition which happens due to the presence of outer cell wall layer of Gram-negative bacteria in blood circulation, containing lipopolysaccharide commonly known as endotoxin. This condition causes high mortality in affected animals and sheep are highly susceptible in this regard. Several researchers have emphasised the therapeutic regimens of endotoxaemia and its sequels in sheep. Furthermore, sheep are among the most commonly used animal species in experimental studies on endotoxaemia, and for the past five decades, ovine models have been employed to evaluate different aspects of endotoxaemia. Currently, there are several studies on experimentally induced endotoxaemia in sheep, and information regarding novel therapeutic protocols in this species contributes to better understanding and treating the condition. This review aims to specifically introduce various treatment methods of endotoxaemia in sheep.

Low molecular weight heparin reduces acute phase response and multiple organ dysfunction following Ovine experimental endotoxemia model

Endotoxemia is one of the most common inflammatory situations leading to death of ruminants. Owing to the importance of this condition, several therapeutic regimens have been proposed, evaluated and implemented to treat endotoxemia. It has recently been suggested that low molecular weight heparin may be effective in treating endotoxemia. Thus, the present experimental study was conducted to evaluate the acute phase response and multiple organ dysfunction following the treatment of the Ovine experimental endotoxemia model employing this compound. In this regard, 20 clinically healthy 1-year old Iranian fat-tailed ewes were randomly divided into 4 equal groups, comprising LMWH 50, LMWH 100, Ctrl+, and Ctrl-. Lipopolysaccharide from Escherichia coli serotype O55:B5 at 0.4 μg/kg was intravenously administered to the ewes. Low molecular weight heparin (at 50 and 100 IU/kg) was administrated to LMWH 50 and LMWH 100 groups, respectively. Positive control (Ctrl+) received lipopolysaccharide and treated only by intravenous fluid without any drugs, and negative control (Ctrl-) only received intravenous fluids without lipopolysaccharide or any drugs. All the ewes were clinically evaluated before and 1.5, 3, 4.5, 6 and 24 h after lipopolysaccharide injection, and blood samplings were also performed at those hours. Serum concentrations of serum amyloid A, tumor necrosis factor-alpha, superoxide dismutase, glutathione peroxidase, creatine kinase-MB, homocysteine, total bilirubin, aspartate aminotransferase, and creatinine were measured. Serum concentrations of acute phase proteins, inflammatory cytokines, oxidative stress, cardiovascular, hepatic and renal biomarkers, and clinical parameters were significantly increased following the induction of endotoxemia in the groups receiving lipopolysaccharide. Significantly lower concentration of these markers was observed at 4.5 and 6 h after lipopolysaccharide administration in the sheep treated with LMWH compared to the Ctrl + group. In conclusion, low molecular weight heparin could act as an anti-inflammatory drug by decreasing cytokines and acute phase proteins, modulating oxidative stress biomarkers, and by reducing multiple organ dysfunction following the induction of endotoxemia by Escherichia coli serotype O55:B5 in Iranian fat-tailed sheep in a dose-dependent manner. Furthermore, the anti-inflammatory effects of low molecular weight heparin at 100 IU/kg were significantly higher than 50 IU/kg in the treatment of endotoxemic sheep.

Effects of polymyxin B on clinical signs, serum TNF-α, haptoglobin and plasma lactate concentrations in experimental endotoxaemia in sheep

Abstract Introduction The experiment evaluated the effects of intravenous administration of polymyxin B on experimental endotoxaemia in sheep. Material and Methods Twenty clinically healthy fat-tailed sheep were randomly divided into: a group treated with 6,000 U/kg of polymyxin B, a group at 12,000 U/kg, and positive and negative controls. Endotoxaemia was induced by intravenous administration of lipopolysaccharide (LPS) from E. coli serotype O55:B5 at 0.5 μg/kg. polymyxin was infused intravenously along with 2.5 L of isotonic intravenous fluids at 20 mL/kg/h. The positive control group received LPS and 2.5 L of isotonic fluids, the negatives receiving just 2.5 L of isotonic fluids. Clinical signs were evaluated before and at 1.5, 3, 4.5, 6, 24, and 48 h after LPS administration. Blood was also sampled at the denoted hours and serum haptoglobin, tumour necrosis factor-α (TNF-α), and plasma lactate concentrations were assayed. Results The serum concentration of TNF-α in the positive control group increased significantly up to 48 h after LPS administration. The concentration of TNF-α was significantly different from those of the polymyxin B and positive control groups from 3 to 48 h; also, the concentrations of haptoglobin at different times in the polymyxin groups were lower than those of the positive control group and were significant at hours 3 to 48 (P < 0.05). Following the LPS administration, haptoglobin and TNF-α concentrations changed without significant difference between the two polymyxin B groups. Conclusion Polymyxin B (6,000 U/kg) restrained blood lactate concentrations. Furthermore, it significantly improved the clinical signs in endotoxaemic animals, including rectal temperature and heart and respiratory rates. Polymyxin B may be an antiendotoxic in fat-tailed sheep.

Effects of Polymyxin B on Clinical Signs, Serum TNF-α, Haptoglobin and Plasma Lactate Concentrations in Experimental Endotoxaemia in Sheep

IntroductionThe experiment evaluated the effects of intravenous administration of polymyxin B on experimental endotoxaemia in sheep.Material and MethodsTwenty clinically healthy fat-tailed sheep were randomly divided into: a group treated with 6,000 U/kg of polymyxin B, a group at 12,000 U/kg, and positive and negative controls. Endotoxaemia was induced by intravenous administration of lipopolysaccharide (LPS) from E. coli serotype O55:B5 at 0.5 μg/kg. polymyxin was infused intravenously along with 2.5 L of isotonic intravenous fluids at 20 mL/kg/h. The positive control group received LPS and 2.5 L of isotonic fluids, the negatives receiving just 2.5 L of isotonic fluids. Clinical signs were evaluated before and at 1.5, 3, 4.5, 6, 24, and 48 h after LPS administration. Blood was also sampled at the denoted hours and serum haptoglobin, tumour necrosis factor-α (TNF-α), and plasma lactate concentrations were assayed.ResultsThe serum concentration of TNF-α in the positive control group increased significantly up to 48 h after LPS administration. The concentration of TNF-α was significantly different from those of the polymyxin B and positive control groups from 3 to 48 h; also, the concentrations of haptoglobin at different times in the polymyxin groups were lower than those of the positive control group and were significant at hours 3 to 48 (P < 0.05). Following the LPS administration, haptoglobin and TNF-α concentrations changed without significant difference between the two polymyxin B groups.ConclusionPolymyxin B (6,000 U/kg) restrained blood lactate concentrations. Furthermore, it significantly improved the clinical signs in endotoxaemic animals, including rectal temperature and heart and respiratory rates. Polymyxin B may be an antiendotoxic in fat-tailed sheep.

Impact of tyloxapol to combat acute phase response in comparison with betamethasone and flunixin meglumine following an ovine experimentally induced endotoxemia model

Systemic inflammatory responses to circulating lipopolysaccharide lead to high mortality rates in affected animals and thus effective treatments of this situation are crucial. However, despite different endotoxemia therapeutic regimens, the lack of an effective treatment still remains a clinical problem in sheep. Tyloxapol is a potential pro- and anti-inflammatory molecule to treat endotoxemia in farm animals. Hence, the present study was an attempt to clarify the antiendotoxic effects of tyloxapol in comparison with betamethasone and flunixin meglumine in experimentally induced endotoxemia in sheep. Thirty clinically healthy 1-year old Iranian fat-tailed ewes were randomly divided into 6 equal experimental (n=5) groups, comprising Negative and Positive control, Flunixin meglumine, Betamethasone, Tyloxapol 1 and Tyloxapol 2. Phenol extracted lipopolysaccharide from &lt;em&gt;Escherichia coli&lt;/em&gt; serotype O55:B5 was infused at 2 μg/kg intravenously. Ninety min after endotoxemia induction, Flunixin meglumine (2.2 mg/kg), betamethasone (1 mg/kg) and tyloxapol (200 and 400 mg/kg) were injected to respective groups, over 60 min along with intravenous fluids. Blood samples were collected from all ewes prior and 1.5, 3, 4.5, 6, 24 and 48 hours after lipopolysaccharide injection and sera and plasmas were separated, subsequently. Haptoglobin, serum amyloid A, tumor necrosis factor-alpha, interferon-gamma, superoxide dismutase and glutathione peroxidase were measured in all samples. Serum concentrations of haptoglobin, serum amyloid A, tumor necrosis factor-alpha, interferongamma in Flunixin meglumine group were found to be lower than other experimental ones after hour 3. Serum levels of haptoglobin, serum amyloid A, tumor necrosis factor-alpha, interferon-gamma in Tyloxapol groups were significantly lower and higher than Betamethasone and Flunixin meglumine ones, respectively. Superoxide dismutase and glutathione peroxidase activities in Flunixin meglumine group were significantly higher than other experimental groups after administration of drugs. In conclusion, the efficacy of tyloxapol was significantly higher and lower than betamethasone and flunixin meglumine, respectively. Furthermore, tyloxapol doesn’t induce its effects by dose dependent manner and its anti- and pro-inflammatory effects at 200 and 400 mg/kg were statistically similar.

Plasma and tissue disposition of florfenicol in Escherichia coli lipopolysaccharide-induced endotoxaemic sheep

1. The purpose of this study was to understand the effects of the acute inflammatory response (AIR) induced by Escherichia coli lipopolysaccharide (LPS) on florfenicol (FFC) and FFC-amine (FFC-a) plasma and tissue concentrations.2. Ten Suffolk Down sheep, 60.5 ± 4.7 kg, were distributed into two experimental groups: group 1 (LPS) treated with three intravenous doses of 1 μg/kg bw of LPS at 24, 16, and 0.75 h (45 min) before FFC treatment; group 2 (Control) was treated with saline solution (SS) in parallel to group 1. An IM dose of 20 mg FFC/kg was administered at 0.75 h after the last injection of LPS or SS. Blood and tissue samples were taken after FFC administration.3. The plasma AUC0–4 h values of FFC were higher (p = 0.0313) in sheep treated with LPS (21.8 ± 2.0 μg·min/mL) compared with the control group (12.8 ± 2.3 μg·min/mL). Lipopolysaccharide injections increased FFC concentrations in kidneys, spleen, and brain. Low levels of plasma FFC-a were observed in control sheep (Cmax = 0.14 ± 0.01 μg/mL) with a metabolite ratio (MR) of 4.0 ± 0.87%. While in the LPS group, Cmax increased slightly (0.25 ± 0.01 μg/mL), and MR decreased to 2.8 ± 0.17%.4. The changes observed in the plasma and tissue concentrations of FFC were attributed to the pathophysiological effects of LPS on renal hemodynamics that modified tissue distribution and reduced elimination of the drug.

Attenuating the endotoxin induced acute phase response by pentoxifylline in comparison with dexamethasone and ketoprofen in sheep

Treating the endotoxemia in animals is necessary to prevent high mortality rates. Despite the suggestion of different endotoxemia therapeutic regimens, the lack of an effective treatment still remains a clinical problem in sheep. Hence, the present study was performed to clarify the antiendotoxic effects of pentoxifylline in comparison with dexamethasone and ketoprofen in experimentally induced endotoxemia in sheep. Thirty clinically healthy 1-year old Iranian fat-tailed ewes were randomly divided into 6 equal experimental (n=5) groups, comprising negative and positive control, ketoprofen (3mg/kg), dexamethasone (1mg/kg) and pentoxifylline (30 and 60mg/kg). Lipopolysaccharide from Escherichia coli serotype O55:B5 was infused at 2μg/kg intravenously. Ketoprofen, dexamethasone and pentoxifylline were injected to related groups, at 90min after endotoxemia induction over 60min along with intravenous fluids. Blood samples were collected from all ewes prior and 1.5, 3, 4.5, 6, 24 and 48h after lipopolysaccharide injection and sera and plasmas were separated, subsequently. Haptoglobin, serum amyloid A, tumor necrosis factor-alpha, interferon-gamma, superoxide dismutase and glutathione peroxidase were measured in all samples. Serum levels of haptoglobin, serum amyloid A, tumor necrosis factor-alpha, interferon-gamma in both pentoxifylline groups were significantly lower and higher than dexamethasone and ketoprofen ones, respectively. In conclusion, the efficacy of pentoxifylline was significantly higher and lower than dexamethasone and ketoprofen, respectively. Furthermore, its anti- and pro-inflammatory effects at 30 and 60mg/kg were statistically similar together.

The comparative efficacy of tyloxapol versus pentoxifylline against induced acute phase response in an ovine experimental endotoxemia model

The effective treatments of endotoxemia are necessary to prevent high mortality rates. Hence, the present study was performed to clarify the antiendotoxic effects of tyloxapol and pentoxifylline in experimentally induced endotoxemia in sheep. Thirty clinically healthy 1-year-old Iranian fat-tailed ewes were randomly divided into six equal experimental (n=5) groups, comprising Negative and Positive control, Tyloxapol 1, Tyloxapol 2, Pentoxifylline 1 and Pentoxifylline 2. Phenol extracted lipopolysaccharide from Escherichia coli serotype O55:B5 was infused at 2µg/kg intravenously. Tyloxapol (200 and 400mg/kg) and pentoxifylline (30 and 60mg/kg) were injected to Tyloxapol and Pentoxifylline groups, respectively, at 90min after endotoxemia induction over 60min along with intravenous fluids. Blood samples were collected from all ewes prior and 1.5, 3, 4.5, 6, 24 and 48h after lipopolysaccharide injection and sera and plasmas were separated, subsequently. Haptoglobin, serum amyloid A, tumor necrosis factor-alpha (TNF-α), interferon-gamma (IFN-γ), superoxide dismutase and glutathione peroxidase were measured in all samples. Serum concentrations of haptoglobin, serum amyloid A, TNF-α and IFN-γ in Tyloxapol 1 and 2 and Pentoxifylline 1 and 2 groups were significantly lower than Positive control one after hour 3. There were no significant differences among Tyloxapol and Pentoxifylline groups (P>0.05). Superoxide dismutase and glutathione peroxidase activities in Tyloxapol 1 and 2 and Pentoxifylline 1 and 2 groups were significantly lower than Positive control one after hour 3. There were no significant differences among Tyloxapol 1 and 2 and Pentoxifylline 1 and 2 groups (P>0.05). Tyloxapol and pentoxifylline act as the anti-inflammatory mediators by decreasing pro-inflammatory cytokines and hepatic APPs and modulating oxidative enzymes activity after endotoxemia induction in sheep. Furthermore, their efficacies at different doses were significantly similar together and both drugs don't induce their effects by dose dependent manner and the anti- and pro-inflammatory effects of them were statistically similar.

The relationships among acute phase response proteins, cytokines, and enzymes during ovine experimental endotoxemia

BACKGROUND: The acute phase response is beneficial to theanimal in restoring homeostasis, and measuring the circulatingacute phase proteins, cytokines, and enzymes can be used toevaluate the innate immune system's responses to invader agentssuch as bacterial lipopolysaccharide. Measurement of theseparameters has shown to be useful as diagnostic and prognosticmarkers in animal endotoxemia. OBJECTIVES: The aim of thepresent experimental study was expression of the acute phaseresponse following the induction of endotoxemia by Escherichiacoli serotype O55:B5 in sheep and the relationships among the acutephase response parameters during endotoxemia and their changingpatterns. METHODS: Five clinically healthy 1-year-old Iranian fattailedewes (25±1.5 kg, bodyweight) were randomly selected andlipopolysaccharide from Escherichia coli serotype O55:B5 wasinfused at 20 μg/kg intravenously to each animal. Fluid therapy wasperformed in all ewes over 120 minutes after lipopolysaccharideinjection and continued for 180 minutes. Blood samples werecollected from all ewes prior and 1, 2, 3, 4, 5, 6, and 24 hours afterlipopolysaccharide injection and sera were separated. Serumconcentrations of haptoglobin, serum amyloid A, tumor necrosisfactor-alpha, interferon-gamma, superoxide dismutase, andglutathione peroxidase were assayed. RESULTS: The rapid andsignificant elevation of haptoglobin, serum amyloid A, tumornecrosis factor-alpha, and interferon-gamma were seen afterendotoxemia induction. Serum concentrations of superoxidedismutase and glutathione peroxidase were significantly decreasedafter intravenous lipopolysaccharide infusion. The results of thepresent experimental study showed that haptoglobin, serumamyloid A, tumor necrosis factor-alpha, and interferon-gamma atall hours studied after endotoxemia induction were positivelycorrelated together. These parameters were negatively correlatedwith superoxide dismutase and glutathione peroxidase at all hoursafter lipopolysaccharide infusion. CONCLUSIONS: The results ofthe present experiment can provide evidence for associationsamong acute phase proteins, cytokines, and enzymes and theirchanges during endotoxemia in sheep.

Modulation of inflammatory responses following insulin therapy in experimentally bolus intravenous Escherichia coli lipopolysaccharide serotype O55:B5 induced endotoxemia in Iranian fat-tailed sheep

The present experimental study was conducted to evaluate the anti-inflammatory effects of different doses of insulin regular on treatment of endotoxemia in sheep. Thirty clinically healthy 1-year old Iranian fat-tailed ewes were randomly divided to 6 equal experimental groups (n=5) containing Insln 1.5, Insln 3, Insln 6, Insln 9, Insln 20 and Control. Lipopolysaccharide from Escherichia coli serotype O55:B5 infused intravenously to induce endotoxemia. Insulin regular was infused at 1.5, 3, 6, 9 and 20IU/kg in Insln 1.5, Insln 3, Insln 6, Insln 9 and Insln 20 groups, respectively. Control group received lipopolysaccharide and was treated only by intravenous fluid without any drugs. Blood samplings were performed before and 1, 2, 3, 4, 5, 6 and 24h after lipopolysaccharide injection. Sera were assayed for haptoglobin, serum amyloid A, tumor necrosis factor-alpha, interferon-gamma, superoxide dismutase and glutathione peroxidase. The results of the current study showed that insulin regular at 3IU/kg was more effective than other doses in controlling acute phase response following endotoxemia induction (P<0.05). It may be suggested that this dose of intravenous insulin regular can have new potential anti-inflammatory effects on systemic inflammatory responses in small ruminant medicine.

Anti-inflammatory effects of insulin regular and flunixin meglumine on endotoxemia experimentally induced by Escherichia coli serotype O55:B5 in an ovine model

Endotoxemia is a major cause of mortality in large animals and there are several therapeutic regimens for the treatment of endotoxemia. Recent studies have suggested the anti-inflammatory effects of insulin in endotoxemic human and laboratory animal models but to the best of our knowledge there is no report on the possible therapeutic effect of insulin in large animal endotoxemia. This experiment was conducted to evaluate the anti-inflammatory effects of insulin regular compared with flunixin meglumine on the treatment of endotoxemia in sheep. Lipopolysaccharide from Escherichia coli was administered intravenously to ewes. Anti-inflammatory effects of flunixin meglumine (at 2.2mg/kg) and insulin regular (at 1.5 and 3IU/kg) were evaluated by determination of serum concentrations of acute phase proteins, inflammatory cytokines and oxidative stress biomarkers. Insulin regular at 3IU/kg controlled the acute phase response following endotoxemia induction. The anti-inflammatory potency of insulin regular at 3IU/kg was significantly higher than at 1.5IU/kg and of flunixin meglumine at 2.2mg/kg (P<0.05). Insulin regular induces its anti-inflammatory effects in a dose-dependent manner. Intravenous use of insulin regular can be a potential new therapeutic regimen for endotoxemia in large animal medicine.

Toll-Like Receptor 4 Inhibitor TAK-242 Attenuates Acute Kidney Injury in Endotoxemic Sheep

This study was conducted to investigate the role of toll-like receptor 4 (TLR4) in mediating acute kidney injury in endotoxemic sheep using the selective TLR4 inhibitor TAK-242. A randomized, controlled, experimental study was performed with 20 adult Texel crossbred sheep. Before an Escherichia coli lipopolysaccharide infusion (3 μg · kg(-1) · h(-1) for 24 h), sheep were randomized to receive a bolus dose (2 mg/kg), followed by a continuous infusion (4 mg · kg(-1) · 24 h(-1)) of either TAK-242 (n = 7) or vehicle (n = 7). A third group of lipopolysaccharide-treated sheep (n = 6) received norepinephrine, titrated to maintain baseline arterial blood pressure. Endotoxin infusion established a state of hyperdynamic circulation, with an increased cardiac index, hypotension, and tachycardia. Urine output and creatinine clearance decreased throughout the experiment, together with increasing plasma creatinine, blood urea nitrogen, and arterial lactate concentrations. After 24 h, TLR4 inhibition had significantly (P ≤ 0.001) attenuated the mean ± SEM decrease in arterial pressure (97 ± 3 vs. 71 ± 4 mmHg), urine output (1.16 ± 0.15 vs. 0.13 ± 0.05 ml · kg(-1) · h(-1)), and creatinine clearance (126 ± 13 vs. 20 ± 7 ml/min) compared with vehicle-treated animals. Furthermore, arterial lactate, plasma creatinine, and blood urea nitrogen concentrations were significantly lower in the TAK-242 group versus the vehicle-treated animals. Compared with TLR4 inhibition, norepinephrine caused similar effects on arterial pressure, cardiac index, and heart rate; however, it did not attenuate the decrease in urine output or creatinine clearance. These results indicate a critical role for TLR4 in impairing renal function during ovine endotoxemia that is independent of changes in central hemodynamics.

ANESTHESIA AGGRAVATES LUNG DAMAGE AND PRECIPITATES HYPOTENSION IN ENDOTOXEMIC SHEEP

Beneficial anti-inflammatory properties have been ascribed to volatile anesthetics in septic conditions, but no studies have compared anesthesia to the conscious state in a large-animal model. The aim of this study was to investigate the effect of isoflurane anesthesia on cardiovascular and respiratory function, leukocyte activation, and lung damage in a model of endotoxemia in sheep. Conscious (n = 6) and anesthetized (n = 6) sheep were made endotoxemic by continuous infusion of LPS for 48 h. Central hemodynamics were monitored continuously, and blood samples were collected regularly. Activation of leukocytes was assessed by surface expression of CD11b and plasma myeloperoxidase concentration. Lung damage was determined by electron microscopy, cell count in bronchoalveolar lavage fluid, and analysis of lung vascular permeability. Four additional animals (two conscious and two anesthetized) went through the same protocol but did not receive LPS. LPS infusion induced a hyperdynamic sepsis. The drop in total peripheral resistance was compensated by an increase in heart rate and cardiac output in the conscious group, whereas anesthetized sheep failed to compensate in this way. Endotoxemic isoflurane-anesthetized sheep also showed signs of aggravated lung edema formation and tissue damage together with enhanced neutrophil activation and lung tissue accumulation. Our data suggest that isoflurane in conjunction with mechanical ventilation blunts cardiovascular compensatory mechanisms in sepsis and enhances leukocyte activation, which may contribute to lung edema formation and tissue damage.

WHAT'S NEW IN SHOCK, OCTOBER 2010?

WHAT'S NEW IN SHOCK, OCTOBER 2010?

Impact of saline-based tetrastarch vs balanced tetrastarch and crystalloid solutions on hyperchloraemic acidosis in endotoxaemic sheep

Septic shock is frequently associated with metabolic acidosis derived from increased lactic acid production and infusion of sodium chloride-based resuscitation fluids. Although the impact of hyperchloraemic acidosis on outcome is still not fully understood, avoiding such a condition is desirable. The hypothesis of the present study was that resuscitation with saline-based tetrastarch solutions results in higher plasma chloride and lower base excess levels as compared with either balanced tetrastarch or crystalloid solutions in ovine endotoxaemic shock.

EMPLOYING DOBUTAMINE AS A USEFUL AGENT TO REVERSE THE TERLIPRESSIN-LINKED IMPAIRMENTS IN CARDIOPULMONARY HEMODYNAMICS AND GLOBAL OXYGEN TRANSPORT IN HEALTHY AND ENDOTOXEMIC SHEEP

Although arginine vasopressin and terlipressin have been identified as useful nonadrenergic agents to increase systemic blood pressure in catchecholamine-resistant septic shock, the impairments in cardiac index (CI) and global oxygen transport may limit their clinical applicability. The present study was designed as a prospective controlled laboratory experiment to investigate the effects of dobutamine as an adjunct to terlipressin infusion on cardiopulmonary hemodynamics and global oxygen transport in healthy and endotoxemic sheep. Nine adult ewes were instrumented for chronic study using an established protocol. After a baseline measurement in the healthy state had been performed, 1 mg terlipressin was given as bolus infusion. Thirty minutes later, dobutamine was continuously infused at incremental doses (2 and 5 microg x kg(1) x min(1), each for 1 h). After 24 h of recovery, a hypotensive-hyperdynamic circulation was induced and maintained by a continuous infusion of Salmonella typhosa endotoxin (10 ng x kg(1) x min(1)). After 16 h of endotoxemia, the six surviving sheep received terlipressin and dobutamine according to the same protocol that was used in healthy sheep. Compared with baseline, terlipressin infusion was associated with a significant increase in MAP that, however, occurred at the expense of a compromised CI, oxygen delivery index (DO(2)I), and mixed venous oxygen saturation (SvO(2), each P < 0.05). Dobutamine infusion was followed by a dose-dependent increase in CI, DO(2)I, and SvO(2) in both health and endotoxemia (each P < 0.05). Although the higher dosage of dobutamine exerted favorable effects, such as a decrease in pulmonary vascular resistance index (P < 0.05), the associated onset of tachycardia (P < 0.05) and arterial hypotension (P < 0.05) may limit its therapeutic use under septic conditions. This study provides evidence that dobutamine in a dosage of 2 microg x kg(1) x min(1) is useful to reverse the terlipressin-linked depressions in CI, DO(2)I and SvO(2) in ovine endotoxemia without obvious side effects.

Hemodynamic effects of titrated norepinephrine in healthy versus endotoxemic sheep

In patients with sepsis and systemic inflammatory response syndrome, hemodynamic support is often complicated by a vascular hyporesponsiveness to exogenously administered norepinephrine. Although norepinephrine tachyphylaxis represents a significant clinical problem, the relationship between norepinephrine dosages and mean arterial pressure (MAP) in the presence of systemic inflammation is still not fully understood. This study was, therefore, designed as a prospective, controlled laboratory trial to elucidate the hemodynamic response to incremental norepinephrine doses in healthy and endotoxemic sheep. ANOVA demonstrated that a significantly higher mean infusion rate of norepinephrine was needed to increase MAP by 20 mmHg in endotoxemic versus healthy control sheep (P = 0.007). Whereas the goal-MAP was reached in 100% of healthy controls, it was achieved in only 80% during endotoxemia. Cardiac index increased significantly in healthy, but not in endotoxemic, sheep. Our findings confirm the presence of vascular hyporesponsiveness to norepinephrine in endotoxemia. In addition, this study demonstrates that the presence of systemic inflammation leads to an early hyporesponsiveness against norepinephrine which was caused by a drug-independent mechanism rather than a tachyphylaxis due to long-term administration of norepinephrine.

Short-time effects of glipizide, an ATP-sensitive potassium channel inhibitor, on cardiopulmonary hemodynamics and global oxygen transport in healthy and endotoxemic sheep

Short-time effects of glipizide, an ATP-sensitive potassium channel inhibitor, on cardiopulmonary hemodynamics and global oxygen transport in healthy and endotoxemic sheep