Milrinone improves intestinal villus blood flow during endotoxemia

PURPOSE: To determine whether the compromised intestinal villus blood flow in a rat model of endotoxemia could be improved by continuous infusion of the phosphodiesterase (PDE) inhibitor milrinone. METHODS: Twenty-four anesthetized and ventilated rats were laparotomized and an ileal portion was exteriorized and opened by an antimesenteric incision. The ileal segment was fixed with the mucosal surface upward. Microcirculatory parameters were assessed by intravital videomicroscopy. The animals were randomly assigned to receive one of three treatments: infusion of Escherichia coli lipopolysaccharides without phosphodiesterase inhibitor pretreatment (=LPS group); or infusion of LPS with milrinone pretreatment (= milrinone group), or without infusion of LPS or milrinone (=control group). Macrohemodynamic parameters (MAP, HR) and microhemodynamic parameters of ileal mucosa (mean diameter of central arterioles = D(A) and mean erythrocyte velocity within the arterioles= V(E)) were measured 30 min before and at 0, 60, and 120 min after induction of endotoxemia. Mucosal villus blood flow was calculated from D(A) and V(E). RESULTS: In the milrinone group MAP decreased 60 min after induction of endotoxemia whereas it remained stable in the control and the LPS group. In both groups given endotoxin V(E) decreased after start of LPS infusion. In contrast, D(A) decreased in the LPS group, but increased in the milrinone group after 120 min of endotoxemia. Thus, the endotoxin-induced decrease of intestinal villus blood flow was diminished but not fully restored by milrinone infusion. CONCLUSION: Our results indicate that milrinone has some beneficial microcirculatory effects during endotoxemia. Although it contributed to systemic hypotension, it attenuated intestinal mucosal hypoperfusion.     

A Comparison of Epinephrine Only, Arginine Vasopressin Only, and Epinephrine Followed by Arginine Vasopressin on the Survival Rate in a Rat Model of Anaphylactic Shock

Background: Epinephrine and more recently arginine vasopressin (AVP) alone or in combination have been proposed in patients with anaphylactic shock, but few experimental data exist. The authors investigated the effects of epinephrine only, AVP only, or epinephrine followed by AVP in a model of anaphylactic shock.

Methods: Ovalbumin-sensitized Brown Norway rats were anesthetized, intubated, and shock induced with ovalbumin. Rats (n = 6/group) were randomly allocated to receive 5 min after shock onset: (1) saline (no-treatment group); (2) two boluses of epinephrine followed by continuous infusion (epinephrine group); (3) AVP bolus followed by continuous infusion (AVP group); (4) epinephrine bolus followed by AVP continuous infusion (epinephrine + AVP group). Mean arterial pressure (MAP) and skeletal muscle oxygen pressure (Ptio2) were measured. Continuous infusion rates were titrated to reach MAP values of 60 mmHg. Survival was analyzed.

Results: Without treatment, MAP and Ptio2 decreased rapidly with 0% survival. In the epinephrine group, MAP and Ptio2 recovered after an initial decrease, with 84% survival. In the AVP group, MAP was partially restored and subsequently decreased; Ptio2 values decreased to values similar to those in the no-treatment group; survival was 0%. In the epinephrine + AVP group, MAP and Ptio2 values increased more slowly as compared with the epinephrine group; survival was 100%.     

Effect of endotoxemia on hepatic portal and sinusoidal blood flow in rats

A decrease in liver blood flow leads to dysfunction of hepatocytes and Kupffer cells, with subsequent local and systemic liberation of proinflammatory mediators that may maintain systemic inflammatory response syndrome (SIRS) and may lead to multiple organ dysfunction syndrome (MODS). There is only limited knowledge on the hepatic micro- and macrocirculation during sepsis or endotoxemia. Therefore, the aim of our study was to investigate alterations in hepatic portal blood flow (PBF) and sinusoidal blood flow (SBF) during endotoxemia. In male Wistar rats endotoxemia was induced by continuous infusion of 2 mg/kg/h lipopolysaccharides from Escherichia coli 026:B6 immediately after baseline measurements (n = 8). The control group (n = 8) received an equivalent volume of Ringer's solution. Mean arterial pressure (MAP), heart rate (HR), cardiac output (CO), PBF, and SBF were measured at baseline and 60 and 120 min after induction of endotoxemia. PBF was measured using an ultrasonic flow probe that was positioned around the portal vein. SBF was detected by in vivo videomicroscopy of the left liver lobe. In the LPS group MAP decreased, but CO remained at baseline values. During endotoxemia PBF decreased significantly from 23 +/- 3 to 15 +/- 4 mL/min (60 min) and 16 +/- 3 mL/min (120 min). SBF also significantly decreased to 68.5% (60 min) and 57.1% (120 min) of baseline value. Our results demonstrate that during early endotoxemia hepatic macro- and microcirculatory perfusion is significantly decreased despite unchanged CO. This early reduction of hepatic perfusion might be caused by an increased hepatic vessel resistance as a consequence of liberation of vasoconstrictive mediators or/and by a decrease in intestinal perfusion.     

Dose-related cardiovascular effects of amrinone during enflurane anesthesia in the dog

The dose-related cardiovascular effects of amrinone, a synthetic cardiotonic and vasodilating drug, were investigated in dogs anesthetized with enflurane (2.2-2.4% end-tidal concentration). Twelve mongrel dogs were divided into two groups of six animals: an enflurane group (E) that received only enflurane, and an amrinone group (A). In the latter group each dog received the following sequential boluses and 30-min infusions: 1) the amrinone solvent alone; 2) amrinone, 1 mg/kg + 5 micrograms X kg-1 X min-1; 3) amrinone, 2 mg/kg + 10 micrograms X kg-1 X min-1; 4) amrinone, 4 mg/kg + 20 micrograms X kg-1 X min-1. Over the course of the experiment, 2.2-2.4% end-tidal enflurane alone resulted in a gradual decrease in cardiac index (CI), stroke volume index (SVI), and the maximum left ventricular dP/dt (LV dP/dtmax), without changes in heart rate (HR), mean arterial pressure (MAP), central venous pressure (CVP), or pulmonary capillary wedge pressure (PCWP) in group E. Significant differences from group E after 30 min of the lowest dose of amrinone included higher CI and SVI with lower systemic vascular resistance (SVR). The medium dose of amrinone, in addition to the effects already observed with the lowest dose of amrinone, decreased MAP and pulmonary vascular resistance (PVR), and increased LV dP/dtmax, when compared to group E only. Furthermore, the highest dose of amrinone caused lower pulmonary artery mean pressure (PAM), PCWP, and higher HR with shortened PR interval. The differences in MAP, CI, LV dP/dtmax, PCWP, PAM, PR interval, SVR, and PVR compared to E were still significant 30 min after the cessation of the highest dose. This study shows that the myocardial depressant effects of enflurane in an unstimulated canine model with a previously healthy heart can be overcome in a dose-related manner by amrinone. In contrast to other vasodilators, no reflex increase in plasma catecholamines was seen.(ABSTRACT TRUNCATED AT 250 WORDS)     

瑞芬太尼对兔内毒素性急性肺损伤的影响

目的 探讨瑞芬太尼对兔内毒素性急性肺损伤(Au)的影响.方法 健康成年雄性新西兰大白兔30只,体重2.5～3.5 kg,随机分为5组(n=6):对照组(C组)、ALI组、低剂量瑞芬太尼组(LR组)、中剂量瑞芬太尼组(MR组)和高剂量瑞芬太尼组(HR组).C组经30 min静脉输注生理盐水10 ml;ALI组经30 min静脉输注大肠杆菌内毒索(LPS)0.5 mG/kg;LR组、MR组和HR组分别静脉输注瑞芬太尼0.2、0.4和0.8μg·kg~(-1)·min~(-1)至处死,输注15 min时开始给予LPS,方法同ALI组.于LPS输注前即刻(T_0)、输注结束后1、2.5、5.5 h时记录平均动脉血压(MAP)、心率(HR)和气道峰压(P_(peak),测定动脉血氧分压(PaO_2)和血浆细胞间粘附分子1(ICAM-1)浓度,称量肺组织湿重(W)和干重(D),计算W/D比,并在光镜和电镜下观察肺组织病理学结果.结果 与C组比较,ALI组MAP、HR和PaO_2,降低,W/D比、P_(peak)和血浆ICAM-1浓度升高(P<0.05);与ALI组比较,LR组、MR组和HR组MAP、HR 升高,肺组织W/D比降低,P(peak)和血浆ICAM-1浓度降低,PaO_2升高(P<0.05);与LR组比较,MR组和HR组MAP、HR、P(peak)、血浆ICAM-1浓度和肺组织W/D比降低,PaO_2升高(P<0.05);与MR组比较,HR组注肺组织W/D比降低,PaO_2升高(P<0.05).LR组、MR组和HR组肺组织病理学损伤较ALI组减轻.结论 瑞芬太尼可减轻兔内毒素性急性肺损伤,且呈剂量依赖性,其机制可能与抑制ICAM-1的表达有关.     

The influence of hyperoxic ventilation during sodium nitroprusside-induced hypotension on skeletal muscle tissue oxygen tension

BACKGROUND: Increasing inspired oxygen concentrations might provide a simple and effective intervention to increase oxygen tension in tissues during controlled hypotension. To test this hypothesis, the influence of hyperoxic ventilation (100% O2) on skeletal muscle oxygen partial pressure (Ptio2) in patients receiving sodium nitroprusside-induced controlled hypotension was studied. METHODS: Forty-two patients undergoing radical prostatectomy were prospectively studied and randomly divided into three groups as follows: (1) Controlled hypotension induced by sodium nitroprusside (mean arterial blood pressure, 50 mmHg) and hyperoxic ventilation (CH-100%; n = 14); (2) controlled hypotension and ventilation with 50% O2 in nitrous oxide (CH-50%; n = 14); and (3) standard normotensive anesthesia with 50% O2 in nitrous oxide (control; n = 14). Ptio2 values were measured continuously in all patients using implantable polarographic microprobes. Arterial blood gases and lactate concentrations were analyzed in 30-min intervals. RESULTS: Surgical blood loss and transfusion requirements were significantly reduced in both groups receiving hypotensive anesthesia. During surgery, arterial partial pressure of oxy-gen and arterial oxygen content were significantly higher in patients of the CH-100% group. Baseline values of Ptio2 were comparable between the groups (CH-50%: 25.0 +/- 0.7 mmHg; CH-100%: 25.2 +/- 0.2 mmHg; control: 24.5 +/- 0.2 mmHg). After a transient increase in Ptio2 in the CH-100% group during normotension, Ptio2 values returned to baseline and remained unchanged in the control group. Ptio2 decreased significantly during the hypotensive period in the CH-50% group. The lowest mean Ptio2 values were 15.0 +/- 4.1 mmHg in the CH-50% group, 24.2 +/- 4.9 mmHg in the CH-100% group, and 23.5 +/- 3.8 mmHg in the control group. There were no significant changes in lactate plasma concentrations in any group throughout the study period. CONCLUSIONS: Hyperoxic ventilation improved skeletal muscle tissue oxygenation during sodium nitroprusside-induced hypotension. This improved local tissue oxygenation seems to be most likely due to an increase in convective oxygen transport and the attenuation of hyperoxemia-induced arteriolar vasoconstriction by sodium nitroprusside.     

Anaphylactic shock: a form of distributive shock without inhibition of oxygen consumption

BACKGROUND: The pathophysiology of anaphylactic shock during anesthesia is incompletely characterized. It is described as distributive by analogy with septic shock (anaerobic metabolism, high tissue oxygen pressure [Ptio2] values). The Ptio2 profile and its metabolic consequences during anaphylaxis are not known. METHODS: Ovalbumin-sensitized anaphylactic shock rats (n = 11) were compared to nicardipine-induced hypotension rats (n = 12) for systemic hemodynamics, Ptio2, sympathetic nervous system activation, skeletal muscle blood flow, and interstitial lactate and pyruvate concentrations using combined microdialysis and polarographic Clark-type oxygen probes. RESULTS: In both groups, the time course and the magnitude of arterial hypotension were similar. The ovalbumin group but not the nicardipine group displayed decreased skeletal muscle blood flow (from 45 +/- 6.2 ml x 100 g(-1) x min(-1) to 24.3 +/- 5 ml x 100 g(-1) x min(-1); P < 0.0001) and Ptio2 values (from 42 +/- 5 to 5 +/- 2; P < 0.0001). The ovalbumin group had more intense sympathetic nervous system activation with higher plasma epinephrine and interstitial norepinephrine concentrations. For the ovalbumin group, there was skeletal muscle anaerobic metabolism (lactate concentration increased from 0.446 +/- 0.105 to 1.741 +/- 0.459 mm; P < 0.05) and substrate depletion (pyruvate concentration decreased from 0.034 +/- 0.01 mm to 0.006 +/- 0.002 mm; P < 0.05) leading to increased interstitial lactate/pyruvate ratios (from 17 +/- 6 to 311 +/- 115; P < 0.05). CONCLUSIONS: This profile suggests decreased skeletal muscle blood flow and oxygen delivery. Persistent energy consumption results in decreased Ptio2 and substrate depletion through anaerobic glycolysis leading to complete failure of cellular energy production. This could explain rapid organ dysfunction and resuscitation difficulties.     

A comparison of epinephrine only, arginine vasopressin only, and epinephrine followed by arginine vasopressin on the survival rate in a rat model of anaphylactic shock

BACKGROUND: Epinephrine and more recently arginine vasopressin (AVP) alone or in combination have been proposed in patients with anaphylactic shock, but few experimental data exist. The authors investigated the effects of epinephrine only, AVP only, or epinephrine followed by AVP in a model of anaphylactic shock. METHODS: Ovalbumin-sensitized Brown Norway rats were anesthetized, intubated, and shock induced with ovalbumin. Rats (n = 6/group) were randomly allocated to receive 5 min after shock onset: (1) saline (no-treatment group); (2) two boluses of epinephrine followed by continuous infusion (epinephrine group); (3) AVP bolus followed by continuous infusion (AVP group); (4) epinephrine bolus followed by AVP continuous infusion (epinephrine + AVP group). Mean arterial pressure (MAP) and skeletal muscle oxygen pressure (PtiO2) were measured. Continuous infusion rates were titrated to reach MAP values of 60 mmHg. Survival was analyzed. RESULTS: Without treatment, MAP and PtiO2 decreased rapidly with 0% survival. In the epinephrine group, MAP and PtiO2 recovered after an initial decrease, with 84% survival. In the AVP group, MAP was partially restored and subsequently decreased; PtiO2 values decreased to values similar to those in the no-treatment group; survival was 0%. In the epinephrine + AVP group, MAP and PtiO2 values increased more slowly as compared with the epinephrine group; survival was 100%. CONCLUSIONS: In this model of anaphylactic shock, early treatment with epinephrine followed by continuous epinephrine or vasopressin infusion resulted in an excellent survival rate, whereas vasopressin only resulted in a 100% death rate. These experimental results suggest that epinephrine must still be considered as the first-line drug to treat anaphylactic shock.     

The Effect of Aminoguanidine on Blood and Tissue Lipid Peroxidation in Jaundiced Rats With Endotoxemia Induced With LPS

Obstructive jaundice (OJ) is a severe condition that leads to several complications. One of the important problems in OJ is the increased incidence of endotoxemia, which is the result of bacterial translocation (BT) and defective host immune response. Lipid peroxidation (LP) is an important problem in OJ and sepsis in which nitric oxide (NO) production and inducible nitric oxide synthase (iNOS) activity are increased and antioxidative activity is decreased. Formation of peroxynitrite (ONOO^?) anion leads to cellular damage and apoptosis. In this experimental study, we explore the effect of specific iNOS inhibitor aminoguanidine (AG) on blood and tissue (liver and renal) LP and iNOS levels in jaundiced rats with endotoxemia induced with lipopolysaccharide (LPS). Rats were randomized into six groups; group A, sham; group B, obstructive jaundice (OJ); group C, OJ + LPS; group D, OJ + AG; group E, OJ + LPS + AG; group F, OJ + AG + LPS. Serum malondialdehyde (MDA) and serum myeloperoxidase (MPO) activity and liver and renal tissue MDA, MPO, and Na⁺/K⁺-ATPase activity levels were detected in biochemical methods. Liver and renal tissue iNOS levels were examined immunohistopathologically. Serum and tissue MDA and MPO levels and tissue iNOS expression were increased significantly in groups B, C, and E, while tissue ATPase levels were decreased significantly in the same groups. In the group treated with AG (group D), serum and tissue MDA and MPO levels and tissue iNOS expression were decreased while tissue ATPase levels were increased significantly. In group F, if AG was administrated before LPS, we observed that serum and tissue MDA and MPO levels and tissue iNOS expression were decreased while tissue ATPase levels were increased significantly. Thus, our study showed that AG had a protective effect when it was administrated before LPS, but it failed to prevent tissue iNOS expression and LP if there was established endotoxemia in OJ.     

The Influence of Hyperoxic Ventilation during Sodium Nitroprusside-induced Hypotension on Skeletal Muscle Tissue Oxygen Tension

Background: Increasing inspired oxygen concentrations might provide a simple and effective intervention to increase oxygen tension in tissues during controlled hypotension. To test this hypothesis, the influence of hyperoxic ventilation (100% O2) on skeletal muscle oxygen partial pressure (Ptio2) in patients receiving sodium nitroprusside-induced controlled hypotension was studied.

Methods: Forty-two patients undergoing radical prostatectomy were prospectively studied and randomly divided into three groups as follows: (1) Controlled hypotension induced by sodium nitroprusside (mean arterial blood pressure, 50 mmHg) and hyperoxic ventilation (CH-100%; n = 14); (2) controlled hypotension and ventilation with 50% O2 in nitrous oxide (CH-50%; n = 14); and (3) standard normotensive anesthesia with 50% O2 in nitrous oxide (control; n = 14). Ptio2 values were measured continuously in all patients using implantable polarographic microprobes. Arterial blood gases and lactate concentrations were analyzed in 30-min intervals.

Results: Surgical blood loss and transfusion requirements were significantly reduced in both groups receiving hypotensive anesthesia. During surgery, arterial partial pressure of oxy-gen and arterial oxygen content were significantly higher in patients of the CH-100% group. Baseline values of Ptio2 were comparable between the groups (CH-50%: 25.0 +/- 0.7 mmHg; CH-100%: 25.2 +/- 0.2 mmHg; control: 24.5 +/- 0.2 mmHg). After a transient increase in Ptio2 in the CH-100% group during normotension, Ptio2 values returned to baseline and remained unchanged in the control group. Ptio2 decreased significantly during the hypotensive period in the CH-50% group. The lowest mean Ptio2 values were 15.0 +/- 4.1 mmHg in the CH-50% group, 24.2 +/- 4.9 mmHg in the CH-100% group, and 23.5 +/- 3.8 mmHg in the control group. There were no significant changes in lactate plasma concentrations in any group throughout the study period.     

The effect of aminoguanidine on blood and tissue lipid peroxidation in jaundiced rats with endotoxemia induced with LPS.

Obstructive jaundice (OJ) is a severe condition that leads to several complications. One of the important problems in OJ is the increased incidence of endotoxemia, which is the result of bacterial translocation (BT) and defective host immune response. Lipid peroxidation (LP) is an important problem in OJ and sepsis in which nitric oxide (NO) production and inducible nitric oxide synthase (iNOS) activity are increased and antioxidative activity is decreased. Formation of peroxynitrite (ONOO(-)) anion leads to cellular damage and apoptosis. In this experimental study, we explore the effect of specific iNOS inhibitor aminoguanidine (AG) on blood and tissue (liver and renal) LP and iNOS levels in jaundiced rats with endotoxemia induced with lipopolysaccharide (LPS). Rats were randomized into six groups; group A, sham; group B, obstructive jaundice (OJ); group C, OJ + LPS; group D, OJ + AG; group E, OJ + LPS + AG; group F, OJ + AG + LPS. Serum malondialdehyde (MDA) and serum myeloperoxidase (MPO) activity and liver and renal tissue MDA, MPO, and Na(+)/K(+)-ATPase activity levels were detected in biochemical methods. Liver and renal tissue iNOS levels were examined immunohistopathologically. Serum and tissue MDA and MPO levels and tissue iNOS expression were increased significantly in groups B, C, and E, while tissue ATPase levels were decreased significantly in the same groups. In the group treated with AG (group D), serum and tissue MDA and MPO levels and tissue iNOS expression were decreased while tissue ATPase levels were increased significantly. In group F, if AG was administrated before LPS, we observed that serum and tissue MDA and MPO levels and tissue iNOS expression were decreased while tissue ATPase levels were increased significantly. Thus, our study showed that AG had a protective effect when it was administrated before LPS, but it failed to prevent tissue iNOS expression and LP if there was established endotoxemia in OJ.     

Oxygen extraction in pigs subjected to low-dose infusion of endotoxin after major abdominal surgery

BACKGROUND: Sepsis may impair O(2) extraction due to blood flow redistribution or decreased utilization of the available oxygen. METHODS: We assessed the effect of endotoxemia on systemic and regional O(2) extraction and lactate handling in pigs, randomized to receive either endotoxin (0.4 microg kg(-1) h(-1); n = 10) or saline infusion (controls; n = 9) for 12 h. RESULTS: High baseline regional and systemic O(2) extraction in the endotoxin group (median 56%, range 45-77%) and in the controls (67%, 49-72%) was maintained until the end of the experiment (endotoxin group: 60%, 50-71%; controls: 60%, 50-74%) despite hypotension and a decrease in stroke volume in endotoxic animals. Hepatic lactate exchange decreased during endotoxemia from 14 micromol kg(-1) min(-1) (range 10-28 micromol kg(-1) min(-1)) to 10 (range 3-15) micromol kg(-1) min(-1); P < 0.01), but remained stable in the controls, with 13 micromol min(-1) (4-18 micromol min(-1)) at baseline and 7 micromol min(-1) (3-17 micromol min(-1)) after 12 h of saline infusion. CONCLUSIONS: The high and sustained oxygen consumption and oxygen extraction in this endotoxemic model speak against any major impairment of hepatosplanchnic or systemic oxygen extraction and oxidative metabolism. The reduced hepatic lactate exchange despite an unchanged hepatic lactate influx suggests altered metabolic activities independent of oxygen consumption.     

Influence of Lidocaine on Endotoxin-induced Leukocyte-Endothelial Cell Adhesion and Macromolecular Leakage in Vivo

Background: Endotoxin activates leukocyte-endothelial cell adhesion, vascular leakage, and changes in vascular microhemodynamics. The aim of this study was to determine whether lidocaine, which inhibits the activation of leukocytes, could attenuate microcirculatory disturbances during endotoxemia.

Methods: Thirty anesthetized male rats were randomly assigned to receive one of three treatments (n = 10 for each group): infusion of saline (control group), infusion of Escherichia coli endotoxin (LPS group: 2 mg [center dot] kg sup -1 [center dot] h sup -1 lipopolysaccharides) without lidocaine treatment, or infusion of endotoxin with lidocaine pretreatment 30 min before baseline measurements (lidocaine group: intravenous bolus of 2 mg/kg and continuous infusion of 2 mg [center dot] kg sup -1 [center dot] h sup -1). Leukocyte adherence, erythrocyte velocity (VRBC), and vessel diameters (Dv) were determined at baseline and at 60 and 120 min in mesenteric post-capillary venules using in vivo videomicroscopy. Macromolecular leakage was determined by measuring the extravasation of fluorescence-labeled albumin. Venular wall shear rate (tau) was calculated according to the equation tau = 8 [center dot] VRBC [center dot] Dv sup -1.

Results: Lidocaine significantly attenuated the increase of leukocyte adherence during endotoxemia. There were no significant differences of tau within or between the groups. Macro-molecular leakage exhibited the greatest increase in the LPS group. In the lidocaine group, it was significantly decreased but still increased compared with the control group.     

入肝血流阻断和全肝血流阻断对肝组织氧压影响

目的 研究兔常温下入肝血流阻断（portal triad clamp,PTC)及全肝血流阻断（total hepatic vascular exclusion,THVE)对肝组织氧压（tissue oxygen pressure,Ptio2)的影响。方法 24只兔均分二组即PTC和THVE组。分别测定二组缺血前、缺血30min及再灌注30min后肝Ptio2值及血清丙氨酸氨基转氨酶（ALT）值变化。结果 PTC和THVE组均表现为肝Ptio2下降，但THVE较PTC组肝Ptio2值下降更显著（P＜0．01）、血清ALT值也明显升高（P＜0．05）。结论 PTC组较THVE组对肝缺血的耐受性增加。     

Systematic evaluation of nitric oxide, tetrahydrobiopterin, and anandamide levels in a porcine model of endotoxemia

PURPOSE: Using a lipopolysaccharide (LPS)-treated porcine model, we examined: (1) whether nitric oxide (NO), anandamide, and tetrahydrobiopterin (BH4) increased or not in early endotoxic shock; and (2) the location of the major site of production of these molecules, by comparing their concentrations in arteries and the portal and hepatic veins. METHODS: Ten pigs received an infusion of LPS at 1.7 microg x kg(-1)x h(-1) via the portal vein for 240 min. Consecutive changes in systemic hemodynamics, hepatosplanchnic circulation, and oxygen delivery were measured. Furthermore, the variable changes in the concentrations of nitrite and nitrate (NOx), anandamide, and BH4 were measured. To access the effects of surgery, anesthesia, and fluid management on BH4, an experiment without LPS infusion was performed in two other animals. RESULTS: Mean arterial pressure and cardiac index started to decrease at 60 min after LPS infusion. However, systemic vascular resistance remained unchanged. Total hepatic blood flow and hepatic oxygen delivery also decreased significantly. NOx and anandamide did not change during LPS infusion. BH4 values did not change without LPS infusion. However, BH4 values increased significantly in the arterial, portal, and hepatic circulation during LPS infusion, especially in the hepatic vein (from 136.8 +/- 27.5 to 281.3 +/- 123.2 mol/ml; P < 0.01). CONCLUSION: Our data suggest that the BH4 values were significantly increased in several organs, especially in the liver during endotoxic shock. Impaired cardiac output and decreased blood pressure appeared in the early phase of porcine endotoxemia. Longer-term observation of these parameters after LPS treatment should be performed as the next step in future studies.     

Effect of N-acetylcysteine on blood and tissue lipid peroxidation in lipopolysaccharide-induced obstructive jaundice.

In obstructive jaundice, free radical production is increased and antioxidative activity is reduced. N-Acetylcysteine (NAC) has a beneficial effect with anti-inflammatory and antioxidant activity, acting as a free radical scavenger. NAC inhibits inducible nitric oxide synthase, suppresses cytokine expression/release, and inhibits adhesion molecule expression and nuclear factor kappa B. The aim of this study was to investigate the effects of NAC on liver/renal tissue and serum lipid peroxidation in lipopolysaccharide (LPS)-induced obstructive jaundice. We randomized 60 rats into 6 groups: group 1, Sham; group 2, obstructive jaundice (OJ) induced after bile-duct ligation; group 3, OJ + NAC (100 mg kg- 1 subcutaneously); group 4, OJ + LPS (10 mg kg-1); group 5, OJ + NAC + LPS; and group 6, OJ + LPS + NAC. For each group, the biochemical markers of lipid peroxidation and the antioxidant products were measured in serum and liver/renal tissue after sacrifice. Almost all lipid peroxidation products levels were increased and antioxidant products levels were decreased in groups who received LPS (groups 4, 5, and 6), but the effect was less remarkable when NAC was administered before LPS (group 5). The same trend was seen for groups with OJ +/- LPS who did not received NAC or received it after induced toxemia (groups 2, 4, and 6) as compared to groups 1 and 3. Moreover, in the case of OJ + LPS, rats treated with NAC before LPS (group 5) had lower lipid peroxidation products levels and higher antioxidant products levels as compared to those who did not received NAC (group 4). This phenomenon was not reproducible with NAC administered after LPS (group 6). Thus, results of this study showed that NAC prevents the deleterious effects of LPS in obstructive jaundice by reducing lipid peroxidation in serum and liver/renal tissue if administered before LPS. Nonetheless, NAC failed to prevent the lipid peroxidation in the case of established endotoxemia in obstructive jaundice.     

小容量不同液体治疗对内毒素血症大鼠肾血流的影响

目的 评价小容量不同液体治疗对内毒素血症大鼠肾血流的影响.方法 清洁级雄性SD大鼠30只,体重180～250 g,随机分为5组(n=6):对照组(C组)、内毒素血症组(LPS组)、7.5%高渗氯化钠溶液组(HS组)、羟乙基淀粉130/0.4溶液组(HES组)和高渗氯化钠羟乙基淀粉40溶液组(HSH组).LPS组、HS组、HES组和HSH组经左侧颈总动脉导管注射LPS 1 mg/kg,C组注射等容量生理盐水.30 min后,C组和LPS组注射生理盐水4 ml/kg;HS组、HES组和HSH组分别注射7.5%高渗氯化钠溶液、羟乙基淀粉130/0.4溶液或高渗氯化钠羟乙基淀粉40溶液4 ml/kg.于给予LPS前、给予LPS后30 min、液体治疗后10、30、60 min时进行左肾脏超声多普勒检测,记录左肾动脉的收缩峰值血流速度(Vmax)、舒张末期血流速度(Vmax)和阻力指数(RI).取肾组织,观察病理学结果.结果 内毒素血症大鼠肾血流逐渐减弱,分布面积减小,肾皮质血流几乎消失,肾小管上皮细胞严重变性、崩解脱落、集合管内可见细胞碎片充塞,左肾段动脉Vmax和Vmin降低,RI升高(P＜0.01).与LPS组比较,HS组、HES组和HSH肾血流增强,Vmax和Vmin升高,RI降低,其中HSH组效果更佳(P＜0.01).结论 小容量羟乙基淀粉130/0.4溶液、高渗盐水和高渗氯化钠羟乙基淀粉40溶液治疗可增强内毒素血症大鼠肾血流,改善肾脏微循环;高渗氯化钠羟乙基淀粉40溶液效果更佳.     

羟乙基淀粉对内毒素血症大鼠肠系膜细静脉白细胞活化和血管通透性的影响

目的 探讨羟乙基淀粉(HES 130/0.4)对内毒素血症早期大鼠肠系膜细静脉白细胞活化及血管通透性的影响.方法 雄性Wistar大鼠36只,体重200～250 g,随机分为3组(n=12):对照组(C组)静脉注射生理盐水0.5 ml后,静脉输注生理盐水16 ml·kg-1·h-1;内毒素组(LPS组)静脉注射LPS 2 mg/ks(溶于生理盐水0.5 ml)后,静脉输注生理盐水16 ml·kg-1·h-1;HES组静脉注射LPS 2ms/kg(溶于生理盐水0.5 ml)后,静脉输注HES 16 ml·kg-1·h-1.各组补液时间60 min.观察给药前及补液期间和补液后30 min内肠系膜细静脉白细胞滚动数、粘附数、游出数、肥大细胞脱颗粒情况及细静脉血管通透性情况,检测外周血白细胞粘附分子CD11b和CD18的表达.结果 与C组比较,LPS组沿肠系膜细静脉内滚动、粘附和游出的白细胞增加,肥大细胞脱颗粒率增加,LPS组和HES组CD11b、CD18表达上调,细静脉血管通透性增加(P＜0.05).与LPS组比较,HES组上述指标均降低(P＜0.05).结论 HES 130/0.4可抑制内毒素血症早期大鼠肠系膜细静脉白细胞沿血管壁滚动、粘附和游出,抑制肥大细胞脱颗粒及血管通透性的增加,从而改善微循环障碍.     

Amrinone reverses bupivacaine-induced regional myocardial dysfunction

Amrinone has been shown to have therapeutic effects on bupivacaine-induced cardiovascular toxicity, but its exact effects on the heart are not well understood.
This study evaluated the regional myocardial effect of amrinone on bupivacaine-induced cardiovascular toxicity in in situ beating hearts in 10 dogs using a selective coronary perfusion and sono-micrometry. In the control group, bupivacaine was administered into the left anterior descending coronary artery (LAD) for 15 min at tour steps: baseline, step 1, step 2 and step 3, (calculated LAD plasma concentrations; 0, 5, 5 and 10 μg·ml^-1, respectively). In the amrinone group, amrinone (5 μg·ml^-1) was simultaneously infused at steps 2 and 3 in addition to bupivacaine infusions. Regional myocardial function of the LAD supplied area was evaluated by analysis of the left ventricular pressure-segment length loop.
In the control group, systolic shortening decreased from the baseline (10.5±1.3%, mean ± SEM) to step 3 (0.1±1.3%), and post-systolic shortening increased from the baseline (18.0±3.7%) to step 3 (52.3±5.5%) dose-dependently. In contrast, with amrinone infusion at steps 2 and 3, both variables returned to near baseline values.
These results indicate that amrinone reverses bupivacaine-induced regional myocardial dysfunction.     

Effects of continuous nitroglycerin infusion on acute myocardial ischemia in dogs

The effects of a continuous infusion of nitroglycerin (NTG) were evaluated by hemodynamic measurements and measurements of regional myocardial blood flow (RMBF) in dogs on right heart bypass with left anterior descending coronary artery ligation. NTG infusion which decreased afterload, mean aortic pressure (MAP) decreased from 100 to 85 mm Hg, thus also decreasing coronary perfusion pressure) resulted in an 11.8% increase in total coronary blood flow (CBF), a 19.1% decrease in coronary vascular resistance index (CVRI), and a 21.7% decrease in myocardial oxygen consumption (MV?O₂). When MAP was returned to the control level (100 mm Hg) with continuing infusion of NTG, CBF increased 49.1%, and CVRI decreased by 23.4% compared to the pre-NTG ischemic state. Regional myocardial blood flow (microsphere technique) to ischemic tissue at the border of the infarct remained stable with NTG infusion despite decreased MAP, in contrast to the significant fall in RMBF in this region with decreased MAP in the control group without NTG. When MAP was elevated back to pre-NTG levels, an 18.6% increase in RMBF to the border of the infarct was seen compared to an insignificant change in RMBF in untreated (control) animals. These data are consistent with the concept that under conditions of regional myocardial ischemia, coronary blood flow to the “border zone” (ischemic myocardium) is maintained or enhanced by NTG, even when coronary perfusion pressure is modestly reduced.