K. van Ackern

Lack of Dependence of Cerebral Blood Flow on Blood Viscosity after Blood Exchange with a Newtonian O2 Carrier

Whether the increase in cerebral blood flow measured after hemodilution is mediated by a decrease in blood viscosity or in oxygen delivery to the brain is debated. In the present study, blood was replaced by an oxygen-carrying blood substitute, ultrapurified, polymerized, bovine hemoglobin (UPBHB). In contrast to normal blood, UPBHB yields a constant and defined viscosity in the brain circulation, since its viscosity is not dependent on the shear rate. CBF was determined after blood exchange with UPBHB in one group of conscious rats (UPBHB group) and in another group of blood-exchanged conscious rats in which viscosity was increased fourfold by the addition of 2% polyvinylpyrrolidone (PVP), mw 750,000 (UPBHB-PVP group). Local CBF (LCBF) was measured in 34 brain structures by means of the quantitative iodo(14C)antipyrine method. After blood replacement, systemic parameters such as cardiac index, arterial blood pressure, blood gases, and acid-base status were not different between the UPBHB and the UPBHB-PVP groups. In particular, arterial oxygen content was similar in both groups. Compared with a control group without blood exchange, LCBF was increased after blood exchange in the different brain structures by 60–102% (UPBHB group) and by 33–101% (UPBHB-PVP group). Mean CBF was increased by 77% in the UPBHB group and by 69% in the UPBHB-PVP group. No significant differences were observed in the values of LCBF or mean CBF between the UPBHB group and the UPBHB-PVP group. The results show that a fourfold variation in the viscosity of a Newtonian blood substitute does not result in differences in CBF values. It is concluded that blood viscosity is less important to CBF than hitherto postulated.

Alterations of bacterial clearance induced by propofol

Background: The purpose of the study was to investigate the potential influence of the anaesthetic agent propofol on immune function in terms of systemic clearance and organ distribution of injected Escherichia coli in a rabbit model.

Effects of N-acetylcysteine on bacterial clearance

Abstract. The aim of this study was to investigate whether the oxygen radical scavenger N‐acetylcysteine (N‐AC) impairs bacterial clearance, thus predisposing the host to increased risk of disease. Blood clearance of Escherichia coli and organ colonization were investigated in anaesthetized rabbits after pretreatment with N‐AC (250 mg kg‐1 body weight, n= 16) and in sham‐operated animals (n= 12). To enable quantification of the clearance process, defined numbers of exogenous E. coli [1.3 times 108 colony‐forming units (CFUs)] were injected intravenously. Parameters monitored were kinetics of bacterial elimination from the blood, and polymorphonuclear leucocyte (PMN) oxidative burst activity. Samples of liver, kidney, spleen and lung were collected for bacterial counts. Compared with controls, pretreatment with N‐AC resulted in delayed bacterial elimination from blood and higher organ colonization with increased numbers of E. coli in liver, lung and kidney (P < 0.05). N‐AC treatment was associated with a suppressed PMN oxidative burst activity. Impaired bacterial clearance and enhanced organ colonization in N‐AC‐treated animals correlated with reduced oxidative burst activity, suggesting impaired granulocyte‐dependent bacterial killing due to N‐AC application.

Heterogeneity in lipopolysaccharide responsiveness of endothelial cells identified by gene expression profiling: role of transcription factors

Interindividual differences of endothelial cells in response to endotoxins might contribute to the diversity in clinical outcome among septic patients. The present study was conducted to test the hypothesis that endothelial cells (EC) with high and low proinflammatory potential exist and to dissect the molecular basis underlying this phenomenon. Thirty human umbilical vein endothelial cell (HUVEC) lines were stimulated for 24 h with lipopolysaccharide (LPS) and screened for interleukin (IL)‐8 production. Based on IL‐8 production five low and five high producers, tentatively called types I and II responders, respectively, were selected for genome‐wide gene expression profiling. From the 74 genes that were modulated by LPS in all type II responders, 33 genes were not influenced in type I responders. Among the 41 genes that were increased in both responders, 17 were expressed significantly stronger in type II responders. Apart from IL‐8, significant differences in the expression of proinflammatory related genes between types I and II responders were found for adhesion molecules [intercellular adhesion molecule (ICAM‐1), E‐selectin)], chemokines [monocyte chemoattractant protein (MCP‐1), granulocyte chemotactic protein (GCP‐2)], cytokines (IL‐6) and the transcription factor CCAAT/enhancer binding protein‐delta (C/EBP‐δ). Type I responders also displayed a low response towards tumour necrosis factor (TNF)‐α. In general, maximal activation of nuclear factor (NF)‐κB was achieved in type I responders at higher concentrations of LPS compared to type II responders. In the present study we demonstrate that LPS‐mediated gene expression differs quantitatively and qualitatively in types I and II responders. Our results suggest a pivotal role for common transcription factors as a low inflammatory response was also observed after TNF‐α stimulation. Further studies are required to elucidate the relevance of these findings in terms of clinical outcome in septic patients.

Hypothermic preservation of lung allograft inhibits cytokine-induced chemoattractant-1, endothelial leucocyte adhesion molecule, vascular cell adhesion molecule-1 and intracellular adhesion molecule-1 expression

Organ dysfunction is a major clinical problem after lung transplantation. Prolonged cold ischaemia and reperfusion injury are believed to play a central role in this complication. The influence of cold preservation on subsequent warm reperfusion was studied in an isolated, ventilated and perfused rat lung. Rat lungs were flushed with cold Perfadex‐solution and stored at 4°C for different time periods. Thereafter lungs were perfused and ventilated for up to 3 h. Physiological parameters, production of inflammatory mediators and leucocyte infiltration were measured before and after perfusion. Lungs subjected to a cold ischaemia time of up to 6 h showed stable physiological conditions when perfused for 3 h. However, cold‐ischaemia time beyond 6 h resulted in profound tissue oedema, thereby impairing ventilation and perfusion. Warm reperfusion and ventilation per se induced a strong inflammatory response, as demonstrated by a significant up‐regulation of chemokines and adhesion molecules (cytokine‐induced chemoattractant‐1, intracellular adhesion molecule and endothelial leucocyte adhesion molecule), accompanied by enhanced leucocyte infiltration. Although the up‐regulation of inflammatory mediators was blunted in lungs that were subjected to cold ischaemia, this did not influence leucocyte infiltration. In fact, cold ischaemia time correlated with leucocyte sequestration. Although cold preservation inhibits the expression of inflammatory mediators it does not affect leucocyte sequestration during warm reperfusion. Cold preservation might cause impairment of the endothelial barrier function, as evidenced by tissue oedema and profound leucocyte infiltration.

Modulation of Pulmonary Vascular Resistance and Edema Formation by Short-Term Infusion of a 10% Fish Oil Emulsion

BACKGROUND The aim of this study was to investigate whether the pulmonary response to inflammatory stimulation, resulting in increased vascular resistance and permeability, could be attenuated by short-term infusion of triglycerides containing omega-3 fatty acids. With the concept of altering the composition of membrane phospholipids in such a manner that stimulation resulted in the release of less vasoconstrictive and permeability-enhancing metabolites of eicosapentaenoic acid instead of those of arachidonic acid (AA), the parenteral application of a lipid emulsion prepared from fish oil (Omegavenös) was tested in comparison with a soy oil preparation (Lipovenös). METHODS Isolated lungs from anesthetized rabbits were ventilated and recirculatingly perfused (200 ml/min) with 200 ml cell-free buffer solution to which either 2 ml saline (controls, n = 6), 2 ml Lipovenös 10% (n = 6) or 2 ml Omegavenös 10% (n = 6) were added. To study the possible metabolic alterations in states of an enhanced AA turnover, lungs of each group were stimulated with smaller doses of A23187 (10(-8) M) during the 180-min lipid perfusion period, followed by a 10 times higher calcium ionophore A23187 (10(-7) M) challenge after washing out the lipids by exchange of perfusion fluid. Pulmonary artery pressure (PAP) and the lung weight gain indicating edema formation were monitored, and eicosanoids were analyzed in samples of the perfusate. RESULTS Upon A23187 injection lung weight gain and PAP increase were significantly reduced (50%) in Omegavenös-perfused lungs in comparison with controls and Lipovenös treatment. The vascular reactions were accompanied by a shifting from LTC4 to LTC5 during and after Omegavenös perfusion. CONCLUSION The data demonstrate that omega-3 fatty acids seem to be incorporated into the phospholipid pool of the pulmonary tissue, even after short-term infusion (3 h) resulting in an attenuated pressure reaction and edema formation due to an altered spectrum of metabolites in the case of inflammatory stimulation.

Fractalkine is not a major chemoattractant for the migration of neutrophils across microvascular endothelium.

Inflammatory responses during sepsis are determined by leucocyte recruitment into inflamed tissues. Both chemokines and adhesion molecules are believed to be involved in this process. As fractalkine exists as transmembrane protein with cell adhesion properties and as soluble chemotactic factor, the present study was conducted to study the role of fractalkine, produced by microvascular and macrovascular endothelial cells, in neutrophil recruitment. Lung microvascular endothelial cells (LMVECs) stimulated with lipopolysaccharide, tumour necrosis factor‐α or interleukin‐1 (IL‐1) produced much more fractalkine compared with the macrovascular human umbilical vein endothelial cells (HUVECs). No differences were found between microvascular endothelial cells of different organs. Chemotactic activity in supernatants was significantly stronger in stimulated LMVEC when compared with HUVEC. Although recombinant fractalkine induced migration of neutrophils, IL‐8 and monocyte chemoattractant protein‐1 were found to be more strictly required. In vivo fractalkine was strongly upregulated in septic lung and kidney. Our data suggest that fractalkine production per se does not explain the preference for inflammation in the lung of septic patients.

Impairment of bacterial clearance induced by norepinephrine infusion in rabbits

ObjectivePurpose of the study was to investigate the potential influence of norepinephrine (NE) on immune functions in terms of systemic and organ-specific bacterial clearance in rabbits.DesignTo enable quantification of the clearance process, defined numbers of exogenousEscherichia coli (1.3×108 CFU) were injected intravenously 60 min after starting the NE infusion at a low dose (1 μg/kg per min,n=6), causing an increase (30 mmHg) in mean arterial pressure without affecting the oxygen uptake, and at a higher dose (7.5 μg/kg per min,n=6), resulting in a marked decrease (20%) in oxygen uptake, after infusion of NaCl solution (control,n=6). In additional experiments (n=6) NE (1 μg/kg per min) was tested in endotoxemia induced by simultaneous infusion of endotoxin (40 μg/kg per h). Parameters monitored were arterial pressure, oxygen uptake, and rates of bacterial elimination from the blood. At 180 min afterE. coli injection, the animals were sacrificed, and tissue samples of liver, kidney, spleen, and lung were collected for bacterial counts.ResultsNE infusion resulted in a dose-dependent prolonged elimination of the injectedE. coli from the blood and in significantly higher (p<0.05) numbers of CFU in liver and lung compared to the controls. Significant impairment of bacterial clearance was found after shockproducing endotoxemia, whereas simultaneous infusion of NE and endotoxin caused only a slightly delayed blood clearance of the injected bacteria.ConclusionNE dose dependently affected bacterial clearance, which might be due to ischemia-derived hypoxic impairment of the phagocytosis and lysis function of the reticuloendothelial system, whereas NE improved elimination of bacteria in a state of endotoxic shock.

Regional heterogeneity of cerebral blood flow response to graded volume-controlled hemorrhage.

ObjectiveOf the animal models of human hemorrhagic shock, the volume-controlled hemorrhage model appears to come closer to the clinical situation than the commonly used pressure-controlled model, since the volumecontrolled model allows regulatory adjustment of blood pressure. The effects of volume-controlled hemorrhage on local cerebral blood flow (LCBF) of conscious animasl are not known. The present study investigates specific reaction patterns of LCBF in comparison to mean cerebral blood flow (CBF) during graded volume-controlled hemorrhagic shock in conscious rats.MethodsConscious, spontaneously breathing, and minimally restrained rats were subjected to different degrees of volume-controlled hemorrhage (taking either 25, 30, 35, or 40 ml arterial blood/kg body weight (b.w.). Thirty minutes after the completion of blood taking, LCBF was determined during hemorrhagic hypovolemia using the autoradiographic iodo (14C) antipyrine method. A group of untreated rats (no hemorrhage) served as controls. LCBF was determined in 34 defined brain structures and mean CBF was calculated.ResultsDuring less severe hemorrhage (25 and 30 ml/kg b.w.) mean CBF was significantly higher than in the control group (+19% and +25%). During severe hemorrhage (35 and 40 ml/kg b.w.) mean CBF remained unchanged compared to the control values, although significant increases in LCBF could be detected in many of the brain structures analyzed (maximum +44%). The mean coefficient of variation of CBF was increased, indicating a larger heterogeneity of LCBF values at shed blood volumes of 35 and 40 ml/kg b.w.ConclusionsA comprehensive and novel description of the local distribution of CBF during graded volume-controlled hemorrhage in conscious rats shows unexpected increases in LCBF and mean CBF. This “hypovolemic cerebral hyperemia” might be caused by endogenous hemodilution, thus maintaining the blood supply to the brain during hypovolemic shock.

Neue Airbag-assoziierte Verletzungsmuster nach Verkehrsunfällen

ZusammenfassungExperimentelle Untersuchungen haben gezeigt, daß bei Verkehrsunfällen mit Frontalaufprall neue Rückhaltesysteme wie der Airbag das Auftreten vital bedrohlicher Verletzungen signifikant reduzieren. Ob der Airbag mit besonderen Verletzungsmustern in Verbindung gebracht werden kann, ist bislang noch nicht eindeutig belegt. Systematisch sind nach Aufarbeitung von Verkehrsunfällen mit Airbagbeteiligung, die Verletzungsmuster und der jeweilige klinische Verlauf von zwei Verkehrsunfällen mit Airbag untersucht worden. In einem Fall verhinderte das Aigbagsystem bei Frontalkollision bei einer Aufprallgeschwindigkeit von 100 km/h vital bedrohlich Verletzungen. In einem anderen Fall wurden zunächst nur geringgradige Gesichtsverletzungen nach dem Verkehrsunfall diagnostiziert; mit einer zeitlichen Verzögerung von 3 h trat hämodynamische Instabilität auf, die durch einen traumatischen Abriß der V. azygos bedingt war. Die Analyse der dargestellten Fälle zeigt neben den offensichtlichen Vorteilen des Airbagsystems Verletzungsmuster, die mit diesem Rückhaltesystem in Verbindung gebracht werden können. Das Airbag-assoziierte Verletzungsausmaß kann nach unseren dargestellten Ergebnissen nicht mit den üblichen klinischen Kriterien abgeschätzt werden. Es wird empfohlen, daß zunächst jeder Airbag-Verunfallte besonders aufmerksam untersucht und einer klinischen Überwachung zugeführt wird.AbstractExperimental studies have shown that in traffic accidents with frontal impact the new airbag system can significantly reduce the incidence of severe injuries and fatal outcome. The question of whether the airbag itself induces specific patterns of injury needs further investigation. Two cases of traffic accidents with airbag protection are presented here. The first case report clearly shows the life-saving and injury-reducing effect of the airbag system in a traffic accident with frontal impact at 100 km/h. In the second case only minor injuries of the face were diagnosed initially. Hemodynamic instability occurred after 3 h of hospitalization due to rupture of the azygos vein. Analysis of the presented cases shows that, besides the well-known benefits, there are certain injury patterns that seem to be related to the use of airbags. These have not been described before. It is concluded that patients who were involved in traffic accidents with airbag deployment have to be hospitalized and followed up carefully over time, even though they are initially stable, as potentially fatal sequelae of deceleration trauma can occur later. In our opinion it is not possible to estimate the severity of airbag-associated injuries with conventional methods.