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M M Gebhard

Publications and source records attributed to M M Gebhard.

At least 91 records · Page 5Linked to original sources
PubMed1997

Extrahepatic biliary obstruction impairs microvascular perfusion and increases leukocyte adhesion in rat liver.

To determine if disturbances of the liver microcirculation may be of pathophysiological relevance for liver damage during acute biliary obstruction, we studied the effects of bile duct ligation (BDL) on hepatic microhemodynamics and leukocyte adhesion in rat liver in vivo. Male Wistar rats were subjected to BDL for 3 days and 7 days, respectively. Sham-operated controls underwent laparotomy without BDL. After 3 days, intravital fluorescence microscopy (IVM) and hydrogen gas (H2) clearance were performed to study hepatic microvascular perfusion. Furthermore, leukocyte-endothelial cell interactions were assessed by IVM. Intercellular adhesion molecule 1 (ICAM-1) protein expression was studied by Western blot analysis and tissue immunofluorescence after 3 and 7 days, respectively. Analysis of microvascular perfusion by IVM revealed a marked impairment of sinusoidal perfusion after 3 days. Assessment of H2 clearance confirmed that overall hepatic microvascular perfusion was decreased. In addition, increased leukocyte adhesion in sinusoids and venules could be observed. A concomitant increase of ICAM-1 expression in liver tissue was also noted within the first week after BDL. Our results show that BDL is followed by a marked depression of the hepatic microcirculation and increased leukocyte adhesion in vivo within 3 to 7 days. Together, these findings suggest that deficits in microvascular perfusion and increased neutrophil infiltration may represent a potential source of liver injury during acute biliary obstruction.

Animals↗
PubMed1997

Effect of the 21-aminosteroid tirilazad mesylate on leukocyte adhesion and macromolecular leakage during endotoxemia.

BACKGROUND: Interstitial accumulation of leukocytes has been related to the development of multiple organ failure after sepsis. Oxygen radicals are involved in the process of leukocyte adherence to the microvascular wall. This study investigates the effects of the oxygen radical scavenger tirilazad mesylate on leukocyte-endothelial interactions, macromolecular leakage, and microhemodynamics in mesenteric venules during endotoxemia. METHODS: Male Wistar rats were randomly allocated to receive tirilazad mesylate (group A, n = 10), its vehicle (group B, n = 10), or saline 0.9% (group C, n = 10) before a 120-minute infusion of endotoxin (2 mg/kg/hr). Furthermore, a control group without receiving endotoxin (group D, n = 10) was investigated. Leukocyte adherence, emigration of leukocytes, and macromolecular leakage were determined in postcapillary venules of the mesentery by using intravital videomicroscopy. RESULTS: During the administration of endotoxin the number of adherent leukocytes per square millimeter of vessel surface progressively increased in group B (baseline, 431 +/- 35 cells/mm2; 120 minutes, 1121 +/- 71 cells/mm2) and group C (baseline, 398 +/- 44 cells/mm2; 120 minutes, 1290 +/- 116 cells/mm2). In group A no increase in leukocyte adherence was observed after 120 minutes (baseline, 415 +/- 81 cells/mm2; 120 minutes, 638 +/- 87 cells/mm2). In control animals the leukocyte adherence remained unchanged (baseline, 347 +/- 41 cells/mm2; 120 minutes, 507 +/- 75 cells/mm2). After 120 minutes, tirilazad mesylate prevented the increase in leukocyte emigration observed in group B and C. Increased macromolecular leakage during endotoxemia (groups B and C) was not influenced by pretreatment with tirilazad. Tirilazad did not affect the decrease in red cell velocity, volumetric blood flow, and venular shear rate observed during endotoxemia. CONCLUSIONS: This study demonstrates inhibitory effects of tirilazad on endotoxin-induced leukocyte adherence and emigration, suggesting a potential therapeutic role for this substance in the prevention of sepsis-induced multiple organ failure.

Animals↗
PubMed1997

Inhibition of nitric oxide synthesis in ischemia/reperfusion of the rat liver is followed by impairment of hepatic microvascular blood flow.

BACKGROUND: Recent studies provide evidence that nitric oxide (NO) has beneficial effects in hepatic ischemia/reperfusion injury. The purpose of this study was to evaluate whether nitric oxide is involved in the regulation of hepatic microvascular perfusion after warm hepatic ischemia. Therefore, we performed a study using in vivo fluorescence microscopy. METHODS: Clamping of the left liver lobe was performed in male Wistar rats for the duration of 70 min. One experimental group (n=8) received L-NAME (Nw-nitro-L-arginine methyl ester hydrochloride), an NO-synthase inhibitor, 1 min prior to reperfusion. A second experimental group (n=8) received L-arginine (NO-substrate) continuously infused throughout the observation period. Controls (n=8) received equivalent volumes of an isotonic solution and underwent the same procedures. Hepatic microvascular blood flow and leukocyte-endothelial cell interaction was studied between 20 and 90 min after reperfusion using in vivo fluorescence microscopy. RESULTS: Inhibition of NO-synthesis during reperfusion by application of L-NAME caused a marked decrease in sinusoidal blood flow velocity. Furthermore, we noted an increase of non-perfused sinusoids in this group. Treatment with L-arginine improved functional perfusion of hepatic acini and reduced significantly the number of adherent leukocytes in sinusoids and venules compared to control animals. CONCLUSIONS: Our results provide further evidence that NO maintains postischemic hepatic microvascular perfusion and that inhibition of NO synthesis has detrimental effects on hepatic microhemodynamics during reperfusion.

Animals↗
PubMed1997

Direct visualization of leukocyte/endothelial cell interaction during extracorporeal circulation (ECC) in a new animal model.

OBJECTIVE: The clinical complications of extracorporeal circulation (ECC) have been linked to a systemic activation of cellular and humoral components and to a dysregulation of the microcirculatory compartment. Since to date only in vitro methods exist for evaluation, we developed an animal model to study the effects of ECC on the microcirculation. To establish the model, we assessed whether these effects are dependent on the duration of ECC. METHODS: Intravital fluorescence microscopy was used on the dorsal skinfold chamber preparation in chronically instrumented, awake Syrian golden hamsters. ECC was realized using a micro-rollerpump and a silicon tube shunting blood between the carotid artery and the jugular vein. ECC was performed in three groups for various times (2, 10 and 20 min) after application of heparin at 300 IU/kg body wt. In hamsters, the application of high-dose heparin releases endothelial bound superoxide dismutase (SOD), a natural scavenger of oxygen-derived free radicals. Protocol II assigned two groups receiving heparin at different doses of 50 and 2000 IU/kg body wt. RESULTS: ECC for 2 min served as control to exclude effects from hemodilution and resulted in a minimal induction of leukocyte/endothelial cell interaction. Isovolemic ECC for 20 min resulted in an increase in rolling (from 11 +/- 3 to 38 +/- 20%, mean +/- S.D., P < 0.05) and adherent leukocytes (from 19 +/- 16 to 215 +/- 145 cells/mm2, mean +/- S.D., P < 0.05) in postcapillary venules. Microhemodynamic parameters and functional capillary density were not significantly affected. Arterial blood pressure and heart rate were stable. Heparin at 2000 IU/kg inhibited post-ECC leukocyte adhesion following ECC, whereas 50 IU/kg showed no protective effects. CONCLUSIONS: Leukocyte/endothelial cell interaction, induced by blood contact with synthetic surfaces, was directly visualized in vivo. The number of adherent leukocytes was dependent on the duration of ECC. The application of high-dose heparin followed by release of SOD almost prevented leukocyte activation, suggesting a formation of oxygen free radicals during ECC. The new application of the hamster model may allow to study the underlying pathomechanisms and to develop therapeutic/prophylactic strategies to avert problems associated with ECC.

Animals↗
PubMed1997

Effects of mixed ETA and ETB-receptor antagonist (Ro-47-0203) on hepatic microcirculation after warm ischemia.

There is evidence that endothelin (ET) is involved in disturbances of the hepatic microcirculation after warm ischemia. In this study we investigated the influence of a mixed ETA-, ETB-receptor antagonist (Bosentan) on ischemia-reperfusion damage of the liver by means of intravital fluorescence microscopy (IVM). Clamping of the left liver lobe (= warm ischemia) was performed in 16 male Wistar rats for 70 min. The treatment group (N = 8) received 15 mg/kg Bosentan (Ro-47-0203) 1 min prior to reperfusion. Controls (N = 8) received an equivalent amount of Ringer's solution. Between 20 and 90 min after reperfusion, leukocyte-endothelial cell interactions in sinusoids and postsinusoidal venules as well as perfusion of hepatic acini were studied. Application of Bosentan improved sinusoidal blood flow, attenuated manifestations of microvascular perfusion failure, and decreased the number of rolling leukocytes in postsinusoidal venules. Our results provide further evidence that ET is involved in postischemic impairment of hepatic microhemodynamics during reperfusion.

Animals↗
PubMed1997

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 micro-hemodynamics. 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 x kg(-1) x h(-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 x kg(-1) x h(-1)). Leukocyte adherence, erythrocyte velocity (V(RBC), and vessel diameters (Dv) were determined at baseline and at 60 and 120 min in mesenteric postcapillary 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 x V(RBC) x Dv(-1). RESULTS: Lidocaine significantly attenuated the increase of leukocyte adherence during endotoxemia. There were no significant differences of tau within or between the groups. Macromolecular 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. CONCLUSIONS: These results show that lidocaine attenuates endotoxin-induced alterations in leukocyte-endothelial cell adhesion and macromolecular leakage, which suggests that lidocaine may have a therapeutic role in preventing endothelial damage in sepsis.

Anesthetics, Local↗
PubMed1997

N-acetylcysteine attenuates endotoxin-induced leukocyte-endothelial cell adhesion and macromolecular leakage in vivo.

OBJECTIVE: To determine the influence of N-acetylcysteine on endotoxin-induced leukocyte-endothelial cell adhesion, vascular leakage, and venular microhemodynamics. DESIGN: Randomized, blinded, controlled trial. SETTING: Experimental laboratory. SUBJECTS: Thirty male Wistar rats. INTERVENTIONS: After pretreatment with N-acetylcysteine (150 mg/kg; n = 40; group A) or 0.9% saline solution (n = 10; group B) animals were given an intravenous infusion of endotoxin (Escherichia coli lipopolysaccharide 026:B6; 2 mg/kg/hr) over 120 mins. Animals in the control group (n = 10; group C) received a volume-equivalent infusion of 0.9% saline solution. MEASUREMENTS AND MAIN RESULTS: Leukocyte adherence, red cell velocity (VRBC), vessel diameters, venular wall shear rate, and macromolecular leakage were determined in mesenteric postcapillary venules using in vivo videomicroscopy at baseline and at 30, 50, 90, and 120 mins after the start of the endotoxin challenge. Endotoxin exposure induced a marked increase in adherent leukocytes (group B: baseline, 391 +/- 24 cells/mm2; 120 mins, 1268 +/- 131 cells/mm2; p < .01). N-acetylcysteine pretreatment attenuated the adherence of leukocytes during endotoxemia (baseline, 366 +/- 28 cells/mm2; 120 mins, 636 +/- 49 cells/mm2; p < .01 vs. baseline; p < .01 vs. group B). Leukocyte adherence in control animals (group C) did not increase significantly. Administration of N-acetylcysteine did not influence the decrease in VRBC observed during endotoxemia. In group B1 VRBC decreased during the infusion of endotoxin from 2.0 +/- 0.2 mm/sec at baseline to 1.1 +/- 0.2 mm/ sec after 120 mins (p < .01 vs. baseline; p < .05 vs. group C), and in group A from 2.2 +/- 0.2 mm/sec to 1.1 +/- 0.1 mm/sec after 120 mins (p < .01 vs. baseline; p < .05 vs. group C). In group C, VRBC remained unchanged (baseline, 1.7 +/- 0.2 mm/sec; at 120 mins, 1.5 +/- 0.2 mm/sec). The venular diameters remained unchanged in all groups during the entire study period. After 120 mins, the venular wall shear rate decreased from 502 +/- 62 secs-1 at baseline to 272 +/- 46 sec-1 in group B (p < .01), and from 563 +/- 45 secs-1 at baseline to 283 +/- 31 secs-1 in group A (p < .01). No differences in venular wall shear rate were observed between these groups. In group C, the venular wall shear rate remained unchanged (baseline, 457 +/- 54 secs-1; at 120 mins, 409 +/- 51 secs-1). Macromolecular leakage, expressed as perivenular/intravenular fluorescence intensity after injection of fluorescence-labeled albumin, increased from 0.29 +/- 0.03 to 0.58 +/- 0.03 (p < .01) during the infusion of endotoxin in group B. In contrast, pretreatment with N-acetylcysteine diminished the extravasation of albumin (baseline, 0.27 +/- 0.01; at 120 mins, 0.37 +/- 0.02; p < .01 vs. baseline; p < .01 vs. group B). CONCLUSION: These results demonstrate that N-acetylcysteine attenuates endotoxin-induced alterations in leukocyte-endothelial cell adhesion and macromolecular leakage, suggesting N-acetylcysteine might be therapeutic in the prevention of endothelial damage in sepsis.

Acetylcysteine↗
PubMed1996

Impact of N-acetylcysteine on the hepatic microcirculation after orthotopic liver transplantation.

Recent observations showed an improvement of hepatic macro- and microhemodynamics as well as survival rates after warm ischemia of the liver following treatment with N-acetylcysteine (NAC). In this study we assessed the influence of NAC on the hepatic microcirculation after orthotopic liver transplantation (OLT) using intravital fluorescence microscopy. OLT with simultaneous arterialization was performed in 16 male Lewis rats following cold storage in University of Wisconsin solution for 24 hr. Within the experimental group (n = 8) donors received NAC (400 mg/kg) 25 min before hepatectomy. In addition, high-dose treatment of recipients with NAC (400 mg/kg) was started with reperfusion. Control animals (n = 8) received an equivalent amount of Ringer's solution. Intravital fluorescence microscopy was performed 30-90 min after reperfusion assessing acinar and sinusoidal perfusion, leukocyte-endothelium interaction, and phagocytic activity. Treatment with NAC reduced the number of nonperfused sinusoid from 52.4 +/- 0.8% to 15.7 +/- 0.5% (p = 0.0001) (mean +/- SEM). Furthermore, we achieved a significant reduction of leukocytes adhering to sinusoidal endothelium (per mm2 liver surface) from 351.9 +/- 13.0 in controls to 83.6 +/- 4.2 in the experimental group (P = 0.0001). In postsinusoidal venules, treatment with NAC decreased the number of sticking leukocytes (per mm2 endothelium) from 1098.5 +/- 59.6 to 425.9 +/- 37.7 (P = 0.0001). Moreover, bile flow was significantly increased after therapy with NAC (4.3 +/- 1.2 vs. 2.2 +/- 0.7 ml/90 min x 100g liver) (P < 0.05). Phagocytic activity was not influenced by application of NAC. We conclude that high-dose therapy with NAC in OLT attenuates manifestations of microvascular perfusion failure early after reperfusion and should be considered as a means to reduce reperfusion injury.

Acetylcysteine↗
PubMed1996

Influence of the platelet-activating factor receptor antagonist BN52021 on endotoxin-induced leukocyte adherence in rat mesenteric venules.

The aim of this study was to investigate the influence of the platelet-activating factor (PAF) antagonist BN52021 on endotoxin-induced leukocyte-endothelium interactions and on venular microcirculation. The rates of leukocyte adherence and changes in red cell velocity, volumetric blood flow, vessel diameter, and venular shear rate were monitored in rat mesenteric venules following intravenous lipopolysaccharide (LPS) exposure (15 mg/kg body wt). The experiments were performed in LPS-treated control animals and in animals pretreated with the PAF receptor antagonist BN52021. LPS exposure induced a marked increase in adherent leukocytes in the control group compared to the BN52021-pretreated group. Thirty minutes after LPS injection, 6.1 +/- 0.8 leukocytes were adherent to 100 microns of venule in the control group compared to 2.5 +/- 0.5 in BN52021-pretreated animals (P < 0.01). The increased leukocyte adherence in the control group was accompanied by leukocytopenia. Red cell velocity, volumetric blood flow, vessel diameter, and venular shear rate did not differ between groups, indicating that increased leukocyte adherence in the control group was not due to diminished hydrodynamic dispersal forces. The attenuation of leukocyte adherence by the PAF receptor antagonist BN52021 suggests that PAF is involved in the mediation of the initial process of leukocyte sticking to the endothelium after LPS stimulation.

Animals↗
PubMed1996

Effect of endotoxemia on intestinal villus microcirculation in rats.

Intestinal mucosal hypoperfusion with subsequent ischemia during endotoxemia might cause a breakdown of the gut barrier with translocation of bacteria and their toxins into the systemic circulation, thus maintaining a "gut-derived" septic state. The aim of this study was to investigate the influence of endotoxin on the microcirculation of intestinal villi, which represent the most vulnerable part of the mucosa. The changes in blood flow and in the diameters of the central villus arterioles located in the distal ileum were monitored in control rats without lipopolysaccharide (LPS) exposure (n=7), and in rats receiving 1.5 mg/kg b.w. LPS (n=7) or 15 mg/kg b.w. LPS (n=7) over 60 min. The blood flow and the arteriolar diameters were determined using in vivo videomicroscopy at baseline, and 60 min and 120 min later. In control animals, no change in blood flow and arteriolar diameters were observed during the entire experiment. Administration of 1.5 mg/kg b.w. LPS reduced the blood flow to 69.5 +/- 9.0% of the baseline value at the end of the study period. This decrease in blood flow was associated with a decrease in the villus arteriolar diameters by 17.4 +/- 2.5% from the baseline values. In animals exposed to 15 mg/kg b.w. LPS, the decrease in villus blood flow at 60 min was 64.8 +/- 10.9% of baseline, and at 120 min 66.9 +/- 12.6% of baseline. The diameters of the villus arterioles were reduced by 11.5 +/- 2.4% and 15.1 +/- 1.7%, respectively. In the control group and in the 1.5-mg/kg LPS group, the mean arterial blood pressure did not change during the entire study period. In the 15-mg/kg LPS group, the mean arterial pressure tended to decrease after 60 min. These data suggest a reduction of villus blood flow due to vasoconstriction in the central villus arterioles during normotensive endotoxmia, which might represent the mechanism for the mucosal ischemia observed in critically ill patients.

Animals↗
PubMed1996

Continuous measurement of porcine renal cortex microcirculation with enhanced thermal diffusion technology.

Continuous monitoring of renal cortical blood flow (RCBF) in the perioperative setting of aortic or renal vascular surgery could facilitate the early detection of vascular complications, possibly resulting in a reduction of postoperative renal failure. A new prototype system for measurement of parenchymous organ perfusion based on the principle of thermal diffusion ("TD"-Thermal Diffusion Electrode, Thermal Technologies Inc., Cambridge, MA, USA) was used for RCBF measurements in the outer cortex of the porcine kidney. We validated the sensitivity of the device to detect renal blood flow impairment, comparing TD flow data with renal artery blood flow values (RABF), measured by ultrasonic flow probes. The hypothesis was tested that acute disturbances of RCBF, induced by a variable degree of renal artery stenosis, can be immediately detected and continuously monitored by TD measurements in the porcine renal cortex. Mean baseline RCBF measured by TD electrodes was 68.1 +/- 25.0 ml/100 g/min. Mean baseline RABF was 102.1 +/- 26.6 ml/min. Controlled induction of a variable degree of renal arterial occlusion by implanted vascular balloon occluders was always followed by an immediate and proportional decline of RCBF, as measured by TD. Flow data obtained with both methods were significantly correlated by linear regression (r=.82, r2=.68; P < 0.0001). Dynamic changes of RABF in the time course of renal artery partial/total occlusion and arterial flow release could be continuously followed by detection of corresponding flow changes of RCBF. We conclude that the TD system investigated in the current study allows a continuous and sensitive determination of porcine renal cortex perfusion. A clinical evaluation of the method, e.g., in the perioperative setting of aortic or renal transplantation surgery, now appears to be justified.

Animals↗
PubMed1996

Different effect of inhaled nitric oxide on yucatan micropig with and without congenital ventricular septal defect.

A strain of Yucatan micropigs is known to have heritable ventricular septal defects (VSDs) and thus may develop overflow pulmonary hypertension. Since inhaled nitric oxide (NO) selectively dilates pulmonary vessels, we determined its hemodynamic and co-agulatory effects in this new animal model. Eight Yucatan micropigs were anesthetized with midazolam, piritramide (a synthetic opioid) and vecuronium bromide. The presence and the size of the VSD were determined by using transesophageal color flow Doppler echocardiography. Four animals showed VSDs of 1-2 mm size. Inhaled NO was then administered with increasing inspired concentrations of 0, 5, 10, 20, 40, 80 and again 0 ppm NO for 10-min periods. NO inhalation did not affect heart rate, right cardiac output, mean arterial pressure, pulmonary arterial wedge pressure, or central venous pressure. Inhaled NO in animals with proven VSDs decreased pulmonary artery pressure (PAP) in a dose dependent manner; 5 ppm NO reduced mean PAP from 25 +/- 2.3 mm Hg to 18 +/- 0.8 mm Hg (p < 0.05), while pulmonary vascular resistance (PVR) decreased from 954 +/- 143 dyn.cm. s-5 to 661 +/- 88 dyn.cm.s-5 (p < 0.01) at the same dose. The maximum reduction in mean PAP and PVR occurred when 80 ppm NO was inhaled. Yucatan micropigs without VSDs did not respond hemodynamically to NO inhalation. Methemoglobin levels remained unchanged during the entire study. Platelet function was assessed according to the method of BREDDIN and BORN (BORN 1962). Initial aggregation and slope were affected when NO inhalation commenced. Yucatan micropigs with VSDs may represent a suitable model for further research of the in vivo effects of inhaled NO.

Administration, Inhalation↗
PubMed1995

Morphometric evaluation of volume shifts between intra- and extra-cellular space before and during global ischemia.

BACKGROUND: It is well known that all forms of cardiac arrest lead to global ischemia combined with alterations in cellular and interstitial volume. The aim of this study was to investigate the nature of these alterations with respect to different methods of cardiac arrest and establish the extent of their mutual influence at the onset as well as during the course of global ischemia. METHODS: Three tested clinical methods were employed to induce cardiac arrest by a) aortic cross clamping, b) coronary perfusion with the cardioplegic solution St. Thomas, and c) coronary perfusion with the cardioplegic solution histidine-tryptophane-ketoglutarate (HTK). The arrested hearts were subjected to global ischemia at 25 degrees C. The size of the myocytes, as well as the interstitial space of myocytes, was determined morphometrically. The contraction state of myocytes was evaluated according to a score. RESULTS: We found that the degree of contraction, as well as nature of alterations in the cellular and interstitial volumes, depended both on the form of cardiac arrest and on the duration of ischemia. The following relationships were established. High contraction at the onset of ischemia leads to expulsion of fluid from the interstitium between bundles of myocytes into the tissue clefts increasing their size. The decrease in contraction during ischemia leads to narrower tissue clefts. Cellular swelling at the onset of and during ischemia is caused by volume shifts between intracellular and interstitial space. An increase in cellular volume during global ischemia and/or additional contraction reduce the interstitium within bundles of myocytes. Sufficient relaxation and/or interstitial edema enlarge the interstitium. CONCLUSIONS: Cellular and interstitial alterations seen at the onset and during the course of ischemia are dependent upon the method of cardiac arrest. Furthermore, a considerable mutual influence is exerted by the alterations in cellular and interstitial spaces.

Animals↗
PubMed1995

Measurement of blood flow in pancreatic exchange capillaries with FITC-labeled erythrocytes.

Characterization of pancreatic capillary blood flow by in vivo microscopy has been limited by technical shortcomings associated with the use of plasma tracers and the lack of quantitative data. Therefore, fluorescent-labeled erythrocytes were evaluated for quantitation of pancreatic capillary blood flow in rats in physiological state and under defined conditions of increased and impaired pancreatic blood flow. Physiological blood flow was 1.21 +/- 0.06 nl/min per capillary with stable capillary perfusion pattern. Reduction of pancreatic blood flow by decreasing systemic arterial pressure to 60 mmHg through controlled hemorrhage produced a profound decrease of volumetric flow to 0.21 +/- 0.05 nl/min (P < 0.05). The number of perfused capillaries was reduced to 52 +/- 8% of baseline (P < 0.001) and the intermittent perfusion pattern was altered in 26 +/- 5% (P < 0.001) of observed capillaries. Stimulation of pancreatic perfusion with intravenous secretin (5 CU/kg/hr) induced a transient decline to 0.94 nl/min (P < 0.05) followed by a continuous increase to 2.39 nl/min (P < 0.001). The intermittent flow pattern was modified in 15 +/- 3% of capillaries (P < 0.05). Fluorescent-labeled erythrocytes provide unique and reliable qualitative and quantitative data about pancreatic microcirculatory changes. Confinement of the fluorescent tracer to erythrocytes prevents extravasation and minimizes phototoxicity, thereby improving intravital analysis of blood flow in pancreatic exchange capillaries.

Animals↗
PubMed1995

Ketamine attenuates endotoxin-induced leukocyte adherence in rat mesenteric venules.

OBJECTIVES: To determine the influence of ketamine on endotoxin-induced leukocyte adherence and venular microhemodynamics. DESIGN: Randomized, controlled trial. SETTING: Experimental laboratory. SUBJECTS: Thirty male Wistar rats. INTERVENTIONS: The rats were pretreated with ketamine (10 mg/kg iv) or 0.9% saline, and both groups were given endotoxin (Escherichia coli lipopolysaccharide; 5 mg/kg iv). The control group received two doses of 0.9% saline. MEASUREMENTS AND MAIN RESULTS: The rates of leukocyte adherence and changes in microhemodynamics were monitored in rat mesenteric venules, using in vivo video microscopy. The number of adherent leukocytes was determined on-line in 10-min intervals from 60 mins before until 2 hrs after endotoxin administration. Venular diameters, red blood cell velocity, volumetric blood flow, and the venular wall shear rate were monitored before and at 10, 30, and 60 mins after endotoxin exposure. A 6.3-fold increase in the number of adherent leukocytes was observed 10 mins after administration of endotoxin when compared with control animals (5.87 +/- 0.69 vs. 0.93 +/- 0.21 adherent cells/100 microns; p < .001). This increase remained unchanged for 120 mins. In ketamine-pretreated rats, a 2.6-fold increase in leukocyte adherence occurred during the first 20 mins after endotoxin exposure (2.40 +/- 0.46 vs. 0.93 +/- 0.21 adherent cells/100 microns; p < .01). However, no difference in the number of adherent leukocytes between ketamine-pretreated and control animals was found after this 20-min period. In animals of the control group, no increase in leukocyte adherence occurred during the entire observation time. Diameters of mesenteric venules did not change after endotoxin exposure in any of the groups. Red blood cell velocity and venular blood flow in the endotoxin-treated groups decreased 10 mins after the injection of endotoxin when compared with controls, but these values did not show any difference when they were compared between ketamine and saline-pretreated animals. Similarly, venular wall shear rate in the endotoxin-treated groups decreased 10 and 30 mins after injection of endotoxin. However, no significant difference occurred between ketamine and saline-pretreated animals. CONCLUSIONS: Pretreatment with ketamine attenuates endotoxin-induced leukocyte adherence by a shear rate-independent mechanism, suggesting reduced expression of adhesion molecules. These results indicate that ketamine exerts an anti-inflammatory effect, which might be beneficial in septic patients.

Animals↗
PubMed1995

[Induction of impaired hepatic microcirculation by in situ hilus preparation in liver explantation].

AIM: Usually, in-situ preparation of the hepatic hilar structures is performed prior to the perfusion with preservation solution. Aim of this study was to investigate mechanical effects of liver preparation on the hepatic microcirculation. METHODS: 16 pigs (German landrace) were randomized in two groups. In both groups, laparotomy was performed after intratracheal intubation. Subsequently, a thermal diffusion probe was implanted into the medial left liver lobe for quantification of microperfusion. In group A (n = 8), bile duct, hepatic artery, and portal vein were exposed and the lesser omentum transsected thereafter. Ultrasound-volume-probes were placed around the hepatic artery and portal vein. Simultaneous measurement of hepatic microperfusion and total liver blood flow was performed five minutes after the end of liver preparation. In group B (n = 8) hepatic microperfusion was quantified 45 minutes after laparotomy without further manipulations. RESULTS: By the preparation, liver perfusion was significantly reduced in group A from 78 +/- 13 ml/100g/min to 61 +/- 16 ml/100g/min. After preparation a total liver blood flow of 137 +/- 46 ml/100g/min was recorded indicating a shunt fraction of 51 +/- 21%. In contrast, hepatic microperfusion in group B remained at baseline during the whole observation period (79 +/- 3 ml/100g/min vs. 78 +/- 5 ml/100g/min). CONCLUSION: In-situ liver preparation induces a relevant disturbance of hepatic microcirculation. Preservation perfusion shortly after surgical manipulation could become ineffective because of an increase in shunt flow. If the regeneration period is too short, e.g. lack of heart explantation, the quality of the liver graft could be limited.

Animals↗