Heinfried Schmidt

Ketamine modulates the stimulated adhesion molecule expression on human neutrophils in vitro

Cytokine production, neutrophil adhesion to endothelial cells, and release of reactive oxygen species are thought to be critical events in sepsis or ischemia/reperfusion. Modulation of leukocyte responses by anesthetics may have an important role in limiting tissue injury under these conditions. Therefore, we investigated the effect of ketamine on the expression of CD18, CD62L, and oxygen radical production of human neutrophils in vitro and on interleukin-6 production in endotoxin-stimulated human whole blood. Ketamine inhibited both the N- formyl-methionyl-leucyl-phenylalanine- and phorbol 12-myristate 13-acetate-induced up-regulation of CD18 and shedding of CD62L, determined by flow cytometry, in a concentration-dependent manner. Ketamine also caused a significant suppression of oxygen radical generation of isolated human neutrophils. In addition, there was a significant decrease in endotoxin-stimulated interleukin-6 production in human whole blood. The inhibitory effects were similar for racemic ketamine and its isomers S(+)-ketamine and R(-)-ketamine, suggesting that the inhibition of stimulated neutrophil function is most likely not mediated through specific receptor interactions. Implications Modulation of leukocyte responses by anesthetics may have an important role in limiting tissue injury in sepsis or ischemia/reperfusion. Therefore, we examined the effect of ketamine on stimulated neutrophil functions in vitro. These neutrophil functions were significantly inhibited by ketamine, independent of whether the racemic mixture or isomers were tested.

Efficacy of silver-coating central venous catheters in reducing bacterial colonization

OBJECTIVE To compare silver-coated and uncoated central venous catheters regarding bacterial colonization. To assess the relative contribution of catheter hub and skin colonization to catheter tip colonization. DESIGN Prospective, randomized clinical trial. SETTING Intensive care unit in a university hospital. PATIENTS Patients after cardiac surgery who required a central venous double-lumen catheter (DLC). INTERVENTIONS Sixty-seven adult patients were prospectively randomized to receive either a silver-coated (S group, n = 34) or an uncoated control (C group, n = 33) DLC. Blood cultures were drawn at catheter removal, and removed catheters were analyzed with quantitative cultures. Typing of microorganisms included DNA fingerprinting. MEASUREMENTS AND MAIN RESULTS Catheters were removed if no longer necessary and aseptically divided into three segments: segment A, the catheter tip; segment B, an intermediate section; and segment C, the subcutaneous portion. Bacterial catheter colonization was quantitatively measured using sonication to detach adherent bacteria from the catheter segments in the broth and subsequent culture of an aliquot. Selected isolates of coagulase-negative staphylococci and other bacteria from catheter segments were examined by means of pulsed-field gel electrophoresis (PFGE) after macrorestriction digestion of bacterial DNA to study colonization pathogenesis. Quantitatively lower bacterial colonization could be demonstrated on the silver-coated catheters (200 +/- 550 colony forming units [CFUs]/cm catheter segment; mean +/- SD). The difference in the control catheters (1120 +/- 5350 CFUs/cm catheter segment; mean +/- SD) was not, however, significant (p = .25). The frequency of colonization of at least one catheter segment was 52.9% for the silver-coated catheters and 57.6% for the control catheters (p= .44), without any significant differences in the colonization of corresponding catheter segments. The rate of significant catheter colonization (i.e., > or = 10(3) CFUs/cm catheter by quantitative catheter culture or > or = 10(3) CFUs/mL by luminal flush) was nine in the silver group and seven in the control group, a difference that failed to reach significance (p = .41). Two patients in both groups developed catheter-related bacteremia. Pattern analysis after PFGE demonstrated that about 70% of the isolates found on the catheter tip were identical with those on the skin at the insertion site, whereas about 75% were identical with those recovered from the hub. In 29% of colonized catheters, identical bacteria were found on the hub and the skin at the insertion site. CONCLUSIONS Silver-coating of DLCs did not significantly reduce bacterial catheter colonization compared with the control catheters. PFGE analysis of coagulase-negative staphylococci and other bacteria demonstrated various pathogenic routes of catheter-related colonization, whereby the microorganisms of the skin flora around the insertion site must be regarded as the main source of catheter-related infections.

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. 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.

Effects of continuous (CPAP) and bi-level positive airway pressure (BiPAP) on extravascular lung water after extubation of the trachea in patients following coronary artery bypass grafting

ObjectiveTo evaluate the effects of continuous positive airway pressure (CPAP) and bilevel positive airway pressure (BiPAP) on extravascular lung water during weaning from mechanical ventilation in patients following coronary artery bypass grafting.DesignProspective, randomized clinical study.SettingIntensive care unit at a university hospital.PatientsSeventy-five patients following coronary artery bypass grafting.InterventionsAfter extubation of the trachea, patients were treated for 30 min with CPAP via face mask (n=25), with nasal BiPAP (n=25), or with oxygen administration via nasal cannula combined with routine chest physiotherapy (RCP) for 10 min (n=25).Measurements and resultsExtravascular lung water (EVLW), pulmonary blood volume index (PBVI) and cardiac index (CI) were obtained during mechanical ventilation (T1), T-piece breathing (T2), interventions (T3), spontaneous breathing 60 min (T4) and 90 min (T5) after extubation of the trachea using a combined dye-thermal dilution method. Changing from mechanical ventilation to T-piece breathing did not show any significant differences in EVLW between the three groups, but a significant increase in PBVI from 155±5 ml/m2 to 170±4 ml/m2 could be observed in all groups (p<0.05). After extubation of the trachea and treatment with BiPAP, PBVI decreased significantly to 134±6 ml/m2 (p<0.05). After treatment with CPAP or BiPAP, EVLW did not change significantly in these groups (5.5±0.3 ml/kg vs 5.0±0.4 ml/kg and 5.1±0.4 ml/kg vs 5.7±0.4 ml/kg). In the RCP-treated group, however, EVLW increased significantly from 5.8±0.3 ml/kg to 7.1±0.4 ml/kg (p<0.05). Sixty and 90 min after extubation, EVLW stayed at a significantly higher level in the RCP-treated group (7.5±0.5 ml/kg and 7.4±0.5 ml/kg) than in the CPAP-(5.6±0.3 ml/kg and 5.9±0.4 ml/kg). No significant differences in CI could be observed within the three groups during the time period from mechanical ventilation to 90 min after extubation of the trachea.ConclusionsMask CPAP and nasal BiPAP after extubation of the trachea prevent the increase in extravascular lung water during weaning from mechanical ventilation. This effect is seen for at least 1 h after the discontinuation of CPAP or BiPAP treatment. Fuether studies have to evaluate the clinical relavance of this phenomenon.

Dopexamine maintains intestinal villus blood flow during endotoxemia in rats.

OBJECTIVE To determine the influence of dopexamine, a synthetic catecholamine ligand for dopaminergic and beta 2-adrenergic receptors, on alterations of the intestinal villus microcirculation in a model of normotensive endotoxemia. DESIGN Randomized, controlled trial. SETTING Experimental laboratory. SUBJECTS Twenty-one male Wistar rats. INTERVENTIONS Rats were treated with a continuous infusion of dopexamine (2.5 micrograms/kg/min; N = 7; group A) or 0.9% saline (n = 7; group B) during a study period of 120 mins. Both groups were given endotoxin (Escherichia coli lipopolysaccharide; 1.5 mg/kg Iv) over 60 mins. Animals in the control group (n = 7; group C) received a volume-equivalent infusion of 0.9% saline. Total volume substitution in all groups was 15 mL/kg/hr. MEASUREMENTS AND MAIN RESULTS Blood flow in the intestinal villi of the distal ileum was determined using in vivo videomicroscopy at baseline, and 60 and 120 mins after the endotoxin challenge. These blood flow determinations were done by an observer who was unaware of the previous treatment of the animals. In addition, mean arterial pressure was monitored at baseline, and 15, 30, 45, 60, 75, 90, 105, and 120 mins later. The administration of 1.5 mg/kg endotoxin alone (group B) resulted in a reduction of the intestinal villus blood flow to 74.8 +/- 9.5% of baseline after 60 mins, and to 61.1 +/- 8.5% of baseline after 120 mins (baseline: 7.4 +/- 0.6 nL/min; 60 mins: 5.3 +/- 0.8 nL/min; 120 mins: 4.4 +/- 0.5 nL/min; p < .05). This reduction of blood flow was associated with a decrease in the arteriolar diameters by 13.8 +/- 2.5% after 60 mins, and by 17.1 +/- 4.3% after 120 mins (p < .05 vs. baseline). In contrast, villus blood flow in the dopexamine group (group A) did not show statistically significant changes during the entire study period, despite the administration of endotoxin (baseline: 8.2 +/- 0.6 nL/min; 60 mins: 7.3 +/- 0.8 nL/min; 120 mins: 7.8 +/- 0.5 nL/min). No vasoconstriction of the villus arterioles was noted in this group. In control animals (group C), the blood flow (baseline: 8.1 +/- 1.6 nL/min; 60 mins: 7.6 +/- 1.4 nL/min: 120 mins: 7.8 +/- 1.4 nL/min) and the arteriolar diameters remained unchanged throughout the observation period. Mean arterial pressure did not differ between groups: it remained unaltered in all groups during the entire study period. CONCLUSIONS Dopexamine maintains intestinal villus arterial perfusion and prevents the vasoconstriction in villus arterioles during early normotensive endotoxemia. Therefore, further studies in critically ill patients will have to determine whether the early prophylactic use of dopexamine can limit ischemia and prevent the development of multiple organ failure.

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.

Dobutamine maintains intestinal villus blood flow during normotensive endotoxemia: An intravital microscopic study in the rat

PURPOSE The gut plays a pivotal role in sepsis. Intestinal hypoperfusion with subsequent ischemia leads to translocation of endotoxin. Dobutamine has been demonstrated to increase mesenteric blood flow during endotoxic shock; however, its effects on mucosal blood flow especially in intestinal villi is not known. Therefore, we investigated its influence on the blood flow and the arteriolar diameters in intestinal villi in a model of normotensive endotoxemia. MATERIALS AND METHODS Twenty-one male Wistar rats were divided into three groups: (1) control, saline; (2) endotoxin, endotoxin 1.5 mg/kg during 60 minutes; and (3) dobutamine, endotoxin 1.5 mg/kg (60 minutes) and dobutamine 2.5 micrograms/kg/min during 120 minutes. Villus blood flow and arteriolar diameters were determined at 0 minutes, 60 minutes, and 120 minutes in each group using intravital microscopy. RESULTS Villus blood flow was constant in the control group, significantly reduced at 120 minutes in the endotoxin group (120 minutes, 55.1 +/- 7.4%), and remained at baseline values in the dobutamine group. The arteriolar diameters remained constant in the control and the dobutamine groups, but they were significantly reduced in the endotoxin group at 120 minutes (7.8 +/- 0.2 to 6.5 +/- 0.7 micron). CONCLUSION Our results indicate that in rats with normotensive endotoxemia, arteriolar diameters and blood flow in intestinal villi were reduced. Dobutamine prevented arteriolar constriction and maintained villus blood flow at preendotoxemic values.

Circulating intercellular adhesion molecule-1 as an early predictor of hepatic failure in patients with septic shock.

OBJECTIVE To investigate whether endotoxin, interleukin-6, and circulating adhesion molecules, measured sequentially in blood, can predict mortality and organ dysfunction in sepsis. DESIGN Inception cohort study with follow-up for 28 days. SETTING Surgical intensive care unit at a university hospital. PATIENTS A total of 14 consecutive patients were enrolled in the study within the first 24 hrs after onset of septic shock. Seven healthy subjects were studied as controls. INTERVENTIONS Patients were analyzed for mortality and development of organ dysfunction. MEASUREMENTS AND MAIN RESULTS At the end of the 28-day follow-up period, seven of the patients were still alive (survivors) but the other seven (nonsurvivors) had died. At the time of enrollment in the study (day 0), the Acute Physiology and Chronic Health Evaluation II score was 28.4 in survivors (n = 7) and 28.7 in nonsurvivors (n = 7). In contrast, circulating intercellular adhesion molecule-1 (ICAM-1) was significantly higher in nonsurvivors than in survivors. Circulating ICAM-1 predicted mortality in patients with septic shock with a sensitivity and a specificity of 71.4% each. Endotoxin, interleukin-6, circulating L-selectin, P-selectin, E-selectin, and platelet endothelial cell adhesion molecule-1, however, did not distinguish between survivors and nonsurvivors. In addition, circulating ICAM-1 at day 0 showed a significant correlation with the highest serum bilirubin observed during the entire study period (r2 = 0.963). CONCLUSIONS Because only circulating ICAM-1 was higher in nonsurvivors than in survivors at day 0, circulating ICAM-1 may serve as an early prognostic marker for outcome in septic shock. In addition, measurement of circulating ICAM-1 facilitates identification of those patients with the highest risk of developing liver dysfunction.

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.

Dopexamine attenuates endotoxin-induced microcirculatory changes in rat mesentery: role of beta2 adrenoceptors.

OBJECTIVE To investigate the influence of dopexamine on endotoxin-induced leukocyte adherence and on vascular permeability in postcapillary venules of rat mesentery. DESIGN Randomized, controlled trial. SETTING Experimental laboratory. SUBJECTS Twenty-seven male Wistar rats, weighing 250 to 350 g. INTERVENTIONS Rats received one of three treatments: a) infusion of Escherichia coli endotoxin without dopexamine pretreatment; b) infusion of endotoxin with dopexamine pretreatment; or c) infusion of endotoxin after pretreatment with dopexamine and ICI 118,551, a selective beta2-receptor antagonist. MEASUREMENTS AND MAIN RESULTS Leukocyte adherence, red blood cell velocity, and vessel diameters in postcapillary venules were evaluated using in vivo videomicroscopy. Vascular permeability was determined by measuring the extravasation of fluorescence-labeled albumin. Venular wall shear rate was calculated from red cell velocity and vessel diameter. Dopexamine attenuated both the increase in leukocyte adherence and vascular permeability during endotoxemia. The attenuating effect on leukocyte adherence could not be antagonized by the beta2-adrenoceptor antagonist. However, the attenuating effect on vascular permeability was antagonized by ICI 118,551. Dopexamine prevented a decrease in venular wall shear rate during endotoxemia. This effect was not influenced by ICI 118,551. CONCLUSIONS Dopexamine attenuates endotoxin-induced microcirculatory disturbances in rat mesentery. The attenuating effect on vascular permeability is a beta2-adrenoceptor-mediated process, whereas the beta2-adrenoceptor actions of dopexamine play no significant role in attenuating leukocyte adherence.