Machine learning identifies ICU outcome predictors in a multicenter COVID-19 cohort.

BACKGROUND: Intensive Care Resources are heavily utilized during the COVID-19 pandemic. However, risk stratification and prediction of SARS-CoV-2 patient clinical outcomes upon ICU admission remain inadequate. This study aimed to develop a machine learning model, based on retrospective & prospective clinical data, to stratify patient risk and predict ICU survival and outcomes. METHODS: A Germany-wide electronic registry was established to pseudonymously collect admission, therapeutic and discharge information of SARS-CoV-2 ICU patients retrospectively and prospectively. Machine learning approaches were evaluated for the accuracy and interpretability of predictions. The Explainable Boosting Machine approach was selected as the most suitable method. Individual, non-linear shape functions for predictive parameters and parameter interactions are reported. RESULTS: 1039 patients were included in the Explainable Boosting Machine model, 596 patients retrospectively collected, and 443 patients prospectively collected. The model for prediction of general ICU outcome was shown to be more reliable to predict "survival". Age, inflammatory and thrombotic activity, and severity of ARDS at ICU admission were shown to be predictive of ICU survival. Patients' age, pulmonary dysfunction and transfer from an external institution were predictors for ECMO therapy. The interaction of patient age with D-dimer levels on admission and creatinine levels with SOFA score without GCS were predictors for renal replacement therapy. CONCLUSIONS: Using Explainable Boosting Machine analysis, we confirmed and weighed previously reported and identified novel predictors for outcome in critically ill COVID-19 patients. Using this strategy, predictive modeling of COVID-19 ICU patient outcomes can be performed overcoming the limitations of linear regression models. Trial registration "ClinicalTrials" (clinicaltrials.gov) under NCT04455451.

Effects of different leukocyte subpopulations and flow conditions on leukocyte accumulation during reperfusion.

BACKGROUND/AIMS: The study examined the interdependent effects of shear stress and different leukocyte subpopulations on endothelial cell activation and cell interactions during low flow and reperfusion. METHODS: Human umbilical venous endothelial cells were perfused with either neutrophils or monocytes at different shear stress (2-0.25 dyn/cm(2)) and adhesion was quantified by microscopy. Effects of adherent neutrophils and monocytes on endothelial cell adhesion molecule expression were analyzed by flow cytometry after 4-hour static coincubation. After coincubation, the cocultures were reperfused with labeled neutrophils at 2 dyn/cm(2) and their adhesion was quantified selectively. For the control, endothelium monocultures with and without lipopolysaccharide activation were used. RESULTS: At 2 dyn/cm(2), adhesion did not exceed baseline levels on nonactivated endothelium. Decreasing shear stress to 0.25 dyn/cm(2) largely increased the adhesion of both leukocyte subpopulations, similar to the effect of lipopolysaccharide at 2 dyn/cm(2). However, only adherent monocytes increased adhesion molecule expression, whereas neutrophils had no effect. As a functional consequence, adherent monocytes largely increased neutrophil adhesion during reperfusion, whereas adherent neutrophils did not. CONCLUSION: Compromised shear stress is an autonomous trigger of leukocyte adhesion even in the absence of additional activators. Exceeding this immediate effect, adherent monocytes induce further endothelial activation and enhance further neutrophil adhesion during reperfusion.

ImageStream cytometry extends the analysis of phagocytosis and oxidative burst.

AIM: Phagocytosis is often measured using conventional microscopy and flow cytometry. ImageStream cytometry is a new technology that combines the advantages of both methods, enabling statistically robust microscopic applications. We compared ImageStream cytometry to flow cytometry in a whole blood model of phagocytosis with viable, fluorescence-marked Staphylococcus aureus. We furthermore measured the co-localization of intracellular bacteria to sites of oxidative burst, as well as changes in cell size and actin levels as a result of phagocytosis. EXPERIMENTAL DESIGN: Fluorescence-labeled S. aureus in a ratio of 5:1 bacteria per leukocyte were added to whole blood. Phagocytosis was stopped at different time points. After staining of neutrophils and lysis of erythrocytes, samples were analysed by ImageStream cytometry and flow cytometry. RESULTS: Phagocytosis and oxidative burst determined by flow cytometry and ImageStream cytometry showed strong correlation. In contrast to flow cytometry, ImageStream cytometry easily detected and excluded extracellular adherent bacteria from the measurement of phagocytosis, and enumerated the bacteria within each neutrophil. Using the Bright Detail Similarity score, we identified a subset of neutrophils with intracellular bacteria co-localized to sites of oxidative burst activity. Phagocytosis resulted in an increase in cell size and actin polymerization as determined by an increase in phalloidin fluorescence intensity. CONCLUSIONS: We describe a simple whole blood image-based method for measuring bacterial phagocytosis and oxidative burst. ImageStream cytometry provides the spatial resolution to determine the number of bacteria ingested and the sub-cellular localization and trafficking patterns that enables a more complete evaluation of the phagocytic process.

Mechanisms of leukocyte distribution during sepsis: an experimental study on the interdependence of cell activation, shear stress and endothelial injury.

INTRODUCTION: This study was carried out to determine whether interactions of cell activation, shear stress and platelets at sites of endothelial injury explain the paradoxical maldistribution of activated leukocytes during sepsis away from local sites of infection towards disseminated leukocyte accumulation at remote sites. METHODS: Human umbilical venous endothelial cells (HUVEC) and polymorphonuclear neutrophils (PMN) were activated with lipopolysaccharide at 100 and 10 ng/ml to achieve adhesion molecule patterns as have been reported from the hyper- and hypo-inflammatory stage of sepsis. To examine effects of leukocyte activation on leukocyte-endothelial interactions, activated HUVEC were perfused with activated and non-activated neutrophils in a parallel plate flow chamber. Adhesion molecule expression and function were assessed by flow cytometry and blocking antibodies. In a subset of experiments the sub-endothelial matrix was exposed and covered with platelets to account for the effects of endothelial injury. To investigate interactions of these effects with flow, all experiments were done at various shear stress levels (3 to 0.25 dyne/cm(2)). Leukocyte-endothelial interactions were analyzed by videomicroscopy and analysis of covariance. RESULTS: Activation of neutrophils rendered adhesion increasingly dependent on shear stress reduction. At normal shear stress, shedding of L-selectin decreased adhesion by 56%. Increased rolling fractions of activated PMN at low shear stress revealed impaired integrin affinity despite numerical up-regulation of CD11b. On sub-maximally activated, intact HUVEC shear stress became the prevailing determinant of adhesion. Presence of a platelet-covered injury with high surface density of P-selectin was the strongest variable for adhesion. When compared to maximally activated HUVEC, platelets increased neutrophil adhesion by 2.7-fold. At sub-maximal activation a 10-fold increase was observed (P < 0.05 for all). CONCLUSIONS: L-selectin shedding and integrin dysfunction render leukocyte adhesion increasingly susceptible to shear stress and alternative adhesion receptors. In combination, these effects inhibit recruitment to normally perfused sites with intact endothelium and favor maldistribution towards sites with compromised perfusion or endothelial injury.

Effects of 1400W and/or nitroglycerin on renal oxygenation and kidney function during endotoxaemia in anaesthetized rats.

1. The pathogenesis of acute renal failure (ARF) in sepsis is multifactorial. The role of nitric oxide (NO) in septic ARF has been a source of controversy. We hypothesized that endotoxaemia-induced exacerbation of inducible nitric oxide synthase (iNOS)-related NO release impairs renal oxygenation and contributes to ARF in anaesthetized rats. 2. In the present study, rats received lipopolysaccharide (2.5 mg/kg) for 30 min. Two hours later, fluid resuscitation was started (HES130; 5 mL/kg per h after a 5 mL/kg bolus) supplemented either by the NO donor nitroglycerin (NTG; 0.5 µg/kg per min after a 2 µg/kg bolus), the selective iNOS inhibitor 1400 W (3 mg/kg per h after a 3 mg/kg bolus) or both. Systemic haemodynamics and renal microvascular Po2 (µPo(2)) were recorded continuously. Furthermore, creatinine clearance, plasma NO(x) (nitrate + nitrite + S-nitrosothiols) levels and the expression of iNOS mRNA were measured. 3. Endotoxaemia reduced renal blood flow, decreased mean arterial pressure, resulted in anuria and was associated with an increase in plasma NO(x) levels and renal iNOS expression. Renal µPo2 deteriorated gradually during endotoxaemia and there was a significant decrease in renal O(2) delivery and consumption. Manipulation of NO levels had no beneficial effect on systemic haemodynamics, renal µPo(2) or creatinine clearance over standard fluid resuscitation. The application of 1400 W+NTG significantly reduced plasma NO(x) levels compared with fluid resuscitation and NTG alone. 4. Neither iNOS inhibition, NO donation nor a combination of both showed beneficial effects on systemic haemodynamics, renal oxygenation and renal function compared with fluid resuscitation alone. Our results question the proposed key role of NO in the pathogenesis of septic ARF in rats.

Influence of fluid resuscitation on renal microvascular PO2 in a normotensive rat model of endotoxemia.

INTRODUCTION: Septic renal failure is often seen in the intensive care unit but its pathogenesis is only partly understood. This study, performed in a normotensive rat model of endotoxemia, tests the hypotheses that endotoxemia impairs renal microvascular PO2 (microPO2) and oxygen consumption (VO2,ren), that endotoxemia is associated with a diminished kidney function, that fluid resuscitation can restore microPO2, VO2,ren and kidney function, and that colloids are more effective than crystalloids. METHODS: Male Wistar rats received a one-hour intravenous infusion of lipopolysaccharide, followed by resuscitation with HES130/0.4 (Voluven), HES200/0.5 (HES-STERIL 6%) or Ringer's lactate. The renal microPO2 in the cortex and medulla and the renal venous PO2 were measured by a recently published phosphorescence lifetime technique. RESULTS: Endotoxemia induced a reduction in renal blood flow and anuria, while the renal microPO2 and VO2,ren remained relatively unchanged. Resuscitation restored renal blood flow, renal oxygen delivery and kidney function to baseline values, and was associated with oxygen redistribution showing different patterns for the different compounds used. HES200/0.5 and Ringer's lactate increased the VO2,ren, in contrast to HES130/0.4. CONCLUSION: The loss of kidney function during endotoxemia could not be explained by an oxygen deficiency. Renal oxygen redistribution could for the first time be demonstrated during fluid resuscitation. HES130/0.4 had no influence on the VO2,ren and restored renal function with the least increase in the amount of renal work.

Effect of synthetic colloids on major histocompatibility complex class II expression.

STUDY OBJECTIVE: Synthetic colloids are used for perioperative fluid management. We hypothesized that their use may be associated with changes in major histocompatibility complex (MHC) class II expression. This could affect patients' morbidity and mortality during clinical intervention. SETTING: University research laboratory. SUBJECTS: Whole blood samples from healthy volunteers. INTERVENTIONS: Whole blood samples from healthy volunteers (n = 6) were incubated with different concentrations of hydroxyethyl starch (HES) from maize and potato (pHES), dextran, and polygelin (gelatine) for 24 hours with or without 100 U/mL human interferon gamma (IFN-gamma; stimulus for MHC class II expression). The expression of human leukocyte antigen (HLA): HLA-DR, HLA-DQ, and HLA-DP was detected simultaneously by a fluoresceinisothiocyanate (FITC)-labeled antibody and analyzed by flow cytometry on lymphocytes and monocytes. MEASUREMENTS AND MAIN RESULTS: Hydroxyethyl starch, pHES, and dextran induced a significant increase in HLA expression. The induction of MHC class II was independent of the structure (50 mg/mL: control, 8.7+/-1.4%; HES, 28 +/- 9.7%; pHES, 29.8 +/- 11.7%; and dextran, 50.2 +/- 8.1%). In contrast, polygelin increased HLA expression only at the highest concentration of gelatine (5 mg/mL, 7.8 +/- 1%; 50 mg/mL, 7.6 +/- 0.8%; 100 mg/mL, 7.3 +/- 1%; 200 mg/mL,16.2 +/- 2.3%). The addition of IFN-gamma decreased HLA expression in presence of highest concentration of HES and dextran. CONCLUSION: In an ex vivo laboratory setting, we demonstrate that high concentrations of plasma expanders are associated with increased HLA expression on lymphocytes and monocytes. However, further in vivo studies are necessary to demonstrate the clinical significance of this observation.

A fish oil emulsion used for parenteral nutrition attenuates monocyte-endothelial interactions under flow.

Monocyte adhesion contributes to perfusion abnormalities, tissue damage, and activation of the coagulation system seen during trauma, shock, or overwhelming inflammation. This study was performed to determine whether an intravenous fish oil emulsion used for parenteral nutrition attenuates monocyte-endothelial interactions under flow and reduces procoagulant activity, measured as tissue factor (TF) expression on adherent monocytes in vitro. Endothelial cell monolayers were incubated with either an intravenous fish oil emulsion or a conventional omega-6 lipid emulsion at 0.05 to 1 mg/ml for 24 h. Six hours following activation with TNFalpha (25 ng/ml), expression of endothelial cell adhesion molecules was measured by flow cytometry. Adhesion of isolated monocytes to pretreated endothelium was examined in a parallel plate flow chamber at a shear stress of 1.5 dynes/cm2. Following perfusion, the cells were cocultured for an additional 4 h and TF expression on monocytes was determined by flow cytometry. In contrast to omega-6 lipids, fish oil down-regulated E-selectin, intercellular adhesion molecule-1, and vascular cell adhesion molecule-1 in a dose-dependent manner. P-selectin, however, remained unchanged. In addition, firm adhesion was reduced to 54%, whereas rolling interactions remained unchanged. Fish oil exhibited no effect on the TF expression on cocultured monocytes. We conclude that intravenous fish oil emulsions reduce both endothelial cell adhesion molecule expression and monocyte adhesion. However, under postcapillary flow conditions, rolling interactions via P-selectin remain unaltered. The functional importance of this effect is illustrated by the corresponding upregulation of TF in response to residual monocyte-endothelial interactions.

Effects of magnetic cell separation on monocyte adhesion to endothelial cells under flow.

Studies on monocyte adhesion are frequently limited by spontaneous changes of CD11b and CD62L during cell purification. Most isolation protocols for flow cytometric analysis that overcome this problem cannot be used when large numbers of living cells are needed for functional adhesion assays. This study investigated whether magnetic cell separation of monocytes with a paramagnetic bead against CD33 is a feasible method combining high yield with a low degree of spontaneous activation. As determined by flow cytometry, isolation of magnetically tagged monocytes at 4 degrees C did not alter the expression of CD11b and CD62L when compared to whole blood controls. Warming the cells slowly to room temperature immediately before starting the adhesion assay in a parallel plate flow chamber at 37 degrees C prevented further upregulation of adhesion molecules due to rewarming. When adhesion of magnetically tagged monocytes was compared with untouched monocytes that had been isolated via depletion of contaminating leukocytes, videomicroscopy showed that labelling CD33 neither affected rolling nor firm adhesion to human umbilical venous endothelial cells under flow. Finally, the subsequent upregulation of tissue factor expression on adherent monocytes indicates that magnetically separated monocytes responded properly to activating stimuli during cell adhesion. We conclude that magnetic cell separation via CD33 represents a feasible method for cell separation whenever large numbers of non-activated monocytes are needed for adhesion assays under flow.

Effective silencing of adhesion molecules on venous endothelial cells for protection of venous bypass grafts.

OBJECTIVE: The patency of venous conduits after aortocoronary bypass grafting is still not satisfactory and needs to be improved. Atherosclerotic alterations mediated by adhesion molecules triggering the transmigration of leukocytes are regarded as one of the major causes for venous graft failure. This study deals with short interfering RNA (siRNA)-mediated silencing of adhesion molecule expression on venous endothelial cells, which could lead to a new therapeutic strategy, resulting in improved patency rates by inhibiting early graft alterations. METHODS: Primary human venous endothelial cells (HVECs) were cultured in a newly developed perfusion model and subsequently transfected with specific siRNAs targeting three different adhesion molecules (the E-selectin (ESELE), the intercellular adhesion molecule 1 (ICAM-1), and the vascular adhesion molecule (VCAM-1)), followed by stimulation with tumor necrosis factor-alpha (TNF-α). Isolated leukocytes were perfused under physiological shear stress conditions, and their attachment to HVEC after single and triple transfection was quantified. RESULTS: siRNA transfection effectively knocks down adhesion molecule expression on venous endothelial cells, which subsequently reduces leukocyte attachment. Leukocyte adhesion to activated HVEC was significantly reduced after transfection by specific siRNAs in each case compared to the controls (p<0.05). Transfection with a mixture of all three siRNA sequences improved this effect even more (p<0.05). CONCLUSION: For the first time, a functional protection of HUEC in a model simulating physiologic vascular conditions by using nonviral transfection of the cells in a setup with high relevance for clinical applicability was demonstrated. Therefore, siRNA transfection of bypass material may develop into a new therapeutic option to improve the quality of venous graft material in the future.

Activity of the lipoxygenase inhibitor 1-phenyl-3-pyrazolidinone (phenidone) and derivatives on the inhibition of adhesion molecule expression on human umbilical vascular endothelial cells.

Leukocyte adhesion contributes to perfusion abnormalities and tissue damage during trauma, shock or overwhelming inflammation. This study was performed to determine whether the lipoxygenase inhibitor phenidone and derivatives decrease the expression of adhesion molecules on tumor necrosis factor-alpha (TNF-alpha) stimulated endothelial cells and attenuate leukocyte-endothelial interactions under flow in vitro. TNF-alpha stimulated human umbilical venous endothelial cells (HUVECs) were incubated with phenidone, 4-methyl-phenidone, 4-4-dimethyl-phenidone, 5-methyl-phenidone, 5-phenyl-phenidone, and 5-methyl-1,(2,5-di-chloro-phenyl)-3-pyrazolidone. We tested the inhibition of adhesion molecule expression at different inhibitor concentrations before, during, and after the stimulation of HUVECs. The inhibition of endothelial cell expression on HUVECs was measured by flow cytometry. Rolling and firm adhesion of leukocytes to pretreated endothelium was examined in a parallel plate flow chamber. Phenidone inhibited the expression of intercellular adhesion molecule-1, vascular cell adhesion molecule-1, and endothelial-leukocyte adhesion molecule-1 on HUVECs when added prior to HUVEC stimulation. The inhibitory effect of phenidone was still observed when added simultaneously, but not when added after HUVEC stimulation. 4-4-dimethyl-phenidone and 5-phenyl-phenidone inhibited the expression of adhesion molecules more effectively than phenidone. The attenuation of leukocyte rolling under flow conditions was also significantly more effective with 4-4-dimethyl-phenidone than with phenidone. Lipoxygenase inhibitors might be of therapeutically interest for the treatment of overwhelming systemic inflammation during shock, trauma, and sepsis.

A pilot open-label study of the efficacy of subanesthetic isomeric S(+)-ketamine in refractory CRPS patients.

OBJECTIVE: Complex regional pain syndrome (CRPS) is a severe neuropathic pain state that is often disproportionate to the initial trauma. Associated features are autonomic dysregulation, swelling, motor dysfunction, and trophic changes to varying degrees. Despite a multitude of treatment modalities, a subgroup of CRPS patients remain refractory to all standard therapies. In these patients, the disease may spread extraterritorially, which results in severe disability. A critical involvement of N-methyl-D-aspartate receptors (NMDARs) has been demonstrated both clinically and by animal experimentation. NMDA antagonists may be effective in many neuropathic pain states. In long-standing, generalized CRPS, we investigated the effects of S(+)-ketamine on pain relief and somatosensory features, assessed by quantitative sensory testing (QST). METHODS: Four refractory CRPS patients received continous S(+)-ketamine-infusions, gradually titrated (50 mg/day-500 mg/day) over a 10-day period. Pain intensities (average, peak, and least pain) and side effects were rated on visual analogue scales, during a 4-day baseline, over 10 treatment days, and 2 days following treatment. QST (thermo-, mechanical detection, and pain thresholds) was analyzed at baseline and following treatment. RESULTS: Subanesthetic S(+)-ketamine showed no reduction of pain and effected no change in thermo- and mechanical detection or pain thresholds. This procedure caused no relevant side effects. The lack of therapeutic response in the first four patients led to termination of this pilot study. CONCLUSION: S(+)-ketamine can be gradually titrated to large doses (500 mg/day) without clinically relevant side effects. There was no pain relief or change in QST measurements in this series of long-standing severe CRPS patients.

Acute decrease in renal microvascular PO2 during acute normovolemic hemodilution.

Large differences in the tolerance of organ systems to conditions of decreased O(2) delivery such as hemodilution exist. The kidney receives approximately 25% of the cardiac output and O(2) delivery is in excess of the oxygen demand under normal circumstances. In a rat model of acute normovolemic hemodilution (ANH), we studied the effect of reduced hematocrit on renal regional and microvascular oxygenation. Experiments were performed in 12 anesthetized male Wistar rats. Six animals underwent four steps of ANH (hematocrit 25, 15, 10, and <10%). Six animals served as time-matched controls. Systemic and renal hemodynamic and oxygenation parameters were monitored. Renal cortical (c) and outer medullary (m) microvascular PO(2) (microPO(2)) and the renal venous PO(2) (P(rv)O(2)) were continuously measured by oxygen-dependent quenching of phosphorescence. Despite a significant increase in renal blood flow in the first two steps of ANH, cmicroPO(2) and mmicroPO(2) dropped immediately. From the first step onward oxygen consumption (VO(2(ren))) became dependent on oxygen delivery (DO(2(ren))). With a progressive decrease in hematocrit, a significant correlation between microPO(2) and VO(2(ren)) could be observed, as well as a PO(2) gap between microPO(2) and P(rv)O(2). Furthermore, there was a high correlation between VO(2(ren)) and RBF over a wide range of flows. In conclusion, the oxygen supply to the renal tissue is becoming critical already in an early stage of ANH due to the combination of increased VO(2(ren)), decreased DO(2(ren)), and intrarenal O(2) shunt. This has clinical relevance as recent publications reporting that hemodilution during surgery forms a risk factor for postoperative renal dysfunction.

Dose-dependent influence of barbiturates but not of propofol on human leukocyte phagocytosis of viable Staphylococcus aureus.

OBJECTIVE: Deep sedation with barbiturates or propofol is a standard therapy for patients with critically elevated intracranial pressure. Such patients are prone to infectious complications, especially to pneumonias, which are most commonly caused by Staphylococcus aureus. Although various immunomodulatory effects of barbiturates have been described in vitro, their influence on the phagocytosis of viable S. aureus has yet to be investigated. Therefore, we examined the effects of thiopentone, methohexitone, and propofol on the phagocytosis of viable S. aureus. DESIGN: Laboratory study. SETTING: University laboratory. PATIENTS: Ten healthy volunteers aged 32.5 +/- 7 yrs. INTERVENTIONS: Blood sampling. MEASUREMENTS AND MAIN RESULTS: Whole blood samples were preincubated with different concentrations of thiopentone, methohexitone, and propofol, which is an isopropylphenol derivate. After viable S. aureus was added, phagocytosis was stopped at different time points. Leukocytes were then stained with monoclonal antibodies for flow cytometric analysis of granulocyte recruitment (ratio of ingesting granulocytes) and phagocytosis activity (fluorescence intensity of ingested bacteria). Both barbiturates inhibited granulocyte recruitment and phagocytosis activity in a dose-dependent manner, whereas propofol did not affect any of the investigated variables. At concentrations higher than 7.6 x 10(-3) M (for thiopentone, p < .008) and 1.1 x 10(-3) M (for methohexitone, p < .04), granulocyte recruitment and phagocytosis activity were significantly inhibited. The calculated inhibitory concentrations (IC50) of thiopentone for granulocyte recruitment and for phagocytosis activity were 1.3 x 10(-2) M and 1.1 x 10(-2) M, respectively. The corresponding values for methohexitone were 3.6 x 10(-3) M and 1.1 x 10(-3) M. CONCLUSIONS: Our in vitro model points at substantially different effects of barbiturates and propofol on phagocytosis of S. aureus, which is one of the most important pathogens in patients who need neuroprotective therapy. The inhibitory effects of both barbiturates demonstrate a strong dose-dependency, with more pronounced effects for methohexitone. Impairment of phagocytosis activity was more pronounced than granulocyte recruitment.

Effects of intraoperative blood salvage on leukocyte recruitment to the endothelium.

BACKGROUND: The contamination of salvaged wound blood with activated leukocytes has been suspected to play a role in leukocyte-mediated tissue injury by increased adhesion to the endothelium. To verify this hypothesis, the authors performed a clinical study to examine the effects of blood salvage on leukocyte-endothelial interactions. METHODS: Expression of L-selectin, CD18, and CD11b and leukocyte adhesion to activated endothelium from human umbilical veins were measured in 25 patients undergoing major orthopedic surgery. Adhesion of fluorescently labeled leukocytes was examined in a flow chamber at shear rates of 50-1,600 s. Comparisons were made between samples from venous blood and from processed salvaged wound blood (SWB). RESULTS: At 30% hematocrit, SWB contained 2,162 +/- 147 leukocytes/microl. In comparison with venous blood, CD11b was up-regulated in SWB 1.3- to 3.6-fold on monocytes and neutrophils, whereas L-selectin and CD18 decreased on monocytes by 53% and 15%, respectively (P < 0.05). Despite up-regulation of CD11b, firm adhesion was significantly reduced by 74-76% in SWB. Rolling fractions and rolling velocities were significantly higher in SWB, and their relation to shear rate was markedly altered (P < 0.01). In addition, adherent leukocytes from SWB were significantly less resistant to increments of shear rate than leukocytes from venous blood (P < 0.01). CONCLUSIONS: Despite up-regulated CD11b, integrin-mediated adhesion is markedly impaired in salvaged blood. Therefore, the effect of blood salvage cannot be predicted from cell surface expression but rather from functional assays. The former hypothesis, that leukocytes from SWB aggravate leukocyte-mediated tissue injury by increased adhesion, may not be as great a concern as previously suggested.

Aortic dissection mimicking subarachnoidal hemorrhage.

In this report we describe a comatose patient with proximal aortic dissection who presented with the signs of subarachnoidal hemorrhage. Shortly before losing consciousness, the patient complained of an excruciating headache. Upon initial examination, neck stiffness and opisthotonos were present. The cardiovascular examination, chest radiograph, and cerebral computed tomography were normal. Eight hours later, the aortic dissection was verified by a thoracic computed tomography. This case shows that aortic dissection, which causes severe pain and possibly transient malperfusion of the carotid arteries, may present with the misleading signs of subarachnoidal hemorrhage but without classical symptoms of aortic syndromes.

Synthetic colloids attenuate leukocyte-endothelial interactions by inhibition of integrin function.

BACKGROUND: It has been suspected that synthetic colloids may interfere with leukocyte adhesion by down-regulation of endothelial cell adhesion molecules. Although inhibition of endothelial inflammation might reduce leukocyte-related tissue injury, the same mechanism may be detrimental for host defense during severe infection. Regarding the widespread use of colloids, the authors performed a laboratory investigation to determine the mechanisms by which synthetic colloids interfere with leukocyte-endothelial interactions. METHODS: Adhesion molecule expression on native and cytokine-activated endothelium from umbilical veins was measured after pretreatment with gelatin and various preparations of dextran or hydroxyethyl starch. Inhibition of neutrophil adhesion to activated endothelium was examined in a flow chamber by perfusion of untreated and colloid-treated neutrophils over colloid-pretreated endothelium at 2 dyn/cm. Comparisons were made between untreated controls, colloid-pretreated endothelium, and colloid-cotreated neutrophils. RESULTS: Intercellular adhesion molecule 1, vascular cell adhesion molecule 1, E-selectin, and P-selectin were not attenuated by any colloid. Accordingly, colloid pretreatment of endothelium alone did not reduce neutrophil adhesion. In contrast, when neutrophils were cotreated by addition of colloids to the perfusate immediately before perfusion, adhesion decreased by 31-51% (P < 0.05) regardless of the colloid type. As indicated by the twofold increased rolling fractions, this reduction was due to an inhibition of neutrophil integrins. CONCLUSIONS: This study shows that synthetic colloids inhibit neutrophil adhesion by a neutrophil-dependent mechanism rather than interfering with endothelial cell activation. This suggests that inhibition of leukocyte sequestration by volume support is a common and transient phenomenon depending on the colloid concentration in plasma.

The effects of fresh frozen plasma on neutrophil-endothelial interactions.

UNLABELLED: Leukocyte adhesion to endothelial cells contributes to microcirculatory disturbances during severe shock syndromes. Whereas certain plasma expanders inhibit leukocyte adhesion, contaminants of plasma protein solutions upregulate endothelial cell adhesion molecules in certain cases. We performed this study to determine whether fresh frozen plasma (FFP) affects neutrophil-endothelial interactions in cocultures of neutrophils and human umbilical vein endothelial cells (HUVEC) in vitro. HUVEC (n = 9) were incubated with either 20% FFP or 20% serum in medium for 6 h. Expression of E-selectin, intercellular adhesion molecule 1, and vascular cell adhesion molecule-1 was induced by tumor necrosis factor alpha (0.5 ng/mL for 4 h) and measured by flow cytometry. Neutrophil adhesion was examined in a parallel plate flow chamber in which isolated neutrophils were perfused over pretreated HUVEC under postcapillary flow conditions. Incubation with FFP decreased E-selectin and intercellular adhesion molecule 1 on activated HUVEC by 28% and 22%, respectively (P < or = 0.01; analysis of covariance). Consequently, neutrophil adhesion decreased by 20%-41% in FFP-treated cocultures (n = 4; P < or = 0.01; paired Student's t-test). We conclude that FFP attenuates the inflammatory response of endothelial cells with regard to neutrophil-endothelial interactions. Because the composition of patients' plasma is affected not only by transfusion, but more frequently by shock treatment with IV fluids, plasma dilution in critically ill patients could be important. IMPLICATIONS: During shock, fluid administration leads to a massive dilution of plasma. Apart from maintaining hemodynamics, this might affect tissue damage by influencing leukocyte accumulation in the microvasculature. Using endothelial cells, isolated neutrophils, and a parallel plate flow chamber, we studied the effects of fresh frozen plasma on neutrophil-endothelial interactions.