Falco Hietbrink

Functional heterogeneity and differential priming of circulating neutrophils in human experimental endotoxemia

Neutrophils play an important role in host defense. However, deregulation of neutrophils contributes to tissue damage in severe systemic inflammation. In contrast to complications mediated by an overactive neutrophil compartment, severe systemic inflammation is a risk factor for development of immune suppression and as a result, infectious complications. The role of neutrophils in this clinical paradox is poorly understood, and in this study, we tested whether this paradox could be explained by distinct neutrophil subsets and their functionality. We studied the circulating neutrophil compartment immediately after induction of systemic inflammation by administering 2 ng/kg Escherichia coli LPS i.v. to healthy volunteers. Neutrophils were phenotyped by expression of membrane receptors visualized by flow cytometry, capacity to interact with fluorescently labeled microbes, and activation of the NADPH‐oxidase by oxidation of Amplex Red and dihydrorhodamine. After induction of systemic inflammation, expression of membrane receptors on neutrophils, such as CXCR1 and ‐2 (IL‐8Rs), C5aR, FcγRII, and TLR4, was decreased. Neutrophils were also refractory to fMLF‐induced up‐regulation of membrane receptors, and suppression of antimicrobial function was shown by decreased interaction with Staphylococcus epidermis. Simultaneously, activation of circulating neutrophils was demonstrated by a threefold increase in release of ROS. The paradoxical phenotype can be explained by the selective priming of the respiratory burst. In contrast, newly released, CD16dim banded neutrophils display decreased antimicrobial function. We conclude that systemic inflammation leads to a functionally heterogeneous neutrophil compartment, in which newly released refractory neutrophils can cause susceptibility to infections, and activated, differentiated neutrophils can mediate tissue damage.

Systemic inflammation increases intestinal permeability during experimental human endotoxemia.

Although the gut is often considered the motor of sepsis, the relation between systemic inflammation and intestinal permeability in humans is not clear. We analyzed intestinal permeability during experimental endotoxemia in humans. Before and during experimental endotoxemia (Escherichia coli LPS, 2 ng/kg), using polyethylene glycol (PEG) as a permeability marker, intestinal permeability was analyzed in 14 healthy subjects. Enterocyte damage was determined by intestinal fatty acid binding protein. Endotoxemia induced an inflammatory response. Urinary PEGs 1,500 and 4,000 recovery increased from 38.8 ± 6.3 to 63.1 ± 12.5 and from 0.58 ± 0.31 to 3.11 ± 0.93 mg, respectively (P < 0.05). Intestinal fatty acid binding protein excretion was not affected by endotoxemia. The peak serum IL-10 concentrations correlated with the increase in PEG 1,500 recovery (r = 0.48, P = 0.027). Systemic inflammation results in an increased intestinal permeability. The increase in intestinal permeability is most likely caused by inflammation-induced paracellular permeability, rather than ischemia-mediated enterocyte damage.

Kinetics of the innate immune response after trauma: implications for the development of late onset sepsis.

Background Severe trauma is characterized by a pronounced immunologic response with both proinflammatory and anti-inflammatory characteristics. The clinical course of trauma patients is often complicated by late-onset (>5 days) sepsis. However, the underlying mechanisms remain poorly defined. Here we studied the kinetics of systemic activation of neutrophils and monocytes following injury in trauma patients in the context of development of sepsis. Methods Thirty-six severely injured patients were included and followed up for 10 days in the intensive care unit. Serial blood samples were taken daily and analyzed ex vivo for activation of PMNs (polymorphonuclear leukocytes, i.e., neutrophils) (expression MAC-1 [macrophage-1 antigen], CXCR-1 [CXC-chemokine receptor 1], Fc&ggr;RII) and expression of human leukocyte antigen DR (HLA-DR) on monocytes. In addition, the functionality of PMNs was measured by activation of the respiratory burst and responsiveness for the innate immune stimulus N-formyl-methionyl-leucyl-phenylalanine (fMLF). Results Ten of 36 patients developed septic shock, invariably 8 to 10 days after admission. CXCR-1 and fMLF-induced active Fc&ggr;RII showed a gradual decrease in expression before clinical signs of septic shock. Patients who developed septic shock demonstrated a statistically significantly decreased fMLF-induced active Fc&ggr;RII (P = 0.009) at initial presentation. An immediate decreased percentage of HLA-DR–positive monocytes could be contributed to an increased absolute number of HLA-DR–negative monocytes. Conclusions Phenotyping blood PMNs enables identification of the kinetics and magnitude of the initial systemic inflammatory response after injury. The decreased functionality of PMNs and monocytes reaches its minimum before the development of sepsis and could be an important contributing factor. This could support the early identification of patients at risk.

Aberrant regulation of polymorphonuclear phagocyte responsiveness in multitrauma patients.

ABSTRACT A systemic inflammatory response often follows severe trauma. Priming (preactivation) of polymorphonuclear phagocytes (PMNs) is an essential first step in the processes that lead to damage caused by the systemic activation of innate immune response. Until recently, priming could only accurately be measured by functional assays, which require isolation of cells, thereby potentially inducing artificial activation. The aim of this study was to identify primed PMNs in response to trauma by using a whole blood analysis with a broad detection range. Twenty-two trauma patients were analyzed for PMN priming with novel developed antibodies recognizing priming epitopes by flow cytometric analysis. Expression of priming epitopes on PMNs was analyzed with respect to time, injury, and disease severity. Expression of priming epitopes in the circulation was compared with expression profiles of PMNs obtained from lung fluid. Fourteen healthy volunteers served as controls. Expression of priming epitopes on peripheral blood PMNs of injured patients was similar, as found in healthy controls, whereas highly primed cells were found in the lung fluid of injured patients (increase of >50 times as compared with peripheral blood cells). In fact, the responsiveness of PMNs toward the bacteria-derived stimulus N-formyl-methionyl-leucyl-phenylalanine was markedly decreased in trauma patients. Lack of expression of priming epitopes and the unresponsiveness to N-formyl-methionyl-leucyl-phenylalanine demonstrates the presence of partially refractory cells in the circulation of trauma patients. An increased expression of epitopes found on pulmonary PMNs suggests that optimal (pre)activation of these cells only occurs in the tissues.

Weight-Bearing and Mobilization in the Postoperative Care of Ankle Fractures: A Systematic Review and Meta-Analysis of Randomized Controlled Trials and Cohort Studies

Purpose To determine the effectiveness and safety of interventions used for rehabilitation after open reduction and internal fixation of ankle fractures. Methods A systematic review and meta-analysis was performed using both randomized trials and cohort studies. The effect of mobilization, weight-bearing, and unprotected weight-bearing as tolerated on postoperative recovery was compared using the Olerud Molander score, return to work/daily activities, and the rate of complications. Results A total of 25 articles were included. Ankle exercises resulted in earlier return to work and/or daily activities compared to immobilization (mean difference (MD) -20.76 days; 95% confidence interval (CI) -40.02 to -1.50). There was no difference in the rate of complications between exercises and immobilization (risk ratio (RR) 1.22; 95% CI 0.60 to 2.45) or between early and late weight-bearing (RR 1.26; 95%CI 0.56 to 2.85). Interpretation Results of this meta-analysis show that following ankle surgery, 1) active exercises accelerate return to work and daily activities compared to immobilization, 2) early weight-bearing tends to accelerate return to work and daily activities compared to late weight-bearing. Active exercises in combination with immediate weight-bearing may be a safe option.

Modulation of the innate immune response after trauma visualised by a change in functional PMN phenotype.

BACKGROUND Acute Respiratory Distress Syndrome (ARDS) is a frequent and severe complication after trauma, caused by an excessive inflammatory response mediated by polymorphonuclear granulocytes (PMNs). It was previously demonstrated that patients with activated PMNs in the lungs have PMNs in the peripheral circulation with a reduced active FcgammaRII up-regulating capacity. We tested the hypothesis that a correlation exists between the severity of inflammation and the extent of decreased responsiveness of active FcgammaRII on circulating PMNs, as a sign of altered immunological capacity. METHODS Fifty-two patients were included and injury severity was assessed by clinical injury severity scores and base deficit. Symptoms and signs of inflammation were recorded on a daily basis and fMLP-induced active FcgammaRII on PMNs was assessed by FACS analysis within 24h after injury. Results were compared with 10, age matched healthy controls. RESULTS The baseline PMN membrane expression of Mac-1/CD11b and active FcgammaRII/CD32 did not correlate with injury severity. Levels of the acute phase protein Interleukin 6 (IL-6) correlated significantly with injury severity, indicating that a range in severity of the inflammatory response was present in the studied population. A statistically significant correlation between the PMN responsiveness towards the bacterial derived peptide fMLP of active FcgammaRII and injury severity was demonstrated. In addition, decreasing responsiveness of active FcgammaRII on PMNs was found in patients who developed systemic inflammatory response syndrome (SIRS) or acute lung injury (ALI)/ARDS. CONCLUSIONS The extent of the sustained injury and the subsequent cellular innate immune response is reflected by changes in a functional PMN phenotype of fMLP-induced active FcgammaRII in the peripheral blood.

Evaluation of hematological parameters on admission for the prediction of 7-day in-hospital mortality in a large trauma cohort

Abstract Background: We evaluated the complete blood count (CBC) for the prediction of 7-day in-hospital mortality in a large adult trauma cohort. Methods: We conducted an analysis of two prospectively collected databases on 1673 patients aged ≥18 years admitted to a level I trauma center (2005–2007). Comparisons between survivors and non-survivors within 7 days after admission and between single and multiple trauma patients were made. Discriminative performance for 7-day in-hospital mortality was assessed using the area under the receiver operating characteristic curve (ROC). Logistic regression was used to identify independent prognostic factors for 7-day in-hospital mortality. Results: Comparison between survivors and non-survivors showed significant differences in white blood cell (WBC) count, absolute neutrophil count, segmented neutrophil count and most red blood cell (RBC) and platelet indices. Comparison between single and multiple trauma patients showed significant differences for WBC count and differential count and most RBC and platelet indices. Among the CBC parameters, RBC count (ROC=0.748), hemoglobin concentration (Hb) (ROC=0.734), hematocrit (Ht) (ROC=0.726), platelet count (PLT) (ROC=0.684) and plateletcrit (PCT) (ROC=0.696) showed the highest ROC. Using logistic regression we showed that RBC count, Hb, Ht, PLT and PCT were predictors of 7-day in-hospital mortality independently of patients age, injury severity and initial physiological state. Conclusions: Significant differences in CBC parameters were found between survivors and non-survivors and between patients with single and multiple trauma, but most of the CBC parameters demonstrated poor to moderate pre dictive ability for 7-day in-hospital mortality in adult trauma patients. Routine laboratory workup of trauma patients should be performed as treatment guidance. However, prognostic value of initial hematological parameters remains limited.

Plate fixation or intramedullary fixation for midshaft clavicle fractures: a systematic review and meta-analysis of randomized controlled trials and observational studies.

BACKGROUND The last decade has shown a shift toward operative treatment of a subset of midshaft clavicle fractures. However, it is unclear whether there are differences between plate fixation and intramedullary fixation regarding complications and functional outcome. The aim of this systematic review and meta-analysis was to compare plate fixation and intramedullary fixation for midshaft clavicle fractures. METHODS The Medline, Embase, and Cochrane databases were searched for both randomized controlled trials and observational studies. The methodologic quality of all included studies was assessed using the Methodological Index for Non-Randomized Studies. RESULTS Twenty studies were included. Ten of the 20 included studies used a fracture classification. Seven of these studies reported exclusion of patients with comminuted fractures. No difference in the total re-intervention rate was found (odds ratio [OR], 1.21; 95% confidence interval [CI], 0.71 to 2.04). Major re-interventions occurred more often after plate fixation (OR, 1.88; 95% CI, 1.02 to 3.46). The mean implant removal rates were 38% after plate fixation and 73% after intramedullary fixation. Re-fracture after implant removal occurred more often after plate fixation (OR, 3.42; 95% CI, 1.12 to 10.42). The Constant-Murley scores showed no differences at both short term (mean difference, -1.18; 95% CI, -13.41 to 11.05) and long term (mean difference, 0.15; 95% CI, -1.57 to 1.87). No differences were observed regarding nonunion (OR, 1.50; 95% CI, 0.82 to 2.75). The rate of infections showed no differences when outlier studies were excluded (OR, 1.54; 95% CI, 0.88 to 2.69). CONCLUSION Major re-intervention and re-fracture after implant removal occurred more frequently after plate fixation of non-comminuted, displaced midshaft clavicle fractures. No differences in terms of function and nonunion between plate fixation and intramedullary fixation were observed.

Initial assessment of chest X-ray in thoracic trauma patients: Awareness of specific injuries

AIM To compare the reported injuries on initial assessment of the chest X-ray (CXR) in thoracic trauma patients to a second read performed by a dedicated trauma radiologist. METHODS By retrospective analysis of a prospective database, 712 patients with an injury to the chest admitted to the University Medical Center Utrecht were studied. All patients with a CXR were included in the study. Every CXR was re-evaluated by a trauma radiologist, who was blinded for the initial results. The findings of the trauma radiologist regarding rib fractures, pneumothoraces, hemothoraces and lung contusions were compared with the initial reports from the trauma team, derived from the original patient files. RESULTS A total of 516 patients with both thorax trauma and an initial CXR were included in the study. After re-evaluation of the initial CXR significantly more lung contusions (53.3% vs 34.1%, P < 0.001), hemothoraces (17.8% vs 11.0%, P < 0.001) and pneumothoraces (34.4% vs 26.4%, P < 0.001) were detected. During initial assessment significantly more rib fractures were reported (69.8% vs 62.3%, P < 0.001). CONCLUSION During the initial assessment of a CXR from trauma patients in the emergency department, a significant number of treatment-dictating injuries are missed. More awareness for these specific injuries is needed.

Surgical Versus Nonsurgical Treatment for Midshaft Clavicle Fractures in Patients Aged 16 Years and Older: A Systematic Review, Meta-analysis, and Comparison of Randomized Controlled Trials and Observational Studies

Background: There is no consensus on the choice of treatment of midshaft clavicle fractures (MCFs). Purpose: The aims of this systematic review and meta-analysis were (1) to compare fracture healing disorders and functional outcomes of surgical versus nonsurgical treatment of MCFs and (2) to compare effect estimates obtained from randomized controlled trials (RCTs) and observational studies. Study Design: Systematic review and meta-analysis. Methods: The PubMed/MEDLINE, Embase, CENTRAL, and CINAHL databases were searched for both RCTs and observational studies. Using the MINORS instrument, all included studies were assessed on their methodological quality. The primary outcome was a nonunion. Effects of surgical versus nonsurgical treatment were estimated using random-effects meta-analysis models. Results: A total of 20 studies were included, of which 8 were RCTs and 12 were observational studies including 1760 patients. Results were similar across the different study designs. A meta-analysis of 19 studies revealed that nonunions were significantly less common after surgical treatment than after nonsurgical treatment (odds ratio [OR], 0.18 [95% CI, 0.10-0.33]). The risk of malunions did not differ between surgical and nonsurgical treatment (OR, 0.38 [95% CI, 0.12-1.19]). Both the long-term Disabilities of the Arm, Shoulder and Hand (DASH) and Constant-Murley scores favored surgical treatment (DASH: mean difference [MD], −2.04 [95% CI, −3.56 to −0.52]; Constant-Murley: MD, 3.23 [95% CI, 1.52 to 4.95]). No differences were observed regarding revision surgery (OR, 0.85 [95% CI, 0.42-1.73]). Including only high-quality studies, both the number of malunions and days to return to work show significant differences in favor of surgical treatment (malunions: OR, 0.26 [95% CI, 0.07 to 0.92]; return to work: MD, −8.64 [95% CI, −16.22 to −1.05]). Conclusion: This meta-analysis of high-quality studies showed that surgical treatment of MCFs results in fewer nonunions, fewer malunions, and an accelerated return to work compared with nonsurgical treatment. A meta-analysis of surgical treatments need not be restricted to randomized trials, provided that the included observational studies are of high quality.