Klebsiella pneumoniae flocculation dynamics.

The bacterial pathogen Klebsiella pneumoniae is a cause of community- and hospital-acquired lung, urinary tract and blood stream infections. It is a common contaminant of indwelling catheters and it is theorized in that context that systemic infection follows shedding of aggregates off of surface-adherent biofilm colonies. In an effort to better understand bacterial proliferation in the host bloodstream, we develop a PDE model for the flocculation dynamics of Klebsiella pneumoniae in suspension. Existence and uniqueness results are provided, as well as a brief description of the numerical approximation scheme. We generate artificial data and illustrate the requirements to accurately identify proliferation, aggregation, and fragmentation of flocs in the experimental domain of interest.

Intracerebral hemorrhage in complement C3-deficient mice.

The complement cascade is activated and contributes to brain damage after intracerebral hemorrhage (ICH). The present study investigated ICH-induced brain damage in complement C3-deficient mice. This study was divided into 2 parts. Male C3-deficient and C3-sufficient mice received an infusion of 30-microl autologous whole blood into the right basal ganglia. In the first part of our study, mice were killed 3 days later for brain water content measurement. Behavioral assessments including forelimb use asymmetry and corner turn tests were also preformed before and after ICH. In the second part of the study, brain heme oxygenase-1 (HO-1) was measured by Western blot analysis and immunohistochemistry 3 days after the infusion. We found that brain water content in the ipsilateral basal ganglia 3 days after ICH was less in C3-deficient mice compared to C3-sufficient mice (p < 0.05). The C3-deficient mice had reduced ICH-induced forelimb use asymmetry deficits compared with C3-sufficient mice (p < 0.05), although there was no significant difference in the corner turn test score. Western blot analysis showed that HO-1 contents were significantly lower in C3-deficient mice (day 3: 2024 +/- 560 vs. 5140 +/- 1151 pixels in the C3-sufficient mice, p < 0.05). We conclude that ICH causes less brain edema and behavioral deficits in complement C3-deficient mice. These results suggest that complement C3 is a key factor contributing to brain injury following ICH.

Brain edema after intracerebral hemorrhage: the effects of systemic complement depletion.

The complement cascade is activated after experimental intracerebral hemorrhage (ICH) and may play an important, role in edema formation. This study investigated the effects of systemic complement depletion on brain edema formation following ICH. Thirty-six pentobarbital-anesthetized Sprague-Dawley rats were used. Treatment animals were complement-depleted with cobra venom factor (CVF) while controls received an equal volume of saline injection (i.p.). In both treatment and control rats, autologous blood (100-microL) was infused stereotactically into the right basal ganglia. Rats were sacrificed one and three days later for brain water and ion content measurements and immunohistochemical studies. Immunohistochemistry was used to detect complement C3d, C5a, and C9. Western blot analysis was applied for C9 semiquantitation. Perihematomal brain edema was reduced by systemic complement depletion at one and three days. The water content of the cerebellum (a tissue distant from the hematoma site) was unaffected by complement depletion. Immunocytochemistry found complement depletion significantly reduced perihematomal C9 deposition, C3d production, and C5a positive cell accumulation. In conclusion, complement depletion by CVF attenuates brain edema in ICH perhaps by inhibiting the inflammatory response and membrane attack complex (MAC) formation.

Exposure to perflubron is associated with decreased Syk phosphorylation in human neutrophils.

Liquid ventilation with perflubron is associated with reduced neutrophil recruitment into the lung during acute injury. Perflubron also reduces chemotactic responses, the respiratory burst, and cytokine production in neutrophils and in alveolar macrophages in vitro. In the current studies, the effect of perflubron on neutrophil chemotaxis to formyl-Met-Leu-Phe (fMLP) and phagocytosis of opsonized sheep erythrocytes (EA) correlated with decreased phosphorylation of Syk, an important intracellular second messenger in pathways regulating neutrophil functional responses. Brief (5 min) exposure of neutrophils to perflubron resulted in a dose-dependent reduction in chemotaxis to fMLP and reduced phagocytosis of EA but no apparent morphological changes as seen by electron microscopy. Concurrently, there was a reduction in both total cytosolic tyrosine phosphorylation and Syk phosphorylation. Binding studies indicated that this effect was neither a result of impaired ligand-receptor affinity nor a change in the number of fMLP receptors available on the neutrophil surface. These results suggest that perflubron nonspecifically affects cellular activation as measured by tyrosine phosphorylation perhaps by interfering with transmembrane signal transduction.

A randomized comparison of helium-oxygen mixture (Heliox) and racemic epinephrine for the treatment of moderate to severe croup.

OBJECTIVE: To compare the additive effect of a helium-oxygen mixture (Heliox) or racemic epinephrine (RE) on croup scores (CSs) in children with moderate to severe croup treated with humidified oxygen and steroids. Design. A prospective, randomized, double-blind trial. SETTING: Emergency department and pediatric intensive care unit of an urban level I trauma center. PARTICIPANTS: Randomly assigned, consecutive children ages 6 months to 3 years presenting with moderate to severe croup (CS: >/=5). Interventions. After cool humidified oxygen and 0.6 mg/kg of intramuscular dexamethasone, patients were randomized to receive either Heliox or RE. Vital signs, oxygen saturation, and CSs were recorded at regular intervals. OUTCOME/ANALYSIS: Reductions in CSs were compared using repeated-measures analysis of variance. RESULTS: Thirty-three patients were enrolled. Three were excluded because of protocol violations, and 1 was excluded because of lack of documentation, leaving 29 patients for final analysis. The average age was 24.2 months, 20 were male (68.8%). Both Heliox and RE were associated with improvement in CSs over time. There were no significant differences in mean CS, oxygen saturation, respiratory rate, or heart rate between groups at baseline or at the end of the treatment period. CONCLUSION: In patients with moderate to severe croup, the administration of Heliox resulted in similar improvements in CS compared with patients given RE.

Systemic and lung physiological changes in rats after intravascular activation of complement.

Systemic complement activation has been noted in a variety of shock states, and there is growing evidence that, in addition to being proinflammatory effectors, products of complement activation contribute directly to generalized manifestations of shock, such as hypotension and acidosis. To study the effects of complement activation, we examined responses in rats to systemic activation of complement with cobra venom factor (CVF), including blood pressure, metabolic acidosis, changes in vascular permeability, and lung function. High doses of CVF produced circulatory collapse (mean arterial pressure = 110 +/- 16 and 35 +/- 9 mmHg in control and with CVF, respectively, P < 0.05), metabolic acidosis (HCO concentration = 27.8 +/- 1.7 and 9.6 +/- 3.4 meq/l in control and with CVF, respectively, P < 0.05), extravasation of albumin into the lung and gut, and modest arterial hypoxemia (PO2 = 486 +/- 51 and 201 +/- 36 Torr in control and during 100% O2 breathing, respectively, P < 0.05). Prior depletion of complement protected against these abnormalities. Other interventions, including neutrophil depletion and cyclooxygenase inhibition, prevented lung injury but had much less effect on systemic hemodynamics or gut permeability, suggesting that complement activation products induce injury by neutrophil- and cyclooxygenase-dependent pathways in the lung but not in the gut. These studies underscore the significant systemic abnormalities developing after systemic activation of complement.

Protective effects of anti-C5a peptide antibodies in experimental sepsis.

We evaluated antibodies to different peptide regions of rat C5a in the sepsis model of cecal ligation and puncture (CLP) for their protective effects in rats. Rabbit polyclonal antibodies were developed to the following peptide regions of rat C5a: amino-terminal region (A), residues 1-16; middle region (M), residues 17-36; and the carboxyl-terminal region (C), residues 58-77. With rat neutrophils, the chemotactic activity of rat C5a was significantly inhibited by antibodies with the following rank order: anti-C > anti-M >> anti-A. In vivo, antibodies to the M and C (but not A) regions of C5a were protective in experimental sepsis, as determined by survival over a 10-day period, in a dose-dependent manner. The relative protective efficacies of anti-C5a preparations (in descending order of efficacy) were anti-C > anti-M >> anti-A. In CLP rats, a delay in infusion of antibodies, which were injected at 6 or 12 h after CLP, still resulted in significant improvement in survival rates. These in vivo and in vitro data suggest that there are optimal targets on C5a for blockade during sepsis and that delayed infusion of anti-C5a antibody until after onset of clinical evidence of sepsis still provides protective effects.

Detrimental effects of complement activation in hemorrhagic shock.

The complement system has been implicated in early inflammatory events and a variety of shock states. In rats, we measured complement activation after hemorrhage and examined the hemodynamic and metabolic effects of complement depletion before injury and worsening of complement activation after hemorrhage and resuscitation [with a carboxypeptidase N inhibitor (CPNI), which blocks the clearance of C5a]. Rats were bled to a mean arterial pressure of 30 mmHg for 50 min and were then resuscitated for 2 h. Shock resulted in significant evidence of complement consumption, with serum hemolytic activity being reduced by 33% (P < 0.05). Complement depletion before injury did not affect hemorrhage volume (complement depleted = 28 +/- 1 ml/kg, complement intact = 29 +/- 1 ml/kg, P = 0.74) but improved postresuscitation mean arterial pressure by 37 mmHg (P < 0.05) and serum bicarbonate levels (complement depleted = 22 +/- 3 meq/ml, complement intact = 13 +/- 8 meq/ml, P < 0.05). Pretreatment with CPNI was lethal in 80% of treated animals vs. the untreated hemorrhaged group in which no deaths occurred (P < 0.05). In this model of hemorrhagic shock, complement activation appeared to contribute to progressive hypotension and metabolic acidosis seen after resuscitation. The lethality of CPNI during acute blood loss suggests that the anaphylatoxins are important in the pathophysiological events involved in hemorrhagic shock.

Systemic complement depletion diminishes perihematomal brain edema in rats.

BACKGROUND AND PURPOSE: The complement cascade is activated after experimental intracerebral hemorrhage (ICH). It remains unclear, however, whether depleting the complement system will improve injury resulting from ICH. This study investigated the effects of systemic complement depletion on brain edema formation after ICH. METHODS: Fifty-six pentobarbital-anesthetized Sprague-Dawley rats were used. Treatment animals were complement-depleted with cobra venom factor (CVF) (intraperitoneally). Control rats received an equal volume of saline injection (intraperitoneally). In both treatment and control rats, autologous blood (100 microL) was infused stereotaxically into the right basal ganglia. Rats were killed 2, 24, or 72 hours later for brain water, ion, and tumor necrosis factor-alpha (TNF-alpha) measurements, for Western blot analysis, and for immunohistochemical studies. Brain edema was quantitated by wet/dry weight. TNF-alpha levels were measured by enzyme-linked immunosorbent assay. Western blot analysis was applied for C9 semiquantification. Immunohistochemistry was used to detect complement C3d, C5a, C9, and myeloperoxidase. RESULTS: Perihematomal brain edema was reduced by systemic complement depletion at 24 hours (78.8+/-0.6% versus 81.5+/-0.8% in control, P:<0.01) and 72 hours (81.5+/-1.5% versus 83.6+/-0.9% in control, P:<0.05), while cerebellar water content was unaffected (78.2+/-0.3% versus 78.0+/-0. 1%). Complement depletion reduced TNF-alpha production 2 hours after ICH. Immunocytochemistry showed that complement depletion significantly reduced perihematomal C9 deposition, C3d production, and the number of C5a- and myeloperoxidase-positive cells. CONCLUSIONS: Complement depletion by CVF attenuates brain edema in ICH, indicating that complement activation plays an important role in ICH-induced brain edema. Preventing complement activation may be effective in the treatment of ICH.

Usefulness of hypotension during dobutamine echocardiography in predicting perioperative cardiac events.

This study was undertaken to determine the prognostic significance of hypotension induced during preoperative dobutamine stress echocardiography (DSE) before vascular and noncardiac thoracic surgery. Wall motion abnormality during DSE predicts perioperative risk. Although hypotension during DSE has not been shown to correlate with the presence or severity of coronary artery disease, its significance in perioperative risk assessment is unknown. We retrospectively studied 300 patients who had DSE within 6 months of noncardiac surgery. Perioperative events including death, myocardial infarction, ischemia, and arrhythmias were recorded. Odds ratios with 95% confidence intervals were used to examine the association between clinical and echocardiographic variables and perioperative events. A hypotensive response during DSE was seen in 85 patients (28%). Forty-eight patients (16%) had 54 perioperative complications including 4 cardiac-related deaths, 10 myocardial infarctions, 12 myocardial ischemic events, and 28 arrhythmias. Hypotension during DSE was predictive of the combined end point of perioperative cardiac mortality, myocardial infarction, and ischemia (odds ratio 4.04, 95% confidence interval 1.72 to 9.51). In a multivariate logistic regression model, hypotension during DSE remained a significant predictor (odds ratio 4.10, p<0.01). DSE-related hypotension was predictive of perioperative cardiac events and therefore may have a role in risk stratification before vascular or noncardiac thoracic surgery.

Extracorporeal life support: the University of Michigan experience.

The University of Michigan experience with extracorporeal life support (ECLS) in 1000 consecutive patients between 1980 and 1998 is the largest series at one institution in the world. Among this patient population, survival to hospital discharge in moribund patients with respiratory failure was 88% in 586 neonates, 70% in 132 children, and 56% in 146 adults. Survival in moribund patients with cardiac failure was 48% in 105 children and 33% in 31 adults. This article describes the University of Michigan's overall ECLS patient experience, the progression of ECLS from laboratory experiments to clinical application at the bedside, the expansion of the technology to other centers, and current ECLS technology and outcomes. Despite the challenges faced in clinical research in this field, our experience and that of others has shown that ECLS saves lives of patients with acute cardiac or pulmonary failure in a variety of clinical settings.

Predictors of malignancy in childhood peripheral lymphadenopathy.

PURPOSE: The aim of this study was to identify factors associated with malignant etiologies of childhood peripheral lymphadenopathy and to construct a model that may be used to assess the risk of malignancy. METHODS: The medical records of 60 consecutive patients 18 years old or less who underwent peripheral lymph node biopsies were reviewed. RESULTS: Increasing node size, number of sites of adenopathy, and age were associated with an increasing risk of malignancy (P < .05 for all variables). Graphs useful for risk determination were constructed based on these variables. Additional factors associated with malignancy included the presence of supraclavicular adenopathy (P < .01), an abnormal chest x-ray (P < .01), and fixed nodes (P < .01). Variables that were not statistically different between patients with benign and malignant adenopathy included the duration of adenopathy (P = .43), the presence of fever (P = .36), cough (P = .14), splenomegaly (P = .93), skin involvement (P = .39), tenderness (P = .49), and bilateral adenopathy (P = .39). Fluctuance was associated with benign adenopathy (P < .04). CONCLUSIONS: The risk of malignancy increased with increasing size and number of sites of adenopathy and age. Other significant predictors of malignancy included supraclavicular location, an abnormal chest x-ray, and fixed nodes. These data may be used to supplement clinical judgment to predict the risk of malignancy.

Thyroid gland hematoma after blunt cervical trauma.

Thyroid hematoma is a rare cause of airway obstruction in victims of blunt trauma. The case of a 34-year-old woman who developed orthopnea after a low-energy motor vehicle accident is described. Presenting greater than 24 hours after her accident, the patient noted dysphagia, tracheal deviation, and postural dyspnea. The diagnosis of thyroid gland hematoma was made with a combination of fiberoptic laryngoscopy, cervical computed tomography, and great vessel and carotid angiography. Invasive airway management was not required. The patient underwent a total thyroidectomy and recovered without complications.

Extracorporeal resuscitation of cardiac arrest.

OBJECTIVE: Extracorporeal support of heart and lung function (venoarterial perfusion) during cardiac arrest (ECPR) has been advocated as a means of improving survival following cardiac arrest. The authors retrospectively reviewed their institution's seven-year experience with this intervention. METHODS: Emergency department patients and inpatients in cardiac arrest or immediately postarrest were considered candidates. ECPR was instituted using venoarterial bypass and was continued until patients regained sufficient cardiopulmonary function to allow weaning from the device or until their condition was deemed irrecoverable. RESULTS: ECPR was attempted in 25 patients and successfully instituted in 21. Four patients (16%) were converted from ECPR to ventricular assist devices, two of whom survived and await transplantation. Seven additional patients were discharged from the hospital, resulting in an overall survival of 36%. Because none of the children treated survived, there was a trend toward higher age among survivors (survivors 40 +/- 14 yr, nonsurvivors 33 +/- 15 yr, p = 0.29). The duration of conventional CPR was shorter among survivors (survivors 21 +/- 16 min, nonsurvivors 43 +/- 32 min, p = 0.04), as was the duration of extracorporeal support (survivors 44 +/- 21 hr, nonsurvivors 87 +/- 96 hr, p = 0.18). Survival was seen only in patients whose conditions were amenable to a definitive therapeutic intervention, particularly cardiac arrest due to respiratory or pulmonary embolic disease. While four of the five patients treated in the ED were successfully supported, none survived to discharge. CONCLUSION: In select patients with reversible disease, extracorporeal CPR can be used to successfully treat cardiac arrest. Further investigation into its most appropriate application is warranted.

Research fundamentals: I. Getting from hypothesis to manuscript: an overview of the skills required for success in research.

This is the first in a series of articles developed by members of the Society for Academic Emergency Medicine (SAEM) Research Committee. The purpose of this series is to describe a stepwise approach to research, from the inception of a hypothesis to the final publication of a report. This series is written for junior academic emergency physicians (EPs), as well as nonacademic physicians who have an interest in research. This first article presents an overview of the steps involved in performing research and publishing the results, emphasizing the initial steps and the importance of collaboration.

The pattern of early lung parenchymal and air space injury following acute blood loss.

UNLABELLED: Acute lung injury is a frequent clinical occurrence following blood loss and trauma. The nature of this injury remains poorly understood. OBJECTIVE: To examine the relative parenchymal and intra-alveolar distribution of inflammation in a rat model of hemorrhage and resuscitation. METHODS: Rats were anesthetized and subjected to hemorrhage followed by resuscitation with shed blood and saline. Myeloperoxidase activity of lung homogenates and cytology of bronchoalveolar lavage fluid were used to measure total lung and intra-alveolar neutrophil invasion. Extravasation of i.v.-administered [125I]-albumin was used to determine total lung and alveolar permeability. Permeability results were analyzed using their base-10 logarithmic transformations. RESULTS: 86 animals were studied. Whole-lung myeloperoxidase activity was increased (control = 0.34 +/- 0.16 units, injured = 0.84 +/- 0.43 units, p < 0.01), while there was no difference in intra-alveolar leukocyte counts (injured = 1.85 +/- 1.30 x 10(5)/mL, control = 2.44 +/- 1.75 x 10(5)/mL, p = 0.40), suggesting that the cellular component of the injury was more severe in the intravascular and interstitial spaces. There was a strong trend toward increased permeability in the interstitial compartment, and a significant increase in permeability in the intra-alveolar compartment (whole-lung permeability: control = -0.27 +/- 0.19 units, injured = 0.10 +/- 0.55 units, p = 0.06; alveolar permeability: control = -2.00 +/- 0.47 units, injured = -1.32 +/- 0.49 units, p < 0.01), suggesting that the loss of integrity to macromolecules was not limited to the interstitium. CONCLUSION: Hemorrhage and resuscitation resulted in an acute lung injury characterized by extravasation of intravascular protein into both the interstitium and the intra-alveolar space. Neutrophil invasion of the lung was demonstrable only in the interstitial compartment.

Use of extracorporeal life support for adult patients with respiratory failure and sepsis.

Traditionally, adult sepsis has been considered a contraindication to extracorporeal life support (ECLS). The objective of this study was to review the authors' institutional experience with a subgroup of adult patients requiring ECLS for severe respiratory failure and sepsis. Hospital records from 100 consecutive adult patients with respiratory failure placed on ECLS between 1990 and 1996 were retrospectively reviewed. Patients with sepsis as a primary indication were identified, and blood culture data reviewed. Data were analyzed with t tests and chi-square and are presented as mean +/- standard deviation. Multiple logistic regression determined the impact of sepsis and positive blood cultures (PBCs) on survival. Fourteen patients required ECLS for sepsis; 36 had PBCs during hospitalization (15 before or during ECLS). Septic patients had lower pre-ECLS PaO2/FIO2 ratios (septic: 53 +/- 14 mmHg, nonseptic: 70 +/- 68 mmHg, p = 0.04). Patients with PBCs before or during ECLS were younger (PBC: 29 +/- 6 years, no PBC: 35 +/- 13 years, p = 0.003), remained on ECLS longer (PBC: 485 +/- 336 hours, no PBC: 232 +/- 212 hours, p = 0.01), and were more frequently cannulated within 12 hours (PBC: 15/15, no PBC 60/85 p = 0.02). Neither group differed in organ dysfunction (incidence or type), frequency of respiratory recovery, or survival. Neither sepsis nor positive blood cultures were independently predictive of mortality. Sepsis and positive blood cultures do not adversely affect outcome in adult patients with respiratory failure requiring ECLS.

Characteristics of an albumin dialysate hemodiafiltration system for the clearance of unconjugated bilirubin.

Extraction of protein bound liver failure toxins, such as unconjugated bilirubin, short chain fatty acids, and aromatic amino acids has been reported using hemodiafiltration with albumin in the dialysate, but the characteristics of such a system have not been described. Therefore, bilirubin clearance using albumin dialysate hemodiafiltration was evaluated in the setting of different dialysate albumin concentrations, varying temperature and pH. An in vitro continuous hemodiafiltration circuit was used with single pass countercurrent dialysis. Unconjugated bilirubin was added to bovine blood and filtered across a polyalkyl sulfone (PAS) hemofilter using matched filtration and dialysate flow rates. The serial bilirubin content was measured and first order clearance kinetics verified. The clearance rate constants were calculated for three dialysate groups of different albumin concentration at constant temperature and pH (group 1: 10 g/dl albumin, n = 5; 2 g/dl albumin, n = 5; normal saline, n = 5), and three groups of different temperature and pH at constant albumin dialysate concentration (group 2: pH = 7.0, temperature = 20 degrees C, n = 5; pH = 7.5, temperature = 20 degrees C, n = 5; pH = 7.0, temperature = 40 degrees C, n = 5). Comparisons were made with ANOVA and Tukey post hoc analysis. When albumin was used in the dialysate, the 2 g/dl group cleared bilirubin 3.1 times faster than saline alone (p = 0.001), and the 10 g/dl group was superior to both (p = 0.001). There were no measurable differences between the 2 g/dl groups at the various temperatures tested (p = 0.08), but the clearance was less at a pH of 7.5 (p = 0.015). The clearance of unconjugated bilirubin is greatly enhanced with the use of albumin containing dialysates when compared to traditional crystalloid hemodiafiltration, is greater at lower pH, and seems to be unaffected by temperature.

Statistical methodology: III. Receiver operating characteristic (ROC) curves.

Measures including sensitivity, specificity, and positive and negative predictive values have been traditionally used to assess a diagnostic test's ability to detect the presence or absence of disease. Receiver operating characteristic (ROC) curve analysis allows visual evaluation of the trade-offs between sensitivity and specificity associated with different values of the test result, or different "cutpoints" for defining a positive result. The purpose of this article is to define, construct, and interpret a ROC curve using a hypothetical example applicable to emergency medicine practice.

Partial liquid ventilation protects lung during resuscitation from shock.

Preliminary animal experience with partial liquid ventilation (PLV) suggests that this therapy may diminish neutrophil invasion and capillary leak during acute lung injury. We sought to confirm these findings in a model of shock-induced lung injury. Sixty anesthetized rats were studied. After hemorrhage to an arterial pressure of 25 mmHg for 45 min, animals were resuscitated with blood and saline and treated with gas ventilation alone or with 5 ml/kg of intratracheally administered perflubron. Myeloperoxidase activity was used to measure lung neutrophil content. A permeability index (the bronchoalveolar-to-blood ratio of 125I-labeled albumin activity) quantified alveolar leak. Injury caused an increase in myeloperoxidase that was reversed by PLV (injury = 0.837 +/- 0.452, PLV = 0.257 +/- 0.165; P < 0.01). Capillary permeability also increased with hemorrhage, with a strong trend toward improvement in the PLV group (permeability indexes: injury = 0.094 +/- 0.102, PLV = 0.045 +/- 0.045; 95% confidence interval for injury--PLV: -0.024, 0.1219). We conclude that PLV is associated with a decrease in pulmonary neutrophil accumulation and a trend toward decreased capillary leak after hemorrhagic shock.