Ronni R. Plovsing

Coagulopathy, catecholamines, and biomarkers of endothelial damage in experimental human endotoxemia and in patients with severe sepsis: A prospective study

PURPOSE The aim of this study was to investigate associations between circulating catecholamines, endothelial damage, and coagulopathy in experimental human endotoxemia and septic patients. MATERIALS AND METHODS Nine healthy male volunteers undergoing endotoxemia (4-hour 0.5 ng/kg/hour infusion of E. coli lipopolysaccharide, blood sampling at 0, 4, and 6 hours) and 20 patients with severe sepsis. Analysis of plasma biomarkers (adrenaline, noradrenaline, thrombomodulin, syndecan-1, soluble vascular endothelial cadherin, histone-complexed DNA fragments, soluble CD40 ligand [sCD40L], protein C, tissue-type plasminogen activator, plasminogen activator inhibitor 1) and routine coagulation tests. RESULTS Endotoxemia increased heart rate, temperature, white blood cell count, C-reactive protein and procalcitonin, decreased blood pressure and induced a hemostatic response with platelet consumption, reduced protein C and sCD40L levels and enhanced tissue-type plasminogen activator release (all P<.05). Septic patients had increased levels of noradrenaline, syndecan-1, thrombomodulin, histone-complexed DNA and sCD40L but reduced soluble vascular endothelial cadherin and plasminogen activator inhibitor 1 (all P<.05) and plasma catecholamines correlated positively with syndecan-1 (adrenaline and noradrenaline) and sTM (only noradrenaline) (all P<.05), biomarkers reflecting endothelial damage. Furthermore, noradrenaline, syndecan-1 and thrombomodulin levels correlated with INR and disease severity scores (noradrenaline and thrombomodulin) (all P<.05). CONCLUSIONS Experimental endotoxemia induced a discrete hemostatic response without sympathoadrenal activation or endothelial damage. Septic patients had high levels of catecholamines and endothelial damage biomarkers that correlated with each other and with markers of hypocoagulability and disease severity.

Disassociation of static and dynamic cerebral autoregulatory performance in healthy volunteers after lipopolysaccharide infusion and in patients with sepsis.

Sepsis is frequently complicated by brain dysfunction, which may be associated with disturbances in cerebral autoregulation, rendering the brain susceptible to hypoperfusion and hyperperfusion. The purpose of the present study was to assess static and dynamic cerebral autoregulation 1) in a human experimental model of the systemic inflammatory response during early sepsis and 2) in patients with advanced sepsis. Cerebral autoregulation was tested using transcranial Doppler ultrasound in healthy volunteers (n = 9) before and after LPS infusion and in patients with sepsis (n = 16). Static autoregulation was tested by norepinephrine infusion and dynamic autoregulation by transfer function analysis (TFA) of spontaneous oscillations between mean arterial blood pressure and middle cerebral artery blood flow velocity in the low frequency range (0.07-0.20 Hz). Static autoregulatory performance after LPS infusion and in patients with sepsis was similar to values in healthy volunteers at baseline. In contrast, TFA showed decreased gain and an increased phase difference between blood pressure and middle cerebral artery blood flow velocity after LPS (both P < 0.01 vs. baseline); patients exhibited similar gain but lower phase difference values (P < 0.01 vs. baseline and LPS), indicating a slower dynamic autoregulatory response. Our findings imply that static and dynamic cerebral autoregulatory performance may disassociate in sepsis; thus static autoregulation was maintained both after LPS and in patients with sepsis, whereas dynamic autoregulation was enhanced after LPS and impaired with a prolonged response time in patients. Hence, acute surges in blood pressure may adversely affect cerebral perfusion in patients with sepsis.

Discrepant fibrinolytic response in plasma and whole blood during experimental endotoxemia in healthy volunteers.

Background Sepsis induces early activation of coagulation and fibrinolysis followed by late fibrinolytic shutdown and progressive endothelial damage. The aim of the present study was to investigate and compare the functional hemostatic response in whole blood and plasma during experimental human endotoxemia by the platelet function analyzer, Multiplate and by standard and modified thrombelastography (TEG). Methods Prospective physiologic study of nine healthy male volunteers undergoing endotoxemia by means of a 4-hour infusion of E. coli lipopolysaccharide (LPS, 0.5 ng/kg/hour), with blood sampled at baseline and at 4 h and 6 h. Physiological and standard biochemical data and coagulation tests, TEG (whole blood: TEG, heparinase-TEG, Functional Fibrinogen; plasma: TEG±tissue-type plasminogen activator (tPA)) and Multiplate (TRAPtest, ADPtest, ASPItest, COLtest) were recorded. Mixed models with Tukey post hoc tests and correlations were applied. Results Endotoxemia induced acute SIRS with increased HR, temperature, WBC, CRP and procalcitonin and decreased blood pressure. It also induced a hemostatic response with platelet consumption and reduced APTT while INR increased (all p<0.05). Platelet aggregation decreased (all tests, p<0.05), whereas TEG whole blood clot firmness increased (G, p = 0.05). Furthermore, during endotoxemia (4 h), whole blood fibrinolysis increased (clot lysis time (CLT), p<0.001) and Functional Fibrinogen clot strength decreased (p = 0.049). After endotoxemia (6 h), whole blood fibrinolysis was reduced (CLT, p<0.05). In contrast to findings in whole blood, the plasma fibrin clot became progressively more resistant towards tPA-induced fibrinolysis at both 4 h and 6 h (p<0.001). Conclusions Endotoxemia induced a hemostatic response with reduced primary but enhanced secondary hemostasis, enhanced early fibrinolysis and fibrinogen consumption followed by downregulation of fibrinolysis, with a discrepant fibrinolytic response in plasma and whole blood. The finding that blood cells are critically involved in the vasculo-fibrinolytic response to acute inflammation is important given that disturbances in the vascular system contribute significantly to morbidity and mortality in critically ill patients.

Two cases of infectious purpura fulminans and septic shock caused by Capnocytophaga canimorsus transmitted from dogs

Abstract We report 2 cases of Capnocytophaga canimorsus-induced septicaemia complicated by purpura fulminans in previously healthy individuals, both of whom had been exposed to dog saliva prior to disease. They both presented with purpuric skin lesions, as well as the tetrad of abdominal symptoms, haemolytic anaemia, metabolic acidosis, and renal failure, which may be common in C. canimorsus-associated purpura fulminans. The patients survived after treatment with broad-spectrum antibiotics and supportive intensive care. C. canimorsus should be considered as a possible cause of infectious purpura fulminans in the unresolved critically ill patient with a history of dog exposure.

High versus low blood-pressure target in septic shock.

To the Editor: As noted by Asfar et al. (April 24 issue),1 a major concern related to targeting a relatively low mean arterial blood pressure in patients with septic shock is that the brain is at risk for ischemia in this condition. The risk of potential brain ischemia is particularly pertinent among patients with a history of arterial hypertension, because their cerebral autoregulatory curve may be shifted to the right.2 Indeed, cerebral ischemia may contribute to sepsis-associated encephalopathy and persistent neurocognitive dysfunction.3 However, neither the primary nor the secondary outcomes in the study by Asfar et al. involved any measures of neurocognitive function. A mean arterial blood pressure of approximately 65 to 90 mm Hg describes the lower limit of autoregulation in healthy persons,4 and the same level appears to be present in critically ill patients with sepsis who do not have a history of hypertension.5 Before the findings by Asfar et al. are implemented in major guidelines, we think that further studies should address the way in which cerebral hemodynamics are specifically affected in patients with sepsis and a history of hypertension, as well as whether targeting a relatively high mean arterial blood pressure improves long-term neurocognitive function.To the Editor: As noted by Asfar et al. (April 24 issue),1 a major concern related to targeting a relatively low mean arterial blood pressure in patients with septic shock is that the brain is at risk for ischemia in this condition. The risk of potential brain ischemia is particularly pertinent among patients with a history of arterial hypertension, because their cerebral autoregulatory curve may be shifted to the right.2 Indeed, cerebral ischemia may contribute to sepsis-associated encephalopathy and persistent neurocognitive dysfunction.3 However, neither the primary nor the secondary outcomes in the study by Asfar et al. involved any measures of neurocognitive function. A mean arterial blood pressure of approximately 65 to 90 mm Hg describes the lower limit of autoregulation in healthy persons,4 and the same level appears to be present in critically ill patients with sepsis who do not have a history of hypertension.5 Before the findings by Asfar et al. are implemented in major guidelines, we think that further studies should address the way in which cerebral hemodynamics are specifically affected in patients with sepsis and a history of hypertension, as well as whether targeting a relatively high mean arterial blood pressure improves long-term neurocognitive function.

Teaching baroreflex physiology to medical students: a comparison of quiz-based and conventional teaching strategies in a laboratory exercise.

Quiz-based and collaborative teaching strategies have previously been found to be efficient for the improving meaningful learning of physiology during lectures. These approaches have, however, not been investigated during laboratory exercises. In the present study, we compared the impact of solving quizzes individually and in groups with conventional teaching on the immediate learning during a laboratory exercise. We implemented two quizzes in a mandatory 4-h laboratory exercise on baroreflex physiology. A total of 155 second-year medical students were randomized to solve quizzes individually (intervention group I, n = 57), in groups of three to four students (intervention group II, n = 56), or not to perform any quizzes (control; intervention group III, n = 42). After the laboratory exercise, all students completed an individual test, which encompassed two recall questions, two intermediate questions, and two integrated questions. The integrated questions were of moderate and advanced difficulty, respectively. Finally, students completed an evaluation form. Intervention group I reached the highest total test scores and proved best at answering the integrated question of advanced difficulty. Moreover, there was an overall difference between groups for student evaluations of the quality of the teaching, which was highest for intervention group II. In conclusion, solving quizzes individually during a laboratory exercise may enhance learning, whereas solving quizzes in groups is associated with higher student satisfaction.

Transcompartmental inflammatory responses in humans: IV versus endobronchial administration of endotoxin*.

Objectives:Transcompartmental signaling during early inflammation may lead to propagation of disease to other organs. The time course and the mechanisms involved are still poorly understood. We aimed at comparing acute transcompartmental inflammatory responses in humans following lipopolysaccharide-induced pulmonary and systemic inflammation. Design:Randomized, double-blind, placebo-controlled, crossover study. Setting:ICU. Subjects:Healthy male volunteers. Interventions:Fifteen volunteers (mean age, 23; SD, 2 yr) received Escherichia coli endotoxin (lipopolysaccharide, 4 ng/kg) IV or endobronchially on two different study days. Groups were evaluated by bronchoalveolar lavage at baseline (0 hr) and 2, 4, 6, 8, or 24 hours postchallenge. Cardiorespiratory variables were continuously recorded throughout the study day, and plasma and bronchoalveolar lavage fluid markers of inflammation were measured. Measurements and Main Results:IV endotoxin elicited a systemic inflammatory response with a time-dependent increase and peak in tumor necrosis factor-&agr;, interleukin-6, and leukocyte counts (all p < 0.001). Furthermore, a delayed (6–8 hr) increase in bronchoalveolar lavage fluid interleukin-6 concentration (p < 0.001) and alveolar leukocyte count (p = 0.03) and a minor increase in bronchoalveolar lavage fluid tumor necrosis factor-&agr; were observed (p = 0.06). Endobronchial endotoxin was followed by progressive alveolar neutrocytosis and increased bronchoalveolar lavage fluid tumor necrosis factor-&agr;, interleukin-6, and albumin (all p < 0.001); a systemic inflammatory response was observed after 2–4 hours, with no change in plasma tumor necrosis factor-&agr;. Conclusions:Acute lung or systemic inflammation in humans is followed by a transcompartmental proinflammatory response, the degree and differential kinetics of which suggests that the propagation of inflammation may depend on the primary site of injury.

Poor agreement between transcranial Doppler and near‐infrared spectroscopy‐based estimates of cerebral blood flow changes in sepsis

Continuous monitoring of cerebral blood flow (CBF) may be valuable in critically ill patients with sepsis. In this study, we compared spatially resolved near‐infrared spectroscopy (NIRS) to transcranial Doppler ultrasound (TCD)‐derived estimates of noradrenaline‐associated changes in CBF in such patients.

Inflammation-Induced Changes in Circulating T-Cell Subsets and Cytokine Production During Human Endotoxemia

Observational clinical studies suggest the initial phase of sepsis may involve impaired cellular immunity. In the present study, we investigated temporal changes in T-cell subsets and T-cell cytokine production during human endotoxemia. Endotoxin (Escherichia coli lipopolysaccharide 4 ng/kg) was administered intravenously in 15 healthy volunteers. Peripheral blood and bronchoalveolar lavage fluid (BALF) were collected at baseline and after 2, 4, 6, 8, and 24 hours for flow cytometry. CD4+CD25+CD127lowFoxp3+ regulatory T cells (Tregs), CD4+CD161+ cells, and activated Human leukocyte antigen, HLA-DR+CD38+ T cells were determined. Ex vivo whole-blood cytokine production and Toll-like receptor (TLR)-4 expression on Tregs were measured. Absolute number of CD3+CD4+ (P = .026), CD3+CD8+ (P = .046), Tregs (P = .023), and CD4+CD161+ cells (P = .042) decreased after endotoxin administration. The frequency of anti-inflammatory Tregs increased (P = .033), whereas the frequency of proinflammatory CD4+CD161+ cells decreased (P = .034). Endotoxemia was associated with impaired whole-blood production of tumor necrosis factor-α, interleukin-10, IL-6, IL-17, IL-2, and interferon-γ in response to phytohaemagglutinin but did not affect TLR4 expression on Tregs. No changes in the absolute count or frequency of BALF T cells were observed. Systemic inflammation is associated with lymphopenia, a relative increase in the frequency of anti-inflammatory Tregs, and a functional impairment of T-cell cytokine production.

T cell subsets in human airways prior to and following endobronchial administration of endotoxin

Bronchial instillation of lipopolysaccharide (LPS) provides a reversible model of lung inflammation that may resemble early stages of acute respiratory distress syndrome (ARDS). We investigated the distributions of T‐cell subsets in the human airways and sought to determine whether pro‐ and anti‐inflammatory T cells are involved in the local immune response to lung inflammation.