Endotoxaemia in Critically Ill Children Shamik Dholakia, 1 I. Simon Nadel, 2 Helen Betts, 3 1 Imperial College School of Medicine, 2 PICU, St Mary’s Hospital Paddington 3 Academic Paediatrics, Imperial College. Introduction Over 1500 children are admitted to paediatric intensive care units (PICU) in the UK with presumed sepsis each year. [1] Endotoxin (lipopolysaccharide, LPS) found in the Gram-negative bacterial cell wall is one of the most potent stimuli of inflammation, causing the clinical signs seen in sepsis (figure 1A). [2] However the clinical signs of sepsis are non-specific and biomarkers tend to appear late, possibly delaying treatment. Thus there remains an unacceptable mortality rate of over 10%, demonstrating the need for better markers of sepsis in the clinical setting. (figure 1B) [3] Results Endotoxaemia was defined as >0.40 EAA units Conclusions 54% had moderate or high EAA on day 1 75% of children had detectable LPS in their blood at some point during the first 4 days of admission Endotoxaemia occurs in a significant number of patients with no positive culture Endotoxaemia is associated with an increased length of stay on PICU High level endotoxaemia is associated with increased severity of illness Traditional endotoxin measurement uses the Limulus Amoebocyte Lysate (LAL) assay which has limited reliability in blood, is non quantitative and cross-reacts with gram positive and fungal antigens, making it inaccurate. The Endotoxin Activity Assay (EAA) is more specific and sensitive, as it uses whole blood, gives rapid quantitative results detecting free LPS and does not cross react, providing more reliable results. The gut acts as a reservoir of LPS, containing up to 25g of endotoxin in the form of bacterial flora. Impaired gut perfusion during systemic inflammation and shock, may allow the translocation of flora or bacterial-derived products such as LPS from the GI tract into the bloodstream, giving rise to or amplifying a ‘sepsis-like’ clinical picture. [4] Systemic inflammation is common in children admitted to PICU with documented Gram- negative sepsis, but also in other infections and in non-infectious conditions, suggesting involvement of endotoxin in the pathophysiology of paediatric critical illness and an association with adverse outcome. [5] Acknowledgements Spectral Diagnostics, St Mary’s PICU staff and Academic Paediatric Infectious Disease Unit, Professor Martin Crowder, Imperial College – Statistics. Funding for this study was provided by COSMIC (Children of St Mary’s Intensive Care) References 1. – national report of paediatric intensive care unit audit network. 2. Cohen J. The immunopathogenesis of sepsis. Nature 2002; 420 : Goldstein et al. International pediatric sepsis consensus conference: definitions for sepsis and organ dysfunction in pediatrics. Pediatric Crit Care Med 2005; 6: 2-8; 4.Deitch et al Effect of haemorrhagic shock on bacterial translocation, intestinal morphology and intestinal permeability in conventional and antibiotic-decontaminated rats. Crit Care Med 1990; 18: Marshall et al. Diagnostic and prognostic implications of endotoxemia in critical illness: Results of the MEDIC study. Journal of infectious disease 2004; 190: www.picanet.org.uk Aim To determine the incidence of endotoxaemia in critically ill children using the EAA; and correlating the degree of endotoxaemia with diagnosis, disease severity and outcome. Methods Subjects: Prospective observational study: All children admitted to PICU for any reason were eligible for inclusion following informed consent, 100 patients were enrolled over 6 month period. Samples: 2 ml of blood was collected daily in EDTA vacutainer tubes when the child was having blood taken for other reasons through already established venous or arterial lines and processed within 30 minutes of collection Assay: EAA utilises complement-mediated neutrophil activation to measure Endotoxin activity in whole blood using chemiluminescence. This assay utilises 0.5 ml of patient’s whole blood and gives a quantitative colorimetric readout which is correlated with LPS level within the sample ( Data: Demographic and clinical details were recorded, including physiological variables to estimate severity scores by Paediatric Index of Mortality 2 (PIM2) on admission, and daily Paediatric Logistic Organ Dysfunction Score (PELOD). Also recorded was length of stay, illness category and microbiological diagnosis (if any). Analysis: SPSS - correlations identified using Spearman’s rank (p = 0.05) Future Work Our work raises several questions: Where does this endotoxin come from? Published data suggests that it may come from increased gut permeability in critical illness, but this has not been confirmed. Can the measurement of endotoxin assist in the management of critically ill children on PICU? Could neutralization of endotoxin with anti-endotoxin therapy in critically ill children improve outcome? 1A.1B. Zymosan LPS / anti- LPS complex LPS Anti- LPS (IgM ) Release of oxyradicals and lumiphor (median 5 days) 5 deaths PICU days EAA High ( n = 27 ) 1 – 57 (median 4 days) 4 deaths PICU days EAA Intermediate ( n = 21) 0.5 – 35 (median 3 days) 2 deaths PICU days EAA Low ( n = 30 ) High EAA Low EAA PIM2 % PELOD % Days in PICU Days in PICU High level > 50 pg/ml of LPS > 0.60 Intermediate level ~ 25 – 50 pg/ml of LPS 0.40 – 0.59 Below Threshold for detection of LPS0.00 – 0.39 EAA Result Interpretation