Blood–brain barrier dysfunction in intensive care unit

The central nervous system is characterized by a peculiar vascularization termed blood–brain barrier(BBB),which regulates the exchange of cells and molecules between the cerebral tissue and the whole body.BBB dysfunction is a life-threatening condition since its presence corresponds to a marker of severity in most diseases encountered in the intensive care unit(ICU).During critical illness,inflammatory response,cytokine release,and other phenomena activating the brain endothelium contribute to alterations in the BBB and increase its permeability to solutes,cells,nutrients,and xenobiotics.Moreover,patients in the ICU are often old,with underlying acute or chronic diseases,and overly medicated due to their critical condition;these factors could also contribute to the development of BBB dysfunction.An accurate diagnostic approach is critical for the identification of the mechanisms underlying BBB alterations,which should be rapidly managed by intensivists.Several methods were developed to investigate the BBB and assess its permeability.Nevertheless,in humans,exploration of the BBB requires the use of indirect methods.Imaging and biochemical methods can be used to study the abnormal passage of molecules through the BBB.In this review,we describe the structural and functional characteristics of the BBB,present tools and methods for probing this interface,and provide examples of the main diseases managed in the ICU that are related to BBB dysfunction.

Protein-S-100-beta is increased in patients with decompensated cirrhosis admitted to ICU

Background Hepatic encephalopathy(HE)is highly prevalent in patients with liver diseases.The pathophysiology of HE is centered on the synergic role of hyperammonemia and systemic inflammation.However,some data suggest altered functioning of the blood–brain barrier(BBB).Assessing BBB function is challenging in clinical practice and at the bedside.Protein-S-100 Beta(PS100-Beta)could be a useful peripheral marker of BBB permeability in HE.This study aimed to assess plasmatic PS100-Beta levels in a prospective cohort of patients admitted to the intensive care unit(ICU)with decompensated cirrhosis with and without overt HE.Methods We retrospectively evaluated a prospective cohort of cirrhotic patients admitted to the ICU from October 2013 to September 2015 that had an available plasmatic PS100-Beta measurement.Patients with previous neurological impairment or limitation of intensive or resuscitative measures were excluded.Overt HE was defined as West-Haven grades 2 to 4.The patients were compared to a control cohort of outpatient clinic cirrhotic and non-cirrhotic patients explored for isolated elevation of liver enzymes.After ICU discharge,the patients were followed for at least 3 months for the occurrence of overt HE.Adverse outcomes(liver transplantation or death)were collected.The ability of PS100-Beta–in combination with other factors–to predict overt HE was evaluated in a multivariate analysis using logistic regression.Likelihood ratios were used to determine the effects and calculate odds ratios(OR).Survival analysis was performed by using the Kaplan–Meier method and survival between groups was compared using a Log-rank test.Results A total of 194 ICU patients and 207 outpatients were included in the study.Increased levels of plasmatic PS100-Beta were detected in the ICU decompensated cirrhotic patients compared with the outpatients([0.15±0.01]mg/L vs.[0.08±0]mg/L,P<0.001).ICU patients with overt HE had higher levels of PS100-Beta([0.19±0.03]mg/L)compared with the ICU patients without overt HE([0.13±0.01]mg/L)(P=0.003).PS100-Beta levels did not differ in outpatients with F 0–3 compared to F 4 fibrosis(P=0.670).PS100-Beta values were correlated with Child-Pugh score(P<0.001),Model for End-Stage Liver Disease(MELD)score(P=0.004),C-reactive protein(P<0.001),ammonemia(P<0.001),and chronic liver failure consortium(CLIF-C)organ failure(P<0.001)and CLIF-C acute-on-chronic(P=0.038)scores,but not with leukocytes(P=0.053),procalcitonin(PCT)(P=0.107),or the lymphocyte-to-neutrophil ratio in ICU patients(P=0.522).In a multivariate model including age,ammonemia,PS100-Beta,PCT,MELD,presence of transjugular portosystemic shunt,and sodium level,the diagnostic performance was 0.765 for the diagnosis of overt HE.Patients with a PS100-Beta level<0.12 mg/L had a better overall survival(P=0.019)and a better survival without liver transplantation(P=0.013).Conclusions Serum levels of PS100-Beta are elevated in ICU patients with decompensated cirrhosis,and even more so in those displaying overt HE,and the levels are correlated with outcome.This suggests an increase in the permeability of the BBB in these patients.