Endothelium in Severe Sepsis

The endothelial response is emerging as a critical element of sepsis pathophysiology. Preclinical data and small human studies suggest that endothelial cells are responsible for increased leukocyte adhesion, inflammation, activation of coagulation, and respond to increased levels of the endothelial cell mediator Vascular Endothelial Cell Growth Factor (VEGF). Furthermore, the endothelium plays an active role in microcirculatory homeostasis and the preservation of microvascular flow.

The researchers propose to study the endothelium by performing a comprehensive endothelial cell "read-out" through the measurement of circulating levels of endothelial cell biomarkers as well as direct visualization of microcirculatory flow with in-vivo videomicroscopy. Accordingly, the broad, long-term objective of this project is to study the role of the endothelium in sepsis in a large, heterogeneous group of patients. To accomplish this, the researchers will investigate two specific aims: 1) to study biomarkers of endothelial cell activation in sepsis; and, 2) to study microcirculatory flow in sepsis.

The overall hypotheses of this project is that severe sepsis is associated with endothelial dysfunction; that endothelial dysfunction, in turn, is predictive of subsequent organ failure and death; and that protocolized resuscitation attenuates endothelial cell (EC) dysfunction and improves patient survival. To test these hypotheses the researchers will utilize ancillary measurements (notably in-vivo assessment of microcirculatory flow), and additional samples and assays from the ProCESS clinical trial. ProCESS is a large, multicenter, randomized, controlled clinical trial testing the efficacy and mechanisms behind protocolized goal-directed resuscitation.

To conduct this line of investigation directed at the endothelium and microcirculation that was not addressed in the original trial, the researchers will select 8 ProCESS study sites for participation in this ancillary study. The researchers will directly visualize and quantify the presence of disturbances in sublingual microcirculatory flow utilizing the novel bedside technique of orthogonal polarization microscopy. Furthermore, the researchers will develop a multi-marker panel that assesses degree of endothelial cell dysfunction and subsequent mortality risk.

The researchers will also capitalize on the randomly assigned interventions in the ProCESS clinical trial to observe differences in endothelial response across the alternative resuscitation strategies. Improved understanding of these mechanisms may lead to strategies to predict outcome, to select patients for tailored (endothelium-directed) therapies, to follow treatment response, and to develop novel therapies for endothelial dysfunction in sepsis.

Inclusion criteria

• Enrolled as a participant in the ProCESS Trial (clinicaltrial.gov identifier NCT00510835)
• At least 18 years of age
• Suspected infection
• Two or more systemic inflammatory response syndrome (SIRS) criteria

• Temperature </= 36˚ C or >/= 38˚C
• Heart rate >/= 90 beats per minute
• Mechanical ventilation for acute respiratory process or respiratory rate >/= 20 breaths per minute or PaC02 < 32 mmHg
• WBC >/= 12,000/mm³ OR </= 4,000/mm³ OR > 10% bands
• Refractory hypotension (a systolic blood pressure < 90 mm Hg despite an IV fluid challenge of at least 20 ml/kg over a 30 minute period) or evidence of hypoperfusion (a blood lactate concentration >/= 4 mmol/L)

Exclusion criteria

• Known pregnancy
• Primary diagnosis of acute cerebral vascular event, acute coronary syndrome, -- acute pulmonary edema, status asthmaticus, major cardiac arrhythmia, active
• gastrointestinal hemorrhage, seizure, drug overdose, burn or trauma
• Requirement for immediate surgery
• ANC < 500/mm³
• CD4 < 50/mm³
• Do-not-resuscitate status
• Advanced directives restricting implementation of the protocol
• Contraindication to central venous catheterization
• Contradiction to blood transfusion (e.g., Jehovah's Witness)
• Treating physician deems aggressive care unsuitable
• Participation in another interventional study
• Transferred from another in-hospital setting
• inability to tolerate microscan procedure (eg oxygen requirement via face mack that can not be discontinue for the procedure)