SEPSIS

1. SEPSIS CCM SENIOR RESIDENT HALF DAY AUGUST 24, 2011

2. OUTLINE • DEFINITIONS • PATHOPHYSIOLOGY • TREATMENT • COMPLICATION

3. DEFINITION • Evolving: • Long history • Sepsis: derived from Greek word for the decomposition of animal or vegetable matter • First used by Homer over 2700 yrs ago • Over 100 yrs ago the link between bacteria and systemic infection was first described. (Schottmueller, AIM 1914)

4. DEFINITION • Sepsis is a HOST RESPONSE to an invading organism and really reflects that response as much if not more than the organism • Sepsis Syndrome: • R. Bone 1989 • Hypo or hyperthermia • Tachycardia • Tachypnea • Presence of a site of infection • At least one site of end organ damage / hypoperfusion • Altered LOC • Hypoxia • Elevated lactate • oliguria

5. DEFINITION • CONSENSUS CONFERENCE: (ACCP / SCCM / ESICM/ SIS) (‘92, 2001) • SIRS: (at least 2 of): • Temp < 36C or > 38C • HR > 90bpm • RR >20 or PaCO2 < 32mmHg • WBC > 12 or <4 • SEPSIS: • systemic response + 2 or more SIRS criteria • Severe Sepsis: • Sepsis + organ dysfunction, hypotension or hypoperfusion (lactate, oliguria, altered LOC) • Septic Shock: • Hypotension despite fluid resuscitation + perfusion abnormalities including lactic acidosis, oliguria, altered LOC, requiring vasopressors or inotropes

6. DEFINITION • PIRO Grading System: (Moreno) • P: predisposing factors: age/ sex / social / comorbidities / meds • I: Insult / infection: microbe / site • R: Host Response: WBC / coag / biomarkers / temp / HR / BP / CO • O: Organ dysfunction: PaO2/FiO2 / Cr / Bili / Plt/ u/o / GCS • PROBLEM: • All of the definitions include a very heterogeneous population • Moving target: evolving as the understanding of sepsis increases • Heterogeneity: may explain the negative results of may of the large trials in sepsis. Or may explain the positive results of others (Prowess)

7. PATHOPHYSIOLOGY • 1. MICROBIAL / PATHOGEN FACTORS • 2. HOST FACTORS • INNATE IMMUNE SYSTEM FUNCTION / DYSFUNCTION • ENDOTHELIAL CELL DYSFUNCTION / COAGULATION • 3. MICROCIRCULATORY CHANGE

8. PATHOPHYSIOLOGY • MICROBIAL FACTORS: • VIRULENCE FACTORS • QUORUM SENSING SYSTEMS • VIRULENCE GENE UPREGULATION

9. PATHOPHYSIOLOGY • MICROBIAL FACTORS: virulence • 5 1. mechanisms of bacterial adherence to host epithelial surfaces 2. mechanisms of bacterial invasion 3. bacterial host defense evasion mechanisms 4. virulence factor-mediated host immune dysfunction **** 5. virulence factor-induced host tissue injury****

10. PATHOPHYSIOLOGY • Mechanisms of bacterial adherence to host epithelial surfaces • Adhesins: secreted proteins enabling adhesion • Flagella, fimbrae, pili • Secretion system: attach and inject • Ligand mimicry

11. PATHOPHYSIOLOGY • Mechanism of bacterial invasion following adherence: • Bacterial protein secretion systems • Transporter systems allowing delivery of bacterial products into the extracellular matrix • Lipidrafts • Avoid the apical area of the cell • Bind near the cell base which is rich in cholesterol and pathogen recognition factors

12. PATHOPHYSIOLOGY • Bacterial host defense evasion mechanisms: • Anti-phagocytosis: • Inhibit opsonization • Surface antigenic variation to prevent recognition • Inhibition of uptake via the release of toxic proteins • Intracellular survival and replication in cytoplasm and lysosomes • Induction of immune effector cell apoptosis • Biofilm formation: • Polysaccharide matrix that encapsulate entire bacterial colonies • Avoid phagocytosis and drugs

13. PATHOPHYSIOLOGY • BACTERIAL CELL TO CELL COMMUNICATION: QUORUM-SENSING SYSTEMS (QSS) • Gram +vs and Gram –vs (different mechanisms) • Secretion of signaling molecules • Avoid detection by the host until there is enough bacteria present (critical mass) • Once critical mass is attained virulence genes are expressed and cellular proliferation signals are produced • Leads to swift invasion and establishment of infection • Hence concept of a INNOCULUM

14. PATHOPHYSIOLOGY 2 MAIN QUORUM MECHANISMS: • 1. GRAM POSITIVES • Synthesize cytosolic autoinducers • Actively transported to the extracellular environment where they bind to neighbouring bacteria • Induce a signaling cascade resulting in QSS control of relevant aspects of cellular function

15. PATHOPHYSIOLOGY • 2. GRAM NEGATIVES: • Acyl-homoserine lactones (AHL) • Diffuse between the intra and extracellular environments until a critical population density of bacteria attained. • High signal molecule concentration which binds to the intracellular promotor regions of the QSS genes leading to relevant gene expression

16. PATHOPHYSIOLOGY • VIRULENCE GENE UPREGULATION & INCREASED EXPRESSION: • Ability is dependent on quality and quantity of virulence factors • Must be able to adapt to host systems which are many and varied • PATHOGENECITY UNITS: • Genes encoding virulence factors are in close proximity to specific sequences of chromosomal DNA • Unstable DNA regions – allowing for “fortuitous” mutations • C. difficiele outbreak in Quebec • Able to exchange DNA with these unstable areas by lateral transfer

17. PATHOPHYSIOLOGY • HOST DEFENSE MECHANISMS: • 2 • Innate • Fluid phase • Endothelial cell dysfunction

18. PATHOPHYSIOLOGY • NORMAL IMMUNE RESPONSE: • Structural barriers • Mucosa • Endogenous flora • Innate followed by adaptive • Innate: early, containment • Adaptive: fine tunning • 7-10 days • Ab response • Initially pro-inflammatory then immunosuppressive • Cross-talk between different systems: ANS, coagulation • Heterogeneity (genetic and non-genetic) • Success of invasion is dependent on the host response

19. PATHOPHYSIOLOGY • HOST RESPONSE: PATHOGEN RECOGNITION • PRRs: pattern recognition receptors • PAMPs: pathogen associated molecular patterns • DAMPs: danger-associated molecular patters • Concept: • Bacteria and viruses: molecular structures that are conserved / shared / consistent (PAMPs) • = molecular signatures • DAMPs: • PAMPs + Alarmins (intracellular proteins expressed or released with host cell injury)

20. PATHOPHYSIOLOGY • PRRs: • 4 families • 1. TOLL-like receptors • 2. NOD-LRR proteins • 3. cytoplasmic caspase activating and recruiting domain helicases • 4. C-type lectin receptors

21. PATHOPHYSIOLOGY • TOLL-LIKE RECEPTORS: • Cool or weird • Drosophila mutated and looked weird • 10-13 toll-like receptors described • Initiate the immune response and regulate the adaptive response • Transmembrane proteins • Extracellular: Leu rich repeats – bind ligand • Intracellular: toll-like interleukin-1R resistance domain • 4 adapter molecules which activate protein kinases amplifying the signal

22. PATHOPHYSIOLOGY • TOLL-LIKE RECEPTORS: • TLR 1: lyme disease and N. meningitides • TLR 2: Grams +s / most bacteria / Candida albicans/ DAMPs • TLR 4: Gram –vs / LPS / Candida / DAMPs • TLR 5: salmonella / flagellated bacteria

23. PATHOPHYSIOLOGY • TRANSMEMBRANE PROTEINS: • Phosphorylation by a KINASE • CASCADE: • Often more than one kinase • SIGNAL AMPLIFICATION • as phosphorylation of several kinases can in turn activate several cascade: NON-SPECIFIC • Control: • Dephosphorylation

24. PATHOPHYSIOLOGY • TRANSMEMBRANE PROTEINS: • CASPASES: • Activated and produce many of the changes leading to apoptosis • RESULT: • Synthesis and release of increased amounts of mediators into the systemic circulation in an attempt to activate and recruit more effector cells.

25. PATHOPHYSIOLOGY • INFLAMMATORY MEDIATORS RELEASED: • HIGH MOBILITY GROUP BOX 1 PROTEIN (HMGB1) • Nuclear and cytoplasmic protein • Active in DNA transcription / repair / replication • MACROPHAGE MIGRATION INHIBITORY FACTOR: • Cytokine / activates T-cells • Can induce pro-inflammatory cytokines in macrophages • Elevated levels early = poor outcome

26. PATHOPHYSIOLOGY • IMMUNE AND NON-IMMUNE EFFECTOR CELL DYSFUNCTION: • Normal effector response in response to Cyk release is lost in severe sepsis • NEUTROPHILS: • NORMAL: • Phagocytosis and release of cytotoxic molecules • Apoptosis in 7 hrs • SEPSIS: • Loss of regulation with excessive activation and prolonged survival • Leads to ENDOTHELIAL DAMAGE

27. PATHOPHYSIOLOGY • IMMUNE AND NON-IMMUNE EFFECTOR CELL DYSFUNCTION: • LYMPHOCYTES: • NORMAL: • Pro-inflammatory response followed by regulatory response • SEPSIS: • Accelerated apoptosis • Loss of regulatory function

28. PATHOPHYSIOLOGY • COAGULATION CASCADE IN SEVERE SEPSIS: • Range of pathology: clinically silent to DIC • Coagulation: 3 phases • 1. initiation • 2. amplification • 3. thrombin action • There is considerable overlap and counterbalancing mechanisms between these phases

29. PATHOPHYSIOLOGY • COAGULATION CASCADE: • INITIATION: • TF (injury) + VII VIIa-TF complex  Thrombin • AMPLIFICATION: • Thrombin / Plt / cofactors • Release of prothrombin (X)+plt+factorsprothrombin complex thrombin burst  clot • THROMBIN: • Thrombin recruitment of additional factors • Maintains platelet activation • Facilitates fibrinogen  fibrin

30. PATHOPHYSIOLOGY • COAGULATION CASCADE DYSFUNCTION: • 2 PHASES: • 1. initial activation • TF • Immune effector cells (neutrophils) • cytokines • 2. largely deregulated response with suppression of the autofibrinolytic pathway • TF, thrombin, APC bind to receptors on endothelial cells leading to cyk production and alters apoptosis • Endothelial cells • TF mediated initiation of thrombin • Dysfunction of anticoagulant pathways • Inhibition of fibrinogen

31. PATHOPHYSIOLOGY • COAGULATION CASCADE DYSFUNCTION: • Activated Protein C: APC • Activated by thrombomodulin • Acts with protein S to deactivate clotting factors Va and VIIIa – shuts down thrombin production • ± inhibit Cyk production • ± Prevent neutrophil activation • ± Inhibit leukocyte adhesion • ± Inhibit leukocyte rolling

32. PATHOPHYSIOLOGY • MICROCIRCULATION: • Despite aggressive resuscitation, normal blood pressure and adequate global 02 delivery, septic patients often persist in exhibiting signs of tissue hypoperfusion which may lead to acidosis and multiorgan failure D. Angus, CCM, 2003 • Macrocirculatory measurements fail to adequately assess the function of microvessles (<100υM)

33. PATHOPHYSIOLOGY • MICROCIRCULATION AND ENDOTHELIAL DERANGEMENTS IN SEPSIS: • ANIMAL MODELS: • decreased microcirculatory flow velocity • Increased heterogeneity of flow • Increased stopped flow vessels • Decreased density of perfused capillaries • Ellis, AJRCCM 2003 • Blood is effectively shunted from tissues

34. PATHOPHYSIOLOGY • MICROCIRCULATION AND ENDOTHELIAL DERANGEMENTS IN SEPSIS: • ARTERIOLES / CAPILLARIES / VENULES • Deregulation of vasomotor control • Endothelial injury • Coagulation • Disordered leukocyte trafficking

35. PATHOPHYSIOLOGY • MICROCIRCULATION AND ENDOTHELIAL DERANGEMENTS IN SEPSIS: • ENDOTHELIUM: CENTRAL ROLE • Regulation of microvessel thrombosis • Profibrinolysis • Leukocyte adherence NITRIC OXIDE • Microvascular tone • Permeability • Blood flow

36. PATHOPHYSIOLOGY • MICROCIRCULATION AND ENDOTHELIAL DERANGEMENTS IN SEPSIS: • ENDOTHELIUM: • Normally homeostatic • Sepsis: • Endothelial damage from Il-1, Il-6, TNF-α, oxidative stress • Increased Cyk release from endothelial cells • Loss of tight junctions • Edema • Tissue hypoxia • Leukocyte adhesion and rolling • RBCs: impaired deformability  aggregates  decreased O2 delivery

37. DIAGNOSIS • BASICS: • History • Physical exam • Labs: CBC • Cultures

38. DIAGNOSIS • BIOMARKERS • LACTATE • VENOUS OXYGEN SATURATION • PRO-CALCITONIN • CRP • TNF, IL-6, IL-1

39. DIAGNOSIS • LACTATE: • From anaerobic respiration • Absolute vs clearance: • Absolute lactates: • > 4 mmol/L predicted short term and in-hospital risk of death (Trzeciak ICM, 2007) • However other studies have shown lactates >8 in normotensive patients and > 18 in septic shock to be predictive

40. DIAGNOSIS • LACTATE: • Absolute: • Mickkelsen et al CCM 2009 • Septic shock • Initial lactate was associated with mortality independent of clinically apparent organ dysfunction and shock in patients with severe sepsis • 3 levels: low <2, intermediate 2-3.9, high >3.9 • OR: intermediate 2.05, high 4.87 in non-shock groups • OR: intermediate 3.27, high 4.87

41. DIAGNOSIS • LACTATE: • Clearance: • Nguyen et al CCM 2004 • Lactate clearance early in hospital course is associated with decreased mortality • Mortality reduction correlates with degree of lactate clearance • ~ 11% decrease in likelihood of mortality with every 10% decrease in the lactate (in 6 hrs)

42. DIAGNOSIS • ScvO2 • “gold standard” • But not validated • ScvO2 vs MvO2: • Higher in shock due to decreased oxygen extraction • Higher due to line position: • Coronary sinus flow • Redistribution of flow from splanchnic, renal& mesenteric beds • Some studies: 5-18% higher • Trends are the same • Needs to be studied

43. DIAGNOSIS • Procalcitonin: • Levels are elevated in sepsis • Source: little known • Serum calcitonin levels are normal • More accurate at diagnosing sepsis than CRP or Il-6 • Some studies have shown prognositic value for mortality

44. DIAGNOSIS • CRP: • Acute phase reactant from the liver • Increase with exposure to Il-1, Il-6 or TNF • Marker of systemic inflammation • Nutritional assessment

45. DIAGNOSIS • BIOMARKERS: • IL-1, IL-6, TNF • Not used in clinical practice • Cost • Value

46. DIAGNOSIS • ORTHOGONAL POLARIZING SPECTRAL IMAGING (OPS) • Polarized green light • 3mm depth • Visualization of the microcirculation (RBC transit) • Non-invasive: sublingual mucosa • Finicky: motion artifact, positioning • DeBacker et al 2002: decreased microvessel density and proportion of perfused vessels were common is sepsis and more severe in non-survivors

47. DIAGNOSIS • FLOWMETRY: • LASER DOPPLER FLOWMETRY: • Doppler flow to detect frequency shifts in laser light illuminating RBCs • Non-invasive • Finicky • ANIMAL MODELS: (Septic, hemorrhagic, cardiogenic shock) • Increased flow with resuscitation • Persistent low flow to liver, pancreas, kidneys • Regional flow disturbances persisted in the jejunum and colon

48. END ORGAN CHANGE • Myocardium: • Relative hypovolemia • Vasodilation • Insensible losses • Third spacing • Cardiovascular depression • RVEF LVEF • RVEDP  LVEDP • CO 20HR with normal SV • SVR

49. END ORGAN CHANGE • Myocardium: • Reversible depression: 40% pts • Resolves over ~ 10 days • Etiology: • Cyk • NO • Myocardial ischaemia with reperfusion injury • Increased coronary flow and net lactate consumption • Ventricular dilation: • Resolves over 10 days • Failure to dilate is a predictor of mortality

50. END ORGAN CHANGE • Acute Lung Injury (ALI): • Either pulmonary or extra-pulmonary etiology • Extrapulmonary: • Circulating Cyk and bacterial products activated endothelial cells which then become prothrombotic. • Leukocytes adhere and migrate into the alveolar space leading to further inflammation and release of inflammatory mediators • Pulmonary macrophages are activated and secrete Cyk • Type 1 pneumocyte damage leads to flooding of the alveolar airspace • Type 2 pneumocyte damage leads to loss of surfactant