Septic shock Pathophysiology

Septic shock Pathophysiology

1. Septic Shock pathophysiology basics Dr.T.V.Rao MD Dr.T.V.Rao MD 1

2. Background In 1914, Schottmueller wrote, “Septicaemia is a state of microbial invasion from a portal of entry into the blood stream which causes sign of illness.” The definition did not change much over the years, because the terms sepsis and septicaemia referred to several ill-defined clinical conditions present in a patient with bacteraemia. Dr.T.V.Rao MD 2

3. Definition of Septic Shock Septic shock is a medical condition as a result of severe infection and sepsis, though the microbe may be systemic or localized to a particular site . It can cause multiple organ dysfunction syndrome (formerly known as multiple organ failure) and death. Its most common victims are children, immunocompromised individuals, and the elderly, as their immune systems cannot deal with the infection as effectively as those of healthy adults. Frequently, patients suffering from septic shock are cared for in intensive care units. The mortality rate from septic shock is approximately 25–50 %. Dr.T.V.Rao MD 3

4. Shock: Types Hypovolemic Septic (high CO, low SVRI) Cardiogenic (high CVP) Neurogenic Anaphylactic Adrenal insufficiency Dr.T.V.Rao MD 4

5. Definitions Infection: microbial phenomenon characterised by an inflammatory response to the presence of micro organisms or the invasion of normally sterile host tissue by these organisms Bacteraemia: the presence of bacteria in the bloodstream Septicaemia: no longer used ACCP/SCCM Consensus Conference: Bone et al, Chest 1992 101:1644 Dr.T.V.Rao MD 5

6. Definition Shock :- When the cardiovascular system fails to deliver enough oxygen and nutrients to meet cellular metabolic needs. Sepsis :- Presence of bacteria in the blood stream. Septic Shock :- Begins with the development of septicaemia usually from bacterial infections, but can be viral in origin. This is the most common type of Distributive Shock. Dr.T.V.Rao MD 6

7. Infection, SiRS, Sepsis Bone, R., Balk, R., Cerra, F., Dellinger, R., Fein, A., Knaus, W., Schein, R., et al. (1992). Definitions for sepsis and organ failure and guidelines for the use of innovative therapies in sepsis. The ACCP/SCCM Consensus Conference Committee. American College of Chest Physicians/Society of Critical Care Medicine. Chest , 101 (6), 1644–1655. Dr.T.V.Rao MD 7

8. Causes of Septic Shock As mentioned any type of bacteria in the bloodstream causes septic shock and this can occur from many infections, for example: The pope died from septic shock caused by a urinary infection Simon has a chest infection Other common reasons according to Collins (2000) are, major abdominal surgery and an invasive catheter. Dr.T.V.Rao MD 8

9. Clinical Spectrum of Infection Infection Sepsis Severe Sepsis Septic Shock Bacteremia Dr.T.V.Rao MD 9

10. Aetiology of Septic shock When bacteria or viruses are present in the bloodstream, the condition is known as bacteraemia or Viremia. Sepsis is a constellation of symptoms secondary to infection that manifest as disruptions in heart rate, respiratory rate, temperature and WBC .. Once severe sepsis worsens to the point where blood pressure can no longer be maintained with intravenous fluids alone, then the criteria have been met for septic shock. The precipitating infections which may lead to septic shock if severe enough include appendicitis, pneumonia, bacteraemia, diverticulitis, pyelonephritis, meningitis, pancreatitis, and necrotizing fasciitis. Dr.T.V.Rao MD 10

11. Systemic inflammatory response syndrome ( SIRS) Systemic inflammatory response syndrome (SIRS) is a term that was developed in an attempt to describe the clinical manifestations that result from the systemic response to infection. Criteria for SIRS are considered to be met if at least 2 of the following 4 clinical findings are present: Temperature greater than 38°C (100.4°F) or less than 36°C (96.8°F) Heart rate (HR) greater than 90 beats per minute (bpm) Respiratory rate (RR) greater than 20 breaths per minute or arterial carbon dioxide tension (PaCO2) lower than 32 mm Hg White blood cell (WBC) count higher than 12,000/µL or lower than 4000/µL, or 10% immature (band) forms Dr.T.V.Rao MD 11

12. Some Characteristics of Septic Shock Systemic vasodilation and hypotension Tachycardia; depressed contractility Vascular leakage and oedema; hypovolemic Compromised nutrient blood flow to organs Disseminated intravascular coagulation Abnormal blood gases and acidosis Respiratory distress and multiple organ failure Dr.T.V.Rao MD 12

13. Terminology Systemic Inflammatory Response Syndrome (SIRS ) Temp > 38 or < 36 HR > 90 RR > 20 or PaCO2 < 32 WBC > 12 or < 4 or Bands > 10% Sepsis The systemic inflammatory response to infection. Severe Sepsis Organ dysfunction secondary to Sepsis. e.g. hypoperfusion, hypotension, acute lung injury, encephalopathy, acute kidney injury, coagulopathy . Septic Shock Hypotension secondary to Sepsis that is resistant to adequate fluid administration and associated with hypoperfusion. Bone, R., Balk, R., Cerra, F., Dellinger, R., Fein, A., Knaus, W., Schein, R., et al. (1992). Definitions for sepsis and organ failure and guidelines for the use of innovative therapies in sepsis. The ACCP/SCCM Consensus Conference Committee. American College of Chest Physicians/Society of Critical Care Medicine. Chest , 101 (6), 1644–1655. TWO out of four criteria acute change from baseline Dr.T.V.Rao MD 13

14. Changing criteria of sepsis With sepsis, at least 1 of the following manifestations of inadequate organ function/perfusion is typically included : Alteration in mental state Hypoxemia (arterial oxygen tension [PaO2] < 72 mm Hg at fraction of inspired oxygen [FiO2] 0.21; overt pulmonary disease not the direct cause of hypoxemia) Elevated plasma lactate level Oliguria (urine output < 30 mL or 0.5 mL/kg for at least 1 h) Dr.T.V.Rao MD 14

15. Pathophysiology The nidus of infection: Localized infections ( otitis, pneumonia, meningitis etc.,) Colonization of mucosal and invasion ( Hib, menigococci) Occult bacteremia ( 3mo to 3 years ) Nosocomial : ‘at risk patients’ Dr.T.V.Rao MD 15

16. Causes of Septic Shock As mentioned any type of bacteria in the bloodstream causes septic shock and this can occur from many infections, for example: The pope died from septic shock caused by a urinary infection Simon has a chest infection Other common reasons according to Collins (2000) are, major abdominal surgery and an invasive catheter. Dr.T.V.Rao MD 16

17. Infection Parasite Virus Fungus Bacteria Trauma Burns Sepsis SIRS Severe Sepsis Severe SIRS Adapted from SCCM ACCP Consensus Guidelines shock BSI Dr.T.V.Rao MD 17

18. Where’s the infection ? Bernard & Wheeler NEJM 336:912, 1997 Dr.T.V.Rao MD 18

19. What’s the infection? Pure isolates, total n = 444 pts, 61% micro documented Cohen et al, J Infect Dis 1999 180:116

20. Data from Bochud et al.42

21. Septic Shock Septic shock- once a uniformly fatal condition with 100% mortality. Present recovery rates are up to 50%. Significance: Frequent occurrence and high mortality. Dr.T.V.Rao MD 21

22. Bacterial infection Sepsis and septic shock Excessive host response Host factors lead to cellular damage Organ damage Death

23. How likely is it that the diagnosis of sepsis is being missed? Is it... Extremely likely Very likely Somewhat likely Not very likely Not likely at all Not sure Total (n=497) Intensive Care Physicians (n=237) Ramsay, Crit Care 2004 8:R409 . Dr.T.V.Rao MD 23

24. Microbial Triggers Gram-negative bacteria : lipopolysaccharide Gram-positive bacteria Lipoteichoic acid/cell wall muramyl peptides – Superatigens Staphylococcal Toxic Shock Syndrome Toxin, TSST Streptococcal pyrogenic exotoxin , SPE Dr.T.V.Rao MD 24

25. Pathogenesis of Septic Shock LPS LBP LPS ENDOTHELIAL CELL Bacteria LPS LBP LPS CD 14 MONOCYTE soluble CD 14 TNF-A Journal of Infection 1995; 30: 201-206. Dr.T.V.Rao MD 25

26. Management of Sepsis Recognition Supportive care Source control Antibiotics Specific (adjunctive) therapy

27. Issues in the rational choice of antibiotics EFFICACY Spectrum of activity Pharmacokinetics & pharmacodynamics Patterns of resistance TOXICITY COST

28. Choosing antibiotics in sepsis There is no, single, “best” regimen Consider the site of the infection Consider which organisms most often cause infection at that site Choose antibiotic(s) with the appropriate spectrum After obtaining cultures, give antibiotics quickly and empirically at appropriate dose Dr.T.V.Rao MD 28

29. “ Non-antibiotic” therapy for sepsis Low dose steroids Intensive insulin therapy – tight glycaemic control Activated protein C Goal directed therapy

30. Shock: Realize the Facts Shock = inadequate tissue perfusion Types of shock: hypovolemic, septic, cardiogenic, neurogenic, anaphylactic Signs of shock: altered MS, tachycardia, hypotension, tachypnea, low UOP Always start with ABCs Resuscitation begins with fluid Dr.T.V.Rao MD 30

31. Best of the References Sepsis and Septic Shock, 2008 Prof J Cohen Dr.T.V.Rao MD 31

32. Dedicated Hand Washing Continues to Save Many Lives in Critical Care Dr.T.V.Rao MD 32

33. Brave and Committed Nurses, Doctors Save Many Lives in spite of Shock Dr.T.V.Rao MD 33