Septic Shock pathophysiology basics Dr.T.V.Rao MD
Dr.T.V.Rao MD
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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
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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 approximatelyDr.T.V.Rao 25–50%. MD 3
Shock: Types • Hypovolemic • Septic (high CO, low SVRI) • Cardiogenic (high CVP) • Neurogenic • Anaphylactic • Adrenal insufficiency Dr.T.V.Rao MD
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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
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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.
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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 Dr.T.V.Rao MDCommittee. American College of Chest Physicians/Society of Critical Care Medicine. Chest, 101(6), 1644–1655.
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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.
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Clinical Spectrum of Infection Infection Bacteremia
Sepsis Severe Sepsis Septic Shock
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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
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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
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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
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Terminology Systemic Inflammatory Response Syndrome (SIRS) Temp > 38 or < 36 HR > 90 RR > 20 or PaCO2 < 32 WBC > 12 or < 4 or Bands > 10%
TWO out of four criteria acute change from baseline
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 Dr.T.V.Rao MDCommittee. American College of Chest Physicians/Society of Critical Care Medicine. Chest, 101(6), 1644–1655.
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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
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
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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.
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Parasite
Virus
Infection Fungus
Severe Sepsis
SIRS
Sepsis
shock
Severe SIRS Trauma
Bacteria BSI
Burns Dr.T.V.Rao MD
Adapted from SCCM ACCP Consensus Guidelines
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Where’s the infection ? Abdomen 15% Urine 10%
Lung 47%
Other 8% Culture Negative 20%
Bernard & Wheeler NEJM 336:912, 1997 Dr.T.V.Rao MD
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What’s the infection? Pure isolates, total n = 444 pts, 61% micro documented 80 70 60 50 Early Late
40 30 20 10 0 Gram pos
Gram neg
Cohen et al, J Infect Dis 1999 180:116
Fungal
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
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Sepsis and septic shock Bacterial infection Excessive host response
Host factors lead to cellular damage Organ damage
Death
How likely is it that the diagnosis of sepsis is being missed? Is it... Intensive Care Physicians (n=237)
Total (n=497)
Extremely likely
3%
3%
Very likely Somewhat likely
Not sure
51%
51%
Not very likely Not likely at all
29%
27%
16%
17%
1%
0%
0%
2%
Ramsay, Crit Care 2004 8:R409. Dr.T.V.Rao MD
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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
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Pathogenesis of Septic Shock Journal of Infection 1995; 30: 201-206.
MONOCYTE CD 14 Bacteria
LPS
LBP
TNF-A
ENDOTHELIAL CELL
LPS soluble CD 14
LPS LBP
LPS
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Management of Sepsis • Recognition • Supportive care • Source control • Antibiotics • Specific (adjunctive) therapy
Issues in the rational choice of antibiotics EFFICACY • Spectrum of activity
• Pharmacokinetics & pharmacodynamics • Patterns of resistance TOXICITY COST
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
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“Non-antibiotic” therapy for sepsis • Low dose steroids • Intensive insulin therapy – tight glycaemic control • Activated protein C
• Goal directed therapy
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
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Best of the References • Sepsis and Septic Shock, 2008 Prof J Cohen
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Dedicated Hand Washing Continues to Save Many Lives in Critical Care
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Brave and Committed Nurses, Doctors Save Many Lives in spite of Shock
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• Programme Created by Dr.T.V.Rao MD for Basic understanding in Septic Shock for Medical Students in the Developing World • Email •
[email protected] Dr.T.V.Rao MD
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