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Flashcards in Sepsis and viral infections Deck (26)
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1
Q

Sepsis

A
  • The body’s systemic response to infection: abnormal generalized inflammatory rxn (due to microbial products) in organs remote from initial insult
  • SIRS (systemic inflammatory response syndrome) + infection (of normally sterile sites) = sepsis
  • SIRS is 2 or more of: temp change (≥38 or ≤36), HR≥90, RR≥20, WBC≥12,000 or ≤4,000 (or 10% bands)
  • Septic shock when accompanied by hypotension (systolic BP 40 mmHg from baseline) despite fluid resuscitation
2
Q

Pathophysiology of sepsis

A
  • Triggered by infection (mostly GN and GP bacteria, can also be fungi)
  • First host response is walling off and killing by tissue macs, mast cells, dendritic cells + innate immune system
  • Also increase in procoagulants to wall off infection
  • Systemic response: fever, leukocytosis, APRs (acute phase reactants)
  • Severe sepsis: hypo perfusion of distant organs, dysfunction of those organs, hypotension
3
Q

Mediators of sepsis

A
  • GP bacteria: teichoic acid, lipoteichoic acid, peptidoglycan
  • GN bacteria: LPS (leads to production and secretion of inflammatory mediators TNF and IL1B)
  • In effect LPS endotoxin increases capillary permeability, leads to infiltration of PMNs, and local fibrin deposition to impede infection
4
Q

Host responses to sepsis

A
  • Microcirculatory and mitochondrial dysfunction
  • Activation or injury of vascular epithelium
  • Septic shock due to TNF and IL1
  • Complement activation, and repression of anticoagulation and fibrinolysis
  • The unbalance btwn coagulation and fibrinolysis can lead to DIC
  • Disordered microcirculation due to shunting of blood and microthrombi
5
Q

Clinical manifestations of sepsis

A
  • Systemic: fever, chills
  • Hemodynamic: tachychardia, hypotenision
  • Organ systems: endothelial damage, microthrombi, DIC (due to unbalanced hemostasis)
  • Lung damage leads to fluid leakage into interstitium and alveoli, inadequate air exchange and ARDS
  • Renal failure in kidney, jaundice due to liver failure, hemorrhagic necrosis from ischemia in intestines
  • CNS symptoms: confusion, delirium, stupor, coma
6
Q

Rx for sepsis

A
  • Medical emergency
  • Goal directed Rx: achieve adequate O2
  • Achieve adequate BP and end organ perfusion (fluid resuscitation, vasoactive agents)
  • Transfusions for anemia
  • RAPID eradication of microbes: draining or removing infectious foci, effective antimicrobial agents (broad spectrum)
  • Possible low doses of corticosteroids (hydrocortisone)
  • Modulation of harmful inflammatory response (Abs to endotoxin, TNF, ect)
7
Q

FUO: Fever of unknown origin

A
  • Fevers due to: exogenous pyrogens and endogenous pyrogens
  • Endogenous: IL1 and IL6, TNFa, CNF (ciliary neurotropic factor), INF
  • Classic FUO, nosocomial FUO (not present on admission), Neutropenic FUO (PMNs <500), immune deficient FUO, HIV-related FUO
8
Q

Classical FUO

A
  • Fever of >38.3 (101F) (lasting more than 3 weeks)

- No Dx after 3 days in hospital or 2 outpatient visits

9
Q

Etiologies of classic FUO

A
  • Mostly infections, neoplasms, connective tissue (CT) disease (often AID), others
  • Infectious FUO: abscess, endocarditis, granulomatous disease (TB, histoplasmosis, coccidiodomycosis, ect), viral infections (CMV, EBV, HIV, parvovirus B19, hepatitis), zoonoses (brucella, leptospirosis, lyme disease), typhoid fever, malaria, leshmania
10
Q

Viral hemorrhagic fever (VHF)

A
  • Severe multisystem syndrome
  • Vascular system is damaged and self-regulation impaired (accompanied by hemorrhage)
  • Some cases are mild others are fatal
  • Hemorrhage due to capillary leak, bleeding diathesis (DIC, hepatic damage, consumptive coagulopathy, primary marrow dysfunction)
  • Hemodynamic compromise leading to shock
  • Cause of all hemorrhagic fevers are enveloped RNA viruses (geographically restricted, survival depends on insect or animal host)
11
Q

Clinical symptoms of hemorrhagic fever

A
  • Fever, malaise, myalgia, exhaustion, headache, dizziness, vomiting, diarrhea
  • Also petechia, edema, bleeding, hypotension and shock
  • Bleeding under the skin, in internal organs, from mouth, eyes, or ears
  • Pts rarely die from blood loss, usually from shock
  • Shock leads to CNS malfunction, coma, delirium, and seizures
  • Some VHF are associated w/ kidney failure
12
Q

Causes of VHF

A
  • Flaviviridae: yellow fever, dengue
  • Arenaviridae: lassa fever
  • Filoviridae: ebola, marbug
  • Bunyaviridae: hantavirus, rift valley
13
Q

Yellow fever

A
  • Mosquito transmitted (africa and south america)
  • Replicates in LNs, spreads via blood to macrophages, liver, lung, kidney, adrenals, spleen
  • Leads to petechial hemorrhaging (liver damage + coagulation + thrombocytopenia + endothelial damage)
  • Jaundice due to liver damage
  • No Rx, only vaccine
14
Q

Lassa fever

A
  • Endemic in africa, host is a wild shrew-rat
  • Endothelial cell damage/leak
  • Platelet dysfunction
  • Cytokines and other mediators induce shock and inflammation
  • Majority only have non-specific flu symptoms
  • Most sever in pregnant women, deafness is a common sequela
  • Rx is supportive care and ribavirin
15
Q

Ebola

A
  • Endemic to africa
  • Sudden onset of fever, weakness, myalgias, headache, sore throat, vomiting, diarrhea, rash, impaired kidneys and liver
  • Fatality rate as high as 90%
  • Rx is supportive care (strict airborne and contact precautions)
16
Q

Eptein-bar virus (EBV)

A
  • A family of herpes viruses (HHV4), thus linear dsDNA, enveloped, 2 types (A and B)
  • DNA forms circular episomes in the nucleus (doesn’t integrate into host DNA)
  • Large enough to code for 100-200 proteins
17
Q

EBV pathogenesis

A
  • Primary infection from exposure to oral secretions from a seropositive individual
  • Infects B cells and nasopharyngeal epithelial cells
  • EBV receptor is CD21 (C3d GP)
  • Infected B cells cause intense CTL response
  • Most infected B cells are cleared but 1/50 million remain quiescently infected and serve as a life-long reservoir
  • 90% of adults are chronically infected
18
Q

EBV latent infection 1

A
  • No virion produced, but viral DNA present (in episomal form)
  • 11 genes expressed during latency, gene products (EBNA, LMP) convert B lymphocytes into immortalized lymphoblastic cells capable of continuous growth
  • This growth-transformation can lead to malignant disease
  • These immortalized B cells can be seen in the circulation, and are continually cleared by the immune system
19
Q

EBV latent infection 2

A
  • Lifelong carrier state develops: low-grade infection kept in check by immune system
  • Continuous but low-grade virus replication and shedding from epithelial cells of pharynx
  • In acute infection up to 20% of B cells in circulation express EBNA
  • Immune response involves both cell-mediated (CD4, CD8, NKCs) and humoral systems (IgM, IgG against viral capsid Ag: or VCA)
  • Early Ags (weeks to months): Anti-EA, EBV nuclear Ag
20
Q

Acute EBV infection

A
  • Children are either asymptomatic or have FUO
  • Adolescents and adults have 30-50% chance of developing infectious mononucleosis (IM) w/ acute infection
  • IM presentation (incubation 4-6 wks): fever, lymphadenopathy, pharyngitis, mild hepatitis (usually self-limiting disease)
  • IM can be due to EBV (90%), or acute CMV (10%)
21
Q

Lab findings in acute IM

A
  • Lymphocytosis: >50% mononuclear cells
  • Atypical lymphocytes: CTLs directed against infected atypical B cells
  • How to distinguish vs strep: in EBV the mononuclear cells are increased, in strep the PMNs are increased
  • Mild hepatitis: elevation of ALT/AST, occasional jaundice
  • Positive heterophile Ab test (will be negative in CMV IM)
  • Heterophile test (monospot): agglutination rxn of Ags horse erythrocytes, represent non-specific B cell activation (positive in 80-90% of EBV IM)
22
Q

Chronic IM

A
  • Symptoms last up to 4 mo
  • May progress to death from lymphoproliferative disease or lymphoma (burkitt’s, possibly HL)
  • Chronic fatigue syndrome not associated w/ EBV
23
Q

EBV associated malignancies

A
  • Burkitt’s lymphoma
  • B cell lymphoproliferative disease (BLPD)
  • Hodkin’s lymphoma
  • Nasopharyngeal CA
  • Gastric CA
  • T cell lymphoma
24
Q

Hemophagocytic lymphohistiocytosis

A
  • Fever, hepatosplenomegaly, rash, respiratory distress, hypotension
  • Cytopenia in 2 cell lines (usually anemia and thrombocytopenia)
  • Hypertriglyceridemia, hypofibrinogenemia
  • Hemophagocytosis w/o evidence of malignancy
25
Q

Other chronic EBV associations

A
  • X-linked lymphoproliferative syndrome occurs exclusively in males w/ inherited defective X chromosome (accounts for 50% of fatal IM cases)
  • If someone becomes immunocompromised the virus may become reactive, this could lead to lymphoproliferative disease or lymphoma
  • AIDS patients can get oral hairy leukoplakia and various NHL including CNS lymphoma
26
Q

Shock

A
  • Causes: cardiac, hypovolemic, distributive (neurogenic, anaphylaxis), obstructive
  • Progression: initial stage (hypoperfusion and lactic acidosis), compensatory shock (hyperventilation, vasoconstriction), progressive shock (leakage of fluid into tissues, ischemia)