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HAEM/IMMUNOLOGY > Infectious diseases > Flashcards

Infectious diseases Flashcards

1
Q

What is systemic inflammatory response syndrome? SIRS

A

SIRS - 2/4 below

  • temp >38 or <36
  • HR >90
  • RR > 30 or CO2 <32mmhg
  • WCC >12,000 or <4000
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2
Q

What is sepsis and septic shock?

A

Sepsis - infection + 2 of (tachypnea, low BP, altered mental status)
Septic shock - sepsis + vasopressors + lactate >2

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3
Q

What is the transition of infection/SIRS into sepsis influenced by?

A
  • organisms virulence and burden
  • immune system: age, immune suppression
  • organ vulnerability
  • timeliness of interventions
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4
Q

In the steps leading up to sepsis, what influences pathogen entry and survival?

A
  • tissue contamination
  • foreign body insertion
  • immune status
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5
Q

What does activation of the innate immune system involve?

A
  • pro inflammatory cytokines, TNF-a, il1+6 activate immune cells
  • ROS, NO, proteases - bacterial killing, vasodilation and permeability
  • complement activated, mediates activation of leukocytes to attack organism
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6
Q

During infection, what alterations occur in the coagulation and endothelial system?

A

Activated endothelium - adhesion and migration, tissue edema
Coagulations - alterations = increase in procoagulant factors, and reduced anticoagulants

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7
Q

How does sepsis cause relative and absolute reduction in circulating volume?

A

Vasodilation and increased permeability

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8
Q

What organ dysfunctions are associated with sepsis?

A

Heart: reduced contractility, hypo perfusion and shock

Pericapillary edema - impaired oxygen delivery

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9
Q

How can bacteremia be classified? (5)

A
  1. site of origin - primary = endovascular, 2’= extravascular
  2. duration - transient, intermittent and continuous
  3. type - gram +ve/-ve, polymicrobial etc
  4. place of acquisition - community acquired or nosocomial
  5. patient groups - well, nosocomial, elderly, immunosuppressed
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10
Q

What are the exogenous mediators of bacteremia and septic shock?

A

Endotoxin - lipopolysacharide of gm-ve bacteria
Gram +ve - lipotechoic acid and peptidoglycan
Viruses - lyse host cells, complement and cell death and proinflammatory response via CD14/TLR3 or TLR4

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11
Q

What are signs and symptoms of sepsis/bacteremia in patients?

A
  • abrupt onset
  • shaking, chills, rigor
  • fever on hypothermia
    Less common - dyspnoea, delirium, renal failure, rash/toxic shock/DIC/purpura fulminant
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12
Q

How is a diagnosis of bacteremia made?

A

3 collections of blood cultures

  • from different venopuncture sites within first 2 hours of presentation
  • at least one aerobic and one anaerobic
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13
Q

What is the treatment of sepsis?

A

Pathogen - broad spectrum beta lactam usually started early then switch to most effective agent following pathogen identification
Host - IV fluids, inotropic, mechanical ventilation, glucocorticoids to curb inflamm.

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14
Q

How can sepsis be prevented for community acquired and nosocomial bacteraemia?

A

Community - vaccines

Nosocomial - minimising iatrogenic infection, hand hygiene, ventilator, IV, catheter mgmt

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15
Q

What can cause immunocompromised?

A
  1. Disease - acute leukaemia, AIDS, RA, diabetes

2. Iatrogenic - chemotherapy, DMARDs, steroids

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16
Q

What cells are involved in cell mediated and humoral immunity?

A

Cell mediated - neutrophils, NK, monocytes

Humoral - Antibodies, complement, lysosyme

17
Q

What is mild, moderate and severe neutropenia?

A

Mild: 1000-1500 cells/uL
Mod: 500-1000 cells/uL
Severe: <500 cells/uL

18
Q

What are causes of neutropenia? and what are the associated defects?

A

Inherited
Acquired: drug induced cytotoxics, bone marrow irradiation, cancer related, plastics anaemia

Defects - chemotaxis, opsonisation, intracellular killing

19
Q

What are the effects of bone marrow irradiation/chemotherapy on the immune system?

A

Following irradiation, 14 days of neutropenia
First 12 days - chemo causes mucositis, so higher risk of gram -ve, streptococci, fungi and HSV infection
Later - graft vs host disease can develop where donor cells attack the body — immunosuppressants are given which immunosuppressed cell mediated immunity even more

20
Q

How may a patient with neutropenic sepsis present?

A
  • fever
  • hypothermia
  • hypotension
  • clinical deterioration
21
Q

What is a neutropenic fever?

A

temp >38.3 C OR sustained temp >38C for more than 1 hour, occurring in a patient with neutrophil count <500 cells/uL

22
Q

Incidence of fever in a neutropenic patient increases with:

A
  • severity of neutropenia
  • prolonged duration of therapy
  • comorbid factors, catheter, mucositis, use of monocloncal a/b
23
Q

What are the most common causes of neutropenic fever and sites of infection?

A

Causes - gm-ve bacilli (P.Aeruginosa) and now gm+ve (s. aureus, s. epidermis, streptococci and enterococci)

Sites: bacteremia, pneumonia, pharyngitis, sinusitis, perianal lesions, skin lesions

24
Q

How is a febrile neutropenic patient evaluated?

A

Evaluated: microbiology with 2+ sets of cultures, sputum and urine gram stain and culture AND imaging - CXR+ CAT

25
Q

How is febrile neutropenic patient managed?

A

MGMT:
Urgently broad spectrum antibiotics IV (cover pseudomonas)
- tazocin (or cefepime or ceftazidime)
- + vancomycin if MRSA/patient in shock
- targeted treatment when pathogen identified

If fever persists past day 4 of a/b then consider fungal infection
- yeast (candida)
- mould (aspergillus, fusarium, zygomycetes)
Empiric anti fungal therapy = voriconazole, amphoterecin B, caspofungin

26
Q

What are 3 ways to prevent neutropenic infection?

A
  1. modify environment - +ve pressure room, no flowers
  2. Meticulous line mgmt
  3. prophylaxis - A/B, antifungals, anti viral
27
Q

What are the 3 stages at which infection can occur following solid organ transplant?

A
  1. Nosocomial/technical (donor or recipient) <1 month
  2. Activation of latent infection 1-6month
  3. Community acquired >6 month
28
Q

What is the importance of the spleen in immune function?

A
  • Produces IgM memory B cells
  • sequesters opsonised encapsulated bacteria
  • modulates effects of cytokines released during sepsis
29
Q

What infections are splenectomy patients at risk of getting?

A
  • encapsulated bacteria
  • malaria and babieosis
  • capnocytophagia
  • S. aureus and gram -ve’s
30
Q

How might patients with overwhelming post splenectomy infection present?

A
  1. fever, shivering, myalgia
  2. vomiting, diarrhoea, headache
  3. septic stick, DIC, multi organ failure
  4. Death (40-70% within in 24hours)
31
Q

Patients with hyposplenia/splectomy have a 5% lifetime risk of developing:

A

Sepsis, pneumonia, meningitis

32
Q

What is the mgmt and prevention of OPSI?

A

MGMT - recognise symptoms, resuscitation with fluid, cultures (blood, urine, CSF), empiric antibiotics - CEFTRIAXONE +VANCOMYCIN to cover s. pneumoniae, N. meningitides, H. influenza

Prevention - vaccinate, prophylactic a/b, SOS antibiotics (amoxycillin)

HAEM/IMMUNOLOGY (5 decks)

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