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3rd year > Infection > Flashcards

Infection Flashcards

1
Q

How does HIV spread?

A 
Sexual transmission 
Injection drug misuse
Blood products 
Vertical transmission 
Organ transplant
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2
Q

What does HIV do in terms of immunology?

A

Infects and destroys cells of the immune system especially the T-helper cells that are CD4+.

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3
Q

What does the CD4 count tell us about the illness?

A

The lower the CD4 count - the greater the severity of the illness.
AIDS occurs at CD4 <200

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4
Q

How is HIV classified?

A

Clinical staging:
Stage 1 - asymptomatic.

Stage 2 - Weight loss <10% body weight. Minor mucocutaneous manifestations. Recurrent upper respiratory tract infections.

Stage 3 - Weight loss >10% body weight. Unexplained chronic diarrhoea > 1 month. Unexplained prolonged fever >1 month. Oral thrush. Severe bacterial infections. (bedridden)

Stage 4 - HIV wasting syndrome. Toxoplasmosis of the brain. Herpes simplex virus infection. Candidasis of the oesophagus, trachea. HIV encephalopathy.
Bedridden <50% of day during last month.

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5
Q

What is the natural history time line of HIV?

A 
Acute infection 
Asymptomatic 
HIV related illnesses
AIDS defining illness 
Death
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6
Q

How does primary HIV present?

A 
Abrupt onset 2-4 weeks post exposure. 
Symptoms generally non-specific:
Flu-like illness
Fever
Malaise and lethargy 
Pharyngitis 
Lymphadenopathy 
Toxic exanthema
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7
Q

What is Pneumocystis jiroveci pneumonia?

A

Commonest late stage (AIDS) infection.
CD4 cell count usually <200.
Classical history of dry cough and increasing breathlessness over several weeks.

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8
Q

What investigations are done for Pneumocystis jiroveci pneumonia?

A

Chest X-ray

Induced sputum or broncoscopy for PCR.

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9
Q

How is PJP treated?

A

Cotrimoxazole
Pentamidine
Prophylaxis until CD4 > 200.

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10
Q

How is HIV treated?

A

Combination Antiretroviral therapy (cART) at least 3 drugs from at least 2 groups.

  • side effects can be significant.
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11
Q

When should treatment begin?

A

All patients at diagnosis regardless of CD4 and viral load.

Any pregnant woman - start before 3rd trimester.

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12
Q

How long is treatment needed for HIV?

A

Life long. Treatment may need to be changed from time to time but will always need to be taking some form of antiviral medication.

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13
Q

Why do treatments for HIV fail?

A

Poor adherence leads to viral mutation and resistance.

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14
Q

What type of antiviral drugs are there?

A

Nucleoside reverse transcriptase inhibitors - marrow toxicity, neuropathy, lipodystrophy.

Non-nucleoside reverse transcriptase inhibitors - skin rashes, hypersensitivity, drug interactions.

Protease inhibitors - drug interactions, diarrhoea, hyperlipidemia.

Integrase inhibitors - disturbed sleep, rashes.

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15
Q

What are the challenges of HIV care?

A 
Osteoporosis 
Cognitive impairment 
Malignancy 
Renal disease 
Ischaemic heart disease
Diabetes mellitus
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16
Q

How can HIV be prevented?

A 
Behaviour change and condoms. 
Circumcision 
Treatment vs prevention 
- VL undetectable = untrasmissable. 
Pre-exposure prophylaxis (PrEP)
Post-exposure prophylaxis for sexual exposure (PEPSE)
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17
Q

What is the definition of Sepsis?

A

Life-threatening organ dysfunction caused by dysregulated host response to infection.

18
Q

What are the stages of sepsis?

A

SIRS - temp >38, HR > 90, WBCs >12,000.

Sepsis = SIRS and infection

Severe Sepsis = Sepsis and end organ damage.

Septic Shock = Severe sepsis and hypotension

19
Q

What is Septic shock?

A

Identified with clinical construct of sepsis with persisting hypotension requiring vasopressors to maintain MAP>65mmHg and having serum lactate of >2.
Hospital mortality of 40%.

20
Q

What is qSOFA?

A

Patients with suspected infection who are likely to have prolonged ICU stay or die in the hospital can be promptly identified using this criteria.

Score of >2 suggest a greater risk of poor outcome.

21
Q

What is the pathophysiology behind sepsis?

A

uncontrolled inflammatory response.
Patients have features consistent with immunosuppression.
- loss of delayed hypersensitivity, inability to clear infection.

Probable change of the sepsis syndrome over time.
Initially increase in inflammatory mediators.
Later, shift toward an anti-inflammatory immunosuppressive phase.

22
Q

What is the first phase in the pathogenesis of sepsis?

A

Release of bacterial toxins:

May or may not be neutralised and cleared by existing immune system.
Commonly released toxins = gram negative - LPS.
Gram positive - MAMP
Superantigens - Staphloccocal toxic shock syndrome toxin.

23
Q

What is the 2nd phase in the pathogenesis of sepsis?

A

Release of mediators in response to infection:

Effects of infections due to endotoxin release.
Effects of infections due to exotoxin release.
Mediator role of sepsis.

24
Q

What are the mediator role in sepsis? (Th1 vs Th2)

A

Pro-inflammatory mediators - causes inflammatory response that characterises sepsis.

Compensatory anti-inflammatory reaction - can cause immunoparalysis.

25
Q

What is phase 3 in pathogenesis of sepsis?

A

Effects of specific excessive mediators:

Pro-inflammatory mediators:

  • promote endothelial cell
  • release of arachidonic acid metabolites.
  • Complement activation.
  • Vasodilatation of blood vessels by NO.
  • Increase coagulation by release of tissue factors and membrane coagulants.
  • Cause hyperthermia.

Anti-inflammatory mediators:

  • Inhibit TNF alpha
  • Augment acute phase reaction.
  • inhibit activation of coagulation system.
  • Provide negative feedback mechanisms to pro-inflammatory mediators.
26
Q

What happens when the pro-inflammatory response is greater than compensatory anti-inflammatory response?

A

Septic Shock with multi-organ failure and death.

27
Q

What happens when the compensatory anti-inflammatory response is greater than pro-inflammatory?

A

Immunoparalysis with uncontrolled infection and multiorgan failure.

28
Q

What does the clinical features of sepsis depend on?

A

Number of factors:
Host.
Organsim.
Environment.

29
Q

What are the general features of sepsis?

A

Fever >38 - presenting as chills, rigors, flushes, cold sweats, night sweats.

Hypothermia <36 - especially in the elderly and very young children.

Tachycardia >90 per min
Tachypnoea > 20/min
Altered mental status - especially elderly.
Hyperglycaemia > 8 in absence of diabetes.

30
Q

What are the inflammatory variable in sepsis?

A

Leucocytosis
Leucopenia
High CRP
High Prolactin

31
Q

What are the organ dysfunction variable in sepsis?

A 
Arterial hypoxaemia 
Oliguria 
Creatinine increase compared to baseline.
Coagulation abnormalities.
ileus (intestinal obstruct)
Thrombocytopenia (low platelet)
Hyperbilirubinaemia
32
Q

Tissue perfusion variables in sepsis

A

High lactate

Skin mottling and reduced capillary perfusion.

33
Q

Effect of host on sepsis presentation

A

Age
Co-morbitdities (COPD, DM)
Immunosuppression
Previous surgery

34
Q

Effect of organism on presentation of sepsis

A

Gram positive vs Gram negative.
Virulence factors
Bioburden.

35
Q

What is the sepsis 6?

A 
Oxygen 
Blood cultures 
Antibiotics 
Fluid challenge
Lactate
Urine output
36
Q

Take 3: Give 3

A

Take: Blood cultures
Blood lactate
Measure urine output

Give: oxygen aim for 94-98%
IV antibiotics
IV fluid challenge

37
Q

Why take blood cultures, lactate and urine output?

A

BC - Make microbiological diagnosis (30-50% positive)
- if spike in temp, take 2 sets.

Lactate - marker of generalised hypoperfusion / severe sepsis/ poorer prognosis.
Type A - hypoperfusion. Type B - mitochondrial toxins.

Low urine output - marker of renal dysfunction.

38
Q

What antibiotics are chosen in sepsis?

A

Based on working diagnosis from history and examination.

Follow local antibiotic guidelines.

Consider allergy, previous MRSA, ESBL, and toxicity.

39
Q

What is given in IV fluids for sepsis?

A

30ml/kg fluid challenge

2.1L 70kg patient.

40
Q

When is HDU referral considered in sepsis?

A 
Low BP responsive to fluids 
Lactate >2 despite fluid resuscitation. 
Elevated creatinine 
Oliguria 
Liver dysfunction 
Bilateral infiltrates, hypoxaemia.
41
Q

When is ITU considered for sepsis?

A

Septic shock
Multi-organ failure
Requires sedation, intubation and ventilation.

3rd year (22 decks)

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