Viva - Influenza Flashcards

1
Q

Describe the flu virus

A

Influenza is an orthomyxovirus

Consists of 8 strands of RNA protected by an M1 matrix protein.

An envelope derived from the host cell envelops this, two types of glycoprotein are embedded

H and N (as in the H1N1) - these determine whether it is A or B and the subtype eg/ H1N1

These also act as the target of antiviral agents

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2
Q

What does the H1N1 nomenclature mean

A

These are the glycoproteins embedded within the envelope:

H - Haemagglutinin - 16 different kinds.

N - Neuraminidase - 9 different kinds

H: facilitates binding of virus to Host respiratory epithelial cells

N: allows release of new viral particles from infected cells

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3
Q

What is antigenic drift

A

Describes small genetic changes that happen continuously over time as the virus replicates and produces viruses closely related to one another.

They share the shame antigenic properties.

An immune system with prior exposure to one that is similar will recognise it and respond

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4
Q

What is antigenic shift

A

An abrupt major change that results in a new Haemagglutinin and/or Neuroaminidase producing a new influenza A subtype.

Have little or no immunity against the new subtype…pandemic results.

Also occurs when H/N combination emerges from animal popuation that is so different from the same subtype in humans that most people do not have immunity to it.

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5
Q

Which flu can undergo antigenic shifts and drifts

A

Influenza A

Undergoes periodic changes in antigenic characteristics of its glycoproteins.

B has a less propensity for this, and actually only drift in the Haemagluttinin has been described in B.

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6
Q

Incubation period of influenza

A

1.5 - 3 days

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7
Q

Presentation of influenze

A

incubation 1.5 - 3 days

Mild: afebrile upper resp tract infection all the way to fulminant viral pneumonia.

Non-specifically as self limiting in children and adults

Fever malaise, myalgia, arthralgia, headache, cough, upper resp symptoms,

GI commonly abdo pain, D&V

More seriously:

Dypnoea, heamoptysis, puruluent sputum, recurrent lower tract symtpoms, dehydration, altered mentation,

Suggest progression to severe disease or complications

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8
Q

Complications of influenza

A

Viral pneumonitis with severe hypoxaemia and ARDS requiring ITU.

Intubation often needed in first 24 hours

CXR - diffuse interstitial and alveolar shadowing

CT - ground glass opacities, air bronchograms and alveloar consolidation

Shock and AKI

CURB-65 will not help here.

2) Bacterial superadded infection
1/5th of patients.
Usually s.aureus (MRSA), st. pneumoniae, St pyogenes

3) Decompensation of pre-existing illness

4) less common: neuro:
Altered mental state, seizures, encephalitis, post infectious encephalopathy

5) viral myocarditis - unusual but poor prognosis

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9
Q

Who are the high risk patients

A

1) Extreme age <5 (especially <2 and high hospitalisation in <1)
or >65 (in 2009, they had highest fatality but lowest rate of infection

2) Pregnant - atypical presentation, increased hospital risk, highest at 3rd trimester.

Risk of severe illness, miscarraige, pre-term labour, fetal distress

3) Chronic diseases, ashthma, COPD, CF,
CCF, CAD
Dialysis, cirrhotic liver disease DM

4) morbid obesity
5) immunocomprimised

Chemo/steroids
HIV
Transplant
Malnutrition

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10
Q

Diagnosis of influenza

A

Suggestive clinical picture

Nasopharyngeal swab/aspirates for reatime RT-PCR for viral RNA

BAL better.

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11
Q

Management of influenza - outline principles

A

1) Manage with ABCDE….
2) Specific organ support

A) Strict infection control
B - Antiviral therapy
C -Antibiotic therapy if superadded infection
D - General principles - VTE, enteral feeding, acid suppression, VAP bundles
E - PEP

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12
Q

What are the infecion control principles

A

Isolate in side room - at least 24 hours after resolution of fever, or 7 days after onset of illness (whichever is longer)

Barrier nurse, strict hand hygeine
AGPs needs full protective kit and PPE, FFP3 or respirators, use as few staff as possible

More:
Year flu vaccines
PPE and hand hygeins, gloves, gown (or apron) goggles, surgical mask

Circuits: Disposable circuit, bacterial filter
Closed circuit suction uses respirators if breaking circuit

NIV - only turn on when mask is in situ
Avoid humidification
Negative pressure preferable

Negative pressure rooms (allow air in but not out the room) used with airborne infectious diseases, flu, TB

Positive pressure - isolate immunocomprimised

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13
Q

When to initiate antivirals

A

in 2009:
Suspected/confirmed H1N1 who were sevrely ill or high risk or had complications

Treatment with Neuraminidase inhibitors reduced severity and mortality

Resitstant to amantidine

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14
Q

Evidence for steroids

A

None

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15
Q

When to give PEP

A

Close contact with confirmed or suspected case
HCPs
Increased risk of developing complications

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16
Q

Managing severe hypoxic resp failure

A

Treat as per any patient with ARDS

Appropirate use of sedation
Paralyse in first 24-48 hours
Make use of P/F ratio

Aim PaO2 >8, titrates FiO2 and PEEP as per ARDSnet protocol
Accept 7-8 if FiO2>0.8 AND no evidence of organ dysunction

Vent: TV 4-6ml/kg
Pplat<30
Permissive Hypercapnia (allow pH>7.25)

Negative or neutral balance
Use of dieuretics or RRT

17
Q

When to refer ECMO

A

Oxygenation or Ventilatory criteria:

Oxy:
Cant get PaO2>8 with FiO2>8 and/or PEEP>15 on days 0-2
Can maintain PaO2>8 on days 2-7

Vent:
Cant maintain TV< 6ml/kg or Pplat<30 and pH>7.25 on days 0-2
Uncompensated resp acidosis <7.2 despite optimal therapy

BPF
High risk failure

18
Q

How would you manage resources

A

Stop elective ops

Retain/relocate staff

Create extra ICU beds, theatres etc

Declare a Major Incident

2009 did say to use SOFA as a traige >11 dont admit
In COVID, CFS was a possibility (6)

19
Q

Predictors of poor outcome

A

Older age
Co-morbidities
Need for ventilation

20
Q

Mortality and ICU mort

A

<0.05% globally (0.026% in UK)

9-31% of hospitalised patients went to ITU

Mortality in ITU subset up to 46%