Infection and immunity Flashcards
When assessing a febrile child, what questions should you consider?
How is fever identified in children? How old is the child? Are there risk factors for infection? How ill is the child? Is there a rash? Is there a focus for infection?
How is fever measured in children in hospital?
The parents will usually know but in hospital:
<4 wks old by an electronic thermometer in the axilla
4 weeks to 5 years by an electronic thermometer in the axilla or infrared tympanic thermometer
What type of infection in febrile infants <3 months old?
Often present with non-specific symptoms and have bacterial infection, uncommon to have viral infection due to passive immunity from their mother. Unless a clear cause is shown, require urgent sepsis screening and IV antibiotics
What are some risk factors for infection>
Illness of other family members
Prevalence of illness in the community
Unimmunised
Recent travel abroad, e.g. malaria, typhoid
Contact with animals e.g. brucellosis
Increased susceptibility due to immunodeficiency
What are some red flags suggesting serious illness in the febrile child?
Fever >38 if under 3 months, >39 if 3-6 months
Colour - pale, mottled, blue
Reduced LOC, neck stiffness, bulging fontanelle, status epileptics, focal neurological signs and symptoms
Significant respiratory distress
Bile-stained vomiting
Severe dehydration/shock
What does it mean if there is no focus for infection?
If no focus is identified, it may be because it is the prodromal phase of a viral illness, but may indicate serious bacterial infection, especially UTI or septicaemia
What is the main cause of a febrile child?
Upper respiratory tract infection (URTI), check for otitis media
How can you confirm meningitis?
Inflammatory cells in the CSF.
Are most meningitis infection bacterial or viral?
Viral, most are self-resolving. Bacterial is more serious (5-10% mortality).
What is the serious pathophysiology of meningitis?
Inflammatory mediators are released and leucocytes are activated, together with endothelial damage, this leads to cerebral oedema, raised ICP and decreased cerebral blood flow. The inflammatory response below the meninges causes a vasculopathy resulting in cerebral cortical infarction, and fibrin deposits may block the resorption of CSF by the arachnoid villi, resulting in hydrocephalus
What bacteria is most likely to cause meningitis in <3 month olds?
Group B strep
E.coli
Listeria monocytogenes
What bacteria is most likely to cause meningitis in 1 months -6 year olds?
Neisseria meningitidis
Strep pneumoniae
Haemophilus influenza
What bacteria is most likely to cause meningitis in > 6 years?
Neisseria meningitidis
Strep pneumoniae
What are some common differential diagnoses for the febrile child?
URTI Otitis media Tonsilitis Stridor Pneumonia Septicaemia Seizure Periorbital cellulitis Rash UTI Meningitis
What may you get in a history of meningitis/encephalitis?
Fever Headache Photophobia Lethargy Poor feeding/vomiting Irritability Hypotonia Drowsiness Loss of consciousness Seizures
What might you get during examination in meningitis/encephalitis?
Fever Purpuric rash Neck stiffness (not always in infants) Bulging fontanelle in infants Opisthotonus (back arching) Positive Brudzinski/Kernig signs Signs of shock Focal neurological signs Altered conscious level Papilloedema
What investigations would you do when thinking of a diagnosis of meningitis?
Bloods: FBC, glucose, blood gas, coagulation screen, CRP, culture of blood, throat, urine, stool
Rapid antigen test of meningitis organisms
LP for CSF unless contraindicated
What is Brudzinski sign?
Flexion of the neck with the child supine causes flexion of the knees and hips
What is Kernig sign?
With the child lying supine and with the hips and knees flexed, there is back pain on extension of the knee
What are some contraindications to lumbar puncture?
Cardiorespiratory instability
Focal neurological signs
Signs of raised ICP (coma, high BP, low heart rate)
Coagulopathy
Thrombocytopaenia
Local infection at the site of LP
If it causes undue delay in starting antibiotics
What is the first thing you do if you suspect meningitis?
There should be no delay in the administration of antibiotics and supportive therapy. A third-generation cephalosporin (cefotaxime or ceftriaxone) is the preferred choice.
What are the cerebral complications of meningitis?
Hearing loss Local vasculitis Subdural effusion Local cerebral infarction Haemophilus influenzae Hydrocephalus Cerebral abscess
How does meningitis cause hearing loss?
Inflammatory damage to the cochlear hair cells
How does meningitis cause hydrocephalus?
It may result from impaired resorption of CSF (communicating hydrocephalus) or blockage of the ventricular outlets by fibrin (non-communicating hydrocephalus)