Infection and Immunology Flashcards
Define cellulitis and erysipelas
- Cellulitis is an acute bacterial infection of the dermis and subcutaneous tissue.
- Erysipelas is a superficial form, affecting the dermis. It is well demaracated, and sepsis is less likely
List risk factors of cellulitis
- Trauma, leg ulceration, maceration or eczema (break in the skin)
- Insect bites
- Lymphoedema
- Leg oedema
- Venous insufficiency and history of venous surgery
- Obesity
- Pregnancy
- Chicken pox
- Conditions that predispose infection (eg. diabetes)
- Neuropathy
- Alcohol misuse
- Recurrent - elderly, previous cellulitis, chronic lymphoedema
List common causative agents of cellulitis
- Strep pyogenes
- Staph aureus
Describe prevalence of cellulitis
- 0.2 per 1000 person years to 24.6 per 1000 person years
- Recurrence common
List symptoms of cellulitis
- Acute onset of red, painful, hot, swollen skin
- Spreads rapidly
- Fever, malaise, nausea, shivering, rigors
List signs of cellulitis
- Tender skin
- Obvious break in the skin where an organism may have entered
- Diffuse redness, well demarcated edge
- Blisters and bullae
- Inflamed lymph nodes or lymphangitis (presence of red, linear streaks spreading proximally from the area of cellulitis, peau d’orange appearance)
- Ulceration
Describe classification of cellulitis
- Class I — there are no signs of systemic toxicity and the person has no uncontrolled comorbidities.
- Class II — the person is either systemically unwell or systemically well but with a comorbidity (for example peripheral arterial disease, chronic venous insufficiency, or morbid obesity) which may complicate or delay resolution of infection.
- Class III — the person has significant systemic upset, such as acute confusion, tachycardia, tachypnoea, hypotension, or unstable comorbidities that may interfere with a response to treatment, or a limb-threatening infection due to vascular compromize.
- Class IV — the person has sepsis or a severe life-threatening infection, such as necrotizing fasciitis.
Describe investigations performed in cellulitis
- Swab for culture
- Ultrasonography (abscess, drainable fluid collection)
- Skin biopsy
- WBC, ESR, CRP
- If orbital, CT/MRI
Describe management of cellulitis
- Draw around the lesion and monitor
- Antibiotics (oral amox if possible, review IV after 48 hours to switch to oral, if MRSA trimethoprim-sulfamethoxazole)
- Hospital admission if class IV or III, rapidly deteriorating, young, immunocompromised, facial, or significant lymphoedema
- Referral if severely unwell, infection near eyes or nose, uncommon pathogen, lymphangitis, cannot take oral antibiotics, not responding to oral antibiotics)
- Recurrent episodes refer
List complications of cellulitis
Acute
- Necrotizing fasciitis (rapidly progressive, extensive gangrene and necrosis of skin and underlying structures)
- Myositis
- Sepsis
- Subcutaneous abscesses
- Post streptococcal nephritis
Chronic complications
- Persistent leg ulceration
- Lymphoedema
- Recurrent cellulitis
Describe prognosis of cellulitis
- Most cases resolve with treatment
- After 12 months, 29.4% of patients had at least 1 recurrence
- Length of hospitalization increases with each subsequent recurrence
Define anaphylaxis
A severe, generalised or systemic hypersensitivity reaction, characterised by rapidly developing life-threatening airway and/or breathing and/or circulation problems usually associated with skin and mucosal changes
Describe epidemiology of anaphylaxis
- Risen by 70% in the last 5 years
- Most commonly food allergic reactions in young children
- Affects both sexes equally
- 1/3 is food related
- Medicines are common causes in adults
List risk factors of anaphylaxis
- Less than 30 at risk of food and exercise related
- Atopy/ asthma
- History of anaphylaxis
- Exposure to a common sensitiser (eg. latex)
- Adults at risk of food, insect venom and medicine related
- Female sex more at risk of food-associated and exercise associated
List symptoms of anaphylaxis
- Acute onset
- Angiooedema (airway swelling, tongue)
- SOB
- Respiratory arrest
- Confusion
- Hives
- Pruritis
- Nausea, vomiting, diarrhoea, incontinence
- Abdominal cramps and pain
- Agitation, anxiety, sense of impending doom
List signs of anaphylaxis
- Inspiratory stridor and hoarse voice
- Chest hyperinflation, accessory muscle use, wheeze
- Cyanosis
- Pale clammy skin
- Hypotension
- Tachycardia
- Respiratory arrest
- Bradycardia
- Urticaria
- Erythema
List investigations for anaphylaxis
- Mast cell tryptase (16 years or over during or soon after resusitation, one as soon as possible, one 1-2 hours after symptoms, one 24 hours. May be elevated)
- Plasma histamine
- ECG (non-specific ST changes)
- Urea and electrolytes (normal)
- ABG (elevated lactate)
- CXR (hyperinflation, interstitial fluid)
- Allergy testing follow up
Describe management of anaphylaxis
- CPR and ALS if arrested
- ABCDE
- IM adrenaline 0.5ml 1:1000
- Airway + high flow oxygen, legs in the air
- IV fluids, chlorphenamine and hydrocortisone
- Cardioresp assess
- Consider nebulised adrenaline, SABA, atropine, glucagon
After initial treatment
- Antihistamine (chlorphenamine)
- Corticosteroid (hydrocortisone sodium succinate)
- Monitor for biphasic reaction
- Review by senior clinician and observation
- Give patient adrenaline auto-injector (eg. Epipen)
List complications of anaphylaxis
- MI
- Recurrence
Describe prognosis of anaphylaxis
- Severity of previous reaction does not predict severity of subsequent events, treatment does
- Serious sequelae of inadequate brain perfusion may occur, prognosis of MI depends on comorbidities and patient age
Which skin condition is aspirin linked to?
Urticaria
What specific inflammatory marker is raised in sepsis?
TNFa
Compare sepsis, septic shock and SIRS
- SIRS consists of changes in clinical signs including an abnormal body temperature, increased heart rate, increased respiratory rate, an abnormal white cell count (either decreased or elevated), or an increase in band neutrophils due to a severe inflammatory response resulting in organ dysfunction
- Sepsis is SIRS with an infectious cause. Life threatening organ dysfunction caused by dysregulated host response to infection
- Septic shock is lactate over 2mmol/l despite good fluid resucitation, or patient requiring vasopressers to maintain MAP over 65
- Septicaemia is an infection in the bloodstream
Define SLE
A chronic multi-system disorder that most commonly affects women during their reproductive years. It is characterised by the presence of antinuclear antibodies