Sepsis and The Innate Immune System Flashcards
Sepsis can be caused by the body’s reaction to meningitis, what type of rash would be spotted in this case?
Purpuric rash - non blanching.
What is sepsis?
Life threatening organ dysfunction due to a disregulated host response to infection.
What is septic shock?
Persisting hypotension requiring treatment to maintain blood pressure, despite fluid resuscitation.
What is bacteraemia?
Presence of bacteria in the blood (with or without clinical features).
Sepsis is recognised by the clinical assessment of patients who look sick or who have Early Warming Scores > 3 (from basic observation chart). Clinical features may suggest the source. What are some red flags and what should be done if Red Flag sepsis is spotted?
Red flags include a high respiratory rate, low blood pressure and unresponsiveness. Immediate action is required: send urgent investigations, inform a senior doctor for review and complete the Sepsis Six bundle.
What makes up the sepsis 6 bundle?
Give oxygen, fluids and IV antibiotics.
Take lactate, urine output and blood cultures (before antibiotics administered).
Give some examples of ‘urgent investigations’ in a case of Red Flag sepsis?
Full blood count (FBC), blood sugar, liver function test - CRP, coagulation studies and other microbiology samples (at site/source of infection).
Neisseria meningitidis - how does it spread, what does it do and give 3 features?
Spread by direct contact with respiratory secretions, mostly colonises harmlessly.
Pili - small hair-like processes for enhancing attachment.
Polysaccharide capsule - promotes adherence and prevents phagocytosis.
Liposaccharide Endotoxin - triggers inflammation.
Describe the inflammatory cascade.
Locally cytokines (TNFa and IL1) stimulate an inflammatory response to promote would repair and recruit RE system. Systemically cytokines are released into circulation and stimulate Growth Factor, macrophages and platelets. The goal is control of infection.
What occurs in the inflammatory cascade during sepsis?
The infection is not controlled. Cytokines lead the activation of humoral cascades and the RE system –> circulatory insult with blood supply to vital organs compromised.
What’s the link between sepsis and coagulation?
Cytokines initiate production of thrombin and this promotes coagulation. They also inhibit fibrinolysis, so the clotting cascade leads to microvascular thrombosis, which may cause organ ischaemia, dysfunction and failure.
Microvascular injury is the major cause of shock and multi organ failure.
What could happen if lesions coalesce?
Progressive necrosis, as blood supply is prioritised to the vital organs.
What are the supportive and specific treatments for sepsis?
Specific - antimicrobials - look for agent that’s likely to be active against pathogen, in age group and will reach the site - follow previously determined plan.
Supportive - physiological restoration with sepsis 6 - consider referral to ITU for regular monitoring and reassessment.
List some life threatening complications of sepsis.
Irreversible hypotension, respiratory failure, acute kidney injury, raised intracranial pressure, ischaemic necrosis of digits/hands and feet.
How might a diagnosis be confirmed in sepsis?
With a blood culture, PCR blood, lumbar puncture (if safe) - microscopy and culture of cerebrospinal fluid and PCR it (in a case with possible meningitis etc).
Neisseria meningitidis is a gram _____ diplococcus with numerous serogroups. It’s polysaccharide capsular agent prevents ______ and its outer membrane acts as an ______. Up to __% of adults are carriers of meningococcal disease. It is spread by aerosols and ________ secretion. Acquisition –> clearance, carriage or ______.
In the U.K., group __ is the most common with a fatality rate of __%. Prevention 1 is ________ and 2 is prophylaxis. It is a _______ disease, which means cases must be reported to public health.
Negative (coccus often found in pairs) Phagocytosis Endotoxin - kidney shaped bacterium 25 (commensalism in some people) Nasopharyngeal Invasion B 10 Vaccination Notifiable
The 6 most common signs of sepsis are what?
- Mottled/discoloured skin
- Severe breathlessness
- Feeling like you’re going to die
- Not passing urine for a day
- Extreme muscle pain/shivering
- Slurred speech/confusion
What are the factors determining the outcome of the host-pathogen relationship?
Pathogen infectivity, virulence with mechanism of infection am the host’s immune response.
What is the immune system and what are its roles?
Cells and organs that contribute to immune defences against infections and non-infectious conditions (self vs non-self).
Roles: pathogen recognition, containing/eliminating infection and regulating itself and remembering pathogens.
What makes an infectious disease?
When a pathogen succeeds in evading or overwhelming a host’s immune defences.
The immune system is split into innate and adaptive. Both halves work towards human survival. State some differences.
Innate/immediate protection takes seconds, lacks specificity and memory and has no change in intensity.
The adaptive/ long lasting protection on the other hand can take days, is specific, has immunologic memory and changes in its intensity.
What is the innate immune system’s first line of defence and what are the different types?
Physical, physiological, chemical and biological barriers; these are factors which prevent entry and limit growth of pathogens.
List some physical barriers involved in innate immunity.
Skin, mucous membranes of the mouth, respiratory tract, GI tract, urinary tract and bronchial cilia.
List some physiological barriers involved in the innate immune system.
Diarrhoea (after food poisoning), vomiting (fp, hep, meningitis) - not just in GI infections, sneezing (sinusitis) where the goal is to expel microbes, but the symptoms may be from non infectious conditions.
