Heart Flashcards
(66 cards)
When does one use anti microbial prophylaxis?
In situations where infection is common and predictable
In situations where the effect of infection would be very detrimental
What are the 4 chambers of the foetal heart called?
Sinus venosus
Atrium
Ventricle
Bulbus cordis
What is an anti microbial prophylaxis
An agent that has activity against most of the expected organisms
What factors determine the efficacy of antimicrobial prophylaxis
The antibiotic sensitivity of the likely pathogens
Adequate levels of the medication needs to be given at the time of risk
What are the disadvantages of antimicrobial prophylaxis?
Cost
Adverse effects
Antibiotic resistance
Insufficient attention to other preventative measures
When is prophylaxis used in HIV?
- Post-exposure antiretrovirals - mother to child, rape survivors, occupational exposure
- With advanced AIDS - prevent initial/recurrent infections (cotrimoxazole to prevent PCP, flu console to prevent cryptococcal infection)
What is the preferred antibiotic for surgical prophylaxis?
Cefazolin (1st generation cephalosporin mainly active against staph)
If operating on the GIT, what antibiotic would you prescribe and why?
- co-amoxiclav
- cefazolin and metronidazole
They cover S. aureus and other organisms found in the colon (anaerobes and gram-neg bacilli)
When must prophylaxis be given for surgery?
At the time of the anesthesia to ensure food levels are present at the time of risk of infection
Why is antimicrobial prophylaxis necessary in patients with rheumatic fever and not with glomerulonephritis?
There are multiple rheumatogenic strains of strep pyogenes and only a few nephrotogenic strains
What is the aim of antimicrobial prophylaxis in rheumatic fever patients?
To prevent repeat infections with strep pyogenes
What are the recommended antibiotics prescribed as prophylaxis for rheumatic fever?
- benzathine penicillin (IM monthly)
- penicillin (12 hourly)
- erythromycin (12hourly)
How long should a rheumatic fever patient be on antimicrobial prophylaxis?
- without proven carditis : 5 years after last attack/ until 18
- with mild carditis : 10 years after last attack/ until 25
- with severe valvular disease : lifelong
Why does penicillin still work as an effective prophylaxis for rheumatic fever?
- s. pyogenes has never developed resistance to it
- it has relatively little effect on other commensal bacteria
What is endocarditis?
An infection of the endocardium of the heart or valves, usually relating to turbulence or abnormal flow of blood resulting in damage to endocardium and development of vegetations (infected clumps of platelets and protein)
What commonly causes endocarditis?
Viridans streptococci (low virulence organism present as normal flora in mouth and upper airway)
According to new research, who should be given prophylaxis for infective endocarditis?
- had previous endocarditis
- had valve replacements
- have surgically constructed shunts
What is autoimmunity?
An influx of auto reactive immune cells and/or antibodies in body tissues that initiate inflammation and represent failure of tolerance induction
What can cause a loss of self-tolerance?
- a loss immunological privileged status (infection)
- viral/drug induced altered self-antigens (haemolytic anaemic)
- regulatory T-cell dysfunction
- molecular mimicry (shared common antigens)
Describe the pathogenesis of rheumatic fever
- pharyngeal infection by group A strep 2-6 weeks before clinical manifestation
- antibodies made against group A strep cross-react with human tissue
- molecular mimicry (heart valve and brain share common antigenic sequences with GAS bacteria)
- host immune responses may play a role in determining who gets ARF following infection
What is the relationship between hypersensitivity reactions and ARF?
Type 2 - carditis
Type 3 - synovitis/ arthritis and s. chorea
Type 4 - subcutaneous nodules and carditis
What are Aschoff nodules?
A form of granulomatous inflammation found in the myocardium around the vessels
What are the major criteria for diagnosing acute rheumatic fever?
- carditis
- erythema marginatum
- Sydenham’s chorea
- subcutaneous nodules
- arthritis
What are the minor criteria for diagnosing acute rheumatic fever?
- fever
- high ESR
- increased CRP
- long PR interval