Antimicrobials Flashcards
goals/general rules of antimicrobials
- inhibit microorganisms at concentrations that are tolerated by the host
- seriously ill/immunocompromised select bactericidal
- narrow spectrum before broad spectrum (or a combination therapy to preserve normal flora)
roles of antimicrobials in anesthesia practice
- prophylaxis before surgery (at least 1 hour before incision)
- potential for adverse reactions (hypersensitivity, direct organ toxicity, super-infections, ID patients at risk for complications)
- cross-reactions with other meds we give
SSI
surgical site infections; infection related to an operative procedure that occurs at or near the surgical incision within 30 days of the procedure
SSI facts
- second most common healthcare associated infection
- develop in 2-5% of 30 million surgical patients
- represent 14-16% of all hospital acquired infections annually in the US
- cost 1 billion dollars/year
- account for 3% of surgical mortality
SSIs lead to
- increased re-admissions
- increased LOS in hospital (7-10 days)
- increased hospital costs (additional $3000-29,000 per SSI diagnosis
Signs indicative of SSI
- purulent drainage from surgical site
- positive culture obtained from surgical site that was closed initially
- surgeon diagnoses infection
- surgical site that requires reopening due to at least one of the following s/s –> tenderness, swelling, redness or heat
surgical risk for SSI
- procedure type
- skill of surgeon (longer it takes, the greater the chance for infection)
- use of foreign material or implantable device
- degree of tissue trauma
patient risks for SSI
- diabetes
- smoking
- obesity
- malnutrition (not enough protein to support healing)
- systemic steroid use
- immunosuppressive therapy
- intra op hypothermia (slows BMR, constricts blood vessels, and makes blood more viscous –> shift of oxy hgb curve to left)
- trauma
- prosthetic heart valves
SSI prevention
- timely and appropriate use of antibiotics
- maintenance of normothermia
- proper syringe/med administration practices
SCIP
Surgical Care Improvement Project
Antibiotic timing
- abx prophylaxis 1 hour before incision had the lowest rate of SSI
- 30-60 min before incision is ideal window for drug admin
normothermia
hypothermia associated with adverse outcomes like…
- increased blood loss
- increased transfusion requirements
- prolonged PACU stay
- post-op pain
- impaired immune function
- compromised neutrophil function –> vasoconstriction –> tissue hypoxia + increased incidence of SSI
bactericidal
if they kill the susceptible bacteria
- more common
- what we use in the OR
bacteriostatic
if they reversibly inhibit the growth of bacteria; for this type of abx, the duration of therapy must be sufficient to allow cellular and humoral defense mechanisms to eradicate the bacteria
list of bactericidal abx
- penicillins
- cephalosporins
- isoniazid
- metronidazole
- polymyxins
- rifampin
- vancomycin
- aminoglycosides
- bacitracin
- quinolones
list of bacteriostatic abx
- chloramphenicol
- clindamycin
- macrolides
- sulfonamides
- tetracyclines
- trimethoprim
Penicillin Structure
dicyclic nucleus that consists of a thiazolidine ring connected to a b-lactam ring
penicillin MOA
bactericidal; interferes with the synthesis of peptidoglycan which is an essential component to cell walls of susceptible bacteria
peptidoglycan
glycolic membrane of bacterial cell wall
penicillin effective against
- pneumococcal
- meningococcal
- streptococcal
- actinomycosis
penicillin excretion
- renal excretion
- rapid plasma concentration decreases 50% in 1st hour
- 10% glomerular filtration
- 90% renal tubular secretion
- anuria increases elimination half time by 10 fold
penicillin DOA
-administration of probenecid (med used for gout) will reduce renal excretion and prolong action
penicillin adverse reactions
- hypersensitivity (most allergenic of antimicrobials; up to 10% of population allergic)
- rash and/or fever
- hemolytic anemia
- maculopapular rash (delayed)
- immediate sensitivity - anaphylaxis
- cross-sensitivity common with all penicillin drugs and cephalosporins (3%) due to common beta-lactam ring
penicillin uses
- otitis media
- peritonitis
- meningitis
- sore throat
- pneumonia & respiratory infections
- septicemia
- gonorrhea UTIs
penicillin routes
- oral
- IV
penicillin known issues
- resistance (beta-lactamase, and other mechanisms)
- allergic rxns
- cross-hypersensitivity (1-3% with cephalosporins)
second generation penicillin
- amoxicillin
- ampicillin
- have a wider range of activity than first generation penicillins
- gram negative bacilli –> haemophilus influenza
- e coli
type of cephalosporin
cefazolin
cephalosporin facts
- MOA - bactericidal antimicrobial that inhibits bacterial cell wall synthesis and have low toxicity
- broad spectrum
- SE - low incidence of allergic rxns
- cross reactivity with other cephalosporins
- penicillin and cephalosporin allergy 3-5%
- renal excretion
1st generation cephalosporin
cephazolin coverage: -gram negative + -strep pneumoniae +++ -gram positives +++
2nd generation cephalosporin
cefuroxime coverage: -gram negative ++ -strep pneumoniae ++ -gram positives ++
3rd generation cephalosporin
cefetaxime coverage: -gram negative +++ -strep pneumoniae +++ -gram positives +
4th generation cephalosporin
cefepime coverage: -gram negative +++ -strep pneumoniae +++ -gram positives ++
which cephalosporins achieve therapeutic levels in CSF
- 3rd generation
- makes it a good option for meningitis
- lower toxicity than earlier generations
macrolides structure
compounds characterized by a macrolytic lactone ring containing 14-16 atoms with a deoxy sugar attached
type of macrolide
- erythromycin
- azithromycin
macrolides effective against
- gram positive bacilli
- pneumococci
- streptococci
- staphylococci
- mycoplasma
- chlamydia
macrolide routes
- oral
- IV
macrolide uses
- Upper respiratory tract (pharyngitis, tonsillitis, sore throat)
- otitis media
- lower respiratory tract infections (pneumonia, MAC, Legionnaire’s, anthrax)
- ulcers (h. pylori)
- uncomplicated skin infections (staph)
- STDs (chancroid disease in men, chlamydia, gonorrhea)
macrolide MOA
- bacteriostatic
- binds to 50S and blocks translocation step in protein synthesis
macrolide pharmacokinetics
- azithro half life = 3 days
- a 1 gram dose provides 7 day coverage
- common therapy consists of 500 mg loading dose and 250 mg/day for 4 more days