Antimicrobials Etc. Flashcards
In the cardiothoracic sx population, _______ is a/w an approxiamte 50% decrease in deep sternal infection
Glucose control
BS should be kept below _____ for 48 hrs post-op to decrease SSIs
200 mg/dL
How long should smoking be stopped prior to sx?
4-8 wks
What 3 factors of hypothermia favor infection?
- Peripheral vasoconstriciton
- Decreased wound oxygen tension
- Decreased recruitment of leukocytes
Immunosuppression from _____ use of corticosteroids has been considered a risk factor for SSIs
Long-term
Which SCIP suggested prophylactic abx be recieved within 1 hr prior to surgical incision?
SCIP 1
Which SCIP recommended prophylactic abx selection for surgical pt should be appropriate for most likely organsim r/t procedure & appropriate to pt characteristics?
SCIP 2
When does the risk of using routine abx prophylaxis outweight the benefits?
Clean elective surgical procedures (mastectomy or thyroidectomy) where no tissue (other than skin) carrrying indogenous flora is bein penetrated
What are the predominant organisms causing SSIs after clean procedures?
Skin flora (Staph aureus & stap epidermidis)
In clean-contaminated procedures, such as abdominal procedures & solid organ transplant, the most common organisms include:
Gram-negative rods
Enterococci
Staph aureus
Staph epidermidis
IgE-mediated anaphylactic reactions to antimicrobials occur ____ after dosing and include what s/s?
30-60 min; urticaria (hives), bronchospasm, & hemodynamic collapse
________ is not recommended for routine prophylaxis for any population without documented or highly suspected colonization of infection with MRSA (nursing home or hemodialysis) or known IgE response to beta-lactam abx
Vancomycin
Wide therapeutic index w/ low incidence of side effects.
Abx of choic for sx procedures where normal flora, skin flora, GI and GU tracts are the most likely pathogens
Cephalosporins
Can be used in pts who are allerigic to PCN unless it was an IgE-mediated rxn
Cephalosporins
Clean-contaminated procedure require additional coverage for ____ & ____ in additon to _____. What can be added?
Gram-negative rods, anaerobes, skin flora; Metronidazole
Is Vancomycin a good choice for bowel surgeries? Why or why not
No, it would affect gram-positive flora which play an important role in resistance to colonization
________ of the antimicrobial depends on drug delivery to site of infection
Efficacy
What 3 sites do nearly 80% of nosocomial infections occur in?
Urinary tract, respiratory tract, blood stream
Organism infecting access catheters most commonly comes from the colonized ___ or ____ and reflect skin flora (___ & __)
HUB, LUMEN; S aureus & S epidermidis
What is the usual initial therapy of suspected intravascular catheter infection? Why?
Vanc; high incidence of MRSA & MRSE in nosocomial environment
How do antimicrobials affect parturients?
Most cross the placenta & enter maternal milk;
Delayed gastric emptying may decrease absorption of PO antimicrobials
How do antimicrobials affect the fetus?
Immature fetal liver may lack enzymes to metabolize drugs;
Teratogenicity;
Why would plasma antimicrobial concenctrations be decreased in a parturient (10-50%)?
Increased maternal blood volume —> increased GFR
& hepatic metabolic activity
Elderly effects on antimicrobials:
⬇️ gastric acidity & GI motility can alter PO absorption;
Distribution (⬆️ total body fat/⬇️ plasma albumin);
Excretion (⬇️ GFR)
_____ & _____ do not need significant changes in dosage schedule as long as serum creatinine concentrations are normal in the elderly. But _____ & ______ may require dose adjustments
PCN, Cephalosporins; Aminoglycosides & Vancomycin
PCN may be classified into subgroups d/t:
Structure, B-lactamase susceptibility, & spectrum of activivty
How does PCN work on bacteria?
- It has ability to interfere w/ synthesis of peptidoglycan which is an essential component of bacteria cell walls. (Bactericidal)
- Decreases availability of an inhibitor of murein hydrolase so the uninhibited enzyme can destroy (lyse) the structural integrity of the cell wall
PCN is drug of choice for:
Pneumococcal, Streptococcal, Meningococcal, & all forms of actinomycosis & clostridial infxns causing gas gangrene
Gradually _____ of PCN is needed to tx _____ d/t resistance
Higher dose, gonococci
Pts with cardiac issues & tissue implants need prophylactic treatment with what d/t transient bacteremia that occurs from dental extractions?
PCN
PCN G IV 10 million units contains _____ mEq of K. Pts with ______ may result in neurotoxicity & hyperkalemia
16; renal dysfunction
Excretion of PCN is ______:
Rapid;
60-90% in first hr —> plasma conc ⬇️ 50% of peak;
10% E by GFR/ 90% by renal tubular secretion
_____ increases elimination half time of PCN G 10-fold
Anuria
Used to prolong PCN by blocking its renal tubular secretion
Probenecid
Major mechanism of resistance to PCNs
Bacteria produce B-lactamase enzymes that hydrolyze the B-lactam ring, rendering it inactive
Which drugs are not susceptible to hydrolysis by staph penicillinases that would normally hydrolyze b-lactam ring
“CON MD” Cloxacillin, oxacillin, nafcillin, methicillin, dicloxacillin
_______ can penetrate the CNS sufficient enough to treat staph meningitis
Nafcillin
High dose _____ therapy has been a/w hepatitis
Oxacillin
There is extensive renal excretion for which penicillinase-resistant PCNs? What would be a better option fot pt with impaired renal fxn?
Methicillin, oxacillin, & cloxacillin;
Nafcillin (80% bile)
2nd generation PCNs are bactericidal against? (Ampicillin & amoxicillin) They are not effective against what?
BOTH gram + and gram - bacteria; staphylococcal infxns
Are 2nd generation PCNs susceptible to penicillinase produced by bacteria?
Yes, ALL inactivated by penicillinase & not effective against most staph infections
When does skin rash typically appear after PCN?
7-10 days after initiation; may not be true allergic rxn but a/w protein impurities
How does amoxicillin compare to ampicillin?
Chemically identical, spectrum of activity identical, but more efficiently absorbed by GI & stays in circulation 2x as long
3rd generation PCN
Derivative of ampicillin
Principal advantage is effectiveness in tx of ifxns caused by pseudomonas aeruginosa & proteus strains resistant to ampicillin.
Parenterally (not absorbed GI)
Carbenicillin
Greater than ____ % of carbenicillin is Na, so ____ may develop in suceptible pts
10; CHF
Interferes with normal platelet aggregation and prolongs bleeding time even when platelet count remains the same
Carbenicillin
Derivative of ampicillin, broadest spectrum of all PCNs
Ineffective against penicillinase
4th generation - Acylaminopenicillins
Have very little antimicrobial activity, but bind irreversibly to beta-lactamase enzyme inactivating it & rendering organism sensitive to beta-lactamase-susceptible PCN
PCN beta-lactamase inhibitors:
Clavulanic acid + PO amoxicillin
Sulbactam + IV ampicillin
Like PCN, ______ are bactericidal antimicrobials that inhibit cell wall synthesis & have a low intrinsic toxicity
Cephalosporins
What causes resistance to cephalosporins?
- Cephalosporinases (beta-lactamases)
2. Inability to penetrate the bacteria to its site of action
Large doses of cephalosporins cause what?
Positive Coomb’s reaction (hemolysis is rare)
With the exception of _______, _______ have less frequency of _______ than aminoglycosides or polymyxins
Cephaloridine; Cephalosporins; nephrotoxicity
Can a pt with PCN allergy use cephalosporins? Why or why not?
Some may be used as alternative bc cross-reactivity is infrequent
What is penicilloyl? What percent of pts allergic to PCN have this?
A hapten metabolite formed from the ring structure of PCN that acts as an antigen. Cannot induce formation of antibodies but may cause immune response when bound to protein. 95%
Which penicillinase-resistant PCN would be the best choice for high dose therapy in a pt with renal impairment?
Nafcillin (80% E in bile)
Treats gram negative & some gram positive bacteria. Used in urinary & genital infections
Cipro (fluoroquinolone)
Treats staph, strep, & gram positive bacteria.
Used as prophylaxis in pts w/ no B lactam allergy.
Cefazolin (cephalosporin)
Treats gram negative bacteria. Abx of choice for sx procedure where normal flora, skin flora, GI & GU tracts are the most likely pathogen
Ceftriaxone (cephalosporin)
Treats strep & staph. Used in pts with beta lactam allergy
Clindamycin (macrolide)
Mostly gram negative bacteria. Penetrates pleural, ascitic, & synovial fluids in the presence of inflammation
Gentamicin (aminoglycoside)
Used for pts who have beta lactam allergy. Used in IV catheter infection and in gram positive bacteria
Vancomycin (Macrolide)
Can be taken by pts who are allergic to penicillin. Treats anaerobic bacteria, gram negative rods, & skin flora. Used in CNS, bone, joint, GI, & GU infections. Can be added for colorectal & abdominal surgeries
Metronidazole
Broad spectrum against gram positive and negative bacteria and atypical respiratory pathogens. Treats infections inside the body. Used in UTI’s and prostatitis
Levofloxacin (fluoroquinolone)
Causes pseudomembranous colitis. __ treats it.
Clindamycin; vanc
Causes torsades de pointes
Erythromycin (oral)
Topical tx for skin infections
Neomycin (aminoglycoside)
