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Anesthesia Pharm > Week 11 - Antibiotics for Surgical Procedures > Flashcards

Week 11 - Antibiotics for Surgical Procedures Flashcards

1
Q

Where do 80% of nosocomial infections occur?

A

Urinary tract – foley catheters

Respiratory system – ventilators and VAP

Bloodstream – IV catheters

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2
Q

What are the patient related risk factors for surgical site infections?

A
  • Age extremes <5 or >65
  • Poor nutritional status
  • Diabetes mellitus AND periop glycemic control (<200)
  • Peripheral vascular disease
  • Tobacco use (quit 4-8 weeks preop reduces SSI 50%)
  • Coexisting infections
  • Altered immune response
  • Corticosteroid therapy
  • Preoperative skin preparation (scrub and shave)
  • Preoperative length of stay (longer preop stay greater risk of infection)
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3
Q

What are the facility related risk factors for surgical site infections?

A
  • Experience of surgeon (volume-outcome relationship)
  • Technique (Open vs laparoscopic procedure)
  • Length of surgery
  • Type and method of sterilization of instruments
  • Perioperative normothermia
  • Appropriate antibiotic dosing and re-dosing as needed
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4
Q

What is the ideal antimicrobial agent?

A

Acts on the pathogen and not the host

Does this via:

  • Unique cellular structures and biochemical pathways
  • Common pathways but altered affinities for certain components
  • Prodrugs that are converted by only the pathogen
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5
Q

What does mismanagement of prophylactic antibiotics lead to?

A
  • Increased risk of surgical site infection and hospital acquired infections
  • Increased surgical morbidity and mortality
  • Increased cost
  • Associated with the rise in resistant infections nationwide

*inappropriate use continues to be a major problem for surgical patients

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6
Q

What are the risk factors for microbial resistance?

A

Antibiotics (2nd largest class of prescribed medications)

Extended/inappropriate use of antibiotics

Transmission of infection

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7
Q

What are the different antimicrobial spectrums of activity?

A

Narrow Spectrum: effective against Gm+ OR Gm- microbes

  • works well for specific organisms and most surgical prophylaxis
  • lowers risk of developing superinfections

Extended Spectrum: affects Gm+ AND Gm- bacteria

Broad Spectrum: affects Gm+ AND Gm- bacteria AND other microorganisms

  • greater risk of superinfections
  • don’t typically give in OR
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8
Q

What are the common narrow spectrum antimicrobial agents?

A 
Clindamycin*
Vancomycin*
Bacitracin
Macrolides
Metronidazole
PCN G
PCN V
Polymyxins
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9
Q

What are the common extended spectrum antimicrobial agents?

A 
Cephalosporins*
Aminoglycosides
Extended PCNs
Fluoroquinolones
Imipenem
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10
Q

What are the common broad spectrum antimicrobial agents?

A

Chloramphenicol
Sulfonamides
Tetracyclines
Trimethoprim

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11
Q

Bactericidal vs Bacteriostatic

A

Bactericidal = agents KILL the microbes (killing infection that occurs requires bactericidal)
*MBC - minimal bactericidal concentration

Bacteriostatic = agents INHIBIT GROWTH of microbes (surgical prophylaxis requires bacteriostatic)
*MIC - minimal inhibitory concentration – surgical dosing

  • Type of microbe is important
  • Chosen antimicrobial’s spectrum of activity is important
  • Antimicrobial level in the blood should exceed the MIC by 2-8x to provide prophylaxis against infection
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12
Q

What common antimicrobial agents are bactericidal?

A 
Aminoglycosides
Bacitracin*
Daptomycin
Fluoroquinolones
Imipenem*
Isoniazid
Metronidazole
Penicillins*
Cephalosporins*
Polymyxins
Rifampin
Vancomycin*
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13
Q

What common antimicrobial agents are bacteriostatic?

A 
Clindamycin*
Erythromycin
Nitrofurantoin
Sulfonamides
Tetracyclines
Trimethoprim
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14
Q

When is Chlorhexidine skin prep bactericidal and when is it bateriostatic?

A

Bacteriostatic = low concentrations

Bactericidal = high concentrations

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15
Q

What percent of iodine based skin prep is bactericidal?

A

Broad spectrum bactericidal at 1%

*higher concentrations cause necrosis

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16
Q

What are the common antibiotics mechanism of actions?

A

Cell Wall Synthesis:

  • Beta Lactams (popular surgical prophylaxis): PCN, Cephalosporins, Carbapenems, Monobactams
  • Vancomycin, Bacitracin
  • Cell Membrane: Polymyxins

Nucleic Acid Synthesis:

  • Folate synthesis (sulfonamides, trimethoprim)
  • DNA Gyrase (quinolones)
  • RNA Polymerase (rifampin)

Protein Synthesis:

  • 30S Subunit (tetracyclines, aminoglycosides)
  • 50S Subunit (macrolides, clindamycin, linezolid, chloramphenicol, streptogramins)
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17
Q

What are beta-lactam antibiotics?

A

Broad spectrum antibiotics that contain a beta-lactam ring in the structure

–Penicillins – Cephalosporins – Monobactams – Carbapenems –

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18
Q

What are the different Penicillins?

A

Derived from Penicillium fungi

PCN-G = IV form — PCN-G = PCN-G-K (K is for potassium – beware high doses)

PCN-V = PO form

  • there is an IM form
  • allergic to one PCN – allergic to all PCN
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19
Q

When are Penicillins the drug of choice?

A
  • Pneumococcal infections
  • Streptococcal infections
  • Meningococcal infections
  • Highly effective treatment for syphilis
  • Actinomycosis and clostridial infections that result in gas gangrene
  • Prophylactic for patients with history of rheumatic fever and surgery or dental work to treat transient bacteremia
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20
Q

How are PCNs excreted?

A

Renal excretion = Rapid (60-90% of an IM dose is excreted within 1 hour) – plasma concentration decreases to 50% its peak within 1 hour

10% GFR
90% renal tubular secretion

  • if renal failure, need to adjust dose
  • anuria increases elimination T1/2 of PCN-G by 10x
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21
Q

What are Cephalosporins (Gen 1-3) active against?

A

First generation = mostly active against Gram+ bacteria

Successive generations = more active against Gram-

*increasing affinity for Gm- resulted in decreased affinity for Gm+

22
Q

What are Cephalosporins mechanism of action?

A

Bactericidal via interruption of cell wall synthesis
-more resistant to Beta-Lactamases

Disrupt B-Lactam ring and inhibit activity

~5-10% (rare) may have cross-reactivity with PCNs and/or Carbapenems (lack of suitable alternatives has forced use of Cephalosporins in these pts)

  • allergic reactions in 1-10% of patients
  • cross reactivity between Cephalosporins (all-for-one)
23
Q

What is PCN resistance due to?

A

Bacterial production of Beta-lactamase enzymes that hydrolyze the Beta-lactam ring, rendering the antimicrobial inactive

*Methicillin, Oxacillin, Nafcillin, Cloxacillin, and Dicloxacillin are not hydrolysis susceptible to hydrolysis and will frequently work against these organisms – these drugs are used in infections caused by staphylococci

24
Q

What is resistance to Cephalosporins due to?

A

Inability to penetrate the site of action

25
Q

What is an example of a first generation cephalosporin? How is it administered? How is it excreted?

A

Cefazolin

Poor PO – reasonable IM absorption and well tolerated – IV is best

1st Gen excreted largely unaltered by the kidneys
-decrease dose in renal failure

26
Q

What is an example of a second generation cephalosporin?

A

Cefoxitin and Cefuroxime

  • Extended activity against Gm- bacteria
  • Shorter T1/2
  • Excreted unchanged by the kidney

*Cefuroxime is only 2nd gen good for treating meningitis

27
Q

What is an example of a third generation cephalosporin?

A

Cefotaxime

  • resist beta-lactam hydrolysis
  • achieves CSF levels and good for meningitis
  • Elimination T1/2 one hour requiring more frequent redosing
28
Q

What are Monobactams (Axtreonam) effective against?

A

Effective ONLY against Gram- bacteria (Neisseria, Pseudomonas)

Resistant to some beta-lactamases

*not absorbed PO – must be given IM or IV

29
Q

What are Carbapenems useful for?

A

Imipenem, Meropenem, Ertapenem, Doripenem

Useful for multi-drug resistant infections (hospitalized pts)

  • Broader spectrum than other beta-lactams
  • Less affected by mechanisms of antibiotic resistance
30
Q

What can Clindamycin cause?

A

Pseudomembranous Colitis

  • reserved for severe infections not controlled by other less toxic antibiotics
  • d/c if significant diarrhea
31
Q

What effect can high doses of Clindamycin have at the NMJ?

A

Produces pre- and post-junctional effects at NMJ
*these effects cannot be readily antagonized with calcium or AChE drugs

High doses can result in profound and long-lasting neuromuscular blockade in the absence of nondepolarizing muscle relaxants

32
Q

What is vancomycin?

A

Bactericidal glycopeptide that impairs cell wall synthesis of Gram+ bacteria

  • works well PO for enterocolitis because it’s poorly absorbed from the GI tract
  • Drug of choice for MRSA infections

IV 10-15mg/kg – MUST be given slowly over 60 minutes
*sustained plasma concentration for 12 hours - rarely re-dose in OR

33
Q

What does a fast administration of vancomycin result in?

A

A large histamine release

  • Red Man’s syndrome
  • Severe hypotension
  • Cardiac arrest?
34
Q

What are Fluoroquinolones good for?

A

Ciprofloxacin is highly effective for urinary and genital tract infections (prostatitis and GI infections)

Upper and lower respiratory infections

Soft tissue, bone, and joint infections

*high blood levels and good tissue penetration make it a good antibiotic

35
Q

What is the mechanism of action of chlorhexidine?

A

Disrupts cell membranes of bacteria

Effective against G- and G+

  • persists on skin to provide continuous coverage
  • 2% is more effective than povidine-iodine as hand scrub
36
Q

How quickly does iodine act?

A

Rapid acting antiseptic that, IN THE ABSENCE of, organic material kills bacteria, viruses, and spores

1% iodine kills 90% bacteria in 90 seconds
5% iodine kills 90% bacteria in 60 seconds
>7% iodine may cause cutaneous burns

***MUST DRY to be effective

37
Q

What do you need to be aware of/check for with surgical antibiotic prophylaxis?

A
  • Ensure surgical antimicrobial orders reflect published evidence
  • Achieve plasma concentration prior to incision
  • Infusion must be completed prior to tourniquet inflation
  • Maintain intra-op MIC plasma concentration until skin closure***
  • Interval dosing based on the particular antibiotic administered
  • Additional dose anytime EBL exceeds 1500 mL since last dose
38
Q

What is the most commonly used antibiotic for surgical prophylaxis?

A

Cefazolin (1st gen cephalosporin)

*wide therapeutic index and low incidence of side effects, cost effective

39
Q

What antibiotics are typical backups for B-lactam allergy?

A

Clindamycin

Vancomycin

Gentamicin

40
Q

What are antibiotic re-dosing intervals based on?

A

2-2.5 times the T1/2 in the general population with normal renal function

*doses are based on ideal body weight

41
Q

What perioperative antibiotics need to be re-dosed every 2 hours?

A

Ampicillin-sulbactam

Ampicillin

Cefoxitin

Piperacillin-tazobactam

42
Q

What perioperative antibiotics need to be re-dosed every 3 hours?

A

Cefotaxime

43
Q

What perioperative antibiotics need to be re-dosed every 4 hours?

A

Aztreonam

Cefazolin

Cefuroxime

44
Q

What perioperative antibiotics need to be re-dosed every 6 hours?

A

Cefotetan

Clindamycin

45
Q

What are the four main factors for surgical site infections?

A
  • Host Fitness (ability to the host to defend)
  • Inoculum (amount of pathogen transmitted)
  • Wound Microenvironment (conditions at the wound site) – necrotic tissue, stitches, the inoculum itself
  • Pathogen Virulence (ability of the pathogen to cause disease)
46
Q

What is the most common causes of bacteremia or fungemia in hospitalized patients?

A

IV access catheters

*S. aureus and S. epidermidis

47
Q

What is the mechanism of action of Penicillins?

A

Bactericidal – Cell Wall Synthesis Inhibitors

  • Interfere with the synthesis of peptidoglycan – essential component of cell walls of susceptible bacteria
  • Decrease the availability of an inhibitor of murein hydrolase such that the uninhibited enzyme can then destroy (lyse) the structural integrity of bacterial cell walls
  • resistant Gm- bacteria prevent access to sites where synthesis of peptidoglycan is taking place
48
Q

What are the broad-spectrum penicillins?

A

2nd Gen PCNs: Ampicillin, Amoxicillin (broad spectrum)
3rd Gen PCNs: Carbenicillin (extended spectrum)
4th Gen PCNs: Mezlocillin, Piperacillin, Azlocillin (extended - broadest spectrum)

  • wider range of activity than other PCNs – bactericidal against Gm- and Gm+ bacteria
  • inactivated by penicillinase produced by certain bacteria – not effective against most staphylococcal infections
49
Q

What are Clavulanic acid, Sulbactam, and Tazobactam?

A

Beta-lactam compounds that bind irreversibly to the Beta-lactamase enzymes

*inactivate Beta-lactamase enzymes causing the bacteria to be sensitive to PCNs

50
Q

What are Erythromycin or Clindamycin an effective alternative for?

A

Treatment of streptococcal pharyngitis, bronchitis, and pneumonia in patients who can’t tolerate PCNs or Cephalosporins

*Erythromycin prolongs QT – torsades de pointes

51
Q

What are Bacitracins?

A

a group of polypeptide antibiotics effective against a variety of Gm+ bacteria

  • use limited to topical application
  • treat furunculosis, carbuncle, impetigo, suppurative conjunctivitis, and infected corneal ulcer

Anesthesia Pharm (18 decks)

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