Anti-Microbials Flashcards
What is the general goal of antimicrobial therapy in anesthesia?
Inhibit microorganisms at concentrations that are tolerated by the host.
Name two general rules of antimicrobial therapy in anesthesia.
- For seriously ill/immunocompromised patients select bactericidal.
- Narrow spectrum before broad spectrum or combination therapy to preserve normal flora.
When we kill a patients normal flora we introduce them to what? Why?
Super infections because the normal flora can secrete “things” that kill opportunistic bacteria.
Name 5 considerations for antimicrobials used for surgical prophylaxis.
- Weigh the risks/benefits.
- select cost effective broad spectrum antibiotics
- Prophylactic antibiotics should be given no more than 1 hour before incision.
- Usually a single dose but may be continued for 48 hours.
- No proof that a brief course of antibiotics results in emergence of resistant organisms.
How do we select an antimicrobial? (6)
- Identify the causative organism.
- Efficacy depends on drug delivery to site.
- Usually treat with a single drug
- Route of administration
- Duration of treatment
- Cost
Name two considerations that may interfere with the efficacy of a drug to a particular site.
- transport across the BBB varies greatly
2. More effective if infected material is removed..
Are hypersensitivity reactions dependent or independent of the dose?
Independent
Are drug toxicities dependent or independent of the dose.
Dependent (dose related)
What special considerations must be made with a parturient when determining the proper antimicrobial? (2).
- Most antimicrobials cross the placenta and enter into maternal milk. Fetus’s liver is immature and they can’t metabolize or excrete that drug and could end up with toxicity. For milk mom should discard the first couple rounds.
- Teratogenecity- the malformation of an embryo or fetus that we worry about with any drug.
What special considerations must be made with an elderly person when determining the proper antimicrobial? (4).
- Renal impairment
- Deceased plasma proteins
- Reduced gastric motility and acidity
- Increased body fat.
Bactericidal means?
Killing the bacteria
Bacteriostatic means?
Preventing the bacterium from reproducing, does not necessarily kill/damage the bacteria.
Is PCN bacteriostatic or bactericidal?
Bactericidal
How does PCN kill the bacteria?
By interfering with the cell wall. Doesn’t allow the cell wall to join correctly and interferes with an enzyme that keeps the cell wall stable.
What three organisms (did Denise mention) that PCN is effective against?
- pneumococcal
- Meningococcal
- Streptococcal
How is PCN excreted?
Renal
PCN is part of what family of antimicrobials?
Beta-lactam.
What is the big difference between PCN and ampicillin?
Ampicillin has a wider range of activity including gram negative bacilli (H. influenzae and E coli)
Of the PCN class which has the highest incidence of a skin rash?
Ampicillin
What is the main difference between amoxicillin and ampicillin?
Amoxicillin is more efficiently absorbed from the GI tract than ampicillin.
What is the most common side effect of the PCN class? What symptoms can be seen?
Hypersensitivity.
Rash and or fever, immediate anaphylactic reaction and rarely hemolytic anemia
How long can the hypersensitivity reaction from PCNs be delayed?
up to 24 hours.
Of all the microbials which is the most allergenic?
The PCN family.
Which class of drugs exhibits cross-sensitively with PCNs?
Cephalosporins.
Are cephalosporins bactericidal or bacteriostatic?
Bactericidal
How do cephalosporins kill the bacterium?
Inhibits cell wall synthesis.
What larger family are the cephalosporins a part of?
Beta-lactam.
What kind of spectrum of action do cephalosporins exhibit?
Broad
How are cephalosporins excreted?
60% through the kidneys
40% through the bile
What type of adverse reactions are associated with cephalosporins?
Allergic reactions causing a rash
Anaphylactic reaction in 0.02% of treated patients
What were cephalosporins cross sensitive with again?
PCNs
How many generations (per Denise, not any of the books) are there of cephalosporins? What does the classification depend on?
3.
Classification depends on the antimicrobial spectrum.
Name a first generation cephalosporin and an advantage to using it.
Cefazolin, because it is the least expensive
What is the most commonly used antimicrobial in surgical prophylaxis?
Cefazolin
Name a second generation cephalosporin.
Cefoxitin
Name a third generation cephalosporin.
Cefotaxime
P.S. we should get credit for merely spelling all this shit correctly
Which cephalosporins penetrate into joints?
All of them.
As you go up the generations of cephalosporins (1 to 2 to 3) they are more effective against what?
Gram negative bacteria
Are aminoglycosides bactericidal or bacteriostatic? Generally, how do they exert their effect?
- Bactericidal.
2. Act on protein synthesis within the cell wall of the bacteria.
What class of bacteria is the aminoglycoside family of antimicrobials affect againts?
Aerobic gram negative bacteria.
How are aminoglycosdies excreted?
Extensively renal excretion.
What is the elimination half time of the aminoglycosides? How much does it increase with renal failure?
- 2-3 hour elimination half time
2. Increased 20-40 fold with renal failure.
Name four adverse reactions that are associated with aminoglycosides.
- Ototoxicity
- Nephrotoxicity
- Skeletal muscle weakness
- Prolongs neuromuscular blockade.
Define ototoxicity, explain how an aminoglycoside causes it, state what it is usually dependent on and whether or not it is reversible.
- Ototoxicity is vestibular/auditory dysfunction
- Is caused by drug induced destruction of vestibular or cochlear sensory hairs.
- It is dose dependent- usually occurs with chronic therapy.
- Usually irreversible
Explain how aminoglycosides can cause nephrotoxcicity.
State what this nephrotoxicty results in.
State whether this nephrotoxicity is reversible or not.
Name the most nephrotoxic of the aminoglycosides.
- Drug accumulates in the renal cortex causing tubular necrosis
- Results in the inability to concentrate the urine (first sign), proteinuria and RBC casts.
- Reversible
- Neomycin
Explain two ways which aminoglycosides can result in skeletal muscle weakness, name a disease that is uniquely sensitive to weakness, state whether a single dose in a healthy patient is or isn’t a problem and name two classes of drugs that’s actions are prolonged by this class of antimicrobials.
- Can inhibit pre-junctional release of acetylcholine and decerse the post synaptic sensitivity to the neurotransmitter.
- Myasthenia Gravis.
- A single dose in a healthy patient is not usually a problem.
- Non-depolarizing and depolarizing muscle relaxants.
Explain when aminoglycosides can result in a potentiation of neuromuscular blockade (two), could this happen outside of the OR, name a drug that is enhanced and considerations that must be made when reversing a patient.
- Potentiation of NM blockade can result from high plasma concentration when given IV and from systemic absorption from large volumes of irrigation.
- The reappearance of NM blockade can reappear outside the OR, maybe in the PACU
- NM blocking properties of lidocaine are enhanced.
- Neostigmine or calcium induced antagonism may be incomplete or transient (use your clinical judgement even if you have a decent train of four).
Steptomycin and Kanamycin (aminoglycosides) have what type of use? What is the most frequent adverse reaction associated with them?
- Limited use.
2. Vestibular Damage
Gentamicin (aminogylcoside) has what type of spectrum when compared to other drugs in this family? What does this drug require? What is the toxic level?
- Broader spectrum
- Monitoring drug levels because of it’s high toxic profile
- Over 9mcg/ml
Amikacin (aminogylcoside) is a derivative of which drug?
Kanamycin.
Neomycin (aminoglycoside) is used as an adjunct therapy for what condition? Why?
- Hepatic Coma
2. To decrease plasma ammonia levels.
Are tetracyclines bactericidal or bacteriostatic? How do they act?
- Bacteriostatic
2. Inhibits bacterial protein synthesis.
What type of spectrum do the tetracyclines have?
Broad.
What are the tetracyclines usually used for? Why?
- Treatment of acne
2. Because they decrease the fatty acid content of the sebum.