Antimicrobials Flashcards
Should all surgical cases get an antibiotic?
No, you should weigh the risks and benefits. Is it worth exposing the patient to an antibiotic? For example, thyroid surgeries tend to NOT get infected. So you might hold off in this case.
What are the 3 general rules for using antibiotics in the surgical setting?
- You want to inhibit microorganisms as a level that is tolerated by the host. 2. In the seriously ill or immunocompromised you should use bactericidal as opposed to bacterostatic 3. Use a narrow spectrum before a broad spectrum to target a specific organism to preserve the patients normal flora.
When choosing an antibiotic for a patient is cost a factor?
Yes, providers need to choose cost effective antibiotics.
When choosing an antibiotic that seems cost effective, what is one thing you should consider?
Most of the cheaper antibiotics are broad spectrum. You must consider the benefit/risk of exposing the patient to a broad spectrum.
When should a surgical prophylactic antibiotic be given?
No more than 1 hour before incision, but completed before incision.
Are surgical prophylactic antibiotics a single-dose deal?
No, they can be continued for 48 hours in some cases.
Will giving a patient a brief course of antibiotics prophylactically increase resistance in organisms?
There is no evidence that a short course increases resistance.
When choosing an antibiotic for active infection, is it essential to identify the a causative organism?
Yes, so in this case, if there is an infected site that needs a washout or drained out, you may want to hold off on that first dose of antibiotic until after the intial incision is made and after samples for culture can be obtained.
Efficacy of antibiotic will depend on it’s _________ to the site of infection
delivery. Consider transport across blood brain barrier, if you have to deliver antibiotic to brain. Also, antibiotics will more readily penetrate infected tissue after it has been debrided and infectious material removed.
True or False. Using multiple antibiotics is the preferred method of treatment of infection.
False. Usually you treat with a single drug.
Does the route of administration need to be considered?
Yes. If it is orally administered it might suffer first pass metabolism and the complete dose will not reach the target tissue.
Does the duration of treatment need to be considered when choosing an antimicrobial?
Yes, is the patient going to have to take this medication at home?
What are the 2 main types of reactions that occur with antibiotics?
- Hypersensitivity 2. Direct drug toxicity
Does the dose of the antibiotic have anything to do with a hypersensitivity reaction?
No. It doesn’t matter what dose you gave, hypersensitivity can occur at even the smallest doses.
Does the antibiotic dose have anything to do with direct drug toxicity?
Yes. If you give more than can be cleared, the drug will reach toxic levels in the bloodstream.
What should you consider when giving antibiotics to a pregnant mother?
- most antimicrobials cross the placenta and enter breast milk. (Moms should discard milk for 24 hours) 2. We should be concerned with teratogenecity with any drug.
What are 4 physiological changes in the elderly that we need to consider when giving them antibiotics?
- They may have renal or liver impairment 2. They have decreased plasma proteins 3. Reduced gastric acid and motility 4. Increased body fat.
What would a decrease in plasma protein have to do with antibiotics?
If there are less plasma proteins for the medication to bind to then there is a higher free fraction of the drug in the bloodstream.
What is the difference between bactericidal and bacteristatic?
Bacterocidal drugs kill bacteria by disrupting cell wall synthesis. Bacteristatic drugs inhibit bacterial protein synthesis.
Is penicillin bactericidal or bacteristatic?
bactericidal
What family is pencillin part of?
the beta lactams
Which 3 main organisms does penicillin target?
pneumococcal, meningococcal, streptococcal.
How is PCN excreted?
90% of it is renally excreted
Name 2 derivatives of penicillin that we commonly see?
Ampicillin and Amoxicillin
Which has a wider range of activity, ampicillin or penicillin?
Ampicillin, it covers all the same stuff and penicillin plus some gram - like Haemophilus influenzae and E. Coli
Which is associated with a higher incidence of skin rash, ampicillin or amoxicillin?
ampicillin
Which is more effectively absorbed from the GI tract, ampicillin or amoxicillin?
amoxicillin
Which is more commonly used in pediatrics, amoxicillin or ampicillin?
Amoxicillin, because it can be given PO.
What is the most common adverse reaction to the pencillins?
hypersensitivity
Which is the most allergenic of all of the antibiotics?
Pencillin
What are 3 allergic type responses to penicillin?
Rash (with or without fever) anaphylaxis (immediate) and hemolytic anemia (this is rare)
What if a patient with with a penicillin allergy is ordered a cephalosporin?
There is an 8% chance of cross-sensitivity in patients with penicillin allergies who receive a cephalosporin. You may want to choose another drug, but at least you should give a test dose before administering
What do penicillin and cephalosporins have in common?
They have the same type of beta lactam ring
Are Cephalosporins bactericidal or bacterostatic?
bactericidal (damages cell wall synthesis)
Are cephalosporins broad or narrow spectrum?
broad
How are cephalosporins excreted?
Mainly by the kidney, but not as extensively as penicillin. 40% of a cephalosporin is excreted in the bile.
What is the most common allergic reaction to a cephalosporin?
rash
What percentage of patients receiving a cephalosporin have an anaphylactic reaction to it?
0.02% of treated patients
What 3 antibiotic types make up the beta lactam family and therefore could have cross-sensitivity reactions?
Penicillins, Cephalosporins, and Carbopenems
How many generations of cephalosporin antibiotics are there?
3
What is the difference between the generations of cephalosporins?
First generation are cheaper. As you move down to 3rd generation they get more effective against gram neg. bacteria.
Is Cefazolin a 1st, 2nd, or 3rd generation cephalosporin?
1st
Is cefoxitin a 1st, 2nd, or 3rd generation cephalosporin?
2nd
Is cefotaxime a 1st, 2nd, or 3rd generation cephalosporin?
3rd
Are cephalosporins ok to use in joint surgery?
Yes, the cephalosporins will all penetrate into joints.
Bacteriostatic agents ____________ the growth or replication of organisms but do not ________ the offending organism.
interfere with growth; do not kill
What is minimum inhibitory concentration?
the lowest concentration of a given antimicrobial at which an organisms growth is inhibited (this pertains to bacteriostatic agents)
Bactericidal agents _______ bacteria
kill
Are aminoglycosides bacteriostatic or bactericidal?
bactericidal
How does the bactericidal action of aminoglycosides work?
They destroy protein synthesis, but not at the cell wall, they enter the cell and destroy protein synthesis inside the cell, killing it.
Aminoglycosides are effective against ________ bacteria.
Gram negative
How are aminoglycosides excreted?
extensively excreted by the kidney
What is the elimination half-time of aminoglycosides?
2-3 hours
What happens to the elimination half time of aminoglycosides in patients with renal failure.
Increases 20-40 times! Watch the BUN/ Cr in these patients.
Name 3 side effects of aminoglycosides.
- ototoxicity 2.nephrotoxicity 3.skeletal muscle weakness
What effect do aminoglycosides have on neuromuscular blockade?
they prolong it
Is the ototoxicity associated with aminoglycosides dose dependent?
Yes, it is more likely to occur with chronic therapy
Describe the ototoxicity associated with aminoglycosides, what happens in the ear?
Vestibular/ auditory dysfunction occurs. There is drug-induced destruction of vestibular or cochlear sensory hairs. This can cause vertigo, ataxia, hearing loss, including complete deafness
Is the nephrotoxicity associated with aminoglycosides reversible?
Yes
Which aminoglycoside is the most nephrotoxic?
Neomycin
What is usually the first thing you will notice in aminoglycoside induced nephrotoxicity?
an inability to concentrate urine, watch that foley bag.
What are the changes you will see in the urine of a patient suffering from aminoglycoside induced nephrotoxicity?
inablity to concentrate urine, RBC casts in urine, and proteinuria
How exactly does the aminoglycoside induced nephrotoxicity damage the kidney?
Aminoglycoside accumulates in the renal cortex leading to tubular necrosis.
What happens to patients with mysasthenia gravis who get aminoglycosides?
Patients with myasthenia gravis are uniquely sensitive to the skeletal muscle weakness side effect associated with aminoglycosides.
If I have given my patient an aminoglyoside, and now I am ready to paralyze, would it matter if I used a depolarizing agent or a non-depolarizing agent to paralyze my patient?
No, it doesn’t matter, both will be affected by the aminoglycoside and can cause prolonged muscle weakness.
What happens at the neuromuscular junction in patients who have received an aminoglycoside and paralytic?
aminoglycosides can inhibit pre-junctional release of AcH and decrease post-synaptic sensitivity to the neurotransmitter.
True or False. A single dose of aminoglycoside in a healthy patient can cause problems.
False. It is usually not a problem.
Your patient getting a wound debridement has received a pre-op aminoglycoside, what else should you be aware of when giving a neuromuscular blocker?
Irrigation fluids used in wound debridement may have antibiotics in them, including aminoglycosides which could increase plasma concentrations of the drug. Remember… aminglycosides potentiate neuromuscular blockade.
At the end of the case, the neuromuscular blocker has worn off enough that your patient is breathing spontaneously again. They are ready to transfer to PACU, but they received an aminoglycoside during the case, what should you be aware of in PACU?
you can see an re-appearance of neuromuscular blockade in patients who have received aminoglycosides.
When lidocaine is used in cases where an aminoglycoside was given, what can happen?
the neuromuscular blocking properties of lidocaine will be enhanced.
rue rueIf my patient has been given an aminoglycoside, and I used a neuromuscular blocker, giving neostigmine will still work to reverse its effects. T or F.
False. neostigmine or calcium antagonism of neuromuscular blockade may be incomplete or transient in patients who have received aminoglycosides
If the train of 4 is normal, my patient is reversed and will not experience the side effect of aminoglycoside induced muscle weakness. T or F.
False. Even with a normal train of 4, my patient still may suffer prolonged muscle weakness.
Name 5 aminoglycosides.
Streptomycin and Kanamycin, Gentamicin, Amikacin, and Neomycin
Name this aminoglycoside. Used once to treat bubonic plague. Limited use now due to vestibular damage.
Streptomycin (or Kanamycin). Streptomycin specifically was used to treat plague.
Name this aminoglycoside. I am broader in spectrum that streptomycin. I am toxic at levels greater than 9 mcg/ml.
Gentamicin
Name this aminoglycoside. I am a derivative of kanamycin.
Amikacin
Name this aminoglycoside. I am used as adjunct therapy in hepatic coma to decrease ammonia levels. I am not usually given IV because of toxic effects. I used to be used routinely in burn dressings until my toxicity became an issue. I am one of the components of neosporin.
Neomycin
Are tetracyclines bacteriostatic or bactericidal?
Bacteriostatic (this is the brown stuff lining the central lines)
Because tetracylcines are bacteriostatic they kill bacteria. T or F
False. Bacteriostatic antibiotics don’t kill they just prevent protein synthesis.
Tetracycline decreases the fatty content in sebum and therefore is a good treatment for _________.
acne
How are tetracylcines excreted?
urine and bile
What are two main adverse reactions/ side effects associated with tetracyclines?
Photosensitivity and tooth discoloration
In what patient population does tooth discoloration from tetracyclines most commonly occur in?
children. you should also use caution in giving tetracycline to pregnant women, as the drug can cross the placenta and stain the baby’s teeth.
How exactly, does tetracycline stain the teeth?
It deposits in the teeth and bones forming tetracycline-orthophosphate-calcium complex
What is meant by phototoxicity related to tetracycline?
a sensitivity to sun and sunlight.
Is tetracycline given IV or PO?
PO only