Exam 1: ABX Flashcards
Goals and General Rules
- Inhibit microorganisms at concentrations that are tolerated by the host
- Seriously ill/immunocompromised select bactericidal
- Narrow spectrum before broad spectrum or combination therapy to preserve normal flora
- OR – use broad-spectrum, bc you want to kill what would infect the surgical area, or
- Or continue abx in the OR for when they’re due
-If doing cx’s during the case, they will likely want you to give the abx AFTER the cx has been taken
Antimicrobial Therapy and Anesthesia Practice: Why do we care
(3 main reasons)
o Prophylaxis before surgery:
- Anesthesia plays important role in timely administration of ABXs – w/i 1 hour of incision
- Reimbursement for quality care
o Potential for adverse reactions
-Hypersensitivity Reaction (dose independent)
-Direct organ toxicity (dose related)
-Potential for superinfections
-Identify patients at risk for complications
• Elderly – less organ fn, and won’t clear drugs quickly
• Parturient – cross BBB
o Cross-reactions with other medications we give
SSI definition
o SSI defined as an infection related to an operative procedure that occurs at or near the surgical incision within 30 days of the procedure:
- Purulent exudate draining from a surgical site
- A positive culture obtained from a surgical site that was closed initially
- A surgeon’s diagnosis of infection
- A surgical site that requires reopening due to at least one of the following signs or symptoms: tenderness, swelling, redness or heat
Factors that increase risk for devt of SSIs (surgical site infections)
o SURGICAL RISK
- Procedure Type
- Skill of surgeon
- Use of foreign material or implantable device
- Degree of tissue trauma
o PATIENT RISKS
- Diabetes
- Smoking use
- Obesity
- Malnutrition – low protein to support fns
- Systemic steroid use
- Immunosuppressive therapy
- Intraoperative hypothermia – constricts bv’s, slows metab rate, blood more viscous, won’t flow to the places it needs, oxy-hgb shifts to the L (hgb will hold on to O2, “Left, loves O2”)
- Type of surgery might lend itself to infxns - brain, bone vs. thyroid surgery – lots of lymph nodes in that area, relatively clean area
- Trauma – degree of tissue trauma
- Prosthetic heart valves
- Always weigh risk-benefit ratio
- Surgeon’s skill – less chance is quick, some sloppy
SSI Prevention tenets
o According to the literature most SSIs are preventable
o Surgical Care Improvement Project (SCIP)
o Anesthesia providers can make an impact on prevention through:
- Timely and appropriate use of antibiotics
- Maintenance of normothermia
- Proper syringe/med administration practices
SBE prophylaxis protocol
o Standard general prophylaxis:
- Amoxicillin 2gm PO
OR - IV amipicillin 2gm IV
o PCN allergic
- Clindamycin 600 mg IV
- Cefazosin 1gm IV (NOT IN pts with hypersensitivity to PCN)
o Use this protocol in ppl who have
- Heart valves
- Ppl who have have bacterial endocarditis in the past
- Transplants
- Congenital heart dz that has been unrepaired, or was repaired and still have defects
SSI (Surg Site Infection) Prevention
• Antibiotic Timing
- Antibiotic prophylaxis 1 hour before incision had the lowest rate of SSI
- 30-60 minutes before incision is the ideal window for drug administration
• Normothermia
- Hypothermia is associated with adverse outcomes which include: Increased blood loss,Increased transfusion requirements, Prolonged PACU stay, Post-op pain, Impaired immune function
- Compromised Neutrophil function → vasoconstriction → tissue hypoxia and increased incidence of SSI
o Glucose control is important in all surgical pts, but especially in cardiac surgery pt.
- Lots of instances of mediastinal site questions
- <200 mg/dl or even 160 as cutoff during surgery
Classes of Abx
• Types of antibiotics
o Antibiotics are categorized
o bactericidal if they kill the susceptible bacteria (usually preferred)
o bacteriostatic if they reversibly inhibit the growth of bacteria. (usually UTIs)
o In general the use of bactericidal antibiotics is preferred but many factors may dictate the use of a bacteriostatic antibiotic.
o When a bacteriostatic antibiotic is used the duration of therapy must be sufficient to allow cellular and humoral defense mechanisms to eradicate the bacteria.
• Bactericidal vs bacteriostatic
List some bactericidal and bacteriostatic drugs
• Bactericidal - PIMP VARB (F?)Q o Penicillin's & Cephalosporin's o Isoniazid o Metronidazole o Polymyxins o Rifampin o Vancomycin o Aminoglycosides o Bacitracin o Quinolones - Fluroquinolones?
• Bacteriostatic - CCM TTS o Chloramphenicol o Clindamycin o Macrolides (erythromycin/azithromycin) o Sulfonamides (sulfamethoxazole, trimethoprim) o Tetracyclines o Trimethoprim
PCN (1st generation) - MOA, organisms, excretion, DOA
Are they bactericidal or bacteriostatic?
(Basically PK)
“PCN - peptidoglycan prevention (no cell membrane) - probenecid (used for gout) prolongs renal excretion”
o Basic structure is a dicyclic nucleus that consists of a thiazolidine ring connected to a B-lactam ring
(Won’t ask us this in this way)
*Bascially cell membrane can’t form and bacterium can’t live
o **Bactericidal: Interferes with the synthesis of peptidoglycan which essential component to cell walls of susceptible bacteria. – inhibits the enzyme, which is needed to keep the bacterium intact. SO the contents will exude.
o Organisms
- pneumococcal
- meningococcal
- streptococcal
- actinomycosis
o Excretion
- Renal excretion is rapid-plasma concentration decreases 50% in 1st hour
• 10% glomerular filtration
• 90% renal tubular secretion
• Anuria increases elimination half-time by 10 fold
o Duration of Action
- Administration of probenecid (used to tx gout) will reduce renal excretion and prolong action
PCN Adverse Rxns
Hypersensitivity-most allergenic of all the antimicrobials (up to 10%):
• Rash +/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)
2nd generation PCNs (organisms and names of drugs)
o Organisms
- pneumococcal
- meningococcal
- streptococcal
- actinomycosis
- Wider range of activity
• Gram negative- bacilli - Haemophilus influenza
• E coli
o Amoxicillin
o Ampicillin
o ** patients with documented IgE mediated anaphylactic reactions the B-lactum antibiotics can be substituted with Clindamycin or Vancomycin – they should not get 2nd generation PCN!!!
Aside: As you go up in generation, you go up in price (ancef is cheap)
Cephalosporins
Are they bactericidal or bacteriostatic?
(Basically PK)
Cefazolin (will prob use most often)
o Bactericidal antimicrobials that inhibit bacterial cell wall synthesis and have low toxicity
- Broad spectrum activity
- Allergy incidence is 1-10%
- anaphylaxis is 0.02%
- cross reactivity with other cephalosporins
- Penicillin and Cephalosporin allergy 1-3%
***DO NOT USE if outright anaphylactic rxn. But if they can’t recall, you could be asked to give a test dose of a few 100 mg of it, then see if there’s a rxn, then infuse the rest of it
- Renal excretion
1st gen: cefazolin
2nd cefoxitin
3rd cefotaxime
All cephalosporins go into joints, and cross placenta.
Macrolides - name of drugs, and PK of “prototype” of this class (no SEs)
(Erythromycin, Azithromycin)
MACRO-GLIDES DOWN - increased peristalsis, cramps, N/V
MACRO QTC - prolonged repolarization, r/f Torsades
o Useful for patients with sensitivities to PCNs and cephalosporin drugs
- Compounds characterized by a macrolytic lactone ring containing 14-16 atoms with a deoxy sugar attached
- **Erythromycin is the Prototype
- Effective against Gram positive bacilli, pneumococci, streptococci, staphylococci, mycoplasma, chlamydia
o Erythromycin
- Bacteriostatic or bactericidal – depends on organism, or dose!
- Inhibits bacterial protein synthesis
- Metabolized by the cytochrome P-450 system and thus increase serum concentration of theophylline, warfarin, cyclosporine, methylprednisone and digoxin
- Excreted mostly in bile
- No need to alter dose in renal disease
Macrolides SEs
MACRO-GLIDES DOWN - increased peristalsis, cramps, N/V
MACRO QTC - prolonged repolarization, r/f Torsades
- GI intolerance - increases peristalsis (→ cramps!) And gastric emptying!
- Most common side effect
- Severe N/V can occur with IV infusion
- Gastric emptying
- Cholestasic hepatitis
- QT effects
- Prolongs cardiac repolarization
- Reports of torsades de pointes
- Thrombophlebitis (common with prolonged IV use)
