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Questions and Answers
Antibiotics administered before contamination of previously sterile tissues are considered prophylactic.
Antibiotics administered before contamination of previously sterile tissues are considered prophylactic.
True
S.aureus and coagulase-negative staphylococci are known as common surgical pathogens after clean procedures.
S.aureus and coagulase-negative staphylococci are known as common surgical pathogens after clean procedures.
True
Vancomycin is the preferred choice of prophylactic antibiotic for all types of surgical procedures.
Vancomycin is the preferred choice of prophylactic antibiotic for all types of surgical procedures.
False
Antimicrobial prophylaxis is appropriate for dirty surgical operations.
Antimicrobial prophylaxis is appropriate for dirty surgical operations.
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The choice of prophylactic antimicrobial depends solely on the cost of the medication.
The choice of prophylactic antimicrobial depends solely on the cost of the medication.
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First-generation cephalosporins are preferred for clean surgical procedures.
First-generation cephalosporins are preferred for clean surgical procedures.
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Prolonged antibiotic prophylaxis can encourage the proliferation of resistant micro-organisms.
Prolonged antibiotic prophylaxis can encourage the proliferation of resistant micro-organisms.
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Gö-β-lactam hypersensitivity can lead to the use of clindamycin instead of cefazolin.
Gö-β-lactam hypersensitivity can lead to the use of clindamycin instead of cefazolin.
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Deep venous thrombosis (DVT) is most common in patients under 40 years of age who undergo major surgery.
Deep venous thrombosis (DVT) is most common in patients under 40 years of age who undergo major surgery.
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Gram-positive coverage is not typically included in surgical prophylaxis choices.
Gram-positive coverage is not typically included in surgical prophylaxis choices.
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Combination antimicrobial therapy is mainly used to narrow the spectrum of coverage.
Combination antimicrobial therapy is mainly used to narrow the spectrum of coverage.
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Clean-contaminated procedures primarily involve gram-negative rods and enterococci along with skin flora.
Clean-contaminated procedures primarily involve gram-negative rods and enterococci along with skin flora.
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Mechanical devices such as Thromboembolic deterrent stockings (TEDS) are one type of thromboprophylaxis.
Mechanical devices such as Thromboembolic deterrent stockings (TEDS) are one type of thromboprophylaxis.
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Fondaparinux increases the risk of bleeding compared to low molecular weight heparin (LMWH).
Fondaparinux increases the risk of bleeding compared to low molecular weight heparin (LMWH).
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The risk of developing DVT is assessed for all patients upon admission to the hospital.
The risk of developing DVT is assessed for all patients upon admission to the hospital.
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Intravenous administration of antimicrobials is preferred over intramuscular administration for its reliability.
Intravenous administration of antimicrobials is preferred over intramuscular administration for its reliability.
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Oral administration of non-absorbable compounds is sufficient on its own and can replace intravenous agents.
Oral administration of non-absorbable compounds is sufficient on its own and can replace intravenous agents.
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The first dose of antimicrobial for surgical prophylaxis should be given 60-120 minutes before the first incision.
The first dose of antimicrobial for surgical prophylaxis should be given 60-120 minutes before the first incision.
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Exceptions to the timing rule for antimicrobial infusion include fluoroquinolones and vancomycin, which can be infused 120 minutes prior.
Exceptions to the timing rule for antimicrobial infusion include fluoroquinolones and vancomycin, which can be infused 120 minutes prior.
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Repeat dosing during an operation is unnecessary if it exceeds two half-lives of the selected antimicrobial.
Repeat dosing during an operation is unnecessary if it exceeds two half-lives of the selected antimicrobial.
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Cefazolin has a half-life of about 4 hours, thus requiring a repeat dose if the operation exceeds 4 hours.
Cefazolin has a half-life of about 4 hours, thus requiring a repeat dose if the operation exceeds 4 hours.
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The continuation of antimicrobial prophylaxis beyond wound closure is generally necessary.
The continuation of antimicrobial prophylaxis beyond wound closure is generally necessary.
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Antimicrobial prophylaxis should not exceed 24 hours, except for cardiac surgery where it can be extended to 48 hours.
Antimicrobial prophylaxis should not exceed 24 hours, except for cardiac surgery where it can be extended to 48 hours.
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Continuing antibiotics until all drains are removed effectively reduces the infection rate.
Continuing antibiotics until all drains are removed effectively reduces the infection rate.
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The goal of antimicrobial dosing is to maintain antibiotic concentrations below the MIC of suspected organisms during surgery.
The goal of antimicrobial dosing is to maintain antibiotic concentrations below the MIC of suspected organisms during surgery.
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Study Notes
Surgical Prophylaxis
- Antibiotics administered before contamination of sterile tissues or fluids are considered prophylactic, aiming to prevent infection.
- Skin flora (including S. Aureus and coagulase-negative staphylococci, e.g., Staphylococcus epidermidis) are predominant organisms causing Surgical Site Infections (SSIs) after clean procedures.
- In clean-contaminated procedures (e.g., abdominal, heart, kidney, and liver transplantations), gram-negative rods and enterococci, alongside skin flora, are the primary organisms.
Antimicrobial Selection
- Prophylactic antimicrobial choice depends on surgical procedure, pathogen likelihood, antimicrobial safety, efficacy, current evidence, and cost.
- Gram-positive coverage (e.g., S. aureus, S. epidermidis) is usually included in surgical prophylaxis.
- Parenteral antibiotic administration is preferred for reliable tissue concentration.
- First-generation cephalosporins (e.g., cefazolin) are the preferred choice for clean procedures.
- Broad-spectrum coverage (e.g., cefoxitin, or cefotetan) may be needed for anaerobic or gram-negative coverage cases.
- Vancomycin can be considered if methicillin-resistant S. aureus (MRSA) risk is high.
- Clindamycin can be an alternative to cefazolin for certain cases.
Types of Surgical Operations
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Surgical operations are classified as clean, clean-contaminated, contaminated, or dirty.
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Antimicrobial prophylaxis is suitable for clean, clean-contaminated, and contaminated procedures.
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Non-prophylactic antibiotics are used for treatment in operations with existing infections.
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Table 1 (in the provided text) outlines classification, surgical site infection risk, and antibiotic indication.
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Clean: Uninfected wounds with no inflammation in closed procedures
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Clean-Contaminated: Wounds involving organs (e.g., biliary tract) under controlled conditions
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Contaminated: Open wounds or wounds with gross spillage from the gastrointestinal tract
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Dirty: Wounds with obvious preexisting infection (e.g., abscess, pus)
Principles of Antimicrobial Prophylaxis
- Intravenous (IV) administration is preferred for reliable serum/tissue concentration over intramuscular.
- Oral antibiotics can be used adjunctively in some cases (e.g., bowel operations) to reduce microbial counts in the bowel.
- Oral agents are not typically a replacement for IV agents.
Timing of First Dose
- A single dose of antimicrobial is ideal 30 minutes to 1 hour before incision, providing sustained levels in the blood and wound.
- For fluoroquinolones and vancomycin, administration may occur up to 2 hours before incision to avoid complications.
Dosing and Redosing
- Maintaining antibiotic concentrations above the minimum inhibitory concentration (MIC) is crucial for the duration of the surgery.
- Redosing is required when the duration of surgery exceeds the drug's half-life to maintain needed antimicrobial concentrations.
- Clinicians should have necessary extra doses for longer-than-expected surgeries.
Duration
- Antimicrobial prophylaxis beyond wound closure or 24 hrs (48 hrs for cardiac surgery) is generally unnecessary.
- Preventing the unnecessary use of antibiotics beyond needed time frames is promoted.
Combination Antimicrobial Therapy
- Using combinations of antimicrobials broadens the spectrum of coverage to tackle mixed infections, optimize effectiveness, and prevent resistant organisms.
- Effective in cases of various infections (intra-abdominal, female pelvic).
- Increased spectrum of activity is beneficial for nosocomial infections.
Thromboprophylaxis
- Deep vein thrombosis (DVT) is frequent in major surgery, particularly in patients older than 40.
- Postoperative increases in platelets, and venous trauma contribute to DVT risk.
- Thromboprophylaxis (prevention of DVT) is given to reduce the occurrence of DVT and associated risks.
- Mechanical devices (e.g., thromboembolic deterrent stockings) and drugs (e.g., heparin, LMWH) are used for prophylaxis.
Regimen
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National guidelines exist for VTE prophylaxis, which involve assessing risk factors and using anticoagulants (e.g., heparin, enoxaparin, fondaparinux) preoperatively and during the initial stages of the postoperative phase.
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Various factors like surgery type and the patient's medical history are considered to manage the risk of VTE.
Table 2
- The table provides likely pathogens and recommended prophylaxis regimens for common surgical procedures (e.g., gastroduodenal, biliary tract procedures) in the table. High-risk patients, specific to each procedure, are highlighted in the comments section.
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Description
This quiz covers the essential concepts of surgical prophylaxis and antimicrobial selection. It addresses the role of antibiotics in preventing infection during surgical procedures and the criteria for choosing the appropriate antimicrobial agents. Test your understanding of the pathogens involved and the best practices for antibiotic administration.
