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Questions and Answers

What is the primary characteristic of a Class I/Clean operative wound?

The wound is contaminated with bacteria from the gastrointestinal tract

The respiratory tract is entered under controlled conditions

There is a major break in sterile technique

No inflammation is encountered and the wound is primarily closed (correct)

Which of the following operations would be classified as a Class II/Clean-Contaminated wound?

An open, fresh, accidental wound

A wound with retained devitalized tissue

A surgical incision with acute inflammation

An operation involving the oropharynx (correct)

What is a characteristic of a Class III/Contaminated wound?

The wound is free of acute inflammation

The wound is primarily closed and shows no signs of inflammation

The wound is contaminated with bacteria from the biliary tract

There is a major break in sterile technique (correct)

Which of the following would be classified as a Class IV/Dirty-Infected wound?

An old traumatic wound with retained devitalized tissue Signup and view all the answers

What is the main difference between Class III/Contaminated and Class IV/Dirty-Infected wounds?

The presence of retained devitalized tissue Signup and view all the answers

What is implied by the definition of Class IV/Dirty-Infected wounds?

The organisms causing postoperative infection were present in the operative field before the operation Signup and view all the answers

What are the consequences of bronchospasm?

↓ ETCO2 and SaO2, ↑ PIP Signup and view all the answers

What is a severe skin and mucous membrane disorder?

Stevens-Johnson Syndrome Signup and view all the answers

What is the primary goal of insulin administration in perioperative patients?

To keep blood glucose levels below 200 mg/dl Signup and view all the answers

Why is the IV route preferred over the subcutaneous route for insulin administration in perioperative patients?

Because the subcutaneous route may not be reliable in patients who are hypothermic or vasoconstricted Signup and view all the answers

In which type of surgical procedures may insulin administration not be necessary?

Minor surgical procedures Signup and view all the answers

What is the recommended blood glucose range for patients undergoing CT or colorectal surgery?

Between 140-180 mg/dl Signup and view all the answers

What is a potential complication of uncontrolled blood glucose levels in perioperative patients?

Stevens-Johnson Syndrome Signup and view all the answers

What is the specific reaction inhibited by thiazolidine connected to a Beta-lactam ring?

Transpeptidation reaction Signup and view all the answers

What is a limitation of Pen G in terms of its ability to target bacterial cells?

It is unable to cross the inner cytoplasmic bilayer of gram-negative cells Signup and view all the answers

What is the primary mechanism by which 1st generation penicillins are eliminated from the body?

Tubular secretion Signup and view all the answers

Why should caution be exercised when administering 1st generation penicillins to patients with renal disease?

Reduced clearance due to low urine output Signup and view all the answers

Which of the following 1st generation penicillins is NOT rapidly excreted by the kidneys?

Nafcillin Signup and view all the answers

What is the spectrum of antibacterial activity of 1st generation penicillins?

Both gram-positive and gram-negative Signup and view all the answers

What is a characteristic of Pen G that increases its susceptibility to degradation?

Susceptibility to Beta-lactamases Signup and view all the answers

Why is Nafcillin not used orally?

Its absorption is unpredictable Signup and view all the answers

What is a precaution that should be taken when administering Pen G to patients with renal disease?

Administer with caution due to nephrotoxicity Signup and view all the answers

How is Nafcillin primarily eliminated from the body?

Through biliary excretion Signup and view all the answers

What is the significance of the 10 million units of Pen G being equal to 16 mEq of K+?

It indicates the potassium content of the drug Signup and view all the answers

What is a characteristic of amoxicillin that distinguishes it from ampicillin?

Better absorption from the GI tract Signup and view all the answers

What is a potential side effect of 2nd generation penicillins?

Rash due to commercial preparation Signup and view all the answers

Which of the following 2nd generation penicillins is longer acting?

Amoxicillin Signup and view all the answers

What is a characteristic of 2nd generation penicillins?

Bactericidal against gram-positive and gram-negative bacteria Signup and view all the answers

What is a unique consideration when administering carbenicillin to patients with congestive heart failure?

It's high sodium content Signup and view all the answers

What is the effect of probenecid on plasma carbenicillin concentration?

Increases it by 50% Signup and view all the answers

Why is carbenicillin typically administered intravenously?

It is not absorbed by the gastrointestinal tract Signup and view all the answers

What is the effect of carbenicillin on platelet function?

Interferes with platelet aggregation Signup and view all the answers

What is a characteristic of carbenicillin that distinguishes it from ampicillin?

It is useful for organisms resistant to ampicillin Signup and view all the answers

What is the effect of probenecid on the elimination of certain drugs?

It inhibits the renal tubular excretion of penicillins Signup and view all the answers

Which of the following drugs is NOT affected by probenecid's inhibitory effect on renal tubular excretion?

Metformin Signup and view all the answers

What is the purpose of pairing probenecid with penicillins?

To increase the plasma levels of penicillins Signup and view all the answers

Which of the following drug's effects are likely to be weakened with concurrent administration of probenecid?

All of the above Signup and view all the answers

What is the mechanism by which probenecid increases the plasma levels of penicillins?

It inhibits the renal tubular excretion of penicillins Signup and view all the answers

What is the mechanism of action of cephalosporins?

Inhibit bacterial cell wall synthesis Signup and view all the answers

What is a common characteristic of cephalosporins that leads to cross-reactivity with penicillins?

Shared beta-lactam ring Signup and view all the answers

What is a potential complication of cephalosporin use?

Thrombophlebitis Signup and view all the answers

What is a characteristic of cephalosporins that makes them suitable for use in certain surgical procedures?

All of the above Signup and view all the answers

What is the recommended dose of Cefazolin for adults weighing over 120 kg?

3 gm IV Signup and view all the answers

What is the primary reason Cefazolin should not be used in patients with an allergy to Cephalexin?

Cefazolin has a similar chemical structure to Cephalexin Signup and view all the answers

What is the recommended re-dosing schedule for Cefazolin in surgical procedures?

Every 3-4 hours or after significant blood loss Signup and view all the answers

What is the maximum dose of Cefazolin recommended in a 24-hour period?

6 gm Signup and view all the answers

What is the recommended pediatric dose of Cefazolin?

15-30 mg/kg IV Signup and view all the answers

What is a characteristic of Cefuroxime that makes it effective in the treatment of meningitis?

It readily crosses into CSF Signup and view all the answers

What is the primary advantage of Cefoxitin over other cephalosporins?

It is resistant to cephalosporinases produced by gram negative bacteria Signup and view all the answers

What is the primary advantage of using Cefuroxime over other antibiotics in treating meningitis?

It can cross into the CSF Signup and view all the answers

What is the primary indication for using Cefoxitin?

Treatment of gram negative bacterial infections Signup and view all the answers

What is the primary concern when using high levels of imipenem?

Seizures Signup and view all the answers

Why is aztreonam suitable for patients with an allergy to PCN?

Low/no cross sensitivity Signup and view all the answers

What is a disadvantage of aztreonam?

It causes enterococcal superinfections Signup and view all the answers

What is a characteristic of neomycin that makes it useful in certain surgical procedures?

It can decrease bacterial flora prior to GI surgery Signup and view all the answers

What is the consequence of combining amikacin with PCNs in the treatment of enterococcus faecalis?

It may antagonize the effect of PCNs Signup and view all the answers

What is the effect of aminoglycosides on the neuromuscular junction?

It decreases the release and sensitivity to acetylcholine Signup and view all the answers

Why should caution be exercised when administering aminoglycosides to patients with renal disease?

Renal disease can increase the elimination half-life of aminoglycosides Signup and view all the answers

What is the effect of calcium administration on the skeletal muscle weakness caused by aminoglycosides?

It decreases the weakness Signup and view all the answers

What is a unique characteristic of gentamicin in relation to bodily fluids?

It penetrates pleural, ascitic, and synovial fluids when inflamed Signup and view all the answers

Why is it essential to monitor plasma levels of gentamicin?

To adjust dosage in patients with renal disease Signup and view all the answers

What is a potential side effect of gentamicin that can present suddenly?

Ototoxicity Signup and view all the answers

What is a common symptom of gentamicin-induced ototoxicity?

All of the above Signup and view all the answers

What should be done to the dosage of gentamicin in patients with renal disease?

Decrease the dosage Signup and view all the answers

What is the primary mechanism of action of Vancomycin?

Inhibition of cell wall synthesis Signup and view all the answers

What is the primary indication for the use of Vancomycin in the treatment of bacterial infections?

All of the above Signup and view all the answers

What is the recommended dosage of Vancomycin in patients with normal renal function?

10-15 mg/kg IV every 12 hours Signup and view all the answers

What are/is the primary side effects to consider when administering Vancomycin?

All of the above Signup and view all the answers

What is the recommended laboratory monitoring for patients receiving Vancomycin therapy?

Renal function tests and trough levels Signup and view all the answers

What is the primary mechanism of action of Linezolid?

Inhibiting bacterial protein synthesis by binding to 50S ribosomal unit Signup and view all the answers

What is a potential short-term effect of Linezolid?

Nausea Signup and view all the answers

What is a characteristic of Vancomycin that can be treated with diphenhydramine?

Flush reaction Signup and view all the answers

What is a long-term effect of Linezolid?

Bone marrow suppression Signup and view all the answers

What is a characteristic that distinguishes Linezolid from Vancomycin?

Incidence of Red Man Syndrome Signup and view all the answers

What is a characteristic of azithromycin?

Long half-life, active 4-7 days after last dose Signup and view all the answers

What is a disadvantage of erythromycin?

GI upset is a common and severe n/v Signup and view all the answers

What is a characteristic of macrolides?

Effective against gram-positive bacteria, including strep, staph, and H. influenzae Signup and view all the answers

What is a potential interaction with erythromycin?

Increased levels with ketoconazole Signup and view all the answers

What is a side effect of IV erythromycin?

Both b and c Signup and view all the answers

What is the primary mechanism of action of Lincosamides?

Inhibiting protein synthesis of the 50S ribosomal subunit Signup and view all the answers

What is a characteristic of azithromycin?

Long half-life, allowing for once-daily dosing for 5 days Signup and view all the answers

What is a potential complication of clindamycin use?

Severe pseudomembranous colitis Signup and view all the answers

What is the primary difference between erythromycin and azithromycin?

Erythromycin has a narrower spectrum of antibacterial activity than azithromycin Signup and view all the answers

What is a characteristic of clindamycin that distinguishes it from erythromycin?

Clindamycin is more effective against anaerobes Signup and view all the answers

What is the primary mechanism of action of fluoroquinolones?

Inhibition of DNA synthesis of topoisomerase II and IV Signup and view all the answers

What is a significant FDA warning regarding the use of fluoroquinolones?

They should only be used if there are no alternative treatments available Signup and view all the answers

What is a specific side effect of fluoroquinolones that is of concern in patients with myasthenia gravis?

Muscle weakness Signup and view all the answers

Which fluoroquinolone is the treatment of choice for anthrax exposure?

Ciprofloxacin Signup and view all the answers

What is a unique consideration for the use of fluoroquinolones in pediatric patients?

They are contraindicated in patients under 18 due to risk of tendon rupture Signup and view all the answers

What is the effect of rifampin on CYP3A4 enzyme activity?

Induction Signup and view all the answers

What is a potential adverse effect of isoniazid?

All of the above Signup and view all the answers

What is the effect of isoniazid on the CYP2D6 enzyme?

Inhibition Signup and view all the answers

What is a characteristic of rifampin that can be observed in a patient's bodily secretions?

Orange color Signup and view all the answers

What is a potential consequence of rifampin use in pregnant women?

Teratogenicity Signup and view all the answers

What is the primary mechanism of action of Metronidazole?

Inhibiting bacterial DNA synthesis Signup and view all the answers

What is the recommended dose of Metronidazole for adults?

500mg-1gm IV Signup and view all the answers

What is a rare adverse effect of Metronidazole?

Seizures Signup and view all the answers

What is the interaction between Metronidazole and EtOH?

EtOH may cause an adverse reaction with Metronidazole Signup and view all the answers

What is the primary indication for using Metronidazole in surgical procedures?

All of the above Signup and view all the answers

What is the primary mechanism of action of tetracyclines?

Inhibition of protein synthesis by binding to 30s ribosomal subunit Signup and view all the answers

What is a significant adverse effect of doxycycline?

Photosensitivity Signup and view all the answers

Why should tetracyclines be avoided in pregnancy?

They can cross the placenta and cause fetal tooth discoloration Signup and view all the answers

What is a significant consideration when administering doxycycline to patients with liver disease?

Dose reduction is necessary to avoid hepatotoxicity Signup and view all the answers

What is a potential consequence of long-term use of tetracyclines in children?

All of the above Signup and view all the answers

What is the primary mechanism of action of sulfonamides in bacterial cells?

Inhibition of folate synthesis Signup and view all the answers

What is the synergistic effect of combining sulfonamides with trimethoprim or pyrimethamine?

Increased inhibition of folate synthesis Signup and view all the answers

What is the significance of sulfonamide metabolism in the liver and excretion in urine?

It increases the risk of nephrotoxicity Signup and view all the answers

What is the primary clinical use of sulfamethoxazole/trimethoprim?

Treatment of GU and respiratory infections Signup and view all the answers

What is the potential complication of using silver sulfadiazine on burns?

Slowed wound healing Signup and view all the answers

What type of antibiotics are known to affect neuromuscular blocking agents?

Aminoglycosides Signup and view all the answers

Which of the following antibiotics is not known to affect neuromuscular blocking agents?

Ceftriaxone Signup and view all the answers

What is the treatment of choice for neuromuscular blocking agents toxicity?

Sugammadex Signup and view all the answers

What is the role of calcium in the treatment of neuromuscular blocking agents toxicity?

May help to reverse the effects of neuromuscular blocking agents Signup and view all the answers

What is the primary mechanism of action of sugammadex?

Reverses the action of neuromuscular blocking agents by binding to the neuromuscular blocking agent itself Signup and view all the answers

Which antibiotic has its absorption decreased by Ca++, Fe++, and Mg++?

Fluoroquinolones Signup and view all the answers

Which drug is potentiated by macrolides, metronidazole, trimethoprim-sulfa, and ciprofloxacin?

Warfarin Signup and view all the answers

What is a characteristic of the interaction between amoxicillin and allopurinol?

Hypersensitivity syndrome is seen, usually with renal impairment Signup and view all the answers

Which drug is accumulated when taken with penicillins, except amoxicillin?

Methotrexate Signup and view all the answers

What is the effect of P450 enzyme inducers on certain drugs?

They increase the elimination of the drug Signup and view all the answers

Study Notes

Wound Classification

Class I/Clean: Uninfected operative wounds with no inflammation, no entry into respiratory, alimentary, genital, or urinary tracts, primarily closed, and drained with closed drainage if necessary.

Clean Wounds Criteria

No penetrating trauma
Meet Class I criteria

Class II/Clean-Contaminated

Operative wounds entering respiratory, alimentary, genital, or urinary tracts under controlled conditions with no unusual contamination
Includes operations on:
- Biliary tract
- Appendix
- Vagina
- Oropharynx
No evidence of infection or major break in sterile technique

Class III/Contaminated

Open, fresh, accidental wounds
Operations with:
- Major breaks in sterile technique (e.g., open cardiac massage)
- Gross spillage from gastrointestinal tract
- Incisions with acute or no purulent inflammation

Class IV/Dirty-Infected

Old traumatic wounds with retained devitalized tissue
Existing clinical infections or perforated viscera
Organisms causing postoperative infection were present in the operative field before the operation

Classification of Operative Wounds

Class I/Clean: Uninfected operative wounds with no inflammation, no entry into respiratory, alimentary, genital, or urinary tracts, primarily closed, and drained with closed drainage if necessary.
Class II/Clean-Contaminated: Operative wounds where respiratory, alimentary, genital, or urinary tracts are entered under controlled conditions, no unusual contamination, and no evidence of infection or major breaks in sterile technique.

Contamination and Infection

Class III/Contaminated: Open, fresh, accidental wounds, major breaks in sterile technique, gross spillage from gastrointestinal tract, and incisions with acute or no purulent inflammation.
Class IV/Dirty-Infected: Old traumatic wounds with devitalized tissue, existing clinical infections, or perforated viscera, implying pre-operative infection in the operative field.

Anesthetic Complications

Bronchospasm

Decreased ETCO2 and SaO2
Increased PIP
Symptoms: Hypotension, Tachycardia, Arrhythmia, and Cardiac arrest

Anaphylaxis Presentation

Skin symptoms: Flushing, Urticaria, Erythema
Severe reaction: Stevens-Johnson Syndrome

Insulin Management

Insulin administration is necessary to maintain glucose levels below 200 mg/dl.
The IV route is preferred in perioperative settings due to unreliable absorption through the subcutaneous (SQ) route in cases of hypothermia, vasoconstriction, and other conditions.
Insulin administration may not be necessary for minor procedures.

Blood Glucose Control

Maintain control of blood glucose levels.
Keep blood glucose levels below 200 mg/dl.
Some sources recommend maintaining blood glucose levels between 140-180 mg/dl for specific procedures, such as CT scans and colorectal surgery.

Adverse Reactions

Stevens-Johnson Syndrome is a potential complication associated with insulin management.

Antibacterial Properties

Thiazolidine ring connected to a Beta-lactam ring, which inhibits cell wall synthesis through transpeptidation reaction.

Pre-Operative Treatment

Used as pre-operative prophylaxis for patients with congenital heart disease or implants (e.g., TKA, THA, heart valves).

Transient Bacteremia

Transient bacteremia often occurs with dental and surgical procedures.

Drug of Choice

Treatment of choice for infections caused by:
- Pneumococcal
- Streptococcal
- Meningococcal

1st Generation Penicillins

Effective against Gram-positive bacteria, but not Gram-negative bacteria due to inability to cross the inner cytoplasmic bilayer.
Examples of 1st generation penicillins include Penicillin G (Pen G), nafcillin, and methicillin.
Penicillin G is unable to cross the inner cytoplasmic bilayer in Gram-negative cells, making it ineffective against these bacteria.
Excretion of 1st generation penicillins occurs primarily through the kidneys, with 90% being excreted through tubular secretion (except for nafcillin).
Caution is advised when using 1st generation penicillins in patients with renal disease, especially those with low urine output.

Penicillin G

Susceptible to Beta-lactamases
High dose of 10 million units equivalent to 16 mEq of potassium (K+)
Use with caution in patients with:
- Renal disease due to nephrotoxicity
- Hyperkalemia

Nafcillin

Resistant to Beta-lactamases
Unpredictable oral absorption, not used orally
Highly protein bound in the bloodstream
Primarily cleared by biliary excretion, no dose adjustment needed in:
- Renal disease

2nd Generation Penicillins

Include ampicillin and amoxicillin, which are bacteriocidal against both gram-positive and gram-negative bacteria
Amoxicillin is absorbed better from the GI tract and has a longer duration of action compared to ampicillin
Ampicillin has high renal excretion
Ampicillin has the highest incidence of rash, often due to the commercial preparation rather than an allergic reaction

Carbenicillin

Effective against organisms resistant to ampicillin
Must be administered intravenously (IV) as it is not absorbed by the gastrointestinal (GI) tract
Combination with probenecid increases plasma concentration by 50%
High sodium content, use with caution in patients with congestive heart failure (CHF)
Interferes with platelet aggregation, leading to increased bleeding time
Platelet count remains normal despite increased bleeding time

Probenecid Mechanism of Action

Inhibits the renal tubular excretion of penicillins
Increases plasma levels of penicillins when paired with them

Interactions with Other Drugs

Inhibits the excretion of acetaminophen
Inhibits the excretion of lorazepam
Inhibits the excretion of ketoprofen
Inhibits the excretion of naproxen
Inhibits the excretion of rifampin

Cephalosporins

Effective against both Gram-negative and Gram-positive bacteria
Mechanism of Action (MOA): inhibit bacterial cell wall synthesis
Inhibited by cephalosporinases, a type of beta-lactamase
Cross-reactivity with penicillins (PCN) due to shared beta-lactam ring structure (rare)
Rare incidence of anaphylaxis reaction: approximately 0.02%
Can cause thrombophlebitis as a side effect
May produce a positive Coombs' test, but hemolysis is rare
Inexpensive and suitable for various procedures:
- Cardiovascular (CV)
- Orthopedic (ortho)
- Biliary
- Pelvic
- Intraabdominal

1st Generation Cephalosporins

Cefazolin (Ancef) is the most widely used antibiotic in surgery.
Dosage for Cefazolin:
- Adults: 1-2 gm IV for 50-120 kg, 3 gm IV if > 120 kg.
- Pediatrics: 15-30 mg/kg IV.
Re-dosing guidelines for Cefazolin:
- Re-dose after 3-4 hours.
- Re-dose after significant blood loss (1500 cc).
- Maximum dose: 6gmin24hours.
Important note: Do not use Cefazolin if allergic to Cephalexin (Keflex).
Cephalexin (Keflex) is an oral antibiotic.

2nd Generation Cephalosporins

Cefuroxime (Ceftin) is effective in treating meningitis and can cross into cerebrospinal fluid (CSF).
Cefuroxime is effective against Haemophilus influenzae.
Cefoxitin is resistant to cephalosporinases produced by gram-negative bacteria.
Cefoxitin is useful for treating gram-negative bacterial infections.

Carbapenems

Examples: Ertapenem, Imipenem, Meropenem
High levels of Imipenem can cause seizures, especially in patients with renal failure
Effective against Enterobacter infections due to resistance to beta-lactamases
Excretion occurs through the kidneys, requiring dosage adjustment in renal failure cases

Aztreonam

Monocyclic beta-lactam ring structure
Penetrates the Central Spinal Fluid (CSF)
Suitable alternative for patients allergic to Penicillin (PCN) for pneumonia, meningitis, and sepsis caused by Gram-negative bacteria
Disadvantage: Can cause Enterococcal superinfections
Relatively expensive antibiotic

Aminoglycosides

Aminoglycosides provide gram negative coverage and exhibit a synergistic effect when used in combination with other antimicrobials.
Examples of aminoglycosides include gentamicin, streptomycin (limited use today), amikacin, and neomycin.

Precautions and Interactions

Amikacin should not be used with PCNs as it may antagonize PCN against enterococcus faecalis.

Neomycin

Neomycin is used topically and orally, but does not undergo systemic absorption.
It is useful orally to decrease bacterial flora prior to GI surgery.
Neomycin is extremely nephrotoxic and should not be given IV.
It may prolong NMB (neuromuscular blockade).

Adverse Effects

Renal Disease

Renal disease can increase the elimination half-life of aminoglycosides by 20-40 fold.

Ototoxicity

Aminoglycosides can cause ototoxicity, which is accentuated by furosemide and mannitol.

Nephrotoxicity

Aminoglycosides can cause renal tubular necrosis, which is usually reversible when discontinued.

Skeletal Muscle Weakness

Aminoglycosides can decrease the prejunctional release and sensitivity to ACh at the postsynaptic junction.
Calcium administration can decrease this effect.
Use with caution in patients with myasthenia gravis, as aminoglycosides can potentiate NMB.

Gentamycin

Penetrates pleural, ascitic, and synovial fluids, but only when they are inflamed
Plasma levels must be monitored to guide dosage adjustments
Side effects are directly related to plasma concentration levels, so dosage should be decreased in patients with renal disease

Side Effects

Ototoxicity can cause nystagmus, vertigo, nausea, tinnitus, and pressure in the ears
Deafness can develop suddenly, highlighting the importance of monitoring plasma levels

Glycopeptides: Vancomycin

Inhibits cell wall synthesis, effective against Gram-positive bacteria
Treatment of choice for:
- MRSA
- Severe staphylococcal infections
- Streptococcal or enterococcal endocarditis (if penicillin or cephalosporin allergy)

Pharmacology

Dosage: 10-15 mg/kg IV over 60-120 minutes
Dosing frequency: every 12 hours
Renal considerations: dose reduction necessary in renal disease
Excretion: 90% unchanged in urine via kidneys

Monitoring and Interactions

Lab monitoring necessary to prevent:
- Ototoxicity
- Nephrotoxicity (especially with concurrent aminoglycosides)
Interaction: may potentiate succinylcholine NMB

Vancomycin Contraindications

Arterial hypoxemia is a possible complication, characterized by an unexpected decrease in SpO2
Drug-induced ventilation/perfusion mismatch can occur
Rapid infusion can lead to "Red Man Syndrome", which requires decreasing the infusion rate if flushing or other symptoms occur

Red Man Syndrome

Caused by massive histamine release
Symptoms include:
- Hypotension
- Facial and truncal flushing
- Cardiac Arrest
May be treated with diphenhydramine (1mg/kg) or cimetidine (4mg/kg) 1 hour preoperatively

Oxazolidinones

Linezolid is a type of oxazolidinone that inhibits bacterial protein synthesis by binding to the 50S ribosomal unit
Has similar coverage to vancomycin
100% bioavailable, making it suitable for oral use
Has a lower incidence of Red Man syndrome compared to vancomycin

Side Effects of Linezolid

Short-term effects:
- Nausea
- Hypoglycemia
Long-term effects:
- Bone marrow suppression
- Peripheral and ocular neuropathy
- Serotonin syndrome (if used with SSRIs)

Macrolides

Macrolides include erythromycin and azithromycin (Z-pack)
Effective against Gram-positive bacteria, including strep, staph, H. influenzae, and chlamydia

Azithromycin

Long half-life: active 4-7 days after last dose
Oral dosing: once/day for 5 days

Erythromycin

Advantage: useful alternative to penicillins (PCN) and cephalosporins
Disadvantages:
- Gastrointestinal (GI) upset (severe nausea and vomiting)
- Thrombophlebitis and tinnitus with IV form
- Prolonged QT interval (torsades de pointes)
Metabolism: via CYP3A4 and CYP1A2
Interactions:
- Increased levels with ketoconazole (CYP3A4 inhibitor)
- Increased ventricular irritability with increased concentrations
- Inhibits P450 enzyme, prolonging metabolism of concurrently used drugs

Macrolides

Erythromycin and azithromycin (Z-pack) are used to treat Gram-positive bacteria such as strep, staph, H. influenzae, and chlamydia
Azithromycin has a long half-life, remaining active for 4-7 days after the last dose
Oral dosing for azithromycin involves taking the medication once a day for 5 days

Lincosamides

Clindamycin and lincomycin inhibit protein synthesis of the 50S ribosomal subunit
These antibiotics are metabolized to inactive compounds
The dose of clindamycin and lincomycin should be decreased in severe liver disease

Clindamycin

Clindamycin is similar to erythromycin but covers more anaerobes
It can cause skeletal muscle weakness due to prejunctional and postjunctional effects on the neuromuscular junction (NMJ)
Large doses of clindamycin can cause significant and prolonged neuromuscular blockade (NMB)
Clindamycin-induced NMB is not readily antagonized by calcium and anticholinesterase drugs
Clindamycin has several disadvantages, including toxicity, and should only be used if other agents have failed
It can cause severe pseudomembranous colitis, and should be discontinued if the patient experiences significant diarrhea

Fluoroquinolones

Effective against Gram-negative and Gram-positive bacteria
Effective for treatment of Gastrointestinal (GI) and Genitourinary (GU) infections
Mechanism of Action (MOA): inhibits DNA synthesis by targeting topoisomerase II and IV, preventing bacterial replication
Excreted by the kidneys
FDA warning: use only when alternative treatments are not available

Side Effects

Peripheral neuropathy
Psychosis
Gastrointestinal symptoms: nausea, vomiting, and diarrhea
Dizziness and insomnia
Increased risk of tendonitis and tendon rupture
Muscle weakness in myasthenia gravis (MG)

Important Contraindications

Not recommended for routine use in patients under 18 years old due to risk of cartilage damage and arthropathy

Specific Fluoroquinolones

Ciprofloxacin

Useful for many systemic infections
Treatment of choice for anthrax exposure
Can be used to treat tuberculosis (TB)

Levofloxacin

Used in genitourinary (GU) procedures

Moxifloxacin

Use only when no other options are available
Additional side effects: SIADH (Syndrome of Inappropriate Antidiuretic Hormone), liver failure, QT prolongation, and psychotic reactions

Antimycobacterials

Used to treat tuberculosis

Isoniazid

Inhibits CYP2D6 enzyme
Can cause:
- Drug-induced lupus
- Hepatitis
- CNS toxicity

Rifampin

Induces CYP3A4 enzyme (and others)
Interacts with medications, such as:
- Methadone
- Anticoagulants
- Anticonvulsants
- Benzodiazepines
Causes harmless orange coloration of:
- Urine
- Sweat
- Tears
Adverse effects:
- Rash
- Thrombocytopenia
- Nephritis
Teratogenicity

Nitroimidazole Antimicrobials

Effective against anaerobic gram-negative bacilli and Clostridium
Metronidazole is a key antimicrobial in this class

Metronidazole

Inhibits bacterial DNA
Dosage:
- IV: 500mg-1gm (30 mg/kg/d)
- Can also be used orally
Indications:
- Colorectal, GYN, and ENT procedures
Metabolism and excretion:
- Metabolized in the liver
- Excreted in urine
Uses:
- Treats non-severe C. diff cases (alternative to vancomycin)
- Can be combined with vancomycin to treat severe C. diff cases

Metronidazole Side Effects and Interactions

Common side effects:
- Dry mouth
- Headache
- Metallic taste
- Nausea
Rare but serious adverse effects:
- Pancreatitis
- CNS effects (ataxia, encephalopathy, seizures)
Drug interactions:
- Potentiates coumadin-like anticoagulants
- Phenytoin and phenobarbital accelerate clearance
- Cimetidine may prolong clearance
- Increases risk of Lithium toxicity
- EtOH may cause adverse reactions

Tetracyclines

Mechanism of action: prevents bacterial protein synthesis by binding to 30S ribosomal subunit
Doxycycline: notable exception in terms of excretion, not renally excreted

Adverse Effects

Gastrointestinal: nausea, vomiting, diarrhea
Dermatological: photosensitivity
Obstetric: contraindicated in pregnancy due to ability to cross placenta
Teratogenic effects: can cause tooth discoloration, dysplasia, and impaired bone growth in the fetus
Hepatotoxic and nephrotoxic: can cause liver and renal toxicity

Sulfonamides

Inhibit folate synthesis in bacterial cells, which is why they're often combined with trimethoprim or pyrimethamine for a synergistic effect.
Metabolized in the liver and excreted in the urine.
Can precipitate in acid pH urine.

Adverse Reactions

Fever
Rash
Stevens-Johnson syndrome
Nausea and vomiting
Diarrhea
Photosensitivity
Hematopoietic disturbances

Sulfonamides in Clinical Use

Sulfamethoxazole/trimethoprim is used to treat:
- Genitourinary (GU) infections
- Respiratory infections
Increasing resistance to E. coli
Trimethoprim:
- Inhibits creatinine secretion without affecting GFR (can be distinguished from sulfonamide nephrotoxicity)

Topical Sulfonamides

Silver sulfadiazine:
- Used to prevent infection in burns
- May slow wound healing

Other Sulfur-Containing Drugs

Diuretics
Diazoxide
Sulfonylurea hypoglycemic agents
Low risk of cross-sensitivity with allergic reactions

Drug Interactions with Antimicrobials

Methotrexate accumulation is seen with penicillins, except amoxicillin, which does not cause accumulation.

Interactions with Specific Medications

Allopurinol can cause hypersensitivity syndrome when taken with amoxicillin, especially in individuals with renal impairment.

Warfarin Interactions

Warfarin's effects are potentiated by certain antimicrobials, including macrolides, metronidazole, trimethoprim-sulfa, and ciprofloxacin.

Fluoroquinolone Interactions

Fluoroquinolone absorption is decreased by Ca++, Fe++, and Mg++, as well as by carafate, which reduces their concentration.

Enzyme Inducers

Phenytoin and phenobarbital are P450 enzyme inducers.

Wound Classifications

Class I/Clean: uninfected operative wounds with no inflammation, respiratory, alimentary, genital, or urinary tract entry, and primarily closed and drained with closed drainage.
Class II/Clean-Contaminated: operative wounds with entry into respiratory, alimentary, genital, or urinary tracts under controlled conditions with no unusual contamination.
Class III/Contaminated: open, fresh, accidental wounds, or operations with major breaks in sterile technique, gross spillage, or acute inflammation.
Class IV/Dirty-Infected: old traumatic wounds with retained devitalized tissue, existing clinical infection, or perforated viscera.

Anaphylaxis Presentation

Flushing
Urticaria
Erythema
Stevens-Johnson Syndrome

Insulin

Maintain glucose levels below 200 mg/dl
IV route is best in perioperative period
Not always necessary for minor procedures

Beta-Lactams

Inhibit cell wall synthesis (transpeptidation reaction)
Preoperative treatment for patients with congenital heart disease or implants
1st Generation Penicillins:
Pen G: unable to cross inner cytoplasmic bilayer in gram-negative cells, destroys gram-positive cells
Nafcillin: resistant to beta-lactamases, high protein binding, cleared by biliary excretion
2nd Generation Penicillins:
Ampicillin and amoxicillin: bacteriocidal against gram-positive and negative bacteria
Amoxicillin: better absorbed from the GI tract, longer acting than ampicillin
Carbenicillin: useful for organisms resistant to ampicillin

Cephalosporins

Inhibit bacterial cell wall synthesis
Inhibited by cephalosporinases (beta-lactamases)
Cross-reactivity with PCN due to shared beta-lactam ring (rare)
Anaphylaxis reaction very low (-0.02%)
1st Generation Cephalosporins:
Cefazolin (Ancef): most widely used antibiotic in surgery
Cephalexin (Keflex): oral, do not use cefazolin if allergic to cephalexin
2nd Generation Cephalosporins:
Cefuroxime (Ceftin): effective in meningitis treatment, crosses into CSF
Cefoxitin: resistant to cephalosporinases produced by gram-negative bacteria

Other Beta-Lactams

Carbapenems: ertapenem, imipenem, meropenem
Aztreonam: monocyclic beta-lactam ring, penetrates CSF, used for pneumonia, meningitis, and sepsis from gram-negative bacteria

Aminoglycosides

Gram-negative coverage
Synergistic effect when used in combination with other antimicrobials
Gentamicin, streptomycin, amikacin, neomycin

Glycopeptides

Vancomycin: inhibits cell wall synthesis, gram-positive bacteria, treatment of choice for MRSA

Oxazolidinones

Linezolid: inhibits bacterial protein synthesis, similar coverage as vancomycin, short-term effects: nausea and hypoglycemia

Macrolides

Erythromycin and azithromycin (Z-pack): gram-positive bacteria, strep, staph, H.influenzae, chlamydia
Azithromycin: long half-life, active 4-7 days after last dose

Lincosamides

Clindamycin and lincomycin: inhibit protein synthesis of the 50S ribosomal subunit

Fluoroquinolones

Gram-negative and positive bacteria
Effective for GI and GU infections
MOA: inhibit DNA synthesis of topoisomerase II and IV
Excreted by kidneys

Antimycobacterials

Isoniazid: CYP2D6 enzyme inhibitor, can cause drug-induced lupus and hepatitis
Rifampin: CYP3A4 enzyme inducer, harmless orange color to urine, sweat, and tears

Nitroimidazole Antimicrobials

Metronidazole: inhibits bacterial DNA, useful for colorectal, GYN, and ENT procedures

Tetracyclines

Prevents bacterial protein synthesis by binding to 30s ribosomal subunit
Doxycycline: not renally excreted, adverse effects: N/V, diarrhea, photosensitive

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Questions and Answers

What is the primary characteristic of a Class I/Clean operative wound?

Which of the following operations would be classified as a Class II/Clean-Contaminated wound?

What is a characteristic of a Class III/Contaminated wound?

Which of the following would be classified as a Class IV/Dirty-Infected wound?

What is the main difference between Class III/Contaminated and Class IV/Dirty-Infected wounds?

What is implied by the definition of Class IV/Dirty-Infected wounds?

What are the consequences of bronchospasm?

What is a severe skin and mucous membrane disorder?

What is the primary goal of insulin administration in perioperative patients?

Why is the IV route preferred over the subcutaneous route for insulin administration in perioperative patients?

In which type of surgical procedures may insulin administration not be necessary?

What is the recommended blood glucose range for patients undergoing CT or colorectal surgery?

What is a potential complication of uncontrolled blood glucose levels in perioperative patients?

What is the specific reaction inhibited by thiazolidine connected to a Beta-lactam ring?

What is a limitation of Pen G in terms of its ability to target bacterial cells?

What is the primary mechanism by which 1st generation penicillins are eliminated from the body?

Why should caution be exercised when administering 1st generation penicillins to patients with renal disease?

Which of the following 1st generation penicillins is NOT rapidly excreted by the kidneys?

What is the spectrum of antibacterial activity of 1st generation penicillins?

What is a characteristic of Pen G that increases its susceptibility to degradation?

Why is Nafcillin not used orally?

What is a precaution that should be taken when administering Pen G to patients with renal disease?

How is Nafcillin primarily eliminated from the body?

What is the significance of the 10 million units of Pen G being equal to 16 mEq of K+?

What is a characteristic of amoxicillin that distinguishes it from ampicillin?

What is a potential side effect of 2nd generation penicillins?

Which of the following 2nd generation penicillins is longer acting?

What is a characteristic of 2nd generation penicillins?

What is a unique consideration when administering carbenicillin to patients with congestive heart failure?

What is the effect of probenecid on plasma carbenicillin concentration?

Why is carbenicillin typically administered intravenously?

What is the effect of carbenicillin on platelet function?

What is a characteristic of carbenicillin that distinguishes it from ampicillin?

What is the effect of probenecid on the elimination of certain drugs?

Which of the following drugs is NOT affected by probenecid's inhibitory effect on renal tubular excretion?

What is the purpose of pairing probenecid with penicillins?

Which of the following drug's effects are likely to be weakened with concurrent administration of probenecid?

What is the mechanism by which probenecid increases the plasma levels of penicillins?

What is the mechanism of action of cephalosporins?

What is a common characteristic of cephalosporins that leads to cross-reactivity with penicillins?

What is a potential complication of cephalosporin use?

What is a characteristic of cephalosporins that makes them suitable for use in certain surgical procedures?

What is the recommended dose of Cefazolin for adults weighing over 120 kg?

What is the primary reason Cefazolin should not be used in patients with an allergy to Cephalexin?

What is the recommended re-dosing schedule for Cefazolin in surgical procedures?

What is the maximum dose of Cefazolin recommended in a 24-hour period?

What is the recommended pediatric dose of Cefazolin?

What is a characteristic of Cefuroxime that makes it effective in the treatment of meningitis?

What is the primary advantage of Cefoxitin over other cephalosporins?

What is the primary advantage of using Cefuroxime over other antibiotics in treating meningitis?

What is the primary indication for using Cefoxitin?

What is the primary concern when using high levels of imipenem?

Why is aztreonam suitable for patients with an allergy to PCN?

What is a disadvantage of aztreonam?

What is a characteristic of neomycin that makes it useful in certain surgical procedures?

What is the consequence of combining amikacin with PCNs in the treatment of enterococcus faecalis?

What is the effect of aminoglycosides on the neuromuscular junction?

Why should caution be exercised when administering aminoglycosides to patients with renal disease?

What is the effect of calcium administration on the skeletal muscle weakness caused by aminoglycosides?

What is a unique characteristic of gentamicin in relation to bodily fluids?

Why is it essential to monitor plasma levels of gentamicin?

What is a potential side effect of gentamicin that can present suddenly?

What is a common symptom of gentamicin-induced ototoxicity?

What should be done to the dosage of gentamicin in patients with renal disease?

What is the primary mechanism of action of Vancomycin?

What is the primary indication for the use of Vancomycin in the treatment of bacterial infections?

What is the recommended dosage of Vancomycin in patients with normal renal function?

What are/is the primary side effects to consider when administering Vancomycin?

What is the recommended laboratory monitoring for patients receiving Vancomycin therapy?

What is the primary mechanism of action of Linezolid?

What is a potential short-term effect of Linezolid?

What is a characteristic of Vancomycin that can be treated with diphenhydramine?

What is a long-term effect of Linezolid?

What is a characteristic that distinguishes Linezolid from Vancomycin?

What is a characteristic of azithromycin?

What is a disadvantage of erythromycin?