Exam 4 review - Surgical Site Infections (SSIs)

Surgical Site Infections (SSIs)

• SSIs are a substantial concern, ranking as the most common perioperative infection and a frequent cause of hospital readmission.
• A multimodal strategy can significantly lower postoperative infection risks, involving double gloving, intraoperative hand hygiene, patient screening and decolonization, and environmental equipment decontamination.
• Immunosuppressed patients, common in chemotherapy, necessitate strict aseptic techniques and may require prophylactic antibiotics.
• Anesthesia providers should employ measures to minimize bacterial transmission during anesthetic administration.
• Prophylactic antibiotics should target the most likely organism without broad coverage to reduce drug resistance.
• Antibiotic prophylaxis should prevent SSI, reduce related morbidity and mortality, lower healthcare costs and duration, avoid adverse effects, and minimize impact on microbial flora.
• Effective antibiotic prophylaxis requires agents active against likely pathogens, administered at the correct dosage and time for adequate concentrations during potential contamination, with safety and the shortest effective duration.
• Preoperative antibiotic prophylaxis should ideally occur within 60 minutes before skin incision; vancomycin and fluoroquinolones should start within two hours.
• Prophylactic antibiotics should stop within 24 hours after surgery completion.
• Anaphylactic reactions, like laryngeal edema or cardiovascular collapse, and delayed reactions, like maculopapular rash, are potential manifestations of drug allergies like beta-lactam hypersensitivity.
• Chemotherapy patients may experience mucous membrane inflammation, necessitating caution with airway devices.

Antibiotic Mechanisms of Action (MOAs)

• Beta-Lactams (Penicillins and Cephalosporins) interfere with peptidoglycan synthesis by inhibiting penicillin-binding proteins, leading to cell wall destruction.
• Penicillins (e.g., Penicillin G, Ampicillin, Piperacillin) bind to penicillin-binding proteins, inhibiting bacterial cell wall synthesis, often combined with beta-lactamase inhibitors (e.g., clavulanic acid) to overcome bacterial resistance.
• Cephalosporins (e.g., Cefazolin, Ceftriaxone) inhibit peptidoglycan synthesis by binding to penicillin-binding proteins; cefazolin is commonly used for surgical prophylaxis.
• Aminoglycosides (e.g., Gentamicin, Tobramycin) bind to the 30S ribosomal subunit, disrupting protein synthesis during mRNA translation.
• Macrolides (e.g., Erythromycin, Azithromycin) bind to the 50S ribosomal subunit, interfering with protein synthesis.
• Lincosamides (e.g., Clindamycin) bind to the 50S ribosomal subunit, inhibiting peptide chain synthesis.
• Glycopeptides (e.g., Vancomycin) bind tightly to the cell wall precursor, blocking glycopeptide formation and inhibiting cell wall synthesis.
• Nitroimidazoles (e.g., Metronidazole) are metabolized to cytotoxic particles that break down bacterial DNA.
• Fluoroquinolones (e.g., Ciprofloxacin, Levofloxacin) inhibit bacterial topoisomerases, preventing DNA uncoiling and causing DNA strand breakage.

Respiratory Anesthetic Considerations

• A detailed respiratory system evaluation is essential due to the frequency of complications associated with respiratory disease.
• Knowledge of airway anatomy is essential; airway adjuncts should be readily available during airway management.
• Exercise caution with sedative medications in patients with respiratory issues due to potential hypersensitivity.
• Preoperative sedation should be judicious in patients with obstructive sleep apnea, along with continuous oximetry monitoring.
• For intubation in patients with obstructive sleep apnea, ramp the upper body and anticipate a difficult airway, keeping a videolaryngoscope or other airway adjuncts nearby.
• For general anesthesia in patients with obstructive sleep apnea, use short-acting agents, limit long-acting opioids, minimize muscle relaxants, and provide PEEP to reduce postoperative atelectasis.
• Consider regional anesthesia when possible in patients with obstructive sleep apnea.
• Avoid increases in pulmonary vascular resistance (PVR) by preventing hypoxemia, hypercarbia, acidosis, pain, and hypothermia.
• For asthma patients, review their medications, symptom frequency, recent hospitalizations, and triggers; continue current medications and monitor for cardiac arrhythmias and other bronchodilator adverse reactions.
• Patients treated with bleomycin may face postoperative respiratory failure risk, necessitating minimized crystalloid administration (consider colloids) and lower inhaled oxygen concentrations (below 30% if possible) while maintaining O2 saturation over 90%.
• Recognizing risk factors and decreasing the overall risk (including avoiding general anesthesia if possible) are important steps in preventing aspiration pneumonitis.

Pathophysiology of Respiratory Disorders

• Asthma is characterized by airway inflammation, hyperirritability, bronchoconstriction, and airway remodeling, resulting in decreased airway diameter, increased resistance, and decreased airflow.
• Chronic Obstructive Pulmonary Disease (COPD) is characterized by expiratory airflow limitation, including emphysema and chronic bronchitis, leading to bronchiolar inflammation, fibrosis, narrowing of airways, alveolar destruction, and reduced elastic recoil.
• Pulmonary Embolism (PE) occurs when a thrombus lodges in the pulmonary vasculature, with risk factors including venous stasis, hypercoagulability, and endothelial injury.
• Aspiration Pneumonitis, chemical aspiration poses the greatest difficulty.

Mechanisms of Action of Respiratory and Pulmonary Vascular Disorder Drugs

• Beta-2 Adrenergic Agonists (e.g., Albuterol, Salmeterol) increase cAMP in smooth muscle, decreasing myosin light chain kinase activity, resulting in bronchodilation.
• Muscarinic Antagonists (Anticholinergics) (e.g., Ipratropium, Tiotropium) block acetylcholine binding to M3 receptors in the airways, reducing bronchoconstriction and mucus secretion.
• Corticosteroids (e.g., Fluticasone, Prednisone) form a complex with glucocorticoid receptors, altering the genetic expression of pro-inflammatory mediators and reducing airway inflammation.
• Leukotriene Modifiers (e.g., Montelukast, Zileuton) reduce bronchoconstriction, mucus production, and inflammation by blocking leukotriene receptors or inhibiting leukotriene production.
• Methylxanthines (e.g., Theophylline) increase cAMP and block adenosine receptors, leading to smooth muscle relaxation and reduced bronchoconstriction.
• High FiO2 can support pulmonary vasodilation in the context of pulmonary embolism management.

Tocolytics - Medications for Preterm Labor Delay

• Tocolysis is an obstetrical procedure that utilizes medications to delay delivery in the presence of preterm labor.
• Tocolytics weaken uterine contractions to quiet the uterus.
• Tocolysis delays pregnancy for fetal lung maturity and possible transfer to a higher acuity facility.
• The typical indication for tocolysis is for patients under 34 weeks of gestation.
• Tocolytics assist external cephalic versions, uterine tachysystole management, and fetal distress cases.
• Many tocolytic medications are used off-label for preterm labor.
• Common tocolytic agents include Beta Agonists (e.g., Terbutaline), Magnesium Sulfate, Calcium Channel Blockers (e.g., Nifedipine), Oxytocin Antagonists (e.g., Atosiban), and Cyclooxygenase Inhibitors (NSAIDs) (e.g., Indomethacin).

Tocolytic MOAs (Mechanisms of Action)

• Beta Agonists (e.g., Terbutaline) stimulates Beta-2 adrenergic receptors promote relaxation of uterine smooth muscle.
• Magnesium Sulfate relaxes uterine smooth muscle with a rapid onset and lasts about 30 minutes via continuous infusion.
• Calcium Channel Blockers (e.g., Nifedipine) Causes are potentially through inhibition or antagonism of calcium.
• Oxytocin Antagonists (e.g., Atosiban) Act as a competitive inhibitor of oxytocin, blocking its binding to receptors and preventing the downstream effects that lead to uterine contraction.
• Cyclooxygenase Inhibitors (NSAIDs) (e.g., Indomethacin) inhibits cyclooxygenase, reducing prostaglandin synthesis, which can lead to decreased uterine contractility and risks.

Important Tocolytic Contraindications

• Intrauterine fetal demise
• Non-reassuring fetal status
• Severe preeclampsia or eclampsia
• Maternal hemorrhage
• Premature rupture of membranes

Intro to Surgical Site Infection (SSI)

• SSI has a prevalence of 2-4%
• Accounts for 20% of HAIs
• SSI increases the length of hospital stay by 7-10 days, lead to a 5 times higher readmission rate
• SSI can increase mortality 2-11 times.
• SSI costs are greater than $20,000 per admission, and 60% are preventable.
• Pathogenesis of SSI involves intraoperative contamination, foreign bodies, adhesive matrix, endotoxin, and both endogenous and exogenous risks.

Multimodal Approach to Infection Prevention

• Approach includes preoperative screening, decolonization, and targeted prophylaxis.
• Includes, hair removal, antibiotic prophylaxis, proper blood glucose, and skin preparation.

Perioperative Antibiotics

• Administered within 60 minutes of the incision.
  • Cefazolin (Ancef, Kefzol)
    • Usual adult dose is 2 g IV.
      • For patients who weigh ≥120 kg, the recommended dose is 3 g IV.
      • Repeat dose approximately every 4 hours until closure.
      • Primarily beneficial for Gram positive organisms.
  • Clindamycin (Cleocin)
    • Surgical prophylaxis dosing for adults is 900 mg IV.
    • Administer within 60 min of incision.
    • Re-dose approximately every 6 hours from the initiation of the preoperative dose for procedures exceeding 2 half-lives of the drug.
    • IV incompatibility with barbiturates, calcium gluconate, and many other antibiotics.
    • Adverse effects include neuromuscular blockade, diarrhea, and thrombophlebitis.
  • Vancomycin (Vancocin)
    • Start within 60 – 120 min of incision.
    • Infuse over at least 60 min to minimize histamine release and hypotension (HOTN).
    • Red man syndrome that requires treatment with diphenhydramine
  • Metronidazole (Flagyl -Surgical prophylaxis dosing often involves combination with other antibiotics for colorectal procedures.
  • Cefepime (Maxipime)
    • Dose 2 g IV every 12 hours. - Adverse effects include superinfection, hypersensitivity, increased INR (prolonged tx), and neurotoxicity.
  • Ceftriaxone and Cefotaxime
    • Used to treat meningitis due to their ability to achieve therapeutic levels in the CSF. Perioperative Antibiotics - Surgical Skin Preparation

Surgical Skin Preparation

• Three antiseptic solutions used for surgical preparation include Chlorhexidine, Povidone Iodine, and Iodine.
• Iodine is an antiseptic wound disinfectant.
• Corneal risk exists, and rarely, allergic skin reactions can occur.

Beta-Lactam Cross-Reactivity

• All beta-lactams share a common nucleus.
  • PCN risks increase with another PCN medication

General Concepts

• Antibiotics generally target bacterial cell wall synthesis, protein synthesis, RNA synthesis, DNA synthesis, or intermediary metabolism.