clinical use of antibiotics

2. CLINICAL USE OF ANTIBIOTICS Prophylactic therapy : Given to patients before contamination or infection has occurred Anticipatory therapy : Includes situations where contamination has already occurred and therapy is aimed at minimizing post-op infection Empiric therapy : Non-directed therapy in absence of pathogen identification Directed therapy : Pathogen identified

3. Surgery associated infection Approximately 60% of patients admitted to the hospital are "surgericed" at some point during their stay in hospital Incidence: Depends upon type of surgery, patient risk factors & hospital antimicrobial practices Estimated to account for up to 70% of nosocomial infections

4. Factors Associated with Increased Risk of Surgical Infection

6. Clean--nontraumatic, uninfected wound; respiratory, gastrointestinal, genitourinary tract or oropharyngeal cavity not entered; elective, primarily closed, undrained wound Clean-contaminated--respiratory, gastrointestinal, genitourinary tract or oropharyngeal cavity entered without unusual contamination and under controlled conditions; mechanically drained wound Contaminated--open, fresh traumatic wounds; gross spillage from gastrointestinal tract; major break in sterile technique; acute, nonpurulent inflammation Dirty/Infected--old traumatic wounds; clinical infection; perforated viscera

9. ANTIBIOTIC PROPHYLAXIS Antibiotic prophylaxis is the peri-operative and/or intra-operative administration of antibiotics to patients to reduce the risk of postoperative infection

10. Antibiotic Prophylaxis Goals The aim of prophylaxis is to augment host defense mechanisms at the time of bacterial invasion, thereby decreasing the size of the inoculum Use antibiotics in a manner that is supported by evidence of effectiveness The use of prophylactic antibiotics is an adjunct to and not a substitute for good surgical technique.

11. Antibiotic Prophylaxis Benefits Decreased incidence of infection (wound/distal) Reduce overall costs - Prolonged stay Risks Toxic reactions Allergic reactions Emergence of resistant bacteria Drug interactions Super infection

12. The 6 laws of prophylactic antibiotic administrationIn prevention of surgical infection

13. Law #1

14. Don't start too early, don't start too late Tissue levels should peak when the knife goes in Law # 2

15. Effect of timing of Prophylactic Antibioticon the infection rate 2847 patients undergoing elective clean or clean-contaminated surgical procedures. Patients divided into 4 categories based upon timing of administration of antibiotic Early 2-24 hours before surgery Pre-operatively 0-2 hours before surgery Perioperative 0-3 hours after surgery Post-operative 3-24 hours after surgery

16. Law # 3 Give the right antibiotic An appropriate prophylactic antibiotic should : (1) Be effective against microorganisms anticipated to cause infection. (2) Need not eradicate every potential pathogen. (3) Achieve adequate local tissue levels. (4) Cause minimal side effects. (5) Be relatively inexpensive. (6) Have no adverse effect on the microbial flora of the patient or hospital.

17. Third-generation cephalosporins (Cefotaxime, Ceftriaxone, Cefoperazone, Ceftazidime or Ceftizoxime) �Fourth-generation cephalosporins: e.g. cefepime Why : Expense Some are less active than 1ST generation against staphylococci �Non-optimal spectrum of action (activity against organisms not commonly encountered in elective surgery) �Widespread use for prophylaxis encourages emergence of resistance

18. Law # 4 give the drug intravenously as oral absorption may be unreliable The effective dose should be governed by the patient's weight. e.g Cephalosporin (Cefazolin) <= 70 kg: 1 g >70 kg: 2 g

19. Law #5 Use additional intra-operative dose only when necessary: * long procedures (> 2-3 hours) * high blood loss (cardiac, liver procedures)

20. Law #6 Keep post-operative doses to a minimum: * 0 doses adequate for most procedures * Further doses Up to 48 hours for selected procedures

22. Endogenous Pathogens Commonly Isolated from Postoperative Pelvic Infections Aerobic gram-positive cocci -�Viridans and nongroup A, B, and D streptococci -�Group B streptococci -�Enterococcus strept faecalis,��Staphylococcus aureus - Staphylococcus epidermidis Aerobic gram-negative bacilli - Escherichia coli - Klebsiella species - Proteus mirabilis - Gardnerella vaginalis

23. Observations in Obgyn surgical infections Febrile morbidity is more common after abdominal than after vaginal hysterectomy Age has inconsistently been shown to be a risk factor after hysterectomy, with premenopausal women shown to be at increased risk in some studies, especially after vaginal hysterectomy

24. Observations in Obgyn surgical infections Bacterial vaginosis has been associated with an increased risk of infection after abdominal hysterectomy Patients scheduled for elective hysterectomy should be screened for bacterial vaginosis; one month before the planned procedure. Those found to have bacterial vaginosis should be treated and allowed several weeks to reestablish a normal lactobacillus-dominant flora before surgery

27. ANTIBIOTIC PROPHYLAXIS IN GYNAECOLOGICALSURGERY Clean Procedures : Antibiotic prophylaxis is considered optional for most clean procedures, although it may be indicated for certain patients that fulfill specific risk criteria Rationale: Likely infecting organism are gram-positive cocci (S. aureus or S. epidermidis) and aerobic coliforms (E. coli). Agents: Cefazolin, cefuroxime, augmentin or metronidazole.

28. ANTIBIOTIC PROPHYLAXIS IN GYNAECOLOGICALSURGERY Vaginal/abdominal hysterectomy : . Augmentin 1.2 g single dose . Cefazolin 1 - 2 g single dose � Metronidazole 500 mg IV single dose . Cefuroxime 1.5 g IV single dose � Metronidazole 500 mg IV single dose Laparotomy : In high risk patients Laparoscopy : None Hysteroscopy : None

29. ANTIBIOTIC PROPHYLAXIS IN GYNAECOLOGICALSURGERY Infertility promoting surgery : . Augmentin 1.2 g single dose . Cefazolin 1 - 2 g or Cefuroxime 1.5 g IV single dose � Metronidazole 500 mg IV single dose . In salpingostomy for hydrosalpinx; extend prophylaxis up to one week (doxycycline + metronidazole OR Augmentin)

30. ANTIBIOTIC PROPHYLAXIS IN GYNAECOLOGICALSURGERY D&C: missed abortion or induced abortion with risk factors, (e.g. history of previous PID, multiple partners, young, known gonococcal or chlamydia infections) 200 mg Doxycycline one hour before, followed by 100 mg x 2 daily x 4 days IUCD insertion and HSG with risk factors : Prohylaxis is probably indicated - Doxycycline as above

31. ANTIBIOTIC PROPHYLAXIS IN OBSTETRIC AND GYNAECOLOGICALSURGERY Penicillin/Cephalosporin allergy Clindamycin, IV, 150 mg 6 hourly for 2�3 doses may be used for such patients

32. High-risk patients Ampicillin, 2 g IM or IV, plus gentamicin, 1.5 mg/ kg (not to exceed 120 mg) within 30 minutes of starting the procedure; six hours later, ampicillin, 1 g IM/IV, or amoxicillin, 1 g orally Patients allergic to ampicllin / amoxicillin Vancomycin, 1 g IV over 1-2 hours, plus gentamicin, 1.5 mg/ kg IV/IM (not to exceed 120 mg); injection/infusion within 30 minutes of starting the procedure

37. Surgical technique remains the paramount factor in preventing infection, but antibiotic prophylaxis assists the patients host response when some bacterial contamination is inevitable.