antibiotic use in surgery.

1. Antibiotics use in surgery
,prophylaxis and therapeutic
By Dr Mengistu Kassa
Assistant professor of General surgery
Debretabor university , Ethiopia
4/23/2022 1
By Dr Mengistu RI

2. Outline
 Introduction
 Classification of antibiotics
 Rational use of antibiotics
 General principle of use of antibiotics
 Indication for antibiotic use
 Irrational use of antibiotics
 Antibiotic resistance
 Summary
 References
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3. Introduction
Antibiotics are chemical substances obtained
from microbes/microorganisms that able to
inhibit or eradicate the growth of the other
microorganisms
The introduction of antimicrobials has greatly
revolutionized the patient out come suffering
from infection.
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4.  Since irrational use of antibiotics may cause
unnecessary morbidity and mortality its rational use
is vital in management of patient with infection
 Understanding the pharmacokinetics (PK) and
pharmacodynamics (PD) of antibiotics helps achieve
maximum benefit with less side effects.
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5.  The rate and extent of drug absorption is affected by
drug and patient characteristics.
 Distribution of the antibiotics determines whether
the antibiotic can be used for a specific infection
 Liver is the major site of drug metabolism & the
kidneys are the major site of drug excretion.
 Most antibiotics require dose adjustments in renal
failure.
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6.  Pharmacokinetics properties of antibiotics includes
• Bioavailability
• Half-life (t1/2)
 Pharmacodynamics properties of antibiotics includes:
• Concentration dependent killing
• Time dependent killing
• Post antibiotic effect
• Dose and dosing frequency of antibiotics are
determined based on the PK and PD properties
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7. Classification of antibiotics
I. Based on mode of
action
• Bacteriostatic - is
adequate for treatment of
most infections
• Bacteriocidal
 For cure in patients with
altered immunity
 For protected infectious
foci (endocarditis or
meningitis)
 Infections like complicated
s. aureus bacteremia
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8. II. Based on spectrum of action
 Narrow spectrum
antibiotics acting only on a single or a limited group of
microorganisms
 Broad spectrum
antibiotics which affects a wide variety of microbial
species
 Extended spectrum
antibiotics that are effective against gram-positive
organisms and also against a significant number of
gram-negative bacteria
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9. III. According to molecular structure
Beta lactams
Quinolones
Aminoglycosides
Macrolides
Tetracycline's
Sulphonamides
Glycopeptides
others
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10. IV. Site of action of antibiotics
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11. Ideal antibiotics criteria
 Most selective, most effective
 More bactericidal effect
 Antibacterial effect is not interfered by body fluid,
exudate, plasma protein or enzymes and persist for a
long duration in the blood
 Minimal toxicity
 Resistance develops slowly
 Given by any route
 Reachable cost
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12. Factors influencing the selection of antibiotics
 Clinical and antimicrobial
diagnosis
 Severity of illness
 Host factor
 Physician knowledge and
attitude
 Availability of
antimicrobials
 Cost of antibiotic
 Patient attitude
 Pattern of antimicrobial
resistance
 Antimicrobial policy
 Commercial influence
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13. Rational use of antimicrobials
Rational use of antibiotics requires;
 Patients receive medications appropriate to their
clinical needs in doses that meet their own
individual requirements for an adequate period of
time at the lowest cost to them and to the
community (WHO)
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14. General principles of antibiotic use
 Make a diagnosis defining
 site of infection
 type of organism responsible
 antibiotic sensitivity
 Decide whether antibiotic is necessary or not
 Select the best drug considering
 Sensitivity, pharmacokinetic factor, optimum dose,
frequency, route, duration & patients factor
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15. Cont…
 Remove barrier to cure
 Abscess
 Obstruction
 Continue therapy until apparent cure
 Test for cure
 clinical
 microbiological
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16. Indications for antibiotic use
Antibiotics can be used for prophylactic or
therapeutic purpose.
Therapeutic can be either definitive or empiric
therapy.
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17. Antibiotic Prophylaxis
Administration of an antimicrobial agent or agents
prior to initiation of certain specific types of surgical
procedures in order to reduce the number of
microbes that enter the tissue or body cavity.
• It does not prevent postoperative nosocomial
infections
• Postoperative doses of an antimicrobial agent
provides no additional benefit, and this practice
should be discouraged
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18. Goals of Antibiotic Prophylaxis
Reduce the incidence of surgical site infection
(SSI)
Minimize the effect on the patient’s normal
bacterial flora.
Minimize adverse side effects of antibiotics.
Minimize the emergence of antibiotics resistant
strains of bacteria.
Cost effectiveness.
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19. General principles of antimicrobial
surgical prophylaxis
 The antibiotic should be active against common
surgical wound pathogens; unnecessarily broad
coverage should be avoided.
The antibiotic should have proved efficacy in
clinical trials.
The antibiotic must achieve concentrations
greater than the MIC of suspected pathogens,
and these concentrations must be present at
the time of incision.
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20.  The shortest possible course—ideally a single dose—
of the most effective and least toxic antibiotic should
be used.
 The newer broad-spectrum antibiotics should be
reserved for therapy of resistant infections.
 If all other factors are equal, the least expensive
agent should be used.
 Limit antibiotic use to a high-risk situation.
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21. Indications for Prophylaxis
Indications:
– Contaminated and clean contaminated
procedures
– Operations in which postop infections may be
catastrophic e.g open heart surgery
– Placement of prosthetic materials
– Procedures in imunocompromised pts.
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22. Cont…
Timing:
 within one to two hours before the initial skin
Incision
 By definition, prophylaxis is limited to the time prior
to and during the operative procedure; in the vast
majority of cases only a single dose of antibiotic is
required.
 Duration : 24 hrs, up to 48 hrs for cardiac surgery
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23. Indications for repeat dose of prophylactic antibiotic
– Procedure lasting > 3 - 4 hours
– Major blood loss
– Extensive burn
Doubling dose may be appropriate in morbidly
obese patients.
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24. Antibiotic Prophylaxis for GI Surgery
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25. 4/23/2022 25
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26. Antibiotic Prophylaxis for Head & Neck
Surgery
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27. Antibiotic Prophylaxis for
Neurosurgery
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28. Antibiotic Prophylaxis Urosurgery
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31. Antibiotic Prophylaxis Thoracic
surgery
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32. Common error in antibiotic prophylaxis
Selection of wrong antibiotic
The initial therapy too early or too late
Excessive duration
Inappropriate use of broad spectrum antibiotics
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33. Disadvantages of prophylactic antibiotics
 Toxic/allergic reaction
 Superinfection with more resistant flora
 The infection may be temporarily masked
 Ecology of the hospital flora may be altered
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34. 4/23/2022 By Dr Mengistu RI 34
Empiric therapy Definitive therapy
Therapeutic antibiotics

35. Definitive therapy
• Treatment of established infections
• Depend on susceptibility & sensitivity tests.
• Requires isolation of the pathogen.
• Requires knowledge of the MIC and MBC
• Advantage:most effective, least toxicity and the
narrowest selection
• Disadvantage: delay treatment, specimen may be
difficult to get, varying sensitivity patterns in
different hospitals
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36. Empiric therapy
When to start ?
• Risk of surgical infection is high - based on the underlying
disease process (e.g. perforated appendicitis)
• Significant contamination during surgery has occurred
(e.g. considerable spillage of colon contents)
• In critically ill patients – potential site of infection has
been identified
• Severe sepsis or septic shock
NB: Stop if the presence of a local site or systemic infection
is not revealed
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37. Empirical therapy: Approach
• Formulate a clinical diagnosis of microbial infection
• Obtain specimen for laboratory examination
• Formulate a microbiologic diagnosis
• Determine the necessity for empirical therapy
• Institute treatment
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38. Duration of empiric therapy
• Should be limited to a short course of days (3 to 5
days), and should be curtailed as soon as possible
based on microbiologic data.
• Obviously, prophylaxis merges into empirical therapy
in based on intraoperative findings.
• Similarly, empirical therapy merges into therapy of
established infection in some patients as well.
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39. • Differs depending on whether the infection is
monomicrobial or polymicrobial.
• Monomicrobial infections:
– Nosocomial which occurred in postoperative
patients, e.g. UTI, pneumonia, catheter-related
infection.
– Therapy for monomicrobial infections follows
standard guidelines: 3 to 5 days for UTIs, 7 to 10
days for pneumonia, and 7 to14 days for
bacteremia.
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40. • Polymicrobial infections:
– Primary therapeutic modality is source control
– Culture results less helpful
– Thus, antibiotic regimen should not be modified solely
on culture information. Clinical course is more
important
• Serious infection may require prolonged courses of
therapy with two or more agents, particularly if a
multidrug-resistant pathogen is causative.
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41. Optimal duration of AB Rx for
polymicrobial infection
• Penetrating GI trauma without extensive
contamination
– 12-24hours
• Perforated/gangrenous appendicitis
– 3-5days
• Peritoneal soilage due to perforated viscus with
moderate degrees of contamination
– 5-7days
• Extensive peritoneal
soilage/immunocompromised host
– 7-14days
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42. Rationale for combination antimicrobial therapy
• To provide broad-spectrum empiric therapy in
seriously ill patients.
• To treat polymicrobial infections such as intra-
abdominal abscesses.
• To decrease the emergence of resistant strains.
• To decrease dose-related toxicity by using reduced
doses of one or more components of the drug
regimen.
• To obtain enhanced inhibition or killing.
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43. Irrational use of antibiotics
 Irrational use of antibiotics is a major problem worldwide
 WHO estimates more than half of all medicines are
prescribed, dispensed or sold inappropriately
 And half of all patients fail to take them correctly
 Use of too many medicines per patient(poly pharmacy)
 Overuse of injections when oral formulations would be
more appropriate
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44. Irrational use Cont…
 Failure to prescribe in accordance with clinical guidelines
 No indication for antibiotic use
 Wrong selection of antibiotic
 Use of antibiotic in inappropriate dose, route, duration
 Inappropriate combination
 Unnecessary use of the costly antibiotic
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45. How to over come irrational use of
antimicrobials
 Appropriate knowledge and attitude of the physician
 Local and national antibiotic policy
 Most frequently used drugs should be made available
 Bacteriologic confirmation of infection should be easily
available
 Appropriate information regarding the newer
antimicrobials should be available
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46. Common causes of failure of antibiotics therapy
DRUGS :
– Inappropriate drug
– Inadequate dose
– Improper route of administration
– Accelerated inactivation
– Poor penetration
HOST :
– Poor host defence
– Undrained pus
– Retained infected foreign bodies
– Necrotic tissues
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47. Pathogen
– Drug resistence
– Superinfection
– Dual infection initially
Laboratory
– Erroneous report of susceptible pathogen
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48. Antimicrobial resistance
Intrinsic
Drug target is not present in the bacteria’s
metabolic pathways
Acquired
Mutation
Transfer of genetic material from resistant to
susceptible organisms (plasmids, transposons,
bacteriophages)
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49. Mechanism of resistance
Inactivation of drugs by enzymes produced by
bacteria
Change of the site of antibacterial action
Impaired access to the site of antibacterial action
Spontaneous mutations with selective
multiplication of resistant strain
By transmission of genes from other organism
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50. Resistance to Antibiotics
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51. Prevention of drug resistance
May be achieved by
 Avoiding indiscriminate use
 Ensuring the appropriate dose & duration of therapy
 Using antimicrobial combination in selected
circumstances
 Constant monitoring of the resistance patterns in
hospital or community
 Limiting the use of newer antibiotics as long as the
currently used drugs are effective
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52. When to use newer antimicrobials
 Therapeutic advantage
 Decreased toxicity
 Better tolerance
 Lower cost
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53. Summary
• Prophylactic antibiotic should be given in clean surgery which
involves prosthetic implants, in clean-contaminated and
contaminated surgeries
• Prophylactic antibiotics should be administered within 1 hour
prior to incision
• Therapeutic antibiotic should be started for dirty wound
• Empirical therapy should be altered according to the
sensitivity of the culture
• Escalation and de-escalation of antibiotics should be done
based on clinical response and aided by culture and sensitivity
results
• Appropriate choice of antibiotics, dosage, compliance should
be ensured to avoid emergence of resistance
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54. REFERENCES
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55. Thank you!
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