Prophylactic And Therapeutic Antibiotics In Surgery Notes

Prophylactic And Therapeutic Antibiotics In Surgery

Antibiotics In Surgery Introduction

• Antibiotics are indicated for use in a surgical patient either to prevent infection (prophylactic) or to treat an established infection (therapeutic).
• Empirical antibiotics means antibiotics which are used to treat clinically suspected infections till culture and sensitivity reports are available. Before the days of antibiotics almost every surgery was infected, and the mortality rates were very high.
• The discovery of penicillin in 1928 by Sir Alexander Fleming changed the world of medicine. Every patient who undergoes in-patient surgery will have prophylactic antibiotics.
• Prophylactic antibiotics depend upon the type of most probable organisms which may colonise after a particular surgery.
• One example is the use of gentamicin for potential contamination that can happen during division of the cystic duct during laparoscopic cholecystectomy.

Read And Learn More: Basic Principles Of Surgery Notes

Common Organisms In Surgical Site Infections

• Staphylococcus aureus
• Staphylococcus epidermidis
• Aerobic streptococci
• Anaerobic cocci

Antibiotic Prophylaxis

• Prophylactic antibiotics are most used to prevent infection of the surgical site.
• It is important to note that only infection of the surgical incision is prevented, and it does not prevent other nosocomial infections. Antibiotic prophylaxis is indicated in clean contaminated and contaminated operations.
• In clean surgeries, antibiotics are only indicated in case of prosthetic implants such as orthopaedic surgeries. Other clean surgeries such as breast or hernia operations, evidence has shown that antibiotic prophylaxis is not required.
• Most of the surgical site infections are caused by endogenous gram-positive cocci that reside on the skin of the patient. Infection from exogenous sources such as health care workers or cross-contamination from other patients reflects poor hospital standards and strict action should be taken to prevent such infections.
• Antibiotics must be administered preoperatively, 1 hour before the skin incision is made, in order to attain maximum blood and tissue concentrations before bacterial growth can become established.
• However, vancomycin and levofloxacin, if these drugs are used for prophylaxis, have to be administered within 120 minutes of the procedural incision due to longer administration times. In case of long duration surgeries, or in surgeries with excessive blood loss, a repeat dosing will be required, usually at 4 hourly intervals, to maintain the desired tissue levels.
• Unnecessary prolonged usage of prophylactic antibiotics is potentially harmful and increases the risk of other nosocomial infections.
• Everyone should know commonly used antibiotics, mechanism of action and their coverage.

Commonly used antibiotics, mechanism of action and their coverage:

Choice of Antibiotic

• As most of the SSIs are caused by gram-positive cocci like Staphylococcus aureus, coagulase negative Staphylococcus, etc., prophylactic antibiotics directed against these are used for clean and clean contaminated cases such as elective biliary and gastric surgeries.
• The recommended antibiotic is a first generation cephalosporin such as cefazolin. An alternative in patients with penicillin allergy is clindamycin.
• In cases which require a gram-negative or anaerobic coverage, either a second-generation cephalosporin can be used, or a first-generation cephalosporin with metronidazole is another choice.
• In cases of emergencies, such as necrotising soft tissue infections that require debridement or perforation peritonitis with gross intra-abdominal contamination that require exploratory laparotomy, the antibiotic used for prophylaxis is continued as the therapeutic drug even after the surgery.
• It is better to use the term empirical antibiotics than prophylactic antibiotics in this type of situation. Once the culture sensitivity pattern is available, antibiotics are changed accordingly.

Prophylactic Antibiotics:

• The antibiotic should have a narrow spectrum of coverage of the relevant organisms that are prevalent in causing surgical site infection—which depends on the site and type of surgery.
• The same antibiotic should not be a part of the therapeutic regimens for infection as it may lead to induction of resistance.
• Should be administered 1 hour before surgery and should be stopped within 24 hours after surgery— ideally single dose.
• Should be safe.

Therapeutic Antibiotics

• In cases of established infection, the use of antibiotics is therapeutic, to eradicate the organism causing the infection. To choose appropriate antibiotics, it is important to identify the causative organism and determine its sensitivity pattern, to tailor treatment and avoid the emergence of resistant strains.
• It should be kept in mind that antibiotic treatment does not replace surgical treatment, and it is just an adjunct to proper surgical drainage and eradication of infection. In a case of simple peritonitis—example acute appendicitis without shock, antibiotics are given for 5 to 7 days.
• However, in cases of peritonitis and shock due to appendicular perforations, antibiotics may have to be given for 10 to 14 days. More details are given in Chapter 45 on peritonitis.
• Antibiotic therapy can be started empirically as soon as a diagnosis of surgical infection is made, and the choice of antibiotic depends on the most common organisms suspected to cause the infection.
• Prior to starting empirical antibiotics, it is important to collect pus or tissue samples from the wound, to be sent for cultures, so that the organism can be identified, sensitivity pattern can be obtained, and accordingly, we can modify the choice of antibiotic, if necessary.

Therapeutic Antibiotics:

• Choose appropriate antibiotics based on culture and sensitivity pattern of the organism.
• Avoid overdosing and inappropriate combinations.
• Educate patients to avoid self-prescribing antibiotics.
• Stop treatment with antibiotics as soon as infection subsides.
• Adopt antibiotic stewardship programmes in hospitals and increase awareness among all doctors.

There are two approaches to choosing therapeutic antibiotics—narrow-spectrum coverage, which treats a known infection when the sensitivity pattern of the organism is available; or broad-spectrum coverage, when the organism is not known and complete gram-positive, gram-negative, and anaerobic coverage is required, e.g. in patients with perforation peritonitis, we can start a 3rd generation cephalosporin such as cefoperazone along with metronidazole.

• Examples: Cefazolin, vancomycin, and gentamicin. For patients receiving cefazolin, 2 g is the current recommended dose except for patients weighing greater than or equal to 120 kg, who should receive 3 g.
• Once the sensitivity pattern of the organism is available, then the antibiotic treatment can be deescalated, if the patient is improving.
• If there is no clinical response to antibiotics, then a thorough review of the patient must be done, as there might be an underlying persistent infection that might need to be drained surgically, or a new infection might have developed.

Please note: The various infections and their treatment have been given in the respective chapters. For example, breast abscess—antibiotics MRSA, etc. in Chapter 39 on breast. In the same fashion, details about antibiotics can be got from other chapters such as skin, peritonitis, intestinal obstruction, etc.

Some common infections, causative organisms, and antibiotic treatment are given.

Common infections, organisms, antibiotics and treatment plan: