SEPSIS AND USE OF ANTIBIOTICS IN COLORECTAL SURGERY
Headings
Wound sepsis
Specialised wound sepsis
Septicaemia
Intra-abdominal abscess
Penicillins
Cephalosporins
Aminoglycosides
Nitroimidazoles
Other agents
Patient factors
Drugs and Chemotherapy
Radiotherapy
Surgical factors
Principles
Clinical trial: quality
Methods
Incidence of sepsis
Flora
Factors related to the incidence of postoperative sepsis
Duration of antibiotic cover
Abdominal wounds: Before the use of antibiotics in colorectal surgery, the incidence of abdominal wound sepsis was between 35 and 61% with the highest incidence for those who have undergone APER and next for those who have had Panproctocolectomy in IBD. It was also common with Colostomy closures and emergency surgery. Careful follow-up is required to document sepsis rates because 40% of wound infections occur after the patient has gone home.
How does one categorise abdominal wall infections?
Category A Erythema and induration in the wound with no pus.
Category B Presence of pus, which occurs in part of the incision or around the skin suture.
Category C Pus, deep to the linea alba, rectus sheath or external oblique aponeurosis causing extensive subcutaneous abscess.
Perineal wounds: When a perineal wound gets infected (79% following APER and 69% following Procto-colectomy; before antibiotics), it invariably leads to a presacral cavity. Among diabetics, there is a risk of developing Fourniers gangrene.
What are the common organisms in Colorectal surgery?
Bacteroides sp,
Staphylococcus albus,
Escherichia coli,
Chlostridium sp,
Proteus,
Pseudomonas sp,
Klebsiella.
Synergistic gangrene
Five organisms Anaerobic streptococcus, peptostreptococcus, chlostridium, e.coli and bacteroides.
Requires wide debridement, repeated desloughing, topical antisepsis and eventual skin grafting.
Gas gangrene
Due to Chlostridium perfringens or sporogenes or paraputrificum.
Mortality is high among elderly diabetics with chronic renal disease and malignancy.
Treatment is by wide debridement, high dose penicillin and hyperbaric oxygen.
Sepsis in the Immunocompromised host:
Those on immunosuppresives for IBD or following Organ transplant fall in this category.
What are the common organisms?
Three bacteria, three virus, one protozoal and one fungal.
Bacteria Staphylococcus
Aerobic Gram negative
Mycobacterium tuberculosis
Virus Herpes Zoster
Cytomegalovirus
Hepatitis B
Protozoal Pneumocystis carinii
Septicaemia:
Defined as SIRS with positive blood culture and documented source of infection. Bacteremia is positive blood culture without SIRS.
The incidence after simple sigmoidoscopy may be as high as 47%. Hence it is important to ensure that the patient does not have artificial heart valves. If so, then the procedure should be done under antibiotic cover. Bacteroides is the commonest organism. Therfore, Flagyl cover should suffice in addition to Augmentin cover.
Other organisms found are Strep.bovis and Strep.milleri.
Intra-abdominal Abscess:
Before use of antibiotics the incidence was 4 to 17%. Nowadays it is less than 5% but may be as high as 13% in emergency surgery.
Available antimicrobial agents:
Penicillin: Keighleys group compared Augmentin with gentamycin and flagyl and found 16% sepsis rate in both groups with significantly more Bacteroides fragilis infections in the Augmentin group.
Verdict This high rate of infection (>10%) is unacceptable.
Cephalosporins: All Cephalosporins except Ceftraixone (Rocephin) have a half life of less than 2 hours. Rocephin has an extremely long half-life. Rocephin with flagyl consistently reduces the infection rate to less than 10% [Shepherd et al., 1986]. Because of its very long half-life, only one dose (1 gm) need to be used (Cost: £11.46p). On the other hand, with Cefuroxime, because of the short half life, it will need to be used for atleast three doses (1.5g, 0.75g, 0.75g). The total cost for this three dose regime will be £12.43p. So Rocephin with Flagyl is more cost-effective. Prolonged use may cause precipitation of the calcium salts in the gall bladder with symptoms of biliary colic, but this is temporary. Also, prolonged use can encourage superinfection.
Aminoglycosides: Physicians have largely discontinued using aminoglycosides with flagyl for prophylaxis because of the nephrotoxicity and ototoxicity and the problems of bacterial resistance.
Amikacin is regarded as the treatment of choice for gentamycin-resistant E.coli and pseudomonas infections.
Nitroimidazoles:
Metronidazole is what is used, commonly. It has a long half-life and is highly effective against Bacteroides.
Other agents:
Co-trimoxazole Short term course in combination with metronidazole has been associated with low rates of sepsis, and is therefore worth using in those who are allergic to penicillin.
Quinolones Ciprofloxacillin has a profound inhibitory effect on the colonic microflora and yet super-infections are unheard of. The main concern is the emerging strain of Enterobacteriaciea against quinolones.
Clindamycin Used to be highly effective against Bacteroides but is no longer used because of the complication of Chlostridium difficile colitis.
Chloramphenicol Excellent activity against gram ve aerobic and a high proportion of anaerobic bacteria. Worth using in Penicillin allergic individuals.
Tetracycline No longer used because of the resistant strains. Topical tetracycline is also not recommended because of the complications of renal failure and adhesions.
Monobactams Have a narrow range of activity against gm-ve aerobes (Aztreonam). If used, it should be combined with agents effective against obligate anaerobes and probably streptococci.
Imipenems This group holds considerable promise as prophylactic and theraupeutic agents in colorectal surgery.
Factors responsible for sepsis in Colorectal surgery:
Patient factors
Age Evidence to support that old age is associated with higher incidence of infection is primarily epidemiological.
Malignancy Those with advanced malignancy have defective host-defence mechanism.
Malnutrition Weight loss of more than 20% is associated with higher incidence of complications (Studley, 1936; Petigrew and Hill, 1986). This is not supported by the Birmingham group. Obesity on the other hand, is associated with higher incidence of wound sepsis.
Both conditions are associated with increased susceptibility to infections. In chronic renal disease, because of immunosuppression and/or dialysis, there is increased risk for three bacterial infections, three viral infections, one fungal and one protozoal infections.
Diabetics have defective phagocytic function and hence they are more susceptible to infections as above.
Patient undergoing emergency surgery in the middle of the night are prone to develop infections, often because of the sub-optimal conditions and gross peritoneal contamination.
Antimicrobials
Steroids and immunosuppresives The Birmingham group suggest that sepsis rates are not significantly higher among patients on steroids. Azathioprine may increase the risk of sepsis, if therapy is associated with leucopenia or thrombocytopenia.
Blood transfusion Allogenic blood transfusion has an immuno-modulating effect (Tartter, 1988). This is considered to be a non-specific immune suppression due to the red cell fragments.
Chemotherapy All forms of Chemotherapy increase the risk of complications.
Radiotherapy Short one week course of RT is not associated with complications whereas, a long four week course is associated with high incidence of complications.
Surgical Factors
Contamination Prediction of wound and intra-abdominal sepsis can be made with swabs taken from the peritoneal cavity and wound at the end of the operation. If there are more than 105 colony-forming units then prolonged antibiotic course is necessary.
Duration surgery If surgery is prolonged to longer than 2 hours, then the level of antibiotics are insufficient unless one is using Ceftriaxone (Rociphen).
Wound protection No proof that wound protection decreases wound sepsis rate.
Shaving Shaving is best done in theatre rather than on the ward.
Drains Open drains increase sepsis rate. Closed suction drains are better.
Blood loss Reduced sepsis rate may be due to lower transfusion rates in units reporting low wound sepsis.
Audit Regular surgical audit improves surgical discipline.
Wound In gross peritoneal contamination, it is best to leave the skin and s.c tissues open. Secondary suturing or delayed pr.closure is not advocated because of the high incidence of secondary infection.
Where the closure is difficult in the presence of severe intra-abdominal sepsis, one might consider temporary closure with Marlex or Teflon mesh (Mathes and Stone, 1975; Boyd, 1977).
For the rest of the topics in this chapter refer to Keighley and Williams. Only two points to make here
a) There is a considerable body of opinion that antiseptic lavage is dangerous in the presence of established peritonitis.
b) Antibiotic cover in IBD should be continued for 5 days.