|MANAGEMENT OF BACTERIAL
INFECTIONS PART I
|Infection After Minimally Invasive Surgery
John E.A. Wickham
The development of minimally invasive surgery has had a significant effect on the surgical deployment of antibiotic therapy in the last 10 years. In the field of the surgical treatment of renal stone disease, for example, there has been a progression from a major surgical operative procedure through endoscopic stone removal to second-generation extracorporeal lithotripsy, which imposes no interventional trauma whatsoever on the patient. This has in turn reduced the dose and duration of antibiotic therapy from large doses for nearly a fortnight to virtually a single dose or sometimes requiring no antibiotics at all.Open-wound surgery
A decade ago, antibiotic therapy was used in two areas of open-wound surgery:
one to primarily treat postoperative wound infection and the other, more
minor, use was in pre- and postoperative prophylaxis. Post-operative
infection rates in every type of surgery , namely clean, clean-contaminated
and contaminated operations have significantly decreased in the last decade.
[Fig.1] The primary reason for this has been the emphasis on pre and post-operative
antibiotic prophylaxis. This fall in infection rates has been compounded
in the last five years by a steep fall primarily due to the increasing
numbers of operations being carried out as day case or short stay procedures
which has become feasible due to minimally invasive therapy and operations
Approximately 10% of all open-wound procedures become complicated by bacterial involvement . The common source of contamination is by intestinal bacteria as the result of intra-abdominal leakage of intestinal contents either pre- or perioperatively . A second source of bacterial contaminants is from either the skin surface or the theatre atmosphere. The organisms causing the latter infections are usually due to Staphylococcus aureus or Staphylococcus albus, or other nosocomial inhabitants such as Pseudomonas aeruginosa and Klebsiella species.
Ten years ago, the major thrust of antibiotic therapy was to treat wounds that had become infected either due to technical aspects of the surgical procedure itself or as a result of exposure to the theatre atmosphere for a prolonged period of time . Use of prophylactic antibiotics was therefore somewhat discouraged by surgeons, who viewed it as a possible criticism of their surgical technique.
There were, however, a number of areas where preoperative prophylactic antibiotic administration had a proven value, for example, in urology. Urethral instrumentation or the manipulation of kidneys containing infective stones may inadvertently lead to the release of infective organisms into the bloodstream, resulting in the development of serious septicaemic episodes. This was particularly likely because of the free communication between the vascular and collecting systems. Thus, the emphasis of antibiotic therapy shifted from the postoperative control of wound infection to the preoperative prevention of septicaemia due to intravascular contamination. The use of preoperative antibiotic prophylaxis will virtually completely prevent this eventuality. The value of preoperative prophylaxis has been demonstrated in several reported stone series. It has also become apparent that the prevention of bacterial infection is more effective when a high serum drug level is ensured at the time of tissue or blood contamination .Minimally invasive therapy
A marked change of emphasis in antibiotic therapy began in 1979 with the development of endoscopic stone removal. The use of endoscopy was accompanied by an almost negligible rate of infection at the site of the postoperative wound or puncture as the endoscope can be introduced through either small punctures or natural orifices, obviating the need for large open wounds. Wound infections from superficial skin or theatre contaminants therefore also decreased rapidly. [Fig. 2,3] With the use of more modern techniques, infections tend to originate only from already infected sites, such as pyelonephrotic kidneys containing infected calculi. In the experience of the present author, in over 2000 patients treated by endoscopic nephrolithotomy, there has been no significant puncture tract infections.
With the further development of extracorporeal shock-wave lithotripsy, the need for postoperative antibiotic therapy is virtually nil. The second-generation machines require no access wounds or puncture of the abdominal wall, thereby eliminating one major source of infection. The vast majority of renal calculi are sterile, so there is no requirement for antibiotic therapy either during or after treatment. There is, however, still a requirement for antibiotic prophylaxis when infected stones are involved. Thus, in practice, it has now become necessary to use antibiotics in only 10% of all patients presenting for renal stone therapy.Gastroenterological surgery
During open gallbladder surgery, it was routine to give a full course of antibiotic therapy postoperatively because of the risk of wound contamination or development of intra abdominal abscesses due to the escape of infected biliary contents . These infections were usually superficial in the abdominal wall, but had the potential to become gangrenous and therefore life-threatening. In the mid eightees the emphasis shifted to pre-operative antibiotic prophylaxis rather than post-operative therapy and the routine was to administer a broad spectrum intravenous antibiotic at induction or during the procedure followed by a short course for 1 - 3 days post-operatively.
However, subsequent to the first endoscopic cholecystectomy performed in 1989, the use of antibiotic therapy in these cases has changed rapidly and radically. At present in the USA, over 85% of cholecystectomies are performed laparoscopically . During such a procedure, bile may be released into the subhepatic region, resulting in localised abscess or peritonitis . However, one dose of intravenously administered aminoglycoside given at the time of surgery is usually able to control such an eventuality. A short course of cephalosporins are sometimes administered for routine prophylaxis  and, when the risk of clinical infection is high, an alternative therapy is an aminoglycoside combined with ampicillin.
As the use of laparoscopy has been extended into other areas of gastroenterology - for example, appendectomy, colectomy, splenectomy and hernia repair  - it remains evident that prophylactic antibiotic therapy prior to gut endoscopic manipulation is more important than postoperative antibiotic therapy. Laparoscopy precludes local abscess formation at the site of manipulation; infection is rare at the puncture sites where endoscopes and ancillary instruments are introduced into the abdominal cavity, and seldom require antibiotic treatment .Orthopaedic surgery
In the past when orthopaedic surgery invariably involved the exposure of joints to the air, it was clearly essential that antibiotic cover be given during these procedures. With the advent of arthroscopy, which requires only minor puncture wounds, the need for extensive antibiotic therapy has decreased, as it has in other minimally invasive surgical procedures. However, a broad-spectrum antibiotic is still usually given for prophylaxis .Vascular surgery
As already established, with careful technique, the risk of infection is low with minimally invasive vascular surgery . Procedures involving the implantation of large grafts using foreign materials are highly susceptible to infection but, with the increasing use of simple balloon dilatation, the need for large doses of long-term antibiotic treatment has virtually disappeared.Other advantages of minimally invasive surgery
A major advantage of endoscopic surgery vs open-wound surgery is that patients can become mobile sooner and there is also much less restriction of respiratory excursion. Patients are no longer confined to bed for several days with compromised diaphragmatic function and thus avoid the development of postoperative bronchopneumonia, a major cause of morbidity in open surgery. The requirement for considerable postoperative antibiotic therapy to control chest infections has therefore reduced.Conclusions
In summary, during the past 10 years, the development of minimally invasive
techniques in various fields of surgery has radically reduced the need
for either pre- or postoperative antibiotic prophylaxis. The emphasis
of antibiotic treatment has shifted from the need to cover the results
of extensive tissue damage due to invasive surgical techniques to the
use of antibiotics to prevent the development of more localised, significant
infective complications within the abdominal wall, bloodstream or other