Article:
EARLIER DEBRIDEMENT AND ANTIBIOTIC ADMINISTRATION DECREASE INFECTION: Maj. Brown KV, Walker JA, Cortz DS et al. J. Surg. Ortho.p Advances, 2010; Vol 19(1): 18-22. Goals: ascertain the effects of 1) earlier debridement (debridement alone or in combination with locally delivered antibiotics) and 2) the use of local antibiotic-depots on bacterial load following contamination of open fractures. A contaminated, critical sized, rat femur, defect model was used. Results: early debridement and early administration of local antibiotics resulted in lower bacterial loads in bone. There was a significant increase in the rate of infection between 2 and 6 hours and a further increase between 6 and 24 hours when treatment was limited to debridement (alone) as well as when debridement was combined with local antibiotics. Treatment with local antibiotics resulted in a significant reduction in infection at 2 and 6 h hours compared to debridement, alone.
Dr. Cierny’S comments: Surgical antibiotic prophylaxis refers to the administration of antibiotics to patients without clinical evidence of infection in the operative field. The objectives of prophylaxis are to prevent naturally occurring organisms in one site from proliferation in a normally sterile site; to prevent organisms contaminating a normally sterile site from producing diseases; and to prevent infection by exogenous organism. In order to achieve this goal, the surgeon must recognize the high-risk patient, operate in an effective and efficient manner, and keep abreast of local hospital flora and sensitivity patterns. Antibiotic prophylaxis is indicated in the surgical patient when there is an unacceptable incidence of infection or when the incidence of infection is low but such an infection would be devastating or lethal. Prophylaxis accounts for approximately 30% of the antibiotic administration on surgical services in the United States. In most instances, these antibiotics are not justified and may lead to multiple problems, including the selection of resistant organisms. However, when the theory and practice of surgical antibiotic prophylaxis are correctly applied, the patient benefits.
The pathogenesis of a surgical wound infection lends itself to a rational approach to surgical antibiotic prophylaxis. The first step is bacterial contamination of surgically manipulated tissue. Bacterial contamination, a component of every surgical wound, arises from two sources: exogenous contamination from the operative theater; or endogenous contamination from the skin, respiratory, or urogenital tracts of the patient. Whether or not the bacterial contamination produces infection depends on the number and the virulence of the organisms, the adequacy of the patient’s defenses, and the condition of the disrupted (injured) tissue.
The first response to surgical injury and subsequent bacterial contamination is local inflammation. Small vessels leak plasma, and leukocytes emerge in response to local leukotactic substances, migrate into the contaminated area, and begin phagocytosis. Inflammation continues, wound induration develops, local macrophages and vascular components proliferate, and the stage is set for wound maturation. The early local inflammatory phase is virtually identical to what is called the “decisive period” as defined by Burke (see below). If inflammation is not appropriate and phagocytosis is overwhelmed, the patient will develop an infection. Necrosis, ischemia, hemorrhage, and the presence of debris and/or foreign bodies impair the local host-defense mechanisms and decrease the number of bacterial organisms required to cure infection. The overall integrity of the host is important because a compromised host is at increased risk for infection.
If an appropriate antimicrobial agent is present in adequate concentrations, a wound infection in the contaminated tissue is less likely. The antibiotics must be in the tissues during the early, “decisive period” to effectively present bacterial invasion and proliferation. If given later, when the bacteria are well established, the antibiotics will have no prophylactic effect. Similarly, if the compromised host can be protected with prophylactic antibiotics until the local defense mechanisms are capable of eradication local bacterial invasion, the subsequent stages of wound healing can proceed normally.
The concept of a “decisive period” was first recognized when Burke (1961) administered an anti-Staphylococcal antibiotic one to three hours after inoculation of S. aureus into the dermis of a guinea pig model …. early antibiotic administration would reduce the size of the lesion. However, if the anti-Staphylococcal antibiotic was given three hours after dermal infection, the antibiotic was less effective in reducing the size of the lesion. Clinical studies have subsequently demonstrated, conclusively, that antibiotic administered one hour before the surgery significantly decreases the incidence of postoperative infection when compared to placebo. However, if the antibiotic is begun one to four hours after the operation, there is no reduction in the postoperative infection rate.
The correlation between the frequency of infection and the density of microorganisms present in a homogenized sample taken from the wound closure site has been established. Since it is not immediately possible to determine the microbial density of every surgical wound, a system for categorizing a surgical wound based on the probability and degree of microbiologic contamination has been developed. The accuracy with which this clinical classification predicts the incidence of wound infection for general and orthopaedic surgery is well established.
Clean surgical procedures account for 75% of all operations. These procedures are performed under ideal and sterile operating room conditions. The procedures are generally elective and no entry is made into the oropharyngeal cavity or the lumen of the respiratory, alimentary, or genitourinary tract. Inflammation is not encountered and no break in surgical technique occurs. The incidence of wound infection in clean procures is less than 5%.
Clean-contaminated surgical procedures involve entry into the oropharyngeal cavity or the lumen of the respiratory, alimentary, or genitourinary tract without significant contamination from these sites. Clean wounds are included in this category when there is a major break in the surgical technique. Clean- contaminated surgical procures occur in approximately 15% of all surgical operations and wound infection is reported in approximately 10% of these cases. Since the mucosa of the oropharyngeal , respiratory, alimentary and genitourinary tracts harbor diffuse and dense microbiologic flora, some contamination of the wound is e inevitable. Antibiotic prophylaxis is indicated in these patients and should be appropriately tailored to the flora expected in the particular region of surgery. Clean surgery on a compromised host ( ) or transoral fixation of lesions involving the first and second cervical vertebra are examples of clean-contaminated procedures.
Contaminated-dirty surgery includes surgery through traumatic wounds, operative procedures with a major break in sterile technique and operations into a site of active infection. The infection rate is between 20% and 40% in surgery involving these patients. Antibiotic “prophylaxis”, in these circumstances, is directed at the prevention of infection in the soft-tissue planes and wounds previously uncontaminated by bacteria. As such, the antibiotic(s) used may be modified by the preoperative Gram stain or culture results stemming from biopsies of exposed granulating surfaces and/or wounds, themselves. Surgery of open fractures is an example of contaminated-dirty surgery. The risk of subsequent infection increases with the amount of tissue devitalization, the extent of contamination and the systemic compromise of the host.
Final comment: There are few controlled trials to scientifically support a practice mandating emergency-debridement of all open fractures (< 6hrs). However, it is in agreement that 1) all open fractures require immediate, systemic antibiotic coverage and 2) that additional coverage with a local antibiotic-depot (antibiotic beads ) will reduce the incidence even further when treating severe open injuries (Seligson D, Henry SL) when used in conjunction with systemic coverage. BEST PRACTICE: all methods of treatment should impact outcomes within the “decisive period”: immediate antibiotic coverage; host resuscitation; the earliest possible debridement; avoidance of large surgical implants; adequate (and safe) methods of stabilization; soft-tissue coverage within 7 days of injury – Primary_versus_Delayed_Soft_Tissue_Coverage_for.8 .
