Postoperative Infections: Prevention and Management
W. David Hager
Mark J. Dougherty
DEFINITIONS
Bacteremia—Infection of the bloodstream can complicate any pelvic infection, but is seen most frequently in association with abscesses, peritonitis, and necrotizing fasciitis.
Cuff cellulitis—A soft tissue infection of the surgical margin in the upper vagina where the uterus was removed.
Drug fever—Elevated temperature that is due to an adverse reaction to medications.
Febrile morbidity—A temperature of 38°C (100.4°F) or greater recorded on two occasions, at least 6 hours apart, more than 24 hours after the surgical procedure.
Necrotizing fasciitis—A severe synergistic bacterial infection of the fascia, subcutaneous tissue, and skin that is often caused by group A beta-hemolytic streptococci, often in combination with other bacteria including methacillin-resistant Staphylococcus aureus (MRSA), anaerobes, and aerobic, gram-negative bacilli.
Surgical Site Infections (SSI)—Recent CDC criteria for SSI’s have been developed using National Health Safety Network (NHSN) criteria; NHSN data provide regularly updated risk stratified rates of SSI for comparison between individual surgeons and between hospitals. (Edwards and colleagues, 2009).
Urinary tract infection—The criterion for defining a urinary tract infection (UTI) is more than 100,000 colonies/mL of a single pathogen from a clean-catch urine and more than 10,000 colonies/mL from a catheterized specimen.
Vaginal cuff hematoma/cuff abscess—A walled-off collection of blood originating from an oozing vascular pedicle or along the vaginal cuff. If the collection becomes infected, it creates an abscess.
Wound cellulitis—Soft tissue infection localized to the skin and adipose tissue above the fascia that is characterized by erythema, warmth, swelling, and tenderness.
Wound seroma—A collection of serous fluid beneath the skin surface.
Infection complicating surgical procedures has been the consternation of gynecologists since the first operations were performed. Multiple interventions have proven value in reduction of SSI, including appropriate perioperative antimicrobial prophylaxis, avoidance of shaving, appropriate skin preparation (such as with chlorhexidine/alcohol), and monitoring of surgeon-specific infection rates.
It is imperative that the gynecologic surgeon understand basic infectious disease concepts in order to treat infected patients appropriately. Diagnosis and treatment are not guesswork but depend on understanding basic principles.
An understanding of bacteria that are a part of the normal vaginal flora enables the gynecologist to recognize the pathogenic bacteria that contribute to postoperative infection. Certain risk factors play a role in increasing postoperative infection rates. Knowledge of these factors can enable the surgeon to take action to alter those risks, and/or be alert for those who are at increased risk. There are various types of postoperative infection, each with its own unique time of onset and usual bacterial etiology. Knowledge about likely causes of a disorder can facilitate decision making when an antibiotic is empirically selected to treat the patient.
Appropriate patient evaluation, including proper culturing techniques, is critical to this diagnostic process. Steps to prevent infection must become routine with every surgeon on every case. These steps are necessary not only for the operator but also for all personnel participating in the surgical and medical management of the patient. These steps are described later in this chapter.
FEBRILE MORBIDITY
In the evaluation of patients who have an elevated temperature in the postoperative period, it is important to recognize that all febrile morbidity is not infectious morbidity. Treating a fever without a definite cause of infection will often do more harm than good.
Several different definitions of febrile morbidity have been used, and this may create confusion for the surgeon. The most frequent definition is a temperature of 38°C (100.4°F) or greater recorded on two occasions, at least 6 hours apart, more than 24 hours after the surgical procedure. This excludes a fever during the first 24 hours. Operative site infections during this time are unusual unless there is preexisting infection at the operative site or gross contamination of the site. Some investigators have used a definition of a single temperature elevation of 39°C (102°F) or greater recorded on any occasion in the postoperative period as indicative of febrile morbidity. We prefer the former definition.
Regardless of the choice of definition of febrile morbidity, it is important to treat infection and not fever. Fever may trigger sensitivity to the possibility of infection, but complete assessment of the patient including assessment for UTI, pneumonia, pelvic infection, DVT, intravascular catheter infection, and drug fever should be performed before antibiotic treatment is initiated.
INCIDENCE
New NHSN definitions for SSI have been created and data collected so that hospitals and surgeons can be compared through public reporting. Many states now legally require public reporting of health care associated events, including SSI. The Centers for Medicare and Medicaid Services has initiated “Payfor-performance” programs that include financial penalties/rewards based on provider performance with SSI rates used as part of the formula. National Health Safety Network data provide risk-stratified percentile rates so that, for instance, median abdominal hysterectomy rates for risk class 0, 1, and 2/3 in 2008 were 0.32, 1.61, and 3.41, respectively. Hospitals in the top 25th percentile had zero infections. The U.S. Department of Health and Human Services has set a national 5-year target to reduce SSI by 25% starting in 2012. In order to achieve this goal, risk factors for infection will need to be reduced.
VAGINAL FLORA
The most frequent source of bacteria that cause postoperative pelvic infection among women is the vagina. The vagina is colonized by large numbers of a variety of bacteria that normally exist in a symbiotic relationship. Several factors influence the vaginal flora, including age, sexual activity, stage of the menstrual cycle, use of antibiotic or immunosuppressive agents, and any invasive procedure.
Mean bacterial counts in vaginal secretions are 108 to 109 bacteria/mL, with three to six different species present. The most frequent aerobic bacteria are Lactobacilli sp., Gardnerella vaginalis, coagulase-negative Staphylococcus, Corynebacterium sp., Enterococcus faecalis species of Streptococcus, and Enterobacteriaceae. Anaerobes outnumber aerobes and include Peptostreptococcus sp., Peptococcus sp., Prevotella bivia, Prevotella disiens, and members of the Bacteroides fragilis group (Table 11.1). These same bacteria are frequently isolated from sites of pelvic infection among women who have undergone gynecologic surgery. This indicates, as Schottmueller proposed at the turn of the century, that pelvic infections are principally a result of endogenous sources of bacteria. The concepts of antibiotic prophylaxis and antiseptic douching before surgery or preoperative placement of antiseptic gel are related to reducing these large numbers of bacteria. Although investigators have found that colonization rates change in relation to the stage of the menstrual cycle, no data have supported the concept that timing of gynecologic surgery in relation to menses alters infection rates.
Surgery itself alters the numbers and types of bacteria in the vagina and cervix. After vaginal and abdominal hysterectomy, the number of lactobacilli decreases, and the number of facultative gram-negative rods, B. fragilis group species, and enterococci increases. Preoperative hospitalization before surgery on a gynecologic ward also alters the vaginal flora in a direction toward more virulent organisms.
TABLE 11.1 Bacteria Composing Normal Vaginal Flora | ||||||||||||||||
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RISK FACTORS FOR INFECTION
Several factors alter the infectious risk morbidity of postoperative patients (Table 11.2). Many of these risk factors may be modified by the surgeon. Appropriate use of perioperative antibiotic prophylaxis, including administration within 1 hour of incision, significantly reduces infection risk. Blood glucose control in diabetes and reduction of immunosuppressive medications may decrease risk. Avoidance of hair removal at the surgical site, especially shaving, by the patient or operative team may significantly reduce risk. Skin preparation with chlorhexidine/alcohol or other appropriate antiseptic also reduces postoperative infection rate. Strict adherence to hand hygiene by health care personnel in the preoperative, perioperative, and postoperative period may also play a significant role in SSI risk.
When a hysterectomy is performed through an infected operative site, there is an increased risk of postoperative infection. Likewise, contamination of the operative field by break in sterile technique or injury to the bowel promotes infection. Duration of surgery is considered to be a risk for infection in most studies, but this actually may reflect experience of the operating surgeon, complexity of the case, or inadequate hemostasis. Lack of adequate hemostasis increases the risk of undrained collections of blood and creates an ideal culture medium for contaminating bacteria. Low hemoglobin and hematocrit levels, preoperatively or postoperatively, have been mentioned as factors in increased rates of postoperative infection, especially of abdominal incisions. No data, however, have indicated that raising the volume of red blood cells decreases the rate of infection. Leaving an excessive amount of devitalized tissue (e.g., large, ligated pedicles) and failure to close dead spaces can predispose to a greater risk of infection. Pedicles should be trim and dry, dead space should be closed, and hemostasis obtained. Lysis of adhesions may increase the risk of infection if a bowel injury occurs.
TABLE 11.2 Risk Factors for Postoperative Infection | ||||||||||||||||||||
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The use of a vaginal cuff drain has been shown to have a significant beneficial effect on decreasing morbidity but has fallen out of favor because of the simplicity and effectiveness of antibiotic prophylaxis.
Bacterial vaginosis, characterized by increased vaginal concentrations of certain anaerobic and facultative bacteria, has been shown to increase the relative risk of postoperative infection in gynecologic procedures. The presence of increased concentrations of pathogenic bacteria adjacent to the site of incision in the vagina allows for ascending spread of these organisms in a susceptible host. Although treatment of bacterial vaginosis in pregnant women may decrease their risk of preterm delivery and preterm, premature rupture of membranes, no studies have shown a decreased rate of postoperative infection in bacterial vaginosis-positive women treated before gynecologic surgery.
ETIOLOGY
All women have bacteria colonizing the vagina in greater or lesser numbers. Women without symptoms have a mean of 4.2 species present. It is these same bacteria normally existing in a symbiotic relationship that ultimately can invade tissue altered by surgery, leading to clinical infection. The virulence of the bacteria and the volume inoculated are countered by the host’s immune defense mechanisms and may be aided by prophylactic antibiotics to combat the occurrence of infection.
The bacteria listed in Table 11.3, which are responsible for postoperative infection after gynecologic surgery, are the same organisms that can be recovered from vaginal cultures of women before hysterectomy, according to Hemsell. The volume of bacteria present and their proximity to the operative site promote a polymicrobial infection in women who experience posthysterectomy infectious morbidity. Aerobic bacteria may initiate the infectious process; as tissue is devitalized and the oxidation reduction potential is altered, anaerobes proliferate and add to the tissue damage. Large, necrotic tissue pedicles and undrained collections of blood are ideal sites for infection to occur. Once the infection has begun, the body’s host immune defense mechanisms initiate an inflammatory response, and attempt to wall off and localize the infection. Infected hematomas and abscesses can result when this occurs.
CATEGORIES OF INFECTION
Not all women who have temperature elevation after gynecologic surgery are infected, and not all of those who are infected have the same clinical syndrome. It is important to categorize the infectious process because treatment can vary accordingly.
TABLE 11.3 Pathogens Responsible for Infections After Gynecologic Surgery | |||||||||||||||||||||||||||
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Cuff Cellulitis
Cuff cellulitis is an infection of the surgical margin in the upper vagina where the uterus was removed. Symptoms and signs of infection usually begin late in the hospital course or even after discharge from the hospital. These patients’ immediate postoperative course may have been completely benign. There is always an element of induration, erythema, and edema in the vaginal cuff immediately after hysterectomy. If the patient becomes infected, she will often have initial symptoms of lower abdominal pain, pelvic pain, back pain, fever, and abnormal vaginal discharge. Examination may reveal persistent hyperemia, induration, and tenderness of the vaginal cuff, and possibly purulent discharge along with fever. The parametrial and adnexal areas are nontender. The white blood cell count usually is mildly to moderately elevated.
Gram-positive aerobes, facultative gram-negative aerobes, and obligate anaerobes can all contribute to the cause of cuff cellulitis. Single- or multiple-agent broad-spectrum antibiotic coverage is effective in treating this infection, although single agents usually are preferred to reduce costs and the likelihood of an allergic reaction.
Infected Vaginal Cuff Hematoma or Cuff Abscess
Hysterectomy can result in small amounts of oozing from vascular pedicles or along the vaginal cuff. This bleeding may result in a walled-off collection of blood called a hematoma. If this localized mass above the vaginal cuff becomes infected, an abscess may result. Bacteria, especially anaerobes, flourish in this environment.
Women with a vaginal cuff abscess present with fever that is usually early in the postoperative period. Other symptoms include chills, pelvic pain, and rectal pressure. Clinical findings include temperature elevation; lower abdominal and vaginal cuff tenderness; the presence of a tender, fluctuant mass near the cuff; and, occasionally, purulent drainage from the cuff. The pain and tenderness is often more predominant on one side.
An infected cuff hematoma actually can present later in the postoperative course than an abscess and usually is associated with a drop in the hemoglobin and hematocrit levels. The hematoma may not be readily palpable but can be delineated on pelvic ultrasound or computed tomographic (CT) scan.
Postoperative Ovarian Abscess
The patient who develops fever and abdominal and pelvic pain late in the postoperative hospital course or after hospital discharge may have a pelvic abscess, possibly of ovarian origin. If there is a sudden increase in abdominal or pelvic pain, a rupture may have occurred. A ruptured abscess should be managed as a surgical emergency, proceeding to a laparoscopy or a laparotomy with excision or drainage of the infected mass. The inciting site for an ovarian abscess is a place of recent follicle expulsion or a site of surgical trauma to an ovary in a premenopausal woman. Ovaries should not be aspirated or probed at the time of hysterectomy for fear that bacteria from the vagina may penetrate the ovary and initiate infection. Once again, anaerobes are the predominant bacteria in an ovarian abscess.
If an ovarian abscess is suspected, then a CT scan should be ordered. The CT scan not only identifies the size and location of the abscess but also allows for visualization and evaluation of the ureters, bladder, and colon. A pelvic ultrasound also may be useful to localize the abscess but does not provide the ancillary information. Many abscesses respond to broad-spectrum antibiotic therapy; but if a tender, fluctuant mass persists, drainage is necessary. A radiologic interventionist may be able to accomplish percutaneous drainage with a needle or catheter using CT or ultrasound guidance, or colpotomy drainage may be possible. For colpotomy drainage to be accomplished safely, the abscess must be fluctuant, fixed in the cul-de-sac, and dissecting the upper third of the rectovaginal septum. With either approach, a closed suction drain should be placed to ensure complete and continued evacuation during the next 2 to 3 days. Some abscesses are amenable to a laparoscopic approach with incision and drainage. Copious irrigation and suctioning are critical if this approach is chosen.
Septic Pelvic Thrombophlebitis
Septic pelvic thrombophlebitis (SPT) complicates gynecologic surgery in 0.1% to 0.5% of procedures. It is usually a diagnosis of exclusion, made when a postoperative patient with febrile morbidity does not respond to appropriate parenteral antibiotic therapy in the absence of an undrained abscess or infected hematoma. The development of SPT is enhanced by venous stasis (e.g., obesity, diabetes), vascular injury, or bacterial contamination of pelvic vessels.
Two forms of SPT have been described. The classic form is seen in association with abdominal surgery. This form occurs 2 to 4 days after surgery and is characterized by fever, tachycardia, gastrointestinal distress, unilateral abdominal pain, and, in 50% to 67% of cases, a palpable abdominal cord resulting from acute thrombus formation. The enigmatic form complicates parturition or pelvic surgery and is characterized by spiking temperatures despite clinical improvement on antibiotics; tachycardia during the temperature spikes; and small, diffusely scattered thrombi in small pelvic vessels. Pelvic findings are minimal in both forms. The diagnosis often may be confirmed by CT scan or magnetic resonance imaging (MRI).
The traditional mainstay of treatment for SPT is anticoagulation with heparin for 7 to 10 days. Some experts recommend changing antibiotics or extending coverage before heparin is considered. All patients should be treated with antibiotics effective against heparinase-producing Bacteroides sp. Longterm anticoagulation is not required unless septic pulmonary emboli have occurred. Lysis of fever may occur 24 to 48 hours after starting heparin, yet other cases may require much longer for complete resolution. Treatment should be continued until the patient is afebrile for 48 hours and clinically well.
Osteitis Pubis
Osteitis pubis rarely complicates gynecologic procedures adjacent to the symphysis pubis, such as retropubic urethral suspension, radical vulvectomy, or pelvic exenteration. Direct or contiguous seeding of the periosteum from pelvic bacteria results in a delayed-onset infection 6 to 8 weeks after the original procedure. Patients report pain and tenderness along the symphysis pubis, especially with ambulation. Low-grade fever, an elevated erythrocyte sedimentation rate, and a moderate leukocytosis have been reported, as well as positive cultures from blood or the bone itself. Aggressive antibiotic therapy covering Staphylococcus aureus and facultative gram-negative bacilli is essential for adequate recovery. If the response is not adequate, surgical debridement of the pubis is necessary.
Wound Infection
Surgical wound infection is possible with any transabdominal gynecologic procedure, but especially with those that are contaminated. Extensive study of the epidemiology of wound infections resulted in a classification of operative wounds in relation to contamination and increasing risk of infection (Table 11.4). Because the vagina is entered during hysterectomy, even an uninfected hysterectomy is classified as a cleancontaminated operation. Fortunately, prophylactic antibiotics and minimally invasive, laparoscopic procedures have greatly reduced the risk of severe, surgical wound infections.
The Centers for Disease Control and Prevention (CDC) definitions of surgical wound infection were modified by Horan et al. This system divides infections into two major categories: (a) an organ/space surgical site infection (SSI) and (b) superficial and deep incision infection. An SSI may be in any anatomic area that was opened or manipulated during a surgical procedure other than the incision itself. This would include most of the infections that develop after hysterectomy. It must develop within 30 days of the procedure and be accompanied by one of the following: diagnosis by a surgeon or attending physician; an abscess or other evidence of infection identified during reoperation or by radiologic or histopathologic examination; aseptically obtained organ/space fluid or tissue, the culture of which resulted in bacterial isolates; or purulent drainage from a drain placed through a stab wound into the organ/space.
Wound Cellulitis
Abdominal wound infections are categorized by their location and severity. The least severe are localized to the skin and adipose tissue above the fascia. Wound cellulitis is characterized by erythema, warmth, swelling, and tenderness. If there is no purulent drainage, antibiotic therapy alone with a cephalosporin or augmented penicillin often is effective. S. aureus, coagulase-negative staphylococci, and streptococci cause most of these infections. If wound cellulitis fails to improve, the possibility of resistant organism infection, such as MRSA, or occult abscess should be considered.
TABLE 11.4 Classification of Operative Wounds in Relation to Contamination and Increasing Risk of Infection | ||||||||||||||||||||||||
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Wound Seroma
A collection of serous fluid beneath the skin surface is a seroma. A small amount of serous drainage may be managed with limited opening of the incision, drainage, and cleansing. Larger collections may require more extensive incision and drainage. Antibiotic therapy is not necessary with an uninfected seroma. If a seroma intermittently or continuously leaks, it may become infected and require antibiotic therapy.
Deep Wound Infection
When purulent drainage is noted, the wound should be opened widely to allow drainage and removal of necrotic tissue. The incision should be probed gently to evaluate fascial integrity. If the fascia is intact, healing is hastened by mechanical debridement followed by loose, wet-to-dry packing with gauze moistened with saline; dilute hydrogen peroxide (1:1 mixture with saline) or Dakin’s solution, 0.5%. Povidone-iodine is to be discouraged because it does not promote the development of granulation tissue. An antibiotic effective against anaerobes such as piperacillin-tazobactam, metronidazole, or a carbapenem must be used.
Evisceration of bowel may occur if the infection involves the fascia. This is a surgical emergency requiring identification of the defect, freshening of the fascial edges, placement of intra-abdominal and subcutaneous closed suction drains, and reinforced closure of the fascia. Some surgeons leave the skin open for delayed closure; others close it primarily.
Necrotizing Fasciitis
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