Infections of Significance in Surgical Patients

1. In the name of God Infections of Significance in Surgical Patients • Present by: MostafaAhani

2. Surgical Site Infections • SSIs are infections of the tissues, organs, or spaces exposed by surgeons during performance of an invasive procedure. SSIs are classified into incisional and organ/space infections, and the former are further subclassified into superficial (limited to skin and subcutaneous tissue) and deep incisional categories.35 The development of SSIs is related to three factors: (a) the degree of microbial contamination of the wound during surgery, (b) the duration of the procedure, and (c) host factors such as diabetes, malnutrition, obesity, immune suppression, and a number of other underlying disease states. Table 6-7 lists risk factors for development of SSIs. By definition, an incisional SSI has occurred if a surgical wound drains purulent material or if the surgeon judges it to be infected and opens it.

3. Risk Factors:

4. Cont… • Surgical wounds are classified based on the presumed magnitude of the bacterial load at the time of surgery (Table 6-8).36 Clean wounds (class I) include those in which no infection is present; only skin microflora potentially contaminate the wound, and no hollow viscus that contains microbes is entered. Class ID wounds are similar except that a prosthetic device (e.g., mesh or valve) is inserted. Clean/contaminated wounds (class II) include those in which a hollow viscus such as the respiratory, alimentary, or genitourinary tracts with indigenous bacterial flora is opened under controlled circumstances without significant spillage of contents. Interestingly, while elective colorectal cases have classically been included as class II cases, a number of studies in the last decade have documented higher SSI rates (9 to 25%).37–39 One study identified two thirds of infections presenting after discharge from hospital, highlighting the need for careful follow-up of these patients.

5. Cont… • Infection is also more common in cases involving entry into the rectal space.39 Contaminated wounds (class III) include open accidental wounds encountered early after injury, those with extensive introduction of bacteria into a normally sterile area of the body due to major breaks in sterile technique (e.g., open cardiac massage), gross spillage of viscus contents such as from the intestine, or incision through inflamed, albeit nonpurulent, tissue. Dirty wounds (class IV) include traumatic wounds in which a significant delay in treatment has occurred and in which necrotic tissue is present, those created in the presence of overt infection as evidenced by the presence of purulent material, and those created to access a perforated viscus accompanied by a high degree of contamination. The microbiology of SSIs is reflective of the initial host microflora such that SSIs following creation of a class I wound are invariable, due solely to skin microbes found on that portion of the body, while SSIs subsequent to a class II wound created for the purpose of elective colon resection may be caused by either skin microbes or colonic microflora, or both.

6. Cont… • In the United States, hospitals are required to conduct surveillance for the development of SSIs for a period of 30 days after the operative procedure.40 Such surveillance has been associated with greater awareness and a reduction in SSI rates, probably in large part based upon the impact of observation and promotion of adherence to appropriate care standards. Several different SSI risk stratification schemes have been developed via retrospective, multivariate analysis of large surveillance data sets. The National Nosocomial Infection Surveillance (NNIS) risk index is commonly used and assesses three factors: (a) American Society of Anesthesiologists Physical Status score greater than 2, (b) class III/IV wound, and (c) duration of operation greater than the 75th percentile for that particular procedure, to refine the risk of infection beyond that achieved by use of wound classification alone. Intriguingly, the risk of SSIs for class I wounds varies from approximately 1 to 2% for patients with low NNIS scores, to approximately 15% for patients with high NNIS scores (e.g., long operations and/or high American Society of Anesthesiologists scores), and it seems clear that additional refinements are required.41

7. Classification

8. Cont… • SSIs are associated with considerable morbidity and occasional lethality, as well as substantial health care costs and patient inconvenience and dissatisfaction.42 For that reason, surgeons strive to avoid SSIs by using the maneuvers described in the previous section Prevention and Treatment of Surgical Infections. Also, the use of prophylactic antibiotics may serve to reduce the incidence of SSI rates during certain types of procedures. For example, it is well accepted that a single dose of an antimicrobial agent should be administered immediately before commencing surgery for class ID, II, III, and IV types of wounds.43It seems reasonable that this practice should be extended to patients in any category with high NNIS scores, although this remains to be proven. Thus the utility of prophylactic antibiotics in reducing the rate of wound infection subsequent to clean surgery remains controversial, and these agents should not be used under routine circumstances (e.g., in healthy young patients). However, because of the potential dire consequences of a wound infection after clean surgery in which prosthetic material is implanted into tissue, patients who undergo such procedures should receive a single preoperative dose of an antibiotic.

9. Cont… Surgical management of the wound is also a critical determinant of the propensity to develop an SSI. In healthy individuals, class I and II wounds may be closed primarily, while skin closure of class III and IV wounds is associated with high rates of incisional SSIs (approximately 25 to 50%). The superficial aspects of these latter types of wounds should be packed open and allowed to heal by secondary intention, although selective use of delayed primary closure has been associated with a reduction in incisional SSI rates.46 It remains to be determined whether NNIS-type stratification schemes can be used prospectively to target specific subgroups of patients who will benefit from the use of prophylactic antibiotic and/or specific wound management techniques. One clear example based on cogent data from clinical trials is that class III wounds in healthy patients undergoing appendectoy for perforated or gangrenous appendicitis can be primarily closed as long as antibiotic therapy directed against aerobes and anaerobes is administered. This practice leads to SSI rates of approximately 3 to 4%.47

10. Cont… • Recent investigations have studied the effect of additional maneuvers in an attempt to further reduce the rate of SSIs. The adverse effects of hyperglycemia on WBC function have been well described.48 A number of recent studies have reported the effects of hyperglycemia in vivo in diabetic patients, with increased SSI rates being associated with hyperglycemia in cardiac surgery patients undergoing bypass.49,50 On this basis, it is recommended that clinicians maintain appropriate blood sugar control in diabetic patients in the perioperative period to minimize the occurrence of SSIs.

11. Cont… • The effects of the level of inhaled oxygen and prewarming of the wound on SSI rates also have been studied. Although an initial study provided evidence that patients who received high levels of inhaled oxygen during colorectal surgery developed fewer SSIs,51 data to the contrary recently have been reported.52,53 In another study, preoperative warming of the wound site for 30 minutes before surgery among patients undergoing clean surgery was associated with a decrease in SSIs (5% with warmed wounds vs. 14% without).54 Unfortunately, several of the aforementioned studies report SSI rates among study patients that are higher than those reported and expected among similar groups of patients, making comparison difficult. Of note, stratification using the NNIS classification methodology was not used. Further evaluation via multicenter studies is needed before implementation of these modalities as standard therapies.

12. Cont… • Effective therapy for incisional SSIs consists solely of incision and drainage without the addition of antibiotics. Antibiotic therapy is reserved for patients in whom evidence of significant cellulitis is present, or who manifest concurrent SIRS. The open wound often is allowed to heal by secondary intention, with dressings being changed twice a day. The use of topical antibiotics and antiseptics to further wound healing remains unproven, although anecdotal studies indicate their potential utility in complex wounds that do not heal with routine measures.55 Despite a paucity of prospective studies,56 vacuum-assisted closure is increasingly used in management of problem wounds and can be applied to complex wounds in difficult locations (Fig. 6-2). Although culture results are of epidemiologic interest, they rarely serve to direct therapy because antibiotics are not routinely withheld until results are known. The treatment of organ/space infections is discussed in Intra-Abdominal Infections, below.

13. Intra-Abdominal Infections • Microbial contamination of the peritoneal cavity is termed peritonitis or intra-abdominal infection, and is classified according to etiology. Primary microbial peritonitis occurs when microbes invade the normally sterile confines of the peritoneal cavity via hematogenous dissemination from a distant source of infection or direct inoculation. This process is more common among patients who retain large amounts of peritoneal fluid due to ascites, and in those individuals who are being treated for renal failure via peritoneal dialysis. These infections invariably are monomicrobial and rarely require surgical intervention. The diagnosis is established based on a patient who has ascites for medical reasons, physical examination that reveals diffuse tenderness and guarding without localized findings, absence of pneumoperitoneum on abdominal flat plate and upright roentgenograms, the presence of more than 100 WBCs/mL, and microbes with a single morphology on Gram's stain performed on fluid obtained via paracentesis. Subsequent cultures will typically demonstrate the presence of gram-positive organisms in patients receiving peritoneal dialysis. In patients without this risk factor organisms can include E. coli, K. pneumoniae, pneumococci, and others, although many different pathogens can be causative. Treatment consists of administration of an antibiotic to which the organism is sensitive; often 14 to 21 days of therapy are required. Removal of indwelling devices (e.g., peritoneal dialysis catheter or peritoneovenous shunt) may be required for effective therapy of recurrent infections.

14. Cont… • Secondary microbial peritonitis occurs subsequent to contamination of the peritoneal cavity due to perforation or severe inflammation and infection of an intra-abdominal organ. Examples include appendicitis, perforation of any portion of the GI tract, or diverticulitis. As noted previously in Source Control, effective therapy requires source control to resect or repair the diseased organ; débridement of necrotic, infected tissue and debris; and administration of antimicrobial agents directed against aerobes and anaerobes.57 This type of antibiotic regimen should be chosen because in most patients the precise diagnosis cannot be established until exploratory laparotomy is performed, and the most morbid form of this disease process is colonic perforation, due to the large number of microbes present. A combination of agents or single agents with a broad spectrum of activity can be used for this purpose; conversion of a parenteral to an oral regimen when the patient's ileus resolves will provide results similar to those achieved with IV antibiotics.58 Effective source control and antibiotic therapy is associated with low failure rates and a mortality rate of approximately 5 to 6%; inability to control the source of infection leads to mortality greater than 40%.59

15. Cont… • Formerly, the presence of an intra-abdominal abscess mandated surgical re-exploration and drainage. Today, the vast majority of such abscesses can be effectively diagnosed via abdominal computed tomographic (CT) imaging techniques and drained percutaneously. Surgical intervention is reserved for those individuals who harbor multiple abscesses, those with abscesses in proximity to vital structures such that percutaneous drainage would be hazardous, and those in whom an ongoing source of contamination (e.g., enteric leak) is identified. The necessity of antimicrobial agent therapy and precise guidelines that dictate duration of catheter drainage have not been established. A short course (3 to 7 days) of antibiotics that possess aerobic and anaerobic activity seems reasonable, and most practitioners leave the drainage catheter in situ until it is clear that cavity collapse has occurred, output is less than 10 to 20 mL/d, no evidence of an ongoing source of contamination is present, and the patient's clinical condition has improved.

16. Organ-Specific Infections • Hepatic abscesses are rare, currently accounting for approximately 15 per 100,000 hospital admissions in the United States. Pyogenic abscesses account for approximately 80% of cases, the remaining 20% being equally divided among parasitic and fungal forms.63 Formerly, pyogenic liver abscesses were caused by pylephlebitis due to neglected appendicitis or diverticulitis. Today, manipulation of the biliary tract to treat a variety of diseases has become a more common cause, although in nearly 50% of patients no cause is identified. The most common aerobic bacteria identified in recent series include E. coli, K. pneumoniae, and other enteric bacilli, enterococci, and Pseudomonas spp., while the most common anaerobic bacteria are Bacteroides spp., anaerobic streptococci, and Fusobacterium spp. C. albicans and other similar yeasts cause the majority of fungal hepatic abscesses. Small (<1 cm), multiple abscesses should be sampled and treated with a 4- to 6-week course of antibiotics. Larger abscesses invariably are amenable to percutaneous drainage, with parameters for antibiotic therapy and drain removal similar to those mentioned above in Intra-Abdominal Infections. Splenic abscesses are extremely rare and are treated in a similar fashion. Recurrent hepatic or splenic abscesses may require operative intervention—unroofing and marsupialization or splenectomy, respectively.

17. Cont… • Secondary pancreatic infections (e.g., infected pancreatic necrosis or pancreatic abscess) occur in approximately 10 to 15% of patients who develop severe pancreatitis with necrosis. The surgical treatment of this disorder was pioneered by Bradley and Allen, who noted significant improvements in outcome for patients undergoing repeated pancreatic débridement of infected pancreatic necrosis.64 Current care of patients with severe acute pancreatitis includes staging with dynamic, contrast-enhanced helical CT scan with 3-mm tomographs to determine the extent of pancreatic necrosis, coupled with the use of one of several prognostic scoring systems. Patients who exhibit significant pancreatic necrosis (grade greater than C, Fig. 6-3) should be carefully monitored in the ICU and undergo follow-up CT examination. A recent change in practice has been the elimination of the routine use of prophylactic antibiotics for prevention of infected pancreatic necrosis. Early results were promising;65 however, several randomized multicenter trials have failed to show benefit and three meta-analyses have confirmed this finding.66–68

18. Contrast-enhanced computed tomographic scan of pancreas with severe pancreatic necrosis. Note lack of IV contrast within the boggy pancreatic bed (large black arrow).

19. Cont… • In two small studies, enteral feedings initiated early, using nasojejunal feeding tubes placed past the ligament of Treitz, have been associated with decreased development of infected pancreatic necrosis, possibly due to a decrease in gut translocation of bacteria. Recent guidelines support the practice of enteral alimentation in these patients, with the addition of parenteral nutrition if nutritional goals cannot be met by tube feeding alone.69,70 • The presence of secondary pancreatic infection should be suspected in patients whose systemic inflammatory response (fever, elevated WBC count, or organ dysfunction) fails to resolve, or in those individuals who initially recuperate, only to develop sepsis syndrome 2 to 3 weeks later. CT-guided aspiration of fluid from the pancreatic bed for performance of Gram's stain and culture analysis is of critical importance. A positive Gram's stain or culture from CT-guided aspiration, or identification of gas within the pancreas on CT scan, mandate operative intervention.

20. Infections of the Skin and Soft Tissue • Infections of the skin and soft tissue can be classified according to whether surgical intervention is required. For example, superficial skin and skin structure infections, such as cellulitis, erysipelas, and lymphangitis, invariably are effectively treated with antibiotics alone, although a search for a local source of infection should be undertaken. Generally, drugs that possess activity against the gram-positive skin microflora that are causative are selected. Furuncles or boils may drain spontaneously or require surgical incision and drainage. Antibiotics are prescribed if significant cellulitis is present or if cellulitis does not rapidly resolve after surgical drainage. Commonly acquired methicillin-resistant S. aureus infection should be suspected if infection persists after treatment with adequate drainage and antibiotics. These infections may require more aggressive drainage and altered antimicrobial therapy.73

21. Cont… • Patients at risk for these types of infections include those who are elderly, immunosuppressed, or diabetic; those who suffer from peripheral vascular disease; or those with a combination of these factors. The common thread among these host factors appears to be compromise of the fascial blood supply to some degree, and if this is coupled with the introduction of exogenous microbes, the result can be devastating. However, it is of note that over the last decade, extremely aggressive necrotizing soft tissue infections among healthy individuals due to streptococci have been described as well.

22. Cont… • Aggressive soft tissue infections are rare, difficult to diagnose, and require immediate surgical intervention plus administration of antimicrobial agents. Failure to do so results in an extremely high mortality rate (approximately 80 to 100%), and even with rapid recognition and intervention, current mortality rates remain high, approximately 16 to 25%.74,75 Eponyms and classification in the past have been a hodgepodge of terminology, such as Meleney's synergistic gangrene, rapidly spreading cellulitis, gas gangrene, and necrotizing fasciitis, among others. Today, it seems best to delineate these serious infections based on the soft tissue layer(s) of involvement (e.g., skin and superficial soft tissue, deep soft tissue, and muscle) and the pathogen(s) that causes them.76

23. Cont… • Initially, the diagnosis is established solely upon a constellation of clinical findings, not all of which are present in every patient. Not surprisingly, patients often develop sepsis syndrome or septic shock without an obvious cause. The extremities, perineum, and torso are most commonly affected, in that order. Careful examination should be undertaken for an entry site such as a small break or sinus in the skin from which grayish, turbid semipurulent material ("dishwater pus") can be expressed, as well as for the presence of skin changes (bronze hue or brawny induration), blebs, or crepitus. The patient often develops pain at the site of infection that appears to be out of proportion to any of the physical manifestations. Any of these findings mandates immediate surgical intervention, which should consist of exposure and direct visualization of potentially infected tissue (including deep soft tissue, fascia, and underlying muscle) and radical resection of affected areas. Radiologic studies should be undertaken only in patients in whom the diagnosis is not seriously considered, as they delay surgical intervention and frequently provide confusing information. Unfortunately, surgical extirpation of infected tissue frequently entails amputation and/or disfiguring procedures; however, incomplete procedures are associated with higher rates of morbidity and mortality (Fig. 6-5).

24. Cont… During the procedure, a Gram's stain should be performed on tissue fluid. Antimicrobial agents directed against gram-positive and gram-negative aerobes and anaerobes (e.g., vancomycin plus a carbapenem), as well as high-dose aqueous penicillin G (16,000 to 20,000 U/d), the latter to treat clostridial pathogens, should be administered. Approximately 50% of such infections are polymicrobial, the remainder being caused by a single organism such as S. pyogenes, P. aeruginosa, or C. perfringens. The microbiology of these polymicrobial infections is similar to that of secondary microbial peritonitis, with the exception that gram-positive cocci are more commonly encountered. Most patients should be returned to the operating room on a scheduled basis to determine if disease progression has occurred. If so, additional resection of infected tissue and débridement should take place. Antibiotic therapy can be refined based on culture and sensitivity results, particularly in the case of monomicrobial soft tissue infections. Adjunctive treatments, including treatment with hyperbaric oxygen or IV Ig, have been described with contradictory results. Hyperbaric oxygen therapy should be strongly considered in patients with infection caused by gas-forming organisms (e.g., C. perfringens). It may be reasonable to consider IV Ig in patients with group A streptococcal infection with toxic shock syndrome and in those patients with a high risk of death, such as the elderly or those with hypotension or bacteremia.77

25. Postoperative Nosocomial Infections • Surgical patients are prone to develop a wide variety of nosocomial infections during the postoperative period, which include SSIs, UTIs, pneumonia, and bacteremic episodes.78 SSIs are discussed above in Surgical Site Infections, and the latter types of nosocomial infections are related to prolonged use of indwelling tubes and catheters for the purpose of urinary drainage, ventilation, and venous and arterial access, respectively. • The presence of a postoperative UTI should be considered based on urinalysis demonstrating WBCs or bacteria, a positive test for leukocyte esterase, or a combination of these elements. The diagnosis is established after more than 104 CFU/mL of microbes are identified by culture techniques in symptomatic patients, or more than 105 CFU/mL in asymptomatic individuals. Treatment for 3 to 5 days with a single antibiotic that achieves high levels in the urine is appropriate. Postoperative surgical patients should have indwelling urinary catheters removed as quickly as possible, typically within 1 to 2 days, as long as they are mobile.

26. Cont… • Prolonged mechanical ventilation is associated with an increased incidence of pneumonia, and is frequently due to pathogens common in the nosocomial environment.79 Frequently these organisms are highly resistant to many different agents.80 The diagnosis of hospital-acquired pneumonia should be made using the presence of a purulent sputum, elevated leukocyte count, fever, and new chest x-ray abnormality. The presence of two of the clinical findings, plus chest x-ray findings, significantly increases the likelihood of ventilator-associated pneumonia.81 Consideration should be given to performing bronchoalveolar lavage to obtain samples to assess by Gram's stain and obtaining a culture to assess for the presence of microbes. Surgical patients should be weaned from mechanical ventilation as soon as feasible, based on oxygenation and inspiratory effort.

27. Cont… • Infection associated with indwelling intravascular catheters has become a common problem among hospitalized patients. Because of the complexity of many surgical procedures, these devices are increasingly used for physiologic monitoring, vascular access, drug delivery, and hyperalimentation. Among the several million catheters inserted each year in the United States, approximately 25% will become colonized, and approximately 5% will be associated with bacteremia. Duration of catheterization, insertion or manipulation under emergency or nonsterile conditions, use for hyperalimentation, and perhaps the use of multilumen catheters increase the risk of infection. Although no randomized trials have been performed, peripherally inserted central venous catheters have a similar catheter-related infection rate.82

28. Cont… • Many patients who develop intravascular catheter infections are asymptomatic, often exhibiting an elevation in the blood WBC count. Blood cultures obtained from a peripheral site and drawn through the catheter that reveal the presence of the same organism increase the index of suspicion for the presence of a catheter infection. Obvious purulence at the exit site of the skin tunnel, severe sepsis syndrome due to any type of organism when other potential causes have been excluded, or bacteremia due to gram-negative aerobes or fungi should lead to catheter removal. Selected catheter infections due to low-virulence microbes such as S. epidermidis can be effectively treated in approximately 50 to 60% of patients with a 14- to 21-day course of an antibiotic, which should be considered when no other vascular access site exists.83 The use of antibiotic-bonded catheters is associated with lower rates of colonization.84 Routine, scheduled catheter changes over a guidewire are associated with slightly lower rates of infection, but an increase in the insertion-related complication rate.85 The surgeon should carefully consider the need for any type of vascular access device, rigorously attend to their maintenance to prevent infection, and remove them as quickly as possible. Use of antibacterial or antifungal agents to prevent catheter infection is of no utility and is contraindicated.

29. Sepsis • Patients presenting with severe sepsis should receive resuscitation fluids to a central venous pressure target of 8 to 12 mmHg, with a goal of mean arterial pressure of 65 mmHg or greater and urine output of 0.5 mL/kg per hour or greater. Delaying this resuscitative step for as little as 3 hours until arrival in the ICU has been shown to result in poor outcome.88 Typically, this goal necessitates early placement of central venous catheter.

30. Cont… • A number of studies have demonstrated the importance of early empiric antibiotic therapy in patients who develop sepsis or nosocomial infection. This therapy should be initiated as soon as possible with broad-spectrum antibiotics directed against most likely organisms, because early appropriate antibiotic therapy has been associated with significant reductions in mortality,89,90 and delays in appropriate antibiotic administration are associated with increased mortality.91 Use of institutional and unit specific sensitivity patterns are critical in selecting an appropriate agent for patients with nosocomial infection. It is key, however, to obtain cultures of appropriate areas without delaying initiating antibiotics so that appropriate adjustment of antibiotic therapy can take place when culture results return.

31. Cont… • Multiple trials have evaluated the use of vasopressors and inotropes for treatment of septic shock. Current suggestions for first-line agents based on effects on splanchnic perfusion include norepinephrine, dopamine, and vasopressin.92,93 It is important to titrate therapy based on other parameters such as mixed venous oxygen saturation and plasma lactate levels as well as mean arterial pressure to reduce the risk of vasopressor-induced perfusion deficits. Several recent randomized trials have failed to demonstrate benefit with use of pulmonary arterial catheterization, leading to a significant decrease in its use.

32. Cont… • A number of other adjunctive therapies are useful in treatment of the patient with severe sepsis and septic shock. Corticosteroids, first evaluated unsuccessfully in the 1980s for treatment of sepsis (high dose), have recently been reintroduced to the armamentarium of the practitioner after the observation that many patients with septic shock have a relative adrenal insufficiency. Low-dose corticosteroids (hydrocortisone at 300 mg/d or less) can be used in patients with septic shock who are not responsive to fluids and vasopressors. However, a recent randomized trial failed to show survival benefit. Recombinant human activated protein C (drotrecogin alfa, Xigris) has been associated with significant survival benefit in patients with severe sepsis and at least one organ failure.94 In surgical patients, this therapy should be reserved for patients with at least two organ failures or for patients with septic shock. Patients with acute lung injury associated with sepsis should receive mechanical ventilation with tidal volumes of 6 mL/kg and pulmonary airway plateau pressures of 30 cm H2O or less. Finally, red blood cell transfusion should be reserved for patients with hemoglobin of less than 7 g/dL, with a more liberal transfusion strategy reserved for those patients with severe coronary artery disease, ongoing blood loss, or severe hypoxemia.

33. Blood-Borne Pathogens • Although alarming to contemplate, the risk of HIV transmission from patient to surgeon is low. By December 31, 2001, there had been six cases of surgeons with HIV seroconversion from a possible occupational exposure, from a total of 469,850 HIV cases to that date reported to the Centers for Disease Control and Prevention. Of the groups of health care workers with likely occupationally acquired HIV infection (n = 195), surgeons were one of the lower risk groups (compared to nurses at 59 cases and nonsurgeon physicians at 18 cases).95 Transmission of HIV (and other infections spread by blood and body fluid) from patient to health care worker can be minimized by observation of universal precautions, which include the following: (a) routine use of barriers (such as gloves and/or goggles) when anticipating contact with blood or body fluids, (b) washing of hands and other skin surfaces immediately after contact with blood or body fluids, and (c) careful handling and disposal of sharp instruments during and after use. The current estimate of the risk of transmission is 0.3% after needlestick.

34. Cont… • Postexposure prophylaxis for HIV has significantly decreased the risk of seroconversion for health care workers with occupational exposure to HIV. Steps to initiate postexposure prophylaxis should be initiated within hours rather than days for the most effective preventive therapy. Postexposure prophylaxis with a two- or three-drug regimen should be initiated for health care workers with significant exposure to patients with an HIV-positive status. If a patient's HIV status is unknown, it may be advisable to begin postexposure prophylaxis while testing is carried out, particularly if the patient is at high risk for infection due to HIV (e.g., IV narcotic use). Generally, postexposure prophylaxis is not warranted for exposure to sources with unknown status, such as deceased persons or needles from a sharps container.

35. Cont… • The risks for surgeons of acquiring HIV infection have recently been evaluated by Goldberg and coauthors.96 They noted that the risks are related to the prevalence of HIV infection in the population being cared for, the probability of transmission from a percutaneous injury suffered while caring for an infected patient, the number of such injuries sustained, and the use of postexposure prophylaxis. Annual calculated risks in Glasgow, Scotland, ranged from one in 200,000 for general surgeons not utilizing postexposure prophylaxis to as low as one in 10,000,000 with use of routine postexposure prophylaxis after significant exposures.

36. Cont… • Hepatitis C virus (HCV), previously known as non-A, non-B hepatitis, is a RNA flavivirus first identified specifically in the late 1980s. This virus is confined to humans and chimpanzees. A chronic carrier state develops in 75 to 80% of patients with the infection, with chronic liver disease occurring in three fourths of patients developing chronic infection. The number of new infections per year has declined since the 1980s due to the incorporation of testing of the blood supply for this virus. Fortunately, HCV virus is not transmitted efficiently through occupational exposures to blood, with the seroconversion rate after accidental needlestick reported to be approximately 2%.100 To date, a vaccine to prevent HCV infection has not been developed. Experimental studies in chimpanzees with HCV Ig using a model of needlestick injury have failed to demonstrate a protective effect of this treatment in seroconversion after exposure, and no effective antiviral agents for postexposure prophylaxis are available. Early treatment of infection with INF- has been considered; however, this exposes patients who may not develop HCV infection–related sequelae to the side effects of this drug.101

37. Cont… • Hepatitis B virus (HBV) is a DNA virus that affects only humans. Primary infection with HBV generally is self-limited (~6% of those infected are over 5 years of age), but can progress to a chronic carrier state. Death from chronic liver disease or hepatocellular cancer occurs in roughly 30% of chronically infected persons. Surgeons and other health care workers are at high risk for this blood-borne infection and should receive the HBV vaccine; children are routinely vaccinated in the United States.97 This vaccine has contributed to a significant decline in the number of new cases of HBV per year in the United States, from approximately 27,000 new cases in 1984 to 4700 new cases in 2006.98 In the postexposure setting, hepatitis B immune globulin confers approximately 75% protection from HBV infection.99

38. Thanks for your attention