醫(yī)學(xué) 感染-【漢魅HanMei-醫(yī)學(xué)專(zhuān)區(qū)分享】課件

1、Surgical InfectionTeng ChangshengDept. of general surgeryBeijing Friendship HospitalAffiliated to Capital University of Medical SciencesGENERAL CONSIDERATIONS Surgical infections can be defined as infections that require operative treatment or result from operative treatment. Infections that require

2、 operative treatment 1. necrotizing soft tissue infection 2. body cavity infection 3. confined tissue, organ, and joint infection 4. prosthetic device-associated infections Classification of Surgery Infection一 according to pathogenic bacterial:1. Nonspecific infection staphylococcus aureus ， Strepto

3、coccus Escherichia coli， Bacillus proteus，pseudomon. 2. Specific infection二 according to pathogenic process1.Acute infection2.Chronic infection3.Subacute infection Infections that result from operative treatment include: 1. wound infection, 2. postoperative abscess 3. postoperative peritonitis 4. po

4、stoperative body cavity infections 5. hospital-acquired infection(result from the transmission of pathogens from a source in the hospital environment to a previously uninfected patient) such as pneumonias, urinary tract infection. Determinants of Infection The development of surgical infection depen

5、ds on several factors:1. Microbial pathogenicity 2. Host defenses,3. The local environment 4. Surgical technique Microbial Pathogenicity1.Thick capsules2. Resist digestion by lysosomal enzymes.3.Elaborate toxins: endotoxins ,neurotoxins Local Environmental FactorsLocal environmental factors inhibit

6、systemic host defenses from being fully effective: Devitalization of tissue Foreign bodiesDiagnosisDiagnosis of surgical infection should be accorded to clinical examination and laboratory examination. Clinical Examination1.Systemic symptoms: Fever and Chills Elevated pulse rate 2.Endemic signs and

7、symptoms: Redness Swelling Heat Pain Loss of function. 3. shock , dysfunction of organs 4.Special manifestation 5.HistoryOperative treatment include : incising and draining an abscess opening an infected wound removing an infected foreign body repairing or diverting a bowel leak draining an intra-ab

8、dominal abscessSystemic treatmentIt apply for severe infection especially systemic infection. Methods include: support treatment, antibiotics and operation. TYPES OF SURGICAL INFECTIONS Soft Tissue Infections: Infection of the soft tissues, skin, subcutaneous fat, fascia, and muscle, usually can be

9、treated by antibiotics unless an abscess is present or tissue necrosis is present. Cellulitis Cellulitis is a spreading infection of the skin and subcutaneous tissues. It is characterized by local pain and tenderness, edema, and erythema. Usually the border between infected and uninvolved skin is in

10、distinctAbscess and FuruncleAn abscess is localized collection of pus surrounded by an area of inflamed tissue in which hypermia and infiltration of leukocytesis marked. A furuncle is an abscess in a sweat gland or hair follicle. The inflammatory reaction is intense, leading to tissue necrosis and t

11、he formation of a central core. This is surrounded by a peripheral zone of cellulitis. Carbuncle A carbuncle is a multilocular suppurative extension of a furuncle into the subcutaneous tissue. The nape of the neck, dorsum of trunk, hands and digits, and hirsute portions of the chest and abdomen are

12、apt to be involved. Individual compartments in a carbuncle are maintained through persistence of fascial attachments to the skin. As these numerous component locules rupture separately, individual fistulas appear. Necrotizing Soft Tissue Infections Soft tissue infection that result in tissue necrosi

13、s are less common than other forms of soft tissue infections but are more serious because of their propensity for extensive destruction of tissues and high mortality rate. Names such as necrotizing fasciitis, streptococcal gangrene, bacterial synergistic gangrene, clostridial myonecrosis, and Fourni

14、ers gangrene are commonly used. Differentiate these infections are based on predisposing conditions, presence of pain, toxicity, fever, presence of crepitus, appearance of the skin and subcutaneous tissues, and whether or not bullae are present. Necrotizing fasciitis is rarely limited to fascia and

15、myonecrosis is rarely limited to muscle.Pathogenic bacterial Most necrotizing soft tissue infection are caused by mixed aerobic and anaerobic gram-negative and gram-positive bacteria. Clostridium species are the most common, cause the most dramatic infections with rapid progression, early toxicity,

16、and high mortality rate. Manifestation and Diagnosisskin necrosis or bullae crepitusEarly mental confusion, toxicity, and failure to respond to nonoperative therapyTetanusTetanus is caused by C. tetani, a large gram-positive sporeforming bacillus. It is acquired by implantation of the organisms into

17、 tissues by means of breaks in the mucosal or skin barriers. Action of C. tetaniC. tetani elaborates : tetanospasmin tetanolysin. Tetanospasmin acts on the anterior horn cells of the spinal cord and on the brainstem. It blocks inhibitor synapses at these sites, leading to muscle spasms and hyperrefl

18、exia. Tetanolysin is cardiotoxic and causes hemolysisManifestation of TetanusSymptoms: restlessness, headache, muscle spasms with vague discomfort in the neck, lumbar region, and jaws,swallowing difficult, stiff neck Progressively,Orthotonos, opisthotonos, and emprosthotonos ,Generalized toxic convu

19、lsions. These convulsions may involve the laryngeal and respiratory muscles and result in fatal acute asphyxia.Other symptom:Throughout these spasms, which can be extremely painful and even cause fractures, the patient remains mentally alert. The pulse is elevated and there is profuse perspiration.

20、Fever may or may not be present.DiagnosisDiagnosis of tetanus is based on the clinical picture associated with no prior history of immunization.The differential diagnosis can be difficult in early tetanus. Even with adequate treatment.TreatmentPatients require exquisite nursing care and should be mo

21、nitored. Initially therapy consist of administration of tetanus immune globulin(TIG), 500 to 10,000 units, as soon as the diagnosis is made. Currently most are treated in an intensive care unit on a respirator with paralytic drugs given to prevent muscle spasms. Mild cases can be treated with sedati

22、on, but most physicians administer muscle relaxants. Adequate doses of analgesics are required because of the pain associated with muscle spasms. Detailed attention must be given to care a paralyzed individual who is on a respirator. Adequate nutrition must be provided. Laxatives are generally indic

23、ated so that gastro-intestinal elimination can be facilitated. A urinary catheter should be provided. The patient will require eye protection to prevent desiccation. The wound must be treated to remove as much of the C. tetani and nonviolable tissue as possible. Debridement of all necrotic tissue sh

24、ould be done. Penicillin G should be administered to treat any bacteria that remain behind, but antibiotics are no substitute for good wound care.Prevention. Active immunization with tetanus toxoid (TD) is a safe and effective way of preventing tetanus. Unfortunately many children in the United Stat

25、es are not adequately vaccinated; immunization is also inadequate in many developing countries. One month after the diagnosis of tetanus is made, the patient should be begun on tetanus toxoid immunization. The dose of tetanus toxin mediated during an infection is so small that immunization does not

26、occur.BacteremiaBacteremia is defined as bacteria in the circulating blood with no indication of toxemia or other clinical manifestations. Bacteremia is usually transient and may last only a few moments, In toxemia, toxins are circulating in the blood, though the microorganism producing the toxin ne

27、ed not be. Toxemia is usually associated with infection by toxin-producing bacteria(e.g.,the clostridia of gas gangrene and the diphtheria bacillus), but this is not always so. For example, botulinum toxin or staphylococcal enterotoxin may have been ingested directly to cause a profound toxemia with

28、out true infection.SepticemiaSepticemia is a diffuse infection which infectious bacteria and their toxins are present in the bloodstream. Septicemia may arise directly from the introduction of infecting otganisms into the circulation but, as a rule, is secondary to a focus of infection within the bo

29、dy. The major routes by which bacteria reach the blood are (1) by direct extension and entrance into an open vessel. (2) by release of infected emboli following thrombosis of a blood vessel in an area of inflammation, (3) by discharge of infected lymph into the bloodstream following lymphangitis. Ma

30、ny specific diseases, e.g., typhoid fever and brucellosis, include a septicemic phase. In the absence of systemic disease, beta-hemolytic streptococci are most frequently responsible. Septicemia caused by alpha-hemolytic streptococci is usually a consequence of subacute bacteria endocarditis.The maj

31、ority of bacteria that produce suppurative lesions may give rise to secondary septicemia. Pyemia is septicemia in which pyogenicmicroorganisms, most notably staphylococcus aureus, and their toxins are carried in the bloodstream and sequentially initiate multiple focal abscess in many parts of the bo

32、dy. Before the advent of chemotherapy, staphylococcic pyemia was almost always fatal; the mortality is still high. ANTIMICROBIAL THERAPYThe use of antimicrobials in treating surgery infections does not differ fundamentally from antimicrobial usage in general medicine. The same basic considerations a

33、pply in treating all infections. One difference, however, is that antimicrobial therapy is only an adjunct in treating surgical infection; operative treatment is the main method of therapy. The goal of antomicrobial therapy is to prevent or treat infection by reducing or eliminating pathogenic organ

34、isms until the hosts own defenses can get rid of the last pathogens.The basic consideration in antimicrobial therapy are efficacy, toxicity,and cost. Effectiveness is the most important consideration in choosing antimicrobial therapy. Effective antimicrobial agents must be active against the pathoge

35、ns the infection and must be able to reach the site of infection in adequate concentrations. All antibiotics have potential toxicity. Toxic effects may be idiosyn-craticsuch as allergy or the rare instance of bone marrow aplasia caused by chloramphenicol or result in damage to tissue and organs as r

36、enal or ototoxicity seen with the aminoglycosides or amphotericin B. Antimicrobial agents also exert selective pressures on the microbial ecology of the hospital that lead to resistant microbes, a problem that can occur especially in intensive care unit settings.Cost is the final consideration in th

37、e selection of antimicrobial agents. Determining antimicrobial costs includes, nursing time, intravenous fluid and lines, and monitoring costs must also be added to drug costs. The increased hospital time that occurs when an inexpensive but also less effective agent is used should also be included i

38、n costs. Obviously an inexpensive agent that is not effective or that causes more toxicity ultimately becomes a more expensive antimicrobial.Distribution of Antimicrobial AgentsSuccessful treatment of localized infections with systemic antimicrobial agents requires that an adequate concentration of

39、drug be delivered tothe site of infection. Ideally the tissue concentration of antibiotics should exceed the minimum inhibitory concentration. Tissue penetration depends in part on protein binding of antibiotics. Only the unbound form of antibiotics will pass through the capillary wall or act to inh

40、ibit bacterial growth. Therapeutic outcome, on the other hand, appears uncorrelated with protein affinity, presumably because protein binding is easily reversible. Lipid solubility of antibiotics is also an important factor in tissue penetration. it determines the ability of antibiotics to pass thro

41、ugh membranes by nonionic diffusion or into wounds, bone, cerebrospinal fluid, the eye, endolymph of the ear, vegetation of bacterial endocarditis, and abscesses.Blood. Rapidity of excretion and protein binding are two main determinants of blood concentration of antimicrobial agents. Protein binding

42、 affects the rapidity of excretion. Antibiotics that are highly protein bound are not excreted as rapidly as those with a low binding affinity and thus have longer half-lives. Therefore, highly protein bound antibiotics generally do not have to be given as frequently as those with low protein bindin

43、g. Efficacy of penicillins, cephalosporins, and other antibiotics that affect bacterial cell wall synthesis depends on the time during which serum levels are above the minimum inhibitory concentra- tions rather than a peak serum concentration. Efficacy of aminoglycosides, on the other hand, is relat

44、ed to achieving peak serum concentrations that are four to eight times the minimum inhibitory concentration. Monitoring of serum aminoglycoside concentration is usually necessary to ensure that these concentration have been achieved; patients more commonly have subtherapeutic levels rather than toxi

45、c levels. On the other hand, some antimicro- bial agents such as nitrofurantoin and norfloxacin are rapidly in the urine that they never achieve blood levels sufficient to achieve effective antibacterial concentrations. They do, however, reach high urinary concentrations and are effective agents for

46、treating urinary tract infections.urine. Most commonly used antibiotics (sulfonamides, penicillins, cephalosporins, aminoglycosides, tetracyclines, quinolones, azoles) are excreted principally in the urine and achieve high urinary concentrationsup to 50to 200 times their serum concentration.Notable

47、exceptions are erythromycin and chloramphenicol. Since concentrating ability is severely compromised in patients with renal disease, infections of the urinary tract are more difficult to treat in these patients. The pH of urine can be changed to facilitate antibiotic activity. For instance aminoglyc

48、osides are more active in an alkaline medium, whereas other urinary antibacterial agents are more active in an acidic environment. Fortunately, the antimicrobials most commonly used to treat urinary tract infections have antimicrobial activity across a broad pH range.Bile. Besides urine, only bile r

49、egularly has concentra- tions of antibiotics higher than found in serum. The biliary concentrations of many of the penicillins especially nafcillin, piperacillin mezlocillin, and azlocillin; cephalosporins especially cefazolin, cefadroxil; tetracyclines; and clindamycin frequently are several times

50、their serum contractions. Nafcillin and rifampin achieve biliary concentrations 20 to 100times that of serum. Aminoglycoside antibioticsenter bile less well, especially in the presence of liver disease. Their biliary concentrations are usually lower than serum levels.Interstitial Fluid and Tissue. H

51、igh , prolonged serum concentration and low protein binding favor diffusion of antibiotics from serum into extra vascular tissue. Absolute tissue levels may not accurately reflect the therapeutic of the antibiotic, however, because the agent may be tightly bound to tissue and thus be unavailable for

52、 binding to bacteria.Abscesses. There are few date of clinical relevance concerning the distribution of antibiotics into abscesses. The generalization that no antibiotics penetrate abscesses is not true. While the penicillins, ephalosporins, and some other antibiotics penetrate mature abscesses poor

53、ly, others such as metronidazole, chloramphenicol, and clindamycin an achieve inhibitory concentrations in abscesses. A separate problem is whether, after penetration, antibiotic retain its antimicrobial efficacy under the conditions that exist in an abscess. The acidic pH, low redox potential, and

54、the large numbers of microbial and tissue products that can bind antibiotics all serve to reduce antimicrobial efficacy. Multiple types of bacteria within an abscess make it more likely that one type will inactivate an agent effective against it or another bacteria. The lack of efficacy of penicilli

55、ns and cephalosporins in treating most abscess may be due to high concentrations of betal lactamasesthat accumulate there.Metronidazole and clindamycin can both enter abscesses and retain antibacterial activity in such environments. but these antibiotics are not effective against the aerobic gram-ne

56、gative bacteria that are usually present together with the anaerobic bacteria against which they are effective, so the abscess usually persists. An additional reason that antibiotics alone are seldom effective in treating abscesses is that antibiotics are most effective against actively metabolizing

57、, rapidly dividing bacteria. Conditions in abscesses are usually unfavorable for such active metabolic activity, so the antibiotics is not able to enter and be active against the bacteria. For all these reasons antibiotics alone should not be relied on to treat most abscesses. Despite occasional rep

58、orts of success with such treatment, drainage remains the mainstay of abscess treatment.Use of Antibiotics in Surgery Prophylactic antibiotics. Antibiotics are frequently administered prophylactically to patients undergoing operation to prevent wound infection where the likelihood of infection is hi

59、gh (when the tissue have been exposed to bacteria such as occurs during colon surgery) or where the consequences of infection are great even though the risk of infection is low .Antibiotic prophylaxis should also be administered to many patients with previously placed prosthetic devices such as card

60、iac valves who are having operations or dental procedures.Therapeutic Use of Antibiotics. Many infections can be successfully treated with oral antibiotics on an outpatient basis. Severe surgical infections should be treated with intravenous antibiotics. Initial antibiotic therapy is usually empiric