1、BAILY LOVE TEXTBOOK OF SURGERY0 INDEX 87. Wound infection DAVID J. LEAPERPhysiology and manifestationBackground. It is clear that the Egyptians knew about infection. They certainly were able to prevent putrefaction which is testified in their skills of mummification. Their medical papyruses also des
2、cribe the use of salves and antiseptics to prevent wound infections. This had also been known, although less well documented, by the Assyrians and the Greeks, particularly in Hippocratic teachings, which had refined the use of antimicrobial practice. The use of wine and vinegar to irrigate open infe
3、cted wounds before successful secondary closure was practised widely. Common to all these cultures, and the later Roman practitioners, was a dictum that whenever pus developed in an infected wound it needed to be drained.Galen recognised that localisation of infection (suppuration) in wounds inflict
4、ed in the gladiatorial arena often heralded recovery, particularly after drainage of the pus (pus bonum et Iaudabile). Sadly, this dictum was misinterpreted by many until well into the Renaissance; many practitioners actually promoted suppuration in wounds by application of many noxious substances,
5、including faeces, in the misbelief that healing could not occur without pus formation. There was occasional light in this long, dark tunnel: Theodoric of Cervia, Ambroise Pare and Guy de Chauliac all realised that clean wounds, closed primarily, could heal without infection or suppuration.The unders
6、tanding of the causes of infection came in the nineteenth century Microbes had been seen under the microscope, but Koch laid down the first definition of infective disease (Kochs postulates). These were basically that a particular microbe could be considered responsible for an infection when it was
7、found in adequate numbers in a septic focus, could be cultured in pure form from specimens taken from the focus and could cause similar lesions when injected into another host.The Austrian obstetrician, Ignac Semmelwe is, showed that maternal mortality caused by puerperal sepsis could be reduced fro
8、m over 10 per cent to under 2 per cent by the simple act of hand washing between postmortem examinations and the delivery suite.Louis Pasteur recognised that microorganisms spoilt wine and Joseph Lister applied this knowledge to the reduction of organisms in compound fractures allowing surgery witho
9、ut infection. However, his toxic phenol spray and principles of antiseptic surgery soon gave way to aseptic surgery at the turn of the century a technique still employed in modern operating theatres.The concept of a magic bullet which could kill microbes but not their host led to early sulphonamide
10、chemotherapy.The antibiotic penicillin, the discovery of which is ascribed to Alexander Fleming, was isolated by Florey and Chain. The first patient to receive penicillin was Police Constable Alexander, who had a severe staphylococcal illness. He made a partial recovery before the penicillin ran out
11、 but later relapsed and died. Since then there has been a huge increase in antibiotic groups with improved antibacterial spectra. Few staphylococci are now sensitive to penicillin but streptococcal illnesses respond, although they are seen increasingly rarely in surgical practice. Many bacteria deve
12、lop resistance through the acquisition of beta-lactamases which can break up the 3-lactam ring, common in the formula of many antibiotics. In general surgery, the synergy of aerobic Gram-negative bacilli with anaerobic Bacteroides spp. presents the most challenging infection. Wide-spectrum antibioti
13、cs can be given empirically to treat such infections, or more specific, narrow-range antibiotics given based on culture and sensitivity. The range of surgery now practised owes much to rational antibiotic use faecal peritonitis may not be considered to be lethal, and wounds made in the presence of s
14、uch contamination can heal primarily without infection in 8090 per cent of patients. Patients undergoing prosthetic surgery or who are immunosuppressed can be spared infection in their wounds by the appropriate use of prophylactic antibiotics.PhysiologyBacteria are normally prevented from causing in
15、fection in tissues by intact epithelial surfaces, but these are broken down by surgery. In addition to this mechanical barrier, there are other protective mechanisms, i.e. chemical (such as the low gastric pH), humoral (antibodies, complement and opsonins) and cellular (phagocytic cells, macrophages
16、, polymorphonuclear cells and killer lymphocytes).Host response is weakened by malnutrition which may present as obesity as well as recent rapid weight loss (Table 7.1) Metabolic diseases, diabetes mellitus, uraemia and jaundice may weaken defences, and disseminated cancer may also be included toget
17、her with immunosuppression caused by radiotherapy, chemotherapy, steroids and acquired immunodeficiency syndrome (AIDS) (Fig 7.1 and Fig 7.2).When enteral feeding is suspended in the perioperative period, the gut rapidly becomes colonised and bacteria, particularly Gram-negative bacilli, translocate
18、 to mesentericnodes. Release of endotoxin may follow, which further increases susceptibility to infection. In these circumstances, nonpathogens become important (opportunism).The pathogenicity and size of bacterial inoculum also relates to the chance of developing an established wound infection afte
19、r surgery. Poor surgical technique that leaves devitalised tissue, excessive dead space or haematoma may increase this risk. Foreign materials of any kind, including sutures and drains, promote infection. A logarithm reduction in the number of organisms is needed to cause a wound infection in the pr
20、esence of a silk suture. These factors need consideration in prosthetic orthopaedic and vascular surgery.In the first 4 hours after a breach in an epithelial surface and underlying connective tissues made during surgery or trauma, there is a delay before host defences can become mobilised through ac
21、ute inflammatory, humoral and cellular processes. This period is called the decisive period and it is during these first 4 hours after incision that bacterial colonisation and established infection can begin. It is logical that prophylactic antibiotics will be most effective during this time.Local a
22、nd systemic manifestationInfection of a wound can be defined as the invasion of organisms through tissues following a breakdown of local and systemic host defences. Sepsis is the systemic manifestation of a documented infection, the signs and symptoms of which may also be caused by multiple trauma,
23、burns or pancreatitis. Bacteraemia should not be confused with this systemic inflammatory response syndrome (SIRS) although the two may coexist (see Table 7.2). Septic manifestations are mediated by release of cytokines such as interleukins (IL) and tumour necrosis factor (TNF) and other modules fro
24、m polymorphonuclear and phagocytic cells and, in its most severe form, presents as multiple system organ failure (MSOF). Infection may cause SIRS through the release of lipopolysaccharide endotoxin from the walls of dying Gram-negative bacilli (mainly Escherichia coli) and other toxins, which in tur
25、n causes release of cytokines (Fig. 7.3). A reduced defence to wound infection follows.Pathogens resist host defences by release of toxins, particularly in unfavourable anaerobic conditions, which favours their spread in wound infections. Clostridium perfringens, which is responsible for gas gangren
26、e, releases many spreading proteases such as hyaluronidase, lecithinase and haemolysin. Many resistant pathogens can produce beta-lactamases which destroy the beta lactam ring of antibiotics. This resistance can be acquired and passed on through plasmids.The human body harbours approximately 1014org
27、anisms. They are released into tissues by surgery, contaminationbeing most severe when a hollow viscus is opened (e.g. colorectal surgery). Any infection which follows may be termed primary, community acquired or endogenous. Exogenous infections are usually hospital acquired (nosocomial) and are sec
28、ondary, being introduced into the tissues after surgery not during it, unless introduced via inadequately filtered air in the operating theatre.A major wound infection is defined as a wound which discharges pus and may need a secondary procedure to be sure of adequate drainage (Fig. 7.4). There may
29、be systemic signs of tachycardia pyrexia and a raised white count (SIRS). The patient may be delayed in returning home beyond the planned day. Minor wound infections may discharge pus or infected serous fluid but should not be associated with excessive discomfort, systemic signs or delay in return h
30、ome (Fig. 7.5).The differentiation of major and minor wound infection is important in audit trials of antibiotic prophylaxis and is of relevance to league tables of hospital infection as major wound infections must be accounted for.Types of infection Wound abscessA wound abscess presents all the Cel
31、sian clinical features of acute inflammation: calor(heat), rubor (redness), dolor (pain)and tumour(swelling),towhich can be added functio leasa (loss of function ) .it hurts the infected part is not used). Pyogenic organisms, predominantly Staphylococcus aureus, cause tissue necrosis and suppuration
32、. Pus is also composed of dead and dying white blood cells which release damaging cytokines, oxygen-free radicals and other molecules. An abscess is surrounded by an acute inflammatory response, and a pyogenic membrane composed of fibrinous exudate and oedema, and the cells of acute inflammation. Gr
33、anulation tissue (macrophages, angiogenesis and fibrobbasts) forms later around the suppuration and beads to collagen deposition. If excessive or partly sterilised by antibiotics (antibioma), a chronic abscess may result. Abscesses usually track along planes of least resistance and point towards the skin. Wound absces
