Surgical Infection General Principles PDF

infections , general principles Dr Abdel maged Elosta Consultant surgeon T.M.C Faculty of Medicine , Surgical Department University of Tripoli - Contamination is the mere presence of micro- organisms in a wound. - infection , when these organisms invade the tissues, and pro...

infections , general principles Dr Abdel maged Elosta Consultant surgeon T.M.C Faculty of Medicine , Surgical Department University of Tripoli - Contamination is the mere presence of micro- organisms in a wound. - infection , when these organisms invade the tissues, and produce ill effects (inflammation). Pathogenesis - The development of infection depends on interaction between an infectious bacteria and a susceptible host. The infectious bacteria: - I - Endogenous bacteria , Different areas in the body possess characteristic microflora :- Examples include ❑ The skin possesses Gram-positive organisms as staphylococci and streptococci. ❑ These organisms cause infection of traumatic lacerations or surgical wounds. ❑ In the gastrointestinal tract , Gram negative resident floras of aerobic and anaerobic organisms are found in the oropharynx , colon and rectum. II – Exogenous agents , Most important exogenous sources are those within the hospitals and are responsible for hospital-acquired infections. - Sources include other patients , medical staff members and defects in sterilization systems. Host reaction , the host's immune mechanisms include : - Non-specific immunity , Phagocytic leucocytes carry out this function. - Uncontrolled Diabetes , corticosteroids and malnutrition impair this function > ↓ immunity. Specific immunity , This is carried out by specific antibodies produced on previous exposure to antigen with subsequent activation of T and B-lymphocytes. - Defects in specific immunity are seen in patients on immunosuppressive therapy and in AIDS patients  Bacteriology Staphylococci , These are the commonest organisms seen clinically , They are Gram positive cocci that live in the skin including sebaceous and sweat glands , and in the nostrils in about 25-50 % of normal adults. - Staph. aureus infection gives rise to acute abscesses , boils and carbuncles. - Its also the commonest cause of osteomyelitis and is commonly seen in infected surgical wounds. - Some strains also produce the enzyme penicillinase so called methicillin resistant Staph aureus (MRSA) , which pose a serious Problem , particularly with hospital-acquired infections. - Most of such strains are sensitive to vancomycin. Streptococci , These are Gram-positive organisms that grow in chains , There are mainly two types of streptococci , the hemolytic and non-hemolytic. - Hemolytic streptococci are the more virulent and are often present in the nasopharynx. - They are readily transmissible by droplet infection and can cause spreading infections such as cellulitis, lymphangitis and erysipelas.  Aerobic Gram-negative bacilli o - Escherichia coli (E. coli) are found in the intestinal tract of all human beings , Many varieties are non-pathogenic under ordinary conditions , E. coli are responsible , either alone or in mixed infection , for the majority of suppurative lesions within the Abdomen. o - Klebsiella , This organism represents a special variety of encapsulated gram negative bacilli , They are found in the respiratory tract and can cause fatal pneumonia in debilitated patients. o - Pseudomonas aeroginosa is present in human faeces in 20 percent of cases , Its recognized by its specific blue-green colour of pus and its odour , Once introduced into a ward , pseudomonas is very difficult to eradicate.  Anaerobic bacteria , Obligatory anaerobes , chiefly gram negative bacilli (bacteroides) , are part of the normal flora of the skin and mucous membranes. - When the epithelial barrier is disrupted , these organisms invade tissues and produce abscesses or enter the blood stream and cause septicaemia , These abscesses are characterized by gas formation , tissue necrosis and foul smelling discharge. - Aerobic cultures fail to grow these organisms. - Postoperative anaerobic wound infection usually follows operations on the colon or oral cavity.  Spread of infection o - Direct spread , Necrotizing fasciitis , for example , spreads along poorly perfused fascia , and subcutaneous planes. 0 - Lymphatic spread , Streptococcal and staphylococcal infections spread along lymphatic vessels producing lymphangitis with characteristic red streaks in the skin that travel proximally to lymph nodes. o - Blood stream spread , This may result in distant abscesses (pyaemic abscesses). Diagnosis - Clinical evaluation of infections : - o - Locally the inflamed area is painful , reddness , edematous , hottness and tenderness. The draining lymph nodes may be enlarged , painful and tender. o - Constitutional symptoms include fever , headache , malaise , and tachycardia , tachypnea , Dyspnea and rigors may occur in severe cases with septicaemia.  Laboratory studies : - - Leucocytosis with granulocytes (shift to the left) indicates pyogenic infection. - Inflammation markers as erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP 1-3 mg/dl) are elevated with any inflammation , They are non-specific , but are used to monitor progress of inflammation. - ESR …. 0-15 mm/hr. - Bacterial culture and antibiotic sensitivity direct treatment , The test is done either for pus discharge , urine or sputum , The patient should not be on antibiotics for 3 days before the sample is taken. - Blood cultures are essential in serious infections , Usually three blood samples from different veins are taken over 24-hours period. - The blood is used for aerobic and anaerobic cultures. Imaging studies - Plain X-Ray for pulmonary infections , subphrenic abscess (elevated immobile cupula of the diaphragm) and osteomyelitis. - Other imaging studies , such as ultrasonography , CT scanning and radionuclide scans are helpful in localizing deep-seated infections. Principles of treatment - Abscess , The treatment of an abscess is by drainage of pus , In the majority of cases making an incision , the so-called incision and drainage operation. - Percutaneous drainage , In a few situations drainage is achieved by needle aspiration or by percutaneous placement of a fine catheter. An examples is brain abscess , in order to avoid damaging irreparable neural tissue , Intra-abdominal abscesses can be drained by inserting a catheter , and then directing it under ultrasound or CT guidance into the abscess cavity.  - Spreading infections as cellulitis and erysipelas are treated by antibiotics. - Some surgical infections require excision , e.g., an infected appendix , gas gangrene and necrotizing fasciitis. - General supportive measures as control of diabetes , limb revascularization in cases of ischaemia, and nutritional support.  CELLULITIS - Its the non-suppurative , invasive infection of the skin and subcutaneous tissues. - Infection may follow a small scratch or wound or incision or insect/snake/scorpion bite. - It can be superficial or deep. More common superficial type is easier to diagnose. - Its common in diabetics , immunosuppressed people and old age. - Its common in face, lower limb, upper limb and scrotum wherein subcutaneous tissue is lax. Cellulitis face. Note the oedema of the face and eyelids. Oedema gives rise to soft pitting , while if pus present , induration can always be felt.  Pathology - Commonly due to Streptococcus pyogenes and other Gram +ve organisms. Release of streptokinase and hyaluronidase cause spread of infection. - Often Gram –ve organisms like Klebsiella , Pseudomonas , E. coli are also involved (usually Gram -ve organisms cause secondary infection).  Complications - Infection can get localised to form pyogenic abscess. - Infection can spread to cause bacteraemia, septicaemia , pyaemia. - Often infection can lead to local gangrene. - Extensive necrosis of skin and subcutaneous tissue necrotizing fasciitis.  Clinical Features - Localized Hotness , redness , tenderness , Swelling is diffuse and spreading in nature. - Fever, toxicity (tachycardia, tachypnea , hypotension) , Pain and, shiny area with stretched warm skin. - Cellulitis will progress rapidly in diabetic and immunosuppressed individuals. - Tender regional lymph nodes may be palpable which signify severity of the infection. - No edge ; no pus ; no fluctuation.  Investigations - Total WBC count raises , differential count. - Liver function tests , blood urea and serum creatinine in severe cases. - Blood sugar estimation , urine test for ketone bodies , glycosylated haemoglobin estimation HBA1c. - Deep vein thrombosis (DVT) often may mimic cellulitis of lower limb. Venous Doppler and ultrasound of soft tissues of the limb may require in such situation.  Treatment Antibiotics (penicillin group). Rest and elevation of the affected part. Warm packs. Note : - If no response has occurred within 48 hours , either an abscess has developed , or resistant organisms as staphylococci are involved , change the Antibiotics— penicillins to cephalosporins.  ERYSIPELAS - Erysipelas is an acute spreading inflammation of the upper (outer) dermis and superficial lymphatics ; it has got typical skin rash presenting on legs , toes , face and fingers due to acute infection by beta haemolytic Streptococcus pyogenes. - presenting as raised well demarcated skin rash (rash is due to exotoxin). Its more superficial than cellulitis , more common in face and legs. - Infection occurs through a minor trauma , Its affects all races ; more common in females , There will be always cutaneous lymphangitis with development of rose pink rash with cutaneous lymphatic oedema.  Clinical features Fever , malaise and loss of appetite. Locally the picture is similar to cellulitis , but there are some differences : - - The skin is rose-pink. - The edge is well-defined , slightly raised and often shows minute vesicles just beyond the spreading margin. - There may be islets of inflammation beyond the spreading margin separated from the main area by apparently normal skin. - Tender , regional lymph nodes are usually palpable.  Complications Facial erysipelas may lead to cavernous sinus thrombosis. Septicaemia and septic shock. Recurrent erysipelas may block the lymphatics leading to elephantiasis. Differential diagnoses : - herpes zoster , contact dermatitis.  Treatment - Like cellulitis , treatment is by antibiotics , mainly penicillins , cephalosporins. - Commonly effective treatment requires intravenous administration.  Acute abscess - An abscess is a localized suppurative inflammation. Bacteria Causing Abscess ❑ - Staphylococcus aureus. ❑ - Streptococcus pyogenes. ❑ - Gram-negative bacteria (E. coli , Pseudomonas , Klebsiella). ❑ - Anaerobes. The commonest causative organisms are staphylococci that produce a coagulase enzyme which helps localize the acute inflammatory processes. Multiple abscesses in neck , chin , face. It is common in HIV , diabetes and immunosuppressed. Abscess in the nape of the neck—suboccipital region. Note the redness and visible pus. Patient is diabetic.  Pathogenesis The organisms reach the tissues by Direct access. through wounds , scratches , and abrasions , or along natural passages such as lactiferous ducts. Local extension , from an adjacent focus , e.g. osteomyelitis of the jaw from an infected tooth. Lymphatic spread , Infection reaches the regional lymph nodes along lymphatics from a septic focus in their drainage area. Blood spread , Organisms gaining access into the circulation , as in bacteraemia or pyaemia , may lodge in distant tissues and cause abscesses , e.g. pyaemic liver, and lung abscesses.  Pathology An abscess consists , of‘ three zones : - A central 'zone"of coagulative necrosis. This ultimately separates ·from surrounding tissues and forms a slough which becomes liquefied by the enzymes of dead leucocytes. The resulting opaque fluid is called pus and is composed of inflammatory exudate , dead WBC , necrotic tissue and dead and living organisms. An intermediate zone of granulation tissue forms a protective layer against the spread of bacteria and their toxins. A peripheral zone of acute inflammation fades gradually into healthy surrounding tissues.  Fate - Pointing and rupture is the commonest sequel. The abscess discharges its pus along the plane of least resistance. - Spread of infection either locally, by lymphatics, or by blood stream. - Chronicity (more than 2 weeks ), A dense fibrous tissue reaction forms around the incompletely resolved abscess leading to the formation of a mass with little inflammatory reaction around. - This mass occurs when an abscess is treated by a prolonged course of antibiotics or if inadequately drained , called antibioma.  Clinical Features Fever often with chills and rigors. Localised swelling which is smooth , soft and fluctuant , Visible (pointing) pus. Throbbing pain and pointing tenderness. Redness and warmth with restricted movement around a joint. Rubor (redness) ; dolor (pain) ; calor (warmness) ; tumour (swelling) and functiolaesa (loss of localised and adjacent tissue/joint function) are quiet obvious. (Commonly cellulitis occurs first which eventually gets localised to form an abscess.) - fluctuation test are the features of formed abscess.  Sites of Abscess a. External Sites - Fingers and hand , Neck , Axilla , Breast. - Foot , thigh — here it’s a deeply situated with brawny induration , Ischiorectal and perianal region. - Abdominal wall. - Dental abscess , tonsillar abscess and other abscesses in the oral cavity. b. Internal Abscess - Abdominal : Subphrenic , pelvic , paracolic , amoebic liver abscess , pyogenic abscess of liver , splenic abscess , pancreatic abscess , Perinephric abscess. - Retroperitoneal abscess , Lung abscess. - Brain abscess , Retropharyngeal abscess.  Investigations - Total WBC count is increased. - Urine sugar and blood sugar FBS is done to rule out diabetes. - USG of the part or abdomen or other region is done when required. - CT scan or MRI is done in cases of brain and thoracic abscess. - Investigations , relevant to specific types : - Liver function tests LFT , PO2 and PCO2 estimation , blood culture.  an Complications of an abscess Bacteraemia , septicaemia , and pyaemia. Multiple abscess formation. Metastatic abscess. Destruction of tissues. Antibioma formation (common in breast abscess) hard swelling which may mimic breast carcinoma. Sinus and fistula formation. Large abscess may erode into adjacent vessels and can cause lifethreatening torrential haemorrhage, e.g. as in pancreatic abscess. Abscess in head and neck region can cause laryngeal oedema , stridor and dysphagia.  Treatment of an Abscess Note: Pus anywhere in the body will come to the surface , pus anywhere should be drained. “Pus is like the truth , you have to let it out. Procedure Hilton’s method of draining an abscess. Initially broad spectrum antibiotics are started (depending on severity , extent and site of the abscess). Under general anaesthesia or regional block anaesthesia , after cleaning and draping , abscess is aspirated and presence of pus is confirmed.  Skin is incised adequately , in the line parallel to the neurovascular bundle in the most dependent position. Next , pyogenic membrane is opened using Sinus forceps , and all loculi are broken up. Abscess cavity is cleared of pus and washed with saline. A drain (either gauze drain or corrugated rubber drain) is placed. Wound is not closed. Wound is allowed to granulate and heal. Pus is sent for culture and sensitivity.  Ludwig’s Angina (Wilhelm Frederick von Ludwig in 1836) Its a rapidly progressive polymicrobial cellulitis of the sublingual and submandibular spaces involving the floor of the mouth and suprahyoid area on both sides of the neck. Commonest cause is dental infection of 2nd or 3rd molar teeth precipitated by tooth extraction ; other causes are submandibular sialadenitis , trauma , peritonsillar abscess , upper respiratory infection , interventions like endotracheal intubation.  Predisposing factors are > diabetes mellitus , chemotherapy , oral cancer , alcohol , neutropenia. Commonest organisms are > Streptococcus viridians , Staphylococcus aureus and anaerobes. Gram negative organisms can also be involved. Cellulitis may extend into the pharyngomaxillary space , retropharynx , and superior mediastinum.  Features Diffuse painful swelling with woody brawny induration of the mouth and anterior neck , Swelling is non-fluctuant but with redness and tenderness. Bilateral submandibular oedema with marked tenderness on palpation at suprahyoid area with bull’s neck appearance. Toxic features like fever , tachycardia , tachypnoea is common. Difficulty in speech , earache , drooling of saliva. Involvement of connective tissues , muscles and fascial spaces but not glandular structures. Spread via fascial planes in continuity not by lymphatics ; no lymph node enlargement.  Oedema of the tongue with pushing against palate (elevation) upwards and backwards causing airway obstruction , dysphagia and odynophagia. Stridor , respiratory distress and cyanosis may develop due to oedema of tongue and larynx. Investigations CT scan or MRI U/S is useful to identify airway block , fluid collection and presence of gas. Total WBC count , blood sugar , chest X-ray and ABG (in severe cases) is done.  Differential diagnoses angioneurotic oedema , sublingual haematoma , sialadenitis , lymphadenitis. Complications Laryngeal oedema can occur due to spread of inflammation to glottis submucosa via stylohyoid tunnel , It may require emergency tracheostomy to maintain the respiration. Mediastinitis due to spread of infection into mediastinum ; aspiration pneumonia , Septicaemia. Spread of infection into the parapharyngeal space leads to thrombosis of the internal jugular vein which may extend above into the sigmoid sinus which may be fatal , Mortality is less than 5% unlike in olden days.  Treatment Antibiotics (intravenous) like penicillins , piperazillin , tazobactam , clindamycin , metronidazole should be started at the earliest. If patient is in respiratory distress , tracheostomy is required as a life saving procedure. Whenever distress is severe surgical decompression is required. Initial steroid therapy (dexamethasone) may be beneficial and is often used to reduce oedema even though its controversial.  ‫شكرا جزيال ألهتمامكم‬ Thanks a lot for your attention.