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Asepsis, antisepsis and skin preparation
INFECTION IN SURGERY
Asepsis, antisepsis and skin preparation
Classification of wounds Classification Clean
Definition Infection rate of <2% Incision through non-inflamed tissue not entering a hollow viscus Clean-contaminated Infection rate of 10% Incision through a hollow viscus other than the colon with minimal contamination Contaminated Infection rate of 20% Incision into a hollow viscus with gross spillage or into colon Human/animal bite or open fracture Dirty Infection rate of 40% Faecal peritonitis, traumatic wound contaminated for 4 hours, frank pus
David Humes Dileep N Lobo
Antisepsis is the use of chemical solutions for disinfection; antisepsis does not imply sterility. Asepsis is the absence of infectious organisms. Aseptic techniques are those aimed at the minimization of all infectious micro-organisms during procedures.
Principles of asepsis and antisepsis Antisepsis and asepsis are practised in order to decrease the incidence of surgical wound infections. Postoperative wound infections are associated with considerable morbidity and mortality and also result in increased costs of health care. The risk of postoperative infection can be estimated by considering the type of surgical wound (Figure 1). A wound with purulent discharge and erythema is infected. Microbiological confirmation of the causative organism should be sought in order to direct therapy, but the diagnosis is clinical. The source of infection is exogenous (transmitted from another source) or endogenous (caused by the microbial flora of the patient). Endogenous flora can be classified as transient (isolated following exposure to a new microbial environment) or resident (isolated consistently from the person).
1
Preoperative preparation of skin with antiseptics (e.g. 10% aqueous povidine-iodine, 0.5% chlorhexidine in alcoholic or aqueous solution) is standard practice in the UK (see ‘Decontamination and sterilization’, page 282). Iodophores are highly complexed iodine molecules that have a sustained release, are non-staining and stable. These complexes are less irritating to the skin than iodine solutions. 0.5% chlorhexidine in alcoholic or aqueous solution kills transient flora and reduces resident flora and has more prolonged residual activity than iodophores. Both solutions are coloured, facilitating recognition of their application to the appropriate area. The solutions should be applied with a sponge from the area of incision outwards. The most heavily contaminated areas should be treated after clean areas. The contaminated sponge should be discarded. Pooling beneath the patient should be avoided in order to prevent burns if diathermy is used. If a stoma is present, it should be cleaned before skin preparation and covered with a sterile swab. The solution should be left to dry before draping. Sterile surgical drapes are used to isolate the prepared surgical site in order to create a sterile field. They create a barrier to the translocation of bacteria to the sterile area. Drapes can be reusable or disposable. Reusable drapes are made of cotton or cotton-polyester and are chemically treated. They reduce transmission from the skin below and protect against abrasion. They can be secured around the surgical site with non-penetrating clips. Disposable drapes are synthetic and offer a greater resistance to the penetration of microbes, but can be affected by volatile liquids and punctured by instruments. Adhesive operative drapes do not reduce wound infections, but allow for the securing of drapes around a site. Only the area of the drape above the operating table is sterile.
Factors contributing to asepsis in theatre Patient preparation: the bacterial flora of the patient is the principal source of infection in surgical wounds. Patient preparation begins with preoperative assessment. A focal source of sepsis should be treated before surgery, particularly if prosthetic implants are used. An infection developing after a 72-hour stay in hospital is termed ‘nosocomial’. Preoperative showering with an antiseptic solution has been shown to reduce wound infections in Sweden, but is not standard practice in the UK. The patient (wearing a clean gown) should be transferred in a clean bed or trolley to theatre. The surgical site should be shaved while the surgeon scrubs, and should be done by trained personnel in order to avoid skin abrasions. Shaving before transfer to theatre encourages colonization of skin abrasions with bacteria, increasing rates of wound infection; the use of electric clippers and depilation creams is associated with a decreased rate of wound infection.
Preparation of surgical instruments: surgical instruments used during surgical procedures are prepared by cleaning, disinfection and sterilization (see page 282).
David Humes is a Surgical Research Fellow at University Hospital, Queen’s Medical Centre, Nottingham, UK. Dileep N Lobo is a Senior Lecturer in Gastrointestinal Surgery and Honorary Consultant Hepatopancreaticobiliary Surgeon at University Hospital, Queen’s Medical Centre, Nottingham, UK.
SURGERY 23:8
Preparation of the surgeon Handwashing – preoperative washing from the fingertips to the 297
© 2005 The Medicine Publishing Company Ltd
INFECTION IN SURGERY
elbows using a bactericidal agent eliminates transient flora and reduces the resident flora on the surgeon’s hands. A brush should be used only on the fingernails and not the skin in order to avoid micro-trauma, which increases the number of surface bacteria. Brushing of the nails should be performed only once in a session. Nails should be short because long nails act as a reservoir for micro-organisms and increase the risk of glove puncture. There is no difference in infection rates between a scrub time of three minutes and five minutes. Chlorhexidine gluconate 4% (Hibiscrub™) with soap has a prolonged, cumulative effect; povidone-iodine liquid soap is more effective initially, but has a shorter duration of action. Alcohol-based solutions are as effective as a surgical scrub, but it is easy to miss some areas that should be included in the scrub. Some surgeons advocate a final rinse with alcohol following scrubbing. Gloves – the use of surgical gloves is an integral part of asepsis. Most surgical gloves are made of latex and are disposable. Alternatives are available for those with latex allergy. Studies suggest that between 50% and 70% of gloves are punctured, and of these 90% occur in operations lasting >2 hours. About 40,000 organisms can pass through a glove pinhole in twenty minutes. An increase in infection of clean wounds from 1.7% to 5.7% after a glove perforation has been shown. The left index finger is the most commonly punctured finger. Wearing two pairs of gloves affords greater protection to the surgeon. The introduction of indicator systems has further increased awareness of glove perforation. Masks, visors and hair cover – masks protect the surgeon. The filtering properties of masks decrease rapidly as they become increasingly moist. There is no evidence of increased wound infection in surgery carried out by surgeons without masks except in the presence of an infection of the upper respiratory tract (where bacterial numbers increase in the naso- and oro-pharynx). The use of a mask decreases bacterial numbers at the surgical site in surgery involving the use of prosthetic devices, but no correlation has been shown with wound infection. Masks with visors should be worn in order to prevent the spread of blood-borne viruses. Their use is particularly important in surgery in which fine sprays are produced. Hair should be completely covered. It is not a common source of infection, but the scalp can carry Staphylococcus aureus. Surgical gowns are made of polyester or polytetrafluoroethylene. A gown reduces the transmission of bacteria from the skin surface (‘strikethrough’). A 1-ply gown is used for surgery of short duration (<2 hours) and minimal blood loss (<100 ml). A 2-ply reinforced gown should be used for longer procedures (2–4 hours and 100–500 ml of blood loss) or surgery of the chest or abdominal cavity. An impervious gown should be used for longer operations. Gowns are sterile from the shoulders down to the level of the sterile field and from just below the elbows.
trolley. The walls and floor should be made of a robust material which is continuous and easy to clean. Joints should be amenable to cleaning. Adjustable lighting should be present. One of the key factors in postoperative wound infections is the number of bacteria in theatre air. Most of these bacteria are carried by theatre personnel. Ventilation systems filter and thus reduce bacterial load in the air and provide a positive pressure in order to prevent the entry of bacteria when the theatre door is opened. Air should be filtered through a 5 µm filter and cycled through theatre 20–25 times an hour in order to reduce bacterial flux. Air should flow across the operating table and be removed from theatre by an exhaust mechanism. In conventional theatres, the aim is to keep bacterial counts to <180 colony-forming units/m3. The theatre should be maintained at a positive pressure compared to the adjacent corridors. In orthopaedic theatres, the use of ultra-clean air systems (in which air is filtered through high-efficiency filters and directed down over the patient) is of paramount importance in reducing postoperative infection. This system can reduce bacterial load to <10 colony-forming units/m3, and allows a two- to fourfold reduction in postoperative infection. Turbulence is decreased further by limiting the number and movement of personnel in theatre and ensuring doors are closed. Surgical technique: poor handling of tissue and inadequate haemostasis result in devitalization of tissues and haematoma formation. Necrotic tissue and haematomas provide a medium for bacterial growth and increase rates of wound infection. Injudicious use of surgical drains can result in increased rates of wound infection. Prophylactic antibiotics (see page 290) should be given if wound contamination is anticipated. They are not advocated in clean procedures except for those in which prosthetic implants are used. The antibiotic chosen should have appropriate activity against the likely infecting pathogen. Intravenous dosing is advised to ensure good penetration of tissue. In general, antibiotics are given one hour before the procedure or 15 minutes before the induction of anaesthesia or inflation of tourniquets. A second dose should be given if a procedure lasts for >4 hours. No evidence exists to support the use of long-term prophylactic antibiotics and it is generally considered that no benefit is conferred after 48 hours.
Preparation of the operating theatre: theatres should be close to the Accident and Emergency Department, ITU and Radiology Department. Ideally, all should be on the same level. The theatre should have a double-door entrance to the anaesthetic room with a double-door exit to the corridor. A designated ‘dirty area’ should be present. A single entrance should connect the theatre to the scrub area. A clean preparation area and store should also be connected. The temperature should be regulated to between 19°C and 22°C and humidity to between 45% and 55%. The anaesthetic room should be stocked with working suction and a cardiac arrest
SURGERY 23:8
FURTHER READING Cruse P J, Foord R. The epidemiology of wound infection. A 10-year prospective study of 62,939 wounds. Surg Clin North Am 1980; 60: 27–40. Wiliams J D, Taylor E W (Editors). Infection in surgical practice. London: Arnold, 2003.
298
© 2005 The Medicine Publishing Company Ltd
Asepsis, antisepsis and skin preparation
Classification of wounds Classification Clean
Definition Infection rate of <2% Incision through non-inflamed tissue not entering a hollow viscus Clean-contaminated Infection rate of 10% Incision through a hollow viscus other than the colon with minimal contamination Contaminated Infection rate of 20% Incision into a hollow viscus with gross spillage or into colon Human/animal bite or open fracture Dirty Infection rate of 40% Faecal peritonitis, traumatic wound contaminated for 4 hours, frank pus
David Humes Dileep N Lobo
Antisepsis is the use of chemical solutions for disinfection; antisepsis does not imply sterility. Asepsis is the absence of infectious organisms. Aseptic techniques are those aimed at the minimization of all infectious micro-organisms during procedures.
Principles of asepsis and antisepsis Antisepsis and asepsis are practised in order to decrease the incidence of surgical wound infections. Postoperative wound infections are associated with considerable morbidity and mortality and also result in increased costs of health care. The risk of postoperative infection can be estimated by considering the type of surgical wound (Figure 1). A wound with purulent discharge and erythema is infected. Microbiological confirmation of the causative organism should be sought in order to direct therapy, but the diagnosis is clinical. The source of infection is exogenous (transmitted from another source) or endogenous (caused by the microbial flora of the patient). Endogenous flora can be classified as transient (isolated following exposure to a new microbial environment) or resident (isolated consistently from the person).
1
Preoperative preparation of skin with antiseptics (e.g. 10% aqueous povidine-iodine, 0.5% chlorhexidine in alcoholic or aqueous solution) is standard practice in the UK (see ‘Decontamination and sterilization’, page 282). Iodophores are highly complexed iodine molecules that have a sustained release, are non-staining and stable. These complexes are less irritating to the skin than iodine solutions. 0.5% chlorhexidine in alcoholic or aqueous solution kills transient flora and reduces resident flora and has more prolonged residual activity than iodophores. Both solutions are coloured, facilitating recognition of their application to the appropriate area. The solutions should be applied with a sponge from the area of incision outwards. The most heavily contaminated areas should be treated after clean areas. The contaminated sponge should be discarded. Pooling beneath the patient should be avoided in order to prevent burns if diathermy is used. If a stoma is present, it should be cleaned before skin preparation and covered with a sterile swab. The solution should be left to dry before draping. Sterile surgical drapes are used to isolate the prepared surgical site in order to create a sterile field. They create a barrier to the translocation of bacteria to the sterile area. Drapes can be reusable or disposable. Reusable drapes are made of cotton or cotton-polyester and are chemically treated. They reduce transmission from the skin below and protect against abrasion. They can be secured around the surgical site with non-penetrating clips. Disposable drapes are synthetic and offer a greater resistance to the penetration of microbes, but can be affected by volatile liquids and punctured by instruments. Adhesive operative drapes do not reduce wound infections, but allow for the securing of drapes around a site. Only the area of the drape above the operating table is sterile.
Factors contributing to asepsis in theatre Patient preparation: the bacterial flora of the patient is the principal source of infection in surgical wounds. Patient preparation begins with preoperative assessment. A focal source of sepsis should be treated before surgery, particularly if prosthetic implants are used. An infection developing after a 72-hour stay in hospital is termed ‘nosocomial’. Preoperative showering with an antiseptic solution has been shown to reduce wound infections in Sweden, but is not standard practice in the UK. The patient (wearing a clean gown) should be transferred in a clean bed or trolley to theatre. The surgical site should be shaved while the surgeon scrubs, and should be done by trained personnel in order to avoid skin abrasions. Shaving before transfer to theatre encourages colonization of skin abrasions with bacteria, increasing rates of wound infection; the use of electric clippers and depilation creams is associated with a decreased rate of wound infection.
Preparation of surgical instruments: surgical instruments used during surgical procedures are prepared by cleaning, disinfection and sterilization (see page 282).
David Humes is a Surgical Research Fellow at University Hospital, Queen’s Medical Centre, Nottingham, UK. Dileep N Lobo is a Senior Lecturer in Gastrointestinal Surgery and Honorary Consultant Hepatopancreaticobiliary Surgeon at University Hospital, Queen’s Medical Centre, Nottingham, UK.
SURGERY 23:8
Preparation of the surgeon Handwashing – preoperative washing from the fingertips to the 297
© 2005 The Medicine Publishing Company Ltd
INFECTION IN SURGERY
elbows using a bactericidal agent eliminates transient flora and reduces the resident flora on the surgeon’s hands. A brush should be used only on the fingernails and not the skin in order to avoid micro-trauma, which increases the number of surface bacteria. Brushing of the nails should be performed only once in a session. Nails should be short because long nails act as a reservoir for micro-organisms and increase the risk of glove puncture. There is no difference in infection rates between a scrub time of three minutes and five minutes. Chlorhexidine gluconate 4% (Hibiscrub™) with soap has a prolonged, cumulative effect; povidone-iodine liquid soap is more effective initially, but has a shorter duration of action. Alcohol-based solutions are as effective as a surgical scrub, but it is easy to miss some areas that should be included in the scrub. Some surgeons advocate a final rinse with alcohol following scrubbing. Gloves – the use of surgical gloves is an integral part of asepsis. Most surgical gloves are made of latex and are disposable. Alternatives are available for those with latex allergy. Studies suggest that between 50% and 70% of gloves are punctured, and of these 90% occur in operations lasting >2 hours. About 40,000 organisms can pass through a glove pinhole in twenty minutes. An increase in infection of clean wounds from 1.7% to 5.7% after a glove perforation has been shown. The left index finger is the most commonly punctured finger. Wearing two pairs of gloves affords greater protection to the surgeon. The introduction of indicator systems has further increased awareness of glove perforation. Masks, visors and hair cover – masks protect the surgeon. The filtering properties of masks decrease rapidly as they become increasingly moist. There is no evidence of increased wound infection in surgery carried out by surgeons without masks except in the presence of an infection of the upper respiratory tract (where bacterial numbers increase in the naso- and oro-pharynx). The use of a mask decreases bacterial numbers at the surgical site in surgery involving the use of prosthetic devices, but no correlation has been shown with wound infection. Masks with visors should be worn in order to prevent the spread of blood-borne viruses. Their use is particularly important in surgery in which fine sprays are produced. Hair should be completely covered. It is not a common source of infection, but the scalp can carry Staphylococcus aureus. Surgical gowns are made of polyester or polytetrafluoroethylene. A gown reduces the transmission of bacteria from the skin surface (‘strikethrough’). A 1-ply gown is used for surgery of short duration (<2 hours) and minimal blood loss (<100 ml). A 2-ply reinforced gown should be used for longer procedures (2–4 hours and 100–500 ml of blood loss) or surgery of the chest or abdominal cavity. An impervious gown should be used for longer operations. Gowns are sterile from the shoulders down to the level of the sterile field and from just below the elbows.
trolley. The walls and floor should be made of a robust material which is continuous and easy to clean. Joints should be amenable to cleaning. Adjustable lighting should be present. One of the key factors in postoperative wound infections is the number of bacteria in theatre air. Most of these bacteria are carried by theatre personnel. Ventilation systems filter and thus reduce bacterial load in the air and provide a positive pressure in order to prevent the entry of bacteria when the theatre door is opened. Air should be filtered through a 5 µm filter and cycled through theatre 20–25 times an hour in order to reduce bacterial flux. Air should flow across the operating table and be removed from theatre by an exhaust mechanism. In conventional theatres, the aim is to keep bacterial counts to <180 colony-forming units/m3. The theatre should be maintained at a positive pressure compared to the adjacent corridors. In orthopaedic theatres, the use of ultra-clean air systems (in which air is filtered through high-efficiency filters and directed down over the patient) is of paramount importance in reducing postoperative infection. This system can reduce bacterial load to <10 colony-forming units/m3, and allows a two- to fourfold reduction in postoperative infection. Turbulence is decreased further by limiting the number and movement of personnel in theatre and ensuring doors are closed. Surgical technique: poor handling of tissue and inadequate haemostasis result in devitalization of tissues and haematoma formation. Necrotic tissue and haematomas provide a medium for bacterial growth and increase rates of wound infection. Injudicious use of surgical drains can result in increased rates of wound infection. Prophylactic antibiotics (see page 290) should be given if wound contamination is anticipated. They are not advocated in clean procedures except for those in which prosthetic implants are used. The antibiotic chosen should have appropriate activity against the likely infecting pathogen. Intravenous dosing is advised to ensure good penetration of tissue. In general, antibiotics are given one hour before the procedure or 15 minutes before the induction of anaesthesia or inflation of tourniquets. A second dose should be given if a procedure lasts for >4 hours. No evidence exists to support the use of long-term prophylactic antibiotics and it is generally considered that no benefit is conferred after 48 hours.
Preparation of the operating theatre: theatres should be close to the Accident and Emergency Department, ITU and Radiology Department. Ideally, all should be on the same level. The theatre should have a double-door entrance to the anaesthetic room with a double-door exit to the corridor. A designated ‘dirty area’ should be present. A single entrance should connect the theatre to the scrub area. A clean preparation area and store should also be connected. The temperature should be regulated to between 19°C and 22°C and humidity to between 45% and 55%. The anaesthetic room should be stocked with working suction and a cardiac arrest
SURGERY 23:8
FURTHER READING Cruse P J, Foord R. The epidemiology of wound infection. A 10-year prospective study of 62,939 wounds. Surg Clin North Am 1980; 60: 27–40. Wiliams J D, Taylor E W (Editors). Infection in surgical practice. London: Arnold, 2003.
298
© 2005 The Medicine Publishing Company Ltd