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Airborne infection in surgery
Journal of Hospital Infection (1982) 3, 215-216
Editorial Airborne
infection
in surgery
The relative roles of airborne and contact spread of staphylococci to operation wounds remain uncertain. Evidence on this subject, which is often controversial, is reviewed in a special article in this issue. A recent large MRC trial on hip and knee joint prosthetic surgery demonstrated that airborne spread was apparently responsible for a small but clinically significant number of septic wounds which could be reduced by operating in ‘ultraclean’ air (Lidwell et al., 1982). Whyte, Hodgson and Tinkler (1982) also showed that most of the infections in their study on similar operations were probably due to airborne spread, and the organisms causing infection were mainly normal skin flora (Staphylococcus epidermidis and diphtheroids). In other types of surgery, particularly abdominal, the situation is very different; at least two-thirds of all wound infections are caused by organisms of probably endogenous origin and these are predominantly Gram-negative bacilli. In the recent national prevalence survey (Meers et al., 1981), coagulase-negative staphylococci were isolated from only 8/l% (5 per cent) infected wounds and it is likely that some of these were from prosthetic replacement operations or were not the cause of the infection. About one-third of the wound infections were caused by Staph. uur~. These are usually isolated from clean wounds (e.g. herniorrhaphy, vascular or orthopaedic operations) but many are probably of endogenous origin. To explain the limited role of airborne spread in general surgery, Lidwell (1981) has suggested that it only assumes major clinical relevance when transfer by other possible routes, contact and endogenous, is considerably reduced. Surgical technique plays an important role in the prevention of infection and some orthopaedic surgeons have very low infection rates in conventionally ventilated theatres (see page 233). Nevertheless, antibiotic prophylaxis undoubtedly played some part in contributing to low infection rates. It might be argued that as antibiotic prophylaxis is effective, there is no need to introduce ‘ultraclean’ air systems even for orthopaedic prosthetic replacement surgery. But there is evidence that the effects of ultraclean air ventilation and of antibiotic prophylaxis are additive. Antibiotics involve no installation costs, but when used prophylactically for each prosthetic operation they involve a continuing and cumulative expenditure and a potential, if small, hazard of emergent bacterial resistance. It seems rational to restrict either/or both of these methods of preventing infection to situations where a high risk of infection is known to exist. Another approach to reducing airborne infection has been the introduction of bacteria-impermeable clothing [reviewed by Mackintosh (1982)]. Unfortunately, such clothing is uncomfortable for the operating team, but the use of ventile suits with body-exhaust ventilation makes them more acceptable. This system used in ultraclean air operating rooms contributes a further small but significant reduction in infection rates in joint prosthetic surgery. The advantages of bacteria-impermeable clothing in general surgery are more doubtful. Prevention of shedding of 0195-6701/82/030215
+ 02 $oz.oo/o
@ 1982 The Hospital Infection
215
Society
216
Editorial
normal skin bacteria into the air will not have much effect on the infection rates in most types of operation for the reasons already given. It would, therefore, seem unnecessary in general surgery to replace conventional theatre clothing with bacteriaimpermeable clothing unless there is no increase in cost and no loss in comfort to the surgeon. However, it is likely that the controversy over ‘ultraclean’ air and bacterial impermeable clothing will continue; a clinical trial to detect a small reduction in infection in operations with an initially low infection rate requires a large number of operations (as in the MRC trial); the expense in time and money to repeat the MRC trial for other types of clean surgery, even with higher initial infection rates, would be considerable and might seem extravagant, particularly as the end result may fail to ,demonstrate clinical significance. Moreover, demonstrating that ultraclean air in operating rooms can reduce the incidence of postoperative infection must inevitably place that measure in competition for limited NHS funds with other clinical necessities, some of them life-saving (e.g. kidney units). Here, as in some other situations, a scientific discovery creates problems which cannot be solved by scientists alone. Doctors and infection control experts can give an informed opinion, but the allocation of priorities between such alternatives requires wisdom and sensibility as well as knowledge. References ‘Lidwell., 0. M. (1981). Airborne bacteria and surgical infection. In: Nosocomiul Infections. (Dixon, R. E., Ed.), pp. 127-132. Yorke Medical Books: New York. Lidwell, 0. M., Lowbury, E. J. L,, Whyte, W., Blowers, R., Stanley, S. & Lowe, D. (1982). The effects of ultraclean air m operating rooms on deep sepsis after total hip or knee replacement: a randomised study. British Medical Journal 285, 10-14. Mackintosh, C. A. (1982). A testing time for gowns. Journal of Hospital Infection 3, 5-8. Meers, P. D., Ayliffe, G. A. J., Emmerson, A. M., Leigh, D. A., Mayon-White, R. T., Mackintosh, C. A. & Stronge, J. L. (1981). Report on the national survey of infection in hospitals, 1980. Journal of Hospital Infection, (Supplement). Whyte, W., Hodgson, R. & Tinkler, J. (1982). The importance of airborne bacterial contamination of wounds. Journal of Hospital Infection 3, 123-135.
Editorial Airborne
infection
in surgery
The relative roles of airborne and contact spread of staphylococci to operation wounds remain uncertain. Evidence on this subject, which is often controversial, is reviewed in a special article in this issue. A recent large MRC trial on hip and knee joint prosthetic surgery demonstrated that airborne spread was apparently responsible for a small but clinically significant number of septic wounds which could be reduced by operating in ‘ultraclean’ air (Lidwell et al., 1982). Whyte, Hodgson and Tinkler (1982) also showed that most of the infections in their study on similar operations were probably due to airborne spread, and the organisms causing infection were mainly normal skin flora (Staphylococcus epidermidis and diphtheroids). In other types of surgery, particularly abdominal, the situation is very different; at least two-thirds of all wound infections are caused by organisms of probably endogenous origin and these are predominantly Gram-negative bacilli. In the recent national prevalence survey (Meers et al., 1981), coagulase-negative staphylococci were isolated from only 8/l% (5 per cent) infected wounds and it is likely that some of these were from prosthetic replacement operations or were not the cause of the infection. About one-third of the wound infections were caused by Staph. uur~. These are usually isolated from clean wounds (e.g. herniorrhaphy, vascular or orthopaedic operations) but many are probably of endogenous origin. To explain the limited role of airborne spread in general surgery, Lidwell (1981) has suggested that it only assumes major clinical relevance when transfer by other possible routes, contact and endogenous, is considerably reduced. Surgical technique plays an important role in the prevention of infection and some orthopaedic surgeons have very low infection rates in conventionally ventilated theatres (see page 233). Nevertheless, antibiotic prophylaxis undoubtedly played some part in contributing to low infection rates. It might be argued that as antibiotic prophylaxis is effective, there is no need to introduce ‘ultraclean’ air systems even for orthopaedic prosthetic replacement surgery. But there is evidence that the effects of ultraclean air ventilation and of antibiotic prophylaxis are additive. Antibiotics involve no installation costs, but when used prophylactically for each prosthetic operation they involve a continuing and cumulative expenditure and a potential, if small, hazard of emergent bacterial resistance. It seems rational to restrict either/or both of these methods of preventing infection to situations where a high risk of infection is known to exist. Another approach to reducing airborne infection has been the introduction of bacteria-impermeable clothing [reviewed by Mackintosh (1982)]. Unfortunately, such clothing is uncomfortable for the operating team, but the use of ventile suits with body-exhaust ventilation makes them more acceptable. This system used in ultraclean air operating rooms contributes a further small but significant reduction in infection rates in joint prosthetic surgery. The advantages of bacteria-impermeable clothing in general surgery are more doubtful. Prevention of shedding of 0195-6701/82/030215
+ 02 $oz.oo/o
@ 1982 The Hospital Infection
215
Society
216
Editorial
normal skin bacteria into the air will not have much effect on the infection rates in most types of operation for the reasons already given. It would, therefore, seem unnecessary in general surgery to replace conventional theatre clothing with bacteriaimpermeable clothing unless there is no increase in cost and no loss in comfort to the surgeon. However, it is likely that the controversy over ‘ultraclean’ air and bacterial impermeable clothing will continue; a clinical trial to detect a small reduction in infection in operations with an initially low infection rate requires a large number of operations (as in the MRC trial); the expense in time and money to repeat the MRC trial for other types of clean surgery, even with higher initial infection rates, would be considerable and might seem extravagant, particularly as the end result may fail to ,demonstrate clinical significance. Moreover, demonstrating that ultraclean air in operating rooms can reduce the incidence of postoperative infection must inevitably place that measure in competition for limited NHS funds with other clinical necessities, some of them life-saving (e.g. kidney units). Here, as in some other situations, a scientific discovery creates problems which cannot be solved by scientists alone. Doctors and infection control experts can give an informed opinion, but the allocation of priorities between such alternatives requires wisdom and sensibility as well as knowledge. References ‘Lidwell., 0. M. (1981). Airborne bacteria and surgical infection. In: Nosocomiul Infections. (Dixon, R. E., Ed.), pp. 127-132. Yorke Medical Books: New York. Lidwell, 0. M., Lowbury, E. J. L,, Whyte, W., Blowers, R., Stanley, S. & Lowe, D. (1982). The effects of ultraclean air m operating rooms on deep sepsis after total hip or knee replacement: a randomised study. British Medical Journal 285, 10-14. Mackintosh, C. A. (1982). A testing time for gowns. Journal of Hospital Infection 3, 5-8. Meers, P. D., Ayliffe, G. A. J., Emmerson, A. M., Leigh, D. A., Mayon-White, R. T., Mackintosh, C. A. & Stronge, J. L. (1981). Report on the national survey of infection in hospitals, 1980. Journal of Hospital Infection, (Supplement). Whyte, W., Hodgson, R. & Tinkler, J. (1982). The importance of airborne bacterial contamination of wounds. Journal of Hospital Infection 3, 123-135.