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Books / Re: Operation Theatre
« Last post by Dr Varun Sharma on April 22, 2012, 07:30:01 pm »
Operating-Room Environment

Introduction | Preoperative Period | Operating-Room Environment | Postoperative Period | Overview | References   
Clean-Air Technology
The use of ultraviolet light to sterilize air particles carrying bacteria was initiated in 1936, but the absolute effectiveness of this technology in the clinical setting has not been definitively determined, as studies to date have been retrospective, with comparison of clinical experiences and historical controls41,50,64. The lack of conclusive clinical studies combined with concern regarding exposure of operating-room personnel to ultraviolet light has led to only tentative acceptance of this methodology. However, recent cost-effectiveness comparisons have created a resurgent interest in ultraviolet-light technology since it is considerably less expensive than laminar airflow systems8,64.
In 1969, Charnley and Eftekhar reported a dramatic reduction in the prevalence of postoperative infection after total hip arthroplasty, from 9 per cent (seventeen of 190) to 1 per cent (nine of 708), with the implementation of a clean-air operating theater16. Careful analysis of their data suggested that multiple factors over the course of the study, such as the method of subcutaneous wound closure and the use of antibiotics, may also have contributed to the reduced rate of infection. In a subsequent report that attempted to clarify these other variables, Charnley concluded that clean air was the most important factor but was not the sole reason for this reduction in the prevalence of infection15. It should be noted that he suggested that clean air is optimally provided by a combination of laminar airflow, with a room-air-exchange turnover rate of more than 300 times an hour; the use of a vertical airflow system; and the use of personnel isolator suits. He also stressed that horizontal laminar airflow systems should be used with body-exhaust systems and impermeable gowns15. Finally, he stated: "I most certainly do not wish to be reported as advocating clean air as a panacea for all surgeon's problems of sepsis in total hip replacement."15
Subsequently, substantial interest developed in the use of clean-air technology as a method of preventing infection in association with total joint arthroplasty. Many initial studies retrospectively evaluated the efficacy of laminar airflow systems by comparing historical rates of infection, and a thorough review by Nelson et al. detailed many of these studies85. A large multicenter prospective randomized clinical trial62 evaluating the effect of laminar airflow during 6781 hip arthroplasties and 1274 knee arthroplasties performed between 1974 and 1979 was published in 1982. Infection occurred in sixty-three (1.5 per cent) of 4129 patients in the control group and in only twenty-three (0.6 per cent) of 3923 patients in the ultraclean-air group (p < 0.001)62. Although these results seemed to provide irrefutable evidence as to the efficacy of laminar airflow systems, the study design had flaws that included randomization irregularities and lack of patient stratification, and, furthermore, the use of prophylactic antibiotics was not controlled59. This study did demonstrate clearly that body-exhaust suits reduced the bacterial counts in the room air and, in general, that vertical airflow systems performed better than horizontal airflow systems. The inconsistency in the use of prophylactic antibiotics in this study62 was a major problem because, in the presence of prophylactic antibiotics, the independent effect of laminar airflow was reduction of the prevalence of infection further from twenty-four (0.8 per cent) of 2968 in the control group to ten (0.3 per cent) of 2863 in the ultraclean-air group, which was not significant (p < 0.1) (Table II). However, in the absence of prophylactic antibiotics, the rate of infection was reduced from thirty-nine (3.4 per cent) of 1161 to thirteen (1.2 per cent) of 1060, which was significant (p < 0.01) (Table II). These data suggest that both factors have an independent effect on the reduction of infection but leave open the question of whether laminar airflow is necessary when prophylactic antibiotics are used.
A large retrospective study of 2384 total hip arthroplasties resulted in additional doubt about the absolute efficacy of laminar airflow technology when prophylactic antibiotics are used69. Between 1975 and 1978, when none of the patients received prophylactic antibiotics, infection developed after nine (3.1 per cent) of 289 arthroplasties performed in a conventional operating room, compared with nine (2.5 per cent) of 363 arthroplasties performed in a laminar airflow room (p = 0.5). After the use of prophylactic antibiotics was initiated in 1979, infection developed following six (0.9 per cent) of 669 arthroplasties performed in the conventional operating room, compared with three (0.3 per cent) of 1063 arthroplasties performed in a laminar airflow room. Again, these differences were not significant (p = 0.1). The difference in the rates of infection between the two study periods (2.8 per cent without antibiotic prophylaxis, compared with 0.5 per cent with antibiotic prophylaxis) was highly significant (p < 0.00001)69. Although retrospective, the study was limited to patients who had had the arthroplasty performed by the same surgeons in one hospital and who had received the same prosthesis, and it was based on excellent documentation of the use of prophylactic antibiotics and consistent use of vertical laminar airflow and body-exhaust suits69.
A large retrospective study by Salvati et al. of 3175 total hip and knee replacements, performed with or without a horizontal unidirectional filtered airflow system, demonstrated a detrimental effect of laminar airflow104. It is extremely important to note that personnel isolator suits were not used in this study. The paradoxical increase in the rate of infection after total knee arthroplasty performed in the laminar airflow rooms was attributed to positioning of the operating team between the patient and the airflow unit, with subsequent entrainment of air containing particulate matter and bacteria from the operating-room personnel into the operative wound104.
The preliminary results were recently reported for a randomized blinded prospective study of 7305 patients who had a total hip or knee arthroplasty with use of horizontal unidirectional airflow and no personnel isolator suits33. All of the patients received antibiotic prophylaxis. Although there was no significant difference in the rate of deep periprosthetic infection between the patients who had the procedure in a room with activated laminar airflow and those who had it in the presence of conventional airflow, it should be noted that these preliminary results essentially parallel the results of Salvati et al.104, in that there was a trend toward a higher rate of infection in some groups with laminar airflow but not in others.
These recent studies emphasize the need for appropriate application of clean-air technology and the paradoxical effects that can occur with the misunderstanding of clean-air concepts. Although there is still considerable controversy regarding the necessity of laminar airflow for the performance of total joint arthroplasty if prophylactic antibiotics are used, the following points can be reasonably drawn from the available literature.
1. Vertical laminar airflow units generally reduce airborne contamination better than horizontal airflow units. This is especially true when personnel isolator suits are not used.
2. Strict attention to laminar airflow protocol is essential, and there can be paradoxical increases in the rates of infection if these concepts are disregarded.
3. During the past few decades, the appropriate use of clean-air technology to reduce airborne contamination has reduced the prevalence of infection after total hip and knee arthroplasty.
4. The current literature has not established that clean-air technology can greatly reduce the prevalence of infection when prophylactic antibiotics are also used. However, if the rate of early postoperative infection following the procedures performed by an individual surgeon or at a specific institution exceeds four or five per 1000 total hip arthroplasties and six, seven, or eight per 1000 total knee arthroplasties, the use of some method of clean-air technology should be considered to reduce further the prevalence of infection15,16,33,49,61,62,108. It is important to remember that, with this low prevalence of infection of less than 1 per cent, analysis of more than 6000 patients is required to achieve the statistical power necessary to determine the effect of any one independent variable, such as airflow, on the rate of infection after total joint replacements.
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