Objective: To investigate the impact of high-efficiency particulate air (HEPA) - filtered air conditions, either turbulent or directed by (vertical) laminar airflow, on severe SSI rates in hip replacement surgery due to arthrosis.
Methods: We accomplished a retrospective cohort-study based on routine surveillance data from July 2004 to June 2009. Active SSI surveillance was performed according to the methods and definitions given by the US National Nosocomial Infection Surveillance system. Corresponding to our previous investigations five years ago, surgical departments were assigned to 2 groups according to the OR ventilation technique in place: (i) conventional turbulent ventilation with HEPA - filtered air; (ii) HEPA - filtered laminar airflow ventilation by (vertical) laminar airflow supply air diffusers. We accomplished a multivariate analysis – determined by generalized estimating equations (GEE) taking into account the departments as a cluster – to control for possible confounding factors: gender, age and American Society of Anaesthesiologists (ASA) score of the individual patients; duration of operation; turbulent or laminar airflow OR ventilation; area at least 2,40 m x 3,20 m and additionally deflectors. Only aseptic operations were considered in this study.
Results: 58 surgical departments participating voluntarily in the German national nosocomial infections surveillance system “KISS” were included (a total of 38 701 hip replacement operations with 270 severe SSI, severe SSI rate: 0.70). The risk for severe SSI did not differ whether (i) conventional turbulent ventilation or (ii) laminar airflow OR ventilation was used. Adjusted odds ratio: 1.44 <0.63-3.30>. Equally, the size of the ceiling did not change the risk for developing a severe SSI (Adjusted odds ratio: 0.94 <0.44–2.00>).
Conclusions: OR ventilation with laminar airflow showed no benefit for severe SSI after hip replacement surgery due to arthrosis. Thereby, we confirmed the data of our previous study covering the period from 2000-2004.