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Laminar airflow ventilation during orthopedic, abdominal procedures does not prevent surgical site infections, study suggests

Friday, November 07 2008 | Comments

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What's This? A large, retrospective study suggests that operating rooms (ORs) with laminar airflow ventilation do not prevent surgical site infections (SSIs) among patients undergoing abdominal or orthopedic surgery, and ORs with this type of ventilation may actually be associated with a significantly higher risk of severe SSIs following hip replacements as compared with ORs that use turbulent ventilation.

The study included data from 63 surgery departments in 55 German hospitals participating in the German national nosocomial infections surveillance system (KISS). In all, 99,230 operations with 1,901 SSIs were represented.

The ORs were grouped according to whether they used turbulent ventilation with high-efficiency particulate-filtered air (HEPA) or HEPA-filtered (vertical) laminar airflow ventilation. Each surgical department performed at least 100 operations per year between 2000 and 2004 in the respective types of surgeries studied, which included hip and knee replacements, appendectomy, cholecystectomy, colon surgery, and herniorrhaphy.

Univariate analysis demonstrated higher SSI rates in ORs with laminar airflow ventilation as compared with turbulent ventilation for all types of surgery included in the study except for colon surgery, a finding that was confirmed by multivariate analysis, which took into account both patient- and hospital-based confounders.

The adjusted odds ratios for an SSI in ORs ventilated by laminar air flow versus turbulent air flow were 1.44 (95% CI, 0.93-2.23) for hip replacement procedures, 2.38 (95% CI, 0.89-6.33) for knee replacements, 2.09 (95% CI, 1.08-4.02) for appendectomies, 1.53 (95% CI, 0.95-2.45) for cholecystectomies, 1.17 (95% CI, 0.65-2.11) for colon surgeries, and 1.67 (95% CI, 0.95-2.91) for herniorrhaphies. In addition, there was a significant 63% increase in the incidence of severe infections for hip replacement surgeries performed in operating rooms with laminar airflow ventilation as compared with those performed in ORs with turbulent ventilation (OR, 1.63; 95% CI, 1.06-2.52; P<.001).

The researchers said it was "surprising" that the study did not find that laminar airflow systems protect against SSIs, and especially that patients undergoing hip replacements performed in laminar airflow ORs are more likely to experience a severe SSI.

They recommended further studies to evaluate these findings, including randomized trials that consider differences in medical treatment, such as antibiotic prophylaxis, intraoperative wound temperature (both systemic and in the wound), glycemia management, and surgical technique (such as use of cautery).  (Brandt C. et al. Ann Surg 2008;248:695-700.)

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