Do warming blankets increase bacterial counts in the operating field in a laminar-flow theatre?

Patient warming systems are used routinely to prevent hypothermia under anaesthesia. Airflow from warming blankets may potentially influence bacterial counts either by pumping 'dirty air' from floor level to the operating area or by blowing the patients' skin cells into the operating field from airflow under the blanket. Using slit-air sampling we analysed the air quality within a laminar-flow theatre at a simulated operating site. We assessed the effect of 'high shedding of skin' under the blanket using volunteer patients with psoriasis. We also simulated general theatre activity outside the laminar-flow area in order to determine whether the bacterial counts in the operating field were affected. No colonies were grown in any of the groups tested and our results suggest that the patient warming system does not influence bacterial counts at the operating site in an ultraclean air-ventilated theatre, even with patients who have high shedding of skin cells.