[Smoking and preoperative fasting--are there evidence-based guidelines?].

Over the last years several clinical studies have modified the guidelines for preoperative fasting to reduce the risk of pulmonary aspiration. In most western countries the following guidelines are accepted: for clear liquids 2 hours, breast feeding 4 hours, small meals and breast milk substitutes 6 hours, heavy meals 8 hours. Since preoperative smoking is acknowledged as a risk factor, it should be ceased in most clinics 6 hours before induction of anaesthesia, as well. Smoking, however, does not increase the risk of pulmonary aspiration, as is often maintained, but increases the risk of postoperative pulmonary complications. To reduce the risk of perioperative pulmonary complications, cessation of smoking is necessary 8 weeks before operation. Stopping smoking only a few days before operation and anaesthesia even tends to increase the risk of pulmonary complications. Regarding cardiac complications, cessation of smoking 12 hours before anaesthesia is sufficient to reduce the incidence of cardiac ischaemia.