Arterial and venous blood lidocaine concentrations after local anaesthesia of the respiratory tract using an ultrasonic nebulizer.

Arterial and venous blood lidocaine concentrations were intermittently measured in 15 bronchoscopy patients in whom local anaesthesia was induced by an inhalation technique. A DeVillbiss ultrasonic nebulizer model 3574 was used. The anaesthetic was 10 ml of 4% lidocaine without adrenaline. Blood concentrations were measured 5 min after commencement of inhalation, on completion of inhalation, and then after 10, 30 and 60 min. Statistically significantly higher concentrations were found in the arterial blood at the first two sampling times (P less than 0.01 and P less than 0.05, respectively). The highest average concentration in both arterial and venous blood eas reached 10 min after completion of anaesthesia. After 30 min, there was no difference between the arterial and venous samples; and after 60 min, the concentration was higher in venous blood. The highest individual concentration was 2.8 mug/ml in arterial blood and 2.1 mug/ml in venous blood, well below that reported to cause systemic toxic symptoms. Thus, the inhalation technique may be considered a safe means of inducing anaesthesia in the respiratory tract.