Propofol or halothane anaesthesia for children with asthma: effects on respiratory mechanics.

Propofol may cause histamine release and alter airway tone and reactivity. Although its use has been reported to be safe in asthmatics, there is a lack of information on its effect on lung function in children with asthma. We measured respiratory mechanics after i.v. or inhalation anaesthesia in 60 children, aged 2-12 yr, with or without asthma. Anaesthesia was induced with propofol 3 mg kg-1, fentanyl 1 microgram kg-1 and atracurium 0.5 mg kg-1 and maintained with an infusion of propofol 10 mg kg-1h-1 and 50% nitrous oxide in oxygen. Halothane was administered subsequently at a concentration of 1 MAC. Respiratory mechanics were measured by applying a single-compartment model using multi-linear regression analysis to calculate dynamic compliance (Crs,dyn) and respiratory system resistance (Rrs), based on: Pao = V/Crs,dyn + V Rrs + PA,EE, where Pao = airway opening pressure, PA,EE = alveolar pressure, V = volume and V = flow. The two groups were comparable in age, weight and ventilation variables (tidal volume and peak pressure). Respiratory mechanics during propofol anaesthesia were comparable in normal and asthmatic children (Rrs = 20.5 X 10(-4) (SD 5.2 X 10(-4)) vs 21.5 X 10(-4) (5.7 X 10(-4)) kPa ml-1 S-1 (ns) and Crs,dyn = 247.5 (76.51 vs 235.1 (63.8) ml kPa-1 (ns)). Halothane produced a minimal decrease in Rrs and a minimal increase in tidal volume in both groups without changes in Crs,dyn. In conclusion, respiratory mechanics were comparable after propofol anaesthesia in both children with and without asthma. Changes in Rrs after halothane administration were not clinically relevant.