Effects of propofol target-controlled infusion on haemodynamic and respiratory changes with regard to safety.

We investigated the haemodynamic and respiratory effects of propofol target-controlled infusion (TCI) during spontaneous ventilation. We studied 20 patients scheduled for elective orthopaedic surgery who were classified as American Society of Anesthesiologists physical status I. During spontaneous ventilation, haemodynamic, respiratory and electroencephalographic variables were measured. Oxygen flow was maintained at 5 l/min using a semi-closed system and a close-fitting face mask. All measurements were obtained before the propofol TCI and at each propofol effect-site concentration (0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5 and 4.0 micrograms/ml). Changes in Bispectral Index Score, systolic blood pressure, diastolic blood pressure, end tidal carbon dioxide tension and heart rate were negatively correlated with propofol effect-site concentrations. Despite maintaining oxygen saturation (> or = 99%), apnoea and blood pressure reductions were abruptly induced as the propofol effect-site concentration increased. We therefore recommend careful monitoring of haemodynamic and respiratory function during spontaneous ventilation using propofol TCI.