[Modification of cardiac circulation and respiratory parameters by alfentanil].

In 93 patients (ASA I) undergoing orthopaedic operations respiratory and haemodynamic effects of alfentanil (steady state: spontaneous breathing halothane, N2O/O2) were measured. After injection of alfentanil apnoea was found be readily antagonized by Naloxone. A significant decrease of arterial pressure and heart rate occurred simultaneously independent of dose level. The decrease of arterial pressure could be prevented by pre-injection of atropine. Therefore an increased vagal tone must be responsible for depression of haemodynamic parameters.