Objectives: Our goal was to identify the incidence and possible causes of delayed emergence after general anesthesia.

Materials and methods: A prospective, observational study was conducted in 1,500 patients underwent general anesthesia in Songklanagarind Hospital between November 1, 2007 and February 28, 2008. Delayed emergence was defined as not awakening for more than 15 minutes after finishing general anesthesia. Ninety-nine patients who had delayed emergence after general anesthesia were compared with 1,401 patients without delayed emergence for analysis into possible causes of delayed emergence. The causes of delayed emergence were identified in each patient.

Results: The incidence of patients who had delayed emergence following general anesthesia was 6.6%. The delayed emergence patients had significantly longer operative time, anesthetic time, awakening time, extubation time, length of recovery room stay and greater use of muscle relaxants than the non-delayed emergence patients. The possible causes of delayed emergence were residual inhaled agents (69.7%), residual opioids (18.2%), hypothermia (7.1%), and hypoventilation (4.0%).

Discussion: The incidence of delayed emergence was 6.6% and the possible causes were related to residual anesthetic agents, hypothermia and hypoventilation. Residual inhaled agents, residual opioids, hypothermia and hypoventilation were considered as preventable factors.