Background: Acute pain service (APS) has been set up at Siriraj Hospital with the aim of providing postoperative pain
management for patients receiving anesthetic pain control and other complicated cases undergoing major operations.
Objective: To identify the incidence of moderate to severe postoperative pain and its risk factors. To describe the techniques used and adverse effects in patients under APS care.
Material and Method: A prospective study in 340 surgical patients under APS care from January to September 2008 was
performed. Data were obtained from medical records and patients’ answers during 48 hours postoperatively.
Results: The incidences of postoperative pain scores 4-10 at 24 and 48 hours were 28.8% and 7.4%, with median pain intensity (0-10, [interquartile range]) of 2.5 [1.0-4.0] and 1.0 [0.0-2.0], respectively. The risk factors related to pain score 4-10 included analgesic intake for >2 consecutive weeks prior to operation, type of surgery with severe degree of pain and age <65 years (odds ratios [95% CI] of 7.12 [1.92, 26.44], 6.17 [1.37, 27.77], and 1.87 [1.07, 3.29], respectively). Of the patients, 67.9% received epidural block for postoperative analgesia. The incidences of nausea/vomiting and itching that needed treatment were 12.4% and 9.4%, respectively.
Conclusion: Risk factors that should be concerned were age <65 years, pre-operative prolonged analgesic use and surgeries
with expected severe degree of pain.

Keywords: Postoperative pain, Risk factors, Acute pain service