Patient Re-education vs. Background Morphine to IV-PCA in Patient With Unsatisfactory Analgesia Post Laparotomy

Inclusion Criteria: * American Society of Anesthesiologists (ASA)Physical Status Classification Class I and II * Elective laparotomy * able to understand either malaysia, mandarin, english language or local dialect * patient with dynamic pain score 4/10 and more within the first 4-hour after initiation of IV-PCA Exclusion Criteria: * patient refusal * laparotomy with pfannenstiel incision * patients with a history of allergy to opioids * patients who required post-operative ventilation support * patients ASA III and above * patients unable to use PCA due to insufficient comprehension * morbid obesity/ obstructive sleep apnea * chronic opioid or alcohol abuse