Gender and pain upon movement are associated with the requirements for postoperative patient-controlled iv analgesia: a prospective survey of 2,298 Chinese patients

Purpose: To investigate prospectively the influence of patient characteristics upon, and the association of postoperative measurements with, the requirements for postoperative morphine and the assessment of resting pain and pain upon movement in Chinese patients. Methods: From January 1998 to December 1999, patients receiving patient-controlled iv morphine subsequent to general anesthesia and surgery at our institute (Kaohsiung Veterans General Hospital), were enrolled in the study. Demographic data (such as gender, age, weight, height and education level) and postoperative measurements, including pain scores at rest or during movement, sedation scores and morphine consumption, were recorded. Results: In total 2,298 patients were recruited. Females consumed significantly less morphine via patient-controlled analgesia (PCA) in the first three postoperative days than was the case for males (P < 0.05). Gender was the strongest predictor for postoperative morphine requirements. Postoperative pain upon movement was another effective predictor for morphine requirement (P < 0.05). Age, body height, body weight, education and operation sites were not associated with morphine consumption. Conclusion: Gender and postoperative pain upon movement are the major factors influencing morphine requirement for patient postoperative days in Chinese patients.