• N H Badner, J A Doyle, M H Smith, and I A Herrick.
• Department of Anaesthesia, London Health Sciences Center, University of Western Ontario, Canada.
• J Clin Anesth. 1996 Aug 1;8(5):382-5.

Study ObjectiveTo investigate the effect on the use of intravenous patient-controlled analgesia (PCA) of varying the dose (D) and lockout interval (LI) while keeping the hourly maximum dose constant.DesignRandomized, prospective study.SettingTeaching hospital.Patients75 patients scheduled to receive PCA morphine following abdominal surgery.InterventionsPostoperatively, patients were randomly assigned to receive PCA morphine with the following parameters: D = 1 mg, LI = 6 min (Group 1-6), D = 1.5 mg, LI = 9 min (Group 1.5-9), or D = 2 mg, LI = 12 min (Group 2-12), so that each group could receive a maximum hourly dose or 10 mg. Inadequate analgesia was managed by increasing the dose and lockout interval, while excessive sedation or respiratory rate less than 10 breaths/min resulted in decreasing the dose and lockout interval.Measurements And Main ResultsPatients were assessed for pain [visual analog scale (VAS), verbal rating scale (VRS)] and side effects at 1, 2, 4, and 24 hours. The number of doses administered, missed attempts, and morphine used for the first 24 hours was recorded by automatic printout from the PCA machine. There was no difference in the total 24-hour morphine consumption, analgesia, or incidence of side effects among the three groups at any of the measurement times. Two patients, one each in the 1.5-9 and 2-12 groups, required naloxone for respiratory depression. The number of PCA injections, attempts, missed attempts, and the incidence of dosage adjustment were all significantly higher for the 1-6 group (p < 0.05).ConclusionThe use of 1.0 mg with a 6-minute lockout may represent appropriate dose titration because this group obtained equivalent analgesia, morphine use, and side effects as the two larger dose and lockout groups. However, the increased number of PCA attempts and missed attempts may reflect lower satisfaction with PCA therapy.

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