Variables of patient-controlled analgesia. 2. Concurrent infusion.

The effectiveness of morphine after surgery by patient-controlled analgesia alone or with a concurrent infusion was studied. The infusion did not reduce the dose of self-administered analgesic and patients treated in this way received twice as much drug as those who used patient-controlled analgesia alone. Pain control was similar in both groups. The practice of patient-controlled analgesia plus infusion requires critical review.