Patient-controlled analgesia in the postoperative period.

Patient-controlled delivery systems deliver drugs at a rate which is controlled by the patient in order to achieve plasma concentrations consistent with acceptable efficacy and minimal side-effects. They can be used therapeutically to provide pain relief after surgery and as a research tool to measure the efficacy of other analgesic techniques. Patient-controlled analgesia (PCA) was investigated in the postoperative period. Comparative studies of PCA devices revealed little difference in terms of clinician and patient satisfaction. As a research tool, PCA proved useful in evaluating alternative methods of providing postoperative analgesia. Ambulatory PCA devices were more portable (p=0.01) on the first postoperative day with less nausea (p=0.02) on the second. Mean (SEM) postoperative morphine requirements were 82.9 (9.8) mg and 120.6 (17.5) mg for the ambulatory and bedside PCAS respectively (p=0.06). Mean (SEM) postoperative morphine consumption between the electronic 35.1 (8.5) mg and nonelectronic devices 35.7 (6.6) mg were similar (p=0.77). In evaluating other methods of analgesia, there was no significant difference between active and placebo TCENS. Mean (SEM) postoperative opioid requirements were 35.6 (5.3) mg and 31.6 (3.5) mg for the active and placebo groups respectively (p=0.5). Subcutaneous wound infiltration with bupivacaine 0.5% also failed to decrease mean (SEM) opioid requirements for the first postoperative day, which were 56.7 (6.1) mg and 67.3 (6.4) mg for the bupivacaine and saline groups respectively (p=0.89). When diamorphine and morphine were compared for dose and effect, the postoperative mean (SEM) requirements were 20.2 (2.4) mg and 44 (6.8) mg respectively (p=0.004). No significant differences were found in side-effects. After PCA and i.m. morphine no differences were detected in mean (SEM) postoperative consumption - 34.8 (5.0) mg and 30.2 (6.7) mg in the PCA and i.m. groups respectively (p=0.17). Overall requirements for antiemetics were not significant (p=0.69). In the PCA group, 53% patients did not vomit, were not nauseated and did not require antiemetics compared with 27% patients in the i.m. group (p=0.14).