The safety and utilization of patient-controlled analgesia

Between December 1989 and March 1996, more than 6000 patients were treated with patient-controlled analgesia (PCA) at Auckland Hospital. The overall incidence of potentially life-threatening complications was low (0.28%). A small number (276) received PCA with a background opioid infusion. This technique was associated with a higher incidence of such complications (1.08%, P < 0.05). To further characterize the safety and utilization of PCA, a subgroup of 300 patients was analyzed. The average duration of PCA was 76.4 +/- 39.2 hr. The peak morphine consumption was highest on the day of operation (45.4 +/- 37.0 mg) and rapidly declined over the next 3 postoperative days (40.6 +/- 39.0, 33.3 +/- 26.2, and 27.8 +/- 36.6 mg, respectively). The ratio of drug demands to deliveries decreased from 1.76 on the morning of the first postoperative day to 1.17 on the evening of the third. The percentage of patients with inadequate analgesia (pain score > or = 3/10) and an inability to comply with physiotherapy (Bruggemann comfort score < or = 2/10) was high on the first postoperative day (42% and 18%, respectively). Men used significantly more morphine than women (141.7 +/- 123.6 versus 102.7 +/- 111.2 mg, P < 0.0001) and general surgical patients used more morphine than urology and orthopedic patients (152.6 +/- 136.9 versus 96.0 +/- 84.2 and 83.7 +/- 97.9 mg, P < 0.0001). There was no association between morphine consumption and age (r = -0.216). Of the 6% of patients who experienced hypoxemia and 2% who experienced respiratory depression, virtually all had one of three risk factors: bolus dose greater than 1 mg morphine, age greater than 65 years, or intra-abdominal surgery. The most common side effects were nausea and sedation. The incidence of nausea was highest on day 1 (28%) and decreased over the next 2 days (14.3% and 4.7%, respectively). A similar pattern was observed with sedation (incidence over the first 3 days: 28%, 9.3%, and 3.3%, respectively). Overall patient satisfaction scores were high (8.3/10 +/- 1.9). We conclude that the risk of serious complications with PCA is very low, but worrying degrees of hypoxemia and bradypnea do occur. We suggest prescribing regimens that may reduce complications and identify patients at high risk.