The efficacy, applicability and side-effects of postoperative intravenous patient-controlled morphine analgesia: An audit of 1233 Chinese patients

Abstract

We analyzed data from 1233 Chinese patients of a wide age range who received patient-controlled analgesia (PCA) intravenous morphine for postoperative pain relief during the period from January 1992 to May 1995. The analgesic regimen was standardized as follows: PCA bolus 1 to 1.5 mg; lock-out interval 5 minutes; one-hour maximum dose 0.075 to 0.1 mg.kg-1 and background infusion 0 or 0.5 mg.h-1. Most patients underwent major surgery that was broadly subclassified according to the anatomical area involved. The median verbal numerical rating scales of pain (0 to 10) at rest and while coughing for the first, second and third 24 hours were 3.0/5.0, 1.5/4, 0 and 0/3, 0 respectively and the corresponding demand to delivery ratios were 2.8 ± 2.9, 2.6 ± 2.4 and 2.4 ± 2.6. The overall morphine consumptions in 1004 of these Chinese patients were 27.5 ± 16.8, 178 ± 16,1 and 18.1 ± 21.0 μg.kg-1.h-1 during the first 16, 17 to 41 and 42 to 66 postoperative hours respectively. These figures were the same as for Caucasian patients managed in the same institution. Morphine consumption was significantly higher following thoracic, upper abdominal and spinal surgery. Also it was higher in patients younger than 65 years, males, cigarette smokers and those with ASA physical status I or II. The commonest side-effects were nausea (34.5%) and vomiting (18.2%). Bradypnoea and oxygen desaturation occurred in 0.5% and 1.6% respectively. All cases were promptly detected and managed with no adverse outcomes. Most patients were satisfied (76.7% ranked 'good') with their postoperative analgesia. The commonest reasons for dissatisfaction were inadequate pain relief, nausea and reluctance to selfcontrol analgesic administration. It is concluded that PCA with intravenous morphine is effective and safe as a routine postoperative technique for Chinese surgical patients.