G. Kunst et al., PATIENT-CONTROLLED EPIDURAL DIAMORPHINE FOR POSTOPERATIVE PAIN - VERBAL RATING AND VISUAL ANALOG ASSESSMENTS OF PAIN, European journal of anaesthesiology, 13(2), 1996, pp. 117-129
Twenty-two patients were studied while receiving epidural analgesia wi
th diamorphine after major lower abdominal surgery under combined regi
onal and general anaesthesia. Epidural PCA began when the intraoperati
ve epidural block with bupivacaine wore off enough for the patient to
request treatment. It was started with 2 mg of diamorphine and continu
ed with a reducible background infusion that was initially set at 0.2
mg h(-1) and supplemented by on-demand doses of 0.2 mg, with a lockout
time of 15 min. The patients received routine post-operative monitori
ng and care, with pain at rest being assessed on a four-point verbal r
ating scale (VRS, none, mild, moderate, severe) at 5, 10, 15, 30, 45,
60, 90 and 120 min from the start of ePCA, then hourly until 24 h and
then 2-hourly until 48 h. VRS on coughing and a 10 cm visual analogue
score (VAS) at rest and on coughing were recorded at the same times at
4 h, then 4 hourly until 24 h and then at 48 h, at which times, blood
samples were also taken to measure morphine concentrations by radioim
munoassay. Analgesia started promptly and reached a maximum at between
30 and 45 min, accompanied by maximum sedation. Thereafter clinically
acceptable analgesia was maintained without undue sedation for 48 h,
though pain on coughing was less well controlled than pain at rest. Af
ter the initial loading dose of diamorphine, the 95% confidence interv
als (CI) for further consumption were 3.7 to 17 mg (average 9.7) in th
e first 24 h and 2.1 to 12.9 mg (average 6.7 mg) in the second 24 h. T
he plasma morphine concentrations rose to a plateau by about 15 min, w
ith concentrations within 95% CI from 0 to 11 ng mL(-1) (average 5 ng
mL(-1)). The VRS and VAS pain scores were analysed by a conservative a
pproach that treated them as ordinal data, and by a parametric approac
h that treated them as interval data. Both approaches conveyed broadly
similar information about the post-operative analgesia.