Feedback by patient‐controlled analgesia devices

logarithmic) should be applied before considering the significance of the difference in total consumption (and hence before any calculation of the appropriate sample size). Uncorrected t-tests could be applied to the total means to assess significance. The negative correlation (variance of total < total of variance) between the daily figures complicates interpretation, so consideration of benefit of treatment is best based on the differences in total consumption. How then can true patient-controlled epidural analgesia be compared with the sham type? One method would be to have two groups of PCEA: no background infusion versus a ‘smart’ background infusion of 14 m1.h-l. The latter group would be ‘in control’, but demands for analgesia occur so infrequently that the technique would approximate to continuous infusion. ‘Smart’ background infusion (currently being developed by Graseby Medical) automatically discontinues itself after a preset time if analgesia is not demanded. and recommences when a demand is made. Nolan and colleagues have made a worthy attempt to widen our knowledge, but more work and a larger study is needed to answer the question is patient controlled epidural analgesia no better than continuous infusion epidural analgesia?