The efficacy of morphine analgesia for procedural pain in preterm infants : subjective judgements as a measure

The purposes of this study were twofold. The first was to determine the efficacy of morphine analgesia in reducing procedural pain in preterm neonates. Efficacy in this context was considered a question of whether objectively measurable reductions in facial response to painful stimuli possess clinical and social validity. Subjective judgements made by untrained adults were employed to address the question of efficacy in three ways; 1) to determine whether the changes in facial expression achieved with morphine analgesia represented perceptible changes in pain levels, 2) to determine whether the morphine analgesia resulted in a judged reduction in.the need for pain control intervention and 3) to determine whether judges believed morphine to provide an adequate level of pain reduction. The second purpose was to examine the effect of judges' empathic concern on their judgements of pain in this population. It was also expected that infant post-cOnceptional age would affect pain judgements due to a previously demonstrated attenuation of pain responses in post-conceptionally very young newborn infants. The judges were 20 university students,'a sample size providing^ high level of inter-judge reliability. The patients were 50 preterm infants who had been administered morphine analgesia and were subjected to heel stick for blood testing as a part of their hospital treatment in a Neonatal Intensive Care Nursery. The judgement stimuli consisted of three ten-second video clips of each infant. Each of the three clips showed the infant either at rest (no pain), undergoing heel, stick with no morphine analgesic (untreated pain) or undergoing a heel stick with morphine (treated pain). The procedure was not visible in the video clips. Judges were divided into high and low empathic concern groups based on their scores on an empathic concern scale. They were asked to perform two judgement tasks. In the first, they were blind to the condition portrayed in each clip and clips were presented in random order. Judges rated the sensory intensity and unpleasantness of each clip and whether the infant portrayed required pain control intervention (yes or ho). In the second, judges were presented with untreated and treated pain clips consecutively for each infant, and they were asked to rate the pain level of the infant in each clip on a visual analogue scale. They were also asked indicate whether the pain reduction achieved was adequate (yes or no). The results confirmed that the effects of morphine analgesia on preterm infants undergoing painful procedures have social and clinical validity. Judges average ratings of sensory intensity and unpleasantness were significantly reduced when the infants were receiving morphine analgesia. The need for intervention was also significantly reduced with the administration of morphine analgesia. The results were more equivocal with respect to the adequacy of these changes. The general pattern Of results suggested that morphine analgesia reduced the suffering experienced during heel stick to a level comparable to "at rest" ratings. However, judges believed even the infants at rest to be experiencing some pain. In the majority of cases (64%), infants were rated as receiving adequate pain reduction, but this percentage indicates that adequate reduction was not universally achieved, possibly due to a need for dosage adjustments. Contrary to