The effectiveness of patient-controlled intravenous morphine with and without a supplementary fixed rate infusion was studied in 40 children after orthopaedic surgery and 40 children after abdominal surgery. The use of a background infusion after orthopaedic surgery, where the majority of children received intra-operative regional blockade, resulted in a higher total dose of morphine (P < 0.05) without evidence of improved analgesia, compared to PCA alone. Children receiving a background infusion after abdominal surgery showed evidence of improved sleeping patterns post-operatively compared with those receiving PCA alone, despite similar overall morphine consumption. There were no episodes of excessive sedation, or respiratory depression with the use of either regimen, and over 90% of the children studied were assessed as experiencing either no pain or mild pain. The suitability and efficacy of patient controlled analgesia for management of post-operative pain for children aged between 5 and 17 years appears to be confirmed. The use of a supplementary background infusion may be of value in children.

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Age‐related differences in the playfighting strategy of captive male red‐necked wallabies Macropus rufogriseus banksianus was examined. Our purpose was to determine whether wallabies adjusted their play in response to their partner's age and, if so, how. The way in which a wallaby played was dependent on the relative age of its partner, and this pattern tended to be the same regardless of whether it was the initiator or reactor of the interaction. If a wallaby's partner was younger than itself it adopted a defensive strategy in which it self‐handicapped by standing flat‐footed, Pawing rather than Sparring, and by not using its full strength. Its greater rate of Shaking suggests that this act may function as an appeasement signal in play. Furthermore, it was highly tolerant of the tactics used by its younger partner and took the more active role in prolonging interactions. If, on the other hand, its partner was older than itself, it adopted an offensive strategy involving vigorous Sparring, increased time in the High‐stance posture and a greater percentage of bouts that were of high intensity. Indeed, it played with even more vigour than when it playfought with wallabies of the same age as itself. Differences in the play of same‐aged partners were in the non‐fighting components of play, while those of differently‐aged partners were in the fighting components. Play between same‐aged partners, however, tended to be more stable and more competitive than that between partners of differing age. These results are discussed with emphasis on the compromises made in order for play to occur and the potential benefits to each partner of play in mixed‐age class encounters. We briefly consider the implications of self‐handicapping in the categorization of macropodid fights as play or aggression.

SummaryOxygen saturation was continuously measured using computerised pulse oximetry for 8 h overnight pre-operatively and for the ,first 24 h postoperatively in 40 patients receiving intermittent intramuscular morphine or continuous infusion of morphine following elective upper abdominal surgery. The proportion of time with an oxygen saturation less than 94% was used as an index of desaturation. Patients receiving continuous infusion analgesia received a larger morphine dose and achieved better analgesia than the intramuscular group. Postoperatively, the duration of desaturation increased I0,fold over pre-operative values, 'intramuscular' patients spending 39.0% ( S D , 37.0%) and 'continuous infusion' patients 40.0% (SO, 37.5%) of the time below 94% saturation. Although newer therapies (e.g. epidural analgesia and patient-controlled analgesia) are currently receiving greater attention. the seyuelae of these more traditional analgesic techniques warrant further study. Key wordsMonitoring; oximetry. Complications; hypoxia. Analgesics; morphine. Pain; postoperative.During the past 30 years the occurrence of intermittent and sustained postoperative hypoxia has been reported [ 1-31. The introduction of newer methods of opioid delivery e.g. patient-controlled analgesia (PCA) [4] and spinal opioids [5] has promoted considerable research into adverse effects of these techniques, particularly respiratory depression. In contrast, there has been little work looking at what actually happens following traditional methods of opioid delivery such as intramuscular injection (IM) and continuous intravenous infusion (CI). Catling et al., using the indices of respiratory rate, tidal volume, number of apnoeic episodes and partial pressure of carbon dioxide showed there were differences between IM and CI analgesia following cholecystectomy [2]. However, these measurements were intermittent, and pulse oximetry was not used. Continuous pulse oximetry, which has allowed accurate monitoring of pre-operative hypoxaemia, combined with computerised data collection, has enabled comprehensive analysis of patients' peri-operative oxygen saturation (Spo,). Brose et al. [6] comparing IM pethidine, PCA pethidine and extradural morphine for post-Caesarean section analgesia, reported that patients receiving PCA had long periods of mild desaturation (90-95%); in contrast, more severe desaturation (mean values 83%) occurred for shorter periods of time with extradural morphine and intramuscular pethidine. Continuous pulse oximetry was used by Wheatley et al. who studied patients undergoing lower abdominal procedures in order to assess the respiratory effects of extradural, PCA and IM analgesia [7]. These workers defined the pattern of Spo, readings as stable or unstable depending on the hourly variability of oxyhaemoglobin saturations, and hypoxaemia as a n Spo, < 94% for more than 10% of the time. Patients receiving IM and PCA had unstable patterns of Spo, values with no hypoxaemia, while 50% of patients receiving extradural morphine had unstab...