Bupivacaine has a chiral centre and is currently available as a racemic mixture of its two enantiomers: R(+)-bupivacaine and S(-)-bupivacaine. Preclinical studies have demonstrated that there is enantiomer selectivity of action with the bulk of central nervous system and cardiovascular toxicity residing with the R(+) isomer. The aim of this study was to compare the clinical efficacy and safety of S(-)-bupivacaine with racemic RS-bupivacaine for extradural anaesthesia. We studied 88 patients undergoing elective lower limb surgery under lumbar extradural anaesthesia who received 15 ml of 0.5% or 0.75% S(-)-bupivacaine, or 0.5% RS-bupivacaine in a randomized, double-blind study. There was no difference in onset time, maximum spread of sensory block or intensity of motor block between the three groups. Duration of sensory block was significantly longer for 0.75% S(-)-bupivacaine. We conclude that S(-)-bupivacaine has similar local anaesthetic characteristics to RS-bupivacaine when used for extradural anaesthesia.

The performance of a patient-demand, target-controlled alfentanil infusion system was compared with that of a traditional morphine patient-controlled analgesia (PCA) pump in 120 adult patients after cardiac surgery. Patients were randomized to one of the two PCA systems for their postoperative analgesia in the intensive care unit and pain, nausea and sedation scores were recorded every 4 h for the first 24 h. Episodes of hypoxaemia, myocardial ischaemia and haemodynamic instability were also recorded. In patients using the alfentanil system the overall median visual analogue pain score was 2.3 (95% Cl 2.3-2.8) compared with 3.0 (95% Cl 2.7-3.2) in those using morphine PCA (P < 0.05), but both systems delivered high-quality analgesia. The two groups did not differ with respect to the overall sedation scores, the frequency of postoperative nausea and vomiting, haemodynamic instability, myocardial ischaemia or hypoxaemia.

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Within the medical domain there are clear expectations as to how a patient should respond to treatments administered. When these responses are not observed it can be challenging for clinicians to understand the anomalous responses. The work reported here describes a tool which can detect anomalous patient responses to treatment and further suggest hypotheses to explain the anomaly. In order to develop this tool, we have undertaken a study to determine how Intensive Care Unit (ICU) clinicians identify anomalous patient responses; we then asked further clinicians to provide potential explanations for such anomalies. The high level reasoning deployed by the clinicians has been captured and generalised to form the procedural component of the ontology-driven tool. An evaluation has shown that the tool successfully reproduced the clinician's hypotheses in the majority of cases. Finally, the paper concludes by describing planned extensions to this work.