British journal of anaesthesia
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Randomized Controlled Trial Clinical Trial
Myocardial depressant effect of nitrous oxide after coronary artery bypass graft surgery.
We have studied the cardiovascular effects of nitrous oxide after cardiac ischaemia-reperfusion injury caused by aortic cross-clamping and unclamping during coronary artery bypass grafting (CABG). At the time of chest closure, 20 patients were allocated randomly to receive oxygen and air (FIO2 = 0.5) or 50% nitrous oxide in oxygen in addition to anaesthesia with fentanyl. Nitrous oxide significantly decreased mean arterial pressure (P less than 0.01) and cardiac index (P less than 0.05), which suggests that nitrous oxide with fentanyl may significantly depress left ventricular performance after CABG. Although ischaemia-reperfusion cardiac injury did not appear to increase the myocardial depressant effect of nitrous oxide, the use of nitrous oxide is not recommended immediately after CABG.
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Comparative Study
Response of 10 pulse oximeters to an in vitro test system.
Pulse oximeters are often used in situations in which severe hypoxaemia may occur. We have developed an in vitro system to test the accuracy of pulse oximeter calibration. ⋯ The oximeters tested varied widely in their accuracy and linearity. We conclude that the system can test the accuracy, reproducibility and linearity of response of pulse oximeter readings at low oxyhaemoglobin saturations.
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Fentanyl and bupivacaine were tested for their stability when diluted with 0.9% sodium chloride to 4 micrograms ml-1 and 0.1% respectively, in 100-ml polyvinyl chloride (PVC) bags, alone and in combination, with and without adrenaline 1:200,000. Changes in drug concentration and pH were investigated for 56 days. The combination of fentanyl, bupivacaine and adrenaline was tested under varying environmental conditions of 35 degrees C, 4 degrees C, -18 degrees C, room temperature, darkness and after autoclaving. ⋯ Adrenaline was progressively degraded to a maximum reduction of 37.3% at 35 degrees C by day 56. Solutions containing adrenaline became more acidic over 56 days. Fentanyl and bupivacaine were stable.
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A disposable patient-controlled analgesia (PCA) device was evaluated in 20 children after major abdominal, urological and orthopaedic surgery. All patients were given a high dependency level of nursing care in general wards. ⋯ Morphine consumption was similar with the two techniques, but varied widely between patients. The disposable device has a complementary role to play in the provision of a comprehensive pain relief service for children.