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Simulator radiographs taken as a record of breast radiotherapy planning often show ill defined breast tissue margins because exposure parameters are set to optimize visualization of the chest wall rather than the bulk of the breast. This creates difficulties when using simulator images as reference images in verification by comparing with either portal film or images from an electronic portal imaging device. Our aim was to improve breast images taken at simulation without changing exposure parameters that have been optimized for visualization of the chest wall. This has been achieved via an external filter to be used when taking radiographs with the treatment simulator. The filter is made of stainless steel coated with tin and is shaped to maintain acceptable imaging of the chest wall by covering only the section of field anterior to the chest wall. Radiographs of breast simulations using the filter have been accepted as satisfactory by both clinicians and radiographers. The filter is now in routine clinical use for breast and chest wall treatment simulation.

Summary The use of the new competitive muscle relaxant, atracurium, is described in five myasthenic patients presenting for thymectomy. With an initial dose of 0.1 mg/kg, that is approximately one-fifth of that normally used, and incremental doses of 0.02–0.04 mg/kg, satisfactory clinical conditions were achieved. Neuromuscular function was monitored throughout using the train-of-four mechanical twitch response, and residual neuromuscular blockade was reversed satisfactorily at the end of the procedure with neo-stigmine 5.0 mg. A marked increase in the magnitude of the first twitch of the train-of-four to greater than control levels, accompanied by pronounced fade. was found on reversal. In reduced dosage and with careful neuromuscular monitoring, atracurium is safe to use in the myasthenic patient.

The clinical neuromuscular effects of two doses of vecuronium (0.15 mg kg-1 and 0.2 mg kg-1) were investigated in 20 healthy patients and 20 patients with cirrhosis, and compared with previous work in which vecuronium 0.1 mg kg-1 was given under identical conditions of anaesthesia and monitoring. Ten healthy patients received vecuronium 0.15 mg kg-1 and 10 received 0.2 mg kg-1. Similarly, 10 patients with cirrhosis received vecuronium 0.15 mg kg-1 and 10 received 0.2 mg kg-1. Vecuronium 0.1 mg kg-1 has previously been shown to have a somewhat shorter duration of action in cirrhotic as opposed to healthy patients. In this study, vecuronium 0.15 mg kg-1 was found to have a similar duration of action in both groups, and vecuronium 0.2 mg kg-1 had a significantly longer action in the cirrhotic group. It is suggested that vecuronium should be used with caution in patients with hepatic dysfunction and that, in such patients, monitoring of neuromuscular function is desirable.

Vecuronium (initial dose 0.1 mg kg-1; incremental doses 0.04 mg kg-1) was given to 21 normal and 21 anephric patients. There were no gross differences between the two groups in the effect or in the duration of action of either initial or incremental doses, except in two anephric patients who were resistant to the agent. Reversal with neostigmine was satisfactory. In normal patients the initial dose of vecuronium was slower in onset of action than was atracurium 0.5 mg kg-1 (26 patients): the first two incremental doses of vecuronium were administered significantly earlier than the corresponding increments of atracurium (0.2 mg kg-1), but the duration of action of increments over-all was not greatly different. However, in anephric patients, except in the resistant patients, the behaviour of vecuronium was similar to that of atracurium (26 patients). A comparison with an initial dose of tubocurarine 0.5 mg kg-1 given to 20 anephric patients and tubocurarine 0.6 mg kg-1 given to 21 normal and 20 anephric patients showed tubocurarine to be longer acting and considerably less predictable. This was particularly so in the anephric group, in which its action sometimes persisted after neostigmine had been given.

The potentiation of alcuronium by halothane, enflurane and isoflurane was investigated using electromyography. In the first study, cumulative dose-response curves were constructed in four groups of 10 patients anaesthetized with one of the inhalation agents and nitrous oxide, or with fentanyl and droperidol (control). All three agents reduced the ED50 of alcuronium; the effect was marked with isoflurane (P less than 0.005) but less so with halothane (P less than 0.05) and enflurane (ns). In the second part of the investigation, designed primarily to test the duration of action of alcuronium with each agent, a single bolus dose of alcuronium 0.2 mg kg-1 was given to four similar groups (n = 5). The duration of action was significantly prolonged by enflurane (P less than 0.01) and isoflurane (P less than 0.05), but not by halothane. The possible reasons for this are discussed.

Summary The use of vecuronium in six patients with myasthenia gravis undergoing thymectomy is described; the train-of-four twitch technique was used to monitor neuromuscular function. The first two patients received an initial dose of 0.02 mg/kg and incremental doses of 4 μg/kg, which is in the order of one fifth of that normally used. Satisfactory depression of the first twitch of the train-of-four, however, was not obtained and, therefore, in the remaining four patients the doses were doubled. At this dose satisfactory depression of the first twitch was achieved. Neostigmine 5.0 mg produced adequate reversal of residual neuromuscular blockade and the train-of-four twitch response recovered to normal levels. With reduced dosage and with careful neuromuscular monitoring. vecuronium can be used safely in the myasthenic patient.

The effects of atracurium (initial dose 0.5 mg kg-1; incremental doses 0.2 mg kg-1) and vecuronium (initial dose 0.1 mg kg-1; incremental doses 0.04 mg kg-1) are described in patients with portal hypertension and some degree of liver dysfunction, and the findings compared with those from normal patients. With these doses there was no evidence of gross resistance to the two neuromuscular blockers in the patients with liver problems, although the duration of action of the initial dose was somewhat shorter, and the same may have been true of incremental doses. The method of elimination would suggest that atracurium may be the better drug in patients with severe liver dysfunction, but the use of small doses of vecuronium is not contraindicated in this type of patient.

One hundred general surgical patients were subjected to a form of personality assessment (Eysenck and Eysenck, 1964) the day before operation. Anaesthesia was standardized using light general anaesthesia, a muscle relaxant and controlled ventilation. The day after surgery patients filled in a standardized postoperative questionnaire about complaints concerning their visit to theatre. The patients were more “neurotic” (had higher N scores) than the general population; they also had a higher lie (L) score, and this tended to increase with age. The N score was greater in those awaiting upper abdominal operations than in those awaiting other procedures, and greater in females than in males. Pain was the most conspicuous postoperative complaint, despite the use of conventional analgesia. Preoperative anxiety was also prominent, as were complaints related to the passage or presence of a nasogastric tube. There was a positive correlation between N score and complaints of anxiety, and between N score and total number of complaints, but not between N score and complaints of pain.

SUMMARY Recent work has suggested that the term pK1′ in the Henderson-Hasselbalch equation may show wider variation than has been thought, and it seemed possible that the generally accepted values might not apply to women in labour. pK1′ was therefore determined experimentally in twenty volunteers in normal labour using arterialized venous blood. pH was measured by the glass electrode, Pco2 by the carbon dioxide electrode and Cco2 by the manometric apparatus of Van Slyke. The value so obtained was 6.106 at 38°C (with a standard deviation of 0.011). This was identical with the value obtained from ten non-pregnant controls and accords well with the value generally accepted as normal. This finding demonstrates the validity of the use of such nomograms as those of Siggaard-Andersen (1962a, 1963) and incidentally confirms the existence of a metabolic acidosis during labour.

The effect of halothane on experimental ischaemic muscle pain has been studied in 18 human volunteers. The submaximum effort tourniquet test was used in this investigation because it has been shown by previous workers to be a sensitive experimental test of analgesia. Two concentrations of halothane (0.25 and 0.35%) were compared with nitrous oxide (30%) in a controlled experiment. It was found that halothane 0.35% is of the same order of effectiveness as an analgesic as is nitrous oxide 30%. Halothane 025% appeared to have no analgesic action, and the possibility of a slight antanalgesic action at this concentration could not be eliminated. The practical effects of this finding are reviewed, and it is suggested that this finding taken with the work of other investigators indicates that halothane should be considered as an analgesic drug, and that the application of the term antanalgesic to this agent is misleading.