Anaesthesia
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Comparative Study
A comparison of the performance of two types of infusion device.
The delivery performance of two types of infusion pump, the IVAC 711 series syringe driver and the IVAC 531 series drop-counter, was examined by measuring the output of 16 pumps. We found that despite careful attention to the setting up of all apparatus, the IVAC 711 series syringe drivers had a significant lag phase before output matched the set rate, and that this lag phase was more pronounced at low rates of infusion. This was not the case with the IVAC 531 series which delivered the set rate from the outset. We suggest, that when the timing and rate of an infusion of drug is important from the outset and when these types of pump are being used, that either the syringe driver pump is primed by a brief period of high rate infusion vented by a three-way tap or that a drop-counter pump is used.
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The use of the Association of Anaesthetists of Great Britain and Ireland checklist for anaesthetic machines, based on an oxygen analyser, was surveyed over a 5-week period in a teaching hospital. Fifty-five completed checklists were analysed; no problems developed during anaesthesia which were missed by the checklist. ⋯ The most frequent faults detected were the poor reliability of some oxygen analysers, absent ventilator disconnection alarms, and absent oxygen supply failure alarms on some older machines. Faults were found in 60% of the machines checked; 18% of these were deemed to be serious.
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The caudal limit of the thoracic paravertebral space was examined in 13 human cadavers. The origin of the psoas major muscle was found to completely seal off the paravertebral space below the level of the 12th thoracic vertebra. The possibility of caudal spread of a thoracic paravertebral block below this level through the paravertebral space would appear unlikely.
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A nasogastric tube was used to aspirate air insufflated into the stomach during intermittent positive pressure ventilation through a laryngeal mask airway and a tracheal tube. No difference was found in the amount aspirated between patients with a tracheal tube, a laryngeal mask airway with the nasogastric tube closed or a laryngeal mask airway with the nasogastric tube open, when the nasogastric tube was aspirated at 15 min intervals for the first hour of anaesthesia.