Anaesthesia
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Mechanical ventilation with air-oxygen mixtures during total intravenous anaesthesia is discussed with the associated problem of obtaining a medically suitable source of air in British rooms. Independently powered ventilators capable of entraining filtered room air were thought to be the best solution. The Penlon Nuffield Series 400 ventilator was modified and assessed for use in this mode. ⋯ The entrainment system ensured good mixing of the entrained air and oxygen and allowed accurate determination of oxygen concentration in the patient system using a suitable nomogram and without an oxygen analyser. An assessment of one-way patient valves was also undertaken. The Laerdal valve was found to be the most suitable for use with the system described.
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A new simple anaesthetic breathing system is described which has been designed to incorporate into a single system advantages of Mapleson A, D and E type systems. Coaxial and non-coaxial versions are available. The system can be used for adults, children or neonates and allows both spontaneous or controlled ventilation with low fresh gas flows at all times. ⋯ The system is safe, simple in design and operation, and is easily sterilized. Further it offers low resistance to expiration and facilitates scavenging at all times which, with low anaesthetic gas flows, permits complete theatre pollution control. Its potential application in academic and rural environments and major advantages over the circle absorber system are discussed.
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The incidence of hypotension occurring in women undergoing Caesarean section with epidural analgesia was investigated in 60 patients receiving an intravenous preload of two litres Hartmann's solution. Hypotension occurred in only 6.7% of patients. Central venous pressure measurements in 20 patients confirmed the safety of the technique. A comparison is made with other preloading techniques.