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We report two cases of severe upper airway obstruction caused by supraglottic oedema which developed rapidly at the time of anaesthesia. Conventional methods to relieve the obstruction failed and it was only overcome when a laryngeal mask airway (LMA) was inserted and positive pressure applied manually during inspiration. In one case a fibrescope was passed via the LMA and this revealed two cushions of oedematous false vocal cords protruding into the bowel of the LMA which were pushed out of the way when positive pressure was applied during inspiration. We believe that the LMA should be considered in the emergency management of severe upper airway obstruction even when this involves supraglottic oedema.

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The action of bile salts upon the rat blood-brain barrier (BBB) was assessed in the absence of energy-yielding metabolism. Brains were perfused in situ with a Ringer solution for 5 min followed by a 1 min perfusion containing either sodium deoxycholate (DOC), taurochenodeoxycholate (TCDC), or Ringer/DNP. The integrity of the BBB was then determined by perfusing with the radiotracer [14C]mannitol for 2.5 min. Alternatively, the brains were perfusion fixed for ultrastructural assessment. At 0.2 mM DOC, the BBB remained intact and the cerebral ultrastructure was similar to the controls. At 1 mM and above, disruption of the BBB became evident. At 2 mM, the cerebral cortex became severely vacuolated, with damaged endothelium and collapsed capillaries. With TCDC, BBB disruption occurred at 0.2 mM without any apparent ultrastructural damage to the microvasculature. Following 2 mM TCDC, similar, but less widespread, structural changes to the 2 mM DOC-perfused animals was apparent. Opening of the BBB occurred at a concentration lower than that required to cause lysis of either red blood cells or cultured cerebral endothelial cells. It is proposed that the effect of bile salts at concentrations of 1.5 mM and above is largely due to their lytic action as strong detergents on endothelial cell membranes, but that at lower concentrations a more subtle modification of the BBB occurs.

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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. An entrainment adapter and circuit was devised which allowed the ventilator to entrain more than sufficient ambient air, premixed with added oxygen for patient ventilation even under adverse conditions. 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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The brains of 9 spider monkeys, inoculated intracerebrally with brain suspension from kuru patients and of 3 normal control monkeys have been studied. All the animals were killed by perfusion with fixative, 8 during early incubation (ranging from 2 to 40 weeks) when healthy and free from neurological signs, one after 122 weeks when the disease was fully established. The most striking feature seen in every brain between the incubation times of 4 and 40 weeks was the formation of multilaminated membranes (ACPMs). These affected stretches of two apposed, mostly neuronal, plasma membranes over variable distances and created the impression of complex ribbon-or cord-like junctions. Their number varied with the length of incubation, reaching a peak at 13 weeks and declining thereafter. ACPMs were found throughout the grey matter, but they were most numerous in phylogenetically older regions of the brain, regions which also show the severest lesions in human kuru. It is suggested that ACPMs are initially due to an excessive synthesis of some membrane constituent by the perikaryon and various possibilities for their genesis are discussed. The hypothesis is advanced that they may be due to the reactivation of embryonic growth mechanisms and represent abortive junctions which, being formed in mature neurons, take a rather bizarre shape. Other changes such as the formation of somatic spines, an excessive number of dendritic spines including a high proportion with long tortuous necks, and the presence of binucleated neurons and numerous growth cones, point to the similarly immature pattern and would support this hypothesis. The material provided ample evidence that ACPMs, which can occupy as much as 26 per cent of a dendritic surface, give rise to intracytoplasmic vacuoles, which may therefore be regarded as secondary to a primary change in the permeability of the plasma membrane at the site of ACPMs. Individual single vacuoles could often build up into complex soap-bubble-like arrays, which were interpreted as the ultrastructural equivalent of histological status spongiosus. There is some evidence that the development of status spongiosus in other transmissible spongiform encephalopathies follows the same pattern.

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A Penlon Nuffield Series 200 Ventilator, adapted for use as a high frequency jet ventilator, was used to treat a patient with adult respiratory distress syndrome. Adequate alveolar ventilation with this method was achieved with lower mean intrapulmonary pressure (5.4 cmH2O) than with conventional intermittent positive pressure ventilation (IPPV) (6 cmH2O). An improved cardiac output was also apparent, as judged by a better systemic blood pressure [105/50 mmHg for high frequency jet ventilation (HFJV) compared to 90/40 mmHg for IPPV] and a lower central venous pressure 6 cmH2O for HFJV as compared to 9.5 cmH2O with conventional IPPV. During HFJV, the patient's need for sedatives and narcotics was reduced. This allowed an assessment to be made of any potential neurological damage caused by the cervical fracture. An assessment had not been possible during conventional ventilation due to the heavy narcotic and sedative regime required to settle the patient. This case report provides further evidence that HFJV is a useful adjunct in the management of patients requiring mechanical ventilation and also that the Penlon Nuffield Series 200 Ventilator is capable of high frequency jet ventilation.

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Intravenous salbutamool or aminophylline was administered under double-blind conditions to 20 asthmatic patients presenting with severe dyspnoea and needing urgent treatment with bronchodilators. Ten patients received salbutamol and ten patients received aminophylline. Objective measurements showing improvement were recorded in nineteen patients. A greater response was produced by salbutamol although this failed to reach statistical significance. Neither drug affected pulse or blood pressure. It is suggested that intravenous salbutamol is an effective bronchodialtor in the treatment of acute exacerbation of asthma or bronchitis.

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