Anaesthesia
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Seven different models of oxygen concentrators were purchased. The manufacturer's data were evaluated by a ranking method for operation at high temperature and high relative humidity, power consumption, warranty and cost. Measurements were then made of the oxygen concentration produced at maximum operating temperature. ⋯ All models delivered low oxygen concentrations at 40 °C and 95% relative humidity. Only two models delivered >82% at 35 °C and 50% relative humidity. Concentrators intended for use in countries with limited resources should be evaluated before they are purchased, by independent experts, using the methods described herein.
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There is currently no consensus regarding how to intervene in anaesthetic-induced hypotension. Whether or not the balance between cerebral oxygen supply and demand is maintained lacks adequate elucidation. It is thus intriguing to explore how cerebral tissue oxygen saturation is affected by anaesthetic-induced hypotension. ⋯ However, cerebral tissue oxygen saturation remained stable (67.0 (9.4) % vs 67.5 (7.8) %, p=0.6). These results imply that the fine balance between cerebral oxygen supply and demand is not disrupted by anaesthetic-induced hypotension. An interpretation based on neurovascular coupling and cerebral autoregulation is proposed.
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Cardiac arrest is associated with a very high rate of mortality, in part due to inadequate tissue perfusion during attempts at resuscitation. Parameters such as mean arterial pressure and end-tidal carbon dioxide may not accurately reflect adequacy of tissue perfusion during cardiac resuscitation. We hypothesised that quantitative measurements of tissue oxygen tension would more accurately reflect adequacy of tissue perfusion during experimental cardiac arrest. ⋯ After the return of spontaneous circulation, all measured parameters including brain oxygen tension recovered to baseline levels. Muscle tissue oxygen tension followed a similar trend as the brain, but with slower response times. We conclude that measurements of brain tissue oxygen tension, which more accurately reflect adequacy of tissue perfusion during cardiac arrest and resuscitation, may contribute to the development of new strategies to optimise perfusion during cardiac resuscitation and improve patient outcomes after cardiac arrest.
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Our hypothesis was that the incidence of malposition of a right-sided double-lumen endobronchial tube and right upper lobe collapse may increase when the distance between the carina and the distal margin of the right upper lobe orifice is less than 23 mm, measured from a computerised tomography scan. A total of 76 patients undergoing left-sided thoracic surgery were enrolled. Patients with a measured distance of <23 mm (n=38) were compared with age-, sex- and body mass index-matched patients with a distance≥23 mm (n=38). ⋯ The incidence of intra-operative malposition in the <23 mm group was also significantly higher than in the ≥23 mm group (31 (82%) vs 8 (21%), respectively, p<0.001). Right upper lobe collapse was detected postoperatively in five patients (13%) in the distance<23 mm group, compared to none in the ≥23 mm group. We recommend that the distance between the carina and the distal margin of the right upper lobe bronchus should be routinely measured on the pre-operative computerised tomography scan, and if it is <23 mm, consideration should be given to using a left-sided endobronchial double-lumen tube in preference to a right-sided one.