British journal of anaesthesia
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Eight patients with a history of failed tracheal intubation during pregnancy were investigated by x-ray laryngoscopy after delivery. Partial elevation of the epiglottis with no view of glottic structures was found in five patients who were therefore considered to still present difficulty. ⋯ Relatively few abnormal anatomical indices were seen in these patients and this was in keeping with the level of difficulty encountered. An angular measure of jaw protrusion from a line joining the upper incisors and a point just above and anterior to the vocal cords, to the mid-point on the inner surface of the mandible was useful: the lower angle of this triangle was as important as the angle at the incisors.
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Comparative Study
Carboxyhaemoglobin concentrations, pulse oximetry and arterial blood-gas tensions during jet ventilation for Nd-YAG laser bronchoscopy.
Oxygen saturation measured with pulse oximetry (SpO2) is overestimated in the presence of carboxyhaemoglobin (COHb). Smoke produced during laser resection of tracheobronchial malignancies may increase concentrations of COHb. We have measured COHb concentrations in 14 patients undergoing laser resection and compared SpO2 with functional oxygen saturation (SaO2) to ascertain if pulse oximetry is an accurate monitor of oxygen saturation. ⋯ The mean difference between SaO2 and SpO2 was 1.13% (95% confidence interval 0.70-1.56%). Oxygen saturation may therefore safely be monitored by pulse oximetry in patients managed by our technique. Empirical setting of a jet ventilator provided acceptable blood-gas tensions, although sometimes it was necessary to increase the FlO2 to greater than 0.3 to maintain oxygenation.
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We have studied eight patients with a history of difficult tracheal intubation, using x-ray laryngoscopy and local anaesthesia, a curved Macintosh blade and a standard intubating position. The view obtained was better than recorded previously during general anaesthesia in two patients, and in a third the x-ray showed that positioning the blade tip beneath the epiglottis would have improved vision, suggesting that reproducibility of the assessment may not be consistent. The "ease of intubation" and "complementary" angles may be helpful in the assessment of such patients. ⋯ In the absence of muscle paralysis, removal of the blade caused immediate correction. However, during anaesthesia with neuromuscular block it is suggested that this not only occurs more readily but, may not correct when the blade is removed. Iatrogenic airway obstruction during moderately difficult tracheal intubation may be common and should be anticipated.
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During an attempt to measure renal function during operation in six patients undergoing major abdominal surgery involving intestinal resection and blood loss in excess of 300 ml, it became apparent that the conventional recommendation for i.v. crystalloid fluid of 5-10 ml kg-1 h-1 was not sufficient to maintain cardiovascular stability and urine output, but a volume of 15 ml kg-1 h-1, given to a subsequent six patients, was adequate. Administration of low sodium (glucose) solutions also produced biochemical abnormalities of a severity not documented previously. A survey of the published literature on volumes of crystalloid fluids used supports the contention that, during major surgery, crystalloid requirements may be of the order of 10-15 ml kg-1 h-1 rather than 5-10 ml kg-1 h-1.