Anaesthesia
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Difficult intubation has been classified into four grades, according to the view obtainable at laryngoscopy. Frequency analysis suggests that, in obstetrics, the main cause of trouble is grade 3, in which the epiglottis can be seen, but not the cords. This group is fairly rare so that a proportion of anaesthetists will not meet the problem in their first few years and may thus be unprepared for it in obstetrics. ⋯ Laryngoscopy is carried out as usual, then the blade is lowered so that the epiglottis descends and hides the cords. Intubation has to be done blind, using the Macintosh method. This can be helpful as part of the training before starting in the maternity department, supplementing the Aberdeen drill.
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A hypothesis is suggested that the initial or 'true' negative pressure encountered when a needle first enters the epidural space is due to initial bulging of the ligamentum flavum in front of the advancing needle followed by its rapid return to the resting position once the needle has perforated the ligament. The bulging has been confirmed to occur in fresh cadavers, and pressure studies carried out during performance of epidural blocks in patients lend weight to this hypothesis.
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Sixty-seven patients undergoing general anaesthesia for exodontia as outpatients were studied in order to measure the levels of oxygen saturation. Both the anaesthesia and extractions were performed by fourth year dental undergraduates working under direct supervision. Falls in oxygen saturation in excess of 5% were found in three groups of patients receiving 20%, 25%, and 30% oxygen in the inspired mixture.
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Ranitidine 150 mg was given to 126 patients requiring elective Caesarean section under general anaesthesia: 43 women had ranitidine alone, 43 had this supplemented by a pre-induction dose of sodium citrate and 40 patients had ranitidine plus sodium bicarbonate. All three sub-groups provided satisfactory gastric pH and volume. ⋯ In the citrate sub-group there was one patient with a gastric pH less than 2.5 (mean pH 6.2, SEM 0.13 range 2.1-8.4). In the bicarbonate sub-group the lowest gastric acidity was 3.8 (mean pH 8.3, SEM 0.11 range 3.8-9.83).