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We have compared the protective effect of 1000 ml preload with 200 ml preload of crystalloid solution, administered during the 10 min before spinal anaesthesia was induced, in 60 healthy women with no fetal compromise undergoing elective Caesarean section. The spinal anaesthetic was managed identically in both groups by an anaesthetist who was unaware of the volume of fluid administered. A prophylactic infusion of ephedrine 60 mg in Hartmann's solution 500 ml was given according to maternal arterial pressure. Hypotension was defined as > or = 30% reduction from baseline or < 90 mm Hg, and was treated by i.v. ephedrine bolus doses. There was no significant difference in ephedrine requirements between the two groups or in the incidence, severity or duration of hypotension: 10 women in the 1000-ml group, five episodes lasting > or = 3 min compared with nine women in the 200-ml group, four lasting > or = 3 min. There was no difference between neonates in each group. We have now abandoned the routine of preloading before regional anaesthesia.

This study analyzes the differences between wet and dry swallows; a manofluorogram is used to determine forces that affect pharyngeal bolus flow. By defining bolus pressures, many of the limitations of pharyngeal manometry are surmounted. This makes manometry a more useful clinical tool. The study results indicate that only a small portion of pharyngeal-generated pressure is directly applied to the bolus. The manofluorogram demonstrates that bolus transit relies on the synergistic action of two pumps--the oropharyngeal propulsion pump and the hypopharyngeal suction pump. A technique is illustrated for quantifying the forces that affect bolus flow. Quantification of force can differentiate abnormal forces responsible for lingual, pharyngeal, and hypopharyngeal pathology in dysphagic patients. The degrees of impairment can be measured.

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