Peripartum changes in gastric emptying.

Applied potential tomography was used to measure changes in gastric emptying during the peripartum period. Gastric emptying was measured sequentially in each of 10 healthy patients at 37-40 weeks gestation, 2-3 days postpartum and after the 6-week postnatal assessment (control). Mean (SD) times to 50% emptying were 15 (6.05), 11 (5.9) and 15 (5.5) min, respectively. There was no statistically significant change in gastric emptying as a result of pregnancy in this group of women. Retrospective power analysis (assuming alpha = 0.05 and beta = 0.20) shows the study design was adequate to detect a difference of 8 min.

Effect of oral liquids and ranitidine on gastric fluid volume and pH in children undergoing outpatient surgery.

Eighty-eight children (mean age 5.6 yr, range 1-14 yr) about to undergo elective outpatient surgery were randomly assigned to four groups. All children were given phenolsulfonphthalein (PSP) orally 2-3 h before the scheduled time of surgery as a marker dye to assess gastric emptying. Immediately after receiving PSP they were given: group A--liquids, up to 5 ml/kg + placebo (glucose water 0.2 ml/kg); group B--liquids, up to 5 ml/kg + ranitidine 2 mg/kg in glucose water 0.2 ml/kg; group C--placebo only; group D--ranitidine only. Gastric contents were aspirated after induction of anesthesia. Mean volume (range) in ml/kg of aspirated gastric fluid in each group was: group A--0.34 (0-1.0); group B--0.17 (0.07); group C--0.25 (0-1.1); group D--0.16 (0-0.6). The pH mean (range) value was: group A--1.83 (0.9-3.6); group B--4.76 (2.0-7.7); group C--2.10 (1.2-4.1); group D--3.97 (1.3-7.3). PSP could not be detected in the gastric samples from children in whom the ingestion-sampling interval was more than 2.25 h. In comparison with prolonged starvation, administration of oral liquids without ranitidine 2-3 h preoperatively did not produce a significant increase in mean volume of gastric aspirate, and there was no increase in the number of patients with gastric aspirate greater than 0.4 ml/kg. Administration of ranitidine with or without fluids resulted in a decrease in both volume and acidity of gastric contents.

Comparison of the effects of high frequency oscillation and controlled mechanical ventilation on hyaline membrane formation in a rabbit model of the neonatal respiratory distress syndrome.

Saline lavage of the lungs of eight anaesthetized New Zealand White rabbits was performed to produce a surfactant-depletion model of the neonatal respiratory distress syndrome. A characteristic change in the shape of the pressure-volume curve occurred, with the appearance of an inflection point on the inspiratory limb. The animals were treated with high frequency oscillation (HFO) at 15 Hz and the results compared with those of a previously studied group of eight similar rabbits treated with controlled mechanical ventilation (CMV) with end-expiratory pressure equal to the pressure at the inflection point, but with the same mean airway pressure of 15 mm Hg. The animals treated with HFO had significantly higher arterial oxygen tensions and end-expiratory lung volumes than those treated with CMV, but there was no significant difference between hyaline membrane scores. Although there was no significant difference in mean survival times, five of the HFO treated animals showed reversion of the shape of their pressure-volume curves towards the prelavage configuration, suggesting a recovery of surfactant function.

Effects of positive end-expiratory pressure on hyaline membrane formation in a rabbit model of the neonatal respiratory distress syndrome.

Sixteen rabbits were anaesthetized and subjected to saline lavage of the lungs to produce surfactant deficiency. This resulted in an arterial oxygen tension of less than 12 kPa on 100% inspired oxygen and an inflection point on the pressure-volume curve at a pressure of 8-12 mmHg. After lavage the animals were randomly assigned to receive either conventional mechanical ventilation (CMV) with a positive end-expiratory pressure (PEEP) of 1-2 mmHg (group I - low PEEP) or CMV with PEEP equal to the inflection point pressure (group II - high PEEP). Mean airway pressures were kept at 14-16 mmHg in both groups by increasing the inspiratory:expiratory time ratios in the low PEEP group. The 5-h protocol was completed by 4 animals in group I and 6 animals in group II, early death usually being associated with a metabolic acidosis. On 100% oxygen, the mean PaO2 at 2-h post-lavage was 15.2 +/- 8.3 kPa in group I and 39.6 +/- 21.8 kPa in group II. Group I had much lower end-expiratory lung volumes (3.0 +/- 1.5 ml above FRC) than group II (34.9 +/- 12.2 ml above FRC). Histological examination of the lungs revealed significantly less hyaline membrane formation in group II (p = 0.001). Thus, the prevention of alveolar collapse by the use of high PEEP levels appears to reduce lung damage in this preparation.