Neonatal gut function, measured by the one hour blood D (+) xylose test: influence of gestational age and size.

D(+) Xylose absorption, assessed by one hour blood xylose levels, has been measured after intraduodenal infusion of the sugar in 35 infants of differing gestational age and size. The test was performed between the 2nd and 6th days of life. Full-term appropriately grown infants had higher blood xylose levels (1.41+/-0.07 mmol/l) at one hour than pre-term appropriately grown infants (1.17+/-0.07 mmol/l; P less than 0.05), or 'light for dates' infants, both full-term (0.73+/-0.06 mmol/l; P less than 0.001) and pre-term (0.96+/-0.17 mmol/l; P less than 0.05). Serial studies of 11 infants were made two to five times between the 3rd and 20th day of life. The levels for one hour xylose rose in all groups, but the 'light for dates' infants showed the least rise. There was no sign of catch-up in this group, and some results appeared to fall further behind those of appropriately grown infants. These results suggest that the primal small intestine is maturing in the perinatal period, and that intrauterine growth retardation may impair intestinal absorption. The nutritional significance is not known.     

Dynamic changes of cerebrospinal fluid in upright and recumbent shunted experimental animals.

The effect of positional change on intracranial CSF pressure, valve flow rates and atrial pressures were studied in 40 experimental dogs. The flow rate with a 30 to 60 mm H2O Holter valve changed from the recumbent to the head-up position: during the first minute it increased 2 1/2 times and then progressively decreased to become stabilized 20-30 min later at a value slightly lower than the head-up value. At the same time pressure dropped rapidly to -23 mm H2O and then slowly, during 30 min to -120 mm H2O. In dogs without a shunt the pressure drop was initially similar to that of shunted dogs but recovered to almost the initial positive pressure in 30 min. The flow rate from a reservoir to the atrium through a shunt system when changing to the head-up position showed a siphon effect. Atrial pressure does not change with positioning. The findings were similar with cisternal-peritoneal shunts. Flow rate, therefore, increase in the head-up position. Negative intracranial CSF pressure was due to a siphon effect through the shunt system.