Development of beta-adrenergic control of phospholipid secretion in rabbit lung.

Lung distension is associated with increased phospholipid secretion into the air spaces. Basal, lavage-induced, and inflation-produced phospholipid secretion, in postmortem in situ lungs of newborn rabbits, were examined at three different levels of maturity, with and without 10(-3) M dl-propranolol. Lungs were lavaged with saline at successive 3- and 15-min time intervals to separate basal from lavage-induced secretion. Inflation-produced secretion was studied after static inflation at 30 cmH2O for 30 min. At 27.5 days gestation, basal secretion was undetectable, and neither lavage-induced nor inflation-produced secretion were influenced by propranolol. At 29.5 days gestation, basal secretion was only just detectable. Distension-associated secretion was increased over that present at 27.5 days gestation, and propranolol had a significant inhibitory effect, especially on lavage-induced secretion, in which the inhibition was shown to be rapidly reversible. There was a significant increase of basal secretion at 2.5 days postterm, possibly inhibited by propranolol. In addition, there was a further substantial increase of distension-associated secretion, and the inhibitory effect of propranolol persisted. These changes were independent of the sedimentation behavior of lavaged phospholipid. Overall, the results are consistent with evidence, produced in other laboratories, that there is an increasing density of sympathetic neurons and beta-adrenergic receptors in whole lung preparations during late gestation in the rabbit and suggest that granular pneumocytes, the presumed source of secreted phospholipid, take part in this developmental change.

Partial plasma exchange transfusion improves cerebral hemodynamics in symptomatic neonatal polycythemia.

Cerebral arterial pulsatile flow changes and the effect of partial plasma exchange transfusion on these pulsatile flow patterns were studied in neonatal polycythemia/hyperviscosity syndrome by transcutaneous Doppler technique. Twenty-two infants with cord blood hematocrit greater than 58% (greater than 2 SD above the mean) were studied from a total of 2,400 infants who were screened for cord hematocrit over a 6-month period. Each of 22 infants had the following initial studies: radial artery hematocrit, viscosity, intracranial pressure measurement, and anterior cerebral arterial Doppler study to determine pulsatility index, mean systolic, mean end diastolic, and mean flow velocities, and area underneath the curve of the velocity tracings/min. Twelve of 22 infants had radial artery hematocrit less than 63%, were normoviscous (less than 13.5 cps, 11.25 sec-1) and were designated as control infants. Ten (study infants) were polycythemic (hematocrit greater than or equal to 63%) and hyperviscous (greater than or equal to 13.5 cps, 11.25 sec-1). All study patients were treated by partial plasma exchange transfusion. Initial studies were repeated after exchange transfusion. Control infants were not treated. Prior to exchange procedure, the polycythemic hyperviscous infants had significantly higher hematocrit, viscosity, and pulsatility index; the other Doppler measurements and heart rate were lower than those of control babies. The exchange procedure resulted in significantly decreased hematocrit, viscosity, and pulsatility index and increase in the other Doppler measurements, heart rate, and intracranial pressure. All postexchange measurements of study infants were not statistically different from the control infants. These data suggest that neonatal polycythemia/hyperviscosity syndrome may be associated with abnormal cerebral hemodynamics that could improve with partial plasma exchange transfusion.

Intestinal perforations in infants with a very low birth weight: a disease of increasing survival?

Seventeen infants with a very low birth weight (VLBW) and spontaneous, non-necrotizing enterocolitis (NEC), intestinal perforations are presented; 14 of them were seen in the past 3 years. A comparison with 16 surgically treated NEC infants (< 1,000 g) is provided. At our institution, the yearly survival of VLBW infants increased from 54% to 90% over the past 6 years. All 17 non-NEC patients were operated on, and 15 (88.2%) survived. Ileal perforations were observed frequently. Initial enterostomies were followed by reanastomosis at an average age of 3 months. A 22.6-month follow-up was attained for all survivors. Non-NEC intestinal perforations in tiny neonates are increasing and constitute a challenging but treatable group. The improving survival rate of VLBW infants will probably be accompanied by a variety of complications.

Asymptomatic syndrome of polycythemic hyperviscosity: effect of partial plasma exchange transfusion.

We determined the cerebral hemodynamic changes in infants with asymptomatic polycythemic hyperviscosity syndrome and whether treatment with partial plasma exchange transfusion (PPET) would affect hemodynamics as well as outcome. From a routine cord blood hematocrit screening, 71 babies were identified as needing to be tested for polycythemic hyperviscosity. In addition to clinical evaluation, each infant had radial artery hematocrit and viscosity determinations, blood gas determinations, cerebral blood flow velocity studies, cranial ultrasonography, and noninvasive intracranial pressure determination. Babies with symptomatic hyperviscosity (n = 17) were treated by PPET, whereas those with asymptomatic hyperviscosity (n = 28) were randomly selected to have PPET (n = 14) or to be observed (n = 14). The remaining babies (n = 26) with normal viscosity served as control subjects. Both hematocrit and viscosity decreased after PPET but remained unchanged in babies with hyperviscosity who were merely observed. Reversal of cerebral blood flow velocity abnormalities was observed after PPET in the infants with symptomatic hyperviscosity, whereas those who had no symptoms had normal results on Doppler studies at the outset, and no significant changes occurred with either PPET or observation. There were two deaths in the group with symptoms. A total of 46 babies returned for follow-up evaluation at a mean age of 30 +/- 7.7 months. Outcome of the control group was no better than that of those who had hyperviscosity, and outcomes did not differ between the babies with symptomatic and those with asymptomatic hyperviscosity, nor between those treated with PPET and those who were only observed. Multivariate analysis revealed that other perinatal risk factors and race rather than polycythemia or PPET, significantly influenced long-term outcome.