Side effects of 2 different dexamethasone courses for preterm infants at risk of chronic lung disease: a randomized trial.

OBJECTIVE: We hypothesized that a pulsed course of dexamethasone would result in better linear growth than a 42-day reducing course in preterm infants at risk for chronic lung disease of prematurity. STUDY DESIGN: Forty infants with a birth weight of < or =1,250 g who required mechanical ventilation at 7 days of age were randomly assigned to a repeatable 3-day pulse course of dexamethasone commencing immediately or a 42-day (long) course commencing at 14 days of age if they still required mechanical ventilation and supplemental oxygen. The primary outcome measure was linear growth at 36 weeks' postmenstrual age measured by knemometry. RESULTS: There was no difference in lower leg length at 36 weeks' postmenstrual age. Infants receiving the pulse course had lower rises in blood pressure, less myocardial hypertrophy, and less adrenal suppression. However, more infants required supplemental oxygen at 28 days' postnatal age (14/18 vs 8/21, P < .05) and 36 weeks' PMA (8/16 vs 5/20, P = .12). CONCLUSION: In preterm infants at risk for chronic lung disease, a pulsed course of dexamethasone has fewer side effects than a long course but may be less effective at preventing chronic lung disease.

The role of neonatal chest physiotherapy in preventing postextubation atelectasis.

We retrospectively assessed atelectasis in 297 postextubation radiographs from 220 babies who underwent ventilation over a 2-year period. All 95 babies in the first year received peri-extubation chest physiotherapy; none of the 125 babies in the second year received chest physiotherapy. There was no difference in the incidence of postextubation atelectasis between the two groups.

Chest physiotherapy may be associated with brain damage in extremely premature infants.

OBJECTIVES: To determine whether a characteristic form of brain damage (encephaloclastic porencephaly) was associated with chest physiotherapy treatment in preterm babies. METHODS: A retrospective case-control study was undertaken among 454 infants of birth weight less than 1500 gm cared for during the 3-year period of 1992 to 1994. Thirteen babies of 24 to 27 weeks of gestation who weighed 680 to 1090 gm at birth had encephaloclastic porencephaly. Twenty-six control subjects were matched for birth weight and gestation. RESULTS: The patients received two to three times as many treatments with chest physiotherapy in the second, third, and fourth weeks of life as did control infants (median 79 vs 19 treatments in the first 4 weeks, p < 0.001). Patients also had more prolonged and severe hypotension in the first week than did control subjects (median duration of hypotension 4 vs 0.5 days, p < 0.01), and were less likely to have a cephalic presentation (31% vs 81%, p < 0.01). Since December 1994 no very low birth weight baby has received chest physiotherapy treatment in the first month of life in our nursery, and no further cases have occurred. CONCLUSIONS: Encephaloclastic porencephaly may be a previously unrecognized complication of chest physiotherapy in vulnerable extremely preterm infants.

Solvent isotope effects on the hexokinase D reaction: evidence for the mnemonical interpretation of the kinetic co-operativity.

Hexokinase D ('glucokinase') from rat liver displays kinetic co-operativity with respect to glucose when studied in 1H2O, with a Hill coefficient of about 1.4 when the other substrate, MgATP, is present at a concentration of 4.3 mM. In 2H2O, however, this becomes negative co-operativity, with a Hill coefficient of about 0.6 under corresponding conditions. At high glucose concentrations there is a small normal isotope effect, but at low glucose concentrations there is a large inverse isotope effect. Graphical analysis shows that these results are consistent with the 'mnemonical' model for kinetic co-operativity, in which there are two forms of free enzyme with different affinities for glucose, if the principal effect of changing the solvent is to alter the relative magnitudes of the on rate constants for binding of glucose to the two forms of free enzyme.