117: Magnesium sulfate (MgSO4) dose and timing, and umbilical cord Mg++ concentration: Relationship to cerebral palsy (CP)

Abstract

To assess MgSO4 dose and timing (as actually used) and total umbilical cord blood Mg++ concentration in relationship to CP. Data are from a randomized clinical trial of MgSO4 to prevent CP among the offspring of women with anticipated preterm delivery from 24-31 weeks′ gestation. The planned dosing regimen was a 6-gm loading dose, 2 gm/hr infusion for up to 12 hrs, discontinuation if delivery not imminent, and re-treatment through 336 weeks′ gestation with the same regimen prior to delivery. We excluded infants with major congenital anomalies and performed logistic regression analyses adjusted for gestational age at birth. Of 2,056 children assessed for cerebral palsy, 1,311 (64%) underwent umbilical cord total Mg++ measurement. Median cord Mg++ (meq/L) was 2.6 (interquartile range [IQR] 1.7 −3.4) in the active group (n = 622) vs. 1.6 (IQR 1.4 −1.7) in the placebo (n = 689). Cord Mg++ was negatively but not significantly correlated with CP, adjusted OR 0.76, 95% CI 0.54-1.1. Among 986 MgSO4-allocated pregnancies (median dose 32.0 gm, IQR 29.0-45.1), dose and exposure were characterized as 1) any MgSO4 in last 3, 12, or 24 hrs before delivery; 2) total dose; and 3) duration in the same time intervals. In all of these exposure/dose analyses (n =10), receipt, dose, and duration of MgSO4 were not significantly related to CP risk; however, in all but one the association was in the negative direction (i.e., ↑ MgSO4, ↓ CP). The low (3.7 %) rate of CP among the children in the MgSO4-allocated pregnancies, and the 4.0% rate among those with a cord blood Mg++ measurement limited our statistical power. Our analyses do not support any specific modification of the intravenous MgSO4 dosing regimen that reduced the rate of cerebral palsy in our clinical trial.