Effect of repetitive umbilical cord occlusions on neuronal brain activity measured by the cerebral function analyzing monitor and histologic outcome in immature fetal sheep

OBJECTIVE: To examine the effect of repetitive total umbilical cord occlusi ons on electrocortical brain activity as measured by cerebral function anal yzing monitoring (CAFM) and the histologic outcome in immature sheep fetuse s. STUDY DESIGN: We performed brief repeated total umbilical cord occlusions, two every 5 minutes, in 12 immature sheep fetuses (at 90 days of gestation, term 147 days) until fetal mean arterial pressure dropped below 50% of bas eline value during two successive occlusions. A pair of electrodes was inse rted on the parietal dura for recording of electrocortical brain activity ( ECoG). Off-line ECoG signal processing consisted of amplitude integrated an alysis (CFAM) and spectral analysis. Fetal blood gas analyses were performe d at regular intervals just before subsequent umbilical cord occlusions. Th ree days after the occlusion neuronal damage was evaluated histologically i n three regions of the fetal brain. RESULTS: CFAM amplitude parameters decreased significantly during the first occlusion and remained so during the entire repetitive occlusion period (a nalysis of variance [ANOVA]; P < .05). Spectral analysis of the ECoG signal demonstrated no changes in the distribution of frequency bands. Progressiv e acidemia and hypotension developed with ongoing occlusions. Five fetuses died at the end or shortly after the entire repetitive occlusion period. No neuronal damage or macroscopic intraventricular and/or germinal matrix hem orrhage was observed in the surviving fetuses. CONCLUSION: Repetitive umbilical cord occlusions in immature sheep fetuses resulted in functional, not structural changes of the fetal brain in surviv ing fetuses. At this gestational age, amplitude analysis is more sensitive than spectral analysis of the ECoG signal to functional changes of the comp romised fetal brain. (J Soc Gynecol Investig 2000;7;218-23) Copyright (C) 2 000 by the Society for Gynecologic Investigation.