Brain stem auditory-evoked response in relation to neonatal glucose metabolism

Imprecise control of glucose homeostasis is a hallmark of neonatal glucose metabolism. A relatively wide range of glucose concentrations is considered 'euglycemic' (2.22-6.94 mmol/l, 40-125 mg/dl) in the neonatal period. We investigated the effects of a wide range of glucose concentrations on brain stem conduction time (BCT) I-V interpeak latency or prolonged wave V latency. Neonates were assessed by brain stem auditory-evoked response followed immediately by heelstick sampling to determine the blood glucose concentration. Twenty-seven appropriate for gestational age (AGA) term neonates (birth weight 3,245 +/- 766 g, mean +/- SD; gestational age 39 +/- 2 weeks) were studied 3.1 +/- 3.7 days after birth. Twenty-three AGA preterm neonates (birth weight 2,175 +/- 477 g; gestational age 35 +/- 1 weeks) were studied 6.0 +/- 7.2 days after birth. Brain stem conduction time wave I-V interpeak latency and wave V latency were determined in two trials using a Grason-Stadler ABR screener at a 60-decibel stimulation level in the right ear. Neonates were studied between 33 and 40 weeks gestational age. Although the blood glucose concentration ranged from 1.38 to 6.83 mmol/1 (25-123 mg/dl), there was no correlation between either brain stem conduction time wave I-V interpeak latency or wave V latency and blood glucose concentration. We conclude that alterations in glucose concentration within the generally accepted neonatal euglycemic range do not effect the functional status of the brain stem auditory pathway. We suggest that the data can be interpreted to affirm that tighter clinical control of glucose homeostasis is probably not required in the neonatal period.