Increased wave latency in auditory brainstem response to anemia in newborn and adult sheep.

The objective of the present study was to determine whether phlebotomy-induced anemia in newborn lambs and adult sheep results in prolonged auditory brainstem response (ABR) wave latencies, and if found, whether developmental differences exist between the two groups. Among newborn lambs, hemoglobin (Hb) levels were reduced from 100-120 to 30-50 g/l over a 3-day period. Over the next 2 days, serial red blood cell transfusions were administered to restore Hb to pre-phlebotomy levels. In adult sheep, comparable levels of phlebotomy-induced anemia were achieved within a 24-hour period, after which Hb levels returned to pre-phlebotomy levels. During the induction of anemia and its reversal, a significant (p < 0.05) increase in ABR latency followed by a return to pre-anemia ABR latencies that was most prominent in the peripheral auditory pathway was observed in both newborn and adult sheep as Hb levels fell below 50 g/l (p < 0.05). There was no difference between adults and newborns in ABR latency relative to the Hb level at which ABR wave latencies increased. We speculate that ABR wave latency prolongation might serve as an indicator of the need for red blood cell transfusion.