ABSTRACT
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.
Subject(s)
Anemia/physiopathology , Animals, Newborn/physiology , Evoked Potentials, Auditory, Brain Stem/physiology , Reaction Time/physiology , Anemia/etiology , Animals , Erythrocyte Transfusion , Hemoglobins/analysis , Phlebotomy , SheepABSTRACT
Thyroid hormone and the beta isoform of its receptor, Trb, are essential for normal development of the mammalian auditory system. We have analyzed auditory system function and structure in a mouse strain with a targeted Thrb mutation, Thrb(PV), which leads to the loss of binding of thyroid hormone (T3) to the Trb protein. Heterozygosity for the orthologous human THRB(PV) mutation and other similar mutations in human THRB cause resistance to thyroid hormone (RTH), which is occasionally associated with mild sensorineural hearing impairment. Auditory brainstem response analysis of heterozygous Thrb(PV)/+ mice demonstrates that they develop normal hearing. In contrast, Thrb(PV)/Thrb(PV) mice have severe hearing impairment that is already present at 3 weeks of age. This hearing loss is associated with disruption of postnatal morphogenesis of the tectorial membrane and organ of Corti. Comparison with the previously described phenotype of a Thrb -/- knockout strain suggests that Thrb(PV) disrupts the function of other genes that are critical for development and/or maintenance of these structures.
Subject(s)
Cochlea/abnormalities , Mutation/physiology , Thyroid Hormone Receptors beta/genetics , Triiodothyronine/physiology , Amino Acid Sequence/genetics , Animals , Animals, Newborn/growth & development , Cochlea/growth & development , Cochlea/physiopathology , Congenital Abnormalities/genetics , Congenital Abnormalities/physiopathology , Drug Resistance/genetics , Hearing/physiology , Humans , Mice , Mice, Transgenic/genetics , Molecular Sequence DataABSTRACT
Incidence studies estimate that 1-3 per 1000 full term normal neonates and 2-4 of high-risk newborns per 100 have severe bilateral hearing loss. In response, universal hearing screening has been proposed; however, choosing the most appropriate technology continues to be an obstacle. The purpose of the current preliminary study was to compare test results from thirty-two full-term newborns using three types of screening devices, Natus Algo 2 AABR, Otodynamics EchoCheck TEE, and Biologic AuDx DPE. Results indicate that the Natus had the highest pass percentage rate for the right and left ears at 97 and 91 respectively, while the other two devices had pass percentage rates between 31 and 56. Test duration time for the Natus was 22.5 minutes compared with 5.8-6.4 minutes for the other devices. Despite the longer duration time, our findings favor using the Natus, given its accurate representation of incidence data.
