Why a Propofol Infusion Should Be the Anesthetic of Choice for Auditory Brainstem Response Testing in Children.

BACKGROUND: Auditory brainstem response (ABR) testing is considered to be relatively resistant to effects of volatile anesthetics. The impact of newer anesthetics on interpretability of ABR testing is unknown. This study compared sevoflurane versus propofol anesthesia on qualitative interpretability of ABR click-testing in children. METHODS: This prospective double-blind crossover study enrolled children (≤18 years old) receiving general anesthesia for elective ABR testing. All subjects received both sevoflurane and propofol anesthesias in the same ABR testing session. Deidentified ABR data were reviewed by 5 audiologists (blinded to anesthetic and patient) to determine threshold levels for hearing loss. The primary outcome was qualitative interpretability (false positive) of ABR click-testing. RESULTS: Each patient was tested at 4 different intensities in each ear: generating 624 records under each anesthetic, for a total of 1248 records. A few patients were tested at 5 different intensities in a single ear accounting for the additional 11 records, yielding 1259 records. Under sevoflurane anesthesia, 21 of the same patients (37 ears) were identified with abnormal ABR levels consistent with hearing loss (one or both ears). The probability of a patient being diagnosed with hearing "loss" in one or both ears was significantly less with propofol versus sevoflurane anesthesia (mid P =.0312). If patients with bilateral loss are compared, the mid P value is 0.0098. The effect size based on patients was medium to large, with a minimum value of Cohen w = 0.320. CONCLUSIONS: Sevoflurane produced more false positives for hearing loss and suggested more severe hearing loss than propofol. False-positive ABR tests, produced by certain anesthetic agents, can have significant life-long impact and negative psychosocial and developmental implications. Use of the intravenous anesthetic propofol is superior to sevoflurane for ABR testing in children.

Characterization of acoustic noise in a neonatal intensive care unit MRI system.

BACKGROUND: To eliminate the medical risks and logistical challenges of transporting infants from the neonatal intensive care unit (NICU) to the radiology department for magnetic resonance imaging, a small-footprint 1.5-T MRI scanner has been developed for neonatal imaging within the NICU. MRI is known to be noisy, and exposure to excessive acoustic noise has the potential to elicit physiological distress and impact development in the term and preterm infant. OBJECTIVE: To measure and compare the acoustic noise properties of the NICU MRI system against those of a conventional 1.5-T MRI system. MATERIALS AND METHODS: We performed sound pressure level measurements in the NICU MRI scanner and in a conventional adult-size whole-body 1.5-T MRI system. Sound pressure level measurements were made for six standard clinical MR imaging protocols. RESULTS: The average sound pressure level value, reported in unweighted (dB) and A-weighted (dBA) decibels for all six imaging pulse sequences, was 73.8 dB and 88 dBA for the NICU scanner, and 87 dB and 98.4 dBA for the conventional MRI scanner. The sound pressure level values measured on the NICU scanner for each of the six MR imaging pulse sequences were consistently and significantly (P = 0.03) lower, with an average difference of 14.2 dB (range 10-21 dB) and 11 dBA (range 5-18 dBA). The sound pressure level frequency response of the two MR systems showed a similar harmonic structure above 200 Hz for all imaging sequences. The amplitude, however, was appreciably lower for the NICU scanner, by as much as 30 dB, for frequencies below 200 Hz. CONCLUSION: The NICU MRI system is quieter than conventional MRI scanners, improving safety for the neonate and facilitating siting of the unit within the NICU.

Universal newborn hearing screening: fine-tuning the process.

PURPOSE OF REVIEW: Universal newborn hearing screening (UNHS) is rapidly becoming the standard of care in hospitals across the country. The goals of Healthy People 2010 are to provide newborn hearing screening to all infants, ensure follow-up audiologic evaluations by 3 months of age, and provide smooth transition to early intervention by 6 months of age. Programs implemented in the 1990s are beginning to report data that will be useful to states new to screening. This article reviews recent trends, suggests appropriate screening protocols, and identifies areas for improvement in UNHS. RECENT FINDINGS: Recent studies indicate the following: (1) screening programs can be cost-effective with low referral rates; (2) maternal stress is not necessarily a byproduct of screenings that end in referral; and (3) developmental outcomes for hearing-impaired infants born in screening hospitals are particularly encouraging. Areas for improvement include the following: (1) compliance in follow-up testing and (2) the establishment of a cohesive multidisciplinary team to manage the infant and provide support to the family. SUMMARY: Hearing screening is only the first step in the care of a hearing-impaired infant. Programs need to ensure that families understand the necessity of follow-up testing without creating undue stress. The transition to early intervention should be seamless, with a cohesive team of health care professionals capable of providing medical, audiologic, communication, and educational management for the infant as well as emotional support for the family.