Release: Embargoed until September 26
Contact: Ken Satterfield
(in New Orleans: 9/23-29 at 504-670-5409) [email protected]
NEWBORNS REQUIRING LENGTHY MECHANICAL VENTILATION ARE AT GREATER RISK FOR SENSORINEURAL HEARING LOSS
Duration of extracorporeal membrane oxygenation (ECMO), an effective treatment for respiratory failure in newborns, is key to potential hearing impairment
NEW ORLEANS -- Extracorporeal membrane oxygenation (ECMO) is an effective treatment for respiratory failure in newborns which has been available since the mid-1980s. Near-term and term infants with severe respiratory failure in whom mechanical ventilation techniques are inadequate to maintain oxygenation are potential ECMO candidates. ECMO involves placing these children on cardio-pulmonary bypass via placing a tube in the common carotid artery and jugular vein in the neck, a procedure which can be done in the neonatal intensive care unit. Cardio-pulmonary bypass provides the neonate's lungs a period for recovery without the potential damaging effects of mechanical ventilation.
The most common problems causing respiratory failure necessitating ECMO are Meconium Aspiration Syndrome (MAS), persistent pulmonary hypertension of the newborn (PPHN), respiratory distress syndrome, sepsis, and congenital diaphragmatic hernia (CDH). ECMO has resulted in survival of neonates who in the past would have succumbed to respiratory failure.
It is well known that some critically-ill newborns are at risk for sensorineural hearing loss (SNHL) including those with severe respiratory depression and prolonged mechanical ventilation.. Previous studies have reported the incidence of SNHL in ECMO survivors to range between 2.5 to 60 percent. This study was undertaken to compare the prevalence of sensorineural hearing loss among ECMO survivors to that in other infants with respiratory failure who did not require ECMO.
The authors of the study, "Sensorineural Hearing Loss in ECMO Survivors" are Nancy M. Young, MD, C. Anthony Hughes, MD, Gregory S. Bussell, MD, all from the Division of Pediatric Otolaryngology, Kimberly Molik, MD, and Marleta Reynolds, MD, from the Division of Pediatric Surgery, Children's Memorial Medical Center, Chicago, IL .
The results were presented before the American Academy of Otolaryngology--Head and Neck Surgery Foundation Annual Meeting and Oto Expo being held September 26-29, at the Ernest N. Morial Convention Center in New Orleans, LA. At the gathering, the Academy's 11,000 members will have the opportunity to hear the latest research in the diagnosis and treatment of disorders of the ear, nose, throat, and related structures of the head and neck.
Methodology:
Subjects were 89 of 146 survivors managed by the Children's Memorial Hospital ECMO program in Chicago, Illinois, between October of 1986 and December of 1993 for whom audiologic data were available. Of these 89 children, 77 underwent audiologic screening prior to or shortly after initial hospital discharge. Thirty-nine of these children had follow-up audiologic testing performed during scheduled developmental visits to the ECMO clinic. Twelve patients were not screened at the time of initial discharge, but subsequently underwent audiologic evaluation.
The control group consisted of 55 children with respiratory failure secondary to Meconium Aspiration Syndrome who did not require ECMO and for whom audiologic information was available. Fifty-four underwent hearing screening proximate to the time of initial hospital discharge. Follow-up testing was possible for only for fourteen patients, thirteen of whom had undergone initial hearing screening.
Results:
Of the 77 ECMO patients who underwent initial hearing screening via ABR, five (six percent) failed in at least one ear. Of these five patients, one was lost to follow-up, three were found on follow-up to have normal hearing, and one was diagnosed with SNHL. Additional findings included:
* Nine subjects who passed their initial hearing screen were later diagnosed with SNHL. Review of the follow-up audiologic data available on the 12 patients not initially screened revealed that three had SNHL. Overall, of the 51 ECMO patients in whom follow-up data were available, 13 (25.5 percent) were diagnosed with SNHL, and 12 required amplification. Nine of ten (90 percent) of the children diagnosed with SNHL had normal hearing at the initial screening. The average age at which SNHL was diagnosed in our ECMO survivors was 27 months, and, in the majority of cases, the hearing loss was down-sloping with a moderate-to-severe loss in the higher frequencies.
* Fifty-three of 55 patients in the control group underwent audiologic screening proximate to initial hospital discharge. Two (3.7 percent) failed the screening and were lost to follow up. Of the 14 patients who did return for audiologic evaluation, nine (64 percent) were diagnosed with SNHL, a significantly higher rate of SNHL than in the ECMO group. Eight of these nine children (88.9 percent) had passed their initial hearing screen, and all currently use amplification.
* When ECMO patients were analyzed by diagnosis, those with CDH had a 70 percent incidence of SNHL and were significantly more likely than other ECMO patients to develop hearing loss. ECMO patients with the diagnosis of MAS had only a 7.1percent rate of hearing loss, compared to 64.3percent in the MAS control group.
Conclusion: Time of mechanical ventilation was significantly related to SNHL in both the ECMO and control groups. The physiologic reason for this finding is likely multifactorial and requires further research. Centers who care for neonates with respiratory failure need to develop protocols that ensure long-term audiologic follow-up, regardless of whether ECMO intervention was necessary for survival.
The results agree with previous reports that neonates requiring ECMO are at risk for development of SNHL. Of the subjects, SNHL occurred in 13 (25. 5percent) children in the ECMO group. However, this number is skewed by inclusion of patients with CDH, a population known to have an extremely high probability of developing SNHL, as was found to occur in our subjects. When ECMO patients with an underlying diagnosis of MAS only are considered, SNHL occurred in 7.1 percent. In terms of the potential risk factors evaluated, only duration of mechanical ventilation was significantly related to SNHL. The more time children receive mechanical ventilation, the greater the likelihood of SNHL. This relationship was present regardless of whether the children were in the ECMO or control group.
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Editor's Note: For a copy of this study or an interview with Dr. Young, contact Ken Satterfield at 703-519-1563 (through 9-21); 9/23-29, call the Annual Meeting Newsroom at 504-670-5409.
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