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J Am Acad Audiol 9 : 367-370 (1998) Sensorineural Hearing Loss in ECMO Survivors Toni Mann* Karen Adamst Abstract Survivors of extracorporeal membraneous oxygenation (ECMO) treatment are at risk for §erious neurodevelopmental disorders or neurologic sequelae, but little has been reported about the prevalence of sensorineural hearing loss in these patients . Of 123 ECMO survivors born between 1987 and 1996, at least 30 survivors have confirmed sensorineural hearing loss . Progressive hearing loss has been confirmed in 10 subjects . Key Words: Extracorporeal membraneous oxygenation Abbreviations : ABR = auditory brainstem response, ECMO = extracorporeal membraneous oxygenation, NICU = neonatal intensive care unit ECMO AND HEARING LOSS E xtracorporeal membrane oxygenation (ECMO) is a form of cardiopulmonary support for full-term or near-term neonates who fail to recover from life-threatening pulmonary illnesses despite conventional medical management (Hofkosh et al, 1991 ; Robertson et al, 1995). The extracorporeal membrane oxygenator is essentially a simplified heart-lung machine. Cannulas draw blood from the right atrium and return it to the aorta, thereby functionally bypassing both the lungs and the heart for prolonged periods of time. The extensive course of treatment can result in severe neurologic sequelae and sensorineural hearing loss. Newborn diagnoses leading to ECMO treatment in this study included respiratory distress syndrome secondary to persistent fetal circulation, congenital diaphragmatic hernia, meconium aspiration, respiratory syncytial virus, blood aspiration, and persistent pulmonary hypertension of the newborn (Table 1) . The purpose of this study was to examine the occurrence and time of onset of sensorineural 'Texas Tech University Medical Center, Hearing & Speech Care Center, Lubbock, Texas ; tHendrick Medical Center, Hearing Health Center, Abilene, Texas Reprint requests : Toni Mann, Texas Tech University Medical Center, Hearing & Speech Care Center, 3502 9th Street, Suite 410, Lubbock, TX 79415 hearing loss in ECMO survivors . Of 123 ECMO survivors born between 1987 and 1996 and treated at Texas Tech University Medical Center (TTUMC), 30 survivors were identified with sensorineural hearing loss (Table 2) . Eight subjects with birth dates in 1988 and 1989 were studied retrospectively, while all others were prospectively investigated . Previous research investigations have yielded a highly variable prevalence of hearing loss (4-75%) in ECMO survivors, possibly due to the limited number of hearing-impaired subjects identified (Table 3) . SUBJECTS AND METHODS T he TTUMC infant hearing assessment protocol required audiologic screening of ECMO infants prior to discharge from the neonatal Table 1 Primary Associated Diagnoses for Subjects in this Study Diagnoses Respiratory distress syndrome secondary to persistent fetal circulation Congenital diaphragmatic hernia (left or right) Meconium aspiration Respiratory syncytial virus pneumonia Persistent pulmonary hypertension of the newborn Blood aspiration Number 8 367 Journal of the American Academy of Audiology/Volume 9, Number 5, October 1998 Table 2 Degree and Prevalence of Sensorineural Hearing Losses in Study Subjects Degree Table 4 Prevalence Unilateral mild Bilateral mild Bilateral moderate Bilateral severe Bilateral profound 1 1 12 7 9 esearch Team Year Reported Number of HearingHearing Impaired Loss Subjects of Cheung et al (1996) Hofkosh et al (1991) Kawashiro et al (1996) 1996 1991 1996 14 .3 21 75 9 7 6 Schumacher et al (1991) 1995 4 4 Robertson et al (1995) 368 1995 8 3 1-Minute Apgars/ 5-Minute Apgars Total Time on ECMO in Hours ex 1 2 3 M F F 3 .4 2 .5 2 .1 7/7 0/0 6/6 93 154 73 5 M 3 .7 5/6 199 6 Table 3 Previous Reports of Sensorineural Hearing Loss Subsequent to ECMO Birth Weight in Kg When on ECMO ubjects 4 intensive care unit (NICU) using automated auditory brainstem response (ABR) techniques . The screenings were conducted on the day of discharge or within the week prior to discharge. Infants born in 1987 and 1988 did not receive a screening in the NICU because their births predated the infant screening program. Not all infants born in 1989 or later were screened. Following a long distance transfer for ECMO treatment, several patients were transported to the home hospital prior to the level of health stabilization required for ABR screening. Following normal screenings, parents were advised to schedule serial audiologic assessments to rule out subsequent hearing loss . Follow-up testing included otoscopy and combinations of the following techniques dependent upon age appropriateness : ABR, visual reinforcement audiometry, play audiometry, traditional earphone techniques, tympanometry, and otoacoustic emissions . Medical record reviews were conducted in order to confirm or complete case history reports and confirm initial audiologic screening results. Eighteen of the patients studied were male while the remaining 12 were female . Twenty-eight of the 30 hearing-impaired children had gestational ages between 32 and 43 weeks when placed on ECMO immediately after delivery, while two were placed on ECMO at the chronological ages of 3 months Relevant Subject Data 7 8 9 10 11 12 13 14 15 M M 18 19 20 21 22 F M F M F 24 25 26 27 28 29 30 3 .0 3 .3 4 .0 NA 3 .0 3 .7 2 .8 3 .1 F M 23 3.7 M M F M F M F F 16 17 3.2 4.4 3 .1 M 3 .5 M 4/6 1/2 8/9 1/3 NA 2/3 6/8 1/4 8/8 1/5 8/9 1/4 150 182 105 125 92 653 123 138 141 119 115 96 110 NA 3 .4 4 .1 2 .3 3 .2 NA 6/8 4/6 5/7 9/10 397 131 130 118 100 2 .6 3 .7 1 .8 3 .3 3 .7 3 .8 3 .6 4/6 5/7 2/5 2/5 6/8 5/8 5/7 106 69 111 292 51 97 104 2 .8 F M M F M M M 3/6 5/7 76 NA -- not applicable . and 13 months . Birth weights ranged from 1 .81 kg to 4.4 kg . For the newborn patients, 1 minute Apgar scores ranged from 0 to 9, while 5-minute Apgar scores ranged from 0 to 10. The ECMO run time was 51 to 292 hours for all subjects with one exception, who remained on ECMO for 653 hours (Table 4) . Mean ECMO run time for the 30 hearing-impaired subjects was 148 .3 hours . Family history of hearing loss was ruled out for 29 patients . Subject number 6 did have a family history of congenital hearing loss . Patients with conductive hearing losses were referred to otolaryngology for treatment. RESULTS T en subjects had a normal ABR screening prior to discharge from the NICU and were subsequently identified with a hearing loss . Of the 30 cases with confirmed sensorineural hearing losses, 20 did not receive an automated ABR Sensorineural Hearing Loss in ECMO Survivors/Mann and Adams screening prior to discharge from the NICU . Late-onset hearing loss could not be ruled out for the 20 unscreened patients . The typical configuration of hearing loss was precipitously sloping in the high frequencies. Degree of hearing loss ranged from mild to profound and amplification was required for all 30 patients . A bilateral hearing loss was recorded for 29 subjects ; the remaining one subject presented a right unilateral loss . Exact onset of hearing loss could not be ascertained but was noted to be as late as 30 months after ECMO treatment in some cases. ECMO survivors show a high prevalence of hearing loss, 24 percent in this study. DISCUSSION he high prevalence of sensorineural hearT ing loss in the post-ECMO population, at least 24 percent in this study, is critically important . This is remarkably higher than the prevalence reported in the general NICU population, 2 to 10 percent (Cox et al, 1981 ; Galambos et al, 1984). A higher pervasiveness of hearing loss cannot be ruled out since many of the 123 survivors were lost to follow-up. Another primary issue is the progressive manifestation of hearing loss noted in at least 10 of the 30 subjects studied . At least one-third of the subjects were identified with late-onset hearing loss . The age of onset was noted to be 36 months for one subject, indicating the need for long-term serial testing. This subject was tested routinely every 3 months after NICU discharge and found to have completely normal results until age 36 months . It is probable that the prevalence of progressive loss is even higher and possibly 100 percent in that every hearingimpaired infant that was screened before discharge passed the initial ABR screening. Despite early detection efforts from screening in the NICU, an insidious hearing loss may go undetected if late onset is not monitored aggressively. Frequent serial testing is needed to detect hearing loss at the earliest stage of development. Significant prevalence of progressive hearing loss is a concern presented by numerous researchers when investigating hearing loss in NICU graduates surviving ECMO, persistent fetal circulation, and persistent pulmonary hypertension of the newborn (Naulty et al, 1986 ; Nield et al, 1986 ; Hendricks-Munoz and Walton, 1988 ; Walton and Hendricks-Munoz, 1991 ; Cheung and Robertson, 1994 ; Robertson et al, 1995 ; Cheung et al, 1996 ; Kawashiro et al, 1996 ; Fujikawa et al, 1997). These findings indicate that an audiologic screening prior to discharge from the NICU alone is not sufficient audiologic management . Conscientious follow-up audiologic care is required for ECMO graduates at least through the age of 3 years. Parent education is also an important issue. Parents must be informed of the risk of progressive hearing loss, symptoms of hearing loss, and symptoms of speech and language delay. The use of ECMO is decreasing as a result of the introduction of nitric oxide treatment, but many medical centers may not yet have access to this new treatment approach . Future research efforts should include audiologic findings of nitric oxide cases to delineate the source of the hearing loss as the actual underlying medical disorder or the ECMO treatment . Further longitudinal scientific investigation is needed to compare treatment variables and indicators for hearing loss between normal hearing and hearing impaired groups and to provide further description of the time course of progressive hearing loss . Acknowledgments . We are grateful to Dwayne Paschall and Jane Goldthom for their assistance with this study and to Mary Ann Rogers for her assistance in locating, contacting, and scheduling audiologic evaluations for the subjects of this study through the years. This study is dedicated to her memory. REFERENCES Cheung PY, Halauschak MM, Finer NN, Robertson CM . (1996) . 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Follow-up of infants treated with extracorporeal membrane oxygenation for newborn respiratory failure. Pediatrics 87 :451-457 . Walton JP, Hendricks-Munoz K. (1991) . Profile and stability of sensorineural hearing loss in persistent pulmonary hypertension of the newborn. JSpeech Hear Res 34 :1362-1370 .