To the Editor:—
The conclusion reached by Wilder et al.1
that exposure to multiple anesthetics is a significant risk factor in the development of learning difficulties is a headline-grabbing statement with far-reaching consequences for all providers of children's services. However, we believe there has been an insufficient attempt to draw attention to the elephant in the room: that children who require multiple operations usually have significant medical diagnoses, and/or syndromes with associated morbidities, that in turn are associated with a higher incidence of learning disorders than the general population has. Though this information on diagnoses is essential to interpret the data, it is only accessible on-line, and there is no information at all on the actual surgical procedures involved. Further analysis of the on-line data reveals that 22 of the 45 patients with multiple exposure to anesthesia have severe comorbidity or congenital anomalies that are frequently associated with learning difficulties. It should come as no surprise that children with cerebral palsy, Sturge–Weber syndrome, a history of meningitis, or cleft lip and palate have a higher incidence of learning difficulties than the general population.2
Of the remaining 23 patients, 13 have serous otitis media. Even such isolated “minor” conditions are known to be associated with an increased incidence of educational delay.3
An attempt has been made to adjust statistically for neonatal factors but not for the effect of comorbidity. Though the inability to adjust for comorbidity is referred to in the text, we believe this omission is so significant that it invalidates any conclusion from this study. We are therefore afraid that this study does not contribute sensibly to the important discussion about potential anesthetic neurotoxicity in the immature human brain.
G. Suren, Arul, F.R.C.S.
Karl-Christian Thies, D.E.A.A.*
*Birmingham Children's Hospital, Birmingham, United Kingdom. email@example.com
1. Wilder RT, Flick RP, Sprung J, Katusic SK, Barbaresi WJ, Mickelson C, Gleich SJ, Schroeder DR, Weaver AL, Warner DO: Early exposure to anesthesia and learning disabilities in a population-based birth cohort. Anesthesiology 2009; 110:796–804
2. Broder HL, Richman LC, Matheson PB: Learning disability, school achievement, and grade retention among children with cleft: A two-center study. Cleft Palate Craniofac J 1998; 35:127–31
3. Reichman J, Healey WC: Learning disabilities and conductive hearing loss involving otitis media. J Learn Disabil 1983; 16:272–8
© 2009 American Society of Anesthesiologists, Inc.