In Reply:-We thank Dr. Rosen for his interesting comments about our report. Our focus was to report the incidence and timing of cerebral microemboli during cardiac surgery in children; however, it is logical to consider interventions that might reduce the number of these (presumed gaseous) emboli. Displacement of air in the operative field by carbon dioxide is certainly such a preventative measure that deserves further study. We would only caution that controlled studies of neuropsychiatric deficits after cardiac surgery in children are difficult because of multiple confounding variables, including nonhomogeneity of cardiac lesions, duration of preexisting cyanosis, use of deep hypothermic circulatory arrest, and difficulty in detecting neurologic injury in very young children.

James J. O'Brien, M.D.

Department of Anesthesiology; Wake Forest University School of Medicine; Winston-Salem, North Carolina

(Accepted for publication March 16, 1998.)