Prospective Observational Study of Sympathetic Failure as a Mechanism Associated with Bradycardia During Induction of General Anesthesia in Children with Down Syndrome.

Aim: While bradycardia in children with Down syndrome (DS) during inhalation induction of anesthesia is characteristic, its mechanism is not well understood. This study investigated sympathetic failure as a potential (and modifiable) mechanism of bradycardia.

Materials and methods: Ninety-three children with DS and 102 typically developing (TD) children underwent inhalation induction of anesthesia. These children were monitored for sympathetic activity, exposed to sevoflurane anesthetic and were observed for the development of bradycardia. The primary outcome was sympathetic failure in the context of normoxic bradycardia within the first 300 seconds of induction. Secondary outcome measures included hypotension and parasympathetic excess.

Results: During the first 300 seconds of induction, 54 DS children became bradycardic (54/93, 58%) while 22 TD children became bradycardic (22/102, 22%). In the DS group, 23 experienced hypotension (23/80, 29%). Of those who experienced hypotension, 15 also experienced sympathetic failure (15/28, 54%).

Conclusion: More than half of children with DS undergoing inhalation anesthesia induction with sevoflurane experienced bradycardia. Bradycardia and hypotension were associated with sympathetic failure. Sympathetic activity therefore appears to be a modifiable target in the prevention of bradycardia in children with DS.