Background: The frequency and morbidity of bradycardia during anesthes
ia in infants are not well documented. This study sought to determine
the frequency of bradycardia during anesthesia in infants (0 to 1 yr)
compared to that in older children, describe causes and morbidity, and
identify factors that influence its frequency. Methods: Computerized
information abstracted from 7,979 anesthetic records of patients ages
0-4 yr undergoing noncardiac surgery were examined for the presence or
absence of intraoperative bradycardia. To study bradycardia in infant
s, 4,645 anesthetics in patients aged 0-1 yr were considered. Those wi
th bradycardia to heart rates less than 100 beats/min were examined fo
r causes, morbidity, and treatment of the bradycardia. For analysis of
influencing factors, the frequency of bradycardia in infants was rela
ted to age, sex, race, ASA physical status, surgical site (body cavity
), complexity (major or minor) and duration, type of primary anestheti
st, type of supervising anesthesiologist, and anesthetic agents. Logis
tic regression was used to estimate the significance (P<0.05) and odds
ratios for each. Results: The frequency of bradycardia was 1.27% in t
he Ist yr of life, but only 0.65% in the third and 0.16% in the 4th yr
, a significant difference. Causes of bradycardia in infants included
disease or surgery in 35%, the dose of inhalation agent in 35%, and hy
poxemia in 22%. Morbidity included hypotension in 30%, asystole or ven
tricular fibrillation in 10%, and death in 8%. Treatment involved epin
ephrine in 30% and chest compression in 25%. Associated factors includ
ed an ASA physical status of 3-5 (vs. 1 or 2) and longer (us. shorter)
surgery. Bradycardia was less than half as likely when the supervisin
g anesthesiologist was a member of the Pediatric Anesthesia service as
with other anesthesiologists (P<0.001). Conclusions: Bradycardia is m
ore frequent In infants undergoing anesthesia compared to older childr
en and is associated with substantial morbidity. It is more likely in
sicker infants undergoing prolonged surgery and less likely when a ped
iatric anesthesiologist is present.