Effect of remifentanil with and without atropine on heart rate variability and RR interval in children

40 children with ASA physical status I or II

Atropine 20 microg.kg(-1) injection followed 3 minutes later by remifentanil (1 microg.kg(-1) bolus over 1 min, then continual infusion at 0.25 microg.kg(-1).min(-1) for 10 min, increased to 0.5 microg.kg(-1).min(-1) for a further 10 min), after stabilization at sevoflurane 1 MAC

Ringer lactate solution followed by the same remifentanil regimen, after stabilization at sevoflurane 1 MAC

RR interval and heart rate variability (HRV) parameters including low frequency (LF), high frequency (HF), and root mean square of successive differences of RR intervals (rmssd)surrogate