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Background and objectives: During regional anesthesia, various stimuli leading to an adrenergic response can occur. However, simulation of an epidural test dose by using intravenous administration of epinephrine (EPI) has always been compared with an intravenous saline infusion as the control. The aim of this study was to evaluate the possibility of distinguishing in children the effect on HR by an intravascular epinephrine infusion and a painful stimulus, using heart rate variability (HRV) and beat-to-beat analysis of HR. Methods: Thirty American Society of Anesthesiologists physical status P I children who required elective surgery were studied. At 1 minimum alveolar concentration (MAC) of sevoflurane, electrocardiogram was recorded continuously. Systolic blood pressure (SBP) was measured every minute. Measurements were performed after an intravenous administration of 0.5 μg/kg of epinephrine and during a small skin surgical incision (SI). Time-varying auto-regressive modeling of the interpolated RR sequences was performed for estimating power spectrum (msec 2 ). The HF bands were defined by (0.15–0.4 Hz). Results: Median (range) age and weight of all children were 3.5 (1–10) years and 16 (9–30) kg. EPI produced a lower increase in HR than did SI. SBP increased significantly more than did after SI. T-wave amplitude increased significantly after EPI but not after SI. Sixty seconds after the first change in HR, a secondary decrease (in comparison to control value) can be detected with EPI in contrast to SI. HF spectral power increased significantly after EPI administration but decreased after SI. The sensitivity, specificity, and positive and negative predictive value were respectively for ΔHR >10 beats per minuteof 56%, 26%, 43%, and 38%; for ΔSBP >15 mm Hg of 60%, 86%, 81%, and 67%; and for ΔT-wave amplitude >25% of 86%, 73%, 76%, and 84%. Using detection of the secondary decrease of HR, 60 seconds after the first change in HR, sensitivity, specificity, and positive and a negative predictive value were respectively 96%, 100%, 100%, and 96%. Conclusions: Detection of the secondary HR decrease, 60 seconds after the first change in HR, allows us to distinguish the effects of a painful stimulus from those related to the epinephrine test dose at 1 MAC of sevoflurane. This secondary HR decrease induced by epinephrine appears primarily because of a compensatory increase in parasympathetic tone.

The aim of this study was to evaluate the potential relationship between age, BIS (Aspect™) and the EEG bispectrum during anesthesia with sevoflurane. BIS and raw EEG sampled at 400 Hz were recorded at a steady state of 1 MAC sevoflurane in 100 children, and during a decrease from 2 MAC to 0.5 MAC in a sub-group of 29 children. The bispectrum of the EEG was estimated on successive epochs of 20 seconds using MATLAB© software, independently of the Aspect™ device. For analysis, the bispectrum was divided into 36 frequencies of coupling (Pi) - the MatBis. A multiple correspondence analysis (MCA) was used to establish an underlying structure of the pattern of each individual’s MatBis at the steady state of 1 MAC. Clustering of children into homogeneous groups was conducted by a hierarchical ascending classification (HAC). The level of statistical significance was set at 0.05. At the steady state of 1 MAC sevoflurane, the BIS values for all 100 children ranged from 20 to 74 (median 40). Projection of both age and BIS value recorded at 1 MAC (T10) onto the structured model of the MCA showed them to be distributed along axis F1 of this model. In contrast, projection of children’s position during the decrease in sevoflurane concentration was linked to axis F2. At 1 MAC sevoflurane, six homogeneous groups of children were obtained through the HAC. Groups 5 (30 months; range 23–49) and 6 (18 months; range 6–180) were the younger children and group 1 (97 months; range 46–162) the older. Groups 5 and 6 had the highest median values of BIS (54; range 50–59)(55; range 26–74) and the group 1 the lowest values (29; range 22–37). The EEG bispectrum, as well as the BIS (Aspect XP™) measured at 1 MAC sevoflurane appeared to be strongly related to the age of children.