Objective The bispectral index (BIS) is used to evaluate the depth of hypnosis and adapt accordingly concentrations of hypnotic issued to the patient. However, antihyperalgesic dose of ketamine administered in adult, tends to alter the values of the BIS in overestimating (Hans, BJA 2005). BIS augmentation has been evaluated in children for 15 minutes after administration of 0.3 mg/kg ketamine.⇓
8 children (ages between 5 and 10 years; ASA 1) were included on a prospective and observational study. After mask-induction and intubation, anesthesia was maintained with sevoflurane, O2/N2O. After stabilizing the BIS to 50, 0.3 mg/kg ketamine was administered (t0). BIS, HR and MAP were recorded every 3 min for 21 min, out of all surgical stimulation. Results were analyzed by ANOVA (Friedman) completed of post-hoc multiples comparisons (Siegel & Castellan). *p<0.05 was considered significant.
Results The BIS is changing significantly after injection of ketamine (p<0.005), with an augmentation peak 6 and 9 min after injection of ketamine (BIS = 57±7 vs 49±3, p<0.05). This BIS augmentation appears to correlate to the age (Spearman test: p<0.05). The hemodynamic parameters remained stable.
Conclusions The value of BIS in children is overestimated as a result of the injection of ketamine, with a significant effect between 6 and 9 minutes after administration.