The relationship between bispectral index and propofol during target-controlled infusion anesthesia: a comparative study between children and young adults.

BACKGROUND: In this prospective study, we compared the relationship between propofol concentrations and bispectral index (BIS) in children versus young adults anesthetized with target-controlled infusion (TCI) of propofol. METHODS: Forty-five prepubertal subjects (children) and 45 postpubertal subjects (adults) were studied. All patients were anesthetized with TCI of propofol, based on the Kataria et al.'s model for children and on the Schnider et al.'s model for adults. All data from the BIS and the TCI system were continuously recorded using Rugloop software. Remifentanil was continuously administered throughout the study (0.25 microg x kg(-1) x min(-1)). In all patients, after the end of surgery, a 12-min period with a stable target plasma concentration (Ct) of propofol, randomly assigned at 2, 3, 4, 5, and 6 microg/mL, was performed. In addition, in most of the patients, another 12-min period was performed during which the BIS was targeted at 50 +/- 5. After each 12-min steady-state period, the Ct and BIS were noted and the plasma concentration of propofol was measured (Cm). The Ct and Cm corresponding to half maximal effect (BIS(50)) was determined by the Hill equation, and by targeting BIS at 50. RESULTS: In children, as in adults, BIS values were highly correlated with the corresponding Ct or Cm of propofol following classical E(max) dose-response curves. The ECt(50) and the ECm(50), derived from the dose-response curves, were higher in children than in adults: ECm(50): 4.0 (3.6-4.5) microg/mL vs 3.3 (3.0-3.7) microg/mL [mean (95% CI)], P < 0.001; as well were the Ct and Cm clinically obtained when BIS was targeted at 50 (Cm(50): 4.3 +/- 1.1 microg/mL vs 3.4 +/- 1.2 microg/mL, (mean +/- SD) P < 0.05, children versus adults). Cm was generally under-estimated by the Ct, and the bias was higher in children than in adults: 2.6 +/- 2.6 microg/mL vs 1.7 +/- 1.6 microg/mL (P = 0.05). CONCLUSIONS: The good relationship between propofol and BIS demonstrated in children as in adults suggested a slightly lower sensitivity to propofol in children. As the predictability of plasma propofol concentrations with the classical pharmacokinetic/pharmacodynamic models is limited in children, a cerebral pharmacodynamic feedback, such as BIS, may be useful in this population.

Sevoflurane and epileptiform EEG changes.

Sevoflurane has become the volatile agent of choice for inhalation induction of anesthesia. Hemodynamic stability and lack of respiratory irritation have justified its rapid extension to pediatric inhalation induction. The epileptogenic potential of sevoflurane has been suspected since the first case reports of abnormal movements in children without a history of epilepsy. The objectives of this short review are to: (i) analyze clinical and electroencephalographic (EEG) features supporting epileptogenic activity of sevoflurane, (ii) identify factors which may modulate that activity, and (iii) suggest guidelines of clinical practice to limit expression of this epileptiform phenomenon, which has thus far unknown morbidity. The use of sevoflurane may be associated with cortical epileptiform EEG signs, usually without clinical manifestation. No lasting neurological or EEG sequelae have been described thus far, and the potential morbidity of this epileptogenic effect is unknown. The use of sevoflurane in children, with its remarkable cardiovascular profile, should include a number of precautions. Among them, the limitation of the depth of anesthesia is essential. The wide use of cerebral function monitoring (the most simple being the EEG), may permit optimization of sevoflurane dose and avoidance of burst suppression and major epileptiform signs in fragile subjects, notably the very young and the very old.

Inhalational anesthetics in pediatric anesthesia.

PURPOSE OF REVIEW: The purpose of this review is to discuss interesting recent developments concerning the use of halogenated agents. Now we are in a new stage of halogen use; we have become alerted to the secondary effects which although not life-threatening are potentially deleterious. RECENT FINDINGS: The recent literature highlighted some unexpected effects with the use of new halogens such as emergence agitation associated with rapid elimination of new anesthetics, or epileptogenic effect of sevoflurane. In addition, recent advances in monitoring of depth of anesthesia may contribute to a more-precise dosing of halogens and concomitant decrease of the deleterious side effects. SUMMARY: Based on this new approach, the therapeutic range of the new halogenated agents may be revisited and possibly narrowed.