Topographic electroencephalogram in children during mask induction of anaesthesia with sevoflurane

Clinical Sensitivity of Fractal Neurodynamics

Among the significant advances in the understanding of the organization of the neuronal networks that coordinate the body and brain, their complex nature is increasingly important, resulting from the interaction between the very large number of constituents strongly organized hierarchically and at the same time with "self-emerging." This awareness drives us to identify the measures that best quantify the "complexity" that accompanies the continuous evolutionary dynamics of the brain. In this chapter, after an introductory section (Sect. 15.1), we examine how the Higuchi fractal dimension is able to perceive physiological processes (15.2), neurological (15.3) and psychiatric (15.4) disorders, and neuromodulation effects (15.5), giving a mention of other methods of measuring neuronal electrical activity in addition to electroencephalography, such as magnetoencephalography and functional magnetic resonance. Conscious that further progress will support a deeper understanding of the temporal course of neuronal activity because of continuous interaction with the environment, we conclude confident that the fractal dimension has begun to uncover important features of the physiology of brain activity and its alterations.

Induction of anesthesia with sevoflurane in children: Curiosities and controversies

Inhalational inductions with sevoflurane (up to 8% inspired concentration) have been the standard for inducing anesthesia in children for over three decades. However, when sevoflurane was first introduced, clinicians reported isolated cases of unexpected myoclonic jerking movements during the induction in children without epilepsy. These cases raised concerns regarding the widespread use of sevoflurane particularly after reports of seizures and epileptiform electroencephalographic (EEG) discharges surfaced. The latter reports prompted recommendations to reduce the concentration of sevoflurane during induction of anesthesia. More recently, a shift away from the use of nitrous oxide has prompted some to question whether sevoflurane has a role as an induction agent in children. The preponderance of evidence supports the practice of safely inducing anesthesia with 8% sevoflurane with or without nitrous oxide in children but recommended strategies to mitigate against epileptiform discharges may be more harmful than beneficial.

Epileptiform EEG discharges during sevoflurane anesthesia in children: A meta-analysis

OBJECTIVE

To investigate the overall incidence and associated factors of epileptiform discharges in children during sevoflurane anesthesia.

METHODS

Our group systematically searched the PubMed, Cochrane library (Central) and EMBASE for the relevant trials from their inception until September 2020. The primary endpoint was the incidence of epileptiform discharges during sevoflurane induction. The secondary endpoints were the incidence of different types of epileptiform discharges, factors associated with these epileptiform events, and other adverse events such as seizure-like movements.

RESULTS

After screening of 713 records, eleven studies involving 448 participants were included into the final analysis. Meta-analysis indicated that the overall incidence of Epileptiform EEG discharges was 38.1% (95%confidence interval [CI], 19.1%-59.2%) during sevoflurane anesthesia in children. Subgroup analysis showed that the incidence of these EEG patters was lower when participants were inducted by using the low initial concentration of sevoflurane, compared with the high initial concentration sevoflurane (1.7%, 95%CI, 0.0% to 8.4% versus 47.7%, 95%CI, 25.5% to 70.3%, P < 0.05). The longer exposure (>3 min) of high concentration sevoflurane during induction showed higher rate of epileptiform discharges than a shorter exposure (≤3 min) (48.4%, 95%CI, 20.1% to 77.3% versus 5.7%, 95%CI, 0.00% to 23.5%; P < 0.05). No significant difference for the incidence of epileptiform discharges was observed in subgroup analysis of addition of nitrous oxide (69.2%, 95%CI, 34.0% to 95.7% versus 41.3%, 95%CI, 15.6% to 69.7%, P﹥0.05) and type of EEG monitoring (26.9%, 95%CI, 3.8% to 60.7% versus 53.1%, 95%CI, 25.4% to 79.8%, P﹥0.05).

CONCLUSIONS

The incidence of epileptiform EEG events in children during sevoflurane anesthesia varied from 19.1%-59.2%. The low initial concentration technique and shorter exposure time of high concentration sevoflurane may be associated with a decreased incidence of these epileptiform discharges in EEG.

SIGNIFICANCE

Epileptiform EEG discharges during sevoflurane anesthesia in children should arouse clinicians' attention. The use of low initial concentration technique and shorter exposure time of high concentration sevoflurane may be associated with a lower occurrence of these paradoxical events.

Lateralized Periodic Discharges Detected and Described via Intraoperative Neuromonitoring

This case report details lateralized periodic discharges (LPDs) detected and described via intraoperative neuromonitoring during tumor resection. Descriptions and quantifications were made according to the American Clinical Neurophysiology Society's Standardized Critical Care EEG Terminology: 2021 Version. Further, this case illustrates quantitative changes to the LPDs observed in real time as the tumor was removed.

Electroencephalographic features of discontinuous activity in anesthetized infants and children

Background

Discontinuous electroencephalographic activity in children is thought to reflect brain inactivation. Discontinuity has been observed in states of pathology, where it is predictive of adverse neurological outcome, as well as under general anesthesia. Though in preterm-infants discontinuity reflects normal brain development, less is known regarding its role in term children, particularly in the setting of general anesthesia. Here, we conduct a post-hoc exploratory analysis to investigate the spectral features of discontinuous activity in children under general anesthesia.

Methods

We previously recorded electroencephalography in children less than forty months of age under general anesthesia (n = 65). We characterized the relationship between age, anesthetic depth, and discontinuous activity, and used multitaper spectral methods to compare the power spectra of subjects with (n = 35) and without (n = 30) discontinuous activity. In the subjects with discontinuous activity, we examined the amplitude and power spectra associated with the discontinuities and analyzed how these variables varied with age.

Results

Cumulative time of discontinuity was associated with increased anesthetic depth and younger age. In particular, age-matched children with discontinuity received higher doses of propofol during induction as compared with children without discontinuity. In the tens of seconds preceding the onset of discontinuous activity, there was a decrease in high-frequency power in children four months and older that could be visually observed with spectrograms. During discontinuous activity, there were distinctive patterns of amplitude, spectral edge, and power in canonical frequency bands that varied with age. Notably, there was a decline in spectral edge in the seconds immediately following each discontinuity.

Conclusion

Discontinuous activity in children reflects a state of a younger or more deeply anesthetized brain, and characteristic features of discontinuous activity evolve with age and may reflect neurodevelopment.

Epileptiform EEG discharges and sevoflurane in children: Protocol of a systematic review and meta-analysis

BACKGROUND

Epileptiform discharges in electroencephalogram (EEG) have been frequently reported in children undergoing sevoflurane mask induction. However, the incidence, characteristics and risk factors of these epileptiform patterns during sevoflurane anesthesia in children are poorly understood. The aim of this study is to systematically review the epileptic potential of sevoflurane in children with the EEG monitoring.

METHODS

PubMed, EMBASE, Cochrane library (Central) will be systematically searched from inception to December 2018. The effect of sevoflurane on epileptic EEG patters in children will be studied. The primary outcome will be the incidence of epileptic discharges, the characteristics and risk factors of these epileptic discharges. Meta-analysis will be calculated using R software 3.5.1.

RESULTS

This study will offer new evidence of the incidence, characteristics and risk factors of EEG epileptic discharges during sevoflurane anesthesia.

CONCLUSION

The conclusion drawn from this systematic review will benefit the children with or without epilepsy undergoing sevoflurane anesthesia.

ETHICS AND DISSEMINATION

Ethics approval is unnecessary because data of individual patients will not be included and no privacy will be involved. The results of this review will be published in a peer-reviewed journal or a conference report. Amendments of the basic protocol will be documented in the comprehensive review.

PROSPERO REGISTRATION NUMBER

PROSPERO CRD 42019122008.

Toxicologic and Inhibitory Receptor Actions of the Etomidate Analog ABP-700 and Its Metabolite CPM-Acid

Editor’s Perspective

What We Already Know about This Topic

What This Article Tells Us That Is New

Background

The etomidate analog ABP-700 produces involuntary muscle movements that could be manifestations of seizures. To define the relationship (if any) between involuntary muscle movements and seizures, electroencephalographic studies were performed in Beagle dogs receiving supra-therapeutic (~10× clinical) ABP-700 doses. γ-aminobutyric acid type A (GABAA) and glycine receptor studies were undertaken to test receptor inhibition as the potential mechanism for ABP-700 seizures.

Methods

ABP-700 was administered to 14 dogs (6 mg/kg bolus followed by a 2-h infusion at 1 mg · kg-1 · min-1, 1.5 mg · kg-1 · min-1, or 2.3 mg · kg-1 · min-1). Involuntary muscle movements were documented, electroencephalograph was recorded, and plasma ABP-700 and CPM-acid concentrations were measured during and after ABP-700 administration. The concentration-dependent modulatory actions of ABP-700 and CPM-acid were defined in oocyte-expressed α1β3γ2L GABAA and α1β glycine receptors (n = 5 oocytes/concentration) using electrophysiologic techniques.

Results

ABP-700 produced both involuntary muscle movements (14 of 14 dogs) and seizures (5 of 14 dogs). However, these phenomena were temporally and electroencephalographically distinct. Mean peak plasma concentrations were (from lowest to highest dosed groups) 35 μM, 45 μM, and 102 μM (ABP-700) and 282 μM, 478 μM, and 1,110 μM (CPM-acid). ABP-700 and CPM-acid concentration–GABAA receptor response curves defined using 6 μM γ-aminobutyric acid exhibited potentiation at low and/or intermediate concentrations and inhibition at high ones. The half-maximal inhibitory concentrations of ABP-700 and CPM-acid defined using 1 mM γ-aminobutyric acid were 770 μM (95% CI, 590 to 1,010 μM) and 1,450 μM (95% CI, 1,340 to 1,560 μM), respectively. CPM-acid similarly inhibited glycine receptors activated by 1 mM glycine with a half-maximal inhibitory concentration of 1,290 μM (95% CI, 1,240 to 1,330 μM).

Conclusions

High dose ABP-700 infusions produce involuntary muscle movements and seizures in Beagle dogs via distinct mechanisms. CPM-acid inhibits both GABAA and glycine receptors at the high (~100× clinical) plasma concentrations achieved during the dog studies, providing a plausible mechanism for the seizures.

The effect of sevoflurane on electrocorticographic spike activity in pediatric patients with epilepsy

BACKGROUND

Electrocorticogram (ECoG) spike activity is enhanced under general anesthesia with 1.5 minimum alveolar concentration (MAC) sevoflurane compared with lower concentrations in adult patients with epilepsy. However, the effect of concentration of sevoflurane on ECoG in children with epilepsy is less known.

AIMS

The primary endpoint was to investigate the effects of sevoflurane on ECoG spike activity in pediatric patients undergoing epilepsy surgery. The secondary endpoint was to examine its effects on baseline ECoG including burst suppression.

METHODS

Children of age 3-18 years with medically intractable epilepsy undergoing corpus callosotomy or resection of the epileptic foci (n = 11) were enrolled. Electrodes were placed on the brain surface and ECoG was recorded under anesthesia with endtidal carbon dioxide tension at 30 mmHg and sevoflurane at 2.5%, followed by age-adjusted 1.5 MAC (3.1-3.4%) for 10 min. The number of leads with spikes, the average number of spikes per lead per minute, median frequency of ECoG, and duration of suppression of ECoG ≥ 1 s were compared between 2.5% and 1.5 MAC sevoflurane.

RESULTS

The number of leads with spikes increased [11 vs 14, P = 0.003, difference in mean (95% CI) is 3 (2-5)], and the average number of spikes increased [9 vs 14·lead^-1 ·min^-1 , P = 0.003, difference in mean (95% CI) is 5 (2-8) lead^-1 ·min^-1 ] under anesthesia with 1.5 MAC compared with 2.5% sevoflurane. Median frequency was decreased [2.8 Hz vs 2.0 Hz, P = 0.003, difference in mean (95% CI) is 0.8 (0.4-1.2) Hz], and the duration of suppression was increased [105 s vs 262 s, P < 0.001, difference in mean (95% CI) is 156 (90-223) s] with 1.5 MAC compared with 2.5% sevoflurane.

CONCLUSIONS

Sevoflurane at 1.5 MAC significantly increased the extent and the number of spikes, prolonged the duration of suppression, and decreased median frequency of ECoG compared with those at 2.5% sevoflurane.

Sevoflurane-induced isoelectric EEG and burst suppression: differential and antagonistic effect of added nitrous oxide

The objective of this study was to investigate whether nitrous oxide influenced the ED50 of sevoflurane for induction of isoelectric electroencephalogram (ED50_isoelectric ) differently from its influence on the ED50 of sevoflurane for electroencephalogram burst suppression (ED50_burst ). In a prospective, randomised, double-blind, parallel group, up-down sequential allocation study, 77 ASA physical status 1 and 2 patients received sevoflurane induction and, after tracheal intubation, were randomly allocated to receive sevoflurane with either 40% oxygen in air (control group) or 60% nitrous oxide in oxygen mixture (nitrous group). The ED50_isoelectric in the two groups was determined using Dixon's up and down method, starting at 2.5% with 0.2% step size of end-tidal sevoflurane. The electroencephalogram was considered as isoelectric when a burst suppression ratio of 100% lasted > 1 min. The subsequent concentrations of sevoflurane administered were determined by the presence or absence of isoelectric electroencephalogram in the previous patient in the same group. The ED50_isoelectric in the nitrous group 4.08 (95%CI, 3.95-4.38)% was significantly higher than that in the control group 3.68 (95%CI, 3.50-3.78)% (p < 0.0001). The values for ED50_burst were 3.05 (95%CI, 2.66-3.90)% and 3.02 (95%CI, 3.00-3.05)% in nitrous group and control group, respectively (p = 0.52). The addition of 60% nitrous oxide increases ED50_isoelectric , but not the ED50_burst of sevoflurane. Neither result indicates an additive effect of anaesthetic agents, as might be expected, and possible reasons for this are discussed.

Electroencephalographic discontinuity during sevoflurane anesthesia in infants and children

BACKGROUND

Deep anesthesia in adults may be associated with electroencephalographic (EEG) suppression and higher rates of postoperative complications. Little is known about the impact of anesthetic depth on short- or long-term outcomes in pediatrics. Brain activity monitoring may complement clinical signs of anesthetic depth. This prospective observational study aimed to assess the frequency and degree of profound EEG suppression using multichannel EEG in children during sevoflurane general anesthesia.

METHODS

Children aged 0-40 months who required general anesthesia for elective surgery were included. Continuous EEG recordings were performed starting from when anesthesia began and until recovery. Discontinuity was defined as EEG amplitude <25 uV, lasting ≥2 s, and observed in all electrodes across the scalp. Frequency, duration, and inter-event interval of discontinuity events were measured. Relationships between discontinuity events and postnatal age, endtidal sevoflurane concentration (etSEVO), and multiple clinical parameters were analyzed.

RESULTS

Discontinuity events were observed in 35/68 children, with a median duration of 10 s (95%CI: 8-12) and a median of 4 events per patient (95%CI: 2-7). Children who had discontinuity events were younger (5.5 months, 95%CI: 3.6-6.5) compared to children who did not have discontinuity events (10.2 months, 95%CI: 6.1-14); (difference between medians, 4.7 months, 95%CI: 2.3-8, P = 0.0002). Younger infants exhibited a higher number of discontinuity events, and the incidence decreased with postnatal age (r₆₈ = -0.53, P < 0.0001). The majority of discontinuity events were observed during the first 30 min of anesthesia (66.4% total events), where etSEVO was >3%. Few discontinuity events were observed during maintenance and none during emergence. Blood pressure, heart rate, tissue oxygen saturation, and endtidal CO₂ partial pressure did not change during these events.

CONCLUSIONS

Electroencephalographic monitoring may complement clinical signs in providing information about brain homeostasis during general anesthesia. The impact of discontinuity events on immediate and long-term outcomes merits further study.

Influence of the sevoflurane concentration on the occurrence of epileptiform EEG patterns

Objectives and Aim

This study was performed to analyse the effects of different sevoflurane concentrations on the incidence of epileptiform EEG activity during induction of anaesthesia in children in the clinical routine.

Background

It was suggested in the literature to use sevoflurane concentrations lower than 8% to avoid epileptiform activity during induction of anaesthesia in children.

Methods

100 children (age: 4.6±3.0 years, ASA I–III, premedication with midazolam) were anaesthetized with 8% sevoflurane for 3 min or 6% sevoflurane for 5 min in 100% O₂ via face mask followed by 4% sevoflurane until propofol and remifentanil were given for intubation. EEGs were recorded continuously and were analysed visually with regard to epileptiform EEG patterns.

Results

From start of sevoflurane until propofol/remifentanil administration, 38 patients (76%) with 8% sevoflurane had epileptiform EEG patterns compared to 26 patients (52%) with 6% (p = 0.0106). Epileptiform potentials tended to appear later in the course of the induction with 6% than with 8%. Up to an endtidal concentration of 6% sevoflurane, the number of children with epileptiform potentials was similar in both groups (p = 0.3708). The cumulative number of children with epileptiform activity increased with increasing endtidal sevoflurane concentrations. The time from start of sevoflurane until loss of consciousness was similar in patients with 8% and 6% sevoflurane (42.2±17.5 s vs. 44.9 s ±14.0 s; p = 0.4073). An EEG stage of deep anaesthesia with continuous delta waves <2.0 Hz appeared significantly earlier in the 8% than in the 6% group (64.0±22.2 s vs. 77.9±20.0 s, p = 0.0022).

Conclusion

The own analysis and data from the literature show that lower endtidal concentrations of sevoflurane and shorter administration times can be used to reduce epileptiform activity during induction of sevoflurane anaesthesia in children.

Minimal alveolar concentration of sevoflurane for induction of isoelectric electroencephalogram in middle-aged adults

BACKGROUND

We determined the minimal alveolar concentration (MAC) of sevoflurane inducing an isoelectric EEG in 50% of adult subjects (MACie).

METHODS

We included 31 middle-aged subjects; 30 subjects finished the study protocol and received sevoflurane at preselected concentrations according to a modified Dixon 'up-and-down' design starting at 1.7 vol% with 0.2 vol% steps size. General anaesthesia was induced and maintained with sevoflurane; tracheal intubation was facilitated with cisatracurium. After a period of 30 min before skin incision, the state of isoelectric EEG was considered as significant when a burst suppression ratio of 100% lasted for >1 min. The haemodynamic responses to skin incision and the vasopressor requirement to maintain stable haemodynamic status were also analysed according to the EEG state.

RESULTS

MACie was 3.5% (95% confidence interval, 3.4-3.7%) in middle-aged subjects. When compared with subjects not in isoelectric EEG state, subjects in isoelectric EEG state received more phenylephrine to maintain stable haemodynamics (10 of 10 compared with 7 of 20 subjects, P=0.001) and experienced less sympathetic responses to skin incision (1 of 10 compared with 11 of 20 subjects, P=0.024).

CONCLUSIONS

MACie for sevoflurane was ∼2.1 times MAC for immobilization in phenobarbital premedicated middle-aged adults. Sevoflurane-induced isoelectric EEG state is associated with significant cardiovascular depression but reduced haemodynamic responses to skin incision.

[Antiepileptic prophylaxis for elective neurosurgery]

In tumoral surgery, the risk factors for perioperative epilepsy can be roughly grouped into two categories: those related to the preoperative patient's conditions (type and location of the tumors, their impact on the surrounding brain…) and those specifically related to surgery (cerebral edema, parenchymal hematoma, surgical approach, complete or incomplete resection...). The first category is supposed to be responsible for preoperative and late postoperative epilepsy, while the second would be more related to the risk of epilepsy in the first postoperative week (or may be even in the first 48hours). It is well accepted (but not always respected) by the neuro-oncologists that there is no indication for preventive antiepileptic drugs (AED) in a patient with a brain tumor that has never presented seizure. However, every seizure crisis must be treated medically. Neurosurgical procedure (which is also a key factor for controlling epilepsy when it occurs. The AED should then be maintained as appropriate. In the absence of preoperative treatment, it has never been shown that prophylactic AED significantly decreases the incidence of postoperative seizures, early or late. Yet, the opposite has not been shown neither, and many groups use AED despite the risk of side effects and an uncertain risk-benefit ratio. Currently, postoperative epilepsy is much less frequent than it was 20 or 30years ago, and the risk of AED side effects also decreases with the latest generation of molecules (such as levetiracetam). So, AED risks and benefits tend to diminish in parallel, but their relationship is still to be assessed. In practice, a modern attitude would restrict prophylactic AED use to the higher risk patients (preoperative epilepsy, temporal astrocytoma, the extent of edema and mass effect...). A drug of last generation should be used, starting one week before surgery. The duration of the treatment should be limited to one week postoperatively in the absence of seizure.

Incidence of epileptiform EEG activity in children during mask induction of anaesthesia with brief administration of 8% sevoflurane

Background

A high incidence of epileptiform activity in the electroencephalogram (EEG) was reported in children undergoing mask induction of anaesthesia with administration of high doses of sevoflurane for 5 minutes and longer. This study was performed to investigate whether reducing the time of exposure to a high inhaled sevoflurane concentration would affect the incidence of epileptiform EEG activity. It was hypothesized that no epileptiform activity would occur, when the inhaled sevoflurane concentration would be reduced from 8% to 4% immediately after the loss of consciousness.

Methodology/Principal Findings

70 children (age 7–96 months, ASA I–II, premedication with midazolam) were anaesthetized with 8% sevoflurane in 100% oxygen via face mask. Immediately after loss of consciousness, the sevoflurane concentration was reduced to 4%. EEGs were recorded continuously and were later analyzed visually with regard to epileptiform EEG patterns. Sevoflurane at a concentration of 8% was given for 1.2±0.4 min (mean ± SD). In 14 children (20%) epileptiform EEG patterns without motor manifestations were observed (delta with spikes (DSP), rhythmic polyspikes (PSR), epileptiform discharges (PED) in 10, 10, 4 children (14%, 14%, 6%)). 38 children (54%) had slow, rhythmic delta waves with high amplitudes (DS) appearing on average before DSP.

Conclusions/Significance

The hypothesis that no epileptiform potentials would occur during induction of anaesthesia with a reduction of the inspired sevoflurane concentration from 8% to 4% directly after LOC was not proved. Even if 8% sevoflurane is administered only briefly for induction of anaesthesia, epileptiform EEG activity may be observed in children despite premedication with midazolam.

Automatic detection and analysis of the EEG sharp wave-slow wave patterns evoked by fluorinated inhalation anesthetics

OBJECTIVE

The aim of this study was to develop a method for the automatic detection of sharp wave-slow wave (SWSW) patterns evoked in EEG by volatile anesthetics and to identify the patterns' characteristics.

METHODS

The proposed method consisted in the k-NN classification with a reference set obtained using expert knowledge, the morphology of the EEG patterns and the condition for their synchronization. The decision rules were constructed and evaluated using 24h EEG records in ten patients.

RESULTS

The sensitivity, specificity and selectivity of the method were 0.88 ± 0.10, 0.81 ± 0.13 and 0.42 ± 0.16, respectively. SWSW patterns' recruitment was strictly dependent on anesthetic concentration. SWSW patterns evoked by different types of anesthetics expressed different characteristics.

CONCLUSIONS

Synchronization criterion and adequately selected morphological features of "slow wave" were sufficient to achieve the high sensitivity and specificity of the method.

SIGNIFICANCE

The monitoring of SWSW patterns is important in view of possible side effects of volatile anesthetics. The analysis of SWSW patterns' recruitment and morphology could be helpful in the diagnosis of the anesthesia effects on the CNS.

Optimum Bolus dose of Propofol for Tracheal Intubation during Sevoflurane Induction without Neuromuscular Blockade in Children

The purpose of this study was to determine the optimum bolus dose of propofol required to provide excellent conditions for tracheal intubation following inhalational induction of anaesthesia using 5% sevoflurane without neuromuscular blockade. Twenty-eight children, aged three to seven years, requiring anaesthesia for short duration surgery were recruited. Two minutes after beginning the inhalational induction with 5% sevoflurane and 60% nitrous oxide, a predetermined dose of propofol was injected over 10 seconds. Propofol dose was determined using the Dixon's up-and-down method, starting from 3 mg/kg (0.5 mg/kg as a step size). Laryngoscopy was performed 50 seconds after propofol injection. The optimum dose of propofol required for excellent intubating conditions was 1.39±0.37 mg/kg in 50% of children during inhalation induction using 5% sevoflurane and 60% nitrous oxide in the absence of neuromuscular blocking agents. From probit analysis, the 95% effective dose of propofol was 2.33 mg/kg (95% confidence interval 1.78 to 6.21 mg/kg).

Optimum Bolus Dose of Propofol for Tracheal Intubation during Sevoflurane Induction without Neuromuscular Blockade in Children

The purpose of this study was to determine the optimum bolus dose of propofol required to provide excellent conditions for tracheal intubation following inhalational induction of anaesthesia using 5% sevoflurane without neuromuscular blockade. Twenty-eight children, aged three to seven years, requiring anaesthesia for short duration surgery were recruited. Two minutes after beginning the inhalational induction with 5% sevoflurane and 60% nitrous oxide, a predetermined dose of propofol was injected over 10 seconds. Propofol dose was determined using the Dixon's up-and-down method, starting from 3 mg/kg (0.5 mg/kg as a step size). Laryngoscopy was performed 50 seconds after propofol injection. The optimum dose of propofol required for excellent intubating conditions was 1.39±0.37 mg/kg in 50% of children during inhalation induction using 5% sevoflurane and 60% nitrous oxide in the absence of neuromuscular blocking agents. From probit analysis, the 95% effective dose of propofol was 2.33 mg/kg (95% confidence interval 1.78 to 6.21 mg/kg).