Topographic electroencephalogram of propofol-induced conscious sedation.

OBJECTIVES: To determine the effects of increasing doses of propofol that induce conscious sedation on the topographic electroencephalogram (EEG) of human volunteers and to test the hypothesis that more frontal brain areas are affected by low doses of propofol. METHODS: The scalp EEG was recorded monopolarly from 16 different sites based on the 10-20 International System. Microcomputer-based hardware and RHYTHM 7.1 software were used to obtain quantitative power frequency topographic EEG data. A total of 10 normal adult volunteers were given incremental doses of propofol targeted to plasma concentrations of 0 to 1200 ng/ml. RESULTS: Sedative concentrations of propofol produced a dramatic increase in beta 1, an increase in alpha 2 and beta 2, and an increase in delta activity at the largest concentration, with almost no change in theta activity. The increase in beta 1 activity had a linear correlation with plasma propofol levels (r = 0.9). Topographic mapping indicated that beta 1 activation was primarily in the frontal and central regions, with focal changes more in the left hemisphere. CONCLUSIONS: Topographic brain EEG mapping techniques indicate that frontal brain beta 1 EEG activity may be useful as an objective brain index of propofol conscious sedation.

Depth of anaesthesia monitoring: what's available, what's validated and what's next?

Depth of anaesthesia monitors might help to individualize anaesthesia by permitting accurate drug administration against the measured state of arousal of the patient. In addition, the avoidance of awareness or excessive anaesthetic depth might result in improved patient outcomes. Various depth of anaesthesia monitors based on processed analysis of the EEG or mid-latency auditory-evoked potentials are commercially available as surrogate measures of anaesthetic drug effect. However, not all of them are validated to the same extent.

The safety and effectiveness of remifentanil as an adjunct sedative for regional anesthesia.

UNLABELLED: We assessed the sedative potential of continuous infusions of remifentanil with a validated composite alertness scale in 160 patients (ASA physical status I or II) undergoing hip replacement surgery with spinal block (n = 61) or hand surgery using brachial plexus block (n = 93). They were randomized to receive one of the following initial dose regimens in double-blinded fashion: placebo or 0.04, 0.07, or 0.1 microg x kg(-1) x min(-1) remifentanil subsequently titrated to effect. Additional midazolam IV was allowed for adequate sedation as required. The combined analysis of both surgery groups revealed a dose-related increase in achievement of sedation level > or =2 within 15 min of the start of the study drug infusion; all remifentanil dose comparisons with placebo reached significance (P < 0.001). The remifentanil 50% effective dose for a composite sedation level > or =2 within 15 min of the start of drug infusion was estimated as 0.043 microg x kg(-1) x min(-1) (95% confidence interval 0.01, 0.059). The requirement for midazolam decreased with increasing remifentanil dose compared with placebo (P < 0.001). The median time to return to alertness after the end of infusion was 10-12 min in the remifentanil groups and 5 min in the placebo group. Significant incidences of nausea, pruritus, sweating, and respiratory depression were reported during remifentanil infusions compared with placebo. The data suggest that remifentanil may be useful for supplementation of regional anesthesia, provided that ventilation is carefully monitored. IMPLICATIONS: In this dose-finding, placebo-controlled study, remifentanil infusions were used to provide sedation during spinal and brachial plexus regional anesthesia. The 50% effective dose for achievement of sedation was 0.043 microg x kg(-1) x min(-1). Return to alertness occurred after 10-12 min (median time). Remifentanil infusions can be used to supplement regional anesthesia, but this requires careful monitoring of ventilation.

Nonlinear methods for biopattern analysis: role and challenges.

An important trend in medical technology is towards support for personalised healthcare, fuelled by developments in genomic-based medicine. New computational intelligent techniques for biodata analysis will be needed to fully exploit the vast amounts of data that are being generated. Non-linear signal processing methods will form an important part of such computational intelligent techniques. This paper introduces some non-linear methods which are likely to play a role in the emerging area of biopattern and bioprofile analysis that will underpin personalized healthcare. We highlight their application to clinical problems involving EEG and fetal ECG and heart rate analysis, and issues that arise when they are applied to real world problems. The clinical problems include dementia assessment, drug administration and fetal monitoring. The potential role and challenges in the application of non-linear signal analysis of biopattern and bioprofile are highlighted within the context of a major EU project, BIOPATTERN.