International journal of clinical monitoring and computing
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Int J Clin Monit Comput · Apr 1989
EEG and SEMG monitoring during induction and maintenance of anesthesia with propofol.
Propofol has been used as IV induction (2 mg/kg) and maintenance agent (150 micrograms/kg/min and 100 micrograms/kg/min after 30 min), combined with N2O/O2 in 16 premedicated (atropine 0.5 mg, Thalamonal 2 ml IM) and mechanically ventilated patients, having ear surgery or arthroscopy. Cranial biopotentials were analysed by 2 different techniques: 1. The Anesthesia and Brain Activity Monitor (ABM Datex) providing the zero crossing frequency (ZXF) as a value for the mean frequency of the EEG signal during a considered time interval, the mean integrated voltage (MIV) as a mean value of the amplitude of the same EEG signal and the spontaneous electromyography of the frontal muscle (SEMG). 2. ⋯ A correlation was looked for between the EEG changes and the propofol blood concentrations. The higher the propofol blood concentrations, the more pronounced the low frequency bands. The appearance of beta waves or a ZXF greater than 10 Hz indicates pending arrousal.
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Int J Clin Monit Comput · Jan 1989
The use of pulse oximetry in post-operative hypoxaemia in patients after propofol induction of anaesthesia.
Pulse oximetry was used to measure changes in oxygen saturation in the early post-operative phase in three groups of 50 patients in whom anaesthesia was induced with propofol. One group breathed room air during induction and anaesthesia was maintained with halothane whereas the other two groups both breathed oxygen during induction and anaesthesia was maintained with either halothane inhalation or a propofol infusion. In 59 patients distributed fairly evenly between the three groups the oxygen saturation fell below 90%; the mean minimum oxygen saturation was 91.7 +/- 0.3 and the mean time at which it occurred was 3.9 +/- 0.4 min after the anaesthetic was withdrawn. Neither the inhalation of oxygen during induction nor the anaesthetic technique affected the decrease in postoperative oxygen saturation but the infusion group took significantly longer to recover consciousness.
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Int J Clin Monit Comput · Jan 1988
Comparative StudyAn automated method of separating patient from ventilator work on the lungs.
This paper describes a method of determining the amount of work on the lungs done by the patient and the ventilator using various modes of ventilation. The method uses a pneumotachograph to measure air flow, and measures pressure from an esophageal balloon and at the airway. The patient's work is separated from the ventilator work by analysis of the esophageal pressure. ⋯ The studies of normal subjects show that in the assist mode with increased airway resistance, significant work by the subject is required to trigger the ventilator. Two patients are presented when the assist mode resulted in excessive amounts of work and fatal outcomes. Measurement of the mechanical work required of the patient can provide useful information for the control of ventilator therapy.
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This computer program depicts the concentration-time curves for the nondepolarizing neuromuscular blocking agents. It simulates their administration by single and multiple iv injections, and with continuous infusion, alone and in combination. It provides the plasma concentrations related to 75% and 25% depression of the twitch response, using these to calculate clinically useful pharmacodynamic values, such as the duration of surgical relaxation, and the recovery index. These simulations allow the user to contrast the time-course of relaxation to be expected with various dosage regimens.
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Int J Clin Monit Comput · Jan 1988
Phase space electroencephalography (EEG): a new mode of intraoperative EEG analysis.
Intraoperative monitoring of electroencephalography (EEG) data can help assess brain integrity and/or depth of anesthesia. We demonstrate a computer generated technique which provides a visually robust display of EEG data plotted as 'phase space trajectories' and a mathematically derived parameter ('dimensionality') which may correlate with depth of anesthesia. Application of nonlinear mathematical analysis, used to describe complex dynamical systems, can characterize 'phase space' EEG patterns by identifying attractors (geometrical patterns in phase space corresponding to specific ordered EEG data subjects) and by quantifying the degree of order and chaos (calculation of dimensionality). ⋯ In this paper we describe and demonstrate phase space trajectories generated for sine waves, mixtures of sine waves, and white noise (random chaotic events). We also present EEG phase space trajectories and dimensionality calculations from a patient undergoing surgery and general anesthesia in 3 recognizable states: awake, anesthetized, and burst suppression. Phase space trajectories of the three states are visually distinguishable, and dimensionality calculations indicate that EEG progresses from 'chaos' (awake) to progressively more 'ordered' attractors (anesthetized and burst suppression).