Anesthesia and analgesia
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Anesthesia and analgesia · Oct 2000
Comparative StudyDefining segments and phases of a time capnogram.
The division of a time capnogram into inspiratory and expiratory segments is arbitrary and results in the inability of a time capnogram to detect rebreathing instantaneously. Demarcation of a time capnogram into inspiratory and expiratory components using gas flow signals will not only facilitate prompt detection of rebreathing, but will also allow application of standardized and physiologically appropriate nomenclature for better understanding and interpretation of time capnograms. A Novametrix((R)) CO(2)-SMO plus respiratory profile monitor (Novametrix Medical Systems, Wallingford, CT) was used to obtain a simultaneous display of CO(2) and respiratory flow waveforms on a computer screen during spontaneous and controlled ventilation using a circle system with the inspiratory valve competent (no rebreathing) and with the valve displaced (rebreathing). Because the response time of the CO(2) analyzer was similar to the response time of the flow sensor, a comparison was made between the two waveforms to determine the inspiratory segment (Phase 0) and the expiratory segment of the time capnogram and its subdivisions (Phases I, II, and III). The end of expiration almost coincides with the downslope of the CO(2) waveform in the capnograms when there is no rebreathing. However, in the presence of rebreathing, the alveolar plateau is prolonged and includes a part of inspiration (Phase 0), in addition to the expiratory alveolar plateau (Phase III). ⋯ Presently, the division of a time capnogram into inspiratory and expiratory segments is arbitrary. Demarcation of a time capnogram into various components using the gas flow signals facilitates prompt detection of the cause of abnormal capnograms that can widen the scope of future clinical applications of time capnography.
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Anesthesia and analgesia · Oct 2000
Smaller-than-expected sevoflurane concentrations using the Sevotec 5 vaporizer at low fill states and high fresh gas flows.
Smaller-than-expected concentrations of sevoflurane were delivered by Sevotec 5 vaporizers (Datex-Ohmeda, Madison, WI) at low-fill states, 8% dialed concentrations, and high fresh gas flows. Clinically, this would lead to prolonged induction times. The risk of complications from prolonged inhaled induction could be increased when using a vaporizer with these characteristics.
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On two occasions, sevoflurane distributed for clinical practice has been found to be contaminated with compounds thought to include hydrogen fluoride (HF) and silicon tetrafluoride (SiF(4)). Both compounds can produce pulmonary injury. However, injury would require fractional distillation of the compounds during the course of sevoflurane vaporization. ⋯ Nuclear magnetic resonance studies indicated that HF interaction with glass changed all HF to three other compounds, one being SiF(4) and the others being unknown. HF and SiF4 distill from sevoflurane more rapidly than sevoflurane is vaporized. Measurement of acidity after sevoflurane administration may not reveal a previous presence of such contaminants.
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Anesthesia and analgesia · Oct 2000
Comparative StudyA magnetic resonance imaging study of modifications to the infraclavicular brachial plexus block.
A previously described infraclavicular brachial plexus block may be modified by using a more lateral needle insertion point, while the patient abducts the arm 45 degrees or 90 degrees. In performing the modified block on patients abducting 45 degrees, we often had problems finding the cords of the brachial plexus. Therefore, we designed an anatomic study to describe the ability of the recommended needle direction to consistently reach the cords. ⋯ Comparing the two arm positions, target precision and risk of contacting the pleura were more favorable with the greater arm abduction. We conclude that when the arm is abducted to 90 degrees, a 65 degrees -needle angle to the skin appears optimal for contacting the cords, still with a minimal risk of penetrating the pleura. However, this needs to be confirmed by a clinical study.
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Anesthesia and analgesia · Oct 2000
A strategy to decide whether to move the last case of the day in an operating room to another empty operating room to decrease overtime labor costs.
We examined how to program an operating room (OR) information system to assist the OR manager in deciding whether to move the last case of the day in one OR to another OR that is empty to decrease overtime labor costs. We first developed a statistical strategy to predict whether moving the case would decrease overtime labor costs for first shift nurses and anesthesia providers. The strategy was based on using historical case duration data stored in a surgical services information system. Second, we estimated the incremental overtime labor costs achieved if our strategy was used for moving cases versus movement of cases by an OR manager who knew in advance exactly how long each case would last. We found that if our strategy was used to decide whether to move cases, then depending on parameter values, only 2.0 to 4.3 more min of overtime would be required per case than if the OR manager had perfect retrospective knowledge of case durations. The use of other information technologies to assist in the decision of whether to move a case, such as real-time patient tracking information systems, closed-circuit cameras, or graphical airport-style displays can, on average, reduce overtime by no more than only 2 to 4 min per case that can be moved. ⋯ The use of other information technologies to assist in the decision of whether to move a case, such as real-time patient tracking information systems, closed-circuit cameras, or graphical airport-style displays, can, on average, reduce overtime by no more than only 2 to 4 min per case that can be moved.