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  • 1
    Online Resource
    Online Resource
    In Vitro  Compound A Formation in a Computer-controlled Closed-circuit Anesthetic Apparatus
    Ovid Technologies (Wolters Kluwer Health) ; 2000
    In:  Anesthesiology Vol. 93, No. 4 ( 2000-10-01), p. 1064-1068
    Details
    In: Anesthesiology, Ovid Technologies (Wolters Kluwer Health), Vol. 93, No. 4 ( 2000-10-01), p. 1064-1068
    Abstract: Few data exist on compound A during sevoflurane anesthesia when using closed-circuit conditions and sodalime with modern computer-controlled liquid injection. Methods A PhysioFlex apparatus (Dräger, Lübeck, Germany) was connected to an artificial test lung (inflow approximately 160 ml/min carbon dioxide, outflow approximately 200 ml/min, simulating oxygen consumption). Ventilation was set to obtain an end-tidal carbon dioxide partial pressure (Petco2) approximately 40 mmHg. Canister inflow (T degrees in) and outflow (T degrees out) temperatures were measured. Fresh sodalime and charcoal were used. After baseline analysis, sevoflurane concentration was set at 2.1% end-tidal for 120 min. At baseline and at regular intervals thereafter, Petco2, end-tidal sevoflurane, T degrees in, and T degrees out were measured. For inspiratory and expiratory compound A determination, samples of 2-ml gas were taken. These data were compared with those of a classical valve-containing closed-circuit machine. Ten runs were performed in each set-up. Results Inspired compound A concentrations increased from undetectable to peak at 6.0 (SD 1.3) and 14.3 (SD 2.5) ppm (P & lt; 0.05), and maximal temperature in the upper outflow part of the absorbent canister was 24.3 degrees C (SD 3.6) and 39.8 degrees C (SD 1.2) (P & lt; 0.05) in the PhysioFlex and valve circuit machines, respectively. Differences between the two machines in compound A concentrations and absorbent canister temperature at the inflow and outflow regions were significantly different (P & lt; 0.05) at all times after 5 min. Conclusion Compound A concentrations in the high-flow (70 l/min), closed-circuit PhysioFlex machine were significantly lower than in conventional, valve-based machines during closed-circuit conditions. Lower absorbent temperatures, resulting from the high flow, appear to account for the lower compound A formation.
    Type of Medium: Online Resource
    ISSN: 0003-3022
    URL: Article
    DOI: 10.1097/00000542-200010000-00030
    RVK:
    XA 22600
    Language: English
    Publisher: Ovid Technologies (Wolters Kluwer Health)
    Publication Date: 2000
    detail.hit.zdb_id: 2016092-6
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  • 2
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    Online Resource
    Comparison of Plasma Compartment versus  Two Methods for Effect Compartment–controlled Target-controlled Infusion for Propofol
    Ovid Technologies (Wolters Kluwer Health) ; 2000
    In:  Anesthesiology Vol. 92, No. 2 ( 2000-02-01), p. 399-399
    Details
    In: Anesthesiology, Ovid Technologies (Wolters Kluwer Health), Vol. 92, No. 2 ( 2000-02-01), p. 399-399
    Abstract: Target-controlled infusion (TCI) systems can control the concentration in the plasma or at the site of drug effect. A TCI system that targets the effect site should be able to accurately predict the time course of drug effect. The authors tested this by comparing the performance of three control algorithms: plasmacontrol TCI versus two algorithms for effect-site control TCI. Methods One-hundred twenty healthy women patients received propofol via TCI for 12-min at a target concentration of 5.4 microg/ml. In all three groups, the plasma concentrations were computed using pharmacokinetics previously reported. In group I, the TCI device controlled the plasma concentration. In groups II and III, the TCI device controlled the effect-site concentration. In group II, the effect site was computed using a half-life for plasma effect-site equilibration (t1/2k(eo)) of 3.5 min. In group III, plasma effect-site equilibration rate constant (k(eo)) was computed to yield a time to peak effect of 1.6 min after bolus injection, yielding a t1/2keo of 34 s. the time course of propofol was measured using the bispectral index. Blood pressure, ventilation, and time of loss of consciousness were measured. Results The time course of propofol drug effect, as measured by the bispectral index, was best predicted in group III. Targeting the effect-site concentration shortened the time to loss of consciousness compared with the targeting plasma concentration without causing hypotension. The incidence of apnea was less in group III than in group II. Conclusion Effect compartment-controlled TCI can be safely applied in clinical practice. A biophase model combining the Marsh kinetics and a time to peak effect of 1.6 min accurately predicted the time course of propofol drug effect.
    Type of Medium: Online Resource
    ISSN: 0003-3022
    URL: Article
    DOI: 10.1097/00000542-200002000-00021
    RVK:
    XA 22600
    Language: English
    Publisher: Ovid Technologies (Wolters Kluwer Health)
    Publication Date: 2000
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  • 3
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    Online Resource
    No Compound A Formation with Superia® During Minimal-Flow Sevoflurane Anesthesia: A Comparison with Sofnolime®
    Ovid Technologies (Wolters Kluwer Health) ; 2002
    In:  Anesthesia & Analgesia Vol. 95, No. 6 ( 2002-12), p. 1680-1685
    Details
    In: Anesthesia & Analgesia, Ovid Technologies (Wolters Kluwer Health), Vol. 95, No. 6 ( 2002-12), p. 1680-1685
    Type of Medium: Online Resource
    ISSN: 0003-2999
    URL: Article
    DOI: 10.1097/00000539-200212000-00039
    RVK:
    XA 22250
    Language: English
    Publisher: Ovid Technologies (Wolters Kluwer Health)
    Publication Date: 2002
    detail.hit.zdb_id: 2018275-2
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  • 4
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    Quantitative Determination of Vapor-Phase Compound A in Sevoflurane Anesthesia Using Gas Chromatography–Mass Spectrometry
    Oxford University Press (OUP) ; 2001
    In:  Clinical Chemistry Vol. 47, No. 2 ( 2001-02-01), p. 281-291
    Details
    In: Clinical Chemistry, Oxford University Press (OUP), Vol. 47, No. 2 ( 2001-02-01), p. 281-291
    Abstract: Background: During low-flow or closed-circuit anesthesia with the fluorinated inhalation anesthetic sevoflurane, compound A, an olefinic degradation product with known nephrotoxicity in rats, is generated on contact with alkaline CO2 adsorbents. To evaluate compound A formation and thus potential sevoflurane toxicity, a reliable and reproducible assay for quantitative vapor-phase compound A determination was developed. Methods: Compound A concentrations were measured by fully automated capillary gas chromatography–mass spectrometry with cryofocusing. Calibrators of compound A in the vapor phase were prepared from liquid volumetric dilutions of stock solutions of compound A and sevoflurane in ethyl acetate. 1,1,1-Trifluoro-2-iodoethane was chosen as an internal standard. The resulting quantitative method was fully validated. Results: A linear response over a clinically useful concentration interval (0.3–75 μL/L) was obtained. Specificity, sensitivity, and accuracy conformed with current analytical requirements. The CVs were 4.1–10%, the limit of detection was 0.1 μL/L, and the limit of quantification was 0.3 μL/L. Analytical recoveries were 100.6% ± 10.1%, 102.5% ± 7.3%, and 99.0% ± 4.1% at 0.5, 10, and 75 μL/L, respectively. The method described was used to determine compound A concentrations during simulated closed-circuit conditions. Some of the resulting data are included, illustrating the practical applicability of the proposed analytical approach. Conclusions: A simple, fully automated, and reliable quantitative analytical method for determination of compound A in air was developed. A solution was established for sampling, calibration, and chromatographic separation of volatiles in an area complicated by limited availability of sample volume and low concentrations of the analyte.
    Type of Medium: Online Resource
    ISSN: 0009-9147 , 1530-8561
    URL: Article
    DOI: 10.1093/clinchem/47.2.281
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2001
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  • 5
    Online Resource
    Online Resource
    Only Carbon Dioxide Absorbents Free of Both NaOH and KOH Do Not Generate Compound A during In Vitro  Closed-system Sevoflurane
    Ovid Technologies (Wolters Kluwer Health) ; 2001
    In:  Anesthesiology Vol. 95, No. 3 ( 2001-09-01), p. 750-755
    Details
    In: Anesthesiology, Ovid Technologies (Wolters Kluwer Health), Vol. 95, No. 3 ( 2001-09-01), p. 750-755
    Abstract: Insufficient data exist on the production of compound A during closed-system sevoflurane administration with newer carbon dioxide absorbents. Methods A modified PhysioFlex apparatus (Dräger, Lübeck, Germany) was connected to an artificial test lung (inflow at the top of the bellow approximately/= 160 ml/min CO2; outflow at the Y piece of the lung model approximately/= 200 ml/min, simulating oxygen consumption). Ventilation was set to obtain an end-tidal carbon dioxide partial pressure of approximately 40 mmHg. Various fresh carbon dioxide absorbents were used: Sodasorb (n = 6), Sofnolime (n = 6), and potassium hydroxide (KOH)-free Sodasorb (n = 7), Amsorb (n = 7), and lithium hydroxide (n = 7). After baseline analysis, liquid sevoflurane was injected into the circuit by syringe pump to obtain 2.1% end-tidal concentration for 240 min. At baseline and at regular intervals thereafter, end-tidal carbon dioxide partial pressure, end-tidal sevoflurane concentration, and canister inflow (T degrees(in)) and canister outflow (T degrees(out)) temperatures were measured. To measure compound Ainsp concentration in the inspired gas of the breathing circuit, 2-ml gas samples were taken and analyzed by capillary gas chromatography plus mass spectrometry. Results The median (minimum-maximum) highest compound Ainsp concentrations over the entire period were, in decreasing order: 38.3 (28.4-44.2)* (Sofnolime), 30.1 (23.9-43.7) (KOH-free Sodasorb), 23.3 (20.0-29.2) (Sodasorb), 1.6 (1.3-2.1)* (lithium hydroxide), and 1.3 (1.1-1.8)* (Amsorb) parts per million (*P & lt; 0.01 vs. Sodasorb). After reaching their peak concentration, a decrease for Sofnolime, KOH-free Sodasorb, and Sodasorb until 240 min was found. The median (minimum-maximum) highest values for T degrees(out) were 39 (38-40), 40 (39-42), 41 (40-42), 46 (44-48)*, and 39 (38-41) degrees C (*P & lt; 0.01 vs. Sodasorb), respectively. Conclusions With KOH-free (but sodium hydroxide [NaOH]-containing) soda limes even higher compound A concentrations are recorded than with standard Sodasorb. Only by eliminating KOH as well as NaOH from the absorbent (Amsorb and lithium hydroxide) is no compound A produced.
    Type of Medium: Online Resource
    ISSN: 0003-3022
    URL: Article
    DOI: 10.1097/00000542-200109000-00030
    RVK:
    XA 22600
    Language: English
    Publisher: Ovid Technologies (Wolters Kluwer Health)
    Publication Date: 2001
    detail.hit.zdb_id: 2016092-6
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  • 6
    Online Resource
    Online Resource
    Comparison of Closed-loop Controlled Administration of Propofol Using Bispectral Index as the Controlled Variable versus  “Standard Practice” Controlled Administration
    Ovid Technologies (Wolters Kluwer Health) ; 2001
    In:  Anesthesiology Vol. 95, No. 1 ( 2001-07-01), p. 6-17
    Details
    In: Anesthesiology, Ovid Technologies (Wolters Kluwer Health), Vol. 95, No. 1 ( 2001-07-01), p. 6-17
    Abstract: This report describes a new closed-loop control system for propofol that uses the Bispectral Index (BIS) as the controlled variable in a patient-individualized, adaptive, model-based control system, and compares this system with manually controlled administration of propofol using hemodynamic and somatic changes to guide anesthesia. Methods Twenty female patients, American Society of Anesthesiologists physical status I or II, who were scheduled for gynecologic laparotomy were included to receive propofolremifentanil anesthesia. In group I, propofol was titrated using a BIS-guided, model-based, closed-loop system. The BIS target was set at 50. In group II, propofol was titrated using classical hemodynamic signs of (in)adequate anesthesia. Performance of control during induction and maintenance of anesthesia were compared between both groups using BIS as the controlled variable in group I and the reference variable in group II, and, conversely, the systolic blood pressure as the controlled variable in group II and the reference variable in group I. At the end of anesthesia, recovery profiles between groups were compared. Results Although patients undergoing manual induction of anesthesia in group II at 300 ml/h reached a BIS level of 50 faster than patients undergoing open-loop, computer-controlled induction in group I, manual induction caused a more pronounced initial overshoot of the BIS target. This resulted in a more pronounced decrease in blood pressure in group II. During the maintenance phase, better control of BIS and systolic blood pressure was found in group I compared with group II. Recovery was faster in group I. Conclusion A closed-loop system for propofol administration using the BIS as a controlled variable together with a model-based controller is clinically acceptable during general anesthesia.
    Type of Medium: Online Resource
    ISSN: 0003-3022
    URL: Article
    DOI: 10.1097/00000542-200107000-00007
    RVK:
    XA 22600
    Language: English
    Publisher: Ovid Technologies (Wolters Kluwer Health)
    Publication Date: 2001
    detail.hit.zdb_id: 2016092-6
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