RESUMEN
BACKGROUND: The aim of this study was to determine whether, after propofol, rocuronium and remifentanil rapid sequence induction, inhaled anaesthetic agents should be started before intubation to minimize autonomic and arousal response during intubation. METHODS: One hundred ASA I and II patients were randomized to receive 1 MAC of desflurane or sevoflurane during manual ventilation or not. Anaesthesia was induced with an effect-site-controlled infusion of remifentanil at 2 ng ml(-1) for 3 min. Patients then received propofol to induce loss of consciousness (LOC). Rocuronium (0.6 mg kg(-1)) was given at LOC and the trachea was intubated after 90 s of manual breathing support (=baseline) with or without inhaled anaesthetics. Vital signs and bispectral index (BIS) were recorded until 10 min post-intubation to detect autonomic and arousal response. RESULTS: A significant increase in BIS value after intubation was seen in all groups. The increases were mild, even in those not receiving pre-intubation inhaled anaesthetics. However, in contrast to sevoflurane, desflurane appeared to partially blunt the arousal response. Heart rate, systolic and diastolic pressure increase similarly in all groups. CONCLUSIONS: Desflurane and sevoflurane were unable to blunt the arousal reflex completely, as measured by BIS, although the reflex was significantly less when desflurane was used. Rapid sequence induction with remifentanil, propofol and rocuronium and without inhaled anaesthetics before intubation can be done without dangerous haemodynamic and arousal responses at intubation after 90 s.
Asunto(s)
Anestésicos por Inhalación , Anestésicos Intravenosos , Nivel de Alerta/efectos de los fármacos , Intubación Intratraqueal/métodos , Adulto , Androstanoles , Anestésicos Combinados , Presión Sanguínea/efectos de los fármacos , Electroencefalografía/efectos de los fármacos , Frecuencia Cardíaca/efectos de los fármacos , Humanos , Laringoscopía , Persona de Mediana Edad , Piperidinas , Propofol , Remifentanilo , RocuronioRESUMEN
Carbon monoxide can be formed when volatile anaesthetic agents such as desflurane and sevoflurane are used with anaesthetic breathing systems containing carbon dioxide absorbents. This review describes the possible chemical processes involved and summarises the experimental and clinical evidence for the generation of carbon monoxide. We emphasise the different conditions that were used in the experimental work, and explain some of the features of the clinical reports. Finally, we provide guidelines for the prevention and detection of this complication.
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Anestésicos por Inhalación/química , Monóxido de Carbono/química , Absorción , Adolescente , Anestesia por Circuito Cerrado , Animales , Compuestos de Calcio/química , Preescolar , Desflurano , Femenino , Depuradores de Gas , Humanos , Isoflurano/análogos & derivados , Isoflurano/química , Masculino , Éteres Metílicos/química , Persona de Mediana Edad , Óxidos/química , Sevoflurano , Hidróxido de Sodio/química , PorcinosRESUMEN
Two new generation carbon dioxide absorbents, DrägerSorb Free and Amsorb Plus, were studied in vitro for formation of compound A or carbon monoxide, during minimal gas flow (500 ml x min(-1)) with sevoflurane or desflurane. Compound A was assessed by gas chromatography/mass spectrometry and carbon monoxide with continuous infrared spectrometry. Fresh and dehydrated absorbents were studied. Mean (SD) time till exhaustion (inspiratory carbon dioxide concentration >or= 1 kPa) with fresh absorbents was longer with DrägerSorb Free (1233 (55) min) than with Amsorb Plus (1025 (55) min; p < 0.01). For both absorbents, values of compound A were < 1 ppm and therefore below clinically significant levels, but were up to 0.25 ppm higher with DrägerSorb Free than with Amsorb Plus. Using dehydrated absorbents, values of compound A were about 50% lower than with fresh absorbents and were identical for DrägerSorb Free and Amsorb Plus. With dehydrated absorbents, no detectable carbon monoxide was found with desflurane.
Asunto(s)
Anestesia por Circuito Cerrado/métodos , Dióxido de Carbono/química , Monóxido de Carbono/química , Éteres/química , Hidrocarburos Fluorados/química , Isoflurano/análogos & derivados , Absorción , Anestésicos por Inhalación/química , Cloruro de Calcio , Hidróxido de Calcio , Desflurano , Humanos , Isoflurano/química , Éteres Metílicos/química , Sevoflurano , TemperaturaRESUMEN
BACKGROUND: 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 < 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 < 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.
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Anestésicos por Inhalación/metabolismo , Dióxido de Carbono/metabolismo , Éteres/metabolismo , Hidrocarburos Fluorados/metabolismo , Éteres Metílicos/metabolismo , Absorción , Humanos , Hidróxidos , Compuestos de Potasio , Sevoflurano , Hidróxido de Sodio , TemperaturaRESUMEN
BACKGROUND: 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.
Asunto(s)
Anestesia por Circuito Cerrado/instrumentación , Anestésicos Intravenosos/administración & dosificación , Electroencefalografía/efectos de los fármacos , Propofol/administración & dosificación , Adolescente , Adulto , Algoritmos , Presión Sanguínea/efectos de los fármacos , Femenino , Procedimientos Quirúrgicos Ginecológicos , Hemodinámica/efectos de los fármacos , Humanos , Laparotomía , Microcomputadores , Persona de Mediana Edad , Modelos BiológicosRESUMEN
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 CO(2) 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 microL/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 microL/L, and the limit of quantification was 0.3 microL/L. Analytical recoveries were 100.6% +/- 10.1%, 102.5% +/- 7.3%, and 99.0% +/- 4.1% at 0.5, 10, and 75 microL/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.
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Anestésicos por Inhalación/química , Éteres/análisis , Hidrocarburos Fluorados/análisis , Éteres Metílicos/química , Aire/análisis , Cromatografía de Gases y Espectrometría de Masas , Éteres Metílicos/toxicidad , Reproducibilidad de los Resultados , Sensibilidad y Especificidad , Sevoflurano , VolatilizaciónRESUMEN
BACKGROUND: 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 < 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 < 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 < 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.
Asunto(s)
Anestesia por Circuito Cerrado , Anestésicos por Inhalación/farmacocinética , Éteres/farmacocinética , Hidrocarburos Fluorados/farmacocinética , Éteres Metílicos/farmacocinética , Anestesia por Circuito Cerrado/instrumentación , Anestesia por Circuito Cerrado/métodos , Anestésicos por Inhalación/administración & dosificación , Dióxido de Carbono/metabolismo , Computadores , Estabilidad de Medicamentos , Éteres/administración & dosificación , Humanos , Hidrocarburos Fluorados/administración & dosificación , Éteres Metílicos/administración & dosificación , Modelos Biológicos , Presión Parcial , Respiración con Presión Positiva , Sevoflurano , Ventiladores MecánicosRESUMEN
BACKGROUND: 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.
Asunto(s)
Anestésicos Intravenosos/administración & dosificación , Anestésicos Intravenosos/sangre , Propofol/administración & dosificación , Propofol/sangre , Adolescente , Adulto , Algoritmos , Anestésicos Intravenosos/farmacocinética , Presión Sanguínea/efectos de los fármacos , Estado de Conciencia/efectos de los fármacos , Femenino , Humanos , Infusiones Intravenosas , Persona de Mediana Edad , Modelos Biológicos , Premedicación , Propofol/farmacocinética , Mecánica Respiratoria/efectos de los fármacos , Factores de TiempoRESUMEN
When using the closed-circuit PhysioFlex apparatus for ventilating patients with an O2/air mixture during total intravenous anesthesia (TIVA) for gynecologic laparoscopy, we noticed that the built-in infrared analyzer indicated unexpected values for halothane. In 10 ASA grade I or II patients, the breathing gases were analyzed at the end of the ventilation for the presence of methane, which could be traced in all patients. Mean concentration was 861 ppm after a mean closed-circuit anesthesia time lasting 78 min. The unexpected halothane concentration at the time of gas sampling indicated an average of 1.0%. The anesthetic vapor analysis by infrared absorption is clearly disturbed by the presence of methane.