摘要:

Several studies have shown that halothane may influence drug disposition in animals and humans, but the mechanism remains unclear. The relative contributions of changes in metabolizing capacity and hepatic blood flow to altered drug disposition were investigated during halothane anesthesia, using propranolol as a model compound. The studies were performed on six dogs on three separate days; first, the day before anesthesia, second, during halothane (2.0 MAC) anesthesia, and third, 24 h after anesthesia. Each dog simultaneously received 40 mg unlabeled propranolol directly into the portal vein and 200 mCi of3H-propranolol intravenously via chronically implanted catheters. Blood samples were taken every 5 min for the first hour and then every 15 min for a further 3 h for the measurement of unlabeled and3H-propranolol concentrations. During halothane anesthesia, intra-portal–intrinsic clearance was decreased by 62% (P< 0.05) from 2,110 ± 298 to 799 ± 233 ml/min, while systemic clearance was decreased (P< 0.05) from 470 ± 33 ml/min preanesthesia to 280 ± 38 ml/min during halothane anesthesia. The intravenous elimination half-life was increased (P< 0.05) from 87 ± 12 to 155 ± 23 min during anesthesia. Although halothane anesthesia tended to lower liver plasma flow from 642 ± 80 to 473 ± 47 ml/min, this change was not significant. The large change in portal or intrinsic clearance indicates that halothane anesthesia markedly inhibits drug-metabolizing ability. The authors therefore conclude that the alterations in drug disposition observed during halothane anesthesia are mainly due to inhibition of drug-metabolizing capacity in the liver.

ISSN:0003-3022    

出版商:OVID    

年代:1985

数据来源: OVID

ISSN:0003-3022    

出版商:OVID    

年代:1985

数据来源: OVID

摘要:

An infrared analyzer for the inert tracer gas sulfur hexafluoride (SF6) is described and evaluated. The analyzer consists of a transducer and a processor unit. It is designed to operate in a nonrebreathing system with a ventilator and a computer. The transducer, which is placed over a cuvette with windows in the ventilator tubings, reads the SF6concentration in the airway during the expiratory phase. At the end of the inspiratory phase, the zero level of the instrument is automatically reset. The response time and linearity of the analyzer were tested, and interference by other gases was assessed. Full response was reached within 20 ms after a sudden introduction of 0.5% SF6into the cuvette. The analyzer–computer system had adequate linearity below 0.5% of SF6. Oxygen, nitrogen, and humid air had no influence on the analyzer signal. One hundred per cent nitrous oxide, 4% enflurane, 4% isoflurance, and 4% halothane caused signals corresponding to 0.010, 0.023, 0.022, and 0.043% SF6, respectively. Due to the method for zero reset, the importance of interference from these gases is greatly reduced when inspired and expired concentration approach each other. The disturbance from CO2(10% CO2gave a signal corresponding to 0.020% SF6) can be compensated for by including a CO2analyzer in the set-up. The rapid response and the high sensitivity of the analyzer may make it useful for studies of pulmonary gas mixing and for measurements of lung volume during mechanical ventilation.

ISSN:0003-3022    

出版商:OVID    

年代:1985

数据来源: OVID

摘要:

Measurement of functional residual capacity (FRC) by the open-circuit multiple breath tracer gas washout technique is an established method. A system based upon washout of sulfur hexafluoride (SF6) during mechanical ventilation is described. The central unit in the system is a sensitive and rapid-response infrared SF6analyzer. SF6is washed in until the alveolar concentration of SF6is 0.5%, a concentration so low that the supply of other gases is hardly influenced. During washout, the flow of SF6from the lungs is calculated by a computer every 10 ms from signals representing expiratory flow and SF6concentration. The total volume of SF6, washed out, is calculated by integration of SF6flow. Since the alveolar concentration at the end of washin is known, the lung volume may be obtained. The measurement procedure is highly automated and the result is presented by the computer immediately after washout. Accurate and reproducible results in model lung tests were obtained during air and N2O/O2ventilation. Comparison with body plethysmography (FRCBOX) in eight sitting healthy subjects gave the following: FRCN2= 7 ml + 0.98 × FRCBOX, r = 0.99. Comparison with nitrogen washout (FRCN2) in five postoperative patients gave the following: FRCSF6= 59 ml + 0.97 × FRCN2, r = 0.97. FRCSF6, during N2O/O2ventilation was the same as during air/O2ventilation in a group of paralyzed patients. The measurement system has not been tested in patients with obstructive lung disease.

ISSN:0003-3022    

出版商:OVID    

年代:1985

数据来源: OVID

ISSN:0003-3022    

出版商:OVID    

年代:1985

数据来源: OVID

ISSN:0003-3022    

出版商:OVID    

年代:1985

数据来源: OVID

ISSN:0003-3022    

出版商:OVID    

年代:1985

数据来源: OVID

ISSN:0003-3022    

出版商:OVID    

年代:1985

数据来源: OVID

ISSN:0003-3022    

出版商:OVID    

年代:1985

数据来源: OVID

ISSN:0003-3022    

出版商:OVID    

年代:1985

数据来源: OVID