The loss of sevoflurane from a closed breathing system

When volatile anaesthetics are used in a closed breathing system it is usually assumed that inflow of anaesthetic to the system matches uptake by the patient. Early laboratory reports on the interactions between sevoflurane and soda lime cast doubt on that assumption. We have measured the loss of sevoflurane, desflurane and isoflurane from a closed breathing system and found no differences of consequences.     

Occupational exposure to sevoflurane, halothane and nitrous oxide during paediatric anaesthesia Waste gas exposure during paediatric anaesthesia

We report the findings of a study on exposure of operating room staff to sevoflurane, halothane and nitrous oxide during induction and maintenance of anaesthesia in children. Concentrations of anaesthetic agents in the operating theatre were measured directly by highly sensitive, photoacoustic infrared spectrometer during 20 anaesthetics. Samples were taken from the breathing zones of the anaesthetist and the circulating nurse. The operating theatre was of modern design with an air conditioning system providing 20 changes of air each hour. The threshold values of 100 ppm N₂O, 50 ppm isoflurane and 10 ppm halothane recommended by the United Kingdom Committee for Occupational Safety and Health (COSH) were exceeded in several cases for a short time during mask induction. After tracheal intubation, trace concentrations of sevoflurane, halothane and N₂O were mostly under the recommended levels and comparable to levels measured during adult anaesthesia.     

Minimum alveolar concentration for halothane in children with cerebral palsy and severe mental retardation

Children with cerebral palsy and severe mental retardation who present for operation may require lower concentrations of inhalational anaesthetics than healthy children. The minimum alveolar concentration (MAC) for halothane was measured in 36 children and adolescents, aged 4–18 years, who underwent orthopaedic surgery. The control group consisted of 12 healthy children (group 1). Children with cerebral palsy and severe mental retardation were allocated to one of two groups: those taking chronic anticonvulsant medication (group 2) ( n  = 12) and those who did not take any drugs (group 3) ( n  = 12). The mean (SEM) MAC value for halothane (expressed in volume per cent) was 0.90 (0.02) for healthy children. Children with cerebral palsy had significantly lower MAC values whether they took anticonvulsant drugs or not (0.62 (0.03) and 0.71 (0.10), respectively).     

Propofol and Intralipid cause creaming of serum from critically ill patients

The aim of this in-vitro study was to investigate the incidence of propofol agglutination with serum from critically ill patients. Serum (400 μl) from 58 critically ill patients and 30 healthy volunteers was incubated with 10 μl of either propofol, Intralipid 10% or Intralipid 20%. Control incubations contained serum only. At 24 h, the serum was examined macroscopically and microscopically for agglutination. Agglutination was seen with Intralipid 20% in serum from all critically ill patients and 13.3% of volunteers. Serum from 91.4% of critically ill patients was agglutinated with Intralipid 10% and only 3.3% of the healthy volunteers. In comparison, propofol produced agglutination in 74.1% of critically ill patients and in none of the serum from healthy volunteers (p < 0.05 propofol versus Intralipid 10%, p < 0.0001 propofol versus Intralipid 20%). No correlation was seen between agglutination and age, sex, APACHE II score or plasma concentration of acute phase proteins. However, agglutination of propofol and Intralipid 10% was more frequent (p < 0.001) in serum from patients with pulmonary disease, than in patients with normal lungs. The clinical implications of these in-vitro findings are unclear and need further investigation.     

Nitrous oxide in early human pregnancy

An analysis of the outcome of 375 cases (383 fetuses) of cervical cerclage and 58 other operations (59 fetuses) conducted under general anaesthesia, which included the administration of nitrous oxide, failed to reveal a single instance of which nitrous oxide could have been clearly indicted as a cause of fetal abnormality The incidence of inevitable abortion and of low birth weight babies in the series of cervical cerclage conducted under general anaesthesia was identical to that in a series conducted under regional analgesia (115 fetuses). This represents the first of a two-part test of the proposition that nitrous oxide should not be administered to women in the first or second trimester. Our interim conclusion is that the proposition is unacceptable.     

喉罩及其麻醉药物临床应用新进展

喉罩是介于气管内插管通气和面罩通气之间的声门上通气装置,和气管插管相比,喉罩具备很多独特的优点,能够安全、有效、微创、舒适地维持通气,是现代气道管理不可或缺的工具。随着喉罩的应用范围越来越广,其并发症亦已引起相应重视。本文拟对喉罩及其麻醉药物的临床应用等进行阐述。     

Comparison of computer-controlled administration of propofol with two manually controlled infusion techniques

Ninety women were studied in order to compare dose requirements and quality of anaesthesia between target-controlled infusion and two manually controlled infusion schemes for propofol administration: group I received target-controlled infusion for induction (4 μg.ml⁻¹ target blood concentration, increased by 2 μg.ml⁻¹ after 3 min if consciousness not lost), groups II and III received an induction bolus of propofol at infusion rates of 1200 or 600 ml.h⁻¹, respectively, until loss of consciousness. Anaesthesia was maintained with propofol target-controlled infusion in group I or by constant rate infusion in the other two groups. Computer simulations were used to calculate blood and effect-site propofol concentrations. Mean induction times (SD) were 78 (65) s in group I versus 51 (10) s and 62 (12) s in groups II and III, respectively (p < 0.05 between groups II and III). Mean induction doses were: 1.31 (0.44), 2.74 (0.56) and 1.77 (0.43) mg.kg⁻¹ and mean maintenance doses were 13.4 (3.55), 9.32 (1.71) and 9.97 (1.53) mg.kg⁻¹.h⁻¹ in groups I, II and III, respectively (p < 0.05 between all groups). There was a lower incidence of apnoea in group I than in groups II and III. There were no significant differences between the groups in other objective parameters of anaesthetic quality studied. Computer simulations showed an 'overshoot' in propofol blood and effect-site concentration with manual induction and significantly higher maintenance levels with target-controlled infusion.     

Halothane and trichloroethylene

The vapour pressures of static mixtures of halothane and trichloroethylene and the output of the two vapours from an Oxford Miniature Vaporizer filled with mixtures of the two liquids have been studied. In a small pilot study, a mixture of halothane and trichloroethylene was used for drawover anaesthesia in patients having minor surgery; this seems to work satisfactorily and may have some limited applications.