Enflurane (Ethrane, compound 347) in man *
Enflurane (2 chloro-1, 1,2-trifluoroethyl difluoro methyl ether) (CHFrOCFrCHFC1) is a halogenated liquid developed by Ross Terrell with the trade name Ethrane1’2. Enflurane has a pleasant, non-irritating smell, is volatile, colourless, non-flammable, stable with soda-lime, and unaffected by metals, light, moisture, heat and oxygen. It is non-explosive in anaesthetic concentrations when mixed with oxygen, air or nitrous oxide. Table 1 shows its physical and chemical characteristics. Virtue et al. 3 confirmed the anaesthetic properties of enflurane in dogs. They found that the agent was incompatible with the use of adrenaline and discovered some evidence of neuromuscular excitation under deep anaesthesia. McDowell and his colleagues4 also used enflurane on dogs. They produced some cardiac and respiratory depression and reported that it
The effects of changes in time interval of stimulation on mechanics of isolated heart muscle and its response to ethrane.
The reserve power of myocardial muscle depressed by Ethrane was determined by means of changes in time interval of stimulation in seven isolated cat papillary muscles. Ethrane (average concentration of 6.5 ± 0.1 mg/100 ml) decreaesd maximal isometric forces to 56 per cent of the control value at the “rested-state contraction” (RSC). Ethrane also decreased maximal isometric force (Fm) and rate of force development (dF/dt) at any given time interval of stimulation. Slopes of both time interval-force and time intcrval-dF/dt curves were unaffected by Ethrane. The percentage depressions in Fm and dF/dt were reduced from 44 and 37 to 25 and 21 per cent by decreasing the time interval from 240 sec to 3.2 sec. The ability of heart muscle to respond to changes in time interval of stimulation was, therefore, maintained during administration of Ethrane. Possible mechanisms of myocardial depression induced by Ethrane are discussed.
High-frequency hearing thresholds: effects of age, occupational ultrasound and noise exposure
AbstractPurpose
It has been suggested that high-frequency audiometry (HFA) could represent a useful preventive measure in exposed workers. The aim was to investigate the effects of age, ultrasound and noise on high-frequency hearing thresholds.MethodsWe tested 24 industrial ultrasound-exposed subjects, 113 industrial noise-exposed subjects and 148 non-exposed subjects. Each subject was tested with both conventional-frequency (0.125–8 kHz) and high-frequency (9–18 kHz) audiometry.ResultsThe hearing threshold at high frequency deteriorated as a function of age, especially in subjects more than 30 years old. The ultrasound-exposed subjects had significantly higher hearing thresholds than the non-exposed ones at the high frequencies, being greatest from 10 to 14 kHz. This hearing loss was already significantly evident in subjects with exposure <5 years and increased with years of exposure and advancing age. The noise exposure group had significantly higher hearing thresholds than the non-exposed group at the conventional frequencies 4 and 6 kHz and at the high frequency of 14 kHz. After stratification for age, there was a significant difference between the two groups at 9–10 and 14–15 kHz only for those under 30 years of age.ConclusionMultivariate analysis indicated that age was the primary predictor, and noise and ultrasound exposure the secondary predictors of hearing thresholds in the high-frequency range. The results suggest that HFA could be useful in the early diagnosis of noise-induced hearing loss in younger groups of workers (under 30 years of age).
