Sister chromatid exchanges in cigarette smokers: effects of halothane, isoflurane or subarachnoid blockade

Occupational exposure to volatile anaesthetics: epidemiology and approaches to reducing the problem

Long term occupational exposure to trace concentrations of volatile anaesthetics is thought to have adverse effects on the health of exposed personnel. In contrast with halothane--an agent likely to cause mutagenic effects and proven to be teratogenic--isoflurane and enflurane have not so far been proved to have adverse effects on the health of personnel exposed long term. Data on the newer agents sevoflurane and desflurane are limited. Since possible health hazards from long term exposure to inhalational anaesthetics cannot yet be definitively excluded, many Western countries have established limits for exposure. These usually range from 2 to 10 ppm as a time-weighted average over the time of exposure. A number of investigations have demonstrated that, in operating theatres with modern climate control and waste anaesthetic gas scavenging systems, occupational exposure is unlikely to exceed threshold limits. However, occupational exposure from the use of volatile agents in operating theatres with poor air control--especially during bronchoscopy procedures in paediatric patients--remains a source of concern. This also holds true for both postanaesthesia care units (PACU) and intensive care units (ICU) lacking proper air conditioning and waste gas scavengers. To minimise occupational exposure to volatile anaesthetics, all measures must be taken to provide climate control and properly working scavenging devices, and ensure sufficient personal skill of the anaesthetist, e.g. during inhalational mask induction. Furthermore, low-flow anaesthesia should be used whenever possible. The sole use of intravenous drugs such as propofol instead of volatile agents, were this possible, would eliminate occupational exposure, but may result in environmental pollution by toxic metabolites (e.g. phenol).

Comparison of genotoxicity of sevoflurane and isoflurane in human lymphocytes studied in vivo using the comet assay

In the present paper, we report data on the possible genotoxic properties of two inhalation anaesthetics--sevoflurane (SVF) and isoflurane (ISF) - in peripheral blood lymphocytes of patients before, during and after anaesthesia as compared to an unexposed control group. Both anaesthetics were evaluated for genotoxic activity using the comet assay. The exposed groups consisted of 24 ASA grades 1-2 unpremedicated patients (aged 20-66 years, anaesthetized 115-162 min for elective lower abdominal surgery), while the control group consisted of 12 healthy individuals. After induction of anaesthesia (thiopenthone sodium 5-7 mg/kg, fentanyl citrate 0.1mg and vecuronium bromide 0.1mg/kg), anaesthesia was maintained with inhalation of SVF 1-1.5% (n=12) or ISF 1-1.5% (n=12) in oxygen-air mixture. Venous blood samples were obtained before the induction of anaesthesia, at 60 and 120 min of anaesthesia and on the first, third and fifth days following anaesthesia. The comet assay detects DNA damage which includes strand breaks and alkaline labile sites induced directly by genotoxic agents as well as DNA degradation due to cell death. One hundred cells from each sample were examined and graded as no tailed, short and long tailed nuclei. The mean comet response was not different between controls and patients before anaesthesia. However, similar significant increases were observed in the mean comet response in blood sampled from patients at 60 (36.5+/-11.2, 37.8+/-12.1), or 120 min (53.1+/-17.1, 50.0+/-12.2) of anaesthesia and on the first day (37.8+/-15.1, 35.2+/-15.7) after anaesthesia in SVF and ISF treated groups, respectively. Removal of the DNA damage was observed after the third day of anaesthesia and the repair was completed within 5 days. The DNA damage detected in lymphocytes of patients during anaesthesia with SVF or ISF showed similar results as demonstrated by an increased mean comet migration at 120 min of anaesthesia and the cells were able to repair the induced DNA damage completely on the fifth postoperative day.

No genotoxic effect of propofol in chinese hamster ovary cells: analysis by sister chromatid exchanges

BACKGROUND

In spite of its high placental transfer, propofol is frequently used in general anesthesia and sedation during obstetric and gynecological surgery such as in vitro fertilization. This study investigated whether or not propofol has a genotoxic potential by the sister chromatid exchange assay in vitro.

METHODS

Sister chromatid exchanges induced after exposure to propofol were measured in Chinese hamster ovary cells with and without metabolic activation. After propofol (0.2-20 microg ml(-1)) diluted dimethyl sulfoxide was applied for 2 h with or without S9 mix, the cells having been incubated for two metaphases (34 h) in the presence of 5'-bromo-2-deoxyuridine. N-nitrosodimethylamine and mitomycin C were used as positive controls with and without metabolic activation. The chromosomes were stained with the fluorescence plus Giemsa method, and then sister chromatid exchanges in 50 cells were counted for each concentration.

RESULTS

Although increasing concentrations of propofol inhibited cell proliferation, no concentrations of propofol used in this study increased the sister chromatid exchange values, with and without metabolic activation.

CONCLUSION

It was concluded that there was no indication, from the sister chromatid exchange assay in mammalian cells, of a genotoxic effect of propofol and its metabolites.

DNA damage evaluated by the alkaline comet assay in lymphocytes of humans anaesthetized with isoflurane

In the present paper, we report data on the possible DNA damage, induced in vivo by isoflurane using the alkaline single cell gel electrophoresis technique (SCGE-comet assay) in patients before/after anaesthesia and in control group. Twelve patients, aged 22-66 years old, were anaesthetized for elective abdominal surgery with isoflurane in oxygen for 120-162 min (mean: 133.2 min). Venous blood samples were obtained from the patients before the induction of anaesthesia, at 60 and 120 min of anaesthesia and on the first, third and fifth following days of anaesthesia. SCGE was examined in 100 cells from each specimen graded as undamaged, intermediate and tailed nuclei. The number of undamaged nucleus was almost same in control and in patients before anaesthesia. However, significant differences were observed in proportion of undamaged, intermediate and tailed nucleus of patients at 60 and 120 min of anaesthesia and on the first day. DNA damage started to return to normal rates after the third day of anaesthesia and were almost identical with the rates of control group five days later.

Sister-chromatid exchanges in operating room personnel

Sister-chromatid exchange (SCE) analysis was carried out in 67 operating room personnel (anaesthetists M.D.; anaesthesia nurses and anaesthesia unit technicians) exposed to waste anaesthetic gases such as halothane, nitrous oxide and isoflurane and in 50 healthy unexposed controls. The SCE frequencies were increased significantly in operating room personnel as compared to controls. A significant increase in SCEs was found in non-smoking operating room personnel as compared to non-smoking controls. This study supports the existence of an association between occupational exposure to mutagens and an increase in SCEs in lymphocytes.

Factors that influence formation of sister chromatid exchanges in human blood lymphocytes

Sister chromatid exchange (SCE) reflects an interchange of DNA sequences between helices in a replicating chromosome. This was initially accomplished by Taylor and colleagues (1957) using tritiated thymidine incorporation followed by autoradiography. The development of an elegant technique for differential staining of sister chromatids by incorporating a thymidine analog, 5-bromodeoxyuridine (BrdU) has greatly simplified the detection of SCEs in metaphase chromosomes. In recent years, the analysis of SCE has been considered to be a highly sensitive and additional (i.e., with chromosome aberrations) end point for measuring mutagenic/carcinogenic potential of various environmental agents and is increasingly being used to detect and differentiate among chromosome fragility human diseases that predispose to neoplasia. Attention has been focused to see if the induction of SCEs in lymphocyte cultures can be used as a reliable "biological dosimeter" for genetic risk assessment and to monitor the exposed populations. Several physical or preparatory as well as biological factors that modify the response and formation of SCEs make the monitoring difficult. The purpose of this article is to review and analyze these factors to facilitate an effective development of a standard protocol for SCE testing and for appropriate evaluation of test results. This may also provide clues to understand the yet unknown molecular mechanism(s) and biological significance of SCE formation.

Genotoxic effects of ketamine on CHO cells

Ketamine, a non-barbiturate anaesthetic agent, was studied for its genotoxic potential using the SCE assay. It was genotoxic in the in vitro system at concentrations comparable to the plasma levels achieved during steady state anaesthesia. It had no effects on cellular kinetics in CHO cells.

Sister chromatid exchanges in lymphocytes of dentists and chairside assistants: no indication of a mutagenic effect of exposure to waste nitrous oxide

Cytogenetic methods are used increasingly for monitoring occupational exposure to potential mutagenic agents. By one such method, the sister chromatid exchange (SCE) test, previous studies of hospital operating room personnel did not indicate any mutagenic effect from exposure to waste anesthetic gases. Dentists and their assistants are exposed to much higher levels of nitrous oxide than hospital personnel, and in studies of dentists it is possible to eliminate bias from concomitant exposure to halogenated anesthetics by including unexposed persons engaged in the same professional activities as the exposed persons. SCE was examined in lymphocytes of venous blood from 38 female dentists and 74 chairside assistants, all working in the Child Dental Service, and 30 male dentists, of whom 23 worked in private practice. From studies of the model y = bo + b1 X age + b2 X cig./day + b3 X hours of exposure to nitrous oxide/week, by multiple linear regression, there was no indication of any influence of exposure to nitrous oxide on SCE. It was concluded that, from the SCE test, there is no indication of a mutagenic effect from exposure to waste nitrous oxide, and that possible health hazards from such exposure would be induced by other effects of nitrous oxide.