Nitrous oxide and formiminoglutamic acid: excretion in surgical patients and anaesthetists

Quantification of urinary zwitterionic organic acids using weak-anion exchange chromatography with tandem MS detection

A rapid and accurate quantitative method was developed and validated for the analysis of four urinary organic acids with nitrogen containing functional groups, formiminoglutamic acid (FIGLU), pyroglutamic acid (PYRGLU), 5-hydroxyindoleacetic acid (5-HIAA), and 2-methylhippuric acid (2-METHIP) by liquid chromatography tandem mass spectrometry (LC/MS/MS). The chromatography was developed using a weak anion-exchange amino column that provided mixed-mode retention of the analytes. The elution gradient relied on changes in mobile phase pH over a concave gradient, without the use of counter-ions or concentrated salt buffers. A simple sample preparation was used, only requiring the dilution of urine prior to instrumental analysis. The method was validated based on linearity (r2>or=0.995), accuracy (85-115%), precision (C.V.<12%), sample preparation stability (<or=5%, 72 h), and established patient ranges. The method was found to be both efficient and accurate for the analysis of urinary zwitterionic organic acids.

Health risks and occupational exposure to volatile anaesthetics - a review with a systematic approach

AIMS AND OBJECTIVES

To provide practicing nurse anaesthetists with evidence based knowledge as to whether they are at risk handling volatile anaesthetics by answering the question: What are the health risks threatening health care personnel occupationally exposed to volatile anaesthetics?

BACKGROUND

The interpretations of results from specific scientific studies vary and preliminary research results indicate that occupational exposure to volatile anaesthetics affects the health of operating room personnel.

DESIGN

Review of scientific literature with a systematic approach.

METHOD

The review included a systematic search in three major databases, a screening process of abstracts/articles followed by a quality assessment of the included studies. The screening process and the quality assessment were done independently by the six reviewers and followed specific protocols.

RESULTS

A systematic search of The Cochrane Library, MedLine and CINAHL resulted in a screening of 413 abstracts of which 31 articles were assessed for quality, all done independently by the reviewers. Finally, the reviewers agreed upon how to interpret the results of the assessed articles.

CONCLUSIONS

The 31 articles assessed covered areas such as genotoxic effects, neurobehavioural effects, immunology, and general health effects. In the scientific literature reviewed there is no evidence of occupational exposure to volatile anaesthetics either being associated with health risks or being harmless. Studies indicating a potential health risk are all investigating circumstances ignorant of modern environmental regulations and/or with no scavenging equipment.

RELEVANCE TO CLINICAL PRACTICE

Although no answer has been given, this review illuminates the methodological difficulties encountered in designing studies. The result of this review further stresses the need for scientific knowledge in this area and enhances the extensive use of scavenging equipment.

Long-term effects of nitrous oxide anaesthesia on laboratory and clinical parameters in elderly Omani patients: a randomized double-blind study

AIMS

This study examined the long-term effects of nitrous oxide anaesthesia on serum levels of cobalamin and folate, red cell folate levels and haematological parameters, and neurological status in elderly Omani patients.

METHODS

Sixty-nine consecutive patients undergoing ophthalmic surgery were randomly and double-blind assigned to nitrous oxide or propofol anaesthesia. They met the following entry criteria: age 55 years or above, no major organ failure, no clinical signs or symptoms of cobalamin or folate deficiency, mean cell volume (MCV) </= 96 fl, haematocrit (Hct) higher than 0.3 and no cobalamin and/or folate substitution therapy during the preceding months. Serum levels of cobalamin and folate, red cell folate levels, and haematological parameters were measured prior to anaesthesia and 3-5 weeks later. At that time, the patients also underwent thorough neurological examination.

RESULTS

Data of 51 patients were complete and considered for analysis. In both nitrous oxide and propofol group, the range of exposure time was comparable (+/-1 h). In the nitrous oxide group, a slight but significant decrease in haemoglobin, Hct, and red blood cell count (RBC) (P < 0.001) was observed, whereas there was a mild increase in mean cell haemoglobin (MCH) and mean cell volume (P < 0.05). In addition, there was a significant decrease in serum folate levels (P < 0.05). Hct and RBC decreased slightly in the propofol group (P < 0. 05), whereas there was a small increase in MCH. There was no difference between the two anaesthetics with regard to serum cobalamin and red cell folate levels, but there was a significant decrease in serum folate levels in the nitrous oxide group compared to those in the propofol group. Three patients with pre-existing low red cell folate levels, who were randomized to nitrous oxide anaesthesia, developed clinical symptoms of folate deficiency.

CONCLUSION

This study showed that short-term (40-80 min) nitrous oxide anaesthesia did not affect cobalamin levels but reduced serum folate levels in this elderly population. Although this reduction was clinically irrelevant, some patients with pre-existing asymptomatic folate deficiency developed nitrous oxide-induced folate deficiency.

A review of physiological and metabolic effects of essential amino acids

The authors review ten essential amino acids with regard to their metabolic, physiologic and therapeutic effects throughout the human body. Physical properties of these biologically active compounds are discussed as a foundation for their diverse roles in special nitrogen containing products, neurotransmitters, and as alternative energy sources. Both normal and abnormal amino acid metabolism are considered in the areas of digestion, elimination of metabolic products, metabolic intermediates, and defects in these systems. Recent developments in therapeutic applications are further examined for clinical utility and as an economical alternative to traditional clinical treatment modalities.

Age-dependent haematological disturbances in anaesthetic personnel chronically exposed to high occupational concentrations of halothane and nitrous oxide

Anaesthetic staff chronically exposed to high occupational concentrations of halothane and nitrous oxide were tested for numerous haematological and cellular function parameters at the peak of the working season and after 3 weeks vacation. The analysis of data was performed to compare differences in subjects younger and older than the age of 40 years, respectively when compared with normal controls. The analysis revealed a higher recovery of erythrocyte count in the blood of older staff, and stronger disturbance of leucocyte formation in younger staff. In contrast, monocytes appeared to be more stable in the younger staff as were the T and B lymphocyte counts. After stimulation with PHA, Con A and PWM mitogens, lymphocytes from the older age group incorporated a significantly higher amount of tritiated thymidine, but stimulation indices did not differ. Natural killer cell numbers appeared equally affected; natural killer cell activity was unaffected, but there was an increase in activity in the younger staff after the vacation. Serum immunoglobulin concentrations tended to be more affected in older individuals at the peak of the working season.

The effect of scavenging on nitrous oxide pollution in the delivery suite

United States standards recommend limits to occupational exposure to nitrous oxide. This can be achieved by the scavenging of waste anaesthetic gases, a routine practice in the operating suite, but less common in the delivery suite. In this study, nitrous oxide levels in the delivery room were measured, and scavenged and unscavenged levels were compared. Unacceptable levels of nitrous oxide were found in unscavenged delivery rooms, and in the majority of cases, scavenging reduced nitrous oxide pollution to within recommended limits.