A static calibration method for the gas chromatographic determination of per cent concentrations of volatile anaesthetic agents

Halogenated Anesthetics Determination in Urine by SPME/GC/MS and Urine Levels Relationship Evaluation with Surgical Theatres Contamination

In this work, a new sensitive analytical method has been developed and evaluated for the determination of the most commonly used gaseous anesthetics, desflurane, sevoflurane, and this latter's hepatic metabolite hexafluoroisopropanol (HFIP) in the urine. In addition, an evaluation of anesthetics exposition on the urine levels of a small population of surgical operators has been performed and results are briefly discussed.

Hyperventilation accelerates rise in arterial blood concentrations of sevoflurane in gynecologic patients

PURPOSE

We investigated whether ventilation volumes affected arterial blood sevoflurane concentration (A (sev)) and its uptake into the body during general anesthesia.

METHODS

Thirty female patients undergoing elective gynecologic surgery were randomly allocated into three groups: hyperventilation, normal ventilation, and hypoventilation. Inspiratory (CI(sev)) and end-tidal ((sev)) sevoflurane concentrations were routinely measured by infrared analysis, and A (sev) were analyzed by gas chromatography for 40 min after intubation. Cardiac index and total peripheral vascular resistance were measured with a Finometer.

RESULTS

During the first 10 min after sevoflurane administration, A (sev) in the hyperventilation group was the highest and differed significantly from those in the normal ventilation group, followed by those in the hypoventilation group. In addition, hyperventilation significantly increased the slope of A (sev) over time in the first 5 min, but there were no differences in slopes in the 5-10, 10-20, and 20-40 min periods, which indicates no difference in sevoflurane bodily uptake among the three groups after 5 min.

CONCLUSION

Hyperventilation accelerated the rate of A (sev) increase immediately after sevoflurane administration, which was time dependent with respect to different alveolar ventilation levels.

Hyperventilation accelerates the rise of arterial blood concentrations of desflurane in gynecologic patients

OBJECTIVES

Under a constant inspired concentration, the uptake of a volatile anesthetic into the arterial blood should mainly be governed by alveolar ventilation, according to the assumption that the patient's cardiac output remains stable during anesthesia. We investigated whether ventilation volume affects the rate of desflurane uptake by examining arterial blood concentrations.

METHOD

Thirty female patients were randomly allocated into the following three groups: hyperventilation, normal ventilation and hypoventilation. Hemodynamic variables were measured using a Finometer, inspiratory and end-tidal concentrations of desflurane were measured by infrared analysis, and the desflurane concentration in the arterial blood (Ades) was analyzed by gas chromatography.

RESULTS

During the first 10 minutes after the administration of desflurane, the Ades was highest in the hyperventilation group, and this value was significantly different from those obtained for the normal and hypoventilation groups. In addition, hyperventilation significantly increased the slope of Ades-over-time during the first 5 minutes compared with patients experiencing normal ventilation and hypoventilation, but there were no differences in these slopes during the periods from 5-10, 10-20 and 20-40 minutes after the administration of desflurane. This finding indicates that there were no differences in desflurane uptake between the three groups after the first 5 minutes within desflurane administration.

CONCLUSIONS

Hyperventilation accelerated the rate of the rise in Ades following desflurane administration, which was time-dependent with respect to different alveolar ventilations levels.

Reliable gas chromatographic-mass spectrometric method combined with a headspace autosampler for isoflurane determination in blood

Isoflurane is a nonflammable, liquid, volatile inhalation anesthetic administered by vaporizing. Although it is now commonly used, fatal cases resulting from its abuse or misuse have been reported. A combined system of a gas chromatograph-mass spectrometer and a headspace autosampler is therefore proposed for the detection of blood isoflurane. This analytic method showed sharp and well separated peaks, and revealed a good linear relationship (r=0.9994) with a function of y = 7.3768x - 0.0222 at concentrations between 18.7 and 299.2 microg/ml. The limits of detection and quantitation of this method were 1.2 and 4.7 microg/ml, respectively. The within- and between-run precision for spiked samples, assessed by the coefficient of variations, ranged from 1.7 to 10.0% and from 4.1 to 12.8%, respectively. The within- and between-run accuracy, assessed by errors from theoretical values, were 2.2-7.8% and 2.4-9.6%, respectively. In addition, practical sample analysis showed a good applicability, with a within-run precision rate of 5.6 to 7.7% and a between-run precision rate of 5.2-10.6%. In summary, the present work presents a valid alternative for blood isoflurane analysis.

Dependence of the output of a halothane vaporizer on thymol concentration

The effect of thymol accumulation inside a Fluotec 3 vaporizer on the concentration of halothane delivered by the vaporizer was investigated. The vaporizer output was reduced progressively as the thymol concentration increased, but the reduction was less than that predicted by Raoult's Law. A reduction of 5% in output required an increase in thymol concentration of a factor of 650 compared to the concentration in fresh halothane, while a reduction of 10% required a 1100-fold increase in thymol concentration. The equilibration of the thymol from the wicks throughout the vaporizing chamber was very slow after the vaporizer was drained and filled with fresh halothane; the half-time was 2.7 days.