Sevoflurane formulation water content influences degradation by Lewis acids in vaporizers. Anesth Analg. 2009;108:1796-1802. [PMID: 19448204 DOI: 10.1213/ane.0b013e3181a3d72b]

Investigation of possible aqueous phase formation during vaporization of sevoflurane

Background and Aims

Ultane^® (sevoflurane; AbbVie Inc., North Chicago, IL, USA) has a dissolved water content of approximately 0.035% weight/weight (w/w). A previous report described formation of an aqueous layer in 4 of 13 sevoflurane vaporizers used in operating rooms. We investigated the conditions under which an aqueous layer could develop during vaporization of sevoflurane-water mixtures.

Material and Methods

A temperature-controlled glass reactor was used to simulate a vaporizer. In four experiments, the vaporization of different sevoflurane-water mixtures was monitored over approximately 3-4 days. Samples were removed at regular intervals for analysis of water content. For confirmation, one experiment was replicated in a Tec 7 vaporizer.

Results

Saturation of sevoflurane with water occurred at 0.11%-0.13% w/w at an ambient temperature; at greater water concentrations a separate aqueous phase was initially present. The sevoflurane-water azeotrope contained approximately 1.2% w/w water at 25°C. When the initial water content was <1.2% w/w (0.11%-1.03% w/w), vaporization resulted in a single phase of drier sevoflurane (final water concentration 0.02%-0.08% w/w). When the starting water concentration exceeded the azeotropic concentration (5.0% w/w), vaporization increased the water content, reaching 13% w/w at 71 h. Results under the low initial water condition were similar in the Tec 7 vaporizer.

Conclusions

An increase in water concentration following vaporization of sevoflurane can only occur when the starting water content is higher than the azeotropic concentration and therefore cannot originate from the dissolved water present in the marketed product because the water concentration in Ultane^® is 34 times lower than the azeotropic concentration.

Innovate combination of sevoflurane dilution in dimethyl sulfoxide: A stability study by gas chromatography and nuclear magnetic resonance

AIM

To investigate physicochemical stability of sevoflurane in dimethyl sulfoxide using gas chromatography with a flame ionization detector and nuclear magnetic resonance (NMR).

METHODS

Undiluted sevoflurane, plus dilutions 1:2, 1:5, 1:10, 1:25, and 1:50 in dimethyl sulfoxide were prepared in a vertical laminar flow cabinet class II type B and stored at different temperatures (23 °C, 6 °C, and -10 °C) for 45 d. Sterile 1 mL polypropylene amber syringes to minimize light degradation, caps and needles were used. The presence of sevoflurane and its degradation products in the samples was determined by gas chromatography with flame ionization detector (260 °C, 40 min), and by ¹H, ¹⁹F, and proton-decoupled ¹⁹F nuclear magnetic resonance.

RESULTS

The gas chromatography analysis showed sevoflurane and dimethyl sulfoxide (DMSO) retention times were 2.7 and 13.0 min, respectively. Pure DMSO injection into the column resulted in two additional peaks at 2.1 and 2.8 min. The same sevoflurane peak at 2.7 min was observed in all the dilutions at -10 °C, 4 °C and 25 °C. The NMR spectra showed signals consistent with the sevoflurane structure in all the dilutions at -10 °C, 4 °C and 25 °C. In the ¹H spectrum, two signals corresponding to the sevoflurane molecule were observed at 5.12 and 4.16 parts per million (ppm). In the ¹⁹F-NMR spectrum, two signals were observed at chemical shift -76.77 ppm and chemical shift -157.13 ppm. In the ¹⁹F{¹H}-NMR CPD, two signals were observed at chemical shift -76.77 ppm and chemical shift -157.13 ppm. The first one showed a doublet (J^F-F = 3.1 Hz) which integrated by six fluorine nuclei from the hexafluoro-isopropyl group. The second signal was integrated by a fluorine atom and showed a septuplet (J^F-F = 3.1 Hz).

CONCLUSION

This study shows that different concentrations of sevoflurane in dimethyl sulfoxide retain their chemical composition after exposure to different temperatures for a period of 45 d.

Sevoflurane

Sevoflurane has been available for clinical practice for about 20 years. Nowadays, its pharmacodynamic and pharmacokinetic properties together with its absence of major adverse side effects on the different organ systems have made this drug accepted worldwide as a safe and reliable anesthetic agent for clinical practice in various settings.

An Open-label Comparison of a New Generic Sevoflurane Formulation With Original Sevoflurane in Patients Scheduled for Elective Surgery Under General Anesthesia

PURPOSE

To compare the stability, effectiveness, and safety profiles of a new generic sevoflurane with those of the original sevoflurane formulation in patients undergoing elective surgery.

METHODS

An accelerated 3-month storage test was performed to evaluate the compositional changes in generic sevoflurane stored in glass bottles. In addition, 182 patients were randomly allocated to receive generic (n = 89 [54 men and 35 women]; mean [SD] age, 49.9 [11.6] years) or original (n = 93 [61 men and 32 women]; mean [SD] age, 49.6 [11.1] years) sevoflurane at a gas flow of 3 L/min for approximately 3 hours. The mean minimum alveolar concentration (MAC) during sevoflurane anesthesia was evaluated, and gas samples for measuring compound A were collected from the inspiratory limb of the circuit at preset intervals. Blood samples for measuring serum inorganic fluoride were obtained at preset intervals (pharmacokinetic group: generic/original sevoflurane = 45/46). Renal biomarkers, such as N-acetyl-β-glucosaminidase, α- and π-glutathione-S-transferase, albumin, urine protein and osmolality, serum creatinine and osmolality, creatinine clearance, and blood urea nitrogen, were measured at preset intervals (renal biomarker group: generic/original sevoflurane = 44/47). Adverse reactions were monitored for 72 hours after discontinuation of sevoflurane use.

FINDINGS

Generic sevoflurane contained in glass bottles was stable for 3 months. The mean MAC was similar for generic and original sevoflurane (median [range], 0.93 [0.67-1.29] vs 0.94 [0.63-1.5] vol%). Adverse event rates were similar (90.3% vs 84.3%), as were the AUClast of inorganic fluoride (333.7 [112.7-1264.7] vs 311.9 [81.5-1266.5] hours·μmol/L) and compound A (51.8 [6.3-204.5] vs 55.3 [10.8-270.6] hours·ppm). Biomarkers associated with renal injury were not significantly different between the 2 formulations.

IMPLICATIONS

No significant difference was found in the mean MAC between generic and original sevoflurane. ClinicalTrials.gov identifier: NCT01096212.

A new perspective on metals and other contaminants in fluoridation chemicals

BACKGROUND

Fluoride additives contain metal contaminants that must be diluted to meet drinking water regulations. However, each raw additive batch supplied to water facilities does not come labeled with concentrations per contaminant. This omission distorts exposure profiles and the risks associated with accidents and routine use.

OBJECTIVES

This study provides an independent determination of the metal content of raw fluoride products.

METHODS

Metal concentrations were analyzed in three hydrofluorosilicic acid (HFS) and four sodium fluoride (NaF) samples using inductively coupled plasma-atomic emission spectrometry. Arsenic levels were confirmed using graphite furnace atomic absorption analysis.

RESULTS

Results show that metal content varies with batch, and all HFS samples contained arsenic (4·9-56·0 ppm) or arsenic in addition to lead (10·3 ppm). Two NaF samples contained barium (13·3-18·0 ppm) instead. All HFS (212-415 ppm) and NaF (3312-3630 ppm) additives contained a surprising amount of aluminum.

CONCLUSIONS

Such contaminant content creates a regulatory blind spot that jeopardizes any safe use of fluoride additives.

Inhaled anesthetics in horses

Inhaled agents represent an important and useful class of drugs for equine anesthesia. This article reviews the ether-type anesthetics in contemporary use, their uptake and elimination, their mechanisms of action, and their desirable and undesirable effects in horses.

Assessment of induction, recovery, agitation upon awakening, and consumption with the use of two brands of sevoflurane for ambulatory anesthesia

BACKGROUND AND OBJECTIVES

Due to its pharmacological characteristics, sevoflurane is the ideal anesthetic for short-duration procedures. There are two brands of sevoflurane in the Brazilian market, Sevocris® and Sevorane®, with different formulations and packaging. The objective of this study was to assess whether there are differences between the two anesthetics regarding induction, maintenance, recovery, and consumption.

METHODS

One hundred and thirty children were included, divided into two groups according to the brand used: Group 1 was assigned to sevoflurane Cristália® and Group 2 to sevoflurane Abbott®. The following parameters were assessed: heart rate, systolic and diastolic blood pressure, fraction of inspired and expired sevoflurane, BIS values, tympanic temperature, induction and recovery time, agitation upon awakening measured by the PAED scale, and anesthetic consumption by weighing the vaporizers. Anesthesia was induced with 1 MAC and increased every three breaths at 0.5 MAC, up to 3 MAC.

RESULTS

There was no difference between groups regarding the duration of the procedure, the anesthesia, and the parameters evaluated at induction. In Group 1, the number of children who required additional bolus of sevoflurane for anesthesia maintenance was higher than in Group 2 (p<0.05). The fraction of inspired and expired sevoflurane at the end of the procedure was lower in Group 1 (p<0.001). Upon awakening, BIS value was lower in Group 1 (p=0.045). Other parameters evaluated in recovery showed no difference between groups. The use of anesthesia was similar between groups.