A qualitative investigation into the physical stability of polypropylene and polyethylene in liquid isoflurane and sevoflurane.

The interaction between medical plastics and drugs is complex. Drug absorption into plastics may affect drug dosage and the migration of plastics' additives into a drug solution may affect drug composition. We investigated the stability of those plastics which may be used in infusion systems to inject liquid volatile anaesthetic drugs directly into an anaesthetic breathing system. Samples of two types of polypropylene from a syringe barrel and plunger and low- and high-density polyethylene from extension tubing were exposed to isoflurane and sevoflurane for 1, 7 or 250 days. All samples were from the same batches. Samples of the plastics (n = 24) and the liquid volatile anaesthetics (n = 24) were subjected to Fourier transform-infrared spectroscopy to produce series of absorption spectra. By reference to control sample absorption spectra, this allows detection of anaesthetic drug absorption into the plastics or migration of the plastics or their additives into the liquid anaesthetics. We found no evidence of migration of the plastic components or their additives into the liquid anaesthetic drugs at any of the exposure periods. Similarly, we found no evidence of absorption of isoflurane or sevoflurane by any of the plastic components during short-term exposure of either 1 or 7 days. However, there was evidence of some absorption of the anaesthetic drugs by the polyethylene plastics after about 8 months' exposure. It would appear that low- and high-density polyethylene and polypropylene are suitably safe for use in infusion systems for the direct injection of isoflurane and sevoflurane into anaesthetic breathing systems.

Amsorb: a new carbon dioxide absorbent for use in anesthetic breathing systems.

BACKGROUND: This article describes a carbon dioxide absorbent for use in anesthesia. The absorbent consists of calcium hydroxide with a compatible humectant, namely, calcium chloride. The absorbent mixture does not contain sodium or potassium hydroxide but includes two setting agents (calcium sulphate and polyvinylpyrrolidine) to improve hardness and porosity. METHODS: The resultant mixture was formulated and subjected to standardized tests for hardness, porosity, and carbon dioxide absorption. Additionally, the new absorbent was exposed in vitro to sevoflurane, desflurane, isoflurane, and enflurane to determine whether these anesthetics were degraded to either compound A or carbon monoxide. The performance data and inertness of the absorbent were compared with two currently available brands of soda lime: Intersorb (Intersurgical Ltd., Berkshire, United Kingdom) and Dragersorb (Drager, Lubeck, Germany). RESULTS: The new carbon dioxide absorbent conformed to United States Pharmacopeia specifications in terms of carbon dioxide absorption, granule hardness, and porosity. When the new material was exposed to sevoflurane (2%) in oxygen at a flow rate of 1 l/min, concentrations of compound A did not increase above those found in the parent drug (1.3-3.3 ppm). In the same experiment, mean +/-SD concentrations of compound A (32.5 +/- 4.5 ppm) were observed when both traditional brands of soda lime were used. After dehydration of the traditional soda limes, immediate exposure to desflurane (60%), enflurane (2%), and isoflurane (2%) produced concentrations of carbon monoxide of 600.0 +/- 10.0 ppm, 580.0 +/- 9.8 ppm, and 620.0 +/-10.1 ppm, respectively. In contrast, concentrations of carbon monoxide were negligible (1-3 ppm) when the anhydrous new absorbent was exposed to the same anesthetics. CONCLUSIONS: The new material is an effective carbon dioxide absorbent and is chemically unreactive with sevoflurane, enflurane, isoflurane, and desflurane.