Compound A and carbon monoxide production from sevoflurane and seven different types of carbon dioxide absorbent in a patient model

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.

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The kinetics of the reactions of the steam-carbon system

Proceedings of the Royal Society of London Series A - Mathematical and Physical Sciences ◽

10.1098/rspa.1946.0071 ◽

1946 ◽

Vol 187 (1009) ◽

pp. 129-151 ◽

Cited By ~ 73

Keyword(s):

Carbon Dioxide ◽

Carbon Monoxide ◽

Fractional Order ◽

Kinetic Scheme ◽

Correct Form ◽

Different Types ◽

Carbon Dioxide Reaction ◽

Water Gas ◽

Kinetics Of ◽

Carbon System

The kinetics of the various individual reactions which may occur in the steam-carbon system have been studied. The pressures of the separate gases have been varied in the range 10-760 mm. Essentially similar results have been obtained with coconut shell charcoal at 700° C and coal charcoal at 800° C. The steam-carbon reaction, the primary product of which is carbon monoxide, is of fractional order with respect to steam and strongly retarded by hydrogen. The carbon dioxide-carbon reaction is of fractional order with respect to carbon dioxide and strongly retarded by carbon monoxide. The rates of both these reactions can be represented closely by an expression of the form rate = k 1 p 1 /1 + k 2 p 2 + k 3 p 1 where p 1 and p 2 are respectively the pressures of steam and hydrogen for the steam reaction, and of carbon dioxide and carbon monoxide for the carbon dioxide reaction. This kinetic scheme provides a consistent interpretation of the apparently conflicting results of previous work under a variety of conditions with many different types of carbon. Further experimental work, however, is necessary to elucidate without ambiguity the mechanisms of these reactions. The water-gas reaction, CO + H 2 O = CO 2 + H 2 , takes place predominantly on the charcoal surface, and the approach to equilibrium has been studied from both sides. The forward reaction is of nearly the first order with respect to carbon monoxide and of fractional order with respect to steam; it is retarded by hydrogen and to a lesser extent by carbon dioxide. The reverse reaction is of fractional order with respect to both carbon dioxide and hydrogen, retarded by steam and unaffected by carbon monoxide. The kinetic expressions for the forward and reverse components of this heterogeneous reversible reaction combine to give the thermodynamically correct form of the equilibrium constant.

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FORMATION AND TOXICITY OF ANESTHETIC DEGRADATION PRODUCTS

The Annual Review of Pharmacology and Toxicology ◽

10.1146/annurev.pharmtox.45.120403.095847 ◽

2005 ◽

Vol 45 (1) ◽

pp. 147-176 ◽

Cited By ~ 42

Author(s):

M.W. Anders

Keyword(s):

Carbon Dioxide ◽

Carbon Monoxide ◽

Degradation Products ◽

Anesthetic Agent ◽

Common Element ◽

Compound A ◽

Anesthetic Agents ◽

Mechanisms Of Formation ◽

The Common

Toxic degradation products are formed from a range of old and modern anesthetic agents. The common element in the formation of degradation products is the reaction of the anesthetic agent with the bases in the carbon dioxide absorbents in the anesthesia circuit. This reaction results in the conversion of trichloroethylene to dichloroacetylene, halothane to 2-bromo-2-chloro-1,1-difluoroethylene, sevoflurane to 2-(fluoromethoxy)-1,1,3,3,3-pentafluoro-1-propene (Compound A), and desflurane, isoflurane, and enflurane to carbon monoxide. Dichloroacetylene, 2-bromo-2-chloro-1,1-difluoroethylene, and Compound A form glutathione S-conjugates that undergo hydrolysis to cysteine S-conjugates and bioactivation of the cysteine S-conjugates by renal cysteine conjugate β-lyase to give nephrotoxic metabolites. The elucidation of the mechanisms of formation and bioactivation of degradation products has allowed for the safe use of anesthetics that may undergo degradation in the anesthesia circuit.

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