Hermann Gilly

Positive malignant hyperthermia susceptibility in vitro test in a patient with mitochondrial myopathy and myoadenylate deaminase deficiency

MALIGNANT hyperthermia (MH) is a life-threatening anesthesia-related complication characterized by a hypermetabolic response of skeletal muscle which can be triggered by anesthetic drugs such as halothane and succinlcholine. 1 Although some genes have been identified to be involved in MH (such as the ryanodine receptor gene [RYR1] and the dihydropyridine receptor [DHP] gene) the underlying molecular defect remains unclear in the majority of MH-cases. However, apart from central core disease, which is regularly associated with MH-susceptibility, the association of other neuromuscular diseases with MH has been reported anecdotally. Here we report a 41-yr-old man with a long history of progressive muscle weakness, myalgia, and recurrent myoglobinuria due to two unrelated metabolic defects, i.e., mitochondrial myopathy in combination with myoadenylate deaminase (MAD) deficiency. The patient tested positive for malignant hyperthermia susceptibility (MHS) by the halothane caffeine in vitro contracture testing (IVCT) procedure.

Absorption of carbon dioxide by dry soda lime decreases carbon monoxide formation from isoflurane degradation.

UNLABELLEDnThis study was performed to determine whether the absorption of carbon dioxide (CO(2)) influences the formation of carbon monoxide (CO) from degradation of isoflurane in dry soda lime. Isoflurane (0. 5%), CO(2) (5%), a combination of the two in oxygen, and pure oxygen were separately passed through samples of 600 g of completely dried soda lime (duration of exposure, 60 min; flow rate, 5 L/min). Downstream of the soda lime, we measured concentrations of CO, isoflurane, and CO(2) as well as the gas temperature. CO(2) increased the peaks of CO concentration (842 +/- 81 vs 738 +/- 28 ppm) and shortened the rise time of CO to maximum values (12 +/- 2 vs 19 +/- 4 min). However, CO(2) inhibited total CO formation (99 +/- 10 vs 145 +/- 6 mL). At the same time, CO(2) absorption by the soda lime decreased in the presence of CO formation (from 21.4 +/- 0. 8 to 19.4 +/- 0.9 g). The temperature of the gases increased during the passage of both isoflurane and CO(2) (to 32.6 +/- 2.0 degrees C and 39.4 +/- 4.0 degrees C, respectively), but the largest increase (to 41.5 +/- 2.1 degrees C) was recorded when isoflurane and CO(2) simultaneously passed through the dry soda lime. We assume that the simultaneous reduction in CO formation and CO(2) absorption is caused by the competition for the alkali hydroxides present in most of soda lime brands.nnnIMPLICATIONSnWe determined, in vitro, that carbon monoxide (CO) formation from isoflurane by dry soda lime is reduced by carbon dioxide (CO(2)). We believe that the potential for injury from CO is less in the clinical milieu than suggested by data from experiments without CO(2) because of an interdependence between CO formation and CO(2) absorption.

Carbon monoxide formation in dry soda lime is prolonged at low gas flow.

UNLABELLED When exposed to volatile anesthetics containing a CHF(2)-group, such as isoflurane, desiccated absorbents produce carbon monoxide (CO). In the anesthesia circuit, the anesthetic flow that passes through the absorber varies with the minute ventilation. We sought to determine CO formation at different levels of test gas flow. Isoflurane 0.5% (series A) or 0.5% isoflurane + 5% CO(2) (series B) in pure O(2) was passed through dry soda lime samples (600 g, Draegersorb 800((R))) at flows of 1, 3, 5, 7, and 10 L/min. Each experiment was performed three times. At the outlet, CO concentration, isoflurane concentration and temperature were continuously recorded. In both series, the duration of CO formation was inversely related to the test gas flow. In series B, mean CO concentrations and the calculated amount of CO formation decreased significantly with increasing flow rates, which was not the case in series A. In both series, the higher the flow rate, the higher was the temperature and the shorter the time until the isoflurane concentration increased to the set level. We conclude that anesthetic degradation in dry soda lime is finite and, as long as no CO(2) is added, will produce roughly the same amount of CO regardless of inflow rate. The inflow rate influences the duration of CO formation such that at lower minute ventilation longer CO formation can be expected. IMPLICATIONS CO formation from isoflurane degradation in dry soda lime was determined at different rates of test gas flow. The duration and, in the presence of CO(2), the total amount of CO formation were inversely related to the flow rate.

Using amsorb to detect dehydration of CO2 absorbents containing strong base.

Background Because Amsorb changes color when it dries, the authors investigated whether Amsorb combined with different strong base-containing carbon dioxide absorbents signals dehydration of such absorbents. Methods Five different carbon dioxide absorbents (1,330 g) each topped with 70 g of Amsorb were dried in an anesthesia machine (Modulus CD, Datex-Ohmeda, Madison, WI) with oxygen (Amsorb layer at the fresh gas inflow site). As soon as a color change was detected in the Amsorb, the authors tested the samples for a change in weight and carbon monoxide formation from 7.5% desflurane or 4% isoflurane. In a different experiment with the five absorbents, Amsorb was layered at the drying gas outflow site. In further experiments, the authors tested for a color change in Amsorb from drying and rehydrating and from drying with nitrogen. Finally, they dried a mixture of Amsorb and 1% NaOH and examined it for color change. Results In the experiments with Amsorb layered at the inflow, the Amsorb changed color when the water content of the samples was only marginally reduced (to a mean 13.6%), and no carbon monoxide formed. With Amsorb layered at the outflow, it changed color when the mean water content of the samples was reduced to 8.8%, and carbon monoxide formation was detected to varying degrees. The color change was independent of the drying gas and could be reversed by rehydrating. Adding NaOH to Amsorb prevented a color change. Conclusions Dehydration in strong base-containing absorbents can reliably be indicated before carbon monoxide is formed when Amsorb is layered at the fresh gas inflow. The authors assume that the indicator dye in Amsorb changes color on drying because of the absence of strong base in this absorbent.