soda-lime and potassium-hydroxide

In this study we sought to determine whether an absorbent in which little carbon monoxide (CO) forms has a correspondingly small capacity to absorb carbon dioxide (CO(2)). Completely dried samples (600 g) of Baralyme (A), Drägersorb 800 (B), Drägersorb 800 Plus (C), Intersorb (D), Spherasorb (E), LoFloSorb (F), Superia (G), and Amsorb (H) were exposed to a flow of 0.5% (A-H; n = 4-5) and 4% isoflurane (F-H; n = 3) in pure oxygen at 5 L/min for 60 min. Downstream CO concentration, temperature, and isoflurane concentration were recorded every 60 s to calculate CO formation and isoflurane loss. The CO(2) absorption capacity of each brand was determined by passing 5.1% CO(2) in oxygen (flow, 250 mL/min) through untreated samples (30 g; n = 5) until the outlet CO(2) concentration reached 0.5%. CO formation was largest in absorbents containing potassium hydroxide (A and B) and negligible in absorbents not containing any alkali hydroxide (F-H). The outlet temperature correlated with CO formation, but the isoflurane loss did not. The duration of CO(2) absorption also did not correlate with CO formation. We conclude that absorbents that allow only very little CO formation are not necessarily poor CO(2) absorbents.. In an in vitro study, carbon dioxide (CO(2)) absorption capacity and possible carbon monoxide (CO) formation were tested in different absorbent brands. Absorbents with very small CO formation are not necessarily poor CO(2) absorbents.

Topics: Absorption; Algorithms; Anesthesia; Anesthetics, Inhalation; Calcium Compounds; Carbon Dioxide; Carbon Monoxide; Hydroxides; Isoflurane; Oxides; Potassium Compounds; Sodium Hydroxide; Temperature

In an in vitro study, less compound A was formed when a KOH-free carbon dioxide absorbent was used. To confirm this observation we used a lung model in which carbon dioxide was fed in at 160 ml min(-1) and sampling gas was taken out for analysis at 200 ml min(-1); ventilation aimed for a PE'CO2 of 5.4 kPa. The soda lime canister temperatures in the inflow and outflow ports (Tin and Tout) were recorded. In six runs of 240 min each, a standard soda lime, Sodasorb (Grace, Epernon, France) was used and in eight runs KOH-free Sofnolime (Molecular Products, Thaxted, UK) was used. Liquid sevoflurane was injected using a syringe pump to obtain 2.1% E'. Compound A was measured by capillary gas chromatography combined with mass spectrometry. Median (range) compound Ainsp increased to a maximum of 22.7 (7.9) ppm for Sodasorb and 33.1 (20) for Sofnolime at 60 min and decreased thereafter; the difference between groups was significant (P<0.05) at each time of analysis up to 240 min. The canister temperatures were similar in both groups and increased to approximately 40 degrees C at 240 min. Contrary to expectation, compound A concentrations were greater with the KOH-free absorbent despite similar canister temperatures with both absorbents.

Topics: Absorption; Anesthesia, Closed-Circuit; Anesthetics, Inhalation; Calcium Compounds; Carbon Dioxide; Ethers; Humans; Hydrocarbons, Fluorinated; Hydroxides; Lung; Methyl Ethers; Models, Biological; Oxides; Potassium Compounds; Sevoflurane; Sodium Hydroxide

Normal (hydrated) soda lime absorbent (approximately 95% calcium hydroxide [Ca(OH)2], the remaining 5% consisting of a mixture of sodium hydroxide [NaOH] and potassium hydroxide [KOH]) degrades sevoflurane to the nephrotoxin Compound A, and desiccated soda lime degrades desflurane, enflurane, and isoflurane to carbon monoxide (CO). We examined whether the bases in soda lime differed in their capacities to contribute to the production of these toxic substances by degradation of the inhaled anesthetics. Our results indicate that NaOH and KOH are the primary determinants of degradation of desflurane to CO and modestly augment production of Compound A from sevoflurane. Elimination of these bases decreases CO production 10-fold and decreases average inspired Compound A by up to 41%. These salutary effects can be achieved with only slight decreases in the capacity of the remaining Ca(OH)2 to absorb carbon dioxide.. The soda lime bases used to absorb carbon dioxide from anesthetic circuits can degrade inhaled anesthetics to compounds such as carbon monoxide and the nephrotoxin, Compound A. Elimination of the bases sodium hydroxide and potassium hydroxide decreases production of these noxious compounds without materially decreasing the capacity of the remaining base, Ca(OH)2, to absorb carbon dioxide.

Topics: Absorption; Anesthetics, Inhalation; Calcium Compounds; Carbon Dioxide; Carbon Monoxide; Chromatography, Gas; Desflurane; Desiccation; Ethers; Hydrocarbons, Fluorinated; Hydroxides; Isoflurane; Methyl Ethers; Oxides; Potassium Compounds; Sevoflurane; Sodium Hydroxide

Nitrogen dioxide is formed during delivery of inhaled nitric oxide for the treatment of patients with pulmonary hypertension. Soda lime has been shown to absorb nitrogen dioxide. We tested three different commercially available soda lime preparations (Sodasorb, Drägersorb 800 and Sofnolime) for their efficacy in absorbing nitrogen dioxide and nitric oxide during simulated nitric oxide inhalation. All soda lime preparation absorbed nitrogen dioxide (15%, 24% and 34%, respectively). To test if this difference could be attributed to the potassium hydroxide (KOH) content of the different preparations, two other preparations with a higher (3.0% and 7.3% w/w, respectively) KOH content were tested and we found an increase in nitrogen dioxide removal up to 47% and 46%, respectively. We conclude that soda lime absorbed nitrogen dioxide during nitric oxide inhalation. This effect seemed to be moderate under simulated clinical conditions, but increased using soda lime with a higher KOH content. Nevertheless, we recommend continuous monitoring of inspired nitrogen dioxide concentration during clinical inhalation of nitric oxide.

Topics: Absorption; Administration, Inhalation; Calcium Compounds; Gas Scavengers; Humans; Hydroxides; Nitric Oxide; Nitrogen Dioxide; Oxides; Potassium Compounds; Sodium Hydroxide; Vasodilator Agents

The various components of commercial soda lime (sodium hydroxide, potassium hydroxide, calcium hydroxide, barium hydroxide) were studied in terms of their reactivity with sevoflurane at its boiling point (59 degrees C). A simple closed system, a reflux cooler, served as a model. Analyses were performed by GC/MS. Besides sevoflurane, we identified four compounds: A, B, C, and D. Free methanol, formaldehyde and formic acid could not be found. Presumably methanol is transferred from an intermediate formalin-semiacetal of the hexafluorisopropanol. Calcium hydroxide and barium hydroxide showed little reaction with sevoflurane, whereas larger amounts of reaction products were observed with sodium hydroxide and potassium hydroxide. The alkali hydroxides of sodalime are presumably responsible for its reaction with halogenated inhalation anaesthetics. We therefore conclude that decomposing reactions of halogenated inhalation anesthetics with dry soda lime could be prevented by using a newly developed soda lime.

Topics: Anesthetics, Inhalation; Barium Compounds; Calcium Compounds; Calcium Hydroxide; Gas Chromatography-Mass Spectrometry; Hydroxides; Methyl Ethers; Oxides; Potassium Compounds; Sevoflurane; Sodium Hydroxide