Quantification of the degradation products of sevoflurane using four brands of CO 2 absorbent in a standard anesthetic circuit

Compound A concentration in the circle absorber system during low-flow sevoflurane anesthesia: comparison of Drägersorb Free, Amsorb, and Sodasorb II

STUDY OBJECTIVE

To determine compound A concentrations in a low-flow circuit containing Drägersorb Free (Dräger, Lübeck, Germany), Amsorb (Armstrong, Coleraine, Northern Ireland), and Sodasorb II (W. R. Grace, Lexington, MA).

DESIGN

Randomized study.

SETTING

Hamamatsu University Hospital.

PATIENTS

24 ASA physical status I and II patients scheduled for general anesthesia greater than 3 hours' duration.

INTERVENTIONS

Patients were allocated to three groups of eight patients each to receive either using either Drägersorb Free, Amsorb, or Sodasorb II. Immediately before anesthesia induction, 1 kg of fresh absorbent was placed in the anesthesia canister. Anesthesia was maintained with sevoflurane (end-tidal concentration 1% to 3%) in oxygen and nitrous oxide (FIO(2) > 0.3) at a total flow of 1 L/min.

MEASUREMENTS

Inspiratory compound A concentration in the circuit was measured once every hour.

MAIN RESULTS

Maximum compound A concentrations for Drägersorb Free, Amsorb, and Sodasorb II were 2.4 +/- 0.8 (mean +/- SD) ppm, 3.1 +/- 0.5 ppm, and 28.0 +/- 10.0 ppm (p < 0.01 vs. Drägersorb Free and Amsorb). Concentrations with Drägersorb Free and Amsorb remained at less than 4 ppm throughout the study.

CONCLUSIONS

Because compound A concentrations in the circuit with Drägersorb Free and Amsorb were negligible, sevoflurane can be used at a fresh gas flow of 1 L/min with these two absorbents.

No compound a formation with Superia during minimal-flow sevoflurane anesthesia: a comparison with Sofnolime

There is concern about the toxicity of Compound (Co) A. Absorbents differ in the production of Co A during minimal-flow sevoflurane anesthesia. Strong alkali-free Amsorb does not produce Co A. It was our aim to study Superia, another new NaOH- and KOH-free CO(2) absorbent, in minimal-flow anesthesia, compared with KOH-free Sofnolime. After Ethics Committee approval, 14 consenting adult patients were included randomly by using Superia or Sofnolime as the CO(2) absorbent in the compact 750-mL canister of an ADU ventilator. After propofol and remifentanil administration, sevoflurane was given in oxygen and air (500 mL/min; fraction of inspired oxygen, 0.4), aiming at an end-tidal concentration of 2.3%-2.5%; ventilation aimed for 33-35 mm Hg PETCO(2). Compound A inspired (Co A(insp)) and expired (Co A(exp)) samples were taken for analysis, and canister temperatures were measured for 150 min. Statistical analysis was performed with the Friedman test or the Mann-Whitney U-test where appropriate. Correction for multiple testing was used. In the Superia group, no significant amount of Co A was formed, whereas in the Sofnolime group, maximum median (range) inspiratory values of 25 ppm (16 ppm) were found. The intergroup difference was P < 0.05. No difference was noticed between the two groups for the canister CO(2) absorbent temperature.

IMPLICATIONS

During minimal-flow 2.3%-2.5% end-tidal sevoflurane, no compound A (Co A) is formed with the NaOH- and KOH-free CO(2) absorbent Superia. Although Co A values with KOH-free Sofnolime are still within reported safe limits, Superia is definitely an alternative for safe clinical practice.