Unusual Cause of Leak in Datex Aisys

Abstract

To the Editor: We wish to report a serious incident encountered while using the Aisys Carestation (Datex-Ohmeda, GE Health Care, Finland, through GE India). While delivering anesthesia to a young male undergoing craniotomy, we noticed that the soda lime exhausted. The Aisys Reusable Multi Absorber canister was removed, refilled with fresh soda lime, and then replaced on the Carestation. The water trap was also drained at this time. After replacement of the canister on the Carestation, a large leak was noted in the circle breathing system. The canister was removed and refitted, but the leak persisted and it was impossible to ventilate the patient’s lungs manually or in ventilator mode, even with a high fresh gas flow. Changing the breathing system to a Bain coaxial circuit connected to the alternate common gas outlet of the Aisys eliminated the leak and allowed ventilation of the patient’s lungs. A subsequent thorough examination of the Carestation revealed a soda lime granule trapped in the flap valve of the water trap, rendering that valve incompetent (Fig. 1). Removal of the granule eliminated the leak when the Carestation was checked out with a circle system. It is unclear how the soda lime granule reached the drain valve of the water trap. One possible explanation is that some brands of soda lime have a high content of dust and flowing gas may have carried that dust through the breathing system, leading to deposits caking in the condenser reservoir. Despite following the manufacturer’s instructions for refilling absorber canisters and in particular replacing the filters, we have noticed clogged dust collecting in the condenser reservoir. Choosing a brand of soda lime with low dust content may prevent this mishap.Figure 1.: (a) Water trap of Aisys with granule stuck in rubber flap valve; (b) canister with water trap.As the anesthesia workstation evolves, it becomes more complicated and less intuitive for the user attempting to troubleshoot a malfunction. The circle breathing systems on many of the new anesthesia workstations have become more complex, and some of the components may be hidden or at least not obvious. The condenser and water trap are integral components of the Aisys circle system. Education and in service training when using a new anesthesia workstation will enable early recognition of system failure. Prashant Kummar, MD Grace Korula, MD, DA Sathish Kumar, MD, DA P. A. Saravanan, MD, DA Christian Medical College and Hospital Vellore, Tamil Nadu, India [email protected]