Unusual cause of circuit failure

After uneventful induction of anaesthesia and insertion of regional nerve blocks, an 82-year-old lady was transferred from the anaesthetic room to the operating theatre for insertion of a␣dynamic hip screw. The laryngeal mask airway was connected to the circle system of the Drager Julian anaesthetic machine and anaesthesia maintained with the patient spontaneously␣breathing oxygen, nitrous oxide and isoflurane. Routine monitoring was connected. After positioning the patient on the operating table, it was apparent that depth of anaesthesia was inadequate and a bolus of propofol was administered. It was noted that the circuit reservoir bag was not filling properly despite increasing the fresh gas flows, or subsequently by using the oxygen flush. Therefore a Mapleson D circuit was attached to the external fresh gas supply of the anaesthetic machine with surgery and anaesthesia continuing uneventfully. After the case had finished, the unit encasing the circle system was removed from the machine, and an antibiotic vial cap was found lodged on it (Fig. 4). Removal of the cap corrected the circuit fault, and normal reservoir bag filling returned. The anaesthetic machine had been checked prior to the start of the list according to Drager guidelines. The automated leakage test was recorded at 100 ml.min−1 and following completion of the full check the machine was passed as safe to use. In trying to reproduce the circuit failure, it was not possible to place the vial cap behind the circle system while it was in position but only if it was removed from the machine first. We recommend that checking the Drager Julian machine should include removing the circle system in its entirety for visual inspection even if the automated leakage test does not give cause for concern.