Isolated AVR, low risk patient, only case of the day. (all times are approximate)
13.22 – Commencement of successful CPB, visual and numerical indicators were all in expected ranges, including colour of blood and saturations.
13.28 – Arterial blood colour started to change (darker) together with a gradual drop in venous saturation. Initial checks of circuit to identify any obvious issues to gas lines, including oxygen sensor, kink or detachment of gas line etc. On detachment of the gas line from the oxygenator there was no gas flow.
13.29 – Informed surgeon and anaesthetist that I was not oxygenating, and as the x-cross clamp had not been applied we came off bypass with the patient ventilated. Total time off bypass was approx. 4 mins. During this time the N+1 member of the department were asked to fetch and fit a Sechrist and the EGB was switched off, and a direct connection from the Sechrist to the oxygenator was established and isoflurane was omitted. The patient was sedated by the anaesthetic department medically. With a clear visual indication on the Sechrist blender that gas flow was established and flow could be felt post gas filter.
13.34 we commenced bypass for the second time. Second pump run was successful with no further oxygenation issues and the procedure concluded approx. 140 minutes later. Following the case the EGB was switched back on and a clear error code was displayed, E15, with an additional message on the dashboard screen reading “module/sensor defective”.
The patient recovered well, with no cognitive dysfunction .
Stockert S5 Electronic Gas Blender
The faulty EGB was removed from circulation and the engineer from LivaNova was informed. A Datix was completed and all appropriate parties informed e.g., clinical technology. The LivaNova rep subsequently sent the unit back to Germany for investigation. In addition, a request was made for the hospital estates team to test flow and pressure from the main hospital gas supply at the theatre pendants, as part of the full investigation to rule out issue locally.
Following the procedure, the unit was tested and an error code related to Module/Sensor defective appeared.
As per additional information AI-027472, Gas blender displayed the error code: E15 (Fault in AD transformer, An AD transformer fault has occurred).
This kind of malfunction can be caused by:
- improper hospital gas supply (a minimum pressure of 2 bar per connection should be observed. Indeed, input pressure too low can cause a discrepancy in the target and actual values, leading to the reported issue);
- a missed gas blender warm-up phase (user error);
- defective gas blender's component (A/D-converter);
- a defective DC/DC board.
The unit was manufactured in 2013 and no other similar events were complained.
The affected device was returned back to the manufacturer's site for repair. The device was opened, checked, and cleaned. The reported issue could not be reproduced and the device was found to be working within specifications. Subsequent functional verification testing was completed without further issues and the unit was returned to service.
During the tests performed after the first occurrence, no hardware malfunctions were detected, the unit was found working as expected and within specification.
During repair visit, front panel was replaced (reported in complaint 2023-01551).
Based on the above, it cannot be ruled out that a missed warm-up phase / an improper hospital gas supply have led to the reported issue.
No specific action was currently deemed necessary, LivaNova maintains and document periodic customer events monitoring process in order to evaluate actions for products improvement.
The importance of N+1 is demonstrated in the response to the EGB failure and the ability to change out the defective equipment with a suitable back up. the incident further demonstrates the requirement for the availability of replacement equipment and the necessity of emergency drills and protocols.