Another circuit block: This time the actual Bain circuit.

Sir,

The Bain Circuit is still popular in theatres with basic anaesthesia machines and for transport of intubated patients. If used to transport critically ill patients, it is possible that secretions, blood etc., may soil the elbow connector or the patient end of the circuit. Such soiled circuits may then be manually cleaned, re-sterilized by ethylene oxide (ETO) where facilities exist, or activated glutaraldehyde in places without ETO facility.

This is an incident where faulty cleaning of a Bain Circuit resulted in an unusual blockage of the circuit that was diagnosed just before it was used to transport a post operative patient.

A 54 year old male, a known hypertensive with coronary artery disease and severe anaemia underwent abdomino-perineal resection for carcinoma rectum. The Anaesthetic technique used was continuous epidural plus general anaesthesia with invasive monitoring. The patient required haemodynamic support intraoperatively, but the surgery was otherwise uneventful and the patient was prepared for shifting to the Intensive Care Unit for elective ventilation on completion of the procedure, as per hospital protocol.

The oxygen cylinder on the transfer trolley was confirmed to be full and the Bain Circuit was connected to the outlet of the Wolfe bottle. When the flowmeter was opened, the Wolfe bottle connections loosened with an explosive noise and the bottle disconnected from the screw cap, despite the Bain circuit being open at the patient end. The Bain Circuit was noticed to have water in the inspiratory limb.

A different oxygen cylinder was connected with similar results. The entire system was then systematically checked for over-pressure, starting from the oxygen cylinder. The cylinder, Wolfe bottle and connections were found to be intact.

The Bain circuit was then examined and was found to be blocked at the distal end of the inspiratory limb by a tightly wedged cotton plug, similar to the plug found at the end of the commonly available ear-bud [Figures 1 and 2].

Figure 1

Cotton plug wedged tightly in the patient end of inspiratory limb

Figure 2

Close up of plug in distal end of inspiratory limb

The circuit was changed and the transfer accomplished uneventfully. Since the patient remained on the anaesthesia ventilator during the events, he remained safe.

In this incident, a staffer had probably attempted to clean secretions from inside the Bain Circuit after removing the elbow connector using a cotton bud. The cotton plug got dislodged inside the patient end of the inspiratory limb and was stuck there, as seen in the pictures. The sudden pressure from the oxygen cylinder then wedged the plug more firmly and blocked oxygen flow (probably a good thing; the plug could have been blown into the patient).

The commonest areas that get blocked in a circuit are the narrow portions at insertion of male-female connectors and valves. Foreign bodies reported include various types of plastic caps, bungs, small rubber pieces, adhesive plaster, inspissated secretions and three-way connector blockers.[12345]

The AAGBI's “Protecting the Breathing Circuit in Anaesthesia” and the American Society of Anesthesiologists’ Closed Claims Project on “Equipment Problems as Damaging Events” are landmark publications including airway equipment related incidents such as disconnections and manufacturing defects apart from a large number of human error related events.[56]

The Bain circuit has been implicated in hypercarbia secondary to disconnection of the inspiratory limb at the machine end of the circuit.[7] However, the author was unable to find a reference to incidents involving blockage of the actual Bain breathing circuit. A report suggesting a faulty Bain Circuit actually refers to the elbow connector between the patient end of the circuit and the endotracheal tube and not the circuit itself.[8] More care needs to be exercised in handling airway equipment and training of personnel in critical equipment usage and maintenance.