Supplementary oxygen during Caesarean section

Abstract

We read with interest the recent letter of Edsell and Erasmus [1]. Our original paper [2] was the first national survey of practices relating to the use of the common gas outlet for administration of supplementary oxygen during Caesarean section under regional anaesthesia. The principle aim of this survey was to highlight the potential risks of the practice of disconnecting the standard anaesthetic circuit from the common gas outlet in order to use the common gas outlet to deliver supplemental oxygen for a procedure conducted under regional anaesthesia. This practice exposes the patient to two potentially unnecessary risks. The first is that of using a circuit which has been disconnected from the common gas outlet and not subsequently reconnected, and the second, the inadvertent administration of volatile anaesthetic agent to a patient having a procedure conducted under regional anaesthesia. Whilst the safety precaution of attaching the proximal end of the breathing system (the fresh gas flow connection) to the distal end of the circuit, as advocated by Edsell and Erasmus, may make the first scenario less likely, it relies on every user to remember to do this every time the circuit is disconnected, and so does not totally eliminate the risk of it occurring. Furthermore, by persisting with the use of the common gas outlet, their precaution does nothing to reduce the potential risk of inadvertent volatile anaesthetic admission. The most recently published Confidential Enquiry into Maternal and Child Health (CEMACH) report [3] recommends a separate oxygen supply should be used for the delivery of supplementary oxygen during regional anaesthesia. This follows the sad and potentially avoidable death of a mother in which a disconnected breathing circuit was at least partly implicated. Our original article [2] was inspired by a critical incident in our own hospital involving a disconnected breathing circuit, and concluded with a similar recommendation. There cannot now be any doubt that the practice of using the common gas outlet for the administration of supplemental oxygen to patients undergoing procedures under regional anaesthesia is fraught with potential for disaster. The solution is very simple and recommendations have been made. Supplemental oxygen for procedures conducted under regional anaesthesia must be administered from a dedicated source separate from the common gas outlet and standard anaesthetic breathing circuit. The practice of using the common gas outlet for this purpose should cease immediately. Units that do not have anaesthetic machines with a separate oxygen source should either upgrade their machines or provide a free-standing oxygen cylinder. We believe a statement to this effect from the Royal College of Anaesthetists and the Association of Anaesthetists could help protect all concerned from further tragedy.