Silenced Alarm Results in “Near-Miss”

Robert N. Norton, BSc, MBChB, FRCA

To the Editor

I read with interest the deliberations regarding the use and abuse of alarms in the anesthetic environment in the Winter 2004-05 issue of the Newsletter. During my residency training I observed a near miss where a resident had silenced all monitoring alarms during a coronary artery bypass graft procedure. The resident disconnected the breathing circuit while the surgeon incised the sternum. He then forgot to reconnect it. It was only when I walked into the OR and asked why the pulse oximeter was reading 20% that he realized what had happened. Frantic efforts ensued and fortunately the patient came to no harm. But it was a salutary lesson for both of us.

I routinely use all monitors available. During my preoperative check of the anesthetic machine, I also check and activate all monitoring alarms. Some anesthetic machines and monitors are set automatically to default settings that are not appropriate. For example, monitors that have been in use recently in our hospital set the default lower oxygen saturation alarm to 88%. Following the recommendation of a colleague I set mine higher and now use 95% as the lower limit of oxygen saturation that I will accept. This gives early warning while there is still time to react.

In my practice the use of pulse oximeter tone is essential. I am continually amazed to see senior colleagues switch this off and rely on the single beat of the EKG monitor. Residents working in our team are routinely taught to use pulse oximeter tone at all times, and we stress all the information this provides: oxygen saturation, the presence of sinus rhythm or arrhythmias, and indication of cardiac arrest . We continually emphasize the importance of “tuning in their ears to the tone.” Its absence or change should spark immediate investigation, particularly when they are away from the “anesthetic end of the table.”

Robert N. Norton, BSc, MBChB, FRCA
Kent, UK