An unusual cause of electrocardiogram interference in the operation theater.

Sir,

We report an electrocardiogram (ECG) malfunction in the operation theater (OT) during pediatric surgery. After induction of anesthesia, ECG leads of monitor (Datex-Ohmeda Division type f-CUB.09, S.N. -5161632) were connected to the patient. ECG tracing showed straight line on the monitor. We changed ECG electrodes and leads multiple times; however, there was no ECG trace on the monitor. Then another cardiac monitor was connected to a different electric board, and ECG leads were connected to the patient with different ECG electrodes. The new monitor also showed a flat line. Earthing wire connection of the monitor was also checked, which was adequately placed. A resident suddenly felt conducting current when he touched child and OT table. Immediately electrical connection of OT table was removed, which resulted in appearance of normal ECG tracing on both monitors.

In another case, pediatric warming gel mattress was put on the OT table and connected to the electrical circuit. When ECG leads were connected to the child, it showed continuous disturbance [Figure 1]. Even with the change of ECG leads and monitor, the disturbances could not be corrected. Earth wire of the monitor was also checked and found to be well connected. Removal of electrical cable of the OT table did not help. Then electrical cable of warming mattress was removed, which resulted in normal ECG tracing.

Figure 1

Continuous disturbance in electrocardiogram (ECG) with warming mattress connected to the electrical circuit and normal ECG tracing after electrical cable of warming mattress removed

It was noticed that the connecting electrical cable of OT table (first case) and of warming mattress (in the second case) had a plug with only two pins, and there was a hole at the place of earthing pin [Figure 2].

Figure 2

Electrical plug (CEE 7/7) with only two pin and a hole at the place of earthing pin and electrical socket with earthing pin

Electrocardiogram tracing artifact can simulate serious arrhythmia, thus leading to unnecessary action in the OT and intensive care unit. The passage of current through a patient can also be potentially fatal. The patient under anesthesia or sedation will not report any symptoms of current passing through his body. Hence, any unexplained ECG abnormality under these circumstances should be immediately looked into to avoid disastrous consequences. Wills et al.[1] described a macroshock electrical injury to a nurse during plugging equipment to an extension cord. Selvan et al.[2] have reported intra-aortic balloon pump failure due to ECG artifact, which occurred on placement of the transthoracic echocardiography probe over the chest due to leakage of current from echocardiography machine secondary to earthing defect. Courtney et al.[3] have reported hazard resulting from compression of an electrical cable by OT table due to a live wire contact.

In our case, the cause of electrical interference in ECG tracing was due to an electrical cable with different plug, which is not being used in India. In different countries, different types of electrical power plugs and socket have been used, which may not be interchangeable. In our case, the electrical plug was compatible with socket having the earthing pin [Figure 2]. However, in India, electrical socket do not have earthing pin to accommodate the hole present in the CEE 7/7 plug. Secondly, the same electrical lead containing the CEE 7/7 plug can be connected to OT table, cardiac monitor and warming mattress machine. Therefore, it is essential that companies should provide those electrical lead with plugs, which are compatible to the existing system in the country to prevent unnecessary distress and disastrous consequences. OT personnel and staff should also be trained so that they will not connect plugs, which are not compatible to the existing pin system.