Hazard [Health Devices Feb 1987;16(2):44-6]

Problem

In a one-month period, two member hospitals reported incidents in which nursing staff inadvertently connected patient ECG lead wires to line power (120 VAC). In both cases, lead wire pins were plugged into the female connector of an energized line cord that was detached from an infusion device. One incident resulted in death by electrocution; the other produced severe third-degree burns that required plastic surgery.

In both incidents, ECG electrode lead wires with round male pins were inserted into a parallel blade-style female connector commonly used on detachable power cords and extension cords. In one case, however, the line cord emerged from a shelf of instruments adjacent to the monitor; its connection to a wall AC outlet was concealed. In the other instance, the line cord was plugged into a visible wall receptacle 46 cm (18 in) above the floor; both cord and cable had been draped over the bedrail, and it was reported that the patient cable had slipped off.

One of the two line cords had a molded clear plastic connector that revealed three colored conductors (black—hot, white—neutral, green—ground) that coincidentally matched frequently used ECG monitor lead wire colors (black—left arm, white—right arm, green—reference). The chassis connector on the other line cord resembled the patient connector both were black and approximately the same size. In one case, the patient cable and lead wires were the same brand as the monitor, while in the other case the cable and lead wires were generic. Although four different brands of line-powered devices were involved in these two cases (two ECG monitors and two infusion pumps), we do not specifically associate this hazard report with these four devices or with a particular electrode lead wire.

Similar incidents in which patient leads were connected to line power have been reported in connection with the use of home apnea monitors. One electrocution and four cases of electrical burns are discussed in a comprehensive study.(1)  In addition to connecting patient leads to detached energized line cords, patients were exposed to line power when lead wires were plugged into "live" extension cords and directly into wall AC receptacles. Some of these connections to line power were made by the pediatric patient being monitored, and others were made by siblings. The authors speculate that electrical burn injuries associated with electrode lead wires are very likely underreported for a number of reasons.

During the past year, manufacturers of home apnea monitors have modified the connector at the patient cable end of their lead wires. (This has required manufacturing new patient cables with modified connectors for electrode lead wires.) Most of the lead wires, however, still have an unprotected pin connector for the electrode, and the potential for an electrical shock exists for children who attempt to insert this pin connector into a line voltage source. (Two of the reported cases of electrical burns allegedly occurred when only one end of a detached lead wire was inserted into a wall AC receptacle.)

Three of the eight units in our evaluation of apnea monitors, currently in progress, have detachable line cords; when these units are operated on battery power, the line cord should be disconnected from the AC receptacle and stored. The other units can be powered by either a detachable plug-mounted low-voltage module or a backup battery. In general, ECRI questions the value of detachable line cords. While they may be considered advantageous for devices with battery backup that are frequently used in transport applications, detachable cords are prone to inadvertent disconnection (leading to battery depletion), are likely to be used with other devices, or may be left behind during transport and lost.

We encourage hospitals to request, and manufacturers to supply, electrode lead wires with a protected connector at the patient cable end. A protected connector (i.e., one that cannot be inserted into the AC receptacle) at the electrode end is also desirable for monitoring applications in the home. To maintain flexibility in the purchase and use of electrode lead wires and patient cables and to encourage competition in marketing these products, we believe that it is desirable for all manufacturers of these items to adopt the same protection mechanism. (At present, a round male pin connector is a de facto standard for connecting physiologic monitoring electrode lead wires to patient cables.) Although a patient cable with molded (nondetachable) lead wires eliminates the problem of pin connectors, this solution is more expensive—a single intermittent lead wire necessitates replacing the entire cable assembly.

One major manufacturer of cables and lead wires states that new lead wires with protected connectors are currently more expensive than those now used in most applications. As a result, hospitals may be faced with slightly higher costs during the period of transition from existing stock to the new-style lead wires and cables. However, as the sales volume of new lead wires increases, costs can be expected to drop back to present levels. In addition, the same manufacturer states that cables for the new lead wires are no more expensive than the cables now in use.

Inform manufacturers and distributors of your needs now to give them a greater incentive to supply appropriately modified electrode lead wires and patient cables as soon as possible. Avoid major purchase commitments, and attempt to minimize inventory of lead wires with unprotected connectors and their associated patient cables so that you can switch to the new lead wires and cables as soon as they are available. As it may take manufacturers some time to design, test, produce, and supply the new product line, be sure not to let inventories drop too low to meet clinical needs.

1. When available, purchase electrode lead wires with protected connectors and compatible patient cables for all ECG and respiration/apnea monitoring systems.
2. Where unprotected electrode lead wires continue to be used as existing inventories are depleted or until an acceptable alternative is available, do the following:

• Warn clinical and housekeeping personnel of the potential for electrocution as described above. Post photocopies of the warning illustration provided here in appropriate places.
• When temporarily disconnecting a patient from a monitor, either disconnect the cable from the monitor or disconnect the lead wires from the electrodes. Do not disconnect the lead wires from the patient cable.
• Hardwire or secure (e.g., with a cable clamp attached to the device) detachable medical device line cords. If this is not practical or the cord must be removed for transport, consider attaching a warning label to the female connector end of the remaining detachable line cords that states "120 VOLTS." Also, request that suppliers of leased devices with detachable line cords follow this recommendation.
• Never leave a detached line cord connected to an AC receptacle.
• Do not routinely use extension cords in the vicinity of monitoring devices.
• Store unused lead wires out of the reach of children; cut up and discard defective lead wires.
• Consider using childproof outlet caps in pediatric departments that do not have tamperproof receptacles and in homes with children under six years old.
• Bring this warning to the attention of parents who will have a child at home on a cardiorespiratory monitor. This report and warning may be freely copied for distribution to home care clinical personnel and parents.

1. Katcher ML, Shapiro MM, Guist C. Severe injury and death associated with home infant cadiorespiratory monitors. Pediatrics 1986;78(5):775-9.

UMDNS Term

Cables/Leads, ECG [15-754]

Device factor: Design/labeling error 

User error: Accidental misconnection

External factor: Power supply

Support system failures: Poor prepurchase evaluation; Use of inappropriate devices

Burn; Electrocution