Cause of Device-Related Incident
Device factors; User errors

Clinical Specialty or Hospital Department
Clinical/Biomedical Engineering; Neurology; Pulmonary / Respiratory Therapy

Device Factors
Design / labeling error

Document Type
Hazard Reports

External Factors
*Not stated

Mechanism of Injury or Death
Burn (electrical, thermal, chemical); Electrical shock / electrocution

Support System Failures
*Not stated

Tampering and/or Sabotage
*Not stated

User Errors
Failure to read label; Incorrect control settings

UMDNS
Iontophoresis Units [12-185]; Iontophoresis Units, Drug Delivery [18-155]

Lesions and Shocks during Iontophoresis



Hazard [Health Devices Mar 1997;26(3):123-5]

Problem

A member hospital reported two separate incidents in which the skin beneath the negative electrode of an iontophoresis unit was found to be reddened following iontophoresis therapy. In addition, at the end of therapy, both patients reported receiving a shock when the iontophoresis unit was turned off. In both cases, the unit had been set at 4.0 volts for a duration of 15 min. After each case, the unit was removed from service and tested by a qualified technician, who found no problems. These incidents highlight two possible adverse outcomes of iontophoresis: 1) lesions, including burns, and 2) shocks.

Background

The goal of iontophoresis is the safe delivery of a therapeutic concentration of an ionic drug solution to a limited area of the body; the rest of the body receives only minimal exposure to the drug. This is accomplished by applying low-voltage direct current through a pair of electrodes, one of which delivers the current and the drug, and the other of which acts as a return. Reddening of the skin under one or both electrodes is a routine, clinically recognized result of iontophoresis. It is produced by increased blood flow caused by the passage of electrical current through the skin. Although complications of the procedure are typically limited to localized skin reactions such as mild lesions, more severe outcomes—such as pain, shocks, and severe lesions (in the form of electrochemical burns)—are also possible.

Discussion

Causes of Lesions and Burns

Lesions resulting from iontophoresis are seldom of thermal origin because of the low current capabilities of iontophoresis units. Rather, they are electrochemical in nature. Such lesions have been described in association with the use of biomedical instruments such as iontophoresis units, pacemakers, and other direct-current stimulators.* Mild lesions are routine and should heal relatively quickly; those reported by the hospital most likely fall into this category. However, more severe lesions—including burns—are also possible, as described below.

The primary mechanism of iontophoresis is direct-current electrolysis at the surface of each electrode; this generates HCl and NaOH at the positive and negative electrodes, respectively, altering the pH on the skin. Electrochemical burns can result if the pH increases or decreases beyond the range that the skin can tolerate. This can happen if the delivered current is too high or its duration is too great, or if the electrode is inadvertently placed over skin defects, which can lower resistance.

Burns are typically more severe under the negative electrode, where the NaOH involved in the localized electrochemical reaction can cause the formation of an alkaline medium with a pH often exceeding 9. The alkaline medium will begin to erode the insulating epidermis; this results in reduced skin resistance and therefore increased electrical current delivery to the localized area, which accelerates the erosion.

Causes of Shocks

Operators manuals for iontophoresis units caution that shocks may occur if patient leads are placed on or removed from a patient while the unit is turned on, or if, after the electrodes have been placed, the unit is turned on or off without first adjusting output to zero or minimum. However, device defects can also produce shocks, and in the two cases described here, the hospital acted correctly in removing the units from service and having them inspected by a qualified technician. Since no defects were found in either case, the shocks may have been caused by the removal of the electrode before turning the unit off. (Note, however, that even with proper operation, a minor shock may be reported at the end of a procedure as the result of increased skin sensitivity due to electrolysis at the electrode.)

Summary

Although a generally safe procedure, iontophoresis has recognized adverse side effects, including first-degree burns—and in fact, any low-voltage direct-current device has the potential to cause such injuries through electrolysis. In addition, as the reported problems indicate, shocks are possible under certain circumstances. Proper device operation and staff understanding of the causes of skin injuries associated with iontophoresis are essential to minimize the occurrence of these problems. It is also important to instruct the patient to inform the operator of any discomfort experienced during the treatment.

Recommendations

  1. Ensure that users read the operators manual for the iontophoresis unit, follow the operating procedures, and understand the associated hazards.
  2. Ensure good skin contact with the electrode. Avoid placing electrodes on areas that have been recently shaved or over skin defects; broken skin and/or gaps between skin and electrode offer reduced resistance, thereby resulting in localized higher current concentrations.
  3. Advise the patient to report any sensation of pain or burning.
  4. Adjust the current output to zero or minimum before the unit is turned on or off. Do not turn the device on until the electrodes have been placed and the lead wires have been attached to the electrodes and to the device.
  5. Do not remove the electrodes or disconnect the lead wires until the power has been turned off.
  6. If a problem occurs, remove the unit from service and have it inspected

* For additional information on direct-current burns, see Leeming MN, Ray C Jr, Howland WS. Low-voltage, direct-current burns. JAMA 1970 Nov 30;214(9):1681-4.

UMDNS Terms

  • Iontophoresis Units [12-185]
  • Iontophoresis Units, Drug Delivery [18-155]

Cause of Device-Related Incident

Device factor: Design/labeling error

User errors: Failure to read label; Incorrect control settings

Mechanism of Injury or Death

Burn; Electrical shock/electrocution


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