Taping jewelry won’t prevent burns
I was long taught that if a patient cannot remove their metal jewelry, one must apply tape to it to prevent it from causing a burn. The logic goes that the tape is non-conductive and provides insulation or resistance to electrical current. This supposedly prevents monopolar electrocautery current from exiting the body at the site of the jewelry and causing a burn. The problem with this teaching is, while well-intentioned, taping jewelry gives a false sense of security without offering any protection from burns.
Let’s start with electrical tape and home electricity. Electrical tape is an excellent insulator, adding such a high resistivity that, in ideal conditions, a single layer can provide substantial protection from household voltages of 120-240 V at 60 Hz.1 If the electrocautery used in surgery operated under these household conditions, applying electrical tape—not medical tape—to jewelry could (theoretically) offer some benefit. However, electrocautery differs significantly from your home’s lightbulbs.
With bipolar electrocautery, the current exits one electrode and returns to an adjacent electrode at the tip of the unit. With monopolar electrocautery, current leaves the single tip electrode and returns through the return electrode—commonly and incorrectly called the “grounding pad.”2 The return electrode pad should offer the lowest resistance path for the current to travel.
The concern with metal jewelry is two-fold. Jewelry placed close to other conductive objects can create an unintended return path for current, resulting in a burn at the site of the jewelry. Even without forming an alternate return path, metal jewelry can concentrate current density beneath it, heating the metal and the adjacent tissue enough to cause a burn. To prevent this, the return electrode should be well-adhered to dry skin, and all metal not removed from the patient’s body should be kept well away from conductive material (e.g. IV pole, bed rail, etc.). While the likelihood of an alternate, lower resistance current path being created with, for example, the IV pole with its plastic or rubber wheels is very low, it is not impossible.
Electrical tape will not provide protection against burns because electrocautery units operate at a frequency in the hundreds of kHz to low MHz range—much higher than a household’s 60 Hz. As frequency increases, more current can flow through the insulation via capacitive coupling. At very high frequencies, displacement current comes into play allowing current to flow across air gaps due to the creation of electric fields. The way to prevent current from moving in this manner is to have sufficiently large air gaps between adjacent conductive surfaces—in other words, keep the IV pole far enough away from the metal ring on a patient’s finger, and even more importantly, have a well-placed return electrode pad.
In contrast to electrical tape, medical tapes have no insulating properties; they will not stop current leakage, and they will not prevent burns. If you are going to tape metal jewelry to prevent it from getting caught on objects or falling out, at least do not fool yourself or the patient into thinking you are providing safety from burns. Patients who cannot remove, or who refuse to remove, metal jewelry should be educated on the risk of burns. If there is a high concern for burns, bipolar electrocautery should be used instead of monopolar.
It is important to note that electrical tape is not intended to provide safety to humans, but rather to isolate wires from each other.
It does not ground the patient or the electrocautery unit.