Circulation 80,350 • Volume 21, No. 2 • Summer 2006   Issue PDF

Line Isolation Still Important

Patrick Noud, MD; David Gaba, MD; Don Martin, MD; Jan Ehrenwerth, MD; Mike Mahan, PE

Has there been a change in the recommended use of line isolation monitors? We had an alarm today and we were told by our engineering department to essentially ignore it, as they are not even being placed in new ORs. They say the equipment maintenance and use of ground fault circuit interrupters (GFCIs) has virtually eliminated any chance of patient harm.

Could you update me on this, or point me to a link on how we should be approaching this issue in 2006? Thanks so much.

Patrick Noud, MD


In Reply:

Dear SIRS:

1) We are a Federal (VA) Hospital. About 11 years ago we designed a new building that opened about 9 years ago. We were told that isolated power was no longer required by code, but we could choose it if we wanted to.
2) I chose isolated power in the OR because:
A) It is a passive safety system that does not depend on an active component (GFCI) on every circuit. It is built into the isolation from ground.
B) If a medical device has a first-fault, the circuit remains ON and all items on that circuit have the same level of safety as with standard 3-wire circuitry AND you are alerted to a problem; this is useful as other devices might still be on the same circuit. With a GFCI, the circuit “pops” to off so that all devices on it are without power. Further, you may not be immediately aware as to whether the failure was due to a ground fault or some other problem.
C) I myself would consider the OR a “wet location.” Most big cases have lots of blood and saline squirted around, not to mention the possibility of patient sweating, and rare circumstances that are not usually wet could become so in unusual situations. I think that ICUs could also fall into this category, but they may not traditionally use isolated power.
3) My guess is that the cost differential is small WHEN AMORTIZED over the lifetime
of the OR suite. I’m not sure that there isn’t more expense with a building full of GFCIs in trouble-shooting them and the like vs. an isolated line system.
4) I believe that in such matters knowledgeable clinicians should essentially have the final say, in consultation with the engineers, not the other way around. Building only to code may NOT necessarily be the optimal thing for patient safety.
5) Even with an isolated power system, you do STILL need to ensure that all devices have
a ground wire. This will handle (at least for macroshock protection) a double fault, as well as any leakage currents.

David Gaba, MD
Professor of Anesthesia
Associate Dean for Immersive and Simulation-based Learning
Stanford University
VA Palo Alto Healthcare System

Dear SIRS:

First, the national requirements for isolated power, and for ground fault interruption, come, to the best of my knowledge, from the NFPA. The applicable standard is NFPA 99 – Standard for Health Care Facilities 2005 edition, Chapter 4 – Electrical Systems. The particular sections that are relevant to this discussion are (Wet Locations), (Isolated Power Systems), and (Line Isolation Monitors).

These standards are available on the NFPA web site in “read only,” copyrighted format. However, as I understand them for wet locations, they require either isolated power systems, or ground fault circuit interruption (GFCI); and it qualifies GFCI to situations where power interruption is tolerable (in the case of a short circuit).

Obviously, as you know, local and state standards may vary from the NFPA. Finally, the ASA itself does not get more specific than to say, in its “Guidelines for Non-operating Room Anesthetizing Locations,” that “In any anesthetizing location determined by the health care facility to be a ‘wet location’ (e.g., for cystoscopy, arthroscopy, or birthing room in labor and delivery), either isolated power or electric circuits with ground fault circuit interrupters should be provided.”

I’ll copy this email to Dr. Jan Ehrenwerth, our representative to NFPA, for his additions or corrections. Thanks, and good luck with your OR construction!

Don Martin, MD
Chair, Committee on Equipment and Facilities
American Society of Anesthesiologists

Dear SIRS:

I am happy to provide you with information about isolated power and line isolation monitors (LIMs). I am the ASA representative to NFPA, and have written and lectured on the subject many times. For reference, please see my chapter (#8) on “Electrical Safety” in Barash’s
Clinical Anesthesia. In 1983, the NFPA (which sets most fire standards) removed the requirement for isolated power and LIMs from ORs that do not use flammable anesthetic agents. This rule was originally developed as a fire safety standard. Therefore, no explosion risk, no need to keep the rule. It made sense to them. What they did not account for, was the huge increase in electrical equipment, often with very wet floors.

Note, however, that NFPA did not say, “Do not use isolated power,” but rather, “ ‘It is not required, but optional.”

Since isolated power is somewhat more expensive (the incremental cost is about $3000–5000 per OR), many hospitals have taken the shortsighted view to leave it out. Therefore, most ORs have no more electrical safety protection than your dining room. Even your kitchen and bath have GFCIs, which are better than nothing. I feel strongly that isolated power should be retained. Hospital engineers are often misinformed or wrong, and use made-up facts to support their argument. As an example, at Yale University in the past 10 years, we have built or remodeled 24 ORs and ALL HAVE ISOLATED POWER AND LIMs.

There are 2 ways to proceed, if you feel as I do, that this is an important safety feature. One is to say, “This is what we want, and we have to have it!” I feel the better approach is for the Anesthesia and Surgery Departments to jointly declare that the ORs are WET LOCATIONS (the same as your kitchen or bathroom). This is easy to do: Think of cystoscopy, irrigation fluids, trauma blood loss, etc.). I am not sure what code they are using that says ORs are
not wet locations. However, local practice can always overrule a national code, especially if one is going to a safer system. I think that you have to be insistent on the OR being a wet location. Once that is accepted then the CODE states that they MUST use isolated power (LIMs) or GFCIs. GFCIs are generally felt not to be acceptable in ORs, because they cause interruption of power. This is fine in a bathroom, but in the OR it can be hazardous. If the GFCI trips, the faulty piece of equipment must first be identified and then unplugged, before the circuit breaker can be reset. This is complicated by the fact that most new ORs have the circuit breaker panel located outside the OR, and it can be difficult to identify which panel controls a given OR. The only safe way to use GFCIs in the OR is to make every electrical outlet its own branch circuit. This is probably more expensive than isolated power.

In response to the question of responding to a LIM alarm – the answer is absolutely! The person who said to ignore it should be sent back to school, or not be working in an OR. The alarm is almost always significant, if the LIM is a newer generation that alarms at 5 milliamps. The very old LIM, which alarms at 2 milliamps, may give a false alarm. Obviously if you have isolated power in the OR, you would not have a GFCI at the time.

It is important to fight this battle early in the design process, since once the walls are up, it is too late and too expensive to change. I am happy to speak with anyone about this at any time.

Jan Ehrenwerth, MD
Professor of Anesthesiology
Yale University

Dear SIRS:

The advantage of isolated power systems for critical locations in hospitals is that they provide safe dependable power that is not interrupted by trips. Instead, the LIM gives an indication that there is a leakage problem before there is any loss of power. The leakage is cumulative. When looking for the cause of an alarm it’s generally the last item plugged in! The alarm threshold was increased from 2 Ma to 5 Ma in 1978. If a system is experiencing a high number of alarms it should be checked to assure that it is not using the pre-1978 threshold.

Mike Mahan, PE
North Carolina Baptist Hospital
Winston-Salem, NC