An

Improved Operating

Room

Demagnetizer

Herbert J. Nevyas, MD \s=b\ An operating room demagnetizer that utilized a pulsed, smoothly decaying oscillating magnetic field is described. The Instrument can demagnetize a number of surgical instruments at one time and can provide instantaneous and com-

plete demagnetization. (Arch Ophthalmol 95:2209, 1977)

increasing popularity Thesurgical techniques with

of microin ocular it some of the surgery brings special problems of dealing with extremely fine instruments and suture materials. One of these problems is that of magnetism: the finest needles, which may weigh only 0.1 mg and measure only 5 mm in length, can become magnetized by processes in manufacture, by proximity to electrical equipment (eg, foreign body magnets), and even by the earth's magnetic field. Surgical instruments sometimes also become magnetized.

MAGNETIZED INSTRUMENTS To attempt to work with magnetized instruments or needles can be a frustrating chore indeed. The surgeon may be disheartened when, after passing a needle through tissue, the needle follows the needle-holder backward as the opened instrument is

removed. There is considerable expertise involved in the removal of a needle-holder from the magnetized needle in such a way that the needle is not drawn out of the tissue into which it has just been placed. I have designed a light, inexpensive, operating room instrument that completely demagnetized needles or instruments in a few seconds. When the need for demagnetization occurred during surgery, a sterile drape was placed over this demagnetizer, the

magnetized instruments were placed top of the drape, and the demagnetizer was activated by pressing the activating button through the drape. on

The instruments were then removed, and they were free of magnetism. New sutures in the protective envelope could routinely be demagnetized by the operating room personnel in just a few seconds. Likewise, in only a few seconds per load, all instruments could be placed on top of the unit and demagnetized several times a year. SURGICAL DEMAGNETIZERS

Surgical demagnetizes

therefore, such demagnetizers

for publication Jan 8, 1977. From the Wills Eye Hospital and the Scheie Eye Institute of the Presbyterian-University of Pennsylvania Medical Center. Reprint requests to 1930 Chestnut St, Philadelphia, PA 19103 (Dr Nevyas).

Fig 1.—Operating

room

demagnetizer.

cannot

protracted periods operated without overheating. The operator must bring each instrument individube

Accepted

in present

consist of an iron-cored coil that is activated with 117 V ac, creating a stable alternating magnetic field. The field is maintained continuously, and use

Fig

for

2.—Circuit

diagram

of

to the demagnetizer and then draw the instrument away by hand so that diminishing lines of oscillating magnetic force will gradually be cut and the intensity will be lessened up to arm's reach of the operator. This technique is slow and cumbersome, and the demagnetization is necessarily incomplete because some strength of field is still present at arm's length from the demagnetizer.

ally

OPERATING ROOM DEMAGNETIZER

The operating room demagnetizer contains a large iron-cored coil that is placed in series with a condenser calculated to create a resonant circuit. The condenser is charged when the activating button is depressed, and then the condenser is switched into the circuit as the button is released. The "ringing circuit" that is thus created results in a single surge of current that produces a rapidly oscillating and smoothly decaying magnetic field. The decaying magnetic field completes demagnetization in a fraction of a second, and since the magnetic field is pulsed and the coil need not operate continuously, a much stronger magnetic field can be used. And, because the demagnetizer "rings out" to extinction, demagnetization is

complete.

The operating room demagnetizer is supplied by Keeler/Diversatronics, Inc, Broomall, l'a.

demagnetizer.

-¡-^-AA^V-K|117 Vac

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An improved operating room demagnetizer.

An Improved Operating Room Demagnetizer Herbert J. Nevyas, MD \s=b\ An operating room demagnetizer that utilized a pulsed, smoothly decaying oscil...
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