Operating Room Devices

 Operating room tables are relatively simple to maintain, but height and movement problems sometimes present themselves.

In previous parts of this series, we covered electrosurgical generators (August 2003), anesthesia units (February 2004), and lasers (July 2005). While these are major items in operating rooms (ORs), they make up a small part of the equipment that is used in operations. This article will cover OR tables, cryosurgery, and wall suction.

Many biomeds do not work on OR tables, as such tables often are not electrically powered and therefore may fall outside of the scope of the biomedical or clinical engineering department. While OR tables are generally quite reliable, they do need attention from time to time. The simplest tables have head, torso, and leg sections, each of which can be adjusted to accommodate the procedure taking place.

The height of a table can be varied using pneumatics, hydraulics, motors/lead screws, or a combination of those components. Height adjustment is one of the more frequent problems with OR tables; for instance, a table may slowly sink as a procedure takes place. As our society gets heavier, we will see more complaints about “sinking” tables.

Many tables have a weight limit of 400 pounds; others can hold even more weight than that, and several have come out that are designed for the very heavy patients undergoing gastric bypass or banding surgeries.

If staff complains about the table sinking during procedures, look for leaks in the hydraulic or pneumatic systems. When testing the table, be sure to put a load on it of several hundred pounds to simulate the patient. It might take up to an hour for the table to sink. Also, use a measuring device to determine just how much the table did sink. On electrically powered units, sinking most often occurs when power is interrupted either on purpose or from a power line glitch. If the weight is great enough, the motor may slip, allowing the tabletop to settle.

One of the most common complaints from surgeons is that the table moves sideways when they lean on it. This is an indication that the floor locks are worn or misadjusted, or that the floor is not even. The table may work fine in one room and slip in another. The floor surface can also contribute to slipping (Is it wet or recently waxed?).

Most hospitals no longer have conductive floors in the OR. If the OR floor at your hospital is conductive, it must be maintained and tested under code. Some traditionalists still want drag chains on OR furniture even if the floor is nonconductive. Conductive floors were supposed to be used for safety with the thinking that sparking would be reduced, but in fact, they were less safe as they created alternate grounding paths. When combined with the no-longer-required isolated power supply for the OR, where there is no true ground alternate, ground paths can be a problem. Remember that isolated power has not been required in a hospital OR for years (See NFPA 99, issues 1999, 2002, or 2005 for details.).

The fourth type of surgery (scalpel, electrosurgery, and laser are the others) is cryosurgery. There are two basic types of cryosurgery: open and closed. With the open technique, the cryogen, often liquid nitrogen, is “painted” on the wart or skin tag with a cotton swab or dropped on using an eye dropper. Another version of open cryosugery uses the spray system, in which the aerosol is a combination of carbon dioxide and nitrous oxide. These systems are not too accurate, and the surrounding tissue is also frozen. While cryosurgery itself is not painful, the blisters it causes can be as they start to weep several days later.

With closed cryosurgery, either carbon dioxide or nitrous oxide gas is used to cool the tip of a probe that is placed on unwanted tissue. Typically, the tip will cool from -20° to -40° C, forming an ice ball on the tissue. To remove the probe without tearing the tissue, the gas flow must stop, allowing the probe to warm (or the probe can be heated on some units). The size and depth of the ice ball is directly related to the contact time. The frozen tissue is dehydrated and will fall off at some point.

With the use of ultrasound imaging, cryosurgery is being tested on tumors in the liver and other organs. Cryosurgery also is used on prostrate tumors. Some say that cryosurgery results in less nerve damage, less blood loss, and shorter hospital stays than the traditional method of “burning through” the gland.

While cryosystems are mostly mechanical, they still need to be checked on a regular timetable. Of particular concern are the hoses and fittings. Adapters should never be used, as it means that an undesignated gas is being used. Also, the hoses need to be checked for dry rot and cracks.

Wall Suction
One problem item in the OR that falls between the cracks of responsibilities in a hospital is the wall suction. In many hospitals, the facilities department has the responsibility of the suction to the wall outlet, and biomed has the responsibility from the wall to the patient. What all too many people forget is that for suction to be useful, both the level of suction (typically -18 to -23 inches of mercury) and the flow rate must be taken into consideration. If the flow rate is below 3 standard cubic feet per minute, the site will not clear as quickly, regardless of the suction level.

Low flow rates are most often caused by material in the lines. Most of that material is caused by the operator bypassing the automatic float shutoff on the canisters, allowing material to enter the lines. When the flow rate gets too low, the only solution is to clean the lines, which can be a major project, for which plumbers may have to replace some of the piping in the wall. 24×7

Review Questions

1.     If an operating room table slowly sinks during      an operation you should look for              _____________.
a)    a leak in the hydraulic or pneumatic system
b)     a patient weighing more than 400 pounds
c)    an uneven floor
d)    a and b

2.    Cryosurgery works at ___________.
a)    -20° to -40° F
b)    0° to -10° C
c)    -50° to -60° F
d)    -20° to -40° C

3.    Minimum suction flow rate at the wall is          _____________.
a)    3 liters per minute
b)    3 standard cubic feet per minute
c)    3 cubic meters per minute
d)    3 standard cubic feet per hour

Answers 1-d; 2-d; 3-b

David Harrington, PhD, director of staff development and training at Technology in Medicine (TiM), Holliston, Mass, is a member of 24×7’s editorial advisory board.

Robert Freeman is a recently retired TiM biomed at the Quincy Medical Center in Quincy, Mass.