Preventive Instrument Maintenance:
A Prudent Investment with Many Dividends
By Brian Kern
What a difference a decade makes. Minimally invasive procedures that were once available at only the most prestigious medical institutions are now commonplace in ORs across the country. The revolution in minimally invasive surgery continues to this day, spurred by the promise of smaller diameter incisions and quicker patient recoveries. Medical manufacturers are keeping pace with the latest surgical advances, designing smaller and often more functionally efficient instrumentation.
The current trend toward smaller diameter instrument design will continue to push the boundaries of what can be accomplished through small diameter incisions. Such instruments, in many instances, will be expected to perform many of the functions of the larger diameter instruments currently in use. It should, therefore, come as no surprise that the strains and stresses placed on these instruments will be greater. Fortunately, instruments in need of service can usually be identified through periodic inspections before they become unusable.
Having a basic understanding of how an instrument is used, including its key features, greatly facilitates the performance of functional checks. Much of this basic information can be readily obtained from the user manual. User manuals often provide useful information such as the deflection characteristics for moveable instruments.
Beyond the information found in user manuals are some universal guidelines and instrument checkpoints, which can be used to establish and manage a successful preventive maintenance program. Be certain to include OR personnel, Central Processing, and Materials Management in all aspects of the program and provide them with detailed training in the functional testing of minimally invasive instrumentation. Above all, it's critical to incorporate functional testing into a scheduled routine of preventive maintenance.
General Surgery Trocars, Sheaths, and Veress Needles
Using reusable sheaths and trocars can produce significant cost savings. The most obvious concern in the maintenance of reusable trocars is ensuring they remain sharp for every procedure. The effects of daily use, reprocessing, and subsequent sterilization ultimately determine the number of cycles between each trocar sharpening. Inspection can help gauge when a trocar should be sharpened. In general, a sharp trocar should be free of any obvious nicks or corrosion on its cutting edges. Most facilities using reusable trocars determine a preset number of procedures between sharpening.
Check endoscopic sheaths for possible curvature by gently rolling the shaft along the edge of a table. Not only can a bent shaft damage instruments passing through it, but it also causes rapid trocar dulling. Trap door valves on trocars should be checked for complete closure by removing the valve and examining the surrounding seal for obvious damage. Since valve seals are sometimes difficult to see, a helpful hint is to shine a bright light through the proximal end of the valve. Escaping light will often help pinpoint the damage.
The obvious effect of a damaged valve is a loss of insufflation gas during operative procedures. Sealing caps should be examined for excess wear, and those with enlarged or cut openings immediately replaced. As sheaths come in many different sizes, it also may be important to ensure the correct sealing cap is chosen. For instance, a sheath intended for a 5mm instrument should have a slightly smaller hole in the cap than the instrument passing through it. This ensures a good seal, which prevents the loss of insufflation gas.
Other valve-type mechanisms must also be noted, such as the trumpet and leaflet valves found on sheaths. Placing an incorrect spring into a trumpet valve may lead to incomplete valve closure and the subsequent loss of insufflation gas. Likewise, periodic replacement of worn springs is essential. Leaflet valves should be examined and replaced if the articulating edges are damaged.
As most sheaths include an insufflation port, ensuring the stopcock on the port rotates freely without excess friction is also important. A sticky stopcock should be lubricated with a non-silicone-based instrument lubricant. The correct stopcock should be placed in its appropriate sheath. An incorrect stopcock can occlude or restrict gas flow, thereby reducing the insufflation rate.
When examining Veress needles, verify sharpness using the same procedures described above. Each needle should be sharp and free of nicks and cuts. Reusable Veress needles should also be checked for bends by rolling the shaft of the needle along the edge of a table. During Veress needle assembly, the hole in the inner sheath must be aligned properly such that it points away from the outer sheath. Finally, perform a functional test to verify proper needle retraction and smooth operation of the stopcock assembly. Like trocars, Veress needles require periodic sharpening.
Endoscopic Grasping Forceps and Scissors
As endoscopic graspers and scissors evolve into even smaller sizes, their designs are becoming more complex functionally. Such designs include very small jaws/shafts, which are bent or angled, and articulating joints that may deflect perpendicular to the main axis of the shaft.
Establish protocols for examining instruments when they are new, prior to first use. For instance, if the device deflects, to what angle will it deflect when it is brand new? Unfortunately, such information is not always included in the device manual. When available, compare the degree of deflection against the manufacturer's specifications. This not only ensures the instrument was not damaged in transit but also establishes a baseline for future comparisons.
Check the shafts of straight instruments for bends as described previously, paying particular attention to those that are cautery capable. Insulated shafts should be free of any obvious cuts, nicks, or deep abrasions and tested periodically for insulation failure. Contact the manufacturer for specific information on testing insulation leakage. Instrument shafts with flush ports should be tested to ensure they are obstruction-free and equipped with a flush port cap or plug. Verify that the cap or plug forms a tight seal around the port to prevent gas loss during surgery.
Examine the jaws and boxlocks on instruments for corrosion and replace as necessary. Hinges should be inspected with a magnifying loop to ensure the pins are present, firmly in place, and undamaged. Grasping jaws should close smoothly and align properly. Return any deviation to the manufacturer for evaluation and/or repair. The cutting edges of scissors should meet without gaps as they close and should be free of pitting, corrosion, and damage. As a simple test, try cutting a latex balloon with the scissors: a sharp pair will cut the balloon smoothly and without resistance. As with trocars, establish protocols for periodic sharpening or replacement of the cutting blades in accordance with the number of uses and handling/reprocessing cycles.
Handles should move freely and smoothly. If they use a ratcheting mechanism, there should be no slippage. Insulated handles should be checked for damage and tested periodically for leakage. Return any handle showing signs of damage or leakage to the original manufacturer for repair.
Routinely check monopolar and bipolar instruments to ensure proper operation. Besides leakage, test for continuity with a multimeter to ensure proper flow of high-frequency current throughout the instrument. The multimeter is a common tool used by biomedical departments to measure various electronic parameters. Those unfamiliar with its use will benefit from a simple in-service from their biomedical department.
Properly functioning monopolar and bipolar instruments may exhibit a very low resistance to the flow of current. A resistance of one ohm or less as read by a multimeter is generally preferred, but the manufacturer should be contacted for exact testing specifications. Readings are taken with most monopolar instruments by attaching one lead of the multimeter to the electrocautery nut and the other to the jaws of the forceps. With the multimeter set to ohms, a measurement is then taken. If the readings fall outside of the specified range, return the instrument to the manufacturer for repair. For bipolar instruments, it is sometimes easier to attach the electrocautery cord to the instrument itself. Resistance readings are taken with the jaws completely closed and multimeter leads attached to the electrocautery cord.
Since graspers and other flexible instruments are routinely passed through flexible endoscopes, they must be examined thoroughly on a more frequent basis. For instance, a damaged flexible grasper jaw might not close completely, thereby increasing its effective overall diameter. Passage of such an instrument through a flexible endoscope could damage the working channel--a costly repair.
Two other special concerns with flexible instruments are pitting and kinking. Pitting on the shaft has a similar effect to that of sandpaper, potentially damaging the walls inside the instrument channel. Likewise, kinked shafts can damage the instrument channel and lead to a loss of function.
Damaged electrocautery cables are a serious risk in the OR and should be carefully checked for holes, cuts, and abrasions. The outer coating of most electrocautery cables is made of an elastic silicone rubber. Care should be taken to avoid stretching the cable to prevent separation of the wires inside. Never pull on the cord, such as when disconnecting it (grasp the plug instead) or when cleaning to remove blood (wipe). The resulting damage is visible as a kink or bend in an otherwise seemingly perfect cable.
The major risk from a broken wire is a spark gap. When the broken wires underneath the silicone rubber are in close proximity and high-frequency current begins to flow through the cable, it can spark or arc across the gap. This generates a tremendous amount of heat, which can cause the cable to catch fire. For this reason, when damage is suspected in any high-frequency cable, discard it immediately. Never attempt to repair a damaged high-frequency cautery cable. It is also useful to test high-frequency electrocautery cables with a multimeter since high resistance to current flow is a good indicator of damage.
Note that all instrument manufacturers share the same design in their high-frequency electrocautery connections. For this reason, ensure the correct cable is paired with the appropriate instrument. A general rule of thumb is never to combine one manufacturer's cable with another's device. Rather, consult the instrument manufacturer for the correct cable.
Most endoscopic retractors feature a sheath housing, which is extended or deployed once inside the body. Check curved retractors for proper curvature and fan retractors to ensure the blades extend properly and fully with easy retraction into their sheaths.
Laser instruments are generally coated with either a black or matte finish to prevent laser beam reflection in unwanted directions. As such, laser-coated instruments should be examined to ensure the matting or finish is not damaged.
Reaping the Dividends of Prevention
Implementing a comprehensive preventive maintenance program yields many dividends, not the least of which is a significant extension of the functional lifetime of OR instrumentation. Beyond the dollars and cents of day-to-day OR operations is the issue of liability. Unreliable instrumentation is simply more likely to malfunction during procedures with untold possible ramifications if the patient is harmed.
Of course, an instrument is only as reliable as its design. But a program of preventive maintenance helps ensure well-designed instruments function reliably and to specification.
Functional testing should follow a rigorous schedule with clearly articulated plans of action for instruments failing one or more test criteria.
While the initial work in setting up a preventive maintenance program is not inconsequential, it's time well spent with dividends that continue to accrue year after year.
Brian Kern is the Technical Services Manager at Karl Storz Endoscopy-America, Inc. (Culver City, Calif).
|Table 1: Functional Testing Checklist|
|PRODUCT||ITEMS TO TEST||PRODUCT||ITEMS TO TEST|
|Signs of stress fatigue (fractures)||Electrocautery||Conductance|
|Cracking||Signs of strain, cuts, abrasions, or discoloration|
|Pitting/discoloration/oxidation||Correct, properly fitting cord|
|Proper jaw alignment and closure; ease of opening and closing||Spare parts|
|Insulation testing; leakage or signs of burns, cracks, deep scratches|
|Screws, missing or loose||Flexible
|Water flushes through ports||Leakage|
|Parts disassemble with ease||Fogging|
|Sheaths||Wearing||Broken fibers (illumination/imaging)|
|Pitting||Tears or wrinkles in outer jacket|
|Bending||Moisture in ocular|
|Discoloration||Focusing rings (free and easy movement)|
|Stopcocks turn freely and stop||Annodization|
|Signs of burns or arcing||Metal flaking|
|Correct cap size||Change in bundle color (i.e., yellow)|
|Valves close completely||Telescopes||Fogging|
|Broken fibers (illumination/imaging)|
|Light Cables||Discoloration||Bends in shaft|
|Broken fibers||Image quality|
For a complete list of references click here