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By Brian Kern
What a difference a decade makes. Minimally invasive procedures that were onceavailable at only the most prestigious medical institutions are now commonplace in ORsacross 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, designingsmaller and often more functionally efficient instrumentation.
The current trend toward smaller diameter instrument design will continue to push theboundaries 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 largerdiameter instruments currently in use. It should, therefore, come as no surprise that thestrains and stresses placed on these instruments will be greater. Fortunately, instrumentsin need of service can usually be identified through periodic inspections before theybecome 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 informationcan be readily obtained from the user manual. User manuals often provide usefulinformation such as the deflection characteristics for moveable instruments.
Beyond the information found in user manuals are some universal guidelines andinstrument checkpoints, which can be used to establish and manage a successful preventivemaintenance program. Be certain to include OR personnel, Central Processing, and MaterialsManagement in all aspects of the program and provide them with detailed training in thefunctional testing of minimally invasive instrumentation. Above all, it's critical toincorporate functional testing into a scheduled routine of preventive maintenance.
Using reusable sheaths and trocars can produce significant cost savings. The mostobvious concern in the maintenance of reusable trocars is ensuring they remain sharp forevery procedure. The effects of daily use, reprocessing, and subsequent sterilizationultimately determine the number of cycles between each trocar sharpening. Inspection canhelp gauge when a trocar should be sharpened. In general, a sharp trocar should be free ofany obvious nicks or corrosion on its cutting edges. Most facilities using reusabletrocars determine a preset number of procedures between sharpening.
Check endoscopic sheaths for possible curvature by gently rolling the shaft along theedge of a table. Not only can a bent shaft damage instruments passing through it, but italso causes rapid trocar dulling. Trap door valves on trocars should be checked forcomplete closure by removing the valve and examining the surrounding seal for obviousdamage. Since valve seals are sometimes difficult to see, a helpful hint is to shine abright light through the proximal end of the valve. Escaping light will often helppinpoint the damage.
The obvious effect of a damaged valve is a loss of insufflation gas during operativeprocedures. Sealing caps should be examined for excess wear, and those with enlarged orcut openings immediately replaced. As sheaths come in many different sizes, it also may beimportant to ensure the correct sealing cap is chosen. For instance, a sheath intended fora 5mm instrument should have a slightly smaller hole in the cap than the instrumentpassing 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 valvesfound on sheaths. Placing an incorrect spring into a trumpet valve may lead to incompletevalve closure and the subsequent loss of insufflation gas. Likewise, periodic replacementof worn springs is essential. Leaflet valves should be examined and replaced if thearticulating edges are damaged.
As most sheaths include an insufflation port, ensuring the stopcock on the port rotatesfreely without excess friction is also important. A sticky stopcock should be lubricatedwith a non-silicone-based instrument lubricant. The correct stopcock should be placed inits appropriate sheath. An incorrect stopcock can occlude or restrict gas flow, therebyreducing the insufflation rate.
When examining Veress needles, verify sharpness using the same procedures describedabove. Each needle should be sharp and free of nicks and cuts. Reusable Veress needlesshould also be checked for bends by rolling the shaft of the needle along the edge of atable. During Veress needle assembly, the hole in the inner sheath must be alignedproperly such that it points away from the outer sheath. Finally, perform a functionaltest to verify proper needle retraction and smooth operation of the stopcock assembly.Like trocars, Veress needles require periodic sharpening.
As endoscopic graspers and scissors evolve into even smaller sizes, their designs arebecoming more complex functionally. Such designs include very small jaws/shafts, which arebent or angled, and articulating joints that may deflect perpendicular to the main axis ofthe 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. Whenavailable, compare the degree of deflection against the manufacturer's specifications.This not only ensures the instrument was not damaged in transit but also establishes abaseline for future comparisons.
Check the shafts of straight instruments for bends as described previously, payingparticular attention to those that are cautery capable. Insulated shafts should be free ofany 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-freeand equipped with a flush port cap or plug. Verify that the cap or plug forms a tight sealaround 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, firmlyin place, and undamaged. Grasping jaws should close smoothly and align properly. Returnany deviation to the manufacturer for evaluation and/or repair. The cutting edges ofscissors 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 pairwill cut the balloon smoothly and without resistance. As with trocars, establish protocolsfor periodic sharpening or replacement of the cutting blades in accordance with the numberof uses and handling/reprocessing cycles.
Handles should move freely and smoothly. If they use a ratcheting mechanism, thereshould be no slippage. Insulated handles should be checked for damage and testedperiodically for leakage. Return any handle showing signs of damage or leakage to theoriginal manufacturer for repair.
Routinely check monopolar and bipolar instruments to ensure proper operation. Besidesleakage, test for continuity with a multimeter to ensure proper flow of high-frequencycurrent throughout the instrument. The multimeter is a common tool used by biomedicaldepartments to measure various electronic parameters. Those unfamiliar with its use willbenefit from a simple in-service from their biomedical department.
Properly functioning monopolar and bipolar instruments may exhibit a very lowresistance to the flow of current. A resistance of one ohm or less as read by a multimeteris generally preferred, but the manufacturer should be contacted for exact testingspecifications. Readings are taken with most monopolar instruments by attaching one leadof the multimeter to the electrocautery nut and the other to the jaws of the forceps. Withthe multimeter set to ohms, a measurement is then taken. If the readings fall outside ofthe specified range, return the instrument to the manufacturer for repair. For bipolarinstruments, it is sometimes easier to attach the electrocautery cord to the instrumentitself. Resistance readings are taken with the jaws completely closed and multimeter leadsattached to the electrocautery cord.
Since graspers and other flexible instruments are routinely passed through flexibleendoscopes, they must be examined thoroughly on a more frequent basis. For instance, adamaged flexible grasper jaw might not close completely, thereby increasing its effectiveoverall diameter. Passage of such an instrument through a flexible endoscope could damagethe working channel--a costly repair.
Two other special concerns with flexible instruments are pitting and kinking. Pittingon the shaft has a similar effect to that of sandpaper, potentially damaging the wallsinside the instrument channel. Likewise, kinked shafts can damage the instrument channeland lead to a loss of function.
Damaged electrocautery cables are a serious risk in the OR and should be carefullychecked for holes, cuts, and abrasions. The outer coating of most electrocautery cables ismade of an elastic silicone rubber. Care should be taken to avoid stretching the cable toprevent separation of the wires inside. Never pull on the cord, such as when disconnectingit (grasp the plug instead) or when cleaning to remove blood (wipe). The resulting damageis 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 thesilicone rubber are in close proximity and high-frequency current begins to flow throughthe 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 anyhigh-frequency cable, discard it immediately. Never attempt to repair a damagedhigh-frequency cautery cable. It is also useful to test high-frequency electrocauterycables with a multimeter since high resistance to current flow is a good indicator ofdamage.
Note that all instrument manufacturers share the same design in their high-frequencyelectrocautery connections. For this reason, ensure the correct cable is paired with theappropriate instrument. A general rule of thumb is never to combine one manufacturer'scable with another's device. Rather, consult the instrument manufacturer for the correctcable.
Most endoscopic retractors feature a sheath housing, which is extended or deployed onceinside the body. Check curved retractors for proper curvature and fan retractors to ensurethe blades extend properly and fully with easy retraction into their sheaths.
Laser instruments are generally coated with either a black or matte finish to preventlaser beam reflection in unwanted directions. As such, laser-coated instruments should beexamined to ensure the matting or finish is not damaged.
Implementing a comprehensive preventive maintenance program yields many dividends, notthe least of which is a significant extension of the functional lifetime of ORinstrumentation. Beyond the dollars and cents of day-to-day OR operations is the issue ofliability. Unreliable instrumentation is simply more likely to malfunction duringprocedures with untold possible ramifications if the patient is harmed.
Of course, an instrument is only as reliable as its design. But a program of preventivemaintenance helps ensure well-designed instruments function reliably and to specification.
Functional testing should follow a rigorous schedule with clearly articulated plans ofaction for instruments failing one or more test criteria.
While the initial work in setting up a preventive maintenance program is notinconsequential, it's time well spent with dividends that continue to accrue year afteryear.
Brian Kern is the Technical Services Manager at Karl Storz Endoscopy-America, Inc.(Culver City, Calif).
|PRODUCT||ITEMS TO TEST||PRODUCT||ITEMS TO TEST|
|Hand Instruments||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 Endoscopes||Deflection|
|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 (|
|Valves close completely||Telescopes||Fogging|
|Broken fibers (illumination/imaging)|
|Light Cables||Discoloration||Bends in shaft|
|Broken fibers||Image quality|
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