Objective
The purpose of this study was to detect the incidence, prevalence, and location of insulation failures (IFs) in laparoscopic and robotic instruments.
Study Design
In phase A, a total of 78 robotic and 298 laparoscopic instruments were tested at 20 W and 2.64 kV at Mayo Clinic in Arizona. In phase B, 60 robotic and 308 laparoscopic instruments were tested at 20 W/1 kV and 20 W/4.2 kV, respectively.
Results
In phase A, the robotic group showed a higher prevalence (25/78; 32%) and incidence of IFs after 10 uses (35/44 instruments; 80%) when compared with laparoscopy (prevalence, 39/298 [13%]; incidence, 68/189 [36%]; P < .05). In phase B, IFs were detected in 81.7% of the robotic instruments and in 19.5% of the laparoscopic instruments ( P < .005).
Conclusion
There is a high incidence and prevalence of IF in endoscopic instrumentation that is more common in the robotic group.
Insulation failure (IF) is an uncommon but important cause of electrosurgical injuries in minimally invasive surgery that result from damage of the coating that insulates the instrument. Unrecognized thermal bowel injuries that are related to laparoscopic procedures have been estimated at 1-5 events per 1000 procedures that frequently occur outside the surgeon’s view. They are associated with a high mortality rate because of subsequent intestinal perforation and delayed recognition. In a recent review of the literature, an Australian group reported an overall prevalence of IF of 27%, with a rate of 39% in monopolar laparoscopic instruments. These are the 2 main reasons Australian and New Zealand guidelines now mandate routine instrument failure testing in laparoscopic surgery. At Mayo Clinic Arizona, IF for laparoscopic instruments is done on a rotational basis once weekly. However, robotic instruments were not checked for IF. Because robotic instruments are discarded after 10 uses, they have a lower potential for IF than reusable laparoscopic instruments.
Click Supplementary Content under the article title in the online Table of Contents
The aim of this prospective study is to evaluate the incidence and prevalence of IF in laparoscopic and robotic instruments.
Materials and Methods
Materials
All laparoscopic and robotic, monopolar and bipolar, reusable and disposable instruments that were in-stock that were used in gynecologic and urologic operations at Mayo Clinic Arizona were tested by 2 independent investigators. Nine robotic instruments and 60 laparoscopic instruments could not be tested during the initial testing because of being reserved for emergency surgeries.
IF testing
The IF test was carried out with a porosity detector (Micromed PD-8K; McGan Technology, LLC, Blackstone, MA). The earth clamp of the porosity detector was connected to the conductive metallic core of the instrument to be tested. A wire brush probe was then moved along the instrument shaft. IFs allow the flowing of electricity through the defect to the wire brush. Insulation defects are noted visually by a spark from the defect to the wire probe and an indicator that flashes in the front panel of the porosity detector and by an alarm sound ( Figure 1 and Supplementary video ). Figures 2-4 show a typical test layout. Defective instruments were inspected visually without magnification to ascertain whether the defect could be detected by the naked eye. Each instrument was categorized as “positive” (if IF was detected) or “negative” (if IF was not detected). The location of the defect was defined as in the proximal or distal one-half of the shaft of the instrument. Positive instruments were further subdivided into visible (defined as a visually detectable defect in the insulation) or nonvisible (defined as a defect that was not visible) to determine the impact of visual inspection for the detection of insulation defects. After the initial testing, reusable instruments were checked after each use and marked with a permanent marker that indicated the number of uses.
Study design
All instruments underwent an initial testing. Positive instruments (IF detected) were discarded. Further IF tests were performed for each negative instrument (IF not detected) after each gynecologic and urologic operation with the same porosity detector for a maximum of 10 uses (as being the maximum number of uses for robotic instruments before their disposal). Disposable instruments were also tested given that, theoretically, they are not defective before being used; they were all discarded after use.
Prevalence of IF was calculated for the total of tested instruments. Cumulative incidence was also calculated for a maximum of 10 uses, according to the Kaplan-Meier method.
Phases of study
The study was divided in 2 phases. Phase A was developed between March 1 and July 15, 2008. Appropriate testing was selected at 20 W and 2.64 kV for both laparoscopic and robotic instruments, following the company’s general recommendations that are based on the plastic sheath thickness. Phase B was carried out to eliminate the possibility that IF could have been created by a higher voltage being used in the testing during phase A in robotic instruments. In phase B, all laparoscopic and robotic instruments were tested by the same 2 independent investigators between August 30 and September 30, 2009, with the same porosity detector. The appropriate testing was selected at 20 W and 1 kV for the robotic instruments. For the laparoscopic instruments according to Intuitive Surgical Inc (Sunnyvale, CA) recommendations, the voltage was selected at 20 W and 4.2 kV, following the Karl Storz Inc (Tuttlingen, Germany) recommendations. All the laparoscopic instruments tested in phase B were from Karl Storz Inc. The authors consulted Karl Storz Inc regarding the appropriate setting according to the plastic sheath thickness.
Statistics
Contingency table analysis was performed by Fisher’s exact test. IF incidence was calculated according to the Kaplan-Meier method. Incidence of IFs in monopolar and bipolar robotic instruments was calculated according to the Kaplan-Meier method.
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