Factors affecting insulation failure in reusable surgical devices

IF of surgical instruments is caused by excessive reuse of instruments, particularly with repetitive passage through trocars, frequent mechanized sterilization processing, and high-voltage applications. The problem that surgeons face is that IF is not always visible, and for this reason regular inspections are recommended using a dedicated detector^7,15,16. The frequency of IF varies from device to device (Table 3). Yazdani et al. reported an overall IF prevalence of 27% in laparoscopic instruments²². In another report, this value was as high as 81.7%¹¹. Therefore, regular inspections should be standard procedure at hospitals; however, only a few facilities actually carry out regular inspections. Additionally, the less visible the damage, the higher the current density is, which may make adverse events more likely^1,5.

In this study, we examined the relationship between the number of cleanings and IF but found no statistically significance. Reusable products are sold for long-term use, and, in fact, our results showed that long-term use was not always related to IF. When appropriate cleaning is performed, the IF in reused instruments is thought to be influenced by whether the equipment is energized, rather than the duration of use. Unlike advanced bipolar and ultrasonic energy devices, which affect the tissue between the tips of the device, monopolar devices conduct electricity between the active and dispersive electrodes, and this difference in mechanism can lead to IF^1,5. The use of high voltages increased the risk of insulation damage and capacitive coupling; as such, the operator should understand these restrictions. In a survey of members of the American College of Surgeons, 18% of surgeons had experienced IF or a capacitive coupling injury, and 54% knew a colleague who had a stray electrical burn⁴. Capacitance is defined as stored electrical charge when two conductors are separated by a nonconductive dielectric, also called an insulator²³. Capacitive coupling occurs when the circuit is completed through the dielectric. Charge will then be stored in the capacitor until either the generator is deactivated or a pathway to complete the circuit is achieved. By its very nature, capacitive coupling can occur only with the use of monopolar instrumentation, and it is not a risk in bipolar instruments because current passes only between the two tips of the active electrodes.

An endoscopic instrument is divided into four zones: near the tip (Zone 1), from the port to the tip (Zone 2), the part passing through the port (Zone 3), and near the operator’s hand (Zone 4)⁶. The surgeon’s attention is focused in the Zone 1, and the surgeon expects 100% of the electrosurgical energy to be delivered only to the tissue in that zone. However, the current may be passed inadvertently into the Zones 2–4. Although the sites of IF were in Zones 2 or 3⁶, those of gynecology were more proximal compared to the others. Procedure, port, and the load on the port may be different depending on the specialty. In this study, it was not possible to determine the differences in ports related to the frequency of IF, as various ports were used. However, since there was no IF detected in the thoracic surgery equipment, it can be inferred that wound retractors may be less prone to damage the devices, in line with a previous report⁹.

In this study, 75% of the instruments showing IF were from one company. Since this research did not involve continuous monitoring of the IF from the beginning of product use, and there is a possibility that insulation may have been already improved, it was deemed unfair to disclose the name of the company. The purpose of this research was not to identify defects in a specific product, but rather to investigate the relationship between IF caused by usage and the duration of use. The insulation material applied to laparoscopic instruments is typically a heat shrink material made from a variety of compounds including polyvinylidene fluoride, polyethylene, and polyvinyl chloride. Most laparoscopic devices have an insulation layer that is at least 0.008 cm thick⁹. Therefore, product differences in insulators may have affected the results. Furthermore, a prospective study of differences in IF frequency between robotic surgery and laparoscopic surgery equipment¹¹ reported that product differences may have more impact on IF than usage.

We examined the relationship between the number of cleanings and IF of different instruments used in endoscopic surgery. Cleaning methods and frequency have been previously reported as the causes of IF¹⁶; however, it has been found that, even after long-term use, IF may not occur. Therefore, we considered the differences in the instrument manufacturer and the usage methods to be a bigger influence on IF than the cleaning methods and usage periods.

Limitations

There are several limitations to this study; it was a single-facility study, and the number of measurements were limited. Since the results were based on a single measurement and not on continuous inspection, it is unknown when the devices were damaged. However, visual inspections were performed regularly, and the instruments were used for long periods of time without causing adverse events. At the time of the study, robotic surgery had just been introduced at our hospital and, as such, our study did not consider robotic instruments.