Induced current on the guide wire during sphincterotomy

Comparison of guidewires for successful cannulation of biliary stenosis and targeting of biliary branches in ERCP

Background and study aims Guidewires play a crucial role in endoscopic retrograde cholangiopancreatography. The ability to pass through stenosis, and the ability to seek the desired biliary branch are particularly important. In this study, we aimed to compare these specific abilities in various guidewires by using a bile duct model. Patients and methods Seven 0.025-inch angle-type guidewires (VisiGlide2, Fielder 25, EndoSelector, NaviPro, Jagwire Plus, RevoWave DualMaster, and J-WIRE prologue ST) were evaluated. To compare these, a bile duct silicone model was prepared. The time from the entry of the guidewire into the common bile duct with the stenosis to the emergence of the guidewire from the common bile duct after reaching two target intrahepatic bile duct branches was measured. Results VisiGlide 2 and Fielder 25 were the fastest guidewires, whereas Jagwire Plus was the slowest. Conclusions In this study, a guidewire with a tip deflection height of approximately 9 mm and a hydrophilic coating length of 7 to 8 cm achieved the fastest completion time for the course. In clinical practice, it is important to consider the performance required in various scenarios and to select the most appropriate guidewire. The results of this model test, which focused on the time required to complete the course around the model, can serve as a foundation for guidewire selection. This method holds potential utility in future guidewire development.

Electrophysical factors influencing endoscopic sphincterotomy

BACKGROUND

Analog computer techniques were used to measure electrosurgical power during sphincterotomy in experimental models and patients.

METHODS

Total energy and transient changes in power were measured during sphincterotomy of bile ducts in the livers of pigs, ampullae of humans post mortem, and during clinical sphincterotomy. The effect of waveform on hemostasis was studied in experiments on canine mesenteric arteries.

RESULTS

Electrosurgical waveforms (CUT, COAG, BLEND) were measured. Halving wire contact length halved energy needed to initiate cutting. The CUT waveform rarely initiated cutting at lower power settings than the BLEND waveform. With CUT, BLEND, and COAG waveforms, approximately the same energy initiated cutting. Efficiency of cutting increased linearly with power. The COAG waveform required higher power settings than BLEND or CUT to initiate cutting (p < 0.05). Force and wire diameter influenced cutting. BLEND was more effectively hemostatic than CUT (p < 0.05). COAG was significantly more hemostatic than BLEND and CUT. Cutting efficiency during clinical sphincterotomy was poor.

CONCLUSIONS

This work has practical implications. Shortening wire contact length was effective in starting a cut at suboptimal settings, whereas changing from BLEND to CUT made little difference. Increasing power setting may help if cutting does not start. BLEND stops bleeding better than CUT. COAG stops bleeding better than BLEND but cuts poorly. Cutting during clinical sphincterotomy is inefficient and can be improved.

Current induction in a fiberglass guidewire compared to conventional wires during simulated papillotomy

BACKGROUND

Current induced in a guidewire during papillotomy poses a danger of injury to the bile duct. We measured currents induced in three commercially available guidewires and a prototype fiberglass wire during simulated sphincterotomy under standard and nonstandard conditions.

METHODS

Blended current at 55 W was applied to a double-lumen papillotome grounded through a 1000 omega resistor. For extreme conditions, power was increased to 70 W using a single-lumen papillotome. Fault conditions were created with a break in the insulation at the distal end of each wire. Guidewire-induced current was measured, and safety calculations performed for adherence to accepted standards for electrosurgical devices.

RESULTS

Induced current was within safety limits for all wires tested under standard conditions. With insulation faults, one of the commercially available wires was unsafe. Under extreme conditions, with or without faults, the three commercial wires produced currents ranging from 9% to 225% above acceptable levels, while only the prototype wire remained safe.

CONCLUSIONS

Most guidewires contain metal cores that function as capacitors. Because its core is primarily fiberglass, the prototype wire generates less induced current under nonstandard conditions, thus achieving a greater margin of safety during wire-guided sphincterotomy.

ERCP guide wires

Guide wires have become an essential part of therapeutic biliary and pancreatic endoscopy. The Teflon-painted stainless steel wire still remains the standard guide wire. However, special situations call for the use of some of the more specialized guide wires mentioned in this article. The endoscopist needs to be familiar with the type that is needed for any given situation. It may be prudent and cost-saving on the part of the endoscopist to anticipate early on in the procedure the type of wire or wires that would be needed, thereby enabling the endoscopist to choose one or two guide wires that would meet his or her needs rather than having to use several wires.

Electrosurgical safety of guide wires during endoscopic sphincterotomy

A study was performed to determine whether alternate site electrosurgical burns could be caused by an inadequately insulated guide wire left in place during endoscopic papillotomy to maintain cannulation of the common bile duct. The safety of four covered guide wires and one standard guide wire was evaluated for electrosurgical safety. All four covered guide wires were coated with polyurethane or polytetrafluoroethylene (Teflon), providing insulation. Leakage currents under normal, limiting case, and fault (damaged insulation) conditions were compared to safety limits. All covered guide wires met safety limits under normal conditions, one of four covered guide wires met safety limits under limiting case conditions, and none met safety limits under fault conditions. The uncovered guide wire did not meet the safety limit under any conditions.

CONCLUSION

Without a well-insulated guide wire with intact coating, our measurements indicate that leaving a guide wire in place during papillotomy may result in an electrosurgical burn.

The effect of guidewires during electrosurgical sphincterotomy

We describe six electrosurgical incidents and one complication which occurred during guidewire-assisted sphincterotomy. Studies were conducted on three types of guidewires: Teflon painted, Teflon sheathed, and polymer coated. Scanning electron micrographs demonstrated surface imperfections in the painted Teflon guidewire coating, which allowed for potential electrical short circuits between cutting wire and guidewire through a septal defect in a double channel catheter. Septal defects were found in 25% (1 of the 4 tested) of the factory fresh sphincterotomes that were used in this study, and in 10% (6 of 57) of those used clinically. Induced current (capacitively coupled) present on the guidewires was measured at 13 to 30 mA for typical sphincterotomy settings. The induced current on sheathed guidewires, without any insulation defects, was measured at less than 1 mA at typical operating powers. As both short circuits and induced currents place the patient at risk for burns or perforation at the distal end of the guidewire, we suggest the use of a Teflon-sheathed rather than Teflon-painted guidewire, if the wire is to be left in place during sphincterotomy. The Teflon sheath offers the thickest insulation, a very low probability of surface defects, and therefore a high index of safety.

Conducted current on guidewires in single lumen papillotomes

An in vitro electrical circuit was designed to measure conducted current in plastic-coated guidewires and standard guidewires inserted in a single lumen papillotome. Single lumen papillotomes, which are more flexible than double lumen papillotomes, require the removal of the guidewire before electrosurgery due to concern over conducted current. In an in vitro electrical circuit, equivalent current was measured in both the papillotome wire and the standard guidewire. Plastic-coated guidewires did not allow any current flow. The advantages of flexible single lumen papillotomes and maintenance of deep biliary cannulation over a guidewire may be combined if insulated plastic-coated guidewires are used.