Effect of optical fiber diameter and laser emission mode (cw vs pulse) on tissue damage profile using 1.94 µm Tm:fiber lasers in a porcine kidney model.

PURPOSE: To evaluate the ablation capacity using two Thulium fiber lasers (TFL) in a porcine kidney model. METHODS: All tissue samples were mounted on a motorized stage for a precise speed of cutting. A continuous wave (cw) TFL and a super pulsed (SP) TFL were used at power settings of 60 and 120 W with 200 and 600 µm laser fibers. After lactate dehydrogenase staining, histological evaluation was performed to measure the vaporization volume (VV), ablation depth (AD), thermo-mechanical damage zones (TMZ), coagulation zones (CZ) and the carbonization grade (CG). RESULTS: At 120 W, no significant differences were seen between 200 and 600 µm fibers utilizing the cw TFL regarding VV (24.6 vs. 28.2 mm3/s), AD (5.6 vs. 5.7 mm), TMZ (0 vs. 0 mm2) and CZ (18.1 vs. 12.3 mm2). Using the SP TFL, no significant differences between both fiber diameters with regard to VV (4 vs. 6.2 mm3/s), AD (2.7 vs. 3.4 mm), TMZ (1 vs. 2.6 mm2) and CZ (3.1 vs. 2.2 mm2) at 120 W were found, respectively. However, the VV of the cw TFL at 60 W was significantly less compared to 120 W using 200 and 600 µm fibers, respectively, whereas the SP TFL did not show significant differences between 60 and 120 W with regard to VV. SP TFL showed a consistently lower CG compared to cw TFL. CONCLUSIONS: This experiment suggests that there is no significant difference using 200 or 600 µm laser fibers in cw or SP TFLs. However, the cw TFL produces a coagulation zone three to five times larger than the SP TFL regardless of the fiber diameter.

Thermal injury to common operating room materials by fiber optic light sources and endoscopes.

PURPOSE: To determine the thermal energy damage potential by heat sources, such as endoscopes and fiber optic light cables, in contact with materials commonly placed around an operating room (OR) table. MATERIALS AND METHOD: Injury by xenon and halogen light sources were tested by direct and indirect contact using fiber optic light bundle cables and scopes at light intensities between ranging from Standby to 100%. The scopes had diameters ranging from 2.7 mm to 10 mm and were set at varying angles. The materials tested were surgical drapes, cotton towels, child shirts, child pants, lap sponges, X-ray detectable sponges, and Mayo covers. The damage potential was determined qualitatively by presence of smoking or smell of burning. RESULTS: Permutations involving direct contact were able to cause thermal injury, while permutations involving indirect contact, endoscopes, or halogen lamp were not. The xenon light source with the fiber optic light cable created thermal injury at light intensities of 50%, 75%, and 100%. Time to injury increased as light intensity was decreased. Only the surgical drape, child shorts, and cotton towel showed evidence of burn injury. CONCLUSIONS: This report supports the potential for thermal injury to the patient secondary to fiber optic light sources, although this potential may be limited in extent. The injury risk can be reduced by avoiding direct contact to materials overlying the patient, confirming standby mode or 25% light intensity, and maintaining the endoscope connected to the fiber optic cable at all times.

Intracranial application of near-infrared light in a hemi-parkinsonian rat model: the impact on behavior and cell survival.

OBJECT The authors of this study used a newly developed intracranial optical fiber device to deliver near-infrared light (NIr) to the midbrain of 6-hydroxydopamine (6-OHDA)-lesioned rats, a model of Parkinson's disease. The authors explored whether NIr had any impact on apomorphine-induced turning behavior and whether it was neuroprotective. METHODS Two NIr powers (333 nW and 0.16 mW), modes of delivery (pulse and continuous), and total doses (634 mJ and 304 J) were tested, together with the feasibility of a midbrain implant site, one considered for later use in primates. Following a striatal 6-OHDA injection, the NIr optical fiber device was implanted surgically into the midline midbrain area of Wistar rats. Animals were tested for apomorphine-induced rotations, and then, 23 days later, their brains were aldehyde fixed for routine immunohistochemical analysis. RESULTS The results showed that there was no evidence of tissue toxicity by NIr in the midbrain. After 6-OHDA lesion, regardless of mode of delivery or total dose, NIr reduced apomorphine-induced rotations at the stronger, but not at the weaker, power. The authors found that neuroprotection, as assessed by tyrosine hydroxylase expression in midbrain dopaminergic cells, could account for some, but not all, of the observed behavioral improvements; the groups that were associated with fewer rotations did not all necessarily have a greater number of surviving cells. There may have been other "symptomatic" elements contributing to behavioral improvements in these rats. CONCLUSIONS In summary, when delivered at the appropriate power, delivery mode, and dosage, NIr treatment provided both improved behavior and neuroprotection in 6-OHDA-lesioned rats.

Comparing the efficacy and safety of 365- and 550-µm laser fibers in semirigid ureteroscopic Ho:YAG lithotripsy.

PURPOSE: To compare the efficacy and safety of 365- and 550-µm Ho:YAG laser fiber in semirigid ureteroscopic lithotripsy and to identify parameters that may affect laser energy and time during the procedure. METHODS: A database of 111 patients who undergone a semirigid ureteroscopy (SRURS) for ureteral stone lithotripsy was analyzed. A 365-µm core fiber was used in 56 cases, and a multiple-uses 550-µm laser fiber was used in 55 cases. A standard 6.4 W protocol (8 Hz, 0.8 J/pulse) was used in all cases. The association between laser fiber diameter and several preoperative, intraoperative and postoperative parameters was evaluated. RESULTS: Mean stone burden was 54.1 ± 39.1 mm(2), and postoperative stone-free and complication rate was 100.0 and 16.2 %, respectively. The 550-µm laser fiber diameter was significantly associated with lower laser energy (p = 0.01), energy/mm(3) (p = 0.031), number of pulses (p = 0.012), laser time (p = 0.012) and laser time/mm(3) (p = 0.043), while it did not affect postoperative outcomes. The multivariate analysis showed that shorter procedure duration, smaller stone burden and the 550-µm laser fiber were all significant independent predictors for decreased laser energy consumption. CONCLUSION: The 550-µm laser fiber may decrease laser energy and time during SRURS lithotripsy with Ho:YAG laser compared to the 365 µm. Given its lower cost, it may represent the optimal choice for semirigid procedures.

Thermal injury secondary to laparoscopic fiber-optic cables.

BACKGROUND: Laparoscopy requires a reliable light source to provide adequate visualization. However, thermal energy is produced as a by-product from the optical cable. This study attempts to quantify the degree of possible thermal damage secondary to the fiber-optic light source. METHODS: Using a digital thermometer, temperature measurements were recorded at the tip of optical cables from five different light sources (Karl Storz, Inc., Tuttlingen, Germany). Temperature measurements were recorded with new and old bulbs. The tip of the cable was applied to surgical drapes and the time to charring was recorded. Subsequently, the tip of the optical cable was applied to a porcine model and tissue samples were obtained after varying amounts of time (5, 15, 30, 60, and 90 s). Sections of the damaged tissue were prepared for microscopic evaluation. Parameters for thermal injury included extent of epidermal, dermal, and subcutaneous fat damage and necrosis. The lateral extent and depth of injury were measured. RESULTS: The maximum temperature at the tip of the optical cable varied between 119.5 degrees C and 268.6 degrees C. When surgical drapes were exposed to the tip of the light source, the time to char was 3-6 s. The degree and volume of injury increased with longer exposure times, and significant injury was recorded with the optical cable 3 mm from the skin. CONCLUSIONS: This study demonstrates that the temperature at the tip of the optical light cord can induce extensive damage. The by-product of light, heat, can produce immediate superficial tissue necrosis that can extend into the subcutaneous fat even when the optical tip is not in direct contact with the skin. In addition, our study shows the variation in temperature that exists between light sources and bulb status. Overall, surgeons must realize and respect the potential complications associated with optical technology.

Fire/burn risk with electrosurgical devices and endoscopy fiberoptic cables.

PURPOSE: The purpose of the study was to systematically explore the fire and burn risk associated with fiberoptic cables and electrosurgical devices. MATERIALS AND METHODS: A 300-W light source was connected to a standard gray fiberoptic light cable. The end of the cable was either rested atop or buried within a cotton towel or polypropylene drape in the presence or absence of 100% oxygen for up to 10 minutes. A monopolar electrosurgical device set at 1 W, 10 W, or 30 W was tested on a cotton towel or polypropylene drape for a period of 30 seconds. All trials were repeated. RESULTS: Resting the light cable on top of the cotton towel or polypropylene drape with or without oxygen produced no result. Burying the end of the cable within the drape produced a hole in the drape within 15 seconds both with and without oxygen. Burying the end of the cable within the cotton towel produced a yellow discoloration after 2 minutes both with and without oxygen. The monopolar electrosurgical device set at 30 W burned immediately through the polypropylene drape, producing a skin burn. All other trials with monopolar electrocautery produced no result. No flame or fire was produced in any trial. CONCLUSIONS: Fiberoptic cables and electrosurgical generators represent a serious burn risk for surgical patients, with operating room drapes and towels affording only limited protection. Otolaryngologists should be keenly aware of the risks that these devices represent because our specialty uses them frequently.