Chilled irrigation for control of temperature elevation during ureteroscopic laser lithotripsy: in vivo porcine model

Thermal Safety Boundaries for Laser Power and Irrigation Rate During Ureteroscopy: In Vivo Porcine Assessment With a Ho:YAG Laser

OBJECTIVE

To map thermal safety boundaries during ureteroscopy (URS) with laser activation in two in vivo porcine subjects to better understand the interplay between laser power, irrigation rate, and fluid temperature in the collecting system.

METHODS

URS was performed in two in vivo porcine subjects with a prototype ureteroscope containing a thermocouple at its tip. Up to 6 trials of 60 seconds laser activation were carried out at each selected power setting and irrigation rate. Thermal dose was calculated for each trial, and laser power-irrigation rate parameter pairs were categorized based on number of trials that exceeded a thermal dose of 120 equivalent minutes.

RESULTS

The collecting fluid temperature was increased with greater laser power and slower irrigation rate. In the first porcine subject, 25 W of laser power could safely be applied if irrigation was at least 15 mL/min, and 48 W with at least 30 mL/min. Intermediate values followed a linear curve between these bounds. For the second subject, where the calyx appeared larger, 15 W laser power required 9 mL/min irrigation, 48 W required 24 mL/min, and intermediate points also followed a near-linear curve.

CONCLUSION

This study validates previous bench research and provides a conceptual framework for selection of safe laser lithotripsy settings and irrigation rates during URS with laser lithotripsy. Additionally, it provides insight and guidance for future development of thermal mitigation strategies and devices.

Retrograde intra renal surgery and safety: pressure and temperature. A systematic review

PURPOSE OF REVIEW

Retrograde intra renal surgery (RIRS) with laser lithotripsy represents the gold-standard to treat renal stones up to 20 mm. Controlling intraoperative parameters such as intrarenal pressure (IRP) and temperature (IRT) is mandatory to avoid complications. This article reviews advances in IRP and IRT over the last 2 years.

RECENT FINDINGS

We conducted a PubMed/Embase search and reviewed publications that include temperature and pressure during RIRS. Thirty-four articles have been published which met the inclusion criteria. Regarding IRP, a consensus has emerged to control IRP during RIRS, in order to avoid (barotraumatic and septic) complications. Several monitoring devices are under evaluation but none of them are clinically approved for RIRS. Ureteral access sheath, low irrigation pressure and occupied working channel help to maintain a low IRP. Robotic systems and suction devices would improve IRP intraoperative management and monitoring. IRT determinants are the irrigation flow and laser settings. Low power settings(<20 W) with minimal irrigation flow (5-10 ml/min) are sufficient to maintain low IRT and allows continuous laser activation.

SUMMARY

Recent evidence suggests that IRP and IRT are closely related. IRP depends on inflow and outflow rates. Continuous monitoring would help to avoid surgical and infectious complications. IRT depends on the laser settings and the irrigation flow.

Temperature profiles during ureteroscopy with thulium fiber laser and holmium:YAG laser: Findings from a pre-clinical study

OBJECTIVE

The aim of this study was to investigate temperature profiles in both the renal pelvis and parenchyma during Thulium Fiber Laser (TFL) and Holmium:yttrium-aluminium-garnet (Ho:YAG) laser activation in an ex-vivo porcine model.

METHODS

Three porcine kidneys with intact renal pelvis and proximal ureters were used in the study. A temperature sensor was inserted through a nephrostomy tube into the renal pelvis and a second sensor was inserted directly into the renal parenchyma. Temperatures were recorded during continuous laser activation for 180 s, and for an additional 60 s after deactivation. TFL (150 μm and 200 μm) and Ho:YAG (270 μm) laser delivered power at settings of 2.4 W, 8 W, 20 W and 30 W.

RESULTS

Intrapelvic temperatures correlated directly to power settings. Higher power produced higher temperatures. For example, using a 150 μm fiber at 2.4 W resulted in a 2.6 °C rise from baseline (p = 0.008), whereas using the same fiber at 20 W produced a rise in temperature of 19.9 °C (p = 0.02). Larger laser fibers caused significantly higher temperatures compared to smaller fibers using equivalent power settings, e.g. mean temperature at 20 W using 150 μm was 39.6 °C compared to 44.9 °C using 200 μm, p < 0.001. There was a significant increase in parenchymal temperatures when applying 20 W and 30 W of laser power with the two larger fibers.

CONCLUSION

In this ex-vivo study, renal temperatures correlated directly to power settings. Higher power produced higher temperatures. Furthermore, larger laser fibers caused higher temperatures. These findings could help guide selection of safe power settings for ureteroscopic lithotripsy, but future clinical studies are needed for confirmation.

Establishment of mini-pig model of ureteral stricture by electrocoagulation under ureteroscopy

OBJECTIVE

To establish a mini-pig model of ureteral stricture by using electrocoagulation under ureteroscopy.

MATERIALS AND METHODS

Twelve female mini-pigs were included. Their ureters on one side and contralateral side were randomly divided into electrocoagulation and control groups, respectively. In the electrocoagulation group, the middle ureter was circumferentially electrocoagulated by using a self-made electrocoagulation device with the ureteroscope under direct vision, while the control group underwent ureteroscopy only without electrocoagulation. At 30 and 90 days after electrocoagulation, the glomerular filtration rate (GFR), formation of ureteral stricture, and histomorphological changes of ureteral tissues of each group were detected.

RESULTS

At 90 days after surgery, ureteroscopy and retrograde urography revealed ureteral stricture formation in the middle ureter in the electrocoagulation group. GFR was gradually decreased over time with prolonged washout half-time in the electrocoagulation group. A compensatory increase in GFR was observed in the control group. HE staining and Masson's Trichrome staining revealed fibroblast infiltration and fibrous tissue hyperplasia in the superficial muscular layers, and the muscular layers were arranged disorderly in the electrocoagulation group. Immunohistochemical staining showed accumulation and disorganization of ureteric epithelium in the narrow segment. In the control group, the epithelium was arranged neatly with normal structure.

CONCLUSION

A mini-pig model of ureteral stricture was successfully established using electrocoagulation under ureteroscopy. This method has the advantages of being simple to implement, having high accuracy and high success rate, which can provide an ideal animal model for studying ureteral stricture.