Laser Lithotripsy Induces Dose-Dependent Temperature Elevation During Retrograde Intrarenal Surgery

Real-time assessment of calyceal and tissue temperatures during laser lithotripsy.

Patients eligible for endoscopic combined intrarenal surgery were assigned to Soltive 60 W SuperPulsed thulium fiber laser (TFL; Olympus, Inc.) or holmium:YAG (Ho:YAG; Lumenis Pulse™ 120H) based on availability. After translocation of stones, a 1.5-mm multipoint thermal sensor needle measuring temperatures 5, 15, 25, and 35 mm from the tip was placed percutaneously with ultrasound guidance. The 5-mm mark recorded calyceal fluid temperature and the others parenchymal temperatures for 2 minutes during fragmentation (1 J/2 Hz TFL and 0.5 J/5 Hz Ho:YAG, 2-2.5 W), dusting (0.3 J/50 Hz, 15 W), and pop-dusting (0.5 J/80 Hz, 40 W). If tissue temperature exceeded 43°C, lasering was paused. After measurements, tract dilation and percutaneous nephrolithotomy were performed. Categorical data were compared using chi-square or Fisher's exact tests and continuous variables via t-tests.

The 20 patients (10 TFL and 10 Ho:YAG) had similar baseline characteristics. During fragmentation, calyceal (T_calyx) and parenchymal (T_tissue) temperatures never exceeded 41°C. During dusting, T_calyx exceeded 43°C in four patients for each laser and T_tissue exceeded 43°C in one Ho:YAG patient (49°C after 60 seconds). Maximum calyceal temperature (T_max) in TFL and Ho:YAG patients was 51°C and 56°C (p = 0.18), respectively. During pop-dusting, T_calyx exceeded 43°C in 10 TFL and 8 Ho:YAG patients, and average maximum temperature (avgT_max) was significantly higher for TFL (52.9°C vs 45.1°C, p = 0.027). The tissue T_max was 47°C and 49°C (p = 0.96), respectively, with 43°C exceeded in three TFL and three Ho:YAG patients.

During high-powered lasering, temperatures can exceed 43°C in as little as 15 seconds. This is concerning since temperatures >43°C may be associated with permanent tissue injury.