Radiofrequency ablation: Effect of pharmacologic modulation of hepatic and renal blood flow on coagulation diameter in a VX2 tumor model

PURPOSE: To determine whether pharmacologic agents can be used to modulate blood flow in hepatic and renal tumors sufficiently to alter the extent of radiofrequency (RF)-induced coagulation. MATERIALS AND METHODS: VX2 tumors (8-15 mm) were implanted in the liver (n = 25) or kidney (n = 8) of 33 New Zealand White rabbits. RF was applied to tumors for 6 minutes with use of conventional electrodes (125 mA +/- 35; 90 degrees C +/- 21 degrees C tip temperature). In the hepatic model, blood flow was modulated with use of halothane, epinephrine, or arsenic trioxide (2-6 mg/kg). Laser Doppler flowmetry was used to quantify changes in hepatic blood flow. Correlation of blood flow with induced coagulation diameter was performed. RF ablation was then performed in a renal model with and without arsenic trioxide. RESULTS: For liver tumors, halothane and arsenic trioxide reduced blood flow to 40.3 % +/- 17.8 % and 29 % +/- 15 % of normal, respectively, whereas epinephrine increased blood flow to 207.8 % +/- 97.9 %. Correlation of blood flow to coagulation diameter was demonstrated (R-2 = 0.40). Coagulation measured 7 mm I with epinephrine, 10 mm 1 with normal blood flow, 12 mm 3 with halothane, and 13 mm 3 with arsenic trioxide (P < .04 compared with controls). In the renal model, arsenic trioxide decreased blood flow (44 % +/- 16 %) and increased coagulation diameter (10.9 mm +/- 1) compared with controls (84 % 11 % and 7.6 mm 1; P < .01, both comparisons). CONCLUSIONS: RF-induced coagulation necrosis in rabbit hepatic and renal tumors is affected by tumor blood flow. Pharmacologic modulation of tumor blood flow may provide a noninvasive way to decrease blood flow during thermally mediated ablation therapy, potentially enabling the creation of larger zones of coagulation necrosis.