Continuous versus pulsed microwave ablation in the liver: any difference in intraoperative pain scores?

Background This study prospectively compared intraoperative pain scores during percutaneous microwave ablation of the liver in patients randomized between continuous and pulsed energy delivery algorithms. Methods During a 12-month period, 20 patients who underwent microwave liver ablation were prospectively randomized between 2 different energy delivery modes: continuous mode (CM, n=10) and pulsed mode (PM, n=10). All ablation sessions were performed using the same microwave ablation platform under computed tomographic guidance and intravenous analgesia. Within 30 min post ablation, all patients completed a questionnaire assigning a numeric pain intensity score from 0 (no pain) to 10. Results Mean pain scores were 8.17 +/- 1.850 in the CM group and 4.50 +/- 1.567 in the PM group, with a statistically significant difference of 3.667 +/- 2.807 pain units (P=0.001). The mean procedure time was 53.5 +/- 20.90 min in the PM group vs. 58.5 +/- 17.44 min in the CM group (P=0.279). The mean size of the lesions was 2.81 +/- 0.95 cm in the PM group and 2.81 +/- 0.85 cm in the CM group (P=0.984). On a per-lesion basis, technical success was achieved in all evaluable tumors in both groups. No difference was noted in the local tumor control on the 6-month imaging evaluation. No complications were observed in the CM arm, while small perihepatic hemorrhagic fluid collections were reported in the PM group. Conclusions Both algorithms for microwave energy delivery have comparable treatment effects in terms of 6-month local tumor control for liver lesions <3 cm in diameter. PM treatments compared to CM appear to induce significantly less pain in patients undergoing percutaneous liver ablation under intravenous analgesia.