Ultrasound thrombolysis in hemodialysis access: In vitro investigation

Purpose: To evaluate the effectiveness of ultrasound thrombolysis in occlud ed hemodialysis access shunts using an in vitro model. Methods: Thrombosed hemodialysis accesses were simulated by clotted bovine blood in a flow model (silicone tubing; inner diameters 4, 6, and 9 mm). Af ter retrograde and antegrade sheath placement (7 Fr), mechanical thrombolys is was performed using an ultrasound probe (Acolysis, Angiosonics, Morrisvi lle, NC, USA). The tip of the device measured 2.2 mm in diameter. During so nication, the catheter was moved slowly back and forth using an over-the-wi re system. Thirty complete occlusions [tubing diameters 4 mm (n = 12), 6 mm (n = 12), 9 mm (n = 6)] were treated. Initial thrombus weights were 3.5 (/- 0.76) g, 7.7 (+/- 1.74) g, and 19.4 (+/- 2.27) g for the three diameters . Maximum sonication time was 15 min for each probe. Results: With this device, we were able to restore a continuous lumen in al l 12 occluded 4 similar to mm silicone tubes. No wall-adherent thrombi rema ined after sonication for 3.5-9.6 min. In hemodialysis access models with d iameters of 6 mm, thrombus fragments persisted in 25% (3/12 accesses). Thes e were located in the medial portion of the access loop and near to the pun cture sites. However, flow was re-established after 5.0-13.0 min of treatme nt in all settings. Mechanical dissolution of thrombus material failed in f ive of six access models with diameters of 9 mm, even though ultrasound ene rgy was applied for the maximum of 15 min. Conclusion: In a clotted hemodialysis shunt model, successful ultrasound th rombolysis was limited to small access diameters and small amounts of throm bus.