Abstract:

High Intensity Focused Ultrasound (HIFU) has been shown to provide an effective method of hemostasis, in animal studies, for both solid organs and blood vessels (acoustic hemostasis). Moderate to profuse bleeding from major blood vessels, liver, and spleen, can be stopped within 1--2 min of HIFU application. The efficacy of acoustic hemostasis has been demonstrated using HIFU frequencies of 1--10 MHz, and acoustic intensities of 1000--5000 W/cm[sup 2]. Conventional B-mode ultrasound imaging and Doppler appear to provide a effective visualization, targeting, and monitoring methods when extracorporeal application, in case of internal bleeding, is desired. Both thermal and mechanical mechanisms of HIFU appear to be responsible for achieving hemostasis. The thermal mechanism, due to ultrasound absorption, raises the tissue temperature in excess of 70(degrees)C in less than a second, leading to shrinkage of the tissue and collapse of small blood vessels. The mechanical mechanism, due to cavitation activity, disrupts the tissue structure, leading to the occlusion of large blood vessels. Both mechanisms result in coagulative necrosis of tissue, and arrest of bleeding. Acoustic hemostasis may provide an effective method in surgery and prehospital settings for treating bleeding in trauma and elective surgery patients.