Hodgson introduced ultrasonic dissector for liver surgery in 1984.31 This is a hand-held instrument consisting of a titanium tip that oscillates at an ultrasonic frequency of 25,000 vibrations per second. When placed against tissue, fat and hepatocytes are destroyed by a cavitational effect based on their higher water content. In contrast, vessels, ducts, and nerves, which contain fibrous tissue with more collagen and less water content, are left relatively undamaged.32 The instrument also has an irrigation port to cool the tip and a suction port to aspirate the irrigant and fragmented tissue. In performing the dissection of liver tissue, the fibrous capsule of the liver requires division by electrocautery as the ultrasonic dissector is not efficient in dividing these tissues. After the parenchyma is exposed, the ultrasonic dissector is employed to destroy the parenchymal tissues and leave vessels and ducts to be electively divided. For small vessels and ducts, electrocautery is sufficient. For larger vessels and ducts, ligation using ties or clips should be employed. The use of the ultrasonic dissector has had a significant impact on patient morbidity and mortality, dramatically reducing blood loss, especially when used in conjunction with intra-operative ultrasound (IOUS).33 A new offshoot of the ultrasonic dissector is the ultrasonically activated coagulating (harmonic) scalpel, which is described below.
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