is true vocal-fold paresis or paralysis that presents with subacute postoperative hoarseness or breathiness. Surgeon experience, extent of resection, presence of malignancy or substernal goiter, and re- operative surgery are all factors associated with higher rates of RLN injury. In an effort to increase the safety of thyroid surgery and better preservation of the RLN, an increasing number of surgeons are employing LNM. LNM is accomplished by using either a postcricoid surface electrode plate or an endotracheal tube equipped with electrodes (see figure 1) that are recording the electrical potentials of the thyroarytenoid muscles (vocalis muscles). Electrodes are connected to the monitor, so when deliberate or inadvertent stimulation of the RLN occurs (i.e. by touch with a probe or mechanical trauma such as dissection), a prompt audible signal accompanies a graphical display of the electrical activity. Today, most commonly employed are NIM-2 (Medtronic-ENT) and the Neurosign 100 (Inomed) systems. Because of the potentially devastating
consequences of a rapidly expanding hematoma, the precise and absolute hemostasis is crucial in thyroid surgery. Several technological innovations today allow surgeons to achieve a better balance between hemostasis and tissue preservation. Harmonic scalpel (HS)
«Minimally invasive video-assisted thyroidectomy was developed to minimize postoperative pain, improve cosmetic results, and potentially reduce the length of hospital stay»
employs mechanical vibration for simultaneous coagulation and tissue cutting (figure 2). The instrument was initially used in abdominal surgery, and has since been successfully employed in various surgical specialties. HS contains a generator producing acoustic waves at a frequency of 55000 Hz. The waves are transferred to the active blade of the instrument, vibrating harmoniously at the same frequency. In addition to the direct cutting action of the vibrating blade, ultrasound waves cause abrupt changes in the tissue inner pressures that result in cavitation fragmentation and additional cutting effect. The coagulation effect occurs due to the interruption of tertiary hydrogen bonds, leading to tissue protein denaturation, in contrast to electrical or laser
coagulation, where the generated and transmitted heat (characteristically ranging from 150°C to 400°C) entails extreme intracellular temperature elevation and intracellular gas explosion. Working with HS is associated with a considerably lower production of thermal energy (up to 80°C), thus causing significantly less thermal damage to the adjacent tissue. In addition to significantly lower intraoperative blood loss, the operative time is markedly reduced with the use of HS. The advents of endoscopic instruments
have revolutionized minimally invasive procedures in many surgical disciplines, including the surgery of the thyroid gland. Currently, the most commonly performed endoscopic procedure is minimally invasive video-assisted thyroidectomy (MIVAT), introduced at the end of 1990s by Prof. Paolo Miccoli. MIVAT approach was developed to minimize postoperative pain, improve cosmetic results, and potentially reduce the length of hospital stay. This approach carries the advantages of superior visualization by endoscopic magnification, and more rapid wound healing due to reduced dissection and reduced tissue edema (figure 3). Patients benefit from a smaller incision (15-20 mm in length), while complication rates are equivalent to standard approaches. Disadvantage of MIVAT is that procedure is applicable for only 10-15% of thyroidectomies; most commonly for thyroid nodules within specific size limits and for low-stage papillary carcinoma. Best candidates for MIVAT are patients with thyroid nodule size less than 30 mm in diameter; stage T1 of papillary carcinoma; or ones with total thyroid volume less than 50 mL.
CONCLUSION Technological advancements over the last decade have led to more precise and safer thyroid surgery and better hemostasis. Owing to novel technologies, many thyroidectomies today can be performed on an outpatient basis. Future evolution of surgical robotics may further facilitate reducing surgical times, with improved dexterity compared with conventional endoscopic instrumentation. ■
AH
REFERENCES References available on request (
magazine@informa.com)
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