Keywords

1 Energy Devices

Thyroid diseases are the most common endocrine disorders [1]. The thyroid is a richly vascularized organ and the achievement of hemostasis during surgery is an issue of great interest to the surgeon. Hemorrhage makes the surgical field dangerous, increasing the risk of damage to adjacent anatomical structures, such as the recurrent laryngeal nerve, the parathyroid glands and the esophagus [2]. Additionally, postoperative bleeding can cause hematoma or seroma, with upper airway obstruction and subsequent hypoxic brain damage. The techniques used for the management of hemostasis are many and include standard vessel ligation and section, monopolar or bipolar electrocautery and the use of monopolar, bipolar, ultrasound and mixed-energy devices. The temperatures generated during electrocautery are high (150–400 °C) and they are responsible for severe damage to adjacent tissues. Electrical and ultrasound energy are generally used in numerous surgical procedures, including thyroid surgery, and they have demonstrated their absolute safety and efficacy, as these devices stop working once the coagulum has already formed, limiting the possibility of overheating. Widely discussed in the literature is the issue of the temperature in the tissue, which decreases from the instrument tips to the periphery, and the damage due to the lateral spread of heat; safety margins are fixed between 3 and 5 mm from healthy tissue with a required cooling time of the tool [3,4,5]. In addition, various prospective randomized studies have shown how the use of these devices can shorten operating times and reduce the incidence of postoperative complications [6]. Many devices have been proposed. One of them relies on an ultrasonic coagulating shear able to cut and coagulate by using temperatures that are lower than those delivered by conventional electrosurgical equipment, performing denaturation of proteins and subsequent coaptation, closing the vessel and avoiding bleeding. The design of this hand-operated shear device reproduces the familiar “Kelly clamp” shape, with very thin and delicate tips. The instrument allows the surgeon to easily dissect, as well as clean and cut vessels in tight spaces, lowering the rate of complications such as postoperative transient hypocalcemia, and decreasing operative time and the need for hemostatic agents and postoperative drainage [7]. Another such device consists of an energy generator and a manual tool produced in different shapes and sizes. This device simultaneously uses both the pressure exerted on the vessel by the tool jaws and bipolar electrical energy, which degrades the collagen and elastin making up the vessel wall, reaching temperatures above 42 °C. This system coagulates vessels up to 7 mm in diameter without causing the formation of an intravessel thrombus. It has been shown that the vessels, thus coagulated, resist higher than normal systolic pressures [8]. A newer device that integrates bipolar energy and ultrasound energy has recently been developed, which can seal and cut vessels up to 7 mm in diameter with little thermal diffusion. In previous studies, this device was shown to have a shorter coagulation and resection time than devices using monopolar or bipolar electrical current in a porcine model [9].

The complication rate of these energy devices is superimposable in terms of transient RLN palsy and transient hypocalcemia, as a result of the similar thermal injury caused to the neighboring tissues. Moreover, in the literature sutureless thyroidectomy is widely discussed as being safer and faster than typical surgery, allowing a shorter anesthesia with a low risk of postoperative complications [10].

2 Hemostatic Agents

Surgical treatment of thyroid gland diseases is associated with the possibility of severe postoperative complications. Bleeding after a thyroidectomy is a severe complication, and reoperation due to bleeding may entail further complications, including death [11]. The reported incidence of bleeding after thyroid surgery varies from 0% to 4.2% [12, 13]. In highly experienced departments the rate usually does not exceed 1% [14, 15]. Blood flow through the thyroid gland is high, as the gland has one of the highest blood flow rates in the human body. Hemorrhage in general surgery can be classified into three main categories: primary bleeding, which occurs within the intraoperative period and should be resolved during the operation; reactive bleeding, which may occur within 24 hours of operation and in most cases is caused by a ligature which slips off or by an unacknowledged vessel that starts to bleed once the blood pressure falls back into a normal range postoperatively [16]; secondary bleeding, which occurs 7–10 days postoperatively and is often due to erosion of a vessel from a spreading infection [17].

Standardization of the capsular dissection technique and precise ligation of the arterial supply by enabling meticulous dissection of the thyroid gland have decreased the morbidity and mortality associated with thyroid surgery to less than 1%. Nevertheless, postoperative hematoma remains an uncommon but potentially life-threatening complication of thyroid surgery. The conventional techniques for hemostasis are suture ligation, electrocautery, or surgical clips. Adjacent anatomical structures, such as the RLN and the parathyroid glands, could be inadvertently injured because of difficulties during bleeding control [18].

Over the last two decades, a number of adjuvant hemostatic agents have been developed for hemostasis in thyroid surgery [19]. Hemostatic agents can be divided according to the nature of the material (animal, human, plant and synthetic derivatives), the mechanism of action, and the class to which they belong. According to these criteria, some hemostatic agents belong to the class of drugs, while others were registered as medical devices. These agents have been broadly classified into three groups: topical hemostats, which cause blood to clot at a bleeding surface; sealants, which prevent leakage from tissues including vessels: and adhesives, which bond tissues [20]. Topical hemostats are the most used and typically consist of a mechanical face which promotes clot formation with either thrombin or fibrinogen, used separately or in combination. The most common hemostatic agent in thyroid surgery consists of soft, thin, pliable, flexible pads of collagen derived from bovine dermis, coated with pentaerythritol polyethylene glycol ether tetra-succinimide glutarate (NHS-PEG); it is a surgical sealant indicated for procedures in which control of bleeding or leakage of air or other body fluids is ineffective by conventional surgical techniques. Another very common device is a sterile, fibrous, resorbable hemostat made from pure natural cotton using controlled oxidation technology, which provides a fast and effective local hemostasis, usually within 2 minutes. Other studies support the use of a combination of bovine-derived gelatin matrix and human-derived thrombin as a first-line hemostatic agent in thyroidectomy [21]. It is indicated in surgical procedures as an adjunct to hemostasis, when control of bleeding by ligature or conventional procedures is ineffective. Moreover, some authors suggest that the increased cost of using this hemostatic agent is offset by the reduced operating times and shorter hospital stays [19]. A synthetic oxidized regenerated cellulose polymer has yielded better results in operating time and duration of drain use than a hemostatic agent composed of a layer of soft, lightweight oxidized regenerated cellulose [22].

A recent meta-analysis evaluated the safety of hemostatic agents in comparison to conventional techniques for hemostasis [18]. While hemostatic agents did not significantly decrease the incidence of complications such as hematomas, seromas, infection, RLN injury or hypoparathyroidism, there was a significant decrease in operative time, drain output and hospital stay through the use of hemostatic agents. Additionally, shorter drainage time may decrease the amount of postoperative discomfort. In conclusion, hemostatic agents appear to be useful tools for achieving hemostasis in thyroidectomies, and they have also been shown to decrease drain output and length of hospital stay following thyroidectomy.

3 Optical Magnification

The use of optical magnification has many potentialities in thyroid surgery. Binocular loupes, endoscopes, exoscopes and microscopes are used for magnification, allowing a detailed visualization of anatomy and tissues, getting also easier and more precise use of surgical instruments, achievement of hemostasis, and placement of sutures. Loupes reach a magnification of 2.5× to 5×, microscopes 6× to 40×, endoscopes and exoscopes 12× to 30×. Despite the many advantages, several surgeons do not yet use magnification because of the increased surgical time, the impractical use of some devices, lens clouding during surgery, and the limitation of the operating field [23].

Magnification can support traditional thyroid surgery in preventing the most common complications: injury to the RLN caused by traction, ligation, section, diathermy injury, clamping and ischemia; injury to the superior laryngeal nerve (SLN); injury to the parathyroid glands (PG); bleeding. Additionally, illumination of the operative field is increased by the led light worn by the operator. There are different routine uses of loupes in thyroid surgery and different authors have suggested using loupe magnification powers of 2.5×, 3×, 4.5×, or from 4× to 10× [24,25,26,27]. Use of the microscope is relatively quick to learn and has ergonomic benefits, as it reduces musculoskeletal risk and allows the operator to keep an upright posture during the surgery. The microscope also allows for video recording, which is very important for teaching and medico-legal purposes [26]. Loupe magnification significantly reduces temporary complications, such as hypocalcemia and dysphonia, by helping to identify the PGs and the RLN, without increasing the operating time [27].

A recent study shows that the combined use of loupes and harmonic scalpel led to an important reduction in operating time, by enabling the surgeon to operate in a bloodless field, with a consequent improvement of surgical outcomes [28]. Endoscopic magnification can be used as a routine dissection method to identify and preserve the external branch of the SLN (EBSLN), for preservation of voice quality in patients undergoing thyroid surgery: this “hybrid technique” involves only one additional step during traditional thyroid surgery, for identification of the EBSLN and its variants [29]. The Karl Storz 4 K 3D VITOM exoscope (Karl Storz SE & Co. KG, Germany) confers superior operative visualization in thyroid surgery: it consists of a 4 K endoscope and a 300 W xenon fiberoptic light source; the camera has 8–30× magnification allowing for a working distance of 20–50 mm; the operating team must wear 3D polarized glasses. The technology is similar to an endoscope, but it is external to the patient and offers ergonomic benefits and a similar visualization quality to that of robotic surgery without the loss of haptic feedback, as well as facilitating surgical training [24].

No doubt, mention should also be made of the minimally invasive techniques of thyroid surgery for their use of video magnification: minimally invasive video-assisted thyroidectomy (MIVAT), transoral endoscopic thyroidectomy (TOET), TOET with vestibular approach (TOETVA), and robot-assisted transaxillary thyroidectomy (RATT) [29].

Magnification offers many benefits, but it is important to remember that the surgeon’s experience is fundamental in thyroid surgery, and similarly also the magnifications technique requires experience [30].