Description
Positioning and Anesthesia
Most thyroidectomies are performed under general anesthe-sia with endotracheal intubation. The patient is placed supine in a 20° reverse Trendelenburg position, with both arms tucked. The neck is extended by placing a beanbag or soft roll behind the scapulae and a foam ring under the head. This places the thyroid in a more anterior position. The head must be well-supported to prevent neck hyperextension and post-operative posterior neck pain.
The use of intraoperative nerve monitoring (IONM) for recurrent laryngeal nerve (RLN) function has become increasingly common in many endocrine surgical practices despite ongoing controversy over the true effectiveness of IONM in reducing the incidence of RLN injury and vocal cord palsy [ 8 ]. Proponents of IONM use cite its value in, among other things, tracing the anatomic course of nerves (particularly for challenging situations such as reoperations), more sensitively detecting injury in the intraoperative set-ting, and enabling the detection of vagal and superior laryn-geal nerve function. If the use of IONM is planned, an appropriate endotracheal tube with contact electrodes for the vocal cords is used, and grounding and return surface electrodes are applied per the individual manufacturer’s instructions. The remainder of this chapter will assume and describe the use of IONM during the relevant steps of the operation.
We routinely perform a bilateral superficial cervical anes-thetic block with 0.25 % bupivacaine, as this provides excel-lent anesthesia in the postoperative setting [ 9 ]. In addition, prior to surgical prep, we routinely perform our own intraop-erative neck ultrasound in order to (1) confirm the findings of the preoperative study, (2) identify any new findings, and (3) assess the overall anatomy of the gland to facilitate inci-sion placement and operative planning. The surgical area is prepared with 1 % iodine or chlorhexidine and sterilely draped.
Description of Procedure
In general, thyroid operations should be performed in a bloodless field so that vital structures can be identified. Bleeding obscures the normal color of the parathyroids and RLN, placing these important structures at greater risk for injury. If bleeding does occur, application of manual pressure is the preferred hemostatic maneuver; vessels should be clamped only if they are precisely identified, or shown to not be in close proximity to the RLN.
A centrally placed, 4–5 cm Kocher transverse incision is made typically 1 cm caudad to the cricoid cartilage, parallel-ing the normal skin lines of the neck (Fig. 1.1 ). The incision is extended through the platysma, and subplatysmal flaps are raised, first cephalad to the level of the thyroid cartilage and then caudad to the suprasternal notch. Five straight Kelly clamps placed on the dermis of each flap aid in retraction for this dissection.
In a cancer operation, dissection of the thyroid gland is generally begun on the side of the suspected tumor, since problems with the dissection on this side (e.g. concern for RLN injury) could allow the surgeon the option to per-form a less-than-total thyroidectomy on the contralateral side in order to avoid bilateral injury and resultant com-plications. One exception is the large bulky tumor, in which case the surgeon may choose to resect the contra-lateral side first in order to more easily mobilize the larger lobe.
The strap muscles are separated in the midline via an incision through the superficial layer of the deep cervical fascia starting at the suprasternal notch and extending cephalad to the thyroid cartilage. On the side of the sus-pected tumor, the more superficial sternohyoid is sepa-rated from the deeper sternothyroid muscle by blunt dissection, proceeding laterally until the ansa cervicalis is visible at the lateral border of the sternothyroid muscle. The sternothyroid is then dissected from the underlying thyroid capsule until the middle thyroid vein is encoun-tered laterally. The thyroid is retracted anteromedially, and the carotid sheath and strap muscles are retracted laterally. A peanut sponge can be used to facilitate retraction and exposure of the area posterolateral to the thyroid. The middle thyroid vein is optimally exposed for division at this time (Fig. 1.2 ). For those that use IONM, a pre-RLN dissec-tion vagus signal (denoted V1) is obtained by stimulating the vagus nerve which is typically located posterolateral to the carotid.
In the case of thyroid lobectomy, the isthmus is usually divided early in the dissection to facilitate mobilization. The isthmus is clamped and divided lateral to the midline, taking care to not leave residual tissue anterior to the trachea to minimize the chances of hypertrophy of the thyroid remnant. Energy sealing devices such as the Ligasure (Covidien, New Haven, CT) or Harmonic scalpel (Ethicon, Cincinnati, OH) are useful for dividing the thy-roid parenchyma in a hemostatic manner; alternatively, the isthmus can be divided with a scalpel between clamps and the thyroid remnant oversewn at the cut edge. The pyramidal lobe, present in 80 % of patients, drapes cepha-lad over the anterior midline just right or left of the cri-coid cartilage, and can extend as superiorly as the hyoid bone. It is dissected until it tapers into a fibrous band, divided, and ligated.