Endocrine Surgical Procedures Thyroid and Parathyroid Surgery

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Thyroid and parathyroid procedures can be considered together as they involve surgery in the same area of the neck, and the haemostatic techniques are generally the same. For convenience, they may be divided into preoperative, intra-operative, and postoperative measures.

Preoperative

All patients should stop aspirin, low molecular weight heparin, and similar medication likely to interfere with platelet function, at least one week beforehand. These simple measures will reduce the risk of postoperative ooze into the thyroid bed and prevent haematoma formation within the wound, which may take several weeks to resolve. After resolution of a haematoma, the scar may be tethered and unsightly and may need re-excision to improve the cosmetic appearance.

The patient should be positioned comfortably on the operating table with the neck extended, to enable good access to the anterior compartment of the neck. This is normally achieved by placing a pillow or bag of fluid under the shoulder blades and stabilising the head on a rubber ring or horseshoe. Care must be taken in patients with cervical bone disease. In patients with short stocky necks or large goitres, the chin can be elevated by tape strapping to the table and the shoulders can be depressed by gentle traction of the arms. Tape can also be used to strap down the breasts if this is contributing to a confined operating space. Good theatre lighting and the use of a bright white xenon operating headlamp is essential for adequate illumination and visualisation of important structures, particularly in the case of minimal access techniques. Prior to skin incision the table should be tilted to 15° head up, to reduce engorgement of the neck veins.

Endocrine anaesthesia plays a crucial role, particularly in the use of hypotensive techniques, to maintain the blood pressure at 20% below normal levels. This reduces intra-operative bleeding. Careful preoperative assessment is undertaken to ensure that there are no preexisting cardiovascular problems that may preclude such a technique.

Prior to incision of the skin, some surgeons infiltrate the area with local anaesthetic or adrenaline solution in an attempt to reduce bleeding. This is not favoured by the authors, however, as much of the bleeding at the skin edges will stop with direct pressure and more persistent bleeding points are best recognised and dealt with at the time with diathermy. It can also contribute to a false sense of security as it may take some time for the vasoconstrictive effects to wear off, risking subsequent bruising and formation of a wound haematoma.

Intra-operative

Most procedures are carried out through a traditional, Kocher collar incision placed a finger's breadth above the supraclavicular joint. Minimal access techniques tend to use a portion of this same incision.

After the skin incision has been made with the scalpel, the authors use a monopolar diathermy forceps with foot pedal operation to dissect carefully through subcutaneous fat and platysma, although this dissection can be carried out with scissors (Fig. 1). Care must be taken to avoid the anteriorjugular veins that course beneath the fascial layer. If they are damaged or are in the way of surgical access, they are best divided by clamping with artery forceps and tying with 2/0 absorbable ties. The key is to locate the bloodless plane between platysma and the fascial layer in front of the strap muscles to keep blood loss to a minimum.

A diamond shaped surgical field is created by mobilising the skin flaps superiorly as far as the thyroid cartilage and inferiorly to the suprasternal notch. It is maintained by a self-retaining Joll's retractor. The approach least likely to cause bleeding is between the strap muscles in the midline, which is achieved by incising the mid-line raphe with monopolar diathermy or scissors. The strap muscles,

Fig. 1 Raising of superior skin flap with monopolar diathermy forceps.

which may have become very atrophic as a result of a large goitre, may either be retracted or in the case of a very large gland, divided with diathermy. Care should be taken to avoid damaging a fairly constant vessel between the two strap muscle layers at the upper end of the field. The sternothyroid muscle is, then, dissected from the thyroid gland, ligating the middle thyroid vein with diathermy, ligaclips, or ties.

It is important to identify the recurrent laryngeal nerve before removing the thyroid or the parathyroid, finding it low in the neck and following its course upwards to the larynx. All the authors' patients undergo preoperative vocal cord checks and intra-operative recurrent laryngeal nerve monitoring. The authors use a Neurosign 100 nerve stimulator (The Magstim Company, Wales, UK) in conjunction with a laryngeal electrode attached to the endotracheal tube (Fig. 2). The electrode is not surgically invasive and is manufactured using a flexible polyester substrate with conductive ink tracks to measure the EMG activity. The laryngeal electrode is connected

Fig. 2 Neurosign 100 nerve stimulator and probe.

to the pre-amplifier pod and a bipolar stimulating probe used to deliver a high stimulation current (0.5 mA to 1 mA) to the recurrent laryngeal nerve. The authors feel that intra-operative nerve monitoring is a vital adjunct to safe neck surgery, and before any use of the diathermy or other haemostatic measure, the nerve should be located.

If both lobes of the thyroid are to be removed, then the larger lobe is generally removed first, making mobilisation of the other lobe easier. The superior pole of the thyroid, with superior thyroid artery and veins are dealt with first. Care is taken to avoid damage to the external branch of the superior laryngeal nerve. By staying on the thyroid and carefully ligating the terminal branches of the artery, haemostasis is easily achieved and safer than mass ligation.

Similarly, when mobilising the lower pole of the thyroid, the main trunk of the inferior thyroid artery is not ligated as this vessel supplies the parathyroids, but the terminal branches are found on the thyroid

Fig. 3 Ligaclip marking right upper parathyroid gland at tip of forceps (recurrent laryngeal nerve is also visible).

and ligated. This has the bonus of being much safer for the recurrent nerve as well. At this stage the parathyroids are sought and preserved, their position marked with a small ligaclip (Fig. 3). If enlarged, as in the case of a patient with hyperparathyroidism, they are removed for frozen section confirmation.

After the lobe has been fully mobilised, the vessels ligated and divided, and the recurrent laryngeal nerve and parathyroids identified, the thyroid is removed. The authors favour using monopolar diathermy alone to divide these small terminal branches of the main vessels and to dissect the lobe free from the pretracheal fascia. The key to this technique is to stay very close to the thyroid, with judicious use of a combination of diathermy and gentle traction, sometimes aided by the use of a stay suture.

If there is difficulty with bleeding, pressure with a pledget or dry swab for five minutes will normally control most small vessels. Diathermy in the thyroid bed can have grave consequences for the nerve, particularly if the view is somewhat obscured by haemorrhage, so ligaclipping or underrunning of bleeding points with an absorbable suture is better. Washout of the cavity created by lobec-tomy and, then, a dry swab left in place will control most oozing while the other side is removed.

In the case of parathyroid disease or thyroid cancer it may be necessary to perform a cervical thymectomy. This should be relatively simple to perform with few complications and virtually no bleeding, provided the appropriate technique is used. The thymus has a distinct structure to it compared with the surrounding fat and has a small vessel on its posterior surface, which must be cauterised or ligated. The thymus is separated from the thyroid by dividing the thyro-thymic ligament that is used to pull the thymus up from the mediastinum with sustained and steady traction (Fig. 4). Thymec-tomy should be virtually bloodless, but if there is any bleeding from the thymus bed, a dry swab left for five minutes will almost always control it.

It is essential that haemostasis is secured prior to closure of the wound. This is best achieved by identifying bleeding from vessels only when the venous pressure has been raised. The authors have the patient placed in a 15° head-down tilt position with the anaesthetist performing a Valsalva manoeuvre (expiration against a closed glottis) to 30 cm of water. This will often identify small vessel bleeding that would otherwise be missed and become the cause of a haematoma in the postoperative period when anaesthetic hypotensive effects have worn off or if the patient coughs after extubation.

If the patient has undergone subtotal resection, there may be troublesome bleeding from the thyroid remnant, which can be controlled by suturing to the pretracheal fascia with an absorbable suture. If the dissection has been extensive or a large vascular goitre has been removed, a suction drain may be used, but routine use is unnecessary. Drainage offers little relief from poor haemostasis, and it will not prevent a patient with significant bleeding in the neck from having to return to theatre.

Fig. 4 Excision of the thymus from the anterior mediastinum by gentle traction.

Closure of the wound comprises approximating the strap muscles with an absorbable suture, taking care not to inadvertently pierce one of the anterior jugular veins. In the authors' practice, the platysma is then closed, the wound infiltrated with bupivicaine with 1 in 200,000 adrenaline, and the skin closed with interrupted 4/0 nylon.

Postoperative

The wound is dressed with steristrips and a low allergenic, non-adherent dressing. The authors favour the application of a mild pressure dressing around the neck for 24 hours, to diminish oozing. All patients are encouraged to sit up to reduce venous engorgement, and drains, if present, are usually removable within 48 hours of surgery.

Sternal split and mediastinal exploration

Sternotomy may be indicated for the removal of a large retrosternal goitre or mediastinal parathyroid or the excision of a thymoma in a patient with myasthenia gravis. Meticulous planning is undertaken preoperatively to localise tumours so that the minimum amount of time is spent exploring the chest. This also reduces trauma and potential blood loss. It is usually not necessary to split the whole sternum, but only the manubrium (Fig. 5), which gives adequate access for exploring the aorto-pulmonary window in the case of ectopic parathyroid excision.

During the procedure diathermy is usually adequate for haemostasis, but the cut edges of the sternum can produce troublesome bleeding. The authors' practice is to use bone wax for control. It is a sterile mixture containing beeswax and paraffin and achieves local haemostasis by acting as a mechanical barrier, tamponading small vascular channels in the bone.

Fig. 5 Manubrial sternal split revealing an ectopic parathyroid gland (at tip of arrow).

Bone wax has no biochemical action and is minimally resorbable. This means it may have possible adverse effects on osteogenesis and can produce mild inflammatory reactions. It acts as a mechanical barrier, therefore, it may prevent clearing of bacteria from infected sites. This is, however, rarely a problem in elective endocrine surgery.27 A review by Milano et al.28 found no evidence of bone wax causing mediastinitis and noted that poor haemostasis was, in fact, the major contributor to a higher risk of infection.

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