2.1. Injuries to the recurrent laryngeal nerve (“RLN palsy”)
Incidence
- 1%–2%, in repeat surgery 2%–8%.
- Patients with thyroid cancer run the highest risk of permanent RLN paralysis.
Cause
- Usually intraoperative strain and/or compression of the recurrent laryngeal nerve (RLN)
- Rarely broken continuity of the nerve
- Also: Pressure trauma due to postoperative bleeding or endotracheal intubation
Endotracheal intubation
The nerve may be injured not only during intraoperative maneuvers but also by the endotracheal intubation (intubation related RLN paralysis rate: temporary 1.4%, permanent 0.5%). That this is indeed possible is demonstrated by postoperative RLN paralysis in patients who had undergone surgical procedures other than in the neck. Possible reasons: Intralaryngeal submucous branching of the RLN, wrong cuff position (e.g., within the larynx), extubation with blocked cuff. Thus, it is recommended to check the cuff for symmetry before intubation, ventilate it occasionally, perform regular pressure checks especially in long procedures, and position the patient quite carefully with indwelling tube to prevent any pressure injury to the RLN coursing adjacent to the tracheal wall.
Other causes of intubation related hoarseness with RLN injury It may be “regular” postoperative hoarseness after general anesthesia (present in about 30% of all such patients) or due to intubation related lesions such as mucosal injury, hematoma, injury to the vocal cords or dislocation of an arytenoid cartilage.
Outcome
- Dysphonia, dysphagia and dyspnea
- Bilateral RLN paralysis often necessitates tracheotomy.
Prophylaxis
The risk of iatrogenic injury to the RLN may be lessened by two complementing measures.
- Consistent exposure of the RLN, particularly in total lobectomy: the gold standard is visual identification
- Intraoperative neuromonitoring (IONM): electromyographic visualization of the function of the RLN and vagus nerve
The following also helps to spare the RLN and parathyroids:
- So-called microdissection technique using optical instruments (surgical loupes).
- Employing gentle hemostasis (bipolar coagulation, vessel clips, vessel sealing, ultrasound dissection)
This link provides you with basic information on intraoperative neuromonitoring: IONM
Preferred locations of RLN injury include:
- Superior pole: Bulk ligation in locations where the RLN enters the cricopharyngeal part of the inferior constrictor muscle of the pharynx.
- Inferior pole: When briskly dislodging the inferior pole with the finger
Superior laryngeal nerve
- The external branch of the superior laryngeal nerve crosses the pole vessels close to the superior pole, either anteriorly or posteriorly or may even pass through them.
- A lesion of this branch may result in dysphonia with impaired vocal potential such as decreased vocal range and quicker voice fatigue.
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- Allowances for the special anatomy should be made by dissecting gently and close to the superior pole.
- Since the data reported to date do not support routine exposure of this nerval branch, the current guidelines no longer advocate this.
2.2. Secondary bleeding
Incidence
- 0.3%–5%
- Most secondary bleeding develops within the first 12h–24h after surgery.
- Due to the increased intrathoracic pressure the recovery phase after extubation is the most vulnerable period.
- The extent of the bleeding varies and ranges from ecchymosis to hematomas under the platysma and life-threatening hemorrhage with asphyxia
In thyroid surgery secondary bleeding is the only complication typical of this procedure which may result in a potentially fatal situation. In arterial hemorrhage the blood enters the cervical compartment under high pressure and may cause compression, swelling, dyspnea requiring intubation, and asystole due to pressure on the vagus nerve.
- Asymptomatic bleeding without noteworthy increase in cervical circumference may need no more than watchful waiting with closely monitored follow-up, being ready for appropriate action at any time
- Caution is advised in slowly developing hematoma with increasing circumference of the neck. It may result in mucosal swelling in the larynx and trachea which could impair endotracheal intubation so much that emergency tracheotomy is required.
- Acute secondary arterial hemorrhage calls for immediate surgical action.
This requires early diagnosis and prompt bold action, thereby minimizing morbidity It is recommended to institute a secondary bleeding management protocol whose details you will find here Notfallplan – Nachblutung nach Schilddrüseneingriffen [Emergency protocol – Secondary bleeding after thyroid surgery]
2.3. Hypoparathyroidism
Incidence
- Transient (7.3%–8.3%)
- Permanent (1.5%–1.7%)
- Rate of permanent hypocalcemia increased in thyroid cancer (up to 4%) and Graves disease (up to 2%)
Cause
- Iatrogenic resection of one or more parathyroids
- Blood flow impaired by injury to the vessels supplying the parathyroids
- The risk of permanent hypoparathyroidism increases significantly if less than 2 or 3 parathyroids are preserved
Information on the management of postoperative hypoparathyroidism is detailed here: Postoperative hyperparathyroidism
Prophylaxis
- Safe identification of the parathyroids by targeted exposure
- Not just generally ruling out unrecognized parathyroid tissue in situand on the specimen
- Autotransplant parathyroids with impaired blood supply (morcellate into 1mm3cubes and autotransplant into a pocket in the ipsilateral sternocleidomastoid muscle; do not forget to document this step!)
- Since the parathyroids are primarily supplied via the inferior thyroid artery, the latter should only be ligated close to the thyroid gland and after definite identification of the recurrent laryngeal nerve.
2.4. Infections
Incidence
- 0.2%-1.4 %
- Most wound infections manifest as hematomas with secondary infection; abscess and fistula formation have been reported
- Infections usually do not present major problems when good wound management is instituted; blood borne spread and a septic course are rare
- One significant but rare infection is mediastinitis which may develop after thyroid surgery with transsternal access.