Evaluating the introduction of intraoperative neuromonitoring of the recurrent laryngeal nerve in thyroid and parathyroid surgery

Training in intraoperative neuromonitoring of recurrent laryngeal nerves reduces the risk of their injury during thyroid surgery

INTRODUCTION

Even though incidence of recurrent laryngeal nerve palsy (RLNP) is low, it affects importantly the quality of life of patients and remains one of main medicolegal litigation problems in surgery. Intraoperative neuromonitoring (IONM) has become widely accepted tool helping in recurrent laryngeal nerve identification, however no clear association of IONM with RLNP rate has been demonstrated. The aim of our study was to assess whether training in IONM influences rates of RNLP after thyroid surgery as an independent factor.

MATERIAL AND METHODS

We analysed retrospectively 1235 patients who underwent thyroidectomy at the 1st Department of General and Endocrine Surgery, Medical University of Bialystok. Possible risk factors for RLNP were evaluated: application or not of IONM, the extent of surgery or thyroid pathology in correlation with surgeons' experience in IONM (trained or untrained).

RESULTS

There were 2351 nerves at risk (NAR) and 39 RNLP were diagnosed after thyroid surgery (1.66%). Surgeons trained in IONM performed 52.2% of all operations (1200 NAR) with 7 RLNP (0.58%), whereas not-trained had 32 RLNP for 1151 NAR (2.8%; p < 0.001). After 182 thyroidectomies (357 NAR) guided by IONM (14.7%) 3 RLNP were observed (0.84%) vs. 36 palsies per 1994 NAR without IONM (1.81%; p = 0.189). The highest danger of RLNP was reported after reoperations and the lowest after subtotal thyroidectomies. We found no association between thyroid pathology and RLNP rate.

CONCLUSIONS

According to our study training in IONM decreases chances of RLNP especially during total or near total thyroidectomy.

[Sequential method for determining the maximum dose of mivacurium continuously infused for intraoperative neuromonitoring in thyroid surgery]

OBJECTIVE

To determine the maximum dose of continuously infused mivacurium for intraoperative neuromonitoring and observe its adverse effects in thyroid surgery.

METHODS

Twenty-eight patients undergoing thyroid surgery with intraoperative neuromonitoring received continuous infusion of mivacurium at the initial rate of 5.43 μg?kg^-1?min^-1, and the infusion rate for the next patient was adjusted based on the response of the previous patient according to the results of neurological monitoring. The depth of anesthesia was maintained with sevoflurane and remifentanil during the surgery. The LD50 and 95% CI of mivacurium were calculated using Brownlee's up-and-down sequential method.

RESULTS

The LD50 of continuously infused mivacurium was 8.94 μg?kg^-1?min^-1 (95% CI: 8.89- 8.99 μg?kg^-1?min^-1) during thyroid surgery, which did not affect neurological function monitoring. Transient chest skin redness occurred after induction in 9 patients (32.1%). None of the patients experienced intubation difficulties or showed intraoperative body motions during the surgery.

CONCLUSIONS

In patients undergoing thyroid surgery under anesthesia maintained by inhalation and intravenous infusion, the LD50 of mivacurium was 8.94 μg?kg^-1?min^-1 (95% CI: 8.89-8.99 μg?kg^-1?min^-1) for continuous infusion, which does not cause serious adverse effects during the operation.