Infiltration of nanocarbon into the trachea during thyroidectomy surgery: case series and literature review.

Introduction: The presence of metastatic disease in the cervical lymph nodes can affect the recurrence and survival of patients with thyroid cancer. Parathyroid gland injury during surgery can result in hypoparathyroidism, particularly with total thyroidectomy. Injection of carbon nanoparticles into the thyroid will label draining lymph nodes and aid in the visualization of metastatic cervical lymph nodes during a radical operation, sparing accidental damage to the parathyroid glands. Although reported to be useful during surgery, the safety of nanocarbon particles has rarely been investigated, and adverse side effects need to be studied. Case presentation: The author describes five patients with thyroid cancer who had carbon secretions in the trachea or mucosa after carbon nanoparticles were injected into the thyroid. A patient with carbon secretions in the trachea mucosa recovered but had progressive dyspnoea. Surgical treatment was performed, and a mass was found in the trachea mucosa. After excluding all other possibilities, the author concluded that the mass was caused by nanocarbon suspension. Discussion: To the author's knowledge, there are no reports on nanocarbon suspension into the mucosa and no consensus has yet been reached on the precise injection site, depth, or dose for injecting carbon nanoparticles before thyroidectomy. Conclusion: The author suggests that the most appropriate injection depth of nanocarbon suspensions should be no more than 3 mm of the thyroid gland thickness to avoid deep injection into the trachea.