I. Causes of surgical operation (1) The upper and lower thyroid pole vessels and the middle vein ligature line are dislodged resulting in hemorrhage. The superior thyroid artery originates from the external carotid artery, and the inferior artery originates from the thyroid neck stem, which has high arterial pressure; the middle thyroid vein flows directly back to the internal jugular vein. Once these vascular ligatures are dislodged, they can easily cause massive bleeding and endanger the patient’s life. (2) Severe bleeding from the residual surface of the thyroid gland after partial or subtotal thyroidectomy. This is mostly due to the lack of tight sutures or poorly knotted or loose threads on the residual surface of the thyroid gland. (3) Bleeding of the vessels at the laryngeal entry of the recurrent laryngeal nerve or reopening of the small vessels that were hemostatic with energy instruments. The laryngeal nerve is often accompanied by some vascular rings at the laryngeal entry, which are not easy to ligate because of the proximity of the laryngeal nerve. In recent years, energy instruments have been widely used in thyroid surgery, which can significantly reduce intraoperative bleeding, significantly shorten the operation time, and perform delicate operations without increasing the complications of surgery. However, the treatment of thicker veins should be supplemented with silk ligation, and training in the use of energy instruments should be enhanced. (4) Bleeding from the broken end of the strap muscle. When a large thyroid mass is removed during thyroid surgery, it may be necessary to dissect the strap muscles. Since there are often small blood vessels between the muscles, improper handling may lead to postoperative bleeding. Therefore, if the strap muscle needs to be severed during surgery, it must be properly ligated or coagulated using energy instruments. (5) Bleeding under the anterior jugular vein, anterior jugular vein arch or skin flap. Avoid damaging the anterior jugular vein as much as possible when freeing the subcervical flap during surgery, and once damaged, sutures above and below the severed end should be performed to stop bleeding. Some larger subclavian vessels should also be ligated or coagulated. (6) Bleeding from the internal jugular vein and its branches. When lymph node dissection in the lateral jugular area is performed and the internal jugular vein needs to be exposed, the internal jugular vein may be damaged, and the increase of pressure in the internal jugular vein after surgery will directly lead to the dislodgement of the ligature, so meticulous hemostasis must be performed intraoperatively. In addition, when postoperative drainage is placed in the thyroid gland, it is often located in the deep surface of the strap muscle, resulting in poor drainage of the deep surface of the broad cervical muscle and the surface of the strap muscle forming a shallow closed cavity, which is prone to the formation of blood accumulation. The author’s experience is that the lower end of the cervical white line is not completely sutured, leaving a gap of about 1 cm, which is conducive to shallow closed cavity drainage. (1) Patients with hyperthyroidism and toxic nodular goiter are more prone to intraoperative and postoperative bleeding than other thyroid disorders because of the rich blood supply to the thyroid gland. (2) Patients with hemophilia, cirrhosis in its decompensated stage, chronic renal insufficiency, thrombocytopenia and other diseases with poor coagulation function. (3) Long-term use of anticoagulant or antiplatelet drugs such as heparin, warfarin, aspirin, and Poliovel is required due to coronary artery disease, thrombotic disease, etc. (4) A history of previous thyroid surgery or a large thyroid mass with abundant blood supply. Liu et al. summarized the following risk factors for post-thyroidectomy hemorrhage by Meta-analysis: advanced age, male, Graves’ disease, antithrombotic drug use, bilateral surgery, cervical lymph node dissection and history of previous thyroid surgery, while the use of drainage devices and pathological benignity were not significantly associated with post-thyroidectomy hemorrhage in this analysis. In addition, Chen et al. also concluded by multifactorial analysis that tumor diameter >3 cm and postoperative systolic blood pressure >150 mmHg (1 mmHg=0.133 kPa) were also independent risk factors for postoperative thyroid bleeding. Third, the high-risk actions of patients causing bleeding after thyroid surgery Post-operative bleeding of the thyroid gland often occurs after violent vomiting, coughing, sneezing, forceful breath-holding during defecation or urination and vigorous neck activities, because these actions can lead to an increase in venous return pressure, causing the originally closed blood vessels to reopen and bleed, so post-operative coughing and vomiting can be reduced by using anti-coughing and anti-emetic drugs to avoid the elevation. When removing the drainage tube after thyroid surgery, negative pressure should be removed in advance, and rough extraction is contraindicated to reduce the incidence of bleeding during extraction.