Thyroid storm is caused by the release of large amounts of thyroid hormones into the bloodstream, and it occurs 12 to 36 hours after surgery, with a rapid onset, rapid development, and high mortality rate, often manifested as fever, cardiac arrhythmia, and neurological symptoms. Thyroid crisis (thyroid storm) is rare as one of the endocrine emergencies, with a mortality rate of more than 20%. There are no clear diagnostic criteria worldwide, so it is difficult to accurately determine the occurrence of thyroid crisis. For moderate hyperthyroidism or above, surgery is still the most common and effective treatment method, which can cure 90%-95% of patients.
1. Clinical manifestations and diagnostic criteria of thyroid crisis
When thyroid crisis occurs after thyroid surgery it is often manifested as.
(1) Fever. It is often characterized by high fever (over 39°C), flushed skin, and profuse sweating. However, hypothermia may also be present. This type of thyroid crisis is rare and can easily be overlooked when it occurs, with very serious consequences.
(2) Cardiovascular abnormalities. Tachycardia, most often manifested as sinus tachycardia with a heart rate >120 beats/min, can also manifest as supraventricular arrhythmias. The pulse pressure difference increases, and in severe cases, heart failure or shock occurs.
(3) Central nervous system dysfunction. Neurological manifestations include restlessness, excitement, irritability, delirium, anxiety, confusion, trance, and coma in severe patients.
(4) Gastrointestinal tract dysfunction. Such as vomiting, diarrhea, strangulated intestinal obstruction, acute peritonitis, etc. Some patients may have jaundice or liver injury, and in severe cases, dehydration and shock. When thyroid crisis is clinically suspected, it should be treated actively and laboratory tests should be performed at the same time. It may show mild elevation of blood glucose; electrolytes may appear normal; liver dysfunction, elevated lactate dehydrogenase, elevated aspartate transferase, elevated bilirubin; elevated white blood cell count, and mild nuclear left shift may also occur in the absence of infection. To better define the occurrence of thyroid crisis, the Thyroid Crisis Diagnostic Scale is used for scoring. A score of more than 45 indicates the occurrence of thyroid crisis. In the author’s opinion, the diagnosis of thyroid crisis cannot be made entirely on the basis of this scale because not only are there differences in the response of the individual patient’s organism, but the clinical experience of the physician also affects the diagnosis and treatment of the disease.
2. Mechanism of thyroid crisis
As to why thyroid crisis occurs after thyroid surgery, the mechanism is not fully understood and may be related to the following factors.
(1) High levels of thyroid hormones in the blood circulation. Patients who suffer from hyperthyroidism before surgery will have excessive amounts of thyroid hormone in the serum. Under the condition of surgical stress, the organism becomes more sensitive to thyroid hormone and thyroid crisis can easily occur after surgery.
(2) Rapid increase of thyroid hormone levels in the serum. The rapid increase in postoperative thyroid hormone levels is more significant than the absolute value of pre-existing thyroid hormones in the serum being at a high level. The rapid accumulation of thyroid hormones in the serum after thyroid surgery is caused, on the one hand, by the excessive and massive release of thyroid hormones during surgery and, on the other hand, by the conversion of large amounts of bound thyroid hormones to free thyroid hormones in the serum. Free thyroxine readily enters the peripheral tissues, producing a potentially life-threatening hypermetabolic state and increasing the excitability of the nervous system.
(3) Sympathetic nervous system excitation. The sympathetic nervous system has been shown to be involved in the development of thyroid crisis. The signs and symptoms and physiological changes manifested during thyroid crisis are clearly related to increased catecholamines and beta-receptor agitation in the blood. Although serum levels of catecholamines are sometimes within the normal range, thyroxine can alter tissue sensitivity to catecholamines by altering the expression of adrenergic receptors.
(4) Elevated cellular responsiveness to thyroid hormones. At the onset of thyroid crisis, the markedly elevated cellular reactivity may be associated with hypoxia, hypovolemia, and lactic acidosis.
3. Causes of postoperative thyroid crisis and preventive measures
The causes of postoperative thyroid crisis are not clear, but may be related to the following factors.
(1) Inadequate preoperative preparation and surgery without good control of hyperthyroidism symptoms.
(2) The stressful reaction to surgery causes a large release of catecholamines and increased excitability of the sympathetic nervous system.
(3) Prolonged surgery, rough operation, and excessive squeezing, which cause a large amount of thyroxine to enter the blood.
(4) Pre-existing underlying diseases. Patients with underlying diseases such as cardiovascular disease, hepatic insufficiency, hemodynamic changes, and increased chance of thyroid crisis after surgery can affect the normal regulation of the thyroid gland by the hypothalamus and produce abnormal secretion of thyroxine, resulting in unstable concentration of thyroxine in the body.
Prevention of thyroid crisis should be the main focus. Adequate and perfect preoperative preparation, standardized and careful intraoperative operation, close observation of postoperative condition and reasonable postoperative management are the keys to prevent postoperative thyroid crisis. At the same time, close observation of patients’ vital signs changes after surgery and timely detection of the precursor features of thyroid crisis can save patients’ lives and reduce the morbidity and mortality rate.
Prevention of thyroid crisis.
(1) Adequate preoperative preparation. Preoperative oral administration of compounded iodine solution (iodine concentration 5%), 5 drops/time, 3 times/d, at the beginning, increasing by 1 drop to 15 drops each time day by day, maintained for l-3 d. Take 15 drops again until 1 h before surgery on the day of surgery. The solution inhibits protein hydrolase and reduces the decomposition of thyroglobulin, which rapidly inhibits the release of thyroxine (TH) and maintains the effective iodine content in the body, preventing some patients from refusing to take the medication due to pain or being unable to take the medication after surgery, which may cause sudden interruption of the iodine action and induce thyroid crisis. Oral anti-thyroid drugs such as propylthiouracil (PTU) can also be used to control thyroid symptoms, as well as the combined application of insulin, to take a comprehensive treatment approach to reduce the patient’s basal metabolic rate to the normal range before surgery.
(2) Intraoperatively, dexamethasone 10mg or hydrocortisone 100mg intravenously can be routinely given after more than 1h of surgery, which not only can play a role in maintaining the stability of the internal environment and anti-edema, but also replenish the hormones needed in the body to prevent acute respiratory asphyxia and the occurrence of thyroid crisis.
(3) Take symptomatic treatment after surgery, especially for patients with underlying diseases such as hypertension and diabetes mellitus, antihypertensive and hypoglycemic treatment should be given to control blood pressure below 140/85 mm Hg (1 mm Hg=0.133 kPa) is appropriate. Dexamethasone 10-20 mg or hydrocortisone 100-200 mg intravenously, followed by half of the above drugs intravenously the next day, and discontinued 48 h after surgery. Continue to take compound iodine solution, 15 drops/dose, 3 times/d, decreasing by 1 drop each time day by day, and maintain for 5 d. Continue the medication for 1 week after surgery for patients taking insulin at the same dose as before surgery, 20 mg/dose, 3 times/d, to bring their basal metabolic rate (BMR) to normal or almost normal, and then gradually reduce the dose. It has been reported in the literature that aggressive treatment is necessary if a patient develops hypothermia, as this condition often signals the onset of a more severe thyroid crisis. Symptoms of thyroid crisis may include a fast and weak pulse, a small pulse pressure, and a drop in blood pressure, eventually progressing to a condition where blood pressure is not easily measured and a slowed heart rate or even shock occurs. At the same time, the patient’s vital signs should be closely monitored and measured every 15 to 30 minutes.