Hyperventilation causing syncope
Introduction
Introduction Hyperventilation caused by hyperventilation is a clinical manifestation of vasovagal syncope. Syncope refers to a brief loss of consciousness in a sudden episode, accompanied by a decrease or disappearance of muscle tone, which lasts for a few seconds to a few minutes, and is essentially a temporary reduction in cerebral blood flow. Syncope can be caused by cardiovascular diseases, nervous system diseases and metabolic diseases. However, many patients cannot find the cause based on medical history, physical examination, and auxiliary examination. They have long been called "unexplained syncope."
Cause
Cause
Various stimuli mediate reflexes through the vagus nerve, leading to dilatation of the visceral and muscle small vessels and bradycardia, sudden expansion of peripheral blood vessels, reduction of venous blood return to the heart, so that the heart has a reflex action that accelerates and strengthens contraction, and some people may be over-excited The vagus nerve and parasympathetic nerves, which cause the heartbeat to suddenly slow down and the peripheral blood vessels to dilate, resulting in lower blood pressure, hypoxia in the brain, manifested as arterial hypotension with transient loss of consciousness, self-recovery, and no neurological localization Syndrome.
Examine
an examination
Related inspection
Repeated breath test cerebrospinal fluid glucose and serum glucose ratio
The diagnosis of neurovascular-mediated vasovagal syncope has long been indirect, time consuming, and expensive, and often has no clear results.
The head-up tilt test (HUT) is a new type of examination method developed in recent years, which plays a decisive role in the diagnosis of vasovagal syncope. The positive reaction was that the sick child had a syncope with a significant decrease in blood pressure or a decrease in heart rate after the patient was tilted from the supine position.
The criteria for judging the positive result of the upright tilt test are as follows:
The child has syncope or syncope during the tilting process (dizziness and often accompanied by one or more of the following symptoms: decreased vision, hearing loss, nausea, vomiting, sweating, unstable standing, etc.) accompanied by the following conditions One:
1. Diastolic blood pressure <6.7Kpa (50mmHg) and/or systolic blood pressure <10.7Kpa (80mmHg) or average pressure drop of more than 25%;
2, sinus bradycardia (4-6 years old: heart rate <75 beats / min; 6-8 years old: heart rate <65 beats / min; 8 years or older: heart rate <60 beats / min) or sinus arrest > 3 More than two seconds;
3, transient II degree or more than atrioventricular block;
4, borderline rhythm (including escape heart rate and accelerated autonomic heart rate).
Type of reaction: According to changes in blood pressure and heart rate during the test, the positive reactions were divided into the following three types:
(1) Cardiac-suppressed response, characterized by a sharp drop in heart rate, showing bradycardia and no decrease in systolic blood pressure;
(2) Angiostatin-type response, blood pressure decreased significantly, with heart rate increased;
(3) Mixed reaction, blood pressure and heart rate were significantly decreased.
Diagnosis
Differential diagnosis
For children with repeated syncope episodes, after detailed medical history, understand the symptoms and signs at the time of onset, and then through the necessary auxiliary examinations such as electrocardiogram, EEG, biochemical examination and upright tilt test, it is not difficult to diagnose, but with Identification of the following diseases:
1. Cardiac syncope: The disease is caused by a sudden decrease in cardiac output caused by heart disease or a pause in blood flow, leading to cerebral ischemia. More common in severe aortic valve or pulmonary stenosis, atrial myxoma, acute myocardial infarction, severe arrhythmia, QT interval prolongation syndrome and other diseases. It is easy to identify by carefully asking about medical history, physical examination, and ECG changes.
2, hypoglycemia: This disease often has a history of hunger or the use of hypoglycemic drugs, mainly manifested as fatigue, sweating, hunger, and then appear syncope and unconsciousness, slow syncope, blood pressure and heart rate during the attack Change, can be unconscious, test blood sugar lower, intravenous glucose quickly relieve symptoms. 3, epilepsy: for patients with convulsive syncope episodes of vasovagal syncope should pay attention to the identification of epilepsy, by doing EEG, upright tilt test is not difficult to identify.
4, erect regulation disorder: the child manifested by the erect position of the erect position or the erect time may be slightly longer may have dizziness, vertigo, chest discomfort and other symptoms, severe cases may have nausea, vomiting, or even faint, no treatment can Get awake quickly and return to normal. It can be identified by an upright test, an upright tilt test, or the like. 5, rickets syncope: The disease has obvious mental factors before the onset, and before the crowd. When you have a seizure, you are conscious, have a breath or excessive ventilation, your limbs are struggling, your eyes are tight, and your face is flushed. The pulse and blood pressure are normal, and there are no pathological neurological signs. The episodes last for several minutes to several hours. After the attack, the mood is unstable. If there is fainting, it will be slow and will not be injured. It often has a similar history and is easy to vaginal. Sexual syncope identification.
In addition, the disease should be differentiated from hyperventilation syndrome.
