OVERVIEW
Plateau cerebral edema is a severe dysfunction of the central nervous system caused by acute hypoxia. It is characterized by rapid onset and clinical manifestations of severe headache, vomiting, ataxia, and progressive impairment of consciousness. Pathological changes mainly include ischemic or hypoxic injury of brain tissue, cerebral circulation disorders, resulting in cerebral edema and increased intracranial pressure. If the treatment is not appropriate, it is often life-threatening.
Causes
Due to the reduction of atmospheric pressure and partial pressure of oxygen in the plateau area, hypoxia occurs in the human body after entering the plateau area. As the altitude rises, the partial pressure of oxygen in the inhaled air decreases significantly, and oxygen supply is seriously impaired. The cerebral cortex has the lowest tolerance to hypoxia, and with the aggravation of hypoxia, the aerobic metabolism of brain cells is impaired, the anaerobic metabolism is increased, the generation of ATP is reduced, and the sodium-ion pump of the brain cell membrane is dysfunctional, and the intracellular sodium and water are retained, which causes cytotoxic cerebral edema. Hypoxia can also act directly on vascular endothelial cells, release vasodilating factors, increase blood flow and blood volume, increase the permeability of blood vessel wall, colloidal substances, ions, water, etc. seepage out of the blood vessel wall into the interstitium, interstitial cerebral edema occurs. If the condition of cerebral hypoxia is not corrected in time, the vicious circle of “cerebral hypoxia – cerebral edema – increased intracranial pressure – cerebral circulatory disorders – difficulty in oxygen diffusion – cerebral hypoxia” can be formed.
Symptoms
1. Symptoms
Plateau cerebral edema clinically manifests as a series of neuropsychiatric symptoms, the most common symptoms being headache, vomiting, drowsiness or agitation, ataxia and coma. According to the occurrence and development of the disease, some people classify plateau cerebral edema into pre-coma (light cerebral edema) and coma (heavy cerebral edema).
(1) Pre-comatose manifestations Most patients have severe acute highland disease symptoms before coma, such as severe headache, progressive aggravation, significant panic and shortness of breath, frequent vomiting, decreased urine output, dyspnea, depression, indifference, unresponsiveness, lethargy, or irritability, and then turn into coma. There are very few patients without the above symptoms and directly into the coma stage.
(2) Coma stage performance If the patient fails to get timely diagnosis and treatment in the pre-coma stage, he/she usually turns into coma within a few hours. Patients show loss of consciousness, pale face, cold limbs, obvious cyanosis, violent vomiting, incontinence and so on. In severe cases, convulsions, heart failure, shock, pulmonary edema, severe infection and cerebral hemorrhage may occur, and the prognosis is poor if not rescued in time.
2. Physical signs
Patients often have cyanosis of lips and mouth, and increased heart rate. There are no special neurological signs in the early stage, tendon reflexes are mostly normal, and pupillary light reflexes exist. Severe patients may have abnormal limb tension, unilateral or bilateral positive pathological reflexes, cervical rigidity, unequal pupil size, and blunted or disappeared reaction to light. Fundus examination often reveals dilated veins, retinal edema, optic disc edema and hemorrhage.
Examination
1. Fundus examination
Most patients have different degrees of fundus changes, which are manifested in venous dilatation, increased arteriovenous ratio, punctate, flaky or flame hemorrhage. Retinal edema, optic disc edema and hemorrhage.
2.Laboratory examination
Lumbar puncture shows elevated cerebrospinal fluid pressure, and the results of routine blood and blood biochemistry tests are normal.
3.CT examination
Most patients can see diffuse cerebral edema of different degrees and scopes: the narrowing of the ventricles and sulci makes the brain parenchyma appear fuller, with symmetrically distributed low-density shadows centered on the corpus callosum, while a few patients have no abnormalities.
4. MRI (magnetic resonance imaging) examination
Symmetrical edema of the white matter of bilateral cerebral hemispheres, low signal in T1WI, high signal in T2WI, uniform signal, unclear edges.
Diagnosis
The diagnosis is most common in people who enter the plateau above 4000 meters rapidly, and the clinical features of cerebral edema such as acute hypoxia-induced central nervous system dysfunction, severe headache, vomiting, drowsiness, ataxia and coma can be confirmed. Early diagnosis is very important, for those who can not alleviate the symptoms of acute highland disease and progressive aggravation, should be alert to the occurrence of highland cerebral edema.
Differential diagnosis
It should be distinguished from intracranial infectious diseases, carbon monoxide poisoning, cerebral hemorrhage, epilepsy and other diseases.
Treatment
The disease mostly occurs in extra-high altitude areas, where transportation and medical conditions are poor. Therefore, early diagnosis and local rescue are very important. Those with serious conditions should be transferred to lower altitudes as soon as possible.
1. Symptomatic treatment
Absolute bed rest, keep the airway open, use symptomatic supportive treatment.
2. Oxygen therapy
Timely and effective improvement of cerebral tissue hypoxia is the key to treatment, should be given as early as possible to the high concentration of high-flow oxygen inhalation, with conditions should be given early hyperbaric oxygen therapy, can expand the effective diffusion of oxygen, rapidly correct the state of cerebral hypoxia, to interrupt cerebral hypoxia – cerebral edema of the vicious cycle.
3.Drug treatment
Oral acetazolamide, intravenous dexamethasone, intravenous 20% mannitol, furosemide diluted in 25% dextrose injection can reduce intracranial pressure and improve cerebral circulation. However, special attention should be paid to the complications caused by dehydration and excessive diuresis. According to the condition of the discretionary use of corticosteroids, brain protective agents and other drugs.
4. Hypothermia treatment
Hypothermia can reduce cerebral blood flow, lower brain metabolic rate, and promote the recovery of injured cell function. Ice packs, ice caps or ice water enemas can be used to lower the temperature.
Prevention
Before entering the plateau, we should carry out mental and physical acclimatization exercises, such as conditions, it is best to carry out intermittent hypoxic stimulation and habitual exercise in the low-pressure cabin, so that the body can make some degree of physiological adjustment in a timely manner from the plains to the plateau hypoxic environment. In addition to the hypoxia especially susceptible to people, laddering up the mountain is the most secure, the safest way to prevent acute highland disease. If the first-time alpinists need to enter the plateau above 4,000 meters, they should generally stay at 2,500 to 3,000 meters for 2 to 3 days, and then the rate of ascent should not exceed 600 to 900 meters per day. After arriving at the plateau, no matter whether the disease is onset or not, hyperbaric oxygen therapy is given, which can effectively prevent the occurrence of cerebral edema. The first two days to avoid drinking alcohol and taking sedative hypnotic drugs, do not do heavy physical activity, but light activity can promote the habit. Avoid cold, pay attention to heat preservation, and advocate consuming more high-carbohydrate diet. The use of acetazolamide, dexamethasone, acanthopanax, rhodiola rosea, and compound party ginseng before entering the plateau may be effective in preventing and alleviating the symptoms of acute altitude sickness.