pulmonary encephalopathy



OVERVIEW

Definition

Pulmonary encephalopathy is a clinical syndrome characterized by respiratory insufficiency caused by various reasons, resulting in hypoxia, carbon dioxide retention, acidosis and other pathological changes, which in turn induces a series of neuropsychiatric symptoms.

Pulmonary encephalopathy is one of the serious complications of chronic emphysema and pulmonary heart disease (hereinafter referred to as “pulmonary heart disease”), and it is also the main cause of death in patients with pulmonary heart disease.

Types

According to the clinical manifestations at the onset of the disease, it can be divided into the following three types:

Excitable type

The initial manifestations are mainly neurological excitation symptoms, such as restlessness, hallucinations, disorganized speech, and even wild screaming and convulsions.

Inhibited type

The initial manifestation is indifference, sleepy thoughts, mental depression, etc., and gradually enter into drowsiness and shallow coma.

Indeterminate type

The symptoms of excitement and inhibition appear alternately.

Morbidity

There is no exact epidemiologic data.

Both sexes can develop the disease, with males being slightly more common than females.

Etiology

Causes

Chronic lung diseases

The most common are chronic bronchitis and asthma with emphysema, which together account for about 78.0% to 86.4%.

Severe tuberculosis accounts for 3.9% to 8.9%.

Thoracic deformities accounted for 2.1% to 3.9%.

Pulmonary fibrosis and lung cancer can also lead to pulmonary encephalopathy, which accounts for a relatively small percentage of cases.

Neurologic diseases

A variety of neurological diseases (e.g. acute infectious polyneuritis, cranial nerve injury, brainstem tumor, brainstem encephalitis, brainstem injury, cervical spine injury, progressive medullary palsy, myasthenia gravis crisis, etc.) can cause acute or subacute respiratory failure leading to pulmonary encephalopathy.

Predisposing factors

Acute respiratory tract infection

The most common predisposing factor, accounting for about 80% of cases.

Acute or chronic respiratory obstruction

Such as severe respiratory spasm, upper airway obstruction (sputum retention, foreign body or tumor obstruction, etc.), hemoptysis, etc.

Improper treatment

Chronic respiratory insufficiency using inappropriate doses of sedatives, pethidine, morphine and other drugs that inhibit breathing.

Use of large doses of corticosteroids or large doses of inhaled high concentration oxygen, etc.

Disorders of the internal environment

Water and electrolyte disorders can also trigger pulmonary encephalopathy.

Circulatory disorders

Such as shock, heart failure, etc.

Pathogenesis

The pathogenesis of pulmonary encephalopathy has not yet been fully elucidated, but is currently thought to be caused by hypoxia due to respiratory insufficiency, hypercapnia due to carbon dioxide retention, and disturbances in the internal environment.

Hypoxia

Chronic pulmonary disease leads to hypoxemia, which causes cerebral hypoxia, increased acidic metabolites in the tissues cause vasodilatation and increased capillary permeability, resulting in cerebral edema and neuropsychiatric symptoms.

Cerebral hypoxia may also lead to exudation of red blood cells, causing peripheral vasculopathy and neurological symptoms.

Carbon dioxide retention

It is generally believed that when the partial pressure of carbon dioxide (PaCO2) increases to twice the normal value (i.e., 10.64 kPa), symptoms such as mental inhibition, dizziness, anorexia, anorexia, lethargy, disorientation, difficulty in concentration, delirium and semi-coma will occur.

When it increases to three times the normal value (i.e., 15.96kPa), “carbon dioxide paralysis” occurs and symptoms such as coma and convulsions are observed.

PaCO2 and pH do not exactly parallel psychoneurological symptoms, and in a few patients PaCO2 may be normal.

Acidosis

Failure to improve carbon dioxide retention will result in uncompensated respiratory acidosis.

Respiratory acidosis leads to tissue hypoxia, resulting in metabolic acidosis and a decrease in serum calcium, which leads to convulsions, increased excitability, hyperreflexia, and excitability and agitation due to edema of the brain tissue and nerve cells.

The presence of metabolic acidosis further reduces pH, but then respiratory excitability still cannot be increased due to respiratory failure, further increasing CO2 storage, exacerbating respiratory acidosis and the elevation of blood potassium and blood ammonia.

Respiratory acidosis and metabolic acidosis may exist singly or in combination, and both can cause a range of water and electrolyte disturbances, leading to an imbalance in the internal environment and damage to the brain and nerves.

Symptoms

Main Symptoms

Impaired consciousness

This is one of the common symptoms in pulmonary encephalopathy, and different degrees of impaired consciousness account for 62.3% to 90.0% of pulmonary encephalopathy.

In mild cases, it is characterized by drowsiness and lethargy, while in severe cases, coma may occur.

Mental symptoms

About 50% will have psychiatric symptoms.

The main manifestations are excitement, restlessness, babbling, depression, and sometimes hallucinations, delusions and other symptoms.

Before the appearance of psychiatric symptoms, disorientation and judgment may occur at an early stage.

Neurological symptoms

Convulsions occur in about 30% of cases.

Most are generalized, with no obvious limited symptoms.

In a small number of cases, the convulsions may be limited or progress from limited to generalized seizures.

A variety of involuntary movements are also seen, such as tremor and fluttering tremor are more common, as well as involuntary myoclonic seizures and myofascial fibrillation.

Hemiparesis or monoparesis may occur in about 4% to 5% of patients.

About 20% to 25% of patients may have optic papillary edema and exudation on funduscopic examination.

About 10% to 15% of patients may develop brain herniation and coma due to persistent increased intracranial pressure, and neuropsychiatric symptoms may worsen, leading to death in severe cases.

Complications

Brain herniation

Severe headache, vomiting, narrowed and asymmetric pupils, loss of light reflex, convulsions, and deep coma may occur.

The condition may deteriorate rapidly after brain herniation, resulting in severe vital signs disorders in a short period of time, with a very high mortality and disability rate.

Shock

Blood pressure may drop, cold extremities and other manifestations.

If not rescued in time, it may lead to circulatory failure and death.

Diffuse intravascular coagulation (DIC)

Skin purpura, bruising, blood leakage from puncture site and other manifestations may occur.

Renal failure

Anuria, oliguria and other manifestations may occur.

Renal failure further aggravates the degree of the above complications, resulting in a vicious circle and ultimately leading to the death of the patient.

Emergency ulcers and bleeding in the digestive tract

Symptoms such as abdominal pain, vomiting blood, black stools, and blood in the stool may occur.

It can lead to hemorrhagic shock, acute severe anemia and other life-threatening conditions.

Myocardial injury

Chest tightness, dyspnea, sedentary breathing, pink foamy sputum, and impaired consciousness may occur.

Severe myocardial injury can lead to heart failure, malignant arrhythmia, cardiac arrest and other life-threatening conditions.

Consultation

Department of Medicine

Neurology

If there are symptoms such as unusual excitement, restlessness, babbling, hallucinations, delusions, drowsiness, convulsions, involuntary movements, hemiparesis, etc., it is recommended to consult a doctor in time.

Respiratory medicine

If you have a history of chronic lung disease and are experiencing symptoms such as unusual excitement or drowsiness, you may also visit the Respiratory Medicine Department.

Emergency Medicine

When unconsciousness occurs, it is recommended to immediately consult the Emergency Department or call 120 for emergency services.

Preparation

Preparation for medical consultation: registration, preparation of information, common problems

Tips for seeking medical treatment

Before seeking medical treatment, the patient should rest in bed and reduce activities and moving to avoid aggravating hypoxia.

If possible, low-flow oxygen should be given to the patient.

Preparation Checklist

Particular attention should be paid to the time of onset of symptoms, special performance, etc.

Are there symptoms such as excitement, restlessness, babbling, hallucinations, delusions, etc.?

Are there symptoms of drowsiness, lethargy, convulsions, involuntary movements, hemiparesis, coma, etc.?

How long have these symptoms been present?

What is the frequency and duration of the onset of these symptoms?

Is there a history of chronic lung disease such as chronic bronchitis, severe tuberculosis, thoracic malformations, lung cancer, etc.?

Is there a history of acute infectious polyneuritis, cerebral nerve injury, brainstem disease, progressive medullary palsy, or any other disease?

Any other history of disease?

Any recent use of glucocorticoids, diazepam, pethidine, morphine, etc.? What dose?

Test results from the last six months to bring to the doctor’s office

Laboratory tests: e.g. blood gas analysis

Imaging tests: e.g. chest X-ray, chest and head CT, magnetic resonance imaging (MRI) of the head, cardiac ultrasound, etc.

Medication used in the last 3 months, if available in boxes or packages, bring with you to the doctor’s office

Sedative-hypnotic drugs: e.g. diazepam, clonazepam, etc.

Opioids: e.g. morphine, pethidine, etc.

Glucocorticoids: e.g. prednisolone, dexamethasone, etc.

Diagnosis

Diagnosis is based on

Medical history

Medical history is not necessary for the diagnosis; the patient may have a history of the following conditions prior to the onset of the disease:

Chronic bronchitis, asthma with emphysema, history of severe tuberculosis, thoracic malformations, pulmonary fibrosis, lung cancer, and other chronic lung diseases.

History of neurological disorders such as acute infectious polyneuritis, cranial nerve injury, brainstem tumor, brainstem encephalitis, brainstem injury, cervical spine injury, progressive medullary palsy, myasthenia gravis crisis.

History of acute respiratory infections, acute or chronic respiratory obstruction (e.g., severe respiratory spasm, sputum retention, obstruction of the upper airway by foreign bodies or tumors, hemoptysis, etc.).

Presence of chronic respiratory insufficiency with inappropriate doses of sedatives, pethidine, morphine, etc.

Clinical manifestations

Usually begins with agitation, accompanied by vomiting, abdominal distension, auditory hallucinations, disorganized speech, and even screaming fits, convulsions, muscle tremors, pupillary changes, and optic disk edema.

In severe cases, epileptic convulsions, hemiparesis and pathological reflexes may appear, and then enter deep coma.

It starts with indifferent expression, sleepy thoughts and depression, and gradually enters into drowsiness, shallow coma, irregular respiration and finally deep coma.

Symptoms of excitation and inhibition alternate and finally enter deep coma.

Laboratory examination

It can find out whether the patient has hypoxia, carbon dioxide retention, acidosis and water-electrolyte imbalance.

It is important for the diagnosis of pulmonary encephalopathy.

It is often characterized by increased PaCO2, increased CO2 binding capacity, increased levels of standard bicarbonate (SB) and residual base (BE), and decreased blood pH.

In secondary respiratory acidosis combined with metabolic acidosis, PaCO2 may be elevated, and CO2 binding capacity, SB and BE may be normal or decreased.

When combined with metabolic alkalosis, PaC02 is elevated, CO2 binding capacity, SB and BE are significantly elevated, and pH is increased.

The erythrocyte count and hemoglobin are often increased, and the white blood cells are basically normal.

Electroencephalogram

Different degrees of diffuse abnormalities can be seen, and the degree of abnormality is basically consistent with the degree of cerebral hypoxia.

Imaging

It is not necessary for diagnosis, but mainly used to understand the etiology and differential diagnosis of pulmonary encephalopathy, including chest radiograph and chest CT, echocardiography, cranial CT and cranial MRI.

Diagnostic criteria and grading

Diagnostic criteria

At present, there is no unified diagnostic standard, and the diagnostic standard of pulmonary encephalopathy revised by the Third National Specialized Conference on Pulmonary Heart Disease in 1980 is as follows:

There is chronic chest and lung disease with respiratory failure, hypoxia and carbon dioxide retention.

Blood gas analysis shows hypoxemia, hypercapnia, and decompensated respiratory acidosis.

Have impaired consciousness, psychoneurologic symptoms or signs, and exclude other causes (e.g., cerebrovascular disease, infectious toxic encephalopathy, toxic effects of drugs, etc.) as the cause.

Grading

Depending on the severity of the patient’s condition, pulmonary encephalopathy can be categorized into the following 3 grades.

Manifestations of trance, indifference, lethargy or polyphasia, and euphoria, but no abnormal neurologic signs.

Manifestations such as semi-coma, delirium, agitation, and mild muscle twitching, accompanied by sluggish pupil radiation to light, but complications such as upper gastrointestinal hemorrhage and DIC have not yet occurred.

Coma or epileptiform convulsions, unresponsiveness to various stimuli, pupil dilatation or narrowing, loss of physiologic reflexes or pathognomonic neurologic signs.

Complications such as upper gastrointestinal bleeding, shock, and DIC may occur.

Differential diagnosis

A variety of diseases have similar clinical manifestations to pulmonary encephalopathy and need to be differentiated.

Hyponatremia

Similarities: both can cause impaired consciousness, psychoneurological symptoms or signs.

Differences: hyponatremia is often seen in elderly patients with pulmonary heart disease, serum sodium is often significantly reduced, and the symptoms can be rapidly improved after sodium supplementation, and the partial pressure of blood oxygen is not significantly reduced, and cyanosis is not significant; pulmonary encephalopathy serum sodium can be normal, the partial pressure of blood oxygen is often significantly reduced, and cyanosis is significant.

Drug reaction

Similarity: In large doses of hormones, chloramphenicol, niclosamide and atropine, or when the patient is more sensitive to the drugs, psychoneurological symptoms or signs similar to pulmonary encephalopathy can be induced.

Differences: drug reactions may gradually disappear after stopping drugs, neuropsychiatric symptoms, blood gas analysis without obvious hypoxia; pulmonary encephalopathy partial pressure of blood oxygen is often significantly reduced.

Geriatric mental disorder

Similarity: Geriatric psychiatric disorders caused by cerebral atrophy, vascular dementia, chronic alcoholism, etc. can cause a series of neuropsychiatric symptoms and signs similar to pulmonary encephalopathy, especially when complicated by respiratory failure, which should be differentiated from pulmonary encephalopathy.

Difference: According to the history and head CT, head MRI, blood gas analysis and other auxiliary examinations, we can distinguish whether the neuropsychiatric disorder is caused by the primary disease or pulmonary encephalopathy.

Treatment

Aim of treatment: to improve hypoxia, correct the internal environment disorder, and avoid the progression of the disease.

Treatment principle: keep the airway open, improve and correct hypoxemia, carbon dioxide retention and metabolic dysfunction as soon as possible, and actively remove the cause of the disease.

General treatment

Rest

Rest in bed, reduce activities to avoid aggravating hypoxia.

Keep the airway open

Promptly clear oropharyngeal secretions and suction if necessary to keep the airway open.

If there is airway obstruction, promptly relieve the cause of obstruction.

Perform tracheal intubation or tubectomy in time to establish an artificial airway.

Medication

Antibiotics

Lung infection is the main cause of pulmonary encephalopathy, effective and sufficient amount of antibiotics to control lung infection is the key to successful treatment.

Commonly used drugs include anti-bacterial drugs such as ceftriaxone and moxifloxacin, and anti-fungal drugs such as fluconazole and voriconazole.

Respiratory stimulants

It can excite the respiratory center, improve the respiratory function of the patient, and relieve the patient’s hypoxia and carbon dioxide retention.

Mostly advocated for use after antibiotics, antispasmodic and asthma medications, the airway is basically open, before and after the evacuation of the ventilator, weak spontaneous respiration and comatose people.

Commonly used drugs include Lobelin and Nicosamide.

Should not be used alone for a long time, so as not to cause respiratory muscle fatigue, aggravate the condition.

Glucocorticoid

Glucocorticosteroids can reduce the inflammatory reaction of the body, reduce the damage of hypoxemia and hypercapnia to brain cells, relieve the spasm of small airways, and have a definite curative effect on pulmonary encephalopathy.

Commonly used drugs include methylprednisolone and hydrocortisone.

Drugs to improve brain cell metabolism

They can improve the metabolism of brain cells and reduce the damage to brain cells caused by hypoxia, carbon dioxide retention and acidosis.

Commonly used drugs include cytidine, adenosine, coenzyme A and so on.

Dehydrating agent

Can eliminate or reduce cerebral edema, reduce intracranial pressure, but have no effect on pH in brain tissue.

It can be considered to be applied when diuretic treatment is ineffective.

Commonly used are 20% mannitol, etc.

Others

Respiratory acid-base imbalance and secondary electrolyte imbalance should be treated promptly.

Reasonable application of asthma medications can relieve airway spasm, facilitate sputum discharge, reduce airway resistance, and increase alveolar ventilation, commonly used theophyllines (e.g., aminophylline) and β receptor stimulants (e.g., salbutamol).

Mechanical ventilation

Establishment of artificial airway and implementation of assisted mechanical respiration are the best indications and effective measures to rescue pulmonary encephalopathy.

Mechanical ventilation should be used early when pulmonary encephalopathy does not improve significantly after short-term drug treatment. When there is no improvement after 3-5 days of rescue by tracheal intubation, tracheotomy should be performed to connect the ventilator (the time of transnasal intubation can be appropriately prolonged).

Prognosis

Cure

Pulmonary encephalopathy is a critical illness with poor prognosis, high mortality and disability rate, according to domestic reports, its hospitalization mortality rate can reach 40.6%～67.2%.

Early diagnosis and early treatment of pulmonary encephalopathy should be emphasized, and supervision should be strengthened for high-risk groups, and immediate attention should be paid once it occurs, in order to reduce the incidence and death rate.

Prognostic factors

The prognosis of pulmonary encephalopathy is affected by many factors, and the following factors often lead to a poor prognosis.

Advanced age.

Poor cardiopulmonary function.

Severe primary disease.

Failure to receive standardized treatment in a timely manner.

Serious complications, such as brain herniation.

Daily

Daily management

Maintain a balanced diet and nutrition.

For patients who are emotionally agitated and have impulsive behaviors such as hurting people and destroying things, safety precautions should be strengthened, attention should be paid to guarding, and the custody of dangerous items such as knives and ropes should be strengthened to avoid patients from wandering off, destroying things and hurting people, committing suicide and self-harm.

Rehabilitation training should be carried out as early as possible under the guidance of doctors after the condition is stabilized, but strenuous exercise is not recommended.

Patients should be actively listened to, supported, comforted and understood, and helped to build up confidence and hope.

Follow-up and review

Regular follow-up examinations of patients with pulmonary encephalopathy can help doctors assess the changes in the patient’s condition and adjust the treatment plan.

The follow-up schedule should be set by the specialist according to the patient’s specific condition.

The main items for follow-up include laboratory tests such as blood gas analysis and imaging tests such as chest X-ray and chest CT.

Prevention

The following measures can effectively prevent the occurrence of pulmonary encephalopathy.

Active treatment of the primary disease

Patients with respiratory, circulatory, neurological and muscular disorders should be actively treated to improve the condition of the primary disease and arrest the progression of the disease.

Enhance safety awareness

Avoid inhalation of foreign bodies.

Strictly follow the doctor’s prescription of medication, avoid overuse of hypnotic and sedative drugs, opioids.