Air embolism is a blockage of the bloodstream by air bubbles that have entered the bloodstream from the external environment. Clinical manifestations depend on the type and size of the affected vessel. The most dangerous is the obturation of the coronary and pulmonary arteries, the blood supply system of the brain. When the PA is affected, there are signs of acute respiratory and heart failure. The cerebral form of the disease proceeds with the development of symptoms of ischemic stroke. The diagnosis is established on the basis of the clinical picture, Dopplerography data, capnogram, measurement of CVP. Specific treatment is aspiration of gas through a catheter, restoration of the integrity of the vascular bed.
ICD 10
T79.0 O08.2 O88.0
General information
Air embolism (AE) is an acute pathological condition that occurs when air enters the blood vessel from the outside. The amount of gas injected at the same time should be at least 10-20 ml, otherwise it will dissolve in the blood without causing harm. Pathology is considered quite rare, it accounts for no more than 2% of all possible types of vascular occlusion. It is detected with the same frequency in men and women, it is not age-related. Mortality with timely diagnosis and provision of qualified care ranges from 10 to 40%. The absence of medical benefits for embolization of pulmonary and cerebral vessels leads to the death of the patient in 90% of cases.
Causes
Spontaneous air ingress into the circulatory system of a healthy person is practically excluded. The pressure in most vessels is excessive in relation to the atmosphere, so there is no suction of gases when the vascular wall is damaged. The exception is the internal jugular vein, the pressure in which is lower than atmospheric when inhaled. The situation with dehydrated patients looks different. By reducing the CBV, the pressure in the central vessels becomes negative, violation of the integrity of the vessel wall can lead to ingress of gases from the environment. Common causes of air occlusion include:
- Traumatization. Atmospheric gases enter the bloodstream with lung barotrauma (sudden ascent from depth, incorrectly selected ventilator mode), chest injuries accompanied by rupture of blood vessels. AE is also detected against the background of injuries of other anatomical zones in the absence of timely stopping of profuse bleeding.
- Childbirth. The penetration of gases becomes possible with the rupture of the placental venous sinuses. Air is injected into damaged vessels under pressure during uterine contractions. The disease develops regardless of the magnitude of the central venous pressure. Symptoms can occur not only directly during childbirth, but also after 1-2 days.
- Medical procedures. Manipulations with a high risk of AE formation include operations on vessels, chest organs, and the brain, if an autopsy of the venous sinus is performed during the intervention. In addition, air can enter the blood supply system when the infusion system is loosely connected to the central venous catheter or during infusion therapy. This happens with a negative CVP.
Pathogenesis
Large air bubbles in the bloodstream can lead to occlusion of any vessels. Most often, pulmonary veins, heart vessels, arterial trunks that feed the brain are blocked. When the pulmonary artery is affected, regional intravascular hypertension, pancreatic overload and acute right ventricular insufficiency are noted. Further, the left ventricle is involved in the process, cardiac output decreases, peripheral blood circulation is disrupted, shock develops. PA air embolism is accompanied by the occurrence of bronchospasm, ventilation-perfusion imbalance, lung infarction and respiratory failure.
In case of violation of blood flow in the cerebral vessels, the formation of pathology occurs according to the type of ischemic stroke. In a certain part of the brain, blood supply is disrupted, the neural tissue experiences oxygen starvation and dies. A necrosis site is formed, multiple small hemorrhages occur in the brain tissue. The further course of the disease depends on the localization of the affected area. Paresis, paralysis, impaired cognitive functions, malfunctions in the activity of internal organs may be detected.
Classification
There are several criteria for the systematization of AE. Air embolism is classified according to the nature of the course (lightning, acute and subacute), the path of air penetration into the bloodstream (iatrogenic, traumatic), the direction of movement of the embolus (orthograde, retrograde, paradoxical). In clinical practice, the separation of the forms of the disease by the type of the affected vessel is used, including the following variants of pathology:
- Arterial. There is a blockage of large arterial trunks (coronary, pulmonary, cerebral). It occurs in 30-35% of cases, develops at lightning speed, proceeds heavily, with pronounced clinical symptoms. The patient dies within a few hours, sometimes minutes. For the formation of AVE, more than 40-50 cm3 of gas simultaneously entering the bloodstream is necessary.
- Venous. It is detected in 65-70% of cases. Leads to a violation of venous outflow. Symptoms progress relatively slowly, life-threatening conditions are rarely detected. It is prone to an under-current. With blockage of small veins and venules, it can be asymptomatic, while blood flow is provided by a system of collaterals. The exception is the air occlusion of the pulmonary veins, through which oxygenated blood flows from the lungs to the heart.
Symptoms
The clinical picture differs depending on the type and size of the affected vessel. If there is a violation of the outflow of blood through large peripheral veins, typical signs of thrombosis occur. The affected area swells, increases in size. When squeezing, severe soreness is determined. The skin in the pathology zone is cyanotic, local hyperthermia occurs. A systemic reaction is moderate tachycardia caused by the deposition of a certain volume of fluid and a decrease in CBV.
Air embolism of small branches of the pulmonary artery causes coughing, hemoptysis, episodes of syncope, shortness of breath for more than 20 breaths, tachycardia within 100-120 beats per minute. There are no hemodynamic disorders. With blockage of large trunks, a picture of an acute pulmonary heart develops. The patient has a sharp hypotension, swelling of the cervical veins, an increase in the size of the liver, the growth of CVP psychomotor agitation, increased heartbeat. The skin is pale, cold, covered with sticky sweat.
Damage to the coronary arteries leads to acute myocardial infarction. There are typical pains behind the sternum of a compressive nature. The use of nitrates does not give the expected effect. Blood pressure decreases down to shock figures. Pulmonary edema of cardiac origin is possible. The typical pattern of AMI is not always observed. In 40% of cases, the disease occurs in an atypical form, manifested by pain in the abdomen, throat, left arm, etc.
Embolization of the blood supply structures of the brain causes a stroke. A focus of necrosis forms in the brain tissues, the localization of which determines the clinical symptoms. The most common signs of ischemic stroke include paresis and paralysis, local decrease in muscle tone, paresthesia, speech disorders, blurred vision, dizziness, headache, stability disorders, drop attacks, weakening of skin sensitivity.
Complications
During embolization of peripheral arteries, trophic ulcers are formed, necrosis zones arise. Violation of venous outflow in the extremities leads to edema. Changes in the blood supply system of internal organs cause the weakening or complete cessation of their activities. Acute renal or hepatic insufficiency, intestinal paresis, insufficiency of heart and lung function may develop. The defeat of the cerebral circulatory structures provokes irreversible disorders in the body. There are paralysis, disorders in the psycho-emotional sphere, changes in the work of internal organs innervated by the damaged area of the brain.
Diagnostics
The diagnosis of VE is carried out by an anesthesiologist-resuscitator in tandem with the patient’s immediate attending physician. Clinical examination data combined with information obtained using hardware diagnostic techniques usually leave no doubt about the diagnosis. Difficulties arise when determining the type of embolism. It is necessary to differentiate vascular occlusion caused by air, gas bubbles formed endogenously with a sharp change in environmental pressure (caisson disease, gas embolism), thrombus, tumor, foreign body, conglomerate of bacterial cells. Diagnostic measures include:
- Physical. They are carried out in the intensive care unit or at the patient’s location. During the examination, indirect signs of thrombosis are detected and a preliminary diagnosis is made. It should be borne in mind that the disease does not always occur with a full set of symptoms, the frequency of occurrence of some of them does not exceed 50-60%.
- Laboratory. At the initial stages of air embolism development, laboratory examination is not very informative. There are changes in the composition of blood gases, acid-base balance, electrolyte balance. With the defeat of internal organs and the development of multiple organ failure, there is an increase in the activity of liver enzymes, an increase in the concentration of creatinine and urea in the blood. Destructive processes in muscle tissue cause an increase in myoglobin levels.
- Instrumental. When performing precardial, transesophageal or transcranial Dopplerography, it is possible to establish the presence of air in the vessels. The study is qualitative, it is impossible to determine the volume of gas with its help. The capnogram indicates an increase in the concentration of carbon dioxide at the end of exhalation, when measuring the CVP, an inadequate increase in indicators is revealed. The ECG shows ventricular extrasystoles, changes in the P wave, depression of the ST segment.
Treatment
Elimination of the consequences of air entering the vessels is carried out using medical and hardware methods of treatment. The amount of necessary care depends on the patient’s condition, the severity of the violation of vital functions, the availability of the necessary equipment in the clinic. Usually , the scheme of rehabilitation measures includes the following methods of exposure:
- Non-specific medications. Treatment is aimed at minimizing the clinical signs of the disease and preventing complications. The patient is prescribed steroid hormones, cardiotonics, loop diuretics, vasodilators, antioxidants. At the recovery stage, multivitamin complexes and nootropic drugs are used. With severe respiratory insufficiency, the patient is transferred to a ventilator in the mode of forced ventilation.
- Hardware. Air embolism is treated with hyperbaric oxygenation and controlled hypothermia. HBO is carried out under a pressure of 2-3 atmospheres, the number of sessions varies from 5 to 12. The duration of each of them is 45 minutes. When using hypothermia, the patient’s body is cooled to 34 ° C. Both barotherapy and cold contribute to an increase in the solubility of gases in the blood, which makes it possible to destroy a blood clot that is inaccessible for surgical removal.
- Operational. The optimal method of embolus extraction in intracardiac AE is its aspiration through a subclavian catheter. In this case, several hundred milliliters of blood are removed, which may require massive infusion therapy or hemotransfusion. If the embolus localization is accurately determined, it is possible to open a vessel or venous sinus.
Prognosis and prevention
The outcome is favorable in cases where the air can be removed with the help of a low-traumatic subclavian access. With intracranial or pulmonary embolus localization, the prognosis worsens, since it is almost impossible to extract it by surgical methods. The use of HBO and hypothermia does not allow for rapid normalization of blood flow, therefore, the likelihood of irreversible consequences increases. When peripheral veins and arteries are affected, there is usually no threat to life, but the restoration of the affected tissues takes a long time, complete regeneration is not always possible.
Air embolization most often occurs during medical manipulations, therefore, measures for its prevention fall entirely on the staff of the medical institution. During interventions on the superior vena cava, the patient should be in the Trandelenburg position, catheterization of the subclavian vein at the moment when the needle remains with the open end (disconnecting the syringe, removing the conductor) is carried out on a deep exhalation of the patient. With a low CVP, the completed infusion systems should be blocked in a timely manner.