Air embolism: etiology and pathogenesis
The primary cause of air embolism lies in a gross violation of blood transfusion technique. The complication occurs if atmospheric air enters the infusion set, or if medical personnel fail to timely stop blood infusion administered under pressure.
The mechanism of this critical event (pathogenesis) represents a clear sequence of events. Air bubbles penetrate into a peripheral vein, from which they rapidly migrate with the blood flow to the right side of the heart. From the right ventricle, air is forced into the lesser circulation, causing mechanical blockage (occlusion) of the pulmonary artery trunk or its large branches. It is important to remember that the critical volume is considered to be a single-moment entry into the bloodstream of just 2–3 cm³ of air.
Clinical presentation of air embolism
Symptoms develop fulminantly and proceed like severe pulmonary thromboembolism (PE), but the substrate is air. The patient suddenly develops the following signs:
- Sharp, intense chest pain.
- Pronounced dyspnea and sudden severe cough.
- Characteristic skin discoloration — cyanosis (bluish tint) of the upper half of the torso.
- Hemodynamic disorders: a drop in blood pressure (BP) against the background of a weak, very rapid pulse.
- Psychomotor agitation accompanied by a pronounced feeling of fear and anxiety.
The prognosis for this complication is most often unfavorable, which requires an instantaneous reaction from medical personnel.
Thromboembolism and pulmonary infarction
Unlike air embolism, thromboembolism during blood transfusion is caused by the entry of material substrates—blood clots—into the bloodstream. These emboli can form in two ways: either directly during prolonged storage of the blood product, or right in the recipient's vein against the background of developing local phlebitis or thrombosis at the puncture site.
Pathogenetically, thromboembolism proceeds similarly to air embolism; however, small blood clots more often occlude not the main trunk, but the small branches of the pulmonary artery. This leads to the formation of a pulmonary infarction.
The classical clinical picture of pulmonary infarction includes:
- Chest pain (associated with pleural involvement).
- Cough, which is initially dry in nature and then accompanied by hemoptysis (discharge of bloody sputum).
- Elevated body temperature (a reaction to pulmonary tissue necrosis).
X-ray examination is used to confirm the diagnosis, visualizing a picture characteristic of focal pneumonia.
Principles of emergency care
Management tactics for suspected embolism do not tolerate delay. The action algorithm includes:
- Immediate cessation of blood transfusion (closing the infusion set).
- Initiation of full-scale resuscitation measures.
- Performance of mechanical ventilation to combat acute hypoxia.
- Intravenous administration of cardiovascular drugs to stabilize falling blood pressure and support cardiac activity.
Briefly: answers to topical questions
How does the clinical picture of air embolism differ from transfusion shock during incompatible blood transfusion?
The clinical picture of air embolism is characterized by acute respiratory disorders, whereas transfusion shock manifests in a staged course with the development of renal failure.
| Sign | Air Embolism | Transfusion shock |
|---|---|---|
| Symptoms | Sharp chest pain, dyspnea, severe cough, cyanosis of the upper half of the torso, psychomotor agitation | Decrease in systolic blood pressure (SBP), development of uremia and azotemia |
| Hemodynamics | Weak rapid pulse, drop in blood pressure | Drop in SBP (grade I — down to 90 mm Hg, grade III — below 70 mm Hg) |
| Course | Acute onset (air PE) | Periods: shock proper, oliguria and anuria, restoration of diuresis, recovery |
The triad of pulmonary infarction in thromboembolism: "BCP" — Pain (chest), Cough (with hemoptysis), Temperature.
Class and exam questions
What amount of air causes critical consequences during blood transfusion?
For the full clinical picture of air embolism to develop, a single-moment entry of 2–3 cm³ of air into a vein is sufficient.
What is the character of the cough during the development of pulmonary infarction?
At the onset of the pathology, the cough is dry; however, it is soon replaced by a cough with hemoptysis (discharge of bloody sputum).
What is visible on the radiograph during occlusion of small branches of the pulmonary artery?
Radiologically, pulmonary infarction caused by small thrombi is defined as a picture of focal pneumonia.
What else to study on this topic
- Technique of safe blood transfusion and priming of infusion sets
- Rules for blood product storage for the prevention of clot formation
- Algorithm for cardiopulmonary resuscitation in PE
- Pharmacology of cardiovascular drugs used in shock
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