Air embolism

Air embolism occurs as a result of air entering the vessels of the lungs or systemic circulation (paradoxical embolism).

Epidemiology

Since the first half of the 19th century, descriptions of air embolism in obstetrics have periodically appeared in the literature. The expansion of diagnostic capabilities (precordial Doppler, echocardiography, end-expiratory gas analysis) has made it possible to more accurately assess the frequency of air embolism in obstetrics. It is detected during cesarean section under general anesthesia in 52-71% of cases, and under regional anesthesia - in 39% of cases. Signs of AE are detected with approximately the same frequency (10-37%) during spontaneous labor. Clinical manifestations are noted only in 0.78% of cases.

Causes air embolism

Factors contributing to the development of VE in obstetrics:

• deviation of the uterus to the left and its removal into the wound cavity during a cesarean section (increases the pressure gradient),
• Trendelenburg position,
• placenta rotation and accreta,
• placenta previa,
• decrease in central venous pressure (during bleeding or BCC deficiency in severe gestosis),
• use of nitrous oxide in general anesthesia.

Air embolism is possible in the following clinical situations: cesarean section, premature detachment of a normally located placenta, manual separation of the placenta, instrumental curettage of the uterus, hysteroscopy, manipulations with a central venous catheter. Air embolism also occurs when venous vessels are gaping and when the gravitational gradient between the surgical wound and the right atrium is 5 cm of water.

Pathogenetic mechanisms leading to disruption of cardiac activity and respiration are similar to those in pulmonary embolism.

The severity of manifestations and mortality in air embolism depend on the volume, speed of air inflow, and localization of the air embolus. Air volumes greater than 3 ml/kg can lead to fatal blockage of blood flow from the right ventricle ("air lock"). Smaller amounts of air contribute to the disruption of ventilation-perfusion relationships and are manifested by hypoxemia, overload of the right heart, arrhythmia, and hypotension. Air entering the arterial circulation through an open oval foramen can manifest as acute coronary insufficiency and neurological symptoms. At a high rate of air inflow, air can pass into the systemic circulation and through the pulmonary vessels.

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Symptoms air embolism

Symptoms of massive air embolism include chest pain, cyanosis, distended neck veins, dyspnea (usually gasping breathing), brady- or tachycardia, arterial hypotension, and cardiac arrhythmia. In severe cases of air embolism, bronchospasm, pulmonary embolism, and circulatory arrest are possible. In paradoxical embolism, coronary or neurological symptoms may be present. Auscultation may reveal “drum” heart sounds, which are replaced by a “mill wheel” noise caused by the mixing of blood and air in the right ventricle.

Diagnostics air embolism

Using instrumental diagnostic methods, the following can be detected:

• increased central venous pressure and pulmonary artery pressure due to overload of the right heart,
• reduction of end-tidal CO2 levels during capnography,
• decreased saturation,
• hypoxemia,
• moderate hypercapnia,
• ECG shows signs of overload of the right heart - changes in the P wave, depression of the ST segment,
• precordial Doppler and echocardiography - air in the heart cavity.

To diagnose paradoxical embolism, computed tomography or magnetic resonance imaging of the brain or spinal cord is performed.

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Treatment air embolism

• Stop further air flow (surgical hemostasis, irrigation of the surgical field with saline solution, change of body position).
• Tilt the operating table to the left and lower the head end to displace the “air lock” and “lock” it in the right atrium or ventricle.
• If breathing occurs spontaneously, begin inhalation of 100% oxygen, switch to mechanical ventilation if necessary.
• During general anesthesia, stop the supply of dinitrogen oxide and perform mechanical ventilation with FiO ₂ 21.0.
• Stabilize hemodynamics (infusion therapy and vasopressors to eliminate hypotension).
• Try to aspirate air from the central vein and chambers of the heart through a catheter located 1 cm below the point where the inferior vena cava enters the right atrium.
• Speed up labor.
• In case of air embolus migration to the brain - HBO.
• In case of circulatory arrest - CPR.