Parameters affecting occurrence of paradoxical air embolism

Area of Science:

• Cardiovascular Physiology
• Anesthesiology
• Surgical Research

Background:

• Paradoxical air embolism (PAE) is a risk during procedures involving venous air infusion and cardiac shunts.
• Understanding factors influencing PAE is crucial for patient safety in interventional cardiology and surgery.
• Atrial septal defects (ASDs) can facilitate right-to-left shunting of air, leading to PAE.

Purpose of the Study:

• To investigate the impact of different ventilation strategies and intravascular volume expansion on PAE occurrence.
• To determine if atrial pressure gradients influence PAE incidence.
• To evaluate the effect of positive end-expiratory pressure (PEEP) on PAE.

Main Methods:

• Surgically created atrial septal defects (ASDs) in 15 pigs.
• Transvenous balloon atrial septostomy created the ASDs.
• Monitoring included transesophageal echocardiography (TEE), ECG, EEG, and hemodynamic pressures.
• Air infused into the superior vena cava under four conditions: intermittent positive pressure ventilation (IPPV), IPPV with PEEP, spontaneous ventilation, and IPPV after hetastarch infusion.

Main Results:

• The incidence of PAE did not differ significantly among the four ventilation/infusion conditions.
• Releasing PEEP led to increased PAE in 9 of 14 animals.
• PAE occurred regardless of whether mean right atrial pressure (RAP) exceeded mean left atrial pressure (LAP).
• Transient reversal of the right-to-left atrial pressure gradient was observed during PAE when LAP exceeded RAP.

Conclusions:

• Ventilation patterns and intravascular volume infusion did not significantly alter PAE incidence in this ASD model.
• PEEP release appears to be a critical factor that can promote PAE.
• Atrial pressure gradients alone may not fully predict PAE occurrence, as transient gradient reversals can facilitate shunting.