During a posterior cervical fusion performed in the sitting position, sudden air detected by precordial Doppler is most consistent with which condition?

During a posterior cervical fusion performed in the sitting position, sudden air detected by precordial Doppler is most consistent with which condition?

• A. Decreased PaO2
• B. Increased end-tidal nitrogen
• C. Decreased arterial blood pressure
• D. All of the above

Answer: (D)

Venous air embolism is the key concept here. In the sitting position, open venous channels and negative pressure can draw air into the venous system during cervical spine surgery. Once air enters the venous circulation, it travels to the right heart and into the pulmonary vasculature, acutely impairing pulmonary perfusion and gas exchange. This causes hypoxemia, so arterial oxygen tension falls (decreased PaO2). The obstructed pulmonary blood flow and reduced return to the left heart also reduce cardiac output, leading to hypotension (decreased arterial blood pressure). At the same time, the air embolus is rich in nitrogen; as ventilation continues, the exhaled gas shows more nitrogen relative to CO2, so end-tidal nitrogen rises. These combined effects—lower PaO2, increased end-tidal nitrogen, and reduced blood pressure—can all occur with a venous air embolism detected by a precordial Doppler, so all of the above is the best answer.

Venous air embolism is the key concept here. In the sitting position, open venous channels and negative pressure can draw air into the venous system during cervical spine surgery. Once air enters the venous circulation, it travels to the right heart and into the pulmonary vasculature, acutely impairing pulmonary perfusion and gas exchange. This causes hypoxemia, so arterial oxygen tension falls (decreased PaO2). The obstructed pulmonary blood flow and reduced return to the left heart also reduce cardiac output, leading to hypotension (decreased arterial blood pressure).

At the same time, the air embolus is rich in nitrogen; as ventilation continues, the exhaled gas shows more nitrogen relative to CO2, so end-tidal nitrogen rises. These combined effects—lower PaO2, increased end-tidal nitrogen, and reduced blood pressure—can all occur with a venous air embolism detected by a precordial Doppler, so all of the above is the best answer.