The relationship between end-expired carbon dioxide tension and severity of venous air embolism during sitting neurosurgical procedures - A contemporary analysis.

STUDY OBJECTIVE: Determine if changes in expired carbon dioxide tension correlate with the severity of venous air embolism (VAE) associated hemodynamic changes in humans. DESIGN: Retrospective case series. SETTING: A single academic medical center with high-volume neurosurgical practice. PATIENTS: One hundred forty seven adult patients having neurosurgical procedures performed with general anesthesia in the sitting position who experienced venous air embolism. INTERVENTIONS: Identification of documentation of venous air embolism by either precordial Doppler sonography or transesophageal echocardiography. MEASUREMENT: Retrospective determination of changes in end-expired carbon dioxide (EECO2) changes associated with venous air embolism. MAIN RESULTS: Greater absolute and relative decreases in end-expired carbon dioxide tension were associated with greater hemodynamic manifestations of venous air embolism. However, based on receiver operating characteristic curve analysis, the absolute and relative changes in EECO2 have moderate utility for predicting the severity of hemodynamic consequences of venous air embolism as area under the curve for absolute and relative carbon dioxide tensions were 0.7654 and 0.7263, respectively. CONCLUSIONS: Greater magnitude of decreases in EECO2 is associated with hemodynamically-significant VAE in mechanically-ventilated patients. However, the magnitude of changes may have limited utility to diagnose VAE or exclude the diagnosis of VAE in patients with unexplained intraoperative hypotension.