Continuous Monitoring of Jugular Bulb Oxygenation during Carotid Temporary Balloon Occlusion
Background: Temporary balloon occlusion (TBO) helps assess the safety of ICA sacrifice in the treatment of aneurysms and head/neck cancers. Several techniques have been used in combination with the clinical exam during TBO to predict low flow ischemia after permanent occlusion (SPECT, MR, Xenon-CT, EEG, TCD). All have poor predictive value. Continuous jugular bulb oximetry (SjvO2) provides easily interpretable, real-time data about cerebral oxygen extraction. It is a surrogate measure for CBF under steady-state conditions and can identify hemispheric hypoperfusion. Methods: An oximetric catheter was placed in the jugular bulb that preferentially drained the hemisphere in question. In the setting of systemic heparinization and continuous neurologic monitoring, TBO of the ICA was performed for 30 min. Hypotension to 70% of baseline BP was induced with nitroprusside for the last 15 min of the TBO. SjvO2 and MAP were sampled at 0.5 Hz. A slope changepoint for the MAP vs. SjvO2 relationship was calculated with a two-phase linear regression model, to identify the point at which SjvO2 became independent of MAP. This inflection point defines the autoregulatory portion of the MAP vs. SjvO2 curve. SPECT tracer (5 patients) was injected during hypotension when available. TBO failure was based on SPECT and symptoms, blinded to the SjvO2 data. Results: 10 consecutive patients (mean age 57, 30% male, 40% with hypertension) were studied, 3 of whom failed TBO. Two showed ischemic symptoms referable to the ICA tested (1 with normal SPECT), and 1 had equivocal symptoms but hemispheric hypoperfusion on SPECT. All 3 developed SjvO2 ≤ 45% at a MAP > 70 mmHg. In the 3 patients who failed TBO, the changepoint on the MAP vs. SjvO2 curves occurred at a higher MAP value than in the patients who passed TBO (mean MAP 100 vs. 72; p=. 05). The 7 patients without symptoms or abnormal SPECT tolerated sacrifice. Conclusion: Continuous SjvO2 monitoring may help identify patients who are still at risk for delayed ischemia despite subtle or no neurologic symptoms during TBO. It may also help guide post-occlusion hemodynamic management in patients with changepoints above 70 mmHg. Further study is warranted.