Intraoperative measurement of cortical oxygen saturation and blood volume adjacent to cerebral arteriovenous malformations using near-infrared spectroscopy.

Objective: Both cortical oxygen saturation (SaO(2)) and cortical blood volume (BV) are related to regional cerebral blood flow. Among a series of patients with cerebral arteriovenous malformations, we examined the problem of hyperemia after embolization/resection or resection with the intraoperative application of near-infrared spectroscopy.

Methods: Cortical SaO(2) and BV (intracapillary total hemoglobin concentrations) were measured, with near-infrared spectroscopy, in areas adjacent to the arteriovenous malformation for 20 patients, before and after resection. The absolute values for both parameters and postexcision/preexcision ratios (P-P ratios) were determined. Data were correlated with multiple clinical and preoperative angiographic parameters.

Results: Before resection, the mean SaO(2) was 49 +/- 16% and the mean BV was 12.65 +/- 7.41 mg/ml. After resection, SaO(2) increased for 17 of 20 patients and BV increased for 18 of 20 patients. The differences between pre- and postexcision values for both parameters were observed to be statistically significant (P < 0.01). The average P-P ratios were 1.5 +/- 0.4 for SaO(2) and 1.7 +/- 0.4 for BV. Correlation between the P-P ratios for the two parameters was good. The initial BV and the P-P ratios for both SaO(2) and BV were exclusively dependent on the extent of preoperative embolization. Postoperatively, two patients developed intracerebral hemorrhage or severe edema. Both demonstrated high P-P ratios for SaO(2) (2.3 and 2.1) and BV (1.6 and 2.1).

Conclusion: Intraoperative near-infrared spectroscopy is able to detect the hyperemic status of adjacent cortex after arteriovenous malformation resection. However, staged therapy with embolization and surgery results in less hyperemia after resection. While two patients with hyperemic complications exhibited very large increases in SaO(2) and BV, we cannot refute the normal-perfusion pressure breakthrough theory.