The Carbon Dioxide Responsiveness of Cerebral Oxygen Saturation

Abstract

S354 INTRODUCTION: Continuous measurements of cerebral oxygen saturation (rSO2) and the change in hemoglobin density (HbI) measured by near infrared spectroscopy (NIRS) provide the information of the balance of supply and consumption of oxygen and cerebral blood volume noninvasively. To evaluate the measurement of rSO2 and HbI using NIRS technique for assessing the cerebrovascular carbon dioxide responsiveness, we compared with its responsiveness of both jugular venous saturation (SjO2) and the middle cerebral blood flow velocity (Vm) to varying PaCO2. METHODS: After CHR approval and written informed consent, 10 laminectomy patients were studied. Anesthetic induction and tracheal intubation was done with thiopental sodium 4-5 mg[center dot]kg-1 i.v. and vecuronium 0.8-0.1 mg[center dot]kg-1 i.v. Anesthesia was maintained with 0.5-1 % enflurane / 50% N2 O in O2. Radial artery was cannulated. The right side jugular bulb catheterization was done for the measurement of SjO2. The NIRS sensor (TOSTEC, Japan) was positioned on the right side of forehead to measure rSO2 and HbI. To measure Vm, transcranial Doppler probe was placed at the right temporal window. Simultaneous measurements of rSO2, HbI, SjO2 and Vm were performed at normo-, hypo- and hypercapnia. Descriptive data of rSO2, HbI, SjO2 and Vm were calculated at normo-, hypo- and hypercapnia and ANOVA was used for analysis. To compare the carbon dioxide responsiveness, linear regression analyses of rSO2, HbI, SjO2 and Vm, respectively, and PaCO2 were used. P < 0.05 was considered statistically significant RESULTS: (Table 1 and Table 2)Table 1: Descriptive DataTable 2: Results Using Linear Regression Analysis with PaCO2CONCLUSIONS: We conclude that lesser degree of carbon dioxide responsiveness of rSO2 and HbI was observed comparing its responsiveness of SjO2 and Vm. But, NIRS can be a useful noninvasive technique for assessing the cerebrovasular carbon dioxide responsiveness.