Spatially resolved spectroscopy (NIRO-300) does not agree with jugular bulb oxygen saturation in patients undergoing warm bypass surgery

Purpose: Near infrared spectroscopy (NIRS) is a promising noninvasive metho d for continuous monitoring of cerebral oxygenation during cardiac surgery with cardiopulmonary bypass (CPB). This study was designed to study the agr eement between tissue oxygen index (TOI) measured by spatially resolved spe ctroscopy (NIRO-300) and jugular bulb oxygen saturation (SjO(2)) in patient s undergoing warm coronary bypass surgery. Methods: Seventeen patients undergoing warm coronary artery bypass surgery were studied. NIRS was continuously monitored and was averaged before CPB, five, 20, 40, 60 min on CPB, five minutes before end of CPB and ten minutes after CPB to coincide with SjO(2) measurements. Bypass temperature was mai ntained at 34-37 degreesC. Results: Bland and Altman analysis showed a bias (TOI-SjO(2)) of 6.7%, and wide limits of agreement (from 16% to -28%) between the two methods. In add ition, mean TOI was lower than mean SjO(2) during and after CPB. We observe d a statistically significant correlation between arterial carbon dioxide a nd SjO(2) measurements (r(2)=0.33; P=0.0003), but the former did not correl ate with TOI values (r(2)=0.001; P=0.7). Conclusion: Our results demonstrate a lack of agreement between SjO(2) and TOI for monitoring cerebral oxygenation during cardiac surgery. We conclude that the two methods are not inter changeable.