Abstract 17490: Cerebral Near Infrared Resonance Spectroscopy Insensitively Detects Critically Low Venous Oxyhemoglobin Saturation Following Stage 1 Palliation for Hypoplastic Left Heart Syndrome
Background: Venous oxyhemoglobin saturation (SvO2) is considered a gold standard in assessing the adequacy of tissue oxygen delivery (DO2); SvO2 <40% often represents compromised DO2. Regional oxygenation index (rSO2) based on near infrared resonance spectroscopy (NIRS) is frequently used to identify patients at risk for compromised DO2, though its sensitivity to detect these abnormalities in the postoperative setting is uncertain.
Hypothesis: We hypothesized that rSO2 would be <40 in at least 50% of patients with SvO2<40.
Methods: SvO2 was measured by co-oximetry (Radiometer ABL 800) from blood sampled from the superior vena cava as clinically indicated in n=88 neonates following the Norwood procedure for hypoplastic left heart syndrome. Only patients in whom the tip of the internal jugular catheter was confirmed to be in the SVC were included. A rolling average of SvO2 (assuming a constant change between each measurement) was created and matched to contemporaneously measured NIRS (ForeSight, CasMed) every 5 seconds. Then, because this device is calibrated to reflect 30% arterial oxyhemoglobin saturation (SaO2) and 70% SvO2, we corrected rSO2 for SaO2 contamination as follows: corrected rSO2 = (rSO2 - SaO2*0.3)/0.7. Groups were compared to SvO2 by linear regression and Bland Altman analysis.
Results: Among 1,792 correlations, SvO2 was <40% in 22.6%. Cerebral rSO2 correlated poorly with measured SvO2 (r2 =0.29, A). The mean bias was +10.6 (B). A low rSO2 (defined as a rSO2 <40) was only 3.9% sensitive and 98.6% specific in detecting SvO2<40%. Given the low prevalence of SvO2<40, the negative predictive value of NIRS>40 was 77.8%. Correcting rSO2 for SaO2 enhanced test performance, with corrected NIRS <40 having a sensitivity for SvO2<40 of 19% and specificity of 95% (C). This decreased positive bias to +3.4 (D).
Conclusion: Cerebral rSO2 is very insensitive in detecting critically low SvO2. Cerebral rSO2 >40 should not be reassuring for adequate DO2.
Author Disclosures: E. Rescoe: None. X. Tang: None. J.N. Kheir: None.
- © 2016 by American Heart Association, Inc.