Absolute Versus Relative Near-Infrared Spectroscopy in Pediatric Cardiac Patients*

Abstract

OBJECTIVES: Near-infrared spectroscopy (NIRS) has been increasingly accepted as a noninvasive marker of regional tissue oxygenation despite concerns of imprecision and wide limits of agreement (LOA) with invasive oximetry. New generation absolute monitors may have improved accuracy compared with trend monitors. We sought to compare the concordance with invasive venous oximetry of a new generation absolute NIRS-oximeter (FORESIGHT ELITE; CASMED, Branford, CT) with a modern widely used trend monitor (INVOS 5100C; Medtronic, Minneapolis, MN). DESIGN: Prospective single-center study. SETTING: Tertiary pediatric heart center. PATIENTS: Children undergoing elective cardiac catheterization under general anesthesia. Time-paired venous oximetry samples (jugular and renal) were compared with NIRS-derived oximetry by two monitors using regression and Bland-Altman analysis. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: We enrolled 36 children (19 female, 10 cyanotic) with median age 4.1 years (25–75%, 2.5–7.8 yr) and weight 16.7 kg (12.3–29.1 kg). The absolute difference between NIRS-derived and invasive jugular oximetry was less than 10% in 67% of occasions for both monitors. Correlation was fair (Spearman r s = 0.40; p = 0.001) for the FORESIGHT ELITE and poor (r s = 0.06; p = 0.71) for the INVOS 5100C. Bias and LOA were +6.7% (+22%, –9%) versus +1.3% (LOA = +24%, –21%), respectively. The absolute difference between NIRS-derived and invasive renal oximetry was less than 10% in 80% of occasions with moderate correlation (r s = 0.57; p < 0.001) for the FORESIGHT ELITE and in 61% of occasions with moderate correlation (r s = 0.58; p < 0.001) for the INVOS 5100C; bias and LOA were +3.6% (+19%, –12%) and –1.4 % (+27%, –30%), respectively. NIRS correlation with renal venous oximetry was worse for cyanotic versus noncyanotic patients (p = 0.02). CONCLUSIONS: Concordance and LOA of NIRS-derived oximetry with invasive venous oximetry in the cerebral and renal vascular beds was suboptimal for clinical decision-making. Cyanosis adversely affected NIRS performance in the renal site.