Multisite Near-Infrared Spectroscopy Predicts Elevated Blood Lactate Level in Children After Cardiac Surgery

Objectives: To determine if a relationship exists between regional oxyhemoglobin saturation (rSO₂) measured at various body locations by near-infrared spectroscopy (NIRS) and blood lactate level in children after cardiac surgery. Design: A prospective, observational study. Setting: A pediatric cardiac intensive care unit in a university hospital. Participants: Twenty-three children undergoing repair of congenital heart disease. Patients with single-ventricle physiology and/or residual intracardiac shunts were excluded. Interventions: None. Measurements and Main Results: Cerebral, splanchnic, renal, and muscle rSO₂ values were recorded every 30 seconds via NIRS for 24 hours postoperatively. Blood lactate levels measured minimally at 0, 2, 4, 6 and 24 hours postoperatively were correlated with rSO₂ values derived by averaging all values recorded during the 60 minutes preceding the blood draw. Twenty-three patients were enrolled with 163 lactate measurements and more than 39,000 rSO₂ observations analyzed. Cerebral rSO₂ had the strongest inverse correlation with lactate level followed by splanchnic, renal, and muscle rSO₂ (r = -0.74, p < 0.0001, r = -0.61, p < 0.0001, r = -0.57, p < 0.0001, and r = -0.48, p < 0.0001, respectively). The correlation improved by averaging the cerebral and renal rSO₂ values (r = -0.82, p < 0.0001). Furthermore, an averaged cerebral and renal rSO₂ value ≤65% predicted a lactate level ≥3.0 mmol/L with a sensitivity of 95% and a specificity of 83% (p = 0.0001). Conclusions: Averaged cerebral and renal rSO₂ less than 65% as measured by NIRS predicts hyperlactatemia (>3 mmol/L) in acyanotic children after congenital heart surgery. Hence, this noninvasive, continuous monitoring tool may facilitate the identification of global hypoperfusion caused by low cardiac output syndrome in this population.