Non-invasive cardiac output and oxygen delivery measurement in an infant with critical anemia

Objective: To assess the combination of a non-invasive blood oxygen content (CaO ₂) monitor and a non-invasive cardiac output (CO) monitor to continuously measure oxygen delivery (DO ₂; DO ₂ = CaO ₂ × CO). Methods: DO ₂ was assessed during blood transfusions in an infant with acute hemolytic anemia following admission (~48 h). CaO ₂ was measured by Pulse Co-Oximetry, which also provides estimates of hemoglobin (Hgb) concentration and percent oxygen saturation. CO was measured by Electrical Velocimetry, which also provides an estimate of stroke volume (SV). Lactate levels, an indirect measure of adequate DO ₂, were assessed during the initial 8 h following admission. Results: Incremental blood transfusions during the first 36 h increased Hgb from 2.7 to 9.5 g/dL during which time heart rate (HR) normalized from 156 to 115 beats/min. Lactate levels decreased from 20 to 0.8 mmol/L in the first 7 h. Non-invasive Hgb and CaO ₂ measurements were well correlated with invasive Hgb and CaO ₂ measures (r ² = 0.88; P = 0.019; r ² = 0.86; P = 0.0074, respectively). CO decreased from 2.47 ± 0.06 to 1.28 ± 0.02 L/min and SV decreased from 15.9 ± 0.4 to 11.1 ± 0.2 mL/beat. Mean arterial blood pressure was stable throughout the admission with systemic vascular resistance increasing from 407.6 ± 15.2 to 887.7 ± 30.1 dynes-s/cm ⁵. DO ₂ was estimated to increase from 120.2 ± 18.9 to 182.4 ± 5.6 mL O ₂/min. Conclusions: Non-invasive contin- uous CO and CaO ₂ monitors are shown in this single case to provide continuous DO ₂ measurement. The ability to assess DO ₂ may improve hemodynamic monitoring during goal directed therapies.