Abstract 14568: Clinical Indirect Indicators of Hemodynamics Do Not Accurately Reflect Systemic Oxygen Transport Status in Neonates After the Norwood Procedure
Objectives: Indirect indicators of hemodynamics (heart rate (HR), systolic (SAP) and diastolic (DAP) arterial pressures, arterial (SaO2) and venous (SvO2) O2 saturations) are commonly used to guild clinical treatments aiming to optimize O2 transport after the Norwood procedure. However, the adequacy of this practice has not been clearly defined. We aimed to determine the correlations between these indirect indicators and the direct measurements of systemic O2 transport parameters in these patients.
Methods: Systemic O2 consumption (VO2) was continuously measured using respiratory mass spectrometry postoperatively for 72 hours in 17 neonates. Arterial, superior vena cava and pulmonary venous blood gases and pressures were measured at 2-4 hour intervals to calculate cardiac output (CO), systemic blood flow (Qs) and vascular resistance (SVR), O2 delivery (DO2) and O2 extraction ratio (ERO2). HR, SAP and DAP were recorded at the same times.
Results: Heart rate ranged 116-220 bpm, SAP 42-100 mmHg, and DAP 23-49 mmHg. Qs positively correlated with SvO2 and negatively with SaO2 (p<0.0001 for both). CO positively correlated with SvO2 (p<0.0001) and SAP (p<0.01). SVR positively correlated with SvO2 (p<0.0001) and negatively with SaO2 (p=0.02). DO2 positively correlated with SaO2 (p<0.0001) and SBP (p=0.04), and negatively with SvO2 (p<0.0001). VO2 positively correlated with HR, SAP and DAP (p<0.01 for all) and negatively with SaO2 and SvO2 (p<0.05 for both). ERO2 positively correlated with HR (p=0.06) and SAP (p<0.01), and negatively with SvO2 (p<0.0001).
Conclusions: Indirect indicators of hemodynamics do not accurately reflect O2 transport status after the Norwood procedure, except for SvO2, which, however, does not differentiate between VO2 and DO2. Higher HR and SAP correlate with a worse balance of oxygen transport. Clinical treatments when using vasoactive and intropic drugs should not be guided by the indirect indicators. Direct measurements of systemic O2 transport parameters are important in the care of neonates after the Norwood procedure.
- © 2011 by American Heart Association, Inc.