Arterial O2 saturation alone does not predict pulmonary to systemic blood flow ratio in the post-operative norwood patient

Roozbeh Taeed, David P. Nelson, Steven M. Schwartz, Jeffrey M. Pearl, Peter B. Manning, Robert H. Beekman

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Introduction: This study tests the hypothesis that arterial O2 saturation (SaO2) is a good predictor of pulmonary flow (Qp) and pulmonary to systemic flow ratio (Qp/Qs) after Norwood palliation. Methods: Hemodynamic data were collected in 7 patients (3-5 days post Norwood palliation) who underwent controlled, prospective manipulation of inspired O2 and CO2 concentration. Using indwelling Unes placed intra-operatively, 43 complete oximetric studies were obtained. Qp and Qs were calculated from simultaneously measured O2 content in the aorta (Ao), superior vena cava (SVC) and pulmonary vein (PV). O2 Consumption was measured (n=3) or was assumed (n=4) at 12cc/kg/min. Results: Multiple regression was used to predict Qp/Qs and Qp (dependent variables) from O 2 saturation data. SaO2 alone correlated weakly with Qp/Qs or Qp (R2 0.17 and 0.21, respectively; p<0.01). Estimation of Qp/Qs and Qp improved substantially with inclusion of SVC and PV O2 saturation data. This was explained by variability of O2 saturation observed in SVC (range: 32-68%) and PV (range: 76-99%) blood. Of note, PV saturation <95% was observed in 13 of 43 (30%) studies, including all 5 studies in sub-ambient oxygen. Nine measurements in 6 patients were <90%. Conclusions: This study demonstrates for the first time that pulmonary venous desaturation is common after the Norwood procedure; it also confirms that variations in SVC saturation occur routinely. Therefore, SaO2 alone is a poor predictor of Qp and Qp/Qs after the Norwood operation. Coefficient of Determination (R2) Qp/Qs Qp Ao alone .17 .21 O2 Saturation Ao+SVC .65 .21 Data Ao+PV .43 .84 Ao+PV+SVC .93 .88.

Original languageEnglish
Pages (from-to)A40
JournalCritical care medicine
Issue number12 SUPPL.
StatePublished - Dec 1 1999


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