title: Unrecognized pulmonary venous desaturation early after Norwood palliation confounds Gp:Gs assessment and compromises oxygen delivery.
abstract: BACKGROUND
  Hemodynamic stability after Norwood palliation often requires manipulation of pulmonary vascular resistance to alter the pulmonary-to-systemic blood flow ratio (Qp:Qs). Qp:Qs is often estimated from arterial saturation (SaO2), a practice based on 2 untested assumptions: constant systemic arteriovenous O2 difference and normal pulmonary venous saturation.
  
  
  RESULTS
  In 12 patients early (</=3 days) after Norwood palliation, simultaneous arterial, superior vena caval (SsvcO2), and pulmonary venous (SpvO2) oximetry was used to test whether SaO2 accurately predicts Qp:Qs. Stepwise multiple regression assessed the contributions of SaO2, SsvcO2, and SpvO2 to Qp:Qs determination. SaO2 correlated weakly with Qp:Qs (R2=0.08, P<0.05). Inclusion of SsvcO2 and SpvO2 improved Qp:Qs prediction accuracy. Pulmonary venous desaturation (SpvO2 <95%) was observed frequently (30%), especially at FiO2 </=0.21, but normalized with higher FiO2 or PEEP in all patients. In 6 patients, FiO2 was increased incrementally from 0.17 to 0.50 to determine whether this was an effective means to manipulate Qp:Qs. Qp:Qs failed to change predictably with increased FiO2. In 5 of 6 patients, however, higher SpvO2 and SaO2 enhanced systemic oxygen delivery, as demonstrated by improvement in oxygen extraction.
  
  
  CONCLUSIONS
  SaO2 correlated poorly with Qp:Qs because of variability in SsvcO2 and SpvO2. A novel observation was that pulmonary venous desaturation occurred frequently early after Norwood palliation but normalized with higher FiO2 or PEEP. Because unrecognized pulmonary venous desaturation confounds p:s assessment and compromises SaO2 and oxygen delivery, judicious use of inspired oxygen and PEEP may be beneficial in selected patients early after Norwood palliation.
authors.affiliation: Divisions of Cardiology and Cardiothoracic Surgery, The Heart Center, Children's Hospital Medical Center, Cincinnati, Ohio 45229-3039, USA.
authors.forename: R
authors.initials: R
authors.lastname: Taeed
authors.forename: S M
authors.initials: SM
authors.lastname: Schwartz
authors.forename: J M
authors.initials: JM
authors.lastname: Pearl
authors.forename: J L
authors.initials: JL
authors.lastname: Raake
authors.forename: R H
authors.initials: RH
authors.lastname: Beekman
authors.forename: P B
authors.initials: PB
authors.lastname: Manning
authors.forename: D P
authors.initials: DP
authors.lastname: Nelson
mesh_terms: D006330:Heart Defects, Congenital / Q000097:blood / Q000503:physiopathology* / Q000601:surgery; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008168:Lung / Q000098:blood supply* / Q000503:physiopathology; D010092:Oximetry; D010100:Oxygen / Q000097:blood*; D010101:Oxygen Consumption; D010166:Palliative Care; D011184:Postoperative Period; D011652:Pulmonary Circulation
chemical_list: D010100:Oxygen