Is Indexed Preoperative Superior Vena Cava Blood Flow a Risk Factor in Patients Undergoing Bidirectional Cavopulmonary Shunt?

Abstract

This study evaluated the effect of a new measurement-superior vena cava (SVC) flow-and anatomic factors on postoperative arterial oxygen saturation and clinical outcome in patients who underwent bidirectional cavopulmonary shunt (BCPS). We reviewed 19 patients who underwent a BCPS between January 2009 and May 2011 who also had SVC blood flow measurements. Median age was 6 months (range, 2 to 29 months). Body weight was 7.0 ± 1.7 kg. Bilateral SVCs were present in 4. SVC flow was measured at the time of BCPS by a Transonic flow probe (Transonic Systems Inc, Ithaca, NY). SVC flow, preoperative hemodynamics, pulmonary artery size, and clinical outcome were analyzed to determine risk for morbidity and death. Mean absolute and indexed pre-BCPS SVC flow was 0.65 ± 0.23 L/min and 1.63 ± 0.55 L/min/m(2) or 91.1 ± 30.8 mL/kg/min, respectively. In all but 1 patient, the SVC flow was increased after BCPS from 1.63 ± 0.55 to 1.99 ± 0.57 L/min/m(2) (p = 0.005). There was a significant positive correlation between pre-BCPS and post-BCPS SVC flow (r = 0.627, p = 0.029). Pulmonary artery size correlated with post-BCPS SVC flow (r = 0.560, p = 0.016). Two patients with preoperative SVC flow of below 1.0 L/min/m(2) died or required BCPS takedown. SVC size did not correlate with BCPS flow (r = 0.231, p = 0.356). Univariate analysis indicated pre-BCPS pulmonary artery pressure was a risk factor for low arterial oxygen saturation (≤ 75%) immediately after BCPS (p = 0.042) and at discharge (p = 0.030). A new indicator-low SVC flow, may be a marker for BCPS failure or death, suggesting that the SVC flow vs size is more important in predicting successful BCPS.