• Comparison of Postoperative Respiratory Function in Neonates with Hypoplastic Left Heart Syndrome Following First Stage Palliation

      Pandurangi, Sindhu; The University of Arizona College of Medicine - Phoenix; Willis, Brigham (The University of Arizona., 2016-03-25)
      Purpose Available surgical procedures in the first stage of the palliation of hypoplastic left heart syndrome (HLHS) are currently the Norwood procedure with Blalock‐Taussing (BT) shunt, Norwood with a Sano shunt (5.0 mm right ventricular‐pulmonary artery conduit), or a hybrid procedure combining surgical pulmonary artery band placement and catheter‐based closure of the ductus arteriosus. Following any of the three procedures, it is necessary for patients to be mechanically ventilated for a period of time; however, little is known about the differences in pulmonary function and outcome among the three groups. Methods We conducted a retrospective chart review of 14 neonates who underwent stage 1 palliation for HLHS, by hybrid procedure or Norwood procedure with BT or Sano shunts, at Phoenix Children’s Hospital from September 2013‐December 2014. Demographic, hemodynamic, and outcome information was collected. Heart rate, respiratory rate, mean arterial pressure, end tidal carbon dioxide (ETCO2), cerebral and renal somatic oximetry, mean airway pressure, ratio of partial pressure of arterial oxygen to inspired oxygen (PaO2/FiO2), partial pressure of arterial carbon dioxide (PaCO2), dead space fraction (Vd/Vt), and dynamic compliance were measured preoperatively, postoperatively, and at multiple time points from 6 to 120 hours postoperatively. Respiratory data was collected using the NM3 monitor (Philips Respironics, Pittsburgh, PA). Outcome measures collected included maximum postoperative lactate, time to extubation, hospital length of stay, and mortality. Results Of the 14 patients, 7 received the Norwood with BT shunt, 5 received the Sano shunt, and 2 received the hybrid procedure. Through linear regression analysis of groups stratified by shunt size, we found that the Vd/Vt ratios of the Sano and 3.0 mm BT shunt groups were higher at earlier times points, but became indistinguishable by 48 hours postoperatively (p=0.02). Linear regression of the 3 surgical groups comparing Vd/Vt across all times points did not show any significant differences (p = 0.79). Linear regression of dynamic compliance among the three groups across all time points also was not significant (p = 0.72). No significant difference was observed in dynamic compliance across all time points when groups were stratified by shunt size (p = 0.33). Examining differences between BT and Sano groups at each time point from 0‐ 120 hours postoperatively using Mann Whitney U analysis did not reveal significance. Analysis of outcomes of length of mechanical ventilation (p=0.61), hospital length of stay (p =0.99), and mortality (p>0.99) also did not differ significantly among the 3 surgical groups. Conclusion Our study identified that the 3.0 mm BT and Sano shunt group had higher Vd/Vt ratios throughout the first 48 postoperative hours. No other differences were found in Vd/Vt or dynamic compliance when surgical groups or shunt sizes were compared. Despite the early differences noted, lack of differences in outcome measures suggests that these early differences have little influence on prognosis.
    • Identifying an Oxygenation Index Threshold for Increased Mortality in Acute Respiratory Failure

      Hammond, Brandon; The University of Arizona College of Medicine - Phoenix; Dalton, Heidi; Willis, Brigham (The University of Arizona., 2016-03-25)
      Objectives: To examine current oxygenation index (OI) data and outcomes using EMR data to identify a specific OI values associated with outcome. Methods: Retrospective review of electronic medical record (EMR) data for patients age 1 month ‐ 20 years mechanically ventilated for >24 hours in the PICU. Serial, average and maximum OI values were calculated. Length of mechanical ventilation, hospital stay and outcome were assessed. Results: OI was calculated on 65 patients from EMR data, of which 6 died (9.2%). The median maximum OI was 10 for all patients, 17 for non‐survivors (NS), and 8 for survivors (S), (p=0.14 via Wilcoxon rank‐sum test). Odds ratios (OR) indicated 2.1 times increase odds of death (p=.08), 95% confidence interval (0.89–5.03) for each one‐percent increase in maximum OI. Average OI OR also revealed 2.1 times increase in odds of death (p=.14), 95% confidence interval (0.77–5.48). ROC analysis indicated a higher discriminate ability for max OI (AUC = 0.68) than average OI (AUC = .58). OI cut points for mortality were established. Mortality was unchanged until max OI >17, for which mortality nearly tripled at a value of 18% versus 6‐7% for range 0‐17. Conclusions: Serial assessment of OI values may allow creation of alert values for increased mortality risk and aid in development of clinical decision rules. Consideration for escalation of therapies for respiratory failure such as high frequency ventilation or ECMO at lower levels of OI than historically reported may be warranted. This study also helps to validate prior reports that OI is useful as a severity score for clinical research and outcome prediction.