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Sequentially randomized designs are commonly used in biomedical research, particularly in clinical trials, to assess and compare the effects of different treatment regimes. In such designs, eligible patients are first randomized to one of the initial therapies, then patients with some intermediate response (e.g. without progressive diseases) are randomized to one of the maintenance therapies. The goal is to evaluate dynamic treatment regimes consisting of an initial therapy, the intermediate response, and a maintenance therapy. In this article, we demonstrate the use of pattern-mixture model (commonly used for analyzing missing data) for estimating the effects of treatment regimes based on familiar survival analysis techniques such as Nelson-Aalen and parametric models. Moreover, we demonstrate how to use estimates from pattern-mixture models to test for the differences across treatment regimes in a weighted log-rank setting. We investigate the properties of the proposed estimators and test in a Monte Carlo simulation study. Finally we demonstrate the methods using the long-term survival data from the high risk neuroblastoma study.

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BACKGROUND: Patients with end-stage heart failure possess many attributes that place them at risk for prolonged mechanical ventilation (MV). However, there are only limited data on MV support among children after ventricular assist device (VAD) implantation. We report the duration of MV after VAD placement, indications for respiratory support in the postimplantation period, and associated patient factors. METHODS: This single-center retrospective study included 43 consecutive children (aged <18 years) with end-stage heart failure who were supported with a VAD as a bridge to transplantation from January 2005 to December 2011. Multivariable analysis was performed using the multiple Poisson regression model for the duration of MV. RESULTS: Overall, 33% (n = 14) remained on MV until heart transplant or death. Of those requiring pre-VAD extracorporeal membrane oxygenation (ECMO) support, 63% (n = 12 of 19) remained on MV until heart transplant or death compared with 8% (n = 2 of 24) among those not on ECMO before VAD (p < 0.001). Patients with moderate or severe mitral regurgitation while on VAD support had 1.7-times more MV days compared with those with none or trivial on-VAD mitral regurgitation. In addition, previous support on ECMO, those with moderate or severe tricuspid regurgitation, and those with only left VAD implants had an increased risk of prolonged MV. CONCLUSIONS: Our results suggest that VAD recipients previously supported on ECMO, those with moderate or severe mitral regurgitation, moderate or severe tricuspid regurgitation, and those with only left VAD implants had an increased risk of prolonged MV. Future studies in larger cohorts are necessary to confirm the findings from this single-institutional experience.

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STUDY OBJECTIVES: To describe characteristics and surgical and clinical outcomes of obese children with obstructive sleep apnea (OSA). METHODS: At our institution from 2000 to 2010, 143 obese children with an overnight polysomnography (OPSG) diagnosis of OSA, excluding children with comorbidities, were identified. Relationships between demographics, clinical findings, and the severity of OSA were assessed. Presurgery and postsurgery OPSG indices were compared. We defined cure as an apneahypopnea index (AHI) < 1.5/h on the postsurgery OPSG, and we compared the cure rates of different surgeries. RESULTS: A total of 143 children, median age 12.4 y (interquartile range [IQR] 9.6-14.9) and BMI z-scores 2.8 (IQR 2.6-2.9), were included. Seventy-eight (55%) (Median age 12 y [IQR 9-15]) underwent surgery: 1 had tonsillectomy; 1 tonsillectomy + uvulopharyngopalatoplasty (UPPP); 23 adenotonsillectomy (AT); 27 AT + UPPP; 11 adenoidectomy + UPPP; 8 UPPP; and 7 AT + turbinate trim ± tongue base suspension. Overall, surgery cured 19 children (26%), but AHI improved in the majority of children (p = 0.001). Similarly, the arousal index, PETCO2, and SpO2 nadir improved significantly (p < 0.002, p = 0.019, p < 0.001, respectively). AHI improved significantly in children with mild-to-moderate OSA in comparison to severe OSA (p < 0.001). Children with enlarged tonsils and no history of prior surgery benefitted more often from surgery (p < 0.004 and p = 0.002, respectively). AT was the only surgery reducing the AHI significantly (p = 0.008). Children did not lose weight despite intervention. Adherence with PAP was poor. CONCLUSIONS: Surgery improved OPSG indices in the majority of obese children with OSA.

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OBJECTIVES: Angiotensin converting enzyme inhibitors (ACEI) have been shown to decrease aortic growth velocity (AGV) in Marfan syndrome (MFS). We sought to compare the effect of ß-blockers and ACEI on AGV in MFS. STUDY DESIGN: We retrospectively reviewed all data from all patients with MFS seen at Arkansas Children's Hospital between January 1, 1976 and January 1, 2013. Generalized least squares were used to evaluate AGV over time as a function of age, medication group, and the interaction between the 2. A mixed model was used to compare AGV between medication groups as a function of age, medication group (none, ß-blocker, ACEI), and the interaction between the 2. RESULTS: A total of 67 patients with confirmed MFS were identified (34/67, 51% female). Mean age at first encounter was 13 ± 10 years, with mean follow-up of 7.6 ± 5.8 years. There were 839 patient encounters with a median of 10 (range 2-42) encounters per patient. AGV was nearly normal in the ß-blocker group, and was less than either the ACEI or untreated groups. The AGV was higher than normal in ACEI and untreated groups (P < .001 for both). CONCLUSIONS: ß-blocker therapy results in near-normalization of AGV in MFS. ACEI did not decrease AGV in a clinically significant manner.

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OBJECTIVE: To examine first the RBC transfusion practice in pediatric patients supported with extracorporeal membrane oxygenation and second the relationship between transfusion of RBCs and changes in mixed venous saturation (SvO2) and cerebral regional tissue oxygenation, as measured by near-infrared spectroscopy in patients supported with extracorporeal membrane oxygenation. DESIGN: Retrospective observational study. SETTING: Pediatric, cardiovascular, and neonatal ICUs of a tertiary care children's hospital. PATIENTS: All pediatric patients supported with extracorporeal membrane oxygenation between January 1, 2010, and December 31, 2010. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: There were 45 patients supported with extracorporeal membrane oxygenation. The median (interquartile range) phlebotomy during extracorporeal membrane oxygenation was 75 mL/kg (33, 149 mL/kg). A total of 617 transfusions were administered (median, 9 per patient; range = 1-57). RBC volumes transfused during extracorporeal membrane oxygenation support were 254 mL/kg (136, 557) and 267 mL/kg (187, 393; p = 0.82) for cardiac and noncardiac patients, respectively. Subtracting the volume of RBCs used for extracorporeal membrane oxygenation circuit priming, median RBC transfusion volumes were 131 and 80 mL/kg for cardiac and noncardiac patients, respectively (p = 0.26). The cardiac surgical patients received the most RBCs (529 vs 74 mL/kg for nonsurgical cardiac patients). The median hematocrit maintained during extracorporeal membrane oxygenation support was 37%, with no difference between cardiac and noncardiac patients. Patients supported with extracorporeal membrane oxygenation were exposed to a median of 10.9 (range, 3-43) individual donor RBC units. Most transfusions resulted in no significant change in either SvO2 or cerebral near-infrared spectroscopy. Only 5% of transfusions administered (31/617) resulted in an increase in SvO2 of more than 5%, whereas an increase in cerebral near-infrared spectroscopy of more than 5 was only observed in 9% of transfusions (53/617). Most transfusions (73%) were administered at a time when the pretransfusion SvO2 was more than 70%. CONCLUSIONS: Patients supported with extracorporeal membrane oxygenation were exposed to large RBC transfusion volumes for treatment of mild anemia resulting from blood loss, particularly phlebotomy. In the majority of events, RBC transfusion did not significantly alter global tissue oxygenation, as assessed by changes in SvO2 and cerebral near-infrared spectroscopy. Most transfusions were administered at a time at which the patient did not appear to be oxygen delivery dependent according to global measures of tissue oxygenation.

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OBJECTIVE: To identify the characteristics of children with cystic fibrosis with low initial forced expiratory volume in 1 second (FEV1) % predicted and to investigate their outcome. STUDY DESIGN: Patients were categorized into low or high initial FEV1 groups using cluster analysis. Comparisons of the demographic and clinical data were performed between the 2 groups. RESULTS: From 122 children, 21 clustered into the low and 101 into the high FEV1 group. The mean FEV1 was 69% ± 12% predicted for the low and 95% ± 12% predicted for the high FEV1 group (P < .001). The low FEV1 group had lower body mass index percentiles (P = .003), were hospitalized more frequently (P = .001), and had been on dornase alfa longer (P = .006). Low FEV1 group had more patients with positive cultures for Pseudomonas aeruginosa (P = .002) and Stenotrophomonas maltophilia (P < .001) and had more total number of cultures positive for mucoid P. aeruginosa (P = .009) and methicillin resistant Staphylococcus aureus + P. aeruginosa (P = .005). The low FEV1 group continued to have low FEV1 measurements, their FEV1 declined slower, required more hospitalizations per year (P = .01), and had more cultures for mucoid (P = .003) and nonmucoid P. aeruginosa (P = .02) ± methicillin resistant S. aureus (P = .002) in comparison with the high FEV1 group. Poor adherence was associated with lower initial FEV1 values in females, and early, rapid decline of FEV1 in males. CONCLUSIONS: Some children with cystic fibrosis may present with poor lung function early in life and continue to have subnormal lung function associated with reduced body mass index, more frequent hospitalization, and higher rates of infection. Such children may benefit from careful evaluation and close follow-up.

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