Limitations of Study
PD
MULTIPLE ORGAN FAILURE, RECRUITMENT, POST CARDIAC SURGERY
The numbers were small; recruitment was high in the first part of the study, when most patients were entering the control phase, but diminished as the study progressed when sites were enrolling babies into the intervention phase. The study faced several challenges to delivery: three pauses due to technical problems with consumables that required resolution by the manufacturers and then the moratoria on non-COVID-19 research lasting between 6 and 16 months (depending on the site) during the COVID pandemic. Even more difficult to quantify was the effect of reopening a study when PICU staff were described as exhausted, and units faced severe staffing shortages.There were missing and unobtainable data, especially for the primary outcome in the intervention group. We underestimated the effect of staff having to learn a new technology and do additional study tasks at the bedside; study financial provision of additional nursing did not translate directly to availability when needed. The number of control cases on PD compared with CVVH was higher than we had expected based on PICANet data. There was an unanticipated need for additional circuits and frequent filter changes due to filter “sludging” (not clotting), which particularly seemed to affect very sick babies. This prevented completion of some studies. These observations add vital information to support our proposed redesign of the filter housing to reduce baseline-operating pressure. This may also have affected willingness to use of NIDUS in some situations. It should also be remembered that the primary outcome is a measure of the performance of the RRT modality—how well it delivers the prescribed UF rate—and is not closely related to the condition of the patient. Consequently, we believe that the failure to collect UF data from 14 patients in the intervention group has not led to important bias.Many babies requiring RRT in PICUs are critically unwell, as reflected by the vast majority in I-KID having multiple organ failure; most were on positive pressure ventilatory support. There was a very high use of inotrope infusions, and this may reflect a tendency for “routine use” in babies post cardiac surgery. In retrospect, we did not collect sufficient data on indications for use nor of the details of fluid bolus administration, or of the volumes of blood transfusions.