Acute Decompensation in Pediatric Cardiac Patients: Outcomes After Rapid Response Events.

OBJECTIVE: We studied rapid response events after acute clinical instability outside ICU settings in pediatric cardiac patients. Our objective was to describe the characteristics and outcomes after rapid response events in this high-risk cohort and elucidate the cardiac conditions and risk factors associated with worse outcomes. DESIGN: A retrospective single-center study was carried out over a 3-year period from July 2011 to June 2014. SETTING: Referral high-volume pediatric cardiac center located within a tertiary academic pediatric hospital. PATIENTS: All rapid response events that occurred during the study period were reviewed to identify rapid response events in cardiac patients. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: We reviewed 1,906 rapid response events to identify 152 rapid response events that occurred in 127 pediatric cardiac patients. Congenital heart disease was the baseline diagnosis in 74% events (single ventricle, 28%; biventricle physiology, 46%). Seventy-four percent had a cardiac surgery before rapid response, 37% had ICU stay within previous 7 days, and acute kidney injury was noted in 41% post rapid response. Cardiac and/or pulmonary arrest occurred during rapid response in 8.5%. Overall, 81% were transferred to ICU, 22% had critical deterioration (ventilation or vasopressors within 12 hr of transfer), and 56% received such support and/or invasive procedures within 72 hours. Mortality within 30 days post event was 14%. Significant outcome associations included: single ventricle physiology-increased need for invasive procedures and mortality (adjusted odds ratio, 2.58; p = 0.02); multiple rapid response triggers-increased ICU transfer and interventions at 72 hours; critical deterioration-cardiopulmonary arrest and mortality; and acute kidney injury-cardiopulmonary arrest and need for hemodynamic support. CONCLUSIONS: Congenital heart disease, previous cardiac surgery, and recent discharge from ICU were common among pediatric cardiac rapid responses. Progression to cardiopulmonary arrest during rapid response, need for ICU care, kidney injury after rapid response, and mortality were high. Single ventricle physiology was independently associated with increased mortality.

Neural Network Evidence for the Coupling of Presaccadic Visual Remapping to Predictive Eye Position Updating.

As we look around a scene, we perceive it as continuous and stable even though each saccadic eye movement changes the visual input to the retinas. How the brain achieves this perceptual stabilization is unknown, but a major hypothesis is that it relies on presaccadic remapping, a process in which neurons shift their visual sensitivity to a new location in the scene just before each saccade. This hypothesis is difficult to test in vivo because complete, selective inactivation of remapping is currently intractable. We tested it in silico with a hierarchical, sheet-based neural network model of the visual and oculomotor system. The model generated saccadic commands to move a video camera abruptly. Visual input from the camera and internal copies of the saccadic movement commands, or corollary discharge, converged at a map-level simulation of the frontal eye field (FEF), a primate brain area known to receive such inputs. FEF output was combined with eye position signals to yield a suitable coordinate frame for guiding arm movements of a robot. Our operational definition of perceptual stability was "useful stability," quantified as continuously accurate pointing to a visual object despite camera saccades. During training, the emergence of useful stability was correlated tightly with the emergence of presaccadic remapping in the FEF. Remapping depended on corollary discharge but its timing was synchronized to the updating of eye position. When coupled to predictive eye position signals, remapping served to stabilize the target representation for continuously accurate pointing. Graded inactivations of pathways in the model replicated, and helped to interpret, previous in vivo experiments. The results support the hypothesis that visual stability requires presaccadic remapping, provide explanations for the function and timing of remapping, and offer testable hypotheses for in vivo studies. We conclude that remapping allows for seamless coordinate frame transformations and quick actions despite visual afferent lags. With visual remapping in place for behavior, it may be exploited for perceptual continuity.