Efficacy of Flow Monitoring During ECMO.

The hypothesis that blood flow monitoring could serve as an effective early indicator of distal obstruction during extracorporeal membrane oxygenation (ECMO) was tested under controlled experimental conditions. The ECMO circuit typically includes (or could be easily modified to include) a shunt that bifurcates from the main line returning a small amount of blood to the pump with access points for drug infusions. Distal circuit obstructions in the oxygenator and beyond will result in an increased diversion of flow from the distal line to the shunt. Thus, elevations in flow through the shunt can serve as a marker for distal circuit obstruction. An ECMO training circuit was adapted with a resistance chamber that simulates controlled and varying levels of distal obstructions. Experiments were conducted under pediatric and adult pump target flow rates simulating different levels of distal obstructions while documenting the shunt flow and pressure drop across the obstruction. There was measurable and statistically significant elevation in the shunt flow at all flow rates because of different levels of obstruction from baseline values and hence consistent with the hypothesis that shunt flow can serve as an indicator of distal obstruction in the ECMO circuit. Flow monitoring is over the tube, hands free, continuous, and easy to implement. Therefore, it has the potential to serve as an early nonspecific indicator of elevated distal resistance in the ECMO circuit, which can then trigger other measurements (such as pressure drop across the oxygenator) for a more specific assessment of the source for distal resistance.

Phlebotomy-induced anemia alters hippocampal neurochemistry in neonatal mice.

BACKGROUND: Phlebotomy-induced anemia (PIA) is common in preterm infants. The hippocampus undergoes rapid differentiation during late fetal/early neonatal life and relies on adequate oxygen and iron to support oxidative metabolism necessary for development. Anemia shortchanges these two critical substrates, potentially altering hippocampal development and function. METHODS: PIA (hematocrit <25%) was induced in neonatal mice pups from postnatal day (P)3 to P14. Neurochemical concentrations in the hippocampus were determined using in vivo (1)H NMR spectroscopy at 9.4T and compared with control animals at P14. Gene expression was assessed using quantitative real-time polymerase chain reaction (qRT-PCR). RESULTS: PIA decreased brain iron concentration, increased hippocampal lactate and creatine concentrations, and decreased phosphoethanolamine (PE) concentration and the phosphocreatine/creatine ratio. Hippocampal transferrin receptor (Tfrc) gene expression was increased, while the expression of calcium/calmodulin-dependent protein kinase type IIα (CamKIIα) was decreased in PIA mice. CONCLUSION: This clinically relevant model of neonatal anemia alters hippocampal energy and phospholipid metabolism and gene expression during a critical developmental period. Low target hematocrits for preterm neonates in the neonatal intensive care unit (NICU) may have potential adverse neural implications.