ECMO-/ECLS

prognostic data are not yet available. The main limitation is the local
measurement of oxygenation. If the catheter is not placed into the area of injury,
the data may not correlate with metabolic activity in the zone of injury.
Furthermore, it remains unclear whether such monitors should be placed in the
area of injury, the penumbra (area around injury at risk for spread of damage), or
in a distant site.
Cerebral microdialysis (CMA microdialysis catheter) is a new technology
that measures brain tissue metabolites as a marker of perfusion allowing
metabolic-directed therapy. Normative values are being developed and are not
yet prognostic. A microcatheter placed into the brain parenchyma can measure
cerebral glucose, lactate, pyruvate, glutamate, aspartate, and glycerol. Differing
ratios in measured diasylate concentrations are thought to reflect altered
substrate delivery and/or substrate utilization. This methodology again only
measures the local effects in the tissue where the catheter is placed.
Near Infared Spectroscopy (NIRS) measures the difference in transmitted
and measured light at specific wavelengths. The NIRS transducer
emits/transmits light through the cerebral tissue and measures light as it exits
tissue, allowing measurement of tissue oxygenation deeper than cutaneous
pulse-oximetry. Similar to other technologies, NIRS is limited by its ability to
interrogate individual locations, though in principle it may be applied to multiple
sites simultaneously. Furthermore, the application of a flank sensor (measuring
renal/somatic perfusion) allows comparison of cerebral and somatic perfusion.