CPM Summer 2018 - 5

daup h i n c m s  .o
.o rg

Sometimes data can
be spurious. I guess
that's when the most
important machine,
the brain, takes over.
The oxygen concentration leaving the heart was fine since the
arterial oximeter on the finger was reading 100% with a stable
waveform. The starting hematocrit was 45% and we lost very little
blood so arterial oxygen content should be fine. The patient was
relaxed with neuromuscular blocking agents and the temperature
was normal so oxygen utilization was at basal rate. Even though I
couldn't directly measure cardiac output, the blood pressure and
heart rate were stable and normal in an individual with documented
normal heart function by preoperative echocardiography. However,
the venous saturation as extrapolated from the cerebral oximeter
reading (not a true mixed venous saturation) was trending into
the abnormally low range. That's all the moving parts of the Fick

equation. Cerebral blood flow is also altered by the amount of
carbon dioxide in the blood (PCO2) as well with lower levels of
PCO2 leading to less blood flow due to vessel construction. The
patient's ETCO2, however, which is a window into the PCO2
level was fine, in the mid 30s. With normal lung function, the
ETCO2 and PCO2 should correlate well. What to do now? I
did nothing but waited and within a few minutes the cerebral
oximeter reading returned to normal without any intervention.
Sometimes data can be spurious. I guess that's when the most
important machine, the brain, takes over. Education and acuity
leads to the ultimate processing of the data. Thankfully, we as
physicians still are required to use our brains to interpret more
and more data, as well as to assess the appropriateness of an
algorithm or protocol as it pertains to a particular patient; and
when to step away from one if the situation changes.
Our next great advancement in anesthesia care as a window into
all of medical care may be to streamline the data to only include
what is most important and let some devices and monitors go.
Furthermore, we need to continue to rely on the ultimate data
processor, our brains. No monitor and its abilities supersedes that
of a medical education and our ability to continue to learn and
to adapt to our changing medical world.

Central PA Medicine Summer 2018 5
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Table of Contents for the Digital Edition of CPM Summer 2018
