ULTIMATE COMPUTING - Quantum Consciousness Studies

150 Anesthesia: Another Side of Consciousness
tend to become dilated with progression to plane four. The fourth stage of
anesthesia is respiratory arrest and ensuing cardiovascular collapse. Muscles are
flaccid, and pupils are widely dilated. Death will occur if anesthetic depth is not
decreased from stage four (Grantham and Hameroff, 1985).
Because of the risks of anesthetic overdose and the variable requirements of
individual patients, anesthesiologists have sought methods to judge anesthetic
depth in addition to the clinical signs enumerated by Snow and Guedel. Since the
early 20th century, electroencephalography (EEG) has been recorded from
anesthetized patients. EEG waves recorded at the scalp are thought to emanate
from summated dendritic synaptic potentials (“dipole fields”) generated by
pyramidal cells of the cerebral cortex. Scalp potentials generally range from 10 to
200 microvolts, and in frequencies from several Hz to about 50 Hz. The
frequency spectrum of the EEG is usually divided into 4 major classifications,
delta: less than 4 Hz, theta: 4–8 Hz, alpha: 8–13 Hz, and beta: greater than 13 Hz.
Generally, power at higher frequency decreases as anesthetic depth increases.
Accordingly, efforts to derive an appropriate index of anesthetic depth have
included attempts to quantify an EEG frequency below which most EEG power
occurs. This involves a Fourier transform of raw EEG data into a
frequency/power spectrum. One example is “spectral edge,” the frequency below
which 95 percent of EEG power occurs (Rampil, 1981). As anesthetic depth
increases, spectral edge roughly decreases. Other attempts to quantitatively assess
EEG and anesthetic depth have included the plotting of EEG voltage in “phase
space,” yielding phase portraits and chaotic attractors. Phase space plotting
involves choosing an arbitrary “phase lag,” and plotting EEG amplitude at any
point in time against the amplitude at that particular time plus the phase lag. This
results in geometric phase portraits which may be analyzed for complexity, or
“dimensionality” on a continuum of order and chaos. As patients become more
anesthetized, the dimensionality of their EEG becomes more ordered, and less
chaotic (Figures 7.2 and 7.3, Watt and Hameroff, 1987). Consciousness may thus
be described as a manifestation of deterministic chaos somewhere in the
brain/mind.
In addition to observing activities of the brain, anesthesiologists must closely
monitor other physiological functions of their patients during and immediately
after surgery. Cardiovascular, pulmonary, neuromuscular, kidney, blood clotting,
and other factors are carefully followed. A variety of technological advances in
monitoring permit safer care of sicker patients for more complex procedures.
Future monitoring may utilize even more advanced technologies. One possible
example is the “biosensor” field effect transistors which are tiny membrane
covered chips which can detect a variety of ions, molecules, drugs or hormones.
Small enough to fit on the tip of a small catheter harmlessly inserted into a blood
vessel or tissue, these biosensors connected to a computer can yield “on-line”
monitoring of blood chemistry and many other functions. With the advent of
nanotechnology, even tinier, more profoundly sensitive biosensors will
materialize. The capability for monitoring nanoscale conformational dynamics of
neural proteins (telemetrically or via very small implants) will lead, not only to
more sensitive observation of brain function during anesthesia and surgery, but
perhaps eventually to the manipulation of consciousness.