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A Pharmacologist discusses his experiences using BIS
Dr. Gilles Fraser is a pharmacologist and
Director of the Clinical Pharmacology Rotation for the internal
medicine and critical care/pulmonary fellowship programs at Maine
Medical Center in Portland. He is also a Fellow of the American
College of Critical Care Medicine. The Critical Care Unit at Maine
Medical Center has been using Aspect's BIS Monitor to guide sedation
in certain circumstances for about a decade.
Aspect:
What is the responsibility of a pharmacologist in the ICU?
GF: Clinical pharmacologists are relatively new to the ICU, and
we're still carving out our role there, but generally speaking I
oversee therapeutics in the ICU. I review each patient's lab work
and diagnosis with a view to optimizing their pharmacology. I work
closely with the doctors and nurses and help to insure that each
patient gets maximum benefit from the drugs used in their care while
minimizing the adverse effects of those drugs. Precision in drug
selection, dosing and administration can have a major impact on
patient outcomes.
Aspect: One of your principal concerns must be inappropriate sedation?
GF:
Absolutely. My overriding concern is to provide a humane environment
for the ICU patient. That means striving for maximum comfort with
minimal adverse effects.The ICU is a hostile environment in the
sense that patients are typically subjected to many unpleasant stimuli
- the insertion and removal of needles, tubes and other medical
devices. An undersedated patient in the ICU is typically an agitated
patient who may thrash about. This agitation and the associated
anxiety can stress the cardiovascular system and, in some cases,
lead to ischemic events. Highly agitated patients also pull out
needles and tubes they find uncomfortable. On the flip side, oversedated
patients can be hard to wean off various forms of life support which
has both clinical and economic consequences. For example, the longer
a patient is on a mechanical ventilator the more susceptible he
or she is to pneumonia and other respiratory ailments. And, obviously,
the longer patients have to remain in the ICU the more costly their
care. Both undersedation and oversedation can also lead to post-traumatic
stress disorder especially in patients with severe respiratory disease
who recall traumatic experiences, and if patients have no factual
recall of their ICU experience but delusional "memories"
remain intact.
Aspect: That brings us to how you use the BIS monitor in the ICU.
When do you use the BIS monitor?
GF: BIS has been of enormous value in assessing patients who, for
whatever reason, are not arousable. Evaluating the adequacy of sedation
in a responsive patient is relatively straight-forward because they
can tell you how they feel. In the non-arousable patient the challenge
is much greater. For example, a patient who is moderately to deeply
sedated may not look clinically different from a patient whose EEG
is flatline. This is where BIS is so valuable. It gives us information
about the level of consciousness that isn't available in any other
way and, therefore, helps us to appropriately titrate sedation for
the non-responsive patient.
Aspect: Are there times when you want a patient to be non-responsive?
GF: Yes, and this is another circumstance in which the BIS monitor
provides important clinical information. For example, in order to
adequately ventilate some patients we need to provide "therapeutic
paralysis" and we need to ensure sedation deep enough to prevent
awareness of the experience. Studies suggest that 18-30% of ICU
patients recall being paralyzed but being unable to speak, blink,
or complain while we are treating them! That's way too high. The
BIS monitor may help lower the rate of recall in patients who require
therapeutic paralysis. As I said, my mission is to make the experience
humane by maximizing comfort and minimizing suffering from the drugs
we use in the ICU. BIS is vital to that mission.
Aspect: Are there are other circumstances in which BIS is especially
useful in the ICU?
GF: In closed-head injury cases we often administer barbiturates
to help lower elevated intracranial pressure by slowing brain metabolism
resulting in a near iso-electric state. BIS helps us titrate the
medication to achieve this state in a much simpler way than relying
on a raw EEG alone.The use of BIS obviates the need for bulky EEG
equipment with its massive production of paper tracings and does
not require a trained neurologist for interpretation.
Aspect: Do you think you have tapped all of the BIS' potential in
the ICU environment?
GF: No. I think we're just beginning to exploit the potential of
BIS technology in the ICU and I'm very excited about it. At Maine
Medical Center we are embarking on a randomized trial using BIS
to look at a whole range of potential benefits.We will be assessing
patient recall at three points during their hospitalization and
at 60 days after discharge to see how use of BIS correlates with
emergence of post-traumatic stress disorder and recall of the ICU
experience.We'll be looking at the effect of sedation guided by
BIS on patient and family member satisfaction. And we'll be assessing
BIS in terms of cost-effectiveness, length of stay in the ICU and
length of ventilation in patients who require it. Using BIS in conjunction
with one's clinical impressions has enormous promise in ICU care.
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