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February 1999
Volume 63 |
Number 2
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| Does Anesthesia
Leave Some of Our Patients With Prolonged Postoperative Cognitive
Dysfunction? |
Joachim S. Gravenstein,
M.D.
We begin the era of the brain. The stage was set last year by
two important publications that focused on cognitive dysfunction
after anesthesia and surgery in the elderly. A clinical study
by Moller and coworkers appeared in The Lancet1
and Dodds and Allison published an excellent review article in
the British Journal of Anaesthesia.2
Because cognition may decline with advancing age, Moller et
al. studied some 1,200 patients who were 60 years of age and older,
assuming that if anesthesia and surgery did indeed affect mental
functions, it should be most readily detected in the elderly.
The investigators administered psychological tests before the
operation, within a week postoperatively and again approximately
three months later. In all patients, general anesthesia lasted
at least two hours. Cardiac and neurosurgical patients were excluded
as were patients who failed to meet the study criteria. Volunteers
of comparable age, but not undergoing surgical treatment, were
given the same psychological tests at the same intervals to serve
as controls.
The investigators detected new cognitive dysfunction in the
first postoperative week in some 25 percent of patients. After
approximately three months, close to 10 percent of patients showed
measurable cognitive dysfunction. This differed significantly
from the 3-percent decline in cognitive function observed in the
control population over the same time span. The data confirmed
the hypothesis that older patients were at greater risk; patients
over 70 years of age were twice (14 percent) as likely as those
in their 60s (7 percent) to show prolonged cognitive difficulties.
The authors rejected the hypotheses that hypoxemia or hypotension
during surgery or during the first three postoperative days can
be linked to postoperative cognitive dysfunction.
The review article by Dodds and Allison brings this study and
many others into focus. The authors cite 89 papers and discuss
the history of published concerns about cognitive difficulties
after anesthesia. Remarkably, such concerns were expressed with
growing frequency only in the last 50 years, perhaps triggered
by Bedford's report in 1955 in The Lancet that some elderly
patients develop dementia after general anesthesia.3
Dodds and Allison examined publications exploring the mechanisms
that might contribute to cognitive dysfunction after anesthesia,
among them: drug effects; physiologic changes during anesthesia
such as hypoxemia, hypotension and hypocarbia; neurotransmitters;
the cholinergic system; and genetic factors. They also reviewed
studies that failed to find prolonged postoperative cognitive
problems or that compared regional with general anesthesia. Dodds
and Allison concluded their review with the following categorical
statement: "There is no debate as to whether or not postoperative
cognitive deficit exists. It is common and persistent ..."
We may accept as inevitable the frequent psychological disturbances
that affect elderly patients in the early postoperative period.
Too many mechanisms come to mind: the slow elimination of central
nervous system-active drugs used during and after the anesthetic,
the effects of metabolic and hormonal disturbances, sleep deprivation,
pain and the disorienting effect of the strange hospital environment.
The observation, however, that many elderly patients and presumably
some younger adults as well show signs of cognitive disturbances
three or more months postoperatively present us with new and urgent
questions: How many of these disturbances fail to resolve with
time? Can such problems push some elderly patients prematurely
into dependency? Can we preoperatively identify patients at risk
for late postoperative cognitive disturbances? The literature
and common sense suggest that patients with pre-existing psychological
dysfunction are at higher risk. Can we prevent the problem with
the help of different perianesthetic measures? Are the problems
even related to anesthesia, or do they have to do with the impact
of hospitalization, drugs unrelated to anesthesia, disease processes
or changes in living brought about as a consequence of the surgical
disease? Whatever the answers to these questions, we should recognize
that there is no postoperative complication more frequent and
of longer duration than postoperative cognitive dysfunction in
the elderly.
Anesthesia is not limited to "putting them to sleep and waking
them up again." Over the years, anesthesiologists have assumed
responsibilities in the intensive care unit and for pain management
for all hospital patients. It is time for the specialty to become
actively involved wherever possible in preventing and treating
postoperative cognitive dysfunction. Such involvement will call
for research and active care of the affected patient.
We may draw a parallel to pain management. While we started
out treating only wound pain, we now treat pain of
many different origins. While we started out worrying only about
early postanesthetic confusion, we now should recognize that late
postoperative cognitive dysfunction demands our attention. At
this time, the ASA standards for care and monitoring do not even
mention the brain, the very organ we depress so skillfully to
relieve anxiety and pain. In the future, it is likely that ASA's
standards for care and monitoring will include statements about
our responsibilities in preventing postoperative dysfunction of
the central nervous system and, where that fails, in monitoring
and caring for patients with postoperative dysfunction of the
central nervous system.
References:
- Moller JT, Cluitmans P, Rasmussen LS, Houx P, et al. Long-term
postoperative cognitive dysfunction in the elderly: ISPOCD1
study. ISPOCD investigators. International Study of Post-Operative
Cognitive Dysfunction. Lancet. 1998; 351:857-861.
- Dodds C, Allison J. Postoperative cognitive dysfunction in
the elderly surgical patient. Brit J Anaesth. 1998; 81:449-462.
- Bedford PD. Adverse cerebral effects of anaesthesia on old
people. Lancet. 1955; 2:259-263.
Joachim S. Gravenstein, M.D., is a Graduate
Research Professor Emeritus, Department of Anesthesiology, Shands
Teaching Hospital, University of Florida, Gainesville, Florida.
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