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SAMBA 2000
INTERVIEW WITH Dr. Terri Monk
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Introduction
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Dr. Kathryn McGoldrick: We're at the SAMBA annual meeting, speaking with Dr. Terri Monk, who is professor of anesthesiology at the University of Florida in Gainesville. Dr. Monk just gave a fascinating presentation on postoperative cognitive dysfunction and she's very graciously agreed to answer some of our questions.
During her presentation Dr. Monk pointed out that the whole issue of postoperative cognitive dysfunction implies a range of severity or manifestations ranging from temporary delirium to mild, transient neuropsychiatric impairment to more obvious, more prolonged, sometimes even permanent dementia.
Common in the Elderly
Dr McGoldrick: This seems to be very common in the elderly, and I was wondering, Dr. Monk, if you could hypothesize as to why the elderly seem to be more susceptible?
Dr. Terri Monk: Well, I think there's probably a lot of reasons for it. I think one thing we have to look at is the type of operations they're having. We don't know the etiology for post-op cognitive dysfunction, but it may be related not to the anesthetic itself, but the surgical procedures. There may be different etiologies for these occurrences at different ages. Also the central nervous system of the older person may be very different, they may have already had some small infarcts that predispose them to this type of problem. So the etiology really is not known, and I think we're at the very early stages in the development of this question. And right now we're asking does it occur. I think the two studies, the Williams-Russo study and also the ISPAC study by Mueller and Gravenstein, point to the fact that, indeed, this is a real problem, and it's more common in the elderly patient. But now we need to look at the patients who are at high risk and we need to characterize the injury. Is it emboli, is it the anesthetic technique? We don't know, but there's a lot of interesting questions to be answered.
Causes?
Dr McGoldrick: As you alluded to during your talk, I think in the past many of us sort of tacitly assumed that when an elderly person was impaired cognitively postoperative ly, there was a problem with oxygenation or with hypotension interoperatively. It seems that this isn't necessarily the case.
Dr. Terri Monk: The ISPAC study that was published in the Lancet in March of 1998 specifically looked at the question of, "is this problem related to hypoxemia and hypotension?" The primary hypothesis was that it was going to occur in patients who became hypotensive or hypoxemic. And in fact they looked at this in correlation and they found many of the patients in this study did have problems with hypoxemia and hypotension, but there was no correlation between these problems and the occurrence of post-op cognitive dysfunction. So I think we have to look beyond the obvious explanation for this problem and realize that it is a problem and there's a lot of research that needs to be done in this area.
Regional vs. General Anesthesia
Dr McGoldrick: It also seems that regional anesthesia may not necessarily be better than general anesthesia in this context. Is that correct?
Dr. Terri Monk: Yes, there is a study that I did not have time to mention today by Williams-Russo that was published in JAMA in the mid-1990's. She actually randomized patients who were having orthopedic surgery to either epidural or general and found a five percent incidence of late post-op cognitive dysfunction occurring at six months after surgery in each of these groups, and there was no improvement with regional as compared to general anesthesia. So that is also an obvious way to prevent the problem, but it doesn't appear that the type of anesthetic necessarily will change the outcome.
Prevention
Dr McGoldrick: Finally, just to finish up on this fascinating topic, do you have any thoughts on possible prevention or treatment in the future?
Dr. Terri Monk: Well, I think the first thing we have to do is find the high risk populations, and then, in these high risk populations, do some studies to look at the mechanism of injury. If it is an embolic phenomena, maybe we should talk about preoperative coumadinization of these patients, or possibly inserting filters. That would be very radical, but if it were going to prevent a long-term memory problem, it might be something we'd want to do. If it is a hypotension-type problem ,say for patients who are in setting positions, we might want to raise the levels of our transducers, not do hypotensive anesthesia on these patients, and ensure that their blood pressure remains at standard preoperative blood pressure level. We have to look at the etiology and attempt to determine that before we can figure out what the interventions ought to be, and I don't think it's one problem, I think it's a multitude of problems that are occurring in different operations and that we are going to have a lot of different steps we need to take to prevent this problem.
Conclusion
Dr McGoldrick: I know you're undertaking a prospective study looking at this very important issue and we wish you all the best and thank you very much for talking with us today.
Dr. Terri Monk: Thank you.
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