To the Editor:
—The article by Williams-Russo et al. 1and the editorial by Raja and Haythornthwaite 2imply that hypotensive anesthesia for total hip replacement (THR) is safe in terms of long-term cognitive impairment. The editorial states that, “the lack of any short or long-term cognitive impairment in the study by Williams-Russo et al. with the use of hypotensive epidural anesthesia is encouraging,” and that, “no declines in cognitive function were found in an elderly nonrisk population.” In the Discussion, Williams-Russo et al. state that, “Complication rates after elective THR observed in the study of high-risk patients are similar to or lower than those of previous studies of elective hip and knee replacement in unselected patients receiving normotensive anesthesia.”
Unfortunately, this statement does not translate to the lack of any short-term or long-term cognitive impairment. Williams-Russo et al. cite their own previous work with bilateral total knee replacement that used the same battery of neuropsychological tests. 3The 1995 study showed that 5% of patients had “clinically significant cognitive impairment” at 6 months. In the Results, the authors included not only baseline, 1-week, and 6-months scores for each test, but also include the percentage of patients with a decline in score from the baseline that is worse than the minimally clinical important difference for that test, a difference that they had defined. This was most helpful when interpreting the data because the standard deviations of the means for the tests were very large. This clinical importance difference data were not included in their most-recent study in which, once again, the standard deviations are large in relation to the means, which make comparison extremely difficult. I would be interested in seeing this data (if available) and to know what percentage of patients in the hypotensive groups had clinically important cognitive impairment according to their previous definition, to compare this number with the 1995 incidence of 5%. Is this impairment similar or is it lower? Do the authors think that these patients did better than the patients in their previous study? If so, could they please comment on why this should be so?
The conclusion of Williams-Russo et al. that there was no difference in early and late-term cognitive, cardiac, and renal complications in elderly patients between the two hypotensive groups for THR seems appropriate, given the data that were presented. As for the safety of total joint replacement in terms of long-term cognitive impairment, as implied by Raja and Haythornthwaite’s editorial, a 5% incidence of this complication is hardly encouraging, regardless of whether the anesthetic is normotensive or hypotensive. If this incidence is lower with hypotensive anesthesia, this observation certainly deserves an explanation.