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a Section of Cardiothoracic Surgery, Yale University School of Medicine, New Haven, Connecticut
b Department of Preventive Medicine, Stony Brook University School of Medicine, Stony Brook, New York
Accepted for publication October 14, 2008.
* Address correspondence to Dr Elefteriades, Section of Cardiothoracic Surgery, 121 FMB, 333 Cedar St, New Haven, CT 06437 (Email: john.elefteriades{at}yale.edu).
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Abstract |
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 Top Abstract IntroductionPatients and MethodsResultsCommentReferences |
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Methods: A total of 29 patients (18 males, 11 females; age, 26 to 75 years; mean 52.6 years) whose jobs require high cognitive capability and who had undergone aortic surgery using DHCA (range, 17 to 54 minutes; mean arrest time, 27.4 minutes) at Yale-New Haven Hospital were retrospectively studied. These 29 patients represented the responders among 45 such patients to whom questionnaires were mailed. A control group of 21 high-cognitive patients (20 males, 1 female; ages, 36 to 77 years; mean, 54.7 years) who underwent aortic surgery without DHCA were surveyed as well. During surgery, DHCA was used as the sole means of cerebral protection. The head was packed in ice, and carbon dioxide flooding of the field was used in all cases. The ascending aorta was resected with an open distal anastomosis and a hemiarch or total arch replacement. A 21-part questionnaire (adapted from A.F. Jorm's Short Form IQCODE and supplemented by our own questions) was distributed postoperatively to subjects and to their informants (generally a spouse). A value of 3 on the questionnaire indicated "not much change" from preoperative status (1 indicated much worse and 5 indicated much improved).
Results: There were no statistically significant differences in any functional outcomes by study group (by patient: DHCA 3.01, control 3.09; by informant: DHCA 3.00, control 3.03; p > 0.05). Mean values of the outcomes for study groups and control subjects were essentially identical and quite close to 3 (the value assigned to "not much change") for overall score, for occupational score, and for memory-related score.
Conclusions: These data indicate that high-cognitive patients experienced very little cognitive change as a result of undergoing DHCA. Our assessment strongly supports the adequacy of straight DHCA as a cerebral protectant strategy during short- to moderate-duration circulatory arrest. We found excellent preservation of functional state and no difference from patients undergoing aortic surgery without DHCA.
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Introduction |
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This study takes a closer look at 29 patients of the 394 of our recent report whose professions required high cognitive levels (patients mentioned briefly in Table 3 of our 2007 paper [8]). The high cognitive variable was selected because the central nervous system is quite sensitive to ischemia, and much research has been centered on neurologic outcome after DHCA. High-cognitive professions were loosely defined, but were essentially limited to physicians, lawyers, doctorates, clergymen, artists, musicians, accountants, and managers. Our goal was to determine whether these professionals noted any difference in their cognitive ability at home or at work after aortic surgery with straight DHCA. We were especially interested in individuals with high cognitive requirements at work, as we anticipated that any substantive adverse effects of DHCA would be less able to "hide" in such individuals than in those with less cognitively demanding occupations. Also, we saw an opportunity to compare functional status with a group of patients undergoing ascending aortic replacement without DHCA. Patients were interviewed and completed a questionnaire. Spouses or relatives were used as additional informants to control for self-reporting bias. Patients and their informants, and a 21-patient control group, were given a 21-part questionnaire to determine whether DHCA had adversely affected their cognitive function. We looked at a variety of questions, including the following: Are the patients able to perform their jobs at the same high cognitive level as before surgery? Have people been pointing out abnormalities in patients' function that have started since surgery? Can the patients not perform tasks now that they could before? We believe that specific neuropsychiatric assessment using validated metrics will extend our understanding of any potential detrimental effects of DHCA beyond nonspecific clinical assessment during and after hospitalization.
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Patients and Methods |
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Patients
Forty-five high-cognitive patients in the above-specified categories, undergoing thoracic aortic surgery requiring circulatory arrest at Yale-New Haven Hospital, were identified among the 394 total patients who underwent DHCA, predominantly during a 5-year period. Twenty-nine patients (64% yield) and their informants responded, and are included in this study. Patients were operated on from 1993 to May 2006. There were 18 male and 11 female patients. Ages ranged from 25 to 75 years with a mean age of 52.6 years. The professions of patients were varied, but required high cognition to function (Table 1). With the exception of 1 patient who was treated for acute type A aortic dissection, all patients were treated for ascending or aortic arch aneurysm, or both. Of the 29 total patients in the DHCA group, 17 had root-sparing procedures (10 with aortic valve replacement, 7 without aortic valve replacement), 11 had root replacement procedures, and 1 had a valve-sparing procedure. For the distal anastomoses, 26 patients had hemiarch replacements and 3 had total arch replacements. The range of DHCA duration was 17 to 54 minutes, and mean DHCA duration was 27.4 ± 10 minutes. Clinical assessment of patients after surgery revealed that 2 patients had a seizure, and none experienced a clinical stroke. Ten patients had postoperative atrial fibrillation, and all patients were alive at the time of contact. The interviews were administered at a mean of 48 months from operation (range, 11 to 168 months).
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Importantly, the test does not discriminate based on years of education, and thus does not favorably bias our study cohort. Our test included Jorm's questions as well as 5 additional questions we compiled pertaining to the patients' behavior in their workplace. These additional questions required the patient and informant to comment on the patient's ability to communicate with others at work; to accomplish work at a normal speed; to accomplish work with a normal degree of efficiency; to produce quality work; and to generate creative ideas in the work environment. A key feature of the questionnaire asks the patient and informant to evaluate subjectively the patient's prospective memory as well (eg, going to store, getting in car and forgetting what they originally set out to do). In most cases, informants were the spouses of patients, but could be chosen at the discretion of the patient. Informants were an important part of the study as patients who are cognitively impaired may fail to evaluate correctly their own cognitive deficiencies [13]. Informants were used to provide a second opinion on the current cognitive functioning of the patient. Informants were asked to fill out a separate copy of the same questionnaire as the patients, answering the questions as they pertained to the patient from the informant's point of view.
Deep Hypothermic Circulatory Arrest Management
The head was packed in ice. No barbiturate coma was used during the operation. No electroencephalogram, sensory evoked potential, or jugular venous bulb oxygen saturation monitoring were used. No special glucose management techniques were applied. Deep hypothermic circulatory arrest management was by the Alpha-stat method. Aprotinin was our antifibrinolytic of choice at the time that these patients were operated on. The femoral artery was our cannulation site of choice; in the minority of patients with descending atheroma seen on intraoperative transesophageal echocardiography (performed routinely), we used the axillary artery. The mean core temperature (bladder) during DHCA was 19.0°C (range, 17.5° to 22°C). The maximum temperature gradient between perfusate and body temperature during rewarming was kept less than 10°C. Rewarming was taken to a temperature of 34° to 36°C. Patient body mass index ranged from 17.4 to 45 kg/m2 (mean, 27.5 kg/m2). The duration of DHCA is shown in the histogram in Figure 1. (Responders and nonresponders both had a preponderance of patients in the 25- to 29-minute DHCA category.) Neither duration of DCHA nor patient age was predictive of subsequent scores in neuropsychiatric testing. The non-DHCA patients were cooled to 26°C.
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Postoperative Follow-Up
All discharged patients were reevaluated in the office within 8 weeks postoperatively and screened for any gross neurologic sequelae or impaired mental or physical functioning.
Statistical Analysis
In addition to determining means of desired groups, Fisher's exact test was used to statistically compare DHCA versus non-DHCA and patients versus informants among a variety of cognitive outcomes. Probability values greater than 0.05 were considered to be statistically insignificant.
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Results |
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The questionnaire results are summarized in Figure 2. The mean value of the questionnaire grade for the DHCA group was 3, indicating "not much change" from the preoperative functional class. This was very similar to the value obtained for the control group, operated on without DHCA. Mean values of the outcomes for both study and control groups were very similar and quite close to 3 ("not much change"; Table 3). Three primary categories were analyzed: total responses to all questions, responses to the occupational or work-related questions, and responses to the memory-related questions. For both the total and occupational questions, responses were all greater than 3 ("not much change"). The memory-related questions produced responses that were slightly less than 3, with patient values at 2.96 ± 0.43 for those with DHCA and at 2.99 ± 0.25 for those without DHCA (not significantly different). It is interesting to note (see mean column in Table 3) that some patients, both DHCA and non-DHCA, reported better cognitive function (values greater than 3) after surgery than before. Multiple DHCA patients have spontaneously reported better cognitive function during their clinic visits compared with preoperatively.
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To examine the possibility of bias in responding, all 16 nonresponders in the DHCA group were contacted in person or by phone. There were no deleterious new job changes (retirement, termination, and so forth). A non-English primary language was the reason for noncompletion in multiple patients.
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Comment |
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Although some studies have investigated the clinical outcomes of DHCA, very few have studied the patients on a subjective level with quantitative techniques. Immer and colleagues [7] investigated quality of life after interventions on the thoracic aorta with DHCA by using the Short Form 36 Health Survey questionnaire. They concluded that quality of life in such patients is "fairly good" and "comparable to an age-matched standard population." Their favorable findings are fully consistent with the excellent function confirmed in our study. Our study may have been more sensitive to subtle neurologic deficits because we included a large number of questions gauging cognitive performance and we looked at high-cognitive professionals. Even in this group with demanding cognitive needs, functional preservation was excellent. Moreover, we compared the study group with a non-DHCA cohort undergoing less technically demanding operations. Again, even compared with this group with milder disease, no deficiencies attributable to DHCA were identified. Furthermore, in Immer's study, the Short Form 36 questionnaire does not as rigorously ask patients to compare their preoperative to postoperative status. Of the 36 questions in the Short Form questionnaire, only one asks patients to compare their current general health now to that of 1 year prior. Because all of our questions asked patients to specifically compare their preoperative to postoperative status, we gained more in-depth information about their perceptions of the overall surgical experience and quality of life before and after surgery.
Our results indicate that there was no significant difference in quality of work generated after surgery between patients who had DHCA and those without. This validates the initial motivation of this study, based on our clinical impression that DHCA did not seem to affect or bias patients' postoperative performance in their work field. It is interesting that the cognition scores in both groups were greater than 3, the value assigned "not much change" (ie, better function than preoperatively). It is also interesting that multiple responses of individual patients showed a score that indicated better cognition postoperatively than preoperatively (maximum column in Table 3).
Memory is often the main physiologic detriment anticipated in DHCA patients [14, 15], but our study found that memory (questions 6 through 12 on the questionnaire) was not significantly different in DHCA patients than in patients without DHCA. Memory scores were essentially identical between the DHCA and the control groups (Table 3) and reflected memory status essentially identical to the preoperative state. Like the other variables, memory scores did not significantly differ between patient or informant responses, or by age groups, sex, or DHCA duration.
Limitations
High cognitive designation
Our study has limitations. The assignment to a highly cognitive group (Table 1) is clearly somewhat arbitrary; on the other hand, most would agree that the patients assigned to this category cannot perform their work without excellent cognitive abilities.
Control group
Although there is no universally acknowledged control group for DCHA, we were pleased with our selection of a control population: patients who underwent ascending aortic surgery without DHCA. These patients were on bypass, and they had a graft placed. In other words, they had a similar operation, but without DHCA. The fact that their operations were shorter and simpler should bias against the relative safety of DHCA in this comparison. So, the equivalency in neuropsychologic outcome is strengthened by the choice of a control group who had a less extensive operation.
Retrospective nature of study
Another important issue is that the retrospective nature of this study precluded us from examining preoperative variables measuring patients' neuropsychological states. Weaknesses of Jorm's questionnaire, or of any informant-based scale, are that they can be biased by the current state of the informant and by the relationship between the informant and the patient. Jorm [12] reports that cognitive decline is perceived to be greater when the informant is anxious or depressed or when there is a poor relationship. This factor could lead to false exaggeration of any cognitive deficit. Despite this potential adverse bias, we still found excellent cognitive preservation.
Along the same lines, one could argue that this study is not as effective as a series of objective tests, rather, that it is based only on the subjective findings of two individuals, patient and informant. Although this is generally true, a study investigating the validity of Jorm's test was performed in which his questionnaire was compared with the findings of a battery of neuropsychological and psychological tests, clinical diagnosis of dementia, computed tomographic scan findings, and psychological characteristics of the individuals who acted as informants [16]. The study confirmed that both the IQCODE and the MMSE (Mini-Mental State Examination) act as similar indicators of cognitive impairment. However, the study noted that the IQCODE (on which our study is based) is advantageous over the MMSE because it is not affected by education or premorbid ability. On the other hand, the IQCODE may be contaminated by the fact that it is influenced by the affective state and personality of the subject, the affective state of the informant, and the quality of the relationship between the subject and the informant. Therefore, the study concludes, it is desirable to use both types of cognitive assessments [16]. In fact, there are inherent advantages to using the IQCODE over objective tests like the MMSE. Specifically, unlike the MMSE, the IQCODE is unaffected by premorbid ability and education [17].
Limitations of Jorm's questionnaire
We chose the Jorm test because of its extensive testing and validation in the field as well as its demonstrated immunity to educational bias. The questions are appropriate for postoperative cognitive decline. We thought that developing our own specific test would open our study to potential criticism about prior validation.
Nonresponders
Additionally, not all patients in either the DHCA or non-DHCA groups responded to our questionnaire. Our protocol allowed us to telephone patients who did not promptly mail back their responses. More than one telephone call to encourage questionnaire completion was not permitted, however, so as not to limit the patients' ability to opt out of the study. Some patients, on speaking to them by telephone, explained that they felt no different after surgery, but simply did not want to be part of the study. Four DHCA patients indicated they were fine but preferred not to take time for the questionnaire, and the remainder were alive and clinically well when seen in clinic, without obvious or expressed deficit or concern. All nonresponders were eventually contacted in person or by phone in the course of this study, permitting us to rule out any deleterious job changes in all the nonresponders. For 6 nonresponders, having a language other than English as their native tongue contributed to their nonresponse.
Spousal informants
It is important to recognize as well that, although spousal informants are usually aware of work-related issues, they are not often present directly in the workplace, so that their assessment of the patient's work capacity is indirect.
Short duration of deep hypothermic circulatory arrest in most patients
Finally, all patients in this study underwent efficient aortic replacement, with a mean arrest time of 27.4 minutes and no arrest time exceeding 54 minutes. The positive findings of this study should not be construed as validating DHCA as a means of brain preservation in complex or prolonged aortic replacements requiring extremely prolonged circulatory arrest time.
Conclusions
In conclusion, our detailed neuropsychiatric questionnaire assessment strongly supports the adequacy of straight DHCA as a cerebral protectant strategy. We found excellent preservation of functional state and no difference from patients undergoing aortic surgery without DHCA. This study was not intended to compare straight DHCA with other forms of cerebral protection in aortic surgery (specifically, antegrade or retrograde cerebral perfusion). This study does, however, find favorable results in the reported high-cognitive patients with DHCA as a sole means of brain preservation for short to moderate duration circulatory arrest in thoracic aortic surgery.
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References |
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