Anesth Analg 2007;104:1012-1014
© 2007 International Anesthesia Research Society
doi: 10.1213/01.ane.0000263281.45718.e4
EDITORIAL
Should All Patients Undergoing Cardiac Surgery Have Preoperative Psychometric Testing: A Brain Stress Test?
Charles W. Hogue, MD*,
Ola A. Selnes, PhD , and
Guy McKhann, MD
From the Departments of *Anesthesiology and Critical Care Medicine and Neurology, The Johns Hopkins Hospital, Baltimore, Maryland.
Address correspondence to Charles W. Hogue, MD, Department of Anesthesiology and Critical Care Medicine, 660 N. Wolfe St, Tower 711, Baltimore, MD 21287, (410) 614-1516. Address e-mail to chogue2{at}jhmi.edu.
Neurological sequelae from cardiac surgery has been the focus of several investigations over the last four decades outlining clinical manifestations, accompanying mortality, health care costs, and the importance for quality of life associated with these conditions (1,2). A particular focus has been on postoperative cognitive decline, the most frequent neurological complication after cardiac surgery, affecting approximately 30%–40% of patients during the first few weeks after surgery. Although the exact etiology of postoperative cognitive dysfunction is not known, susceptibility can be broadly categorized as resulting from patient-related and surgery-related factors. The latter include cerebral microembolism and cerebral hypoperfusion exacerbated by other pathophysiological processes resulting from surgery including inflammation and hyperthermia (1,2). Atherosclerosis of the ascending aorta and cerebral arteries, genetic factors, and other traits are examples of factors that increase individual susceptibility for postoperative cognitive dysfunction (1,2).
In this issue of Anesthesia & Analgesia two articles underscore the high preoperative prevalence of cerebrovascular disease in candidates for cardiac surgery and its importance for postoperative neurological complications. Silbert et al. (3) report a retrospective observational study of 349 patients scheduled for coronary artery bypass (CABG) surgery without evidence of preoperative clinical stroke who underwent neuropsychological testing before surgery. A group of 170 nonhospitalized individuals matched for age and intelligence (two important determinants of psychometric test performance) free of known cardiovascular disease served as controls. The CABG surgery patients performed significantly worse (score  2 SD below mean results) than the controls on all tests except for a measure of motor speed (Grooved Peg Board, nondominant hand). Cognitive impairment (defined as impairment on two or more neuropsychological tests) was found in 35% of CABG surgery patients before their procedure.
Goto et al. (4) studied 720 patients undergoing CABG surgery to assess gender differences in risk factors for neurological complications. Our group has previously found in single and multicenter studies that female gender is an independent predictor of perioperative stroke (5,6). The study by Goto et al. (4) is unique, in that all patients underwent brain magnetic resonance imaging (MRI) and angiography to assess for cerebral infarctions, carotid artery stenosis, and intracranial arterial stenosis. Several groups (2) have now reported studies where brain MRI is performed before surgery, but the study by Goto et al. (4) is the largest to date. A notable finding of these studies is that more than 40% of patients undergoing cardiac surgery have evidence of prior brain infarction that are usually clinically asymptomatic and that are associated with risk for perioperative neurological complications.
Goto et al. (4) found no difference in the frequency of prior cerebral infarction or preoperative cognitive impairment between genders (51% of men and 23% of women). The authors used only a broad measure of cognitive performance (Hasegawa dementia scale) and not a full neuropsychological test battery. The definition of cognitive impairment was based on comparison with normative data derived from community dwelling individuals. The small sample size and limited neuropsychological testing, thus, does not exclude a type II error in their results. Of interest, though, was the finding that men and women had different prevalence of atherosclerotic risk factors: men were more likely to have severe carotid artery stenosis, severe aortic atherosclerosis (assessed with epiaortic ultrasound), and peripheral vascular disease, whereas women were more likely to have hypertension and intracranial arterial stenosis. A relationship was found between preexisting cognitive impairment, prior cerebral infarction, and atherosclerosis of the ascending aorta with perioperative stroke, but only the latter two variables were significant predictors after statistical adjustment with multivariate logistic regression analysis. There was a correlation between cerebrovascular atherosclerosis and age and other vascular disease risk factors.
It is well established that patients burdened with widespread cardiovascular disease often have "silent" brain infarctions and other degenerative disease of the central nervous system associated with cognitive impairment (7,8). The studies by Silbert et al. (3) and Goto et al. (4) thus do not provide unexpected results in this regard. However, a potentially important implication of these findings is that the presence of preexisting cognitive impairment may decrease the sensitivity of psychometric testing because of the "basement effect" as we and others have reported (9). That is, low baseline cognitive performance may mean that an affected individual may not demonstrate a large enough decrement in psychometric testing results after surgery to meet a dichotomous definition of cognitive dysfunction. In such patients, even a small degree of further deterioration in cognitive performance, though, may have a large impact on their quality of life, yet they may be incorrectly labeled as not suffering postoperative cognitive dysfunction.
The studies by Silbert et al. (3) and Goto et al. (4) raise perhaps more interesting questions on how to approach an aging cardiac surgical patient population with limited cerebral reserve. First, should we consider preoperative psychometric testing to identify patients with cerebrovascular disease? We know that these conditions often go unrecognized with routine physical examination and diagnostic evaluations, yet the presence of "subclinical" large or small vessel brain infarction is an important predictor of stroke and postoperative cognitive impairment. Psychometric testing has a long track record for detecting neurologic dysfunction from a variety of causes that predates contemporary brain imaging studies. The testing thus might uncover prognostically important neurological impairment that would otherwise go undetected. There are multiple issues that would first need to be assessed in clinical investigations in addition to the effectiveness of such screening across a wide array of academic, government, and community practices of varying size and in different countries. If found reliable, preoperative neuropsychological evaluation might, in fact, be cost-effective if more accurate patient risk assessment and better planning for perioperative management results. Another consideration, though, is that advances in cardiac computed tomography and MRI might well lead to these diagnostic tests becoming more widespread in the future rather than current coronary angiographic-based studies. Simply obtaining imaging of the brain after cardiac imaging might be economically and logistically feasible. Either approach, of course, will await further studies that provide evidence-based guidelines derived from multicenter studies on effective neuroprotective strategies (e.g., "on" versus "off" pump surgery, "higher" hematocrit and arterial blood pressure targets during cardiopulmonary bypass, epiaortic ultrasound scanning, near infrared spectroscopy monitoring, etc) (2).
A second and perhaps larger question raised by the studies by Silbert et al. (3) and Goto et al. (4) is who should be the controls for neuropsychological studies for patients undergoing cardiac surgery? Ideally, the controls would need to have similar demographic characteristics such as age, gender, education and premorbid IQ. In our own prospective studies, we have used nonsurgical controls with coronary artery disease documented by cardiac catheterization (10). We have demonstrated that at baseline, the cognitive test performance of the CABG candidates and controls with cardiovascular disease is quite similar in most cognitive domains. However, by comparison with the psychometric performance of controls without known risk factors for cardiovascular disease, their scores are significantly lower. One can argue therefore, that the use of controls with cardiovascular disease will under-estimate the degree of preexisting cognitive impairment. A group of demographically matched community-dwelling individuals, unselected for presence or absence of coronary artery disease, may therefore be a more reasonable choice of controls.
In most contemporary studies of the effects of cardiac surgery on cognition, a control group is not included. Rather, patients serve as their own controls using arbitrary "cut-offs" from baseline to define cognitive decline after surgery. Limitations to this approach have been widely reported and editorialized (11–14). Using arbitrary cutoffs to quantify cognitive impairment fails to consider the inherent variability of psychometric retesting (11–14). The frequency of cognitive impairment can vary 30-fold, depending on the definition, and it can even be found spuriously in healthy controls when the psychometric tests are repeated after only a few weeks. Further, when tracking changes in cognitive function over time, the natural history of decline because of preexisting cerebral disease is not considered (10,11). Thus, whether an individual is simply on their expected "curve" of decline in cognitive performance (explained by cerebrovascular disease regardless of surgery), or whether a new slope of decline resulted from surgery is often unknown.
The reports by Silbert et al. (3) and Goto et al. (4) help to highlight important considerations in detecting neurological complications from cardiac surgery. The growing presence of cerebrovascular disease in patients undergoing cardiac surgery will challenge both clinicians and investigators. An assessment of cerebral reserve before surgery may well allow more appropriate selection of surgical candidates and/or a more focused perioperative plan for limiting brain injury.
 |
Footnotes
|
|---|
Accepted for publication January 23, 2007.
Supported in part by a grant from the National Institutes of Health to Dr. Hogue (NHLBI 64600).
Dr. Charles Hogue, Associate Editor-in-Chief for Cardiovascular Anesthesia, was recused from all editorial decisions related to this manuscript.
|
REFERENCES
|
|---|
- Selnes OA, Goldsborough MA, Borowicz LM, McKhann GM. Neurobehavioural sequelae of cardiopulmonary bypass. Lancet 1999;353:1601–6.[Web of Science][Medline]
- Hogue CW Jr, Palin CA, Arrowsmith JE. Cardiopulmonary bypass management and neurologic outcomes: an evidence-based appraisal of current practices. Anesth Analg 2006;103:21–37.[Abstract/Free Full Text]
- Silbert BS, Scott DA, Evered LA, et al. Pre-existing cognitive impairment in patients for elective coronary artery bypass graft surgery. Anesth Analg 2007;104:1023–8.[Abstract/Free Full Text]
- Goto T, Baba T, Ito A, et al. Gender differences in stroke risk among the elderly after coronary artery surgery. Anesth Analg 2007;104:1016–22.[Abstract/Free Full Text]
- Hogue CW Jr, Murphy SF, Schechtman KB, Dávila-Román VG. Risk factors for early or delayed stroke after cardiac surgery. Circulation 1999;100:642–7.[Abstract/Free Full Text]
- Hogue CW Jr, Barzilai B, Pieper KS, et al. Sex differences in neurologic outcomes and mortality after cardiac surgery: a Society of Thoracic Surgery National Database Report. Circulation 2001;103:2133–7.[Abstract/Free Full Text]
- Knopman D, Boland LL, Mosley T, et al; Atherosclerosis Risk in Communities (ARIC) Study Investigators. Cardiovascular risk factors and cognitive decline in middle-aged adults. Neurology 2001;56:42–8.[Abstract/Free Full Text]
- Breteler MM, Claus JJ, Grobbee DE, Hofman A. Cardiovascular disease and distribution of cognitive function in elderly people: the Rotterdam Study. BMJ 1994;308:1604–8.[Abstract/Free Full Text]
- Hogue CW Jr, Hershey T, Dixon D, et al. Pre-existing cognitive impairment in women prior to cardiac surgery and its relation with C-reactive protein concentrations. Anesth Analg 2006;102:1602–8.[Abstract/Free Full Text]
- Selnes QO, Grega MA, Borowicz LM Jr, et al. Cognitive outcomes three years after coronary artery bypass surgery: a comparison of on-pump coronary artery bypass graft surgery and nonsurgical controls. Ann Thorac Surg 2006;82:388–90.[Free Full Text]
- Selnes OA, Pham L, Zeger S, McKhann GM. Defining cognitive change after CABG surgery: decline versus normal variability. Ann Thorac Surg 2006;82:388–90.[Free Full Text]
- Mahanna EP, Blumenthal JA, White WD, et al. Defining neuropsychological dysfunction after coronary artery bypass grafting. Ann Thorac Surg 1996;61:1342–7.[Abstract/Free Full Text]
- Keizer AM, Hijman R, Kalkman CJ, et al. The Octopus Study Group. The incidence of cognitive decline after (not) undergoing coronary artery bypass grafting: the impact of a controlled definition. Acta Anaesthesiol Scand 2005;49:1232–5.[Web of Science][Medline]
- Lewis M, Maruff P, Silbert B, et al. The detection of postoperative cognitive decline following coronary artery bypass graft surgery is affected by the number of neuropsychological tests in the assessment battery. Ann Thorac Surg 2006;81:2097–104.[Abstract/Free Full Text]
This article has been cited by other articles:
|
|
|
|
 
R. Gottesman and C. W. Hogue
Invited Commentary
Ann. Thorac. Surg.,
March 1, 2008;
85(3):
870 - 871.
[Full Text]
[PDF]
|
|
|
|
Top
REFERENCES
