Perioperative Stroke, Encephalopathy, and Central Nervous System Dysfunction

Abstract

The leading cause of mortality in adult populations throughout the world is atherosclerosis, which results in cardiovascular and cerebrovascular complications and consumes substantive health care resources. The impact of atherosclerosis on patients undergoing surgery is also considerable, given the multiple stresses occurring during, and especially following, the surgical procedures, thereby precipitating vascular morbidity. Perioperative cerebrovascular morbidity and mortality occur in approximately 10% of the 600,000 patients who undergo cardiac surgery annually, consuming approximately $13 billion, which is expended on in-hospital, intensive care unit (ICU), and long-term specialized care for these neurological complications of stroke, encephalopathy, and cognitive dysfunction. Furthermore, risk of these outcomes will continue to increase as the surgical population ages. Principal among the etiologies of focal stroke and encephalopathy appear to be perioperative hypotension and precipitation of macroemboli and microemboli. As a result, new detection techniques for these events have been instituted, including (1) continuous hemodynamic monitoring, for detection of hypotensive episodes; (2) transesophageal echocardiography, for detection of aortic atherosclerosis, a potential source for emboli; and (3) transcranial Doppler sonography, for detection of cerebral emboli, as well as determination of cerebral blood flow. Recent large-scale multicenter studies have identified risk factors and indices for perioperative central nervous system (CNS) morbidity. Regarding therapy, a number of pharmacological approaches are currently under consideration; principal among these approaches are agents that can modulate the excitotoxic response, including glutamate receptor antagonists (NMDA, AMPA, metabotrophic), calcium channel blockers, free radical scavengers, and agents that modify the inflammatory white cell response. Although a number of laboratory, animal, and smaller clinical trials have been conducted, only one large-scale multicenter program to date has been conducted to assess the efficacy of adenosine modulation. These data, collected in more than 4,000 patients undergoing cardiac surgery, suggest that in addition to mitigation of myocardial injury, stroke also may be modulated by enhancing adenosine concentration in the area of cerebral ischemia. However, these preliminary findings must be validated in appropriately powered clinical trials. Finally, postoperative stroke and encephalopathy consume substantive resources, resulting in prolonged length-of-stay (17 days in-hospital 10 days for patients suffering Q-wavc infarction, vs 7 days for patients having no adverse outcome) and prolonged length-of-stay in the ICU following surgery (5 vs 3 vs 2 days, respectively). Hospital costs increase by approximately 3- to 4-fold in patients who suffer CNS outcomes following surgery. In conclusion, perioperative CNS morbidity and mortality is a critical problem that affects a substantial portion of the surgical population and consumes considerable health care resources. Over the next several years, attention must be focused on this important problem, and clinical and research resources should be redirected toward the solution of perioperative CNS morbidity.

Adverse Cerebral Outcomes after Coronary Bypass Surgery

“…They are also subject to marked hemodynamic fluctuations; cerebral embolization of atherosclerotic plaque, air, fat, and platelet aggregates; cerebral hyperthermia after the discontinuation of cardiopulmonary bypass; and other inflammatory and neurohumoral derangements associated with surgery. [1][2][3][4][5] Although cerebral complications are responsible for an increasing proportion of perioperative deaths, 6,7 their incidence and effects have not been rigorously investigated. The majority of studies have been performed only at one center, have enrolled a limited number of patients, or have been retrospective (all of which has resulted in substantial variability among findings).…”

“…3,4,8,9 Studies of perioperative stroke have not attempted to identify potentially reversible risk factors, nor have they examined the long-term impact of perioperative cerebral outcomes on the use of resources. 3,7,10 Our investigation was designed as a multi-institutional, prospective, observational study to determine the incidence of both stroke and encephalopathy after coronary-artery bypass graft (CABG) surgery, to identify the independent predictors of these cerebral outcomes, and to define their impact on the use of resources, as measured by the lengths of hospital stays and the need for intensive intermediate-or long-term care.…”

“…This finding supports the theory that most strokes are caused by large atherosclerotic emboli liberated by surgical manipulation of the aorta. 3,[15][16][17][18][19][20][21][22] In our study, proximal aortic atherosclerosis, detected by palpation, was found in approximately 12 percent of all patients and in 20 percent of patients у70 years of age. Moderate or severe atherosclerotic disease has been detected with ultrasonographic scanning in 14 to 20 percent of elderly patients.…”

“…These results emphasize the medical importance of adverse cerebral outcomes after CABG surgery; they have economic implications as well. 1,3,13 *History of carotid disease includes carotid bruit, stenosis, and carotid endarterectomy. Excessive alcohol consumption indicates hospitalization because of alcohol consumption or alcohol withdrawal.…”

“…Moderate or severe atherosclerotic disease has been detected with ultrasonographic scanning in 14 to 20 percent of elderly patients. 3,[23][24][25][26][27] Although palpation of the aorta is not as sensitive a measure as other techniques, such as echocardiography, the method is simple and can be used routinely to identify patients at risk and therefore to indicate alterations in surgical technique. Such alterations might include the adjustment of the site for aortic clamping and cannulation, to avoid atherosclerotic regions; the use of arterial conduits (e.g., internal thoracic or epigastric arteries) to avoid aortic anastomoses; the use of hypothermic fibrillatory arrest without clamping the aorta; or the use of hypothermic circulatory arrest, with replacement of the diseased aorta.…”