Predictors of cognitive decline following coronary artery bypass graft surgery

BACKGROUND: A significant number of patients develop cognitive impairment that persists for months following coronary artery bypass grafting (CABG) surgery. Our objectives were to identify patient-related risk factors, processes of care, and the occurrence of any perioperative complications associated with cognitive decline. METHODS: Nine hundred thirty-nine patients enrolled in the Processes, Structures, and Outcomes of Care in Cardiac Surgery study undergoing CABG-only surgery at 14 Veterans Administration medical centers between 1992 and 1996 completed a short battery of cognitive tests at baseline and 6-months post-CABG. The composite cognitive score was based on the sum of errors for each individual item in the battery. Multiple linear regression analyses were used to identify independent predictors of the 6-month composite cognitive score. RESULTS: In multivariable analyses, patient characteristics associated with cognitive decline included cerebrovascular disease (p = 0.009), peripheral vascular disease (p = 0.007), history of chronic disabling neurologic illness (p = 0.016), and living alone (p = 0.049), while the number of years of education (p = 0.001) was inversely related to cognitive decline. After adjustment for baseline patient risk factors, the presence of any postoperative complication(s) (p = 0.001) was also associated with cognitive decline while cardiopulmonary bypass time (p = 0.008) was inversely related to cognitive decline. CONCLUSIONS: Patients with noncoronary manifestations of atherosclerosis, chronic disabling neurologic illness, or limited social support are at risk for cognitive decline after CABG surgery. In contrast, more years of education were associated with less cognitive decline. Preoperative assessment of risk factors identified in this study may be useful when counseling patients about the risk for cognitive decline following CABG surgery.     

The impact of postoperative atrial fibrillation on neurocognitive outcome after coronary artery bypass graft surgery.

Neurocognitive decline is a continuing source of morbidity after cardiac surgery. Atrial fibrillation occurs often after cardiac surgery and has been linked to adverse neurologic events. We sought to determine whether postoperative atrial fibrillation was associated with postoperative cognitive dysfunction. Four-hundred-eleven patients were enrolled to receive a battery of neurocognitive tests both preoperatively and 6 wk after elective coronary artery bypass graft surgery. Neurocognitive test scores were separated into four cognitive domains, with a composite cognitive index (the mean of the four domain scores) determined for each patient at every testing period. Multivariable analysis controlling for age, years of education, diabetes mellitus, left ventricular ejection fraction, and preoperative atrial fibrillation compared the presence of postoperative atrial fibrillation with change in cognitive function. Three-hundred-eight patients completed both pre- and postoperative cognitive testing; 69 patients (22%) had postoperative atrial fibrillation. Those who developed atrial fibrillation showed more cognitive decline than those who did not develop postoperative atrial fibrillation (P = 0.036). Atrial fibrillation was associated with poorer cognitive function 6 wk after surgery. Although the mechanism of this association is yet to be determined, prevention of atrial fibrillation may result in improved neurocognitive function. IMPLICATIONS: Neurocognitive dysfunction is common after coronary artery bypass graft surgery. The relationship between atrial fibrillation and neurocognitive dysfunction has not been examined. Our study shows that postoperative atrial fibrillation is associated with neurocognitive decline.     

Neuropsychological functioning 3–5 years after coronary artery bypass grafting: does the pump make a difference?

Objective: Neurocognitive sequelae after coronary artery bypass grafting (CABG) are frequently reported. The present study investigated the possible difference between on- and off-pump CABG patients in a long-term perspective. Methods: We administered seven standardized neuropsychological tests 1 day before, 6 days after, 6 months after and 3–5 years after CABG. We measured intra-operative high intensity transient signals (HITS) as a reflection of embolic load by transcranial Doppler ultrasonography. Results: Of the 74 patients originally recruited, 54 of the patients (73%) (mean age 59 years ± 7.5 years) completed the neuropsychological battery. Cognitive decline was defined as 20% decline on two or more tests. Three to 5 years after the operation, 30% of the patients showed neurocognitive problems in domains of non-verbal immediate memory and attention, speed for visual search, visual attention and mental flexibility. Neither difference in frequency of cognitive dysfunction nor a difference in evolution over the 5 year time period between on- and off-pump patients was observed. No significant predictors for cognitive decline were found. Conclusions: Three to 5 years after the CABG surgery no difference in neurocognitive deficits is found between on- and off-pump CABG patients, indicating that the extracorporeal circulation (ECC) may not be the main cause of late neuropsychological decline.     

Evaluation of brain injury after coronary artery bypass grafting. A prospective study using neuropsychological assessment and diffusion-weighted magnetic resonance imaging.

OBJECTIVE: Neurocognitive dysfunction is a common complication after cardiac surgery with cardiopulmonary bypass (CPB). Studies using magnetic resonance imaging (MRI) have demonstrated that new focal brain lesions can occur after coronary artery bypass grafting (CABG), even in patients without apparent neurological deficits. Diffusion-weighted MRI is superior to conventional MRI and allows for sensitive and early detection of ischemic brain lesions. We prospectively investigated cerebral injury early and 3 months after CABG using diffusion-weighted MRI and related the findings to clinical data and neurocognitive functions. METHODS: Twenty-nine patients [67.6+/-8.6 (52-85) years, 5 females] undergoing elective CABG with CPB were examined before surgery, at discharge and 3 months after surgery. A battery of standardized neuropsychological tests and questionnaires on depression and mood were administered. Conventional and diffusion-weighted MRI of the brain was performed and new lesions were analyzed. Clinical characteristics, neuropsychological test performance and radiographic data were collected and compared. RESULTS: There was no major neurological complication after CABG. Thirteen patients (45%) exhibited 32 new ischemic lesions on postoperative diffusion-weighted MRI. The lesions were small, rounded and equally dispersed in both hemispheres. Eight patients had at least two lesions. At discharge, significant deterioration of neuropsychological performance was observed in 6 of the 13 tests compared to baseline assessment. By 3 months postoperatively, 5 of the 6 tests returned to preoperative levels. Verbal learning ability, however, remained impaired. The presence of new focal brain lesions was not associated with impaired neuropsychological performance. There was also no correlation between clinical variables, intraoperative parameters and postoperative complications and MRI findings. CONCLUSIONS: Although neurocognitive decline after CABG is mostly transient, memory impairment can persist for months. New ischemic brain lesions on postoperative diffusion-weighted MRI do not appear to account for the persistent neurocognitive decline.     

Prospective Randomized Trial of Normothermic versus Hypothermic Cardiopulmonary Bypass on Cognitive Function after Coronary Artery Bypass Graft Surgery

Background : Despite significant advances in cardiopulmonary bypass (CPB) technology, surgical techniques, and anesthetic management, central nervous system complications occur in a large percentage of patients undergoing surgery requiring CPB. Many centers are switching to normothermic CPB because of shorter CPB and operating room times and improved myocardial protection. The authors hypothesized that, compared with normothermia, hypothermic CPB would result in superior neurologic and neurocognitive function after coronary artery bypass graft surgery.

Methods : Three hundred patients undergoing elective coronary artery bypass graft surgery were prospectively enrolled and randomly assigned to either normothermic (35.5-36.5[degrees]C) or hypothermic (28-30[degrees]C) CPB. A battery of neurocognitive tests was performed preoperatively and at 6 weeks after surgery. Four distinct cognitive domains were identified and standardized using factor analysis and were then compared on a continuous scale.

Results : Two hundred twenty-seven patients participated in 6-week follow-up testing. There were no differences in neurologic or neurocognitive outcomes between normothermic and hypothermic groups in multivariable models, adjusting for covariable effects of baseline cognitive function, age, and years of education, as well as interaction of these with temperature treatment.     

Prospective randomized trial of normothermic versus hypothermic cardiopulmonary bypass on cognitive function after coronary artery bypass graft surgery.

BACKGROUND: Despite significant advances in cardiopulmonary bypass (CPB) technology, surgical techniques, and anesthetic management, central nervous system complications occur in a large percentage of patients undergoing surgery requiring CPB. Many centers are switching to normothermic CPB because of shorter CPB and operating room times and improved myocardial protection. The authors hypothesized that, compared with normothermia, hypothermic CPB would result in superior neurologic and neurocognitive function after coronary artery bypass graft surgery. METHODS: Three hundred patients undergoing elective coronary artery bypass graft surgery were prospectively enrolled and randomly assigned to either normothermic (35.5-36.5 degrees C) or hypothermic (28-30 degrees C) CPB. A battery of neurocognitive tests was performed preoperatively and at 6 weeks after surgery. Four distinct cognitive domains were identified and standardized using factor analysis and were then compared on a continuous scale. RESULTS: Two hundred twenty-seven patients participated in 6-week follow-up testing. There were no differences in neurologic or neurocognitive outcomes between normothermic and hypothermic groups in multivariable models, adjusting for covariable effects of baseline cognitive function, age, and years of education, as well as interaction of these with temperature treatment. CONCLUSIONS: Hypothermic CPB does not provide additional central nervous system protection in adult cardiac surgical patients who were maintained at either 30 or 35 degrees C during CPB.     

Comparison of neurocognitive results after coronary artery bypass grafting and thoracic aortic surgery using retrograde cerebral perfusion.

OBJECTIVE: Retrograde cerebral perfusion (RCP) is used as an adjunctive method to hypothermic circulatory arrest to enhance cerebral protection in patients undergoing thoracic aortic surgery. It remains unclear whether RCP provides improved neurological and neuropsychological outcome. METHODS: Forty-six patients undergoing thoracic aortic surgery using RCP, and 28 undergoing coronary artery bypass grafting (CABG; n = 28) with CPB, were enrolled in the study. Patients receiving RCP were subdivided into two groups, those with less than 60 min of RCP (S-RCP; n = 27) and with 60 min or more (L-RCP; n = 19). The patients' neurocognitive state was assessed by the revised Wechsler Adult Intelligence Scale a few days before operation, at 2-3 weeks and 4-6 months after operation. RESULTS: There were no stroke, seizure, and hospital mortality in either group. Significant decline between baseline and early scores were seen in three subtests (digit span, arithmetic, and picture completion) for S-RCP and four (digit span, arithmetic, picture completion, and picture arrangement) for L-RCP. Significant decline between baseline and late scores were seen in one subtest (arithmetic) for S-RCP, four (digit span, arithmetic, picture completion, and picture arrangement) for L-RCP, and one (object assembly) for CABG. The mean change of scores for one late test (digit symbol) was significantly lower in S-RCP than in CABG. The mean change of scores for three early tests (digit span, vocabulary, and picture arrangement) and four late tests (information, digit span, picture completion, and picture arrangement) were significantly lower in L-RCP than in CABG. Stepwise logistic regression analysis disclosed that, after considering the other variables, significant difference in test score changes were observed between CABG and L-RCP for two early tests (picture completion and digit symbol) as well as for three late tests (digit span, similarities, and picture completion). None of test score changes showed significant difference between CABG and S-RCP. CONCLUSIONS: The neurocognitive outcome in patients undergoing RCP less than 60 min were comparable with patients undergoing CABG without circulatory arrest. Prolonged RCP of 60 min or more in patients undergoing surgery of the thoracic aorta was associated with postoperative neurocognitive impairment.     

Cognitive decline after major noncardiac operations: a preliminary prospective study

BACKGROUND: Cardiac operations frequently are complicated by postoperative cognitive decline. Less common and less studied is postoperative cognitive decline after noncardiac surgery, so we determined its incidence, severity, and possible predictors. METHODS: Twenty-nine patients who had thoracic and vascular procedures were studied. A neurocognitive test battery was administered preoperatively and 6 to 12 weeks postoperatively. A change score (preoperative minus postoperative) was calculated for each measure in each individual. Cognitive deficit (a measure of incidence) was defined as a 20% decrement in 20% or more of the completed tests. The average scores of all tests and the average decline (a measure of severity) were determined. RESULTS: The incidence of cognitive deficit was 44.8%. Overall the severity of the decline was an average of 15% decline. In the 44.8% of patients who had cognitive deficit, the severity was 24.7%. Multivariable predictors of cognitive decline were age (for incidence and severity) and years of education (for severity). CONCLUSIONS: Cognitive decline after noncardiac operations is a frequent complication of surgical procedures. The severity could preclude successful return to a preoperative lifestyle.     

Serum creatinine patterns in coronary bypass surgery patients with and without postoperative cognitive dysfunction

Renal dysfunction is common after coronary artery bypass graft (CABG) surgery. We have previously shown that CABG procedures complicated by stroke have a threefold greater peak serum creatinine level relative to uncomplicated surgery. However, postoperative creatinine patterns for procedures complicated by cognitive dysfunction are unknown. Therefore, we tested the hypothesis that postoperative cognitive dysfunction is associated with acute perioperative renal injury after CABG surgery. Data were prospectively gathered for 282 elective CABG surgery patients. Psychometric tests were performed at baseline and 6 wk after surgery. Cognitive dysfunction was defined both as a dichotomous variable (cognitive deficit [CD]) and as a continuous variable (cognitive index). Forty percent of patients had CD at 6 wk. However, the association between peak percentage change in postoperative creatinine and CD (parameter estimate = -0.41; P = 0.91) or cognitive index (parameter estimate = -1.29; P = 0.46) was not significant. These data indicate that postcardiac surgery cognitive dysfunction, unlike stroke, is not associated with major increases in postoperative renal dysfunction. IMPLICATIONS: We previously noted that patients with postcardiac surgery stroke also have greater acute renal injury than unaffected patients. However, in the same setting, we found no difference in renal injury between patients with and without cognitive dysfunction. Factors responsible for subtle postoperative cognitive dysfunction do not appear to be associated with clinically important renal effects.     

Short-term and long-term cognitive function and cerebral perfusion in off-pump and on-pump coronary artery bypass patients.

OBJECTIVE: The aim of this study was to evaluate cognitive function, as measured by serial neuropsychological testing, and cerebral perfusion, as measured by brain SPECT scanning in patients with coronary artery diseases (CAD) following off-pump and on-pump coronary artery bypass graft surgery. Besides, the relationship between cerebral blood flow, cognitive functions, surgery parameters, and cardiac function in these patients were estimated. Also, brain-protective effects of instenon were studied. METHODS: Brain SPECT and comprehensive neuropsychological testing were performed 1 day before, 10-14 days and 6 months after coronary artery bypass graft surgery (CABG). The study involved 65 patients (62 males and 3 females, mean age 55+/-2) who underwent CABG with cardiopulmonary bypass (CPB) (43 pts) and off-pump coronary revascularization (OPCAB) using the Octopus stabilization system (22 pts). In 21 cases employing CPB, for prevention of the impairments of cerebral perfusion and cognitive deficit instenon was administered. RESULTS: CABG with the use of extracorporeal circulation is complicated by short-term and long-term neurocognitive dysfunction (in 96 and 55% cases, correspondingly). Also, in the early period after CABG, in 68% patients, decrease in regional cerebral blood flow (rCBF) was found, and after 6 months brain perfusion was lower than the baseline in 55% cases. Relationship between postoperative rCBF changes and the dynamics of cognitive function was found in early period and after 6 months following CABG. CONCLUSION: The coronary revascularization on beating heart or preventive administration of instenon in CPB patients helps significantly to diminish the risk of cerebrovascular complication.     

Cognitive changes with coronary artery disease: a prospective study of coronary artery bypass graft patients and nonsurgical controls

BACKGROUND: Cognitive impairment after coronary artery bypass grafting (CABG) is well recognized, but previous investigations have been limited by lack of an appropriate control group. We compared changes in cognitive performance at 3 and 12 months after CABG with those in a control group of patients with comparable risk factors for coronary artery disease (CAD) who had not undergone surgery. METHODS: Patients undergoing CABG (n = 140) and demographically similar nonsurgical control subjects with CAD (n = 92) completed baseline neuropsychological assessment and were followed prospectively at 3 and 12 months. Cognitive function was evaluated with a battery of neuropsychological tests assessing the cognitive domains of attention, language, verbal and visual memory, visuoconstruction, executive function, and psychomotor and motor speed. RESULTS: The CABG patients who were tested in their hospital rooms before surgery had lower scores for timed tests; however, after adjustment for demographic variables and testing location there were no statistically significant differences between the CABG and nonsurgical control subjects in baseline neuropsychological test performance. Both groups improved from baseline to 3 months; the only statistically significant group difference was a greater improvement in the CABG group with regard to verbal memory. At 12 months there were no statistically significant differences between the two groups. CONCLUSIONS: The prospective longitudinal neuropsychological performance of patients with CABG did not differ from that of comparable nonsurgical control subjects with CAD at 3 months or 1 year after base line examination. This suggests that the previously reported cognitive decline during the early postoperative period after CABG is transient and reversible. Continued follow-up will determine whether a specific "late decline" occurs in CABG patients but not in nonsurgical control subjects with similar risk factors for cardiovascular and cerebrovascular disease.     

Aortic atheroma burden and cognitive dysfunction after coronary artery bypass graft surgery

Background

Neurocognitive dysfunction (NCD) after coronary artery bypass graft (CABG) surgery is a common problem. Atherosclerotic disease of the aorta is a known risk factor for stroke after cardiac surgery, but its relationship to NCD is unclear. This study investigates the relationship between aortic atherosclerotic disease and NCD after CABG.

Patients and Methods

Patients undergoing primary elective CABG were enrolled in an ongoing investigation of NCD after CABG. Intraoperative transesophageal echocardiography (TEE) of the thoracic aorta was performed and analyzed off-line to quantify atheroma burden. Neurocognitive evaluation was performed, both preoperatively and at 6 weeks after surgery. Multivariable linear regression (controlling for age, years of education, and base line cognitive index) was used to determine the relationship between NCD and atheroma burden in the ascending, arch, and descending aorta.

Results

One hundred sixty-two patients who had a complete neurocognitive evaluation and adequate TEE images were studied. No significant relationship was found between NCD and atheroma burden in the ascending (p = 0.22), arch (p = 0.89) or descending aorta (p = 0.64).

Conclusions

Although the etiology of NCD is likely multifactorial, our results suggest that aortic atherosclerosis may not be the primary factor in the pathogenesis of post-CABG cognitive changes.     

Neurocognitive impairment and driving performance after coronary artery bypass surgery.

OBJECTIVE: Neurocognitive impairment is common after cardiac surgery but few studies have examined the relationship between postoperative neuropsychological test performance and everyday behavior. The influence of postoperative cognitive impairment on car driving has previously not been investigated. The purpose of this study was to evaluate neurocognitive function and driving performance after coronary artery bypass grafting (CABG). METHODS: Twenty-seven patients who underwent coronary artery bypass grafting with standard cardiopulmonary bypass technique and 20 patients scheduled for percutaneous coronary intervention (PCI) under local anesthesia (control group) were enrolled in this prospective study conducted from April 1999 to September 2000. Complete data were obtained in 23 and 19 patients, respectively. The patients underwent neuropsychological examination with a test battery including 12 tests, a standardized on-road driving test and a test in an advanced driving simulator before and 4-6 weeks after intervention. RESULTS: More patients in the coronary artery bypass grafting group (n=11, 48%) than in the percutaneous coronary intervention group (n=2, 10%) showed a cognitive decline after intervention (P=0.01). In the on-road driving test, patients who underwent coronary artery bypass grafting deteriorated after surgery in the cognitive demanding parts like traffic behavior (P=0.01) and attention (P=0.04). Patients who underwent percutaneous intervention deteriorated in maneuvering of the vehicle (P=0.04). No deterioration was detected in the simulator in any of the groups after intervention. Patients with a cognitive decline after intervention also tended to drop in the on-road driving scores to a larger extent than did patients without a cognitive decline. CONCLUSION: This study indicates that cognitive functions important for safe driving may be influenced after cardiac surgery.     

Smoking Is Not a Predictor of Mortality and Morbidity Following Coronary Artery Bypass Grafting

A bstract Background: The objective of this study was to determine the significant differences in preoperative and operative characteristics, and postoperative outcomes in patients having coronary artery bypass grafting (CABG) who are smokers and in those who are not smokers. Methods : Data were collected prospectively in all (2916) patients having their first CABG. The patients were cared for in a regional medical center by private physicians. No operations were denied because of smoking status. Smokers differed from nonsmokers in several characteristics. Results : Analysis of morbidity and mortality showed no instance in which smokers fared worse than nonsmokers. Stepwise logistic regression analysis showed that smoking was not predictive of mortality. Smoking was not predictive of morbidity except that it was predictive of less probability of need for intra-aortic balloon pump (7.5% in non-smokers and 4.7% in smokers). We then created groups of smokers and nonsmokers that were individually matched for age and sex. Analysis of the matched groups of smokers and nonsmokers showed that there was no significant difference in the incidence or magnitude of preoperative and operative factors except that recent myocardial infarction was more common in smokers. Nonsmokers had greater weight, body mass index (obesity), and ejection fraction. There was no difference in smokers and nonsmokers in mortality or morbidity at the 99% confidence level. Conclusion : We conclude that there is no need to delay CABG for the patients who are smokers.     

Short-term and long-term neurocognitive outcome in on-pump versus off-pump CABG.

OBJECTIVE: Neuropsychological dysfunctions are considered to be important complications of coronary artery bypass graft surgery (CABG). We examined the frequency of neuropsychological abnormalities occurring in patients undergoing CABG with (on-pump) and without (off-pump) cardiopulmonary bypass. METHODS: Neuropsychological assessment with seven cognitive tasks was performed one day before, 6-7 days after (n=49) and 6 months after (n=35) surgery. The subgroup undergoing on-pump surgery (n=30 at 7 days and n=22 at 6 months) was demographically comparable to the off-pump subgroup. The on-pump group included more multiple vessel disease. RESULTS: Repeated measures multivariate analysis of variance (using surgical group as a between-subjects factor) on the group data revealed no significant differences neither immediately after surgery nor at 6 months after surgery, compared with the preoperative performance. There were no significant differences between the on-pump and off-pump groups in post-operative neuropsychological performance soon after surgery. A significant difference was found between the two groups 6 months after surgery, with more favorable results for the off-pump group. Individual comparisons revealed that 59% of the patients of both groups undergoing CABG showed evidence of cognitive impairment soon after surgery. In 11% of the patients (all on-pump), the cognitive sequelae persisted at follow-up. CONCLUSION: This study showed no short-term difference between the on-pump and off-pump CABG groups. The long-term cognitive outcome revealed more favorable results for the off-pump group. Although a preference to operate multiple vessel disease with classical cardiopulmonary bypass (CPB) has to be considered, the present study shows evidence for a different pattern of early decline and late recovery of cognitive functions in patients undergoing CABG with and without CPB.     

The rewarming rate and increased peak temperature alter neurocognitive outcome after cardiac surgery.

Neurocognitive dysfunction is a common complication after cardiac surgery. We evaluated in this prospective study the effect of rewarming rate on neurocognitive outcome after hypothermic cardiopulmonary bypass (CPB). After IRB approval and informed consent, 165 coronary artery bypass graft surgery patients were studied. Patients received similar surgical and anesthetic management until rewarming from hypothermic (28 degrees -32 degrees C) CPB. Group 1 (control; n = 100) was warmed in a conventional manner (4 degrees -6 degrees C gradient between nasopharyngeal and CPB perfusate temperature) whereas Group 2 (slow rewarm; n = 65) was warmed at a slower rate, maintaining no more than 2 degrees C difference between nasopharyngeal and CPB perfusate temperature. Neurocognitive function was assessed at baseline and 6 wk after coronary artery bypass graft surgery. Univariable analysis revealed no significant differences between the Control and Slow Rewarming groups in the stroke rate. Multivariable linear regression analysis, examining treatment group, diabetes, baseline cognitive function, and cross-clamp time revealed a significant association between change in cognitive function and rate of rewarming (P = 0.05). IMPLICATIONS: Slower rewarming during cardiopulmonary bypass (CPB) was associated with better cognitive performance at 6 wk. These results suggest that a slower rewarming rate with lower peak temperatures during CPB may be an important factor in the prevention of neurocognitive decline after hypothermic CPB.     

The incidence of cognitive decline after (not) undergoing coronary artery bypass grafting: the impact of a controlled definition

BACKGROUND: After coronary artery bypass grafting (CABG), 20-30% of patients are reported to suffer from cognitive decline. Studies reporting these high incidences, however, have not included an appropriate control group. METHODS: We repeatedly administered a series of neuropsychological tests to 112 healthy middle-aged volunteers not undergoing surgery, and applied two widely used definitions of cognitive decline to their test results. In addition, we re-analysed the neuropsychological test data of 281 CABG patients with a definition of cognitive decline that takes into account the natural variability of test performance that was found in the volunteers. RESULTS: Three months after their first assessment, 14-28% of the volunteers suffered from cognitive decline according to the definitions of cognitive decline after CABG. Using the controlled definition of cognitive decline that takes the natural variability in test performance into account, we found that only 7.7% of the CABG patients suffered from cognitive decline at 3 months after their operation. CONCLUSION: These data suggest that the incidence of cognitive dysfunction after CABG has previously been greatly overestimated.     

Change in plasma glutamate concentration during cardiac surgery is a poor predictor of cognitive outcome

OBJECTIVE: To develop a simple and reliable method for quantitating plasma glutamate concentration and apply this method to monitor systemic glutamate levels during coronary artery bypass graft (CABG) surgery, a procedure associated with neurologic deficits. DESIGN: Prospective serial investigation of cardiac surgery patients. SETTING: Tertiary-care university teaching hospital. PARTICIPANTS: Patients undergoing CABG surgery (n = 33). INTERVENTIONS: Preoperative and postoperative neurologic and neurocognitive testing were done. Intraoperative blood samples for glutamate quantitation were obtained from jugular bulb and pulmonary artery catheters before, during, and after cardiopulmonary bypass. MEASUREMENTS AND MAIN RESULTS: Glutamate concentrations were determined using a reverse-phase high-pressure liquid chromatography method coupled to precolumn derivatization of the analyte with o-phthalaldehyde. The mean prebypass plasma glutamate concentration was 79.4 +/- 41.8 micromol/L. Plasma glutamate levels fluctuated during surgery with considerable degrees of temporal and quantitative interpatient variability. Neurologic and neurocognitive deficits were observed after CABG surgery. However, neither the occurrence nor the severity of cognitive decline could be predicted by the magnitude of increase in plasma glutamate concentration. CONCLUSION: Fluctuations in intraoperative systemic glutamate levels do not predict post-CABG surgery neurologic outcome.     

老年择期关节置换术患者术后谵妄的认知和功能预测因子及其后遗症

背景术后谵妄（postoperativedelirium，POD）在老年患者中很常见，且与不良预后相关。在行择期手术的患者中，POD的认知和功能性后遗症尚且未知。我们试图研究：①在老年手术患者中，敏感性神经认知测试的较低评分能否作为POD的独立风险因子；@POD能否预测手术3个月后的认知和功能下降。方法我们对年龄I〉65岁的全髋关节或全膝关节置换术患者进行了一项前瞻性队列研究。参与者接受术前的神经认知和功能测试。使用混乱评估法诊断POD。出现POD的患者组与对照组在手术后3个月接受重复的神经认知和功能测试。结果418例患者符合入选标准，有42例出现POD。各组之间在基础细微精神状态检查评分、酗酒、抑郁和语言智力等方面没有差别。POD的独立预测因子包括年龄、精神疾病史、功能状态的下降和语言记忆的下降。对于所有测试，POD患者组和匹配的对照组之／＇~-J在术前和术后3个月的变化相似。结论术前神经认知和功能状态的轻微下降可以预测POD。然而在出现POD的小群体中，没有手术后3个月出现认知和功能下降的证据。POD与术前认知功能的降低有关，但在择期手术的老年患者中，可能不存在手术后3个月有害的认知或功能后遗症。     

Effects of Extreme Hemodilution during Cardiac Surgery on Cognitive Function in the Elderly

Background: Strategies for neuroprotection including hypothermia and hemodilution have been routinely practiced since the inception of cardiopulmonary bypass. Yet postoperative neurocognitive deficits that diminish the quality of life of cardiac surgery patients are frequent. Because there is uncertainty regarding the impact of hemodilution on perioperative organ function, the authors hypothesized that extreme hemodilution during cardiac surgery would increase the frequency and severity of postoperative neurocognitive deficits.

Methods: Patients undergoing coronary artery bypass grafting surgery were randomly assigned to either moderate hemodilution (hematocrit on cardiopulmonary bypass >=27%) or profound hemodilution (hematocrit on cardiopulmonary bypass of 15-18%). Cognitive function was measured preoperatively and 6 weeks postoperatively. The effect of hemodilution on postoperative cognition was tested using multivariable modeling accounting for age, years of education, and baseline levels of cognition.

Results: After randomization of 108 patients, the trial was terminated by the Data Safety and Monitoring Board due to the significant occurrence of adverse events, which primarily involved pulmonary complications in the moderate hemodilution group. Multivariable analysis revealed an interaction between hemodilution and age wherein older patients in the profound hemodilution group experienced greater neurocognitive decline (P = 0.03).