Neuron loss after coronary artery bypass detected by SPECT estimation of benzodiazepine receptors.

BACKGROUND: Cerebral dysfunction is common after cardiac surgery and probably related to embolic phenomena, but the etiological mechanisms have not been elucidated. The aim of this study was to assess whether a possible neuron loss could be detected by single photon emission computer tomography (SPECT) estimation of benzodiazepine receptor density. In addition, we correlated the findings with neuropsychological test results. METHODS: We included 15 elderly patients undergoing coronary artery bypass surgery. Neuropsychological testing was performed before surgery and postoperatively at discharge from hospital and after 3 months using a neuropsychological test battery. SPECT was performed before surgery and after 3 months using the iomazenil bolus/infusion technique, and the benzodiazepine receptor density was calculated for the frontal, parietal, temporal, and occipital cortex. RESULTS: Cognitive dysfunction was found in 46.7% at discharge from hospital and in 6.7% after 3 months. A significant decrease in the estimated density of neurons was found in the frontal cortex, but no significant correlation was found between cognitive dysfunction and SPECT findings. CONCLUSIONS: Neuron loss was detectable in the frontal cortex, but the decrease did not correlate with neuropsychological test results.

Cerebral blood flow and cognitive dysfunction after coronary surgery.

BACKGROUND: Postoperative cognitive dysfunction after cardiac surgery has been attributed both to embolic events and periods with reduced cerebral perfusion. We investigated whether cognitive dysfunction after coronary surgery is associated with changes in regional cerebral blood flow (CBF) using single photon emission computed tomography. METHODS: Before surgery and at discharge, 15 coronary surgery patients were studied. Global and regional CBF were measured using a brain-dedicated single photon emission computed tomography scanner, and neuropsychological testing with seven subtests was performed. Postoperative cognitive dysfunction was defined as a Z score above 2. Normative single photon emission computed tomography data were available from 26 healthy age-matched controls. RESULTS: Preoperative global CBF was significantly lower in patients compared with controls (53.7 versus 46.1 mL/100 g/min, p = 0.006). After surgery, global CBF significantly decreased in the patient group (46.1 versus 38.6 mL/100 g/min, p = 0.0001). No significant differences were detected in regional CBF. Cognitive dysfunction was identified in 4 of the 15 patients (26.7%, 95% CI 7.8% to 55.1%). No correlation was found between the neuropsychological Z score and global or regional CBF. CONCLUSIONS: The significant decrease in CBF after coronary surgery was uniformly distributed and was not correlated to postoperative cognitive dysfunction.

Postoperative cognitive dysfunction in middle-aged patients.

BACKGROUND: Postoperative cognitive dysfunction (POCD) after noncardiac surgery is strongly associated with increasing age in elderly patients; middle-aged patients (aged 40-60 yr) may be expected to have a lower incidence, although subjective complaints are frequent. METHODS: The authors compared the changes in neuropsychological test results at 1 week and 3 months in patients aged 40-60 yr, using a battery of neuropsychological tests, with those of age-matched control subjects using Z-score analysis. They assessed risk factors and associations of POCD with measures of subjective cognitive function, depression, and activities of daily living. RESULTS: At 7 days, cognitive dysfunction as defined was present in 19.2% (confidence interval [CI], 15.7-23.1) of the patients and in 4.0% (CI, 1.6-8.0) of control subjects (P < 0.001). After 3 months, the incidence was 6.2% (CI, 4.1-8.9) in patients and 4.1% (CI, 1.7-8.4) in control subjects (not significant). POCD at 7 days was associated with supplementary epidural analgesia and reported avoidance of alcohol consumption. At 3 months, 29% of patients had subjective symptoms of POCD, and this finding was associated with depression. Early POCD was associated with reports of lower activity scores at 3 months. CONCLUSIONS: Postoperative cognitive dysfunction occurs frequently but resolves by 3 months after surgery. It may be associated with decreased activity during this period. Subjective report overestimates the incidence of POCD. Patients may be helped by recognition that the problem is genuine and reassured that it is likely to be transient.