Disordered Mental States in the Postoperative Period

Disruption of the ascending arousal system and cortical attention networks in post-stroke delirium and spatial neglect

Delirium is an acute attention and cognitive dysfunction, adversely affecting functional outcomes and mortality. As many as half of hospitalized right brain stroke survivors may develop delirium. Further, about 50% of right stroke patients experience spatial neglect, impairing safety and recovery. In this review we explore the brain mechanisms, which may explain the high incidence of delirium and spatial neglect after right-brain stroke. We suggest that brain networks for spatial attention and arousal, composed of ascending projections from the midbrain nuclei and integrating dorsal and ventral cortical and limbic components, may underlie impairments in delirium and spatial neglect. We propose that lateralized deficits in spatial neglect may arise because cortical and limbic components of these functional networks are disproportionally impaired by right-brain strokes, and that spatial neglect may lower the threshold for developing delirium. An improved understanding of the brain basis of delirium and spatial neglect could provide a critical biomarker for initiating preventive care in stroke patients at high risk of hospital morbidity and loss of independence.

Validation of a cognitive test for delirium in medical ICU patients

Patients with delirium, dementia, depression, and schizophrenia were administered a newly developed test designed to identify delirium in an intensive care unit (ICU) setting. Two alternate forms of the Cognitive Test for Delirium (CTD) were highly correlated. The delirium patients performed least well, and an optimal cutoff score derived from relative-operating characteristic analysis resulted in a sensitivity of 100% and a specificity of 95%. In a follow-up study, the Mini-Mental State Exam could not be administered to 42% of the ICU patients who completed the CTD. Early identification of delirium with the CTD may lead to timely treatment of specific etiologic conditions and a reduction in mortality and morbidity.

Postoperative delirium in the elderly

Postoperative delirium is common in the elderly in the postoperative period. It can result in increased morbidity, delayed functional recovery, and prolonged hospital stay. In surgical patients, factors such as age, alcohol abuse, low baseline cognition, severe metabolic derangement, hypoxia, hypotension, and type of surgery appear to contribute to postoperative delirium. Anesthetics, notably anticholinergic drugs and benzodiazepines, increase the risk for delirium. Despite the above recommendations, postoperative delirium in the elderly is poorly understood. Clearly, further studies are needed to determine the risk and long-term outcome of delirium in the elderly population. Research is also needed to define the effects of hypoxemia on cerebral function and whether oxygen therapy has any benefits. The geriatric-anesthesiologic intervention program of pre- and postoperative geriatric assessment, early surgery, thrombosis prophylaxis, oxygen therapy, prevention and treatment of perioperative decrease in blood pressure, and vigorous treatment of any postoperative complications showed some promise, but further definitive studies are needed.

Writing disturbances: an indicator for postoperative delirium

OBJECTIVE

To study the writing ability pre- and postoperatively in patients undergoing major surgery.

METHOD

In an open study twenty-four consecutive patients undergoing thoracotomy for pulmonary malignancy were monitored for postoperative delirium throughout their stay in the hospital. The writing ability was tested on a preoperative day and on the third day after the operation. Main outcome measures were delirium according to the DSM-III-R criteria and writing ability assessed on items such as reluctance to write and motor-, spatial-, syntactical- and spelling disorders.

RESULTS

Five patients (21%) developed delirium according to the DSM-III-R criteria. The writing of all patients with delirium was severely impaired with features like reluctance to write, motor disability and spatial disturbances. No patient without delirium developed these disturbances.

CONCLUSIONS

These results suggest that testing of writing ability may be useful in the diagnosis of delirium. The Delirium Writing Test is proposed as a diagnostic tool.

Positron-emission tomographic localization of abnormalities of brain metabolism in patients with minimal hepatic encephalopathy

Many patients with compensated cirrhosis without overt hepatic encephalopathy have deficits in visual-spatial perception, a condition we call minimal hepatic encephalopathy. Five patients with alcohol-induced cirrhosis and nine control subjects underwent positron-emission tomographic imaging of the brain with 18F-fluorodeoxyglucose. Patients also underwent neuropsychological and clinical chemistry tests. The patients had mild arterial hyperammonemia (62 +/- 13 mumol/L, range = 11 to 35 mumol/L) and other abnormalities typical of patients with cirrhosis. The patients' mean percentile scores on the digit symbol and block design subtests, from the Wechsler Adult Intelligence Scale (revised), and Purdue pegboard test were 11 +/- 7, 24 +/- 7 and 7 +/- 8 (right hand). Tests of vocabulary, memory, and new learning were normal. The technique of statistical parametric mapping was used to identify regions where cerebral 18F-fluorodeoxyglucose uptake and metabolism were abnormal. We noted significant reductions in the cingulate gyrus, a center mediating attention, target analysis and response formulation and significant increases in visual associative regions subserving motion and color perception and object orientation. We suggest that minimal hepatic encephalopathy is due to a deficit in the detection and formulation of responses to visual stimuli, a function of the cingulate, which is a part of the anterior attentional system of the brain. Increases in 18F-fluorodeoxyglucose metabolism may be compensatory. These studies show that brain regions differ in their sensitivity to the agents that cause hepatic encephalopathy and that positron-emission tomography is useful in studying the pathophysiology of this disorder.

Septic Encephalopathy

Septic encephalopathy occurs easily in many septic persons. Manifestations are largely similar to those seen in other metabolic brain diseases. It can be detected most sensitivily, but not specifically, with electroencephalography. Diagnosis is based on excluding other causes of encephalopathy, such as a central nervous system infection or exposure to drugs or toxins. The pathogenesis is unknown but is likely diverse. Its severity correlates with mortality. Early recognition of septic encephalopathy is essential becuase early: diagnosis and treatment of sepsis markedly reduces mortality.

Delayed recovery of behavior after anesthesia in rats

Early, complete recovery from general anesthesia is of importance for outpatients, in resuscitation research and in behavior testing of neonates. A model was designed to study behavior during the first week of recovery from anesthesia in rats, using two methods: spontaneous and unrestrained locomotor activity was tested and passive avoidance of electroshock was studied in a two session, one trial model. Neurologic deficit and ease of handling were also tested. After anesthesia with halothane 1-2% in N2O/O2 for 30 min, spontaneous activity was reduced, compared with unanesthetized rats, for up to at least 48 h. On day 6 post-anesthesia, locomotor activity was recovered, and, on days 4 and 5, passive avoidance was unchanged. Neurologic deficits were absent after the first hour of recovery and ease of handling was unchanged.

CONCLUSION

Halothane and nitrous oxide have prolonged effects on locomotor behavior beyond the immediate post-anesthesia recovery period, at a time when neurologic deficit testing does not reveal any abnormalities. The model is suitable for the comparison of recovery from different anesthesia techniques in rats.